course: leycroft rsv -...

21.04.2008

Individual Project ENGD3000, 2008

Leycroft RSV Simulation

W. Shipway P04125213 A. Lees

CONTENTS

Course:

Title:

Student:

Supervisor:

Abstract: Rotary Spin Vane separators (RSV’s) are used in Walkers Crisp Factories

throughout the UK to separate the water and potato particulate from the flow in a pipe.

The system of pipes is known as a Leycroft Turbo Air Sweep System. It has been

proposed to install this system in other locations, including India and the USA, but the

factories are not large enough to accommodate it. This paper is written to find the design

requirements of the Rotary Spin Vane separator with regards to the length of piping pre

and post-RSV.

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Title: Leycroft RSV Simulation

Student: W. Shipway

CONTENTS

1. ASSIGNMENT OUTLINE................................................................................... 1

2. AIM ....................................................................................................................... 2

3. SUMMARY OF OBJECTIVES. .......................................................................... 2

4. CHALLENGES .................................................................................................... 2

5. RESEARCH .......................................................................................................... 9

5.1 – Walkers Crisp Factory ..................................................................................... 9

5.2 – Fluid Dynamics................................................................................................. 10

5.2.1 – Fluid Dynamics – Fluid Flow ........................................................... 12

5.2.2 – Fluid Dynamics – Flow Through a Bend........................................... 14

5.3 – Air Conditioning .............................................................................................. 14

5.4 – RSV Operation ................................................................................................. 15

5.5 – Applications ..................................................................................................... 15

5.5.1 – Food Industry .................................................................................... 15

5.5.2 – Oil Industry ....................................................................................... 16

5.5.3 – Space Industry ................................................................................... 16

5.5.4 – Other Applications ............................................................................ 17

5.6 – Manufacturers ............................................................................................ 17

6. DESIGN CHANGES ............................................................................................ 18

7. ENGINEERING DRAWINGS ............................................................................. 18

8. RSV BODY .......................................................................................................... 19

9. FAN MODEL ....................................................................................................... 21

10. PROCEDURE ..................................................................................................... 25

11. MEASUREMENTS ............................................................................................ 25

12. DISCREPANCIES BETWEEN THE SYSTEMS .............................................. 26

13. RESULTS ........................................................................................................... 26

14. INTERPRETATION ...........................................................................................32

15. HYPOTHESIS .................................................................................................... 33

16. SUMMARY OF HYPOTHESIS ........................................................................ 34

16.1 – Test 2 Variables ............................................................................................. 36

17. TEST 2 ................................................................................................................ 37

17.1 – Parameters ................................................................................................ 37

17.2 – Process and Results................................................................................... 38

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18. DISCUSSIONS ................................................................................................... 43

18.1 – Potential Errors ........................................................................................ 43

18.2 – Test 1 ........................................................................................................ 45

18.2.1 – Limits of Post-RSV Pipe Length .................................................... 45

18.2.2 – Liquid Flow Pattern ........................................................................ 45

18.2.3 – RSV Frictional Coefficient ............................................................. 46

18.2.4 – Centrifugal Impingement ................................................................ 47

18.2.5 – Introducing a Bend in the Pipe Work ............................................. 47

18.2.6 – Decreasing of Increasing the Pressure ............................................ 48

18.3 – Test 2 ........................................................................................................ 49

18.3.1 – Stream of Water .............................................................................. 50

18.3.2 – Vertical RSV’s and the Inlet Pipe ................................................... 51

18.3.3 – Rotational (Radial) Flow Inside the Pipe ........................................ 51

18.4 – Boundary Layer and Surface Finish ........................................................ 52

18.5 – Applications of Newtonian Fluid Flow ....................................................52

18.6 – Further Testing ......................................................................................... 53

19. CONCLUSIONS ................................................................................................ 53

20. NONCLEMATURE ........................................................................................... 56

21. REFERENCES ................................................................................................... 57

22. APPENDIX ......................................................................................................... 58

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1. ASSIGNMENT OUTLINE

As part of the Walkers crisp process raw potato chips are cleansed and then water

particulate is removed from the chips by a suction process, before the chips are fried.

The reason for this removal of water pre-frying is to reduce the moisture content of the

potato chips and hence lower the gas consumption of the fryer when cooking the crisps.

The system used to remove the moisture (named the Leycroft Turbo Air Sweep System)

is shown in Figure 1. There are two systems, one passing above the chip conveyor belt,

and the other passing below the belt. The system under investigation passes below the

belt, and is located at the Leicester Walkers Crisp Factory.

More specific to the project, once the water droplets are removed from the potatoes it is

transported through the pipe work into the atmosphere through a funnel exiting the

building on the roof. At the exit point on the roof there should only be air in the pipe

work system. To remove the moisture exit before it enters the atmosphere a Rotary Spin

Vane Separator (RSV) has been introduced to the system, approximately half way along

the pipe work, in-line. The RSV separates the water and chip particulate from the air,

and only lets air continue the route to the exit. The particulate is trapped in the RSV and

removed through a drain pipe, settling in a catch box.

The problem with the current Leycroft Turbo Air Sweep system is that it is too

large in length to be implemented in other factories, and as such design changes

must be made to the pipe work to allow installation. It is investigated here whether

any changes made to the system affect the functionality of the RSV.

The manufacturer (PepsiCo) would like to know whether vertical ductwork can join at a

90 degree angle to the separator ductwork. This, along with varying pipe work lengths

pre and post separator will be subject to investigation by experimental process.

The current system shows that there is no debris (no potato chips or water) exiting at the

roof, and as such there should be no debris after any design changes have been

implemented. It is presumed, although not stated, that the reason for no water/potato

debris exiting at the roof is due to environmental regulations.

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2. AIM

The aim of the project is to investigate how to separate liquid and solid particulate from

an air stream (3-phase flow). A Rotary Spin Vane separator (RSV) is designed for such

a task, and hence exclusively this paper will investigate the parameter of the RSV and

how they affect the flow pre and post-RSV. These are considered with the overall aim

of decreasing the length of the Leycroft Turbo Air Sweep System installed at Walkers

Crisp Factory.

3. SUMMARY OF OBJECTIVES

To achieve the aim the objective are outlined in chronological order: -

1) Research fluid dynamics and any related principles that may apply.

2) Research RSV’s and their operation, the manufacturers, and their

applications.

3) Produce a physical model of the Walkers RSV and Leycroft System of

ducting.

4) Test the model to the same parameters of the Leycroft System, and test the

proposed design changes (to the length of the ducting).

5) Examine the results and extract applicable information to the operation of

the RSV.

4. CHALLENGES

The project is not designed to challenge any fundamental laws, and as such any

theoretical investigations will be considered purely academic, and as a possible source

of improvement to the current system. Any such hypothetical improvements will be

empirically validated.

Therefore the logical approach to investigating the effects of changing the pipe work is

to build an accurate model of the current system, and test this model by simulating the

actual system. Then, by changing the pipe work the effects can be observed and

proposed onto the real system.

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The pipe-work system (shown in Figure 1) will been re-scaled for modelling purposes,

and the pipe would need to be out-sourced. For this reason all proportions are subject to

this size (namely the diameter of the pipe). The overall system will be scaled down and

a one off prototype will be manufactured.

The project plan is outlined in Figure 3, the Gantt chart. The main task involved is

physically modelling the separator, and applying it to an external fan. Appropriate pipe

lengths will be installed in-line with the RSV and the fluid/solid flow (3-phase,

consisting of air/water/potato) will be observed. Then appropriate design changes will

be applied to the model and the experiment will be repeated and observed with

reference to the base results found in the first experiment.

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Figure 1. Overview of the Turbo Air Sweep System (Leycroft System). Note the system is either situated above or below the chip transport belt, not both.

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WEEK: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

OBJECTIVES

submit project outline

submit interim report

submit 2 copies of final report

oral presentation

1 outline project

2 initial research

2.1 Rresearch RSV and fluids

3 build a model

3.1 source materials

3.2 order materials

3.3 scale down drawings

3.4 model fan

3.6 produce RSV body

3.6 check scale

3.7 assemble

4 test

4.1 check data for parameters

4.2 outline testing variables

4.3 outline testing procedure

4.4 test model

5 evaluate results

5.1 interpret results

5.2 form conclusions of results

5.3 conclusions/correlations

6 (Potential) re-test

6.1 outline new investigation

6.2 outline new procedure

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6.3 re-test model

7 evaluate results

7.1 interpret results

7.2 form conclusions of results

7.3 conclusions/correlations

8 theoretical interpretation

8.1 produce a CAD model

8.2 apply CFD to model

8.3 compare results/evidence

9 formulate correlation

9.1 verify concludions

10 write report

Figure 3. Gantt Chart

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P&ID Reference

Point

Pipe Work Internal

Diameter in mm CSA in m 2 Air Flow at

Reference Point in

m3/min

Air Speed at

Reference Point in

m/sec

1 150 0.017679 28.32 26.69

2 200 0.031429 56.63 30.03

3 200 0.031429 56.63 30.03

4 250 0.049107 56.63 19.22

5 250 0.049107 113.26 38.44

6 600 0.282857 113.26 6.67

7 600 0.282857 113.26 6.67

8 350 0.096250 113.26 19.61

9 300 0.070714 113.26 26.69

System Pipework Air Speeds @ Nominal Air Flow Specification of 113.26 m3/min (4000 CFM)

V

9

Title: Leycroft L2 Turbo Air Sweeps P&ID Diagram

Sheet: 2 of 2

Drawn: Mark Timmins

Date: 9 July 2007

Version: A

Item Length in mm Diameter in mm CSA in m 2

Hole N/A 3.0 0.000007071428571

Slot 46.0 3.0 0.000138000000000

Total Slot CSA 0.000145071428571

No. of Slots per Plenum 115

Total Plenum (x1) CSA in m2 0.016683214

No. of Plenums 2


Air flow rate in m3/min though each plenum slot 0.49

Air speed in m/sec through each Plenum Slot 56.57

System Plenum Air Speeds @ Nominal Air Flow Specification of 113.26 m3/min (4000 CFM)

P&ID Reference

Point

Pipe Work Internal

Diameter in mm CSA in m 2 Air Flow at

Reference Point in

m3/min

Air Speed at

Reference Point in

m/sec

1 150 0.017679 28.32 26.69

2 200 0.031429 56.63 30.03

3 200 0.031429 56.63 30.03

4 250 0.049107 56.63 19.22

5 250 0.049107 113.26 38.44

6 600 0.282857 113.26 6.67

7 600 0.282857 113.26 6.67

8 350 0.096250 113.26 19.61

9 300 0.070714 113.26 26.69

System Pipework Air Speeds @ Nominal Air Flow Specification of 113.26 m3/min (4000 CFM)

V

99


Sheet: 2 of 2

Drawn: Mark Timmins

Date: 9 July 2007

Version: A


Sheet: 2 of 2

Drawn: Mark Timmins

Date: 9 July 2007

Version: A

Item Length in mm Diameter in mm CSA in m 2

Hole N/A 3.0 0.000007071428571

Slot 46.0 3.0 0.000138000000000

Total Slot CSA 0.000145071428571

No. of Slots per Plenum 115


No. of Plenums 2


Air flow rate in m3/min though each plenum slot 0.49

Air speed in m/sec through each Plenum Slot 56.57

System Plenum Air Speeds @ Nominal Air Flow Specification of 113.26 m3/min (4000 CFM)

Figure 4. Air speed and air flow rate at different sections of the Leycroft system.

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To build the model schematic drawings of the RSV have been provided by PepsiCo,

shown in Figure 2. These drawings will be used to produce a scale model of the RSV.

The static fan also needs to be prototyped, and it has been suggested that rapid

prototyping by Stereo-Lithography would be appropriate. Therefore the fan design

needs to be modelled with CAD, using Pro-Engineer. The fan design will be drawn for

scaling and modelling purposes.

Note: “static” in this interpretation means the rotors do not rotate, rather there is a

velocity forced upon the rotors from the main turbine (see Figure 1).

Once the drawings have been manufactured the model system needs to be assembled,

with the location constrained to the availability of a main turbine. This will therefore be

assembled at the university laboratories in Queens building, Leicester university. The

experiments on the model will be carried out as described in Section 10 - Procedure.

5. RESEARCH

5.1 – Walkers Crisp Factory

The Walkers Crisp Factory under investigation is located in Leicester, address: -

Walkers Snack Foods

Bursom Road

Leicester

LE4 1BS

The Factory is one of many located across the UK. The process of making crisps (with

relevance to this paper) is outlined below.

3 4

5

6

8

1 2

7

Figure 5. The relevant process of making the crisp, with steps numbered 1 to 8.

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The process is: -

1. Cut potato chips are moved along a belt (green arrow).

2. The belt moves through water to clean the chips (green arrow).

3. The chips fall off the belt into the fryer (green arrow).

4. Water and potato particulate are sucked off the potato chips as they move

towards the fryer. The plenums are located at point 4 (blue-grey arrow).

5. The 3-phase flow passes into the Rotary Spin Vane Separator (RSV).

6. Clean air only (single phase) exits the RSV (blue arrow).

7. The suction is caused by the fan located at point 7.

8. Clean air exits the system at the roof.

The RSV in situ is shown in Figure 6 below.

Figure 6. The RSV at Leicester’s Walkers Factory.

5.2 – Fluid Dynamics

The RSV basic principles operate on a combination of fluid (multi-phase) travelling

through a vessel of pressure P, and at velocity V. At some point along the vessel a

device is used to remove one or more of the phases. Therefore fluid mechanics should

apply to this operation. The pressure and velocity at any stage of the system is

proportional (in a linear fashion) to each other, as per Newtonian physics (known as the

ideal gas law, PV = mRT, where R is a physical gas constant, equivalent to Boltzmann’s

constant).

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5.2.1 – Fluid Dynamics – Fluid Flow

The flow of a fluid with constant density can be described using Bernoulli’s equation,

which states

ghPV

2

2

= constant

where V = velocity

g = gravitational constant

h = height of the fluid flow above ground level

P = pressure

ρ = density of the fluid

Considering that the equation is constant for a section of fluid flow, it can now used to

suggest what will happen when a change to the pipe is introduced, as is shown in Figure

7.

UNAVAILIBLE

Figure 7. A pipe with varying diameter and height

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Bernoilli’s equation can be stated for a variation of any of the variables, including

gravity if the height were large enough, and so it takes the form,

22

2

21

1

2

1

22gh

PVgh

PV

The above statements are only generalisations, and can be applied to predict the

approximate flow on application. The assumptions made in the above statements is that

the fluid is incompressible (constant density, ρ), the flow type is steady (as opposed to

turbulent flow), and the fluid is frictionless. But, of course friction does occur in fluid

flow, which brings us nicely to the next research subject.

Whenever a fluid passes over a stationary object the fluid that touches the object

experiences high shear stress, due to the fluid “sticking” to the surface. This point of

high shear stress creates a layer of fluid, where the fluid has low velocity. This is layer

of high shear due to friction is called the boundary layer, and can be diagrammatically

represented as in Figure 8 and 9.

UNAVAILIBLE

Figure 8. A slab of fluid moving over a solid object

For a pipe this can be reversed, as shown

UNAVAILIBLE

Figure 9. A slab of fluid moving through a pipe. The fluid is decelerated due to friction

on the wall.

Ref: [13] to [15]

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5.4 – RSV Operation

The operation of an RSV (Rotary Spin Vane separator) is designed to separate

contaminants from a gas flow. The gas and contaminants must be contained within a

closed system, usually consisting of duct-work (referred to above as a vessel). Certain

separators deal with the process of separation through what is known as gravity

segregation, with the heaviest fluid sinking to the bottom of the vessel through

gravitational force. These types of separators are not discussed in this paper (it is

outside of the scope).

It is known that as the multi-phase flow enters RSV the fan sends it off in a trajectory

towards the separator wall. The liquid droplets then drain off the wall, with the gas flow

continuing through and past the RSV. In this way there may be many phases in the

flow, and limitations to the quantity of the phases with regards to the RSV’s ability to

separate them.

As previously stated there is no direct references found relevant to phase separation, and

as such the principles behind the operation cannot be disclosed here. However, as

previously stated this paper is not intended to challenge or validate any fundamental

laws.

Ref: [22] to [24]

5.5 - Applications

The main applications for the RSV are listed below: -

5.5.1 - Food industry

The application of RSV technology in the food industry is due to the necessity to clean

the food before it is processed and packaged. Due to the relative importance of hygiene

in the food industry it is necessary to remove contaminants from a system, as in all

instances these contaminants (water/other cleaning liquid, or solid particulate) will

contain bacteria. Also it is sometimes necessary to remove a discharge of droplets in

chimney fitting, before it enters the atmosphere. This is of course the application that

this paper is based on.

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It is also noted that the use of separators in the food processing industry can be applied

to remove liquids from solids, such as the wine, beer and milk industry. Although the

direct application of RSV’s does not apply, the main process of directing liquids into a

wall applies. By spinning a barrel containing the liquid and solid, the liquid is separated

by centrifugal forces. The machine is commonly known as a mist separator, or

centrifugal separator. However, separators of this nature will not work on solid removal,

as it either lets the solids pass through, or disrupts the machine.

Ref: [25] to [27]

5.5.2 - Oil industry

In all instances in the oil industry oil is removed from the ground. Whether the oil is

located deep in the ground on terra firma or underneath the sea is not of consequence

with regards to the application of RSV technology. The oil erected from the ground is

never pure, and always contains both water and solid particulate (earth). Indeed a well

stream is often used to procure the oil from its location, and as such liquid is purposely

imposed on the oil. Therefore RSV’s are applied due to a need to separate the oil from

the water and gas. This is due to the necessity to use pure oil in all it applications, e.g.

for burning or lubrication. Also it is necessary to separate it to protect downstream

equipment like compressors.

The process of separating the oil is done in multiple stages, firstly from gravity

segregation (as previously touched on), then from a vane separator, then to remove the

remaining liquid (typically less then 2%) from the gas, a gas scrubber is used. The

latter, gas scrubbing, is a process of gases coming into intense contact with a liquid to

remove the remaining small volume of liquid. As such it is not further investigated, as

the process is different.

Ref [28] to [32]

5.5.3 - Space industry

A phase separator is used in the space industry for life support, thermal management

and power conversion. All air in space stations/shuttles is man made (i.e. through water

electrolysis and from storage tanks), and as such it is important to separate the gas from

liquid in an efficient manner. However, due to the lack of gravity in space the process is

slightly different, and this is referred to later in the paper.

Ref: [33] to [35]

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5.5.4 – Other Applications

Other than the above described processes, it is obvious from these descriptions above

that RSV technology is applicable to any industry where contaminants may prove

detrimental to the industry’s process. This is usually considerate to specific equipment

in the industry, such as sensitive equipment, or highly contaminant fluid in the relative

atmosphere, which may corrode the equipment. As such the application is used to

protect the equipment. Such British Standards apply to the safety of machinery by

evaluation of the efficiency of the removal of air borne hazardous substances. This is

outlined in BS EN 1903, but applies mostly to air-conditioners.

As stated in the Food Industry the operation of separation can be achieved by spinning a

barrel. This also applies to the waste industry, and the pharmaceutical industry.

They can also be used to recapture valuable liquids (such as solvents), although in most

instances gas scrubbers are the preferred method.

It is of course debatable as to which industry is the main user of separators. It is likely

that the food industry is the main user; however, the main economic profit would lie

within the oil and space industry. It is of relevance to note that the oil industry as a

whole represents the largest £ value industry.

Ref: [36] to [40]

5.6 – Manufacturers

The main manufacturers of vane separators are listed below,

Munters, UK – for use in the process industry – www.munters.co.uk

Mikropor, Istanbul – Air, gas and liquid purification -

www.mikroporamerica.com/

However, it seems that the majority of separators consist of either knock out drum

types, where they remove free liquid from gas streams, and the phase flow passes

through a meshing pad; gas scrubbers, where the flow comes into intense contact with

liquid; and finally gravity segregation, which has previously been discussed.

Ref: [41]

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6. DESIGN CHANGES

The proposed design changes made by PepsiCo involve using a 90 degree bend pre

separator and variable lengths of pipe-work pre and post separator. These are the

experimental variables, along with different air-flow velocities.

If during the experiment it becomes clear there are uncertainties in particular areas, or it

is appropriate to test another variable, then these will be tested and justified.

7. ENGINEERING DRAWINGS

The pipe work has been outsourced from the following manufacturer -

www.pipecenter.co.uk. This has a diameter of 100mm, 3mm, made from Acetyl

material. This provides adequate strength in case the velocity and pressure change cause

appreciable stress on the walls and could potentially buckle the pipe.

Drawings D001 to D003 are shown at the end of this paper, and are used to manufacture

the model. Drawing D001-1 has been scaled to 1:100/616. This is because the outside

diameter of the pipe work in the actual system is 616mm, and the out-sourced pipe work

has an outside diameter of 100mm, with 3mm thickness.

Drawing D001-2 and D001-3 has been scaled to 1:90/610. This is because as explained

a shell needed to be created around the fan of 2mm thickness. The fan needs to be

placed inside the pipe. The internal diameter of the actual pipe is 610mm, and the inside

of the model pipe is 94mm (100mm external diameter of 3mm thickness). With the shell

having an external diameter of 94mm to mate to the pipe, it leaves the blades (D001-3)

and diverter (D001-2) of external diameter 94mm – 2mm – 2mm = 90mm.

Drawing D002 shows the Leycroft system; with scaled dimensions to enable the model

to be assembled at the correct proportions.

Drawing D003 shows the proposed design changes, as outlined in section 6.

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8. RSV BODY

The main body of the RSV, as designed in drawing D001-1, will be manufactured by

vacuum forming. This is the best manufacturing technique, as it wastes little material.

Techniques like injection moulding are not available, due to costs and machine

availability. The costing would not be justified, and the time to manufacturer would not

be adequate for the project. The other technique possible would be turning; however

this would waste a lot of material. Hence vacuum forming has been employed. This was

done by turning a piece of low cost material (subject to its heat resistance) into half of

the RSV body. This mould was then placed in a vacuum forming machine, and a sheet

of plastic was heated above it. The plastic was then lowered onto the turned mould, and

negative pressure was forced inside the area between the mould and plastic. This causes

the plastic to form over the mould.

The plastic was then bolted to a CNC machine, where an outline was modelled in Pro

Engineer, and an appropriate file was created to cut out the waste material. Holes were

also added for the other half. This is shown in Figures 10 to 12. The two halves were

then loosely bolted together, slotted over the piping, and tightened.

Figure 10. The CNC machine, with the model bolted down inside.

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Figure 11. The model after the waste material has been cut.

Figure 12. One half of the final RSV body.

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9. FAN MODEL

The fan will be manufactured using a rapid prototyping technique, stereo-lithography.

This uses a vat of resin and a laser to solidify the liquid resin. A moveable bed drops

down by a certain amount and the laser then solidifies the next “plane”. Due to the

brittleness of the resin the manufacturer of the fan was consulted on the production of

the fan. It was proposed that it would be possible to make, but an accurate scale of the

thickness of the blades would not be possible. Also the blades would be vulnerable due

to their length. It was suggested that a shell was placed around the whole component to

give structural rigidity. The thickness of the shell and blades was suggested to be 2mm.

The fan was modelled as shown below in Figure 13, and then an .stl file was sent to the

Innovation Centre at DeMontfort University, where the model was manufactured. It

takes approximately 12 hours to manufacture, and photos are shown in Figures 16 and

17.

Figure 13. The fan modelled in Pro Engineer, for rapid prototyping.

Some concern was raised as to the dimensions of the blades. Figure 2 shows the original

blade and diverter (the section in the middle). But, when this was modelled in Pro

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Engineer it did not seem to fit correctly. This was raised with PepsiCo, and as such they

provided us with a revised drawing of the blades. This is shown in Figure 14. However

this schematic also proved to be inadequate. Hence the overall model of the Leycroft

System was assembled in Pro Engineer, to the dimensions of the drawings D001 to

D003 (see section 7 – Engineering Drawings). The fan component was then added to

the assembly in Pro Engineer and re-modelled so that it fits. This component was then

sent to the Rapid Prototyping Centre as a .stl file.

Figure 14. The revised blade design, provided by PepsiCo.

Figure 15. The overall assembly of the test rig, as modelled in Pro Engineer.

It is also appropriate to model this assembly in case any Computational Fluid Dynamics

can be applied. This model also provides a visual representation of the system in 3D. As

such it can be used to analyse any potential problems with the assembly, however, none

came up.

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Figure 16. The fan, .stl file (top left), structure stability (top right), and the model.

These pictures above are of the finished static fan, and complement the photos of the

stereo-lithography machine. The picture top left shows the digital model, from which

the laser takes its co-ordinates from, and the highlighted red sections are added for

structural rigidity. These are broken away when the component has been baked and is

solid, of which one segment is shown top right.

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Figure 17. The resin bath, which the fan is made in

One such parameter of the RSV is the interaction between the potato

particulate/air/water and the blades. It is necessary to ensure the model was of a similar

surface finish to the actual fan. The fan is made by welding cut to shape sheets of steel,

as is needed in the food industry, and is shown in Figure 18 below. An appropriately

smooth material is needed for the model, to simulate the steel. But, the rapid

prototyping technique for manufacturing the fan is primarily used for high geometrical

accuracy and good surface finish, and hence is appropriate.

Figure 18. a section of the fan, showing the blades.

Ref: [42] to [44]

Resin bath

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12. DISCREPANCIES BETWEEN THE SYSTEMS

1. The drawings provided by PepsiCo (Figures 1 and 2) show inconsistencies with the

location of the fan in the RSV, and the orientation of the RSV. In Figure 1 the fan in the

RSV is shown to be after the main body of the RSV (i.e. closer to the main turbine).

This would cause the RSV to not function properly, as the 3-phase flow would pass

through the RSV body before hitting the fan.

2. The position of the fan blades is inconsistent with convention. Convention states the

fan blade should be angled behind the diverter. That is, the blades should sweep back

from the centre, but the fan situated at the Leicester Factory protrudes in the opposite

direction to the 3-phase flow. This however will be researched to ensure that the logic

here is correct.

13. RESULTS - TEST 1

The velocity of air flow is quoted as 6.7m/s at the inlet of the RSV; see Appendix -

Turbo Air Sweeps Modelling URS Version 0.2, page 11, at P&ID reference point 6. A

smoke machine was obtained to run the test (taken from a aero-dynamics test rig.),

which was placed in front of the system, and allowed to warm up for 15 minutes.

Test 1.1: Initial Test – Base results – 03/01/2008

Velocity at input, V = 6.7 m/s

Pipe Length pre-RSV, L1 = 0.36 m

Pipe Length post-RSV, L2 = 0.95 m (see drawing D002)

This test involved using a smoke machine to observe the flow through the pipe work. It

proved unsuccessful due to the colour and density of the smoke making it hard to

observe accurately. Consequently minute adjustments were made to try and improve the

visibility of the flow. Eventually it was conceived that we needed to apply the smoke

stream over a single blade. This proved successful by the fact that a vortex stream was

observed to flow through the separator, although any similarities to the actual system

were reduced at each adjustment (the flow placement at the inlet, the velocities, and

density of flow).

Outcome: UNSUCCESSFUL – unable to observe

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Figure 19. A smoke machine has been put in front of the input opening, to visualise the

fluid flow. But, as stated in Test 1.1 it was not successful, as it was not possible to

observe the flow accurately. It was also inaccurate by the fact it was just one phase (air).

It was previously stated that the 2 potential ways to model the 3 phase flow included

using a smoke machine and to use a sprayer to physically inject water into the system.

Due to the former being inadequate for testing purposes (as described in test 1.1) a

water sprayer was used to simulate a 2-phase flow. The sprayer was filled with water,

and dye was added to help observe the dynamics of the water droplets.

Test 1.2: Initial Test Attempt 2 – Base results – 10/01/2008

Velocity at input, V = 6.7 m/s

Pipe Length pre-RSV, L1 = 0.36 m

Pipe Length post-RSV, L2 = 0.95 m (see drawing D002)

This test involved using a pressurised water sprayer to force feed a 2-phase flow (air

and water droplets) at the inlet. It proved successful in both visually observing the flow,

and in simulating the actual system. There was an observed 2-phase flow before the

RSV and 1-phase (air) flow after. The saturation pre and post-RSV is unknown.

Outcome: SUCCESSFUL – Base parameters set

The test was recorded to better analyse the experiment, and images of the clip are shown

in Figures 20 to 23.

Test 1.3: Introducing a 90 degree bend at the input – 10/01/2008

V = 6.7 m/s

L1 = 0.36 m

Smoke machine

RSV body

Main Turbine Input

aperture RSV body

Fan

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was an observed 2-phase flow before the RSV and 1-phase flow after. The saturation

pre and post-RSV is unknown.

Outcome: SUCCESSFUL – decreasing the pipe length considerably had no adverse

effects on the RSV’s purpose. Please see Figure 22 and 23.

Test 1.6: Adjusting the pipe length before and after the RSV – 10/01/2008

V = 6.7 m/s

L1 = 0.19 m

L2 = 0.36 m

The pipe lengths were changed to 0.19m before and 0.36m after the RSV as shown in

Drawing D003. The water sprayer was applied at the input. The changes to the pipe

lengths gave no major change in particulate separation by the RSV. There were

observed water droplets along the pipe section after the RSV but only approximately

1% of the total quantity sprayed, and the water flow stopped approximately 150mm

after the RSV. No water entered the fan. The saturation pre and post-RSV is unknown.

Outcome: SUCCESSFUL – changing the length of the pipe work after the RSV does

affect the phase content post separator. An appropriate length needs to be applied post

separator to ensure no water reaches the fan.

It was noted in all tests that the hole in the bottom of the RSV did not operate

sufficiently. The pressure difference between inside the system and that of atmospheric

caused the water to remain in the bottom of the RSV. If left to fill too much the water

overflowed into the pipe port RSV.

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Figure 20. The initial test, using red ink dye and water. There was no water after the

RSV.

Figure 21. Introducing the pipe introduces a larger boundary layer for the flow to

decrease in velocity.

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Figure 22. For test 1.5 a 0.19m pipe was assembled pre-RSV.

Figure 23. For test 1.5 a concentrated jet of water was also applied.

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14. INTERPRETATION

Section 13 shows that none of the suggested design changes as described in Section 6

gave undesirable results. The limitations of the test were the amount of fluid the RSV

was subject to, the maximum velocity of the fan (i.e. its power output), and the amount

of variations in pipe length.

The amount of fluid used was assumed to be more than the actual system, and as such is

adequate for modelling purposes.

The maximum velocity of the fan was a restriction with regards to finding the

limitations of the RSV, but to solve the problem presented by PepsiCo it is not an issue,

as the stated velocity is 6.7m/s, as shown in Figure 4. Indeed it would be better to lower

the fan speed, as this would decrease the power consumption of the fan. This is

contradicting to knowledge given by a consultant that the optimum fan speed is 9.5m/s

(as described in Test 1.4). Also, decreasing the fan speed will increase the amount of

water left on the potato chips, and so increase gas consumption of the fryer. This

association suggests that there is a compromise and therefore a theoretical optimum fan

speed and fryer temperature (gas consumption). But the gas consumption for given chip

surface moisture content is outside of the scope of this project, and it would also require

more information from PepsiCo with regards to the fryer and chip production.

The variations in pipe length pre and post-RSV were constrained to the resources

available, as there was only a finite amount of pipe to work with.

Test 1.5 involved changing the pipe pre separator, and had no adverse effects. Test 6

involved changing the pipe pre and post separator, and although there was a minimal

amount of liquid after the separator, it was observed that some liquid did pass the RSV.

Therefore there are limitations with respect to the pipe length post-RSV. This is the

main outcome of the test. However the amount of water in the bottom of the RSV did

affect the liquid quantity post-RSV. As Test 1.6 progressed the amount of liquid

observed post-RSV increased, but at the start of the test there was only a small amount.

It is suggested that the increase is not due to a certain amount passing through the RSV

in a linear fashion (i.e. the longer the test progressed the more water passed through in a

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16. SUMMARY OF HYPOTHESIS

Referring to Section 14 and 15 the main parameters of the RSV is hypothesised to be

1. The length of the pipe work post-RSV. A limit has been suggested that 0.19 m

length post-RSV is the limit for the functionality of the RSV, but it was not

tested past this length.

2. The geometry of the fan blades. Specifically the angle and surface area in

contact with the phase flow.

3. The diametric ratio of the RSV. The diameter to length of the RSV will have a

limit to which it can no longer separate the phases.

4. The material and surface finish of the inside of the RSV. If the surface frictional

coefficient were too low then the water and some particulate would simply

follow the path of the air, and not be caught in the RSV

5. The speed of the fluid flow.

6. The insert inside the RSV, where the pipe work protrudes into the RSV slightly.

This is shown below in Figure 24. The protrusion (insert) is there to ensure no

water/particulate enters the other side of the pipe work. It does this by simple

means of physically blocking the outskirts of the pipe work.

UNAVAILIBLE

Figure 24. Detail of the section that protrudes into the RSV

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A second test is hence conducted. Of the above parameters number 3 is investigated.

This has been deduced in the following manner: -

Regarding number 1: It would be appropriate to change the length of the pipe work

post-RSV to find the limit of length before the water was sucked past the RSV into the

fan, but as previously highlighted, there is only a finite amount of pipe-work, and so this

test is not possible. The length of the pipe work has already been investigated to a good

degree as well.

Regarding number 2: It would be possible, and indeed it would likely have a

considerable amount of difference to the RSV, however the stereo lithography process

is quite expensive, and it would take too long a time to make another. The process

previously involved booking the machine some weeks in advance, making the model,

and acquiring funding for it. It was quoted by the manufacturer that the fan would cost

approximately £150.

Regarding number 4: As described later, increasing the frictional coefficient is possible,

but once this is done the model can no longer be used for such a wide variety of

experiments, as the coating would be permanent. Also, colleagues are using the system

for their own investigations, and this may be disadvantageous to their experiments.

Regarding number 5: This has already been investigated in Test 1.

Regarding number 6: It is relatively obvious that decreasing the protrusion (as in Figure

xx above) will decrease the RSV functionality, but increasing it may provide some more

insight.

Also the main purpose of investigating the RSV is to decrease the length of the Leycroft

System. This directly does that, and the only other parameter that considers this is the

pipe work length post-RSV.

Ref: [45] to [47]

16.1 – Test 2 Variables

It is therefore proposed that changing the length of the RSV at the larger diameter

section and then running a test should provide more data and help to find out what the

limitations of the system are. In this sense it will help to find what the main design

requirements are for the RSV. To do this the RSV is cut along its diameter at one end,

to make the RSV adjustable. This is shown in Figure 26. The interface must be tight to

ensure there is no pressure drop. It is calculated geometrically as in Figure 25.

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Student: W. Shipway

UNAVAILIBLE

Figure 25. The trigonometric drawing of the RSV cut.

Figure 26. A photo of the RSV cut.

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Student: W. Shipway

which did not continue along the pipe towards the main turbine, but remained where it

was. Figure 26 shows a picture of the RSV and pipe after the RSV.

Figure 26. x = 0.14m. An insignificant amount of water was observed post-RSV.

Test 2.2: x = 0.12m – 02/04/2008

The test was conducted as in Test 1, with the fan switched on, the water sprayer was

sprayed into the inlet, with coloured water to observe the flow pre and post-RSV.

Outcome: SUCCESSFUL – the observed flow was exactly the same as in Test 2.1.

Only a small amount of water (less than 1%) was observed along the pipe post-RSV,


was. Figure 27 shows a picture of the RSV and pipe after the RSV. It was observed that

a stream of water formed in the pipe before the RSV. This is shown in Figure 28.

Figure 27. x = 0.12. Only a small amount of water (less than 1%) passed into the pipe

post-RSV.

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Figure 28 (a). x = 0.12m. A stream formed in the pipe

Figure 28 (b). x = 0.12m. A stream formed at in the pipe before the RSV

Test 2.3: x = 0.1m – 02/04/2008



Outcome: SUCCESSFUL – the observed flow was exactly the same as in Test 2.1.

Only a small amount of water (less than 1%) was observed along the pipe post-RSV,


was. Figure 29 shows a picture of the RSV and pipe after the RSV. It was observed that

there was no water in the extension section. This is highlighted in Figure 30.

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Figure 29. x = 0.1m. Only a small amount of water (less than 1%) passed into the pipe

post-RSV.

Figure 30. x = 0.1m, notice there is no water in the circled area.

Test 2.4: x = 0.08m – 02/04/2008



Outcome: SUCCESSFUL – It was observed that there was a considerable amount of

water in the pipe after the RSV. This is highlighted in Figure 31.

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18. DISCUSSIONS

Please see sections 14 - Interpretation, and 15 - Hypothesis for a discussion on test 1.

This is because the outcomes of this test dictated the variables for test 2. They are

however further discussed in section 18.2 – Test 1, and summarised in 19 -Conclusions.

18.1 - Potential Errors

The amount of fluid removed from the system is quoted as 80-100 l/min, from the

Turbo Air Sweeps Modelling URS Version 0.2, page 6. To compare the amount of

liquid Test 1 and test 2 removed from the system the water sprayer has been tested. This

was conducted by pressurising the sprayer by the same amount as was done in the test,

and spraying water into a beaker for 10 seconds. The outcome was that the sprayer

dispersed 110 ml. comparatively this is 0.66 l/min.

This gives rise to 2 concerns. Firstly, the model is to a particular scale, and as such the

flow rate needs to be multiplied by this scale factor to yield accurate comparisons.

Secondly, after conducting test 1 and 2 and observing the flow rate and quantity of

liquid, the water separation rate seems very high for the Leycroft System.

Problem 1 is tackled first. The internal diameter of the Leycroft System and the model

is 610mm and 94mm respectively (taking into account the thickness of the material, as

this is the area that the fluid flows through). The x-sectional area is then

2m 3109464

209402

A Model,

2m304

2610

4

2

1A System,Leycroft

..π

..ππd

By taking the scale factor A1/A2 the flow rate of liquid for the model is

l/min528660310946

30660

2

1Model of Rate Flow ...

..

A

A

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The high separation rate is evaluated by knowing a few parameters. The flow rate is

nominally 6.7m/s, and the quantity of liquid separated is 80 to 100 l/min. The flow of

liquid can be calculated as,

m/s

4

35

)2(m 30

/s)3(m310671

)2

(m2

610

/s)3

(m3

1060

100

area sectional-x

(l/min)100 .

.

-.

.

π

This calculation assumes that 100 litres of fluid travels through a pipe of 0.3 m2 x-

section every second. As such there are no other phases (air or particulate) present, i.e.

100% of the x-sectional area is covered by the liquid at any instant in time. This shows

that it is possible, as the actual flow rate is defined as 6.7 m/s, and hence the quantity of

air and particulate can occupy 26.4% of the x-sectional area at any one instant in time.

This is applicable to all lengths of the pipe work, assuming the fluid flow is not that of

the slug/plug type.

2 or multiple phase flow patterns can arrange themselves in a variety of configurations.

With slug flow large gas bubbles followed varyingly with slugs of liquid form the

majority of the flow pattern. Please see Figure 33 for an appreciable description. The

changes in flow pattern are a function of either gas-liquid interface, or geometry

changes.

Figure 33. Varying 2 phase flow types along a pipe [48]

The 3rd

phase flow of potato particulate was not tackled, due to limitations of the

experimental technique, i.e. it was not possible to simulate a similar flow of particulate.

However, as described in the hypothesis, having a phase flow of greater density would

only separate easier from the main flow pattern.

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18.2.3 – RSV Frictional Coefficient

After test 1 was conducted it was hypothesised that a higher frictional coefficient inside

the RSV would be beneficial to the removal of the water/particulate. This could simply

be applied as a coating inside the RSV, instead of making a new system. However it is

also suggested that it could be detrimental to the overall operation of the system. Whilst

the RSV specifically is used to remove water and potato particulate, this is superseded

by the operation of removing water from the potatoes on the belt. Having a higher

frictional coefficient at the RSV would cause the air to also lower its velocity when

entering the RSV. This may prove to be detrimental to the sucking operation at the

plenum chambers, as regardless of the pressure difference pre and post-RSV the fluid

velocity would be lower when the frictional coefficient is higher. This is a law of

classical physics. A simple analogy is that more force is required to push a brick over a

rough surface than a smooth surface.

It is not suggested that having a very smooth surface finish would also prove to be

beneficial to the RSV operation. Having what is known as “cold welding” between two

interfacing surfaces occurs when two surfaces are of such a mechanical smoothness that

they adhere to each other, and is dependant on the molecular force of the material. As

such this smoothness would not be achieved easily, and it may not provide such a high

coefficient as a rough surface.

Irrespective of the above statement, having a higher coefficient of friction will cause all

fluid flow to decrease. This may or may not prove to be detrimental to the suction

power at the plenums. It is suggested that the fluid velocity would decrease overall for a

given fan speed for a higher frictional coefficient inside the RSV, and hence would

require more power to suck the same amount of water off the potatoes. But, this

decrease in velocity may only be minimal, and not enough to be considered. As stated at

the start of this paper this hypothesis would need to be experimentally proven, and

indeed not only proven but shown to have such an effect that it should be considered

beneficial enough to the system to stop the chip manufacture whilst the coating were

applied. Indeed, the cost effectiveness should be analysed. It should be decided how

long it would take to dismantle, apply the coating, and re-assemble the RSV, which

would be offset by the increase in performance of the RSV with regards to its cost

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effectiveness. Then it would be decided whether this capital loss would be greater than

the benefits discussed. However, this is not decided here due to a few reasons. Firstly

there is not enough information with regards to the economics; secondly it is beyond the

scope. The test is not done due to the limit in time; also by applying a coating it would

not be possible to see the whole process, only the outcome post-RSV. Whilst this is

adequate for that particular experiment it would disturb the model in such a way that

any future testing would not be possible, even if it is only very small.

18.2.4 – Centrifugal Impingement

As described in section 15 – hypothesis, the operation of the RSV relies on the density

of the other phases (water/potato). The RSV turns the axial flow pattern into a radial

flow, and the liquid and solid particulate is thrown off by centrifugal forces, whilst the

air remains in this radial flow pattern. The liquid and particulate then drain off the inner

wall of the RSV. This is also validated by the fact that space applications have to pursue

different techniques to achieve this phase separation. By definition, in space the

respective weight (force) of a liquid particle travelling through a vessel of ducting will

be zero, due to the lack of gravity. As such what is known as a vortex separator is being

researched elsewhere and applied to space technology. The basic physics fundamental

to the success of this vortex separator is that a force is applied to the phase flow by use

of a vortex, creating an induced centrifugal force (simulating gravity).

18.2.5 – Introducing a Bend in the Pipe Work

A radius of curvature of approximately 300mm is used for the pipe bend in test 1.3, and

the velocity was not shown to decrease to any extent. Therefore, it is suggested that

boundary layer separation did not occur (see section 5.2.2 – Flow Through a Bend), and

hence a pipe should be used with a radius of curvature of 1.9m (by scaling up to size) in

the Leycroft System, assuming a linear relationship. It is not known if this is the limit of

the radius of curvature, as other pipe bends were not tested. If bends are applied the

velocities around these locations should be checked, and the turbine should be adjusted

accordingly. But, this gives rise to a problem. It is necessary to note that a bend can

cause turbulence due to boundary layer separation, and hence the velocity in the bend is

not uniform. It has been calculated that the laminar velocity be measured at a point

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along the pipe 12 to 14 times the diameter of the pipe [49], and must be considered

when measuring velocities at this point.

If the pipe bend radii of 1.9m, then curved guide vanes could be suggested. An example

is shown in Figure 34. Even though the boundary layer surface is increased, the losses

due to separation are greatly reduced. Further information of flow through a bend is

found in Ref. [50] and [51].

UNAVAILIBLE

Figure 34. Curved guide vanes for small bends. [52]

18.2.6 – Decreasing or Increasing the Pressure

In test 1.4 the velocity of the main turbine was increased to a maximum of 8.5m/s. As

explained in section 5 – Research, this is used to force a pressure change between one

vessel and another. But, as experimentally found an increase in pressure difference

(represented by the fan speed) had no adverse effects on the operation of the RSV. If the

pressure change were decreased (the fan speed slowed down) however, it may cause

problems. As previously described the liquid impinge onto the RSV by applying a radial

flow pattern. If the fan speed was decreased then the radial centrifugal force would

decrease, and the point of separation from the flow would also decrease. There should

consequently be a theoretical limit to the fan speed. Also, more importantly, if the fan

speed was decreased then suction of liquid from the potatoes would decrease.

There would also likely be a limit to the increase in speed of the main turbine. If the

velocity were too high it could suck the water from the RSV, particularly further away

from the fan. This problem could be solved by the application of another “static” fan.

This is shown below in Figure 35. The RSV main body would have to be increased in

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length to a certain extent, to allow sufficient room for the second fan, and allow the 2nd

flow of liquid to impinge on the wall. An example is shown below. This is not discussed

further though as there are many variables to consider, like the specific location, the

length of the blades, the orientation of the blades, the angle of the blades, introducing a

2nd

rotational flow etc...

UNAVAILIBLE

Figure 35. An RSV with 2 fans, for high flow velocity.

Ref: [53] to [58]

18.3 – Test 2

Test 2 involved changing the length of the RSV. It was found that the limit to the length

of the RSV is 0.08m. This potentially shows a limitation with regards to the length of x.

At x = 0.08m there was a considerable amount of water passing through the RSV and

into the pipe. The cause may be that the RSV no longer functions at this length, and as

such a limit has been reached. This limitation has to consider hypothesis number 3, the

diameter to length ratio (see section 16 - Summary of Hypothesis), as a smaller/larger

diameter will change the operation. The limits may be considered then for diameter to

length ratio of 2.2.

But, as stated in test 1 the drainage hole did not function properly due to the pressure

difference. This is applicable to test 2 as well, and as such it was observed that if left to

fill too much it overflowed into the pipe post-RSV. More specifically, a description of

the process at this stage is that the suction from the fan caused a turbulent formation of

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fluid (both water and air) at the bottom of the RSV. When filled to a certain amount this

turbulence causes some of the liquid to spill over into the pipe post-RSV. This amount

can be calculated as a function of the length of x, the diameter of the RSV and the time

it took to cause this turbulence. But it is not necessary as this does not occur in the

Leycroft System, i.e. there is a pump in situ of the drain that counter acts the pressure

difference. However, the variables of this function can predict that a decrease in x will

also decrease the time it takes to cause this turbulent overflow, hence it would happen

quicker the shorter x was. Indeed, it was observed to occur very quickly for x = 0.08m

and below. This may account for the observed liquid post-RSV, rather than a deficit in

the function of the RSV at x = 0.08m and below.

It was noticed in test 2.3 that there was no water at the extended part of the RSV (when

x decreased). This observation confirms that the RSV is a closed system at this point,

and that no water escapes through a gap at the interface. This ensures the tests are not

invalid due to a change in the RSV design. Also, it was noted that adjusting the length

of x whilst the fan was ON required considerably more force than with the fan OFF.

This is due to the attempted change in length increases the volume for a constant

pressure (set by the main turbine). The result of this is due to a tight fit of the RSV,

suggesting that the cut did indeed produce a close model to the original RSV, with no

decrease in pressure, and more importantly no gaps for the water escape from.

18.3.1 – Stream of Water

The observed stream of water pre-RSV suggests that the air flow does not carry 100%

of the water droplets. Some of the water that was sprayed into the pipe was carried

along to the RSV, at which point it separated in the normal manner. However, when the

stream of water made contact with the RSV fan, the quantity of water inside the RSV

dramatically increased. However, this did not change the operation of the RSV, as it

was still able to separate the phases. Absolutely, this is described to occur in the

Leycroft Turbo Air Sweeps System, see Appendix Turbo Air Sweeps Modelling URS

Version 0.2 – page 18. This describes “a continuous stream of water flowing into the

separator belly from the main ductwork – this was expected”. This stream is associated

with keeping the separator clean. For the model to also formulate this stream it

demonstrates an accurate simulation, and as such the results are more convincing.

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Figure 36. The droplets are dispersed in an angular formation.

18.4 – Boundary Layer and Surface Finish

Please refer to section 5.2.1 – Fluid Dynamics - Fluid Flow for the theory of a boundary

layer.

When the liquid comes into contact with the surface of the blades, it creates a boundary

layer of high shear stress, and will create a layer of liquid on the blades. Therefore it is

not necessary to consider the surface finish of the blades as part of the design, as the

blade will be covered with this boundary layer of liquid. However, as found by

experimentation, the liquid does not cover the inside of the RSV completely at any

instant in time, and hence the roughness of the inside should be considered. The extent

of the difference this will make is not known, and, it is also not known whether the

boundary layer will consist of only liquid or gas, or a mixture. Theoretically, if the

velocity is zero then by definition there would be no change. However, “high shear

stress” does not mean zero velocity, but “low” relative velocity. When the gas passes

over the liquid on the blades it may also affect the boundary layer.

18.5 – Applications of Newtonian Fluid Flow

It is shown that the principles of fluid dynamics do obey Newtonian Physics, and hence

could be used to predict the flow pattern and radial velocity for separation. However,

the flow pattern is not known, and would be subject to the quantity of air, water and

potato sucked in from the plenums, and is of course variable considering the

manufacturing technique. Therefore, it is not appropriate to model the RSV with

principles proposed by D. Bernoulli, Navier-Stoke, Rankine, and Reynolds, as the

θ

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practical variables are not known. As such there is no analytical correlation covering the

separation of phases in a vessel, but it was not found to be necessary for the project.

However it would have been excellent to measure the variables at the plenum and

develop an analytical technique.

Note: water and air obey Newtonian Fluid mechanics, i.e. the relationship is linear with

respect to rises in temperature and hence velocity and pressure. But the relationships of

a solid in a fluid flow are not known.

18.6 – Further Testing

To further test the system:- a) the flow rate would be increased to a proportionate value

of 2.3 l/min b) the application of a simplistic pressure drop with respect to the inside of

the pipe at the bottom of the RSV to remove the liquid would be needed, i.e. a pump.

This may validate or null test 2. c) the pipe inlet and outlet locations could be changed

to see the effects. d) the fan could be flipped so see if it makes a difference in the correct

orientation. e) smaller bend radii of pipe could be applied. f) two fans could be applied

to see if there are any effects on the operation.

19. CONCLUSIONS

The Rotary Spin Vane separator (RSV) is found to rely on the density of the

other phases (water/potato). The RSV fan turns the axial flow pattern into a

radial flow, and the liquid and solid particulate is thrown off by centrifugal

forces, whilst the air remains in this radial flow pattern. The liquid and

particulate then drain off the inner wall of the RSV.

The limit of the length of the pipe post-RSV has been experimentally found as

4m for the Leycroft System (taking into account the scale of the model). It is

hypothesised that this limit is due to the boundary layer associated with flow

through a pipe. However, the turbulent liquid at the bottom of the RSV may

have been the cause of the observed liquid.

The turbulent liquid in the bottom of the RSV was observed better in test 2. The

hole in the bottom of the RSV did not serve its purpose, as the negative pressure

21.04.2008

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Student: W. Shipway

inside the RSV with respect to atmospheric cause a vacuum in the RSV, and as

such the liquid did not exit the system until the main turbine was switched off.

If pipes with bends were introduced, it is suggested that boundary separation

(and hence velocity flow losses) will not occur for a radius of curvature of 1.9m

for the Leycroft System.

By increasing the flow velocity the separation rate of liquid would increase, as

the centrifugal force acting tangential would increase. There is a limit to this on

the operation of the RSV however, as a high velocity would cause the liquid to

be taken off the inner wall and back into the stream further along the RSV body.

As the RSV is applied horizontally in the Leycroft System the inlet pipe can be

pulled out by approximately 154mm. This would decrease the overall length of

the system, but not by much comparatively. However, the fan is orientated

incorrectly in the Leycroft System, and as such any other system would need to

take into account the fan blades being 5 degrees less than the RSV slope, with

respect to the horizontal axis. This is to ensure the liquid and particulate does not

impinge on the slope of the RSV body.

The limit of the RSV body length is found experimentally to be 0.5m for the

Leycroft System. However, this limit may be subject to the turbulent flow in the

bottom of the RSV, as aforementioned

High shear stress at the interface between the blades and fluid/solid flow will

cause a boundary layer at the surface of the fan blades, and hence the surface

finish of the blades is insensitive to the RSV operation. However, the interface

of solid particulate and gas may disrupt the boundary layer, and so this surface

of liquid may not be constant.

The surface finish of the RSV body would cause a change in the separation rate,

due to the frictional coefficient. However, it is not known whether it would be

21.04.2008

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Student: W. Shipway

detrimental to the flow velocity, and indeed whether the change would be

noticeable.

If the blade angle was to shallow (to the horizontal axis) then it would not cause

enough centrifugal force, and so the liquid and solid would not separate from the

radial flow. Conversely, if the angle were too large, it would be detrimental to

the flow velocity, as it would act as a blockage.

The diametral ratio to length of the RSV body is found to be 2.2. Associated

with the above statement, if the diameter is too small then the radial flow pattern

would not sufficiently materialise, and the liquid/solid would not separate. Also,

the liquid would more easily return to the flow. If the diameter is too large then

the separated liquid may not impinge on the wall at a great velocity and hence

may return to the flow, particularly at the top most part of the RSV inner wall.

Note: all geometry stated assumes that the flow velocity and water separation rate is

linear. It is assumed that the solid particulate would separate from the radial flow easier

than the liquid proportionately to the respective increase in density. This is in following

with Newton’s 2nd

law of Motion.

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Student: W. Shipway

20. NONCLEMATURE

Symbol Description Units Section

PL Pressure, inside the Leycroft System N.A.

5.2

PF Pressure, behind the fan N.A.

5.2

P1 Pressure, of pipe for use in Bernoulli’s equation N.A. 5.2

P2 Pressure, of pipe for use in Bernoulli’s equation N.A. 5.2

V Velocity N.A. 5.2

V1 Velocity, of pipe for use in Bernoulli’s equation N.A. 5.2

V2 Velocity, of pipe for use in Bernoulli’s equation N.A. 5.2

h1 Height, of pipe with reference to a ground level N.A. 5.2

h2 Height, of pipe with reference to a ground level N.A. 5.2

ρ Density, of fluid N.A. 5.2

A1 Area, of the Leycroft System m2

18

A2 Area, of the model m2

18

x Length, of the RSV larger diameter m 17

y Length, of the pipe inside the RSV m 17

θ Angle, of droplet formation after the RSV degrees 18

Θ Angle, of RSV body slope degrees 16

d Diameter, outside of RSV body (model) mm 16

d1 Diameter, outside of pipe (model) mm 16

a Length, of opposite side of triangle mm 16

b Length, of adjacent side of triangle mm 16

c Length, of hypotenuse of triangle mm 16

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Student: W. Shipway

21. REFERENCES

[1], [17], [52] B. S. Massey, 1989, Mechanics of Fluids, 6th

Ed., Chapman & Hall, London

[2], [48] S. W. Yuan, 1970, Foundations of Fluid Mechanics, SI Unit Edition, Prentice Hall,

London

[3], [49] R. J. Goldstein, 1983, Fluid Mechanics Measurements, Hemisphere, London

[4] J. F. Douglas, R. D. Matthews, 1986, Solving Problems in: Fluid Mechanics Volume 1, 3rd

Ed.,

Longman, Essex

[5] T. Schwenk, 1965, Sensitive Chaos, Rudolph Stiener, London

[6] S. Levy, 1999, Two Phase Flow in Complex Systems, Wiley & Sons, Chichester

[7] W. Schowalter, 1978, Mechanics of Non-Newtonian Fluids, Pergamon, Oxford

[8] A. Brebbic, J. J. Connor, 1976, Finite Element Techniques for Fluid Flow, Butterworth, London

[9] http://en.wikipedia.org/wiki/Francis_turbine, last modified 05.02.2008

[10] http://en.wikipedia.org/wiki/Pressure, last modified 03.09.2007

[11] http://en.wikipedia.org/wiki/Turbine, last modified 10.02.2008

[12] http://en.wikipedia.org/wiki/Gas_constant, last modified 05.02.2008

[13] J.A. Fay, 1994, Introduction to Fluid Mechanics, MIT Press, London

[14] M. Horsley, K. Sherwin, 1996, Thermofluids, Chapman & Hall, London

[15] http://en.wikipedia.org/wiki/Bernoulli%27s_principle#cite_ref-14, last modified 05.02.2008

[16] J. F. Douglas, J. M. Gasoirek, Fluid Mechanics, 4th

Ed., Prentice-Hall, London, 2001

[18] J. R. Watt, 1986, Evaporative Air Conditioning Handbook, 2nd

Ed., Chapman-Hall, London

[19] V. P. Lang, 1979, Basics of Air-Conditioning, 3rd

Ed., Litton Ed.

[20] W. P. Jones, 1980, Air Conditioning Applications & Design, Edward Arnold, London

[21] R. McMullan, 2007, Environmental Science in Building, 6th Ed., Palgrave, London

[22] www.munters.us/en/uk/Products - DS8000-Series, Munters AB, Sweden

[23] www.glossary.oilfield.slb.com/Display.cfm?Term=separator, Schlumberger Ltd., 2008

[24] www.glossary.oilfield.slb.com/Display.cfm?Term=two-phase%20separator, Schlumberger Ltd.,

2008

[25] www.foodprocessing-technology.com/contractors/separator/westfalia/, SPG Media Ltd., 2007

[26] www.munters.co.uk – See DS8000 series, and DV270, Munters AB, Sweden

[27] www.misteliminators.org/separators/index.html

[28] http://process- equipment.globalspec.com/LearnMore/Manufacturing_Process_Equipment

/Air_Quality/Scrubbers, GlobSpec., 2008

[29] http://en.wikipedia.org/wiki/Scrubber, last modified 10.02.2008

[30] www.lenntech.com/Air-purification/Gas-purification-techniques/Gasscrubber.htm, Lenntech,

Netherlands, 2008

[31] www.patentstorm.us/patents/7144437-description.html, PatentStorm Ltd., 2006

[32] www.rigjobs.co.uk/oil/history.shtml, Rigjobs, 2007

[33] www.macrovu.com/image/PVT/NASA/RPC/uc%3DVortex.v3.pdf

[34] www.scribd.com/doc/388135/Aerospace-systems, 2007

http://www.macrovu.com/image/PVT/NASA/RPC/uc%3DVortex.v3.pdf

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Student: W. Shipway

[35] X. deFerrán, 1991, ISO Project, ESA Directorate for Scientific Programmes, ESTEC,

Noordwijk, Netherlands

[36] www.luwa.co.uk/luwa/product%20files/Waste%20Sep.html, LUWA (UK) Ltd.,

[37] www.tetrapakprocessing.ca/download.asp?dID=147

[38] www.chemplast.co.uk/gas-liquid-separators/gas-liquid-separators.htm

[39] www.biotage.com/DynPage.aspx?id=25351

[40] http://products.ihs.com/bs-seo/gbm13_28.htm

[41] B. Kalis, 2004, We need a mist eliminator in that knockout drum! Can we add one without

overhauling the vessel?, Amistico

[42] http://en.wikipedia.org/wiki/Stereolithography, last modified 13.02.2008

[43] http://computer.howstuffworks.com/stereolith.htm, last modified 05.08.2000

[44] www.stereolithography.com/slainfo.php

[45] http://en.wikipedia.org/wiki/Stereolithography, last modified 13.02.2008

[46] http://computer.howstuffworks.com/stereolith.htm, last modified 05.08.2000

[47] www.stereolithography.com/slainfo.php

[50] H. Ito, 1959, Friction Factors for Turbulent flow in Curved Pipes, J. Basic Engng 81D

[51] H. Ito, 1960, Pressure Losses in Smooth Pipe Bends, J. Basic Engng 82D

[53] http://hyperphysics.phy-astr.gsu.edu/hbase/frict.html#rou, R Nave

[54] http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html, R Nave

[55] R. L. Childers, E. R. Jones, 1993, Contemporary College Physics, 2nd Ed, Addison-Wesley,

USA

[56] http://en.wikipedia.org/wiki/Factor_of_adhesion, last modified 03.03.2008

[57] http://en.wikipedia.org/wiki/Drag_%28physics%29, last modified 26.02.2008

[58] http://en.wikipedia.org/wiki/Coefficient_of_friction, last modified 27.02.2008

Discussions with:

Dr. Rajakaruna - Thermodynamics, contacted for applications of Fluid Dynamics

Mr A. Lees - Chartered Engineer, Mechanics and Design, Project Leader

Prof. Goman - Computational Methods for aerodynamics, contacted for applications of

CFD

22. APPENDIX

The Turbo Air Sweeps Modelling Specification is shown in the following pages.

course: leycroft rsv -...

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