fuel injector project

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Heath Headley Vu Danh Nicholas Chua Tommy Harris Ryan Fontenot DEPARTMENT OF MECHANICAL ENGINEERING UNIVERSITY OF LOUISIANA AT LAFAYETTE PROJECT ADVISOR: DR. LULIN JIANG Flow-Focusing to Flow-Blurring Fuel Injector MCHE 484 SENIOR DESIGN PROJECT APRIL 28, 2016

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Page 1: Fuel Injector Project

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Heath Headley Vu Danh Nicholas Chua Tommy Harris Ryan Fontenot

DEPARTMENT OF MECHANICAL ENGINEERING UNIVERSITY OF LOUISIANA AT LAFAYETTE PROJECT ADVISOR: DR. LULIN JIANG

Flow-Focusing to Flow-Blurring Fuel Injector MCHE 484 SENIOR DESIGN PROJECT APRIL 28, 2016

Page 2: Fuel Injector Project

Executive Summary

This project involved designing and building a fuel injector that is of the continuous flow

type, and employs the flow-blurring concept. Flow-blurring was invented by Dr. Alfonso GaΓ±Γ‘n-

Calvo. Flow-blurring involves the use of high speed air flow mixing with fuel flow to atomize

and vaporize any given fuel. This is especially useful if one were to be using an unusually high

viscosity fuel like some thick biofuels, as it would effectively vaporize them for more efficient

combustion.

The team designed and built an injector that can be adjusted to operate in both the flow-

blurring and flow-focusing regimes by adjusting the offset distance. The injector parts were 3-D

printed with ABS plastic. The model that was built performed as expected, working well in both

flow-focusing and flow-blurring regimes. Pictures were taken of the spray patterns that resulted

from various air-liquid ratios and later examined.

The approximate spray angle and air-liquid composition of the injector sprays were both

able to be analyzed visually from the photographs that were taken with a Nikon camera mounted

on a tripod. More exact analysis of spray characteristics, for example droplet size, was not possible

to determine from photographs alone. More sophisticated measuring equipment would be

necessary.

Page 3: Fuel Injector Project

Table of Contents

Introduction…………………………………………………………………..….…………....…..1

Section I: Project Constraints………………………………………………………….....…..…..3

Section II: Background Research………………………………………………………....…..….4

Section III: Design Process……………………………………………….…………………...…6

III.1 Design Criteria……………………………………………………………….…..…6

III.2 Design Evaluation Process……………………………………………………..…...7

III.3 Designs Created…………………………………………………………………......8

Section IV: Final Design Details…………………………………………………………….....16

IV.1 Design Testing and Results…………………………………………………….….16

IV.1.A Equipment Used…………………………………………………….…..16

IV.1.B Testing Procedure…………………………………………………….…16

IV.1.C Testing Results………………………………………………………….17

IV.2 Cost Analysis………………………………………………………………………20

IV.3 Conclusions……………………………………………………………………….. 21

Appendices……………………………………………………………………………………..23

Appendix A: Sample Calculations……………………………….….……………….24

Appendix B: Injector Part Drawings………………………………………………....29

Appendix C: Parts List……………………………………………………………….32

Appendix D: Time and Personnel Management……………………………………..33

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Introduction

Flow-blurring fuel injectors would be desirable for use in turbine engine applications that

are running on high viscosity biofuels. They can also be quickly adjusted to operate in the flow-

focusing regime, if desired. High viscosity fuels are not as quick to vaporize as more conventional

fuels like gasoline. A common automotive injector can simply spray gasoline into a combustion

chamber to vaporize and mix with the incoming air quite readily. A thicker fuel is not as easily

vaporized by conventional injectors. This is one way a flow-blurring injector can be useful. When

certain geometrical and flow conditions are met within the injector nozzle and around the exit

orifice, a flow-blurring injector that is operating in the flow-blurring regime can effectively

vaporize even the thickest of fuels, which allows easy mixing with intake air so that efficient

combustion can be achieved.

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Project Objectives

Design unique flow-focusing to flow-blurring fuel injector using Solidworks

3-D print design

Install leak-proof and reliable fuel and air connections

Set up test lab with all necessary equipment

Outline experiment plan for relating spray characteristics to ALR (air-liquid ratio) and

H/D ratio (offset distance to fuel feed tube diameter ratio)

Conduct experiments and collect desired data

Organize data into neat and presentable form

Discuss what has been learned from the experiments

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Section I

Project Constraints

In this context, project constraints are defined as limitations that prevent the design from

becoming the best it can be. These will include time, cost, and material constraints, among others.

The constraints for this project are as follows:

Material Constraints:

The material is limited to 3-D printable plastic like PLA or ABS.

Size Constraints:

The size of the full assembly must be as small as practicable, while still allowing

installation of a 1/16” NPT compression fitting for liquid and a 3/8” NPT air hose adapter.

Financial Constraints:

An arbitrary budget limit of $500 was set by Dr. Jiang. The Cole-Parmer liquid pump was

$2400 and specifically purchased by Dr. Jiang, so the budget was not affected by this purchase.

Time Constraints:

Approximately 13 weeks was available from the start of project to final presentation on

April 28, 2016.

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Section II

Background Research

The three main factors for producing a better spray pattern are maximized surface

production, minimized droplet coalescence, and minimized gas expense. All of these are increased

by a new atomization technique called flow-blurring atomization. Flow-blurring atomization was

a concept which was first conceptualized by Dr. Alfonso GaΓ±Γ‘n-Calvo, a fluid mechanics professor

at the University of Seville in Spain. It was GaΓ±Γ‘n-Calvo’s idea to create an atomizer that is simple

yet effective. His concept takes advantage of turbulent gas currents in order to create a more

efficient atomization of liquid. In his studies, he observed that at a certain height to diameter ratio,

a backflow of gas is introduced into the fluid stream which acts to break up the fluid. When the

ratio, Ξ¨= H/D, is greater than 0.25, a pattern termed flow-focusing spray is observed. This pattern

is characterized by a micro-jet, which either can break up in a symmetric or asymmetric pattern

depending on the Weber number. When this ratio Ξ¨ is less than or equal to 0.25, a turbulent

backflow can be observed. Dr. GaΓ±Γ‘n-Calvo refers to this as flow-blurring. This phenomenon

increases the surface of spray up to fifty times more than standard plain-jet air blast type atomizers

which observe flow-focusing spray. A model of this design can be seen below in Figure 1.

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Figure 1: Schematic of the Simple Nozzle Geometry Used

One of the advantages of this design is that the effects of viscosity become negligible. This

means that this atomizer can be applied to a variety of fluids and that the material used for

constructing the model is also able to be varied.

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Section III

Design Process

III.1 Design Criteria

Design criteria are guidelines or rules that must be met when designing the models. The

design criteria for this fuel injector were communicated verbally by the team’s advisor, Dr. Jiang.

Requirements for a flow-blurring injector were also outlined by Dr. GaΓ±Γ‘n-Calvo in his paper. 1

These criteria are as follows:

Offset distance (H) must be adjustable, so that H/D can be varied

Fuel feed tube diameter (D) must be either adjustable or interchangeable

Injector nozzle must attach to some sort of holder, so that fuel and air lines can be

connected

All parts must be 3-D printable

Exit orifice diameter must equal fuel feed tube diameter

1 GaΓ±Γ‘n-Calvo,Alfonso. Enhanced Liquid Atomization: From flow-focusing to flow-blurring.

Applied Physics Papers 86 2005

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III.2 Design Evaluation Process

Several models were designed over the course of three months. Once the team outlined

the design criteria and constraints, ideas were brainstormed and then modeled with Solidworks.

Going with the advice of the team’s advisor and client, Dr. Jiang, small changes were made with

each iteration. The ultimate goal was to produce an injector that was suitable for use in a small

turbine engine. Once this final design was satisfactory, it was 3-D printed by Idea Zoo, a company

that specializes in producing parts from CAD designs. Figure 2 shows a morphological chart that

helped with design selection.

Figure 2. Morphological chart

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III.3 Designs Created

Here, several versions of the injector design are shown as it evolved. Figure 2 shows the

first idea of the injector model.

Figure 3. First idea

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This first idea was modified to decrease the size and increase the wall thickness of the outer

shell that holds air pressure.

After more team brainstorming sessions and spending more hours into putting these ideas

into Solidworks, an injector holder was designed as well as a new exit orifice cap. These early

ideas are shown in Figures 4, 5, and 6 below.

Figure 4. First exit orifice cap design

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Figure 5. First injector holder

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Figure 6. First design of injector and holder assembly

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After consulting with Dr. Jiang, she suggested we make the parts even smaller and modify

the fuel feed tube. This resulted in the design shown in Figures 7 and 8.

Figure 7. Injector holder

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Figure 8. Injector holder section view

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Further modifications were made to this design so that fuel and air attachments could be

installed on the injector holder. This resulted in the design that was 3-D printed, tested, and is still

in use today. This design is shown in Figures 9 and 10.

Figure 9. 3-D printed design

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Figure 10. 3-D printed design section view

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Section IV

Final Design Details

IV.1 Design Testing and Results

IV.1.A Equipment used:

Cole-Parmer water Pump

Air compressor

Air flow meter with stand

Test stand

Nikon D3100 camera

IV.1.B Testing Procedure

Water is used for liquid and air is used for gas in this experiment. To find the relationship

between Air-Liquid ratio (ALR) and spray angle for each H/D ratio, air flow rate is fixed at 1

SCFM while liquid flow rate is increased from 20 mL/min to 240 mL/min with 20mL/min

increments. This is repeated for two H/D ratios of 0.19 and 0.375. Images of each spray for every

set of conditions were captured with the Nikon digital camera.

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IV.1.C Testing Results

Graph 1: Comparison of the two flow regimes

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Graph 2: Flow-blurring regime

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Graph 3: Flow-focusing regime

The spray angle was measured from the images captured during experimentation. This

was accomplished by using the computer program ImageJ, which has the ability to determine

angles referenced in images. The angles were then plugged into an Excel spreadsheet according

to the GLR which they were tested at. From this Graphs 1-3 above were produced.

Upon observation of the graphs, it appears that as ALR (GLR) increases, the spray angle

decreases. A smaller spray angle correlates to smaller liquid droplets, because larger droplets have

a larger momentum and are thus more likely to escape from the center of the exit orifice. This is

what we would intuitively expect. The air mass flow rate was determined from a flow meter and

recorded. The liquid flow rate was read and recorded from the pump directly.

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IV.2 Cost Analysis

Table 1: Price List

Total Price: $2900

Each member of the group of five students spent at least 5 hours a week to

work on this project, totaling 65 hours each.

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IV.3 Conclusions

The team took about six weeks to design a fuel injector with Solidworks that would be

reliable and satisfactory for testing purposes. This final design was 3-D printed by a private

company, Idea Zoo. The cost to make all the fuel injector parts of ABS plastic was $20.

The test lab was set up with an air compressor, which Heath Headley brought from

home. Dr. Jiang bought a Cole-Parmer liquid pump that accurately delivers a desired flow rate.

A test stand was bought that holds the injector during experiments. Dr. Jiang also supplied an air

flow meter that was later attached to a wooden stand.

An experiment plan was outlined. It was desired to relate ALR and H/D to the resulting

spray pattern. Pictures were taken with Heath’s camera, and these pictures were matched with

their respective ALR and H/D values.

When the injector was tested in the flow-blurring regime (H/D=0.19) with an ALR around

1.0-1.5, the water spray appears to fully vaporize with a small spray angle. When the ALR is

around 0.3-0.7, it is clear to see a small micro-jet with a wider spray angle, presumably because

the exit velocity of the air-water mixture is lower. This would indicate a higher droplet size, and

incomplete vaporization. We can conclude from this that a higher ALR is more desirable. An

ALR>1 would be ideal.

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The injector was also tested in the flow-focusing regime, with H/D=0.38. With a low ALR

of around 0.3-0.7, the liquid micro-jet is clearly visible. With a higher ALR, the micro-jet is still

visible but smaller, and the spray angle is smaller because the exit velocity is higher.

We can conclude that this injector operates as expected when in the flow-blurring mode by

completely vaporizing the water that running through it. If there were more time, it would be

interesting to conduct more precise experiments with more sophisticated equipment. For instance,

we would like to test many values of ALR, while taking pictures with a camera that is fixed in

place. It would also be desirable to measure the droplet size directly, and then produce a graph of

droplet size vs. ALR. It is also possible that this design could be used in a turbine engine if it were

made of steel. This might be feasible if a few small changes were made to the design, so that it

could be made with a lathe and milling machine.

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Appendices

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Appendix A

Relevant Equations and Sample Calculations

Theoretical Mass Flow Rate of Air (that could be used in later

experiments)

(Compressible Flow)

mass flow rate of air = π€πŒπšπ‘·π’βˆš

π’Œ

𝑹𝑻𝒐

[𝟏+(π’Œβˆ’πŸ)π‘΄π’‚πŸ

𝟐]

π’Œ+𝟏(𝟐(π’Œβˆ’πŸ))

A: Area of exit orifice = 𝝅

πŸ’π‘«πŸ units: (π’ŽπŸ)

Ma: Mach number = 𝑽

π‘ͺ=

𝑽

βˆšπ’Œπ‘Ήπ‘» units: (dimensionless)

𝑷𝒐 : Stagnation pressure in tank units: (1kPa= 0.145 psi)

k: Specific heat ratio of air = 1.4 (dimensionless)

R : Specific gas constant of air =0.287 units: ( π’Œπ‘·π’‚βˆ’π’ŽπŸ‘

π’Œπ’ˆβˆ’π‘² )

𝑻𝒐 = π’”π’•π’‚π’ˆπ’π’‚π’•π’Šπ’π’ π’•π’†π’Žπ’‘π’†π’“π’‚π’•π’–π’“π’† π’Šπ’ π’•π’‚π’π’Œ π’–π’π’Šπ’•π’”: [(𝑲 = 𝑭 + πŸ’πŸ”πŸŽπ’ )πŸ“

πŸ—]

To find Ma, π‘·π’•π’‚π’π’Œ,𝒂𝒃𝒔

π‘·π’‚π’•π’Ž= [𝟏 + (

π’Œβˆ’πŸ

𝟐) π‘΄π’‚πŸ ](

π’Œ

π’Œβˆ’πŸ)

π‘·βˆ—

𝑷𝒐 =0.5283 Note: Back pressure must be

π‘·βˆ— 𝒐𝒓 𝒍𝒆𝒔𝒔 𝒇𝒐𝒓 π’„π’‰π’π’Œπ’†π’… π’‡π’π’π’˜. 𝑰𝒇 π‘·π’‚π’•π’Ž ≀ π‘·βˆ— , π’‡π’π’π’˜ π’Šπ’” π’„π’‰π’π’Œπ’†π’… 𝒂𝒏𝒅 𝑴𝒂=1

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Unit Conversions

SCFM (Standard cubic feet per minute)

SCFM is volume flow rate corrected to standard ambient

temperature and pressure)

πŸπ’‡π’•πŸ‘

π’Žπ’Šπ’(

πŸπ’Žπ’Šπ’

πŸ”πŸŽπ’”) (

𝟎. πŸŽπŸπŸ–πŸ‘π’ŽπŸ‘

πŸπ’‡π’•πŸ‘) = πŸ’. πŸ•πŸπŸ• βˆ— πŸπŸŽβˆ’πŸ’

π’ŽπŸ‘

𝒔

πŸπ’‡π’•πŸ‘

π’Žπ’Šπ’= πŸ’. πŸ•πŸπŸ• βˆ— πŸπŸŽβˆ’πŸ’

π’ŽπŸ‘

𝒔

οΏ½Μ‡οΏ½ = 𝝆𝑸 = 𝝆𝑨𝒗 π†π’‚π’Šπ’“ 𝒂𝒕 𝑺𝑻𝑷 = 𝑷𝒂𝒃𝒔

π‘Ήπ’‚π’Šπ’“π‘»π’‚π’ƒπ’”

π†π’‚π’Šπ’“ =𝟏𝟎𝟏 π’Œπ‘·π’‚

𝟎.πŸπŸ–πŸ•βˆ—πŸπŸ—πŸ– 𝑲= 𝟏. πŸπŸ–

π’Œπ’ˆ

π’ŽπŸ‘ (Estimated)

οΏ½Μ‡οΏ½ = 𝟏. πŸπŸ–π’Œπ’ˆ

π’ŽπŸ‘βˆ— πŸ’. πŸ•πŸπŸ• βˆ— πŸπŸŽβˆ’πŸ’

π’ŽπŸ‘

𝒔= πŸ“. πŸ• βˆ— πŸπŸŽβˆ’πŸ’

π’Œπ’ˆ

𝒔 𝒑𝒆𝒓 𝟏 𝑺π‘ͺ𝑭𝑴

Liquid Flow

𝟏 π’Žπ‘³

𝟏𝟎𝟎𝟎 π’Žπ‘³(

πŸπ’Œπ’ˆ

𝟏𝟎𝟎𝟎 π’Žπ‘³)

π’˜π’‚π’•π’†π’“(

πŸπ’Žπ’Šπ’

πŸ”πŸŽπ’”) = 𝟏. πŸ”πŸ• βˆ— πŸπŸŽβˆ’πŸ“

π’Œπ’ˆ

𝒔

𝟏 π’Žπ‘³

π’Žπ’Šπ’= 𝟏. πŸ”πŸ• βˆ— πŸπŸŽβˆ’πŸ“

π’Œπ’ˆ

𝒔

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How to set offset distance for testing (H)

Threads: M19 x 1.5

Pitch = 1.5 mm/turn D=2mm

=0.375mm/ 𝟏

πŸ’ turn

For 𝑯

𝑫= 𝟎. πŸŽπŸ—πŸ‘πŸ•πŸ“ 𝑯 = 𝟎. πŸπŸ–πŸ•πŸ“ (

𝟏

πŸ– 𝒕𝒖𝒓𝒏)

𝑯

𝑫= 𝟎. πŸπŸ–πŸ•πŸ“ 𝑯 = 𝟎. πŸ‘πŸ•πŸ“ (

𝟏

πŸ’ 𝒕𝒖𝒓𝒏)

𝑯

𝑫= 𝟎. πŸπŸ–πŸπŸπŸ“ 𝑯 = 𝟎. πŸ“πŸ”πŸπŸ“ (

πŸ‘

πŸ– 𝒕𝒖𝒓𝒏)

𝑯

𝑫= 𝟎. πŸ‘πŸ•πŸ“ 𝑯 = 𝟎. πŸ•πŸ“ (

𝟏

𝟐 𝒕𝒖𝒓𝒏)

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Matlab program used during testing to calculate ALR

Figure 11. ALR program

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Figure 12. ALR program code

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Appendix B

Injector Part Drawings

Drawing 1. Injector Holder

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Drawing 2. Exit Orifice

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Drawing 3. Injector nozzle

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Appendix C

Parts List

Swagelok compression fitting Part #: SS-400-1-1

3/8” NPT air hose adapter got from home

¼” OD fuel hose Guidry Hardware

Two air hoses one from home, one bought from Wal-Mart

3-D printed parts Idea Zoo

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Appendix D

Time and Personnel Management

Figure 13. Gantt chart

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Figure 14. Personnel flow chart