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MINI-REPORT #1: RESEARCH AND CONCEPTUAL DESIGN

ENGI 8926: MECHANICAL DESIGN PROJECT II

GROUP 5

Bret Kenny 200902518

Chintan Sharma 200943512

Lida Liu 200814853

Piek Suan Saw 200829760

Revision Created by Date Reviewed

by Date Approved by Date

1 Group 5 2/7/14 Group 5 2/7/14 Dr. Yang

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Mini-Report # 1 February 2014 !

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Table of Contents 1.0! Introduction ........................................................................................................... 1!

1.1! Background ................................................................................................. 1!1.2! Scope ........................................................................................................... 1!1.3! Design Methodology ................................................................................... 1!1.4! Project Constraints ...................................................................................... 2!

2.0! Background Research ............................................................................................ 2!2.1! Existing Industrial Solutions ....................................................................... 2!

2.1.1!Vertical Submersible Pumps .............................................................. 2!2.1.2!Electrical Submersible and Sub-turbine Pumps (Turbine Pumps) .... 4!2.1.3!Axial-Flow Propeller Pumps ............................................................. 5!2.1.4!Positive Displacement Motors (PDMs) ............................................. 6!2.1.5!Turbodrill ........................................................................................... 6!2.1.6!PDM versus Turbodrill Selection Criteria ......................................... 7!2.1.7!Pelton Wheel Turbine ........................................................................ 8!2.1.8!Francis Turbine .................................................................................. 9!2.1.9!Kaplan Turbine ................................................................................ 10!2.1.10! Turgo Turbine ............................................................................. 10!

2.2! Fluid Mechanics Theory ............................................................................ 11!3.0! Concept Selection ................................................................................................ 13!4.0! Conclusion ........................................................................................................... 15!5.0! Recommendation ................................................................................................. 15!

5.1! Compatibility Tool .................................................................................... 15!5.2! Pressure Relief Valve ................................................................................ 15!5.3! Gearbox ..................................................................................................... 16!5.4! Bearings ..................................................................................................... 16!5.5! Housing ..................................................................................................... 16!

6.0! References ........................................................................................................... 17!!!!!!!!!

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Tables Table 1: Berkeley Vertical Submersible Pump ................................................................... 4 Table 2: Turbine Concepts ................................................................................................ 13 Table 3: Design Selection Criteria .................................................................................... 13 Table 4: Kaplan Turbine criteria justification ................................................................... 14

Figures Figure 1: Vertical Submersible Pump (TrimLine 4" Submersible Pumps) ........................ 3 Figure 2: Berkeley's 6T Sub-turbine Series Pump (6T SubTurbine Series) ....................... 4 Figure 3: Axial-Flow Pump Guide and Propeller (Axial Flow Pumps) ............................. 5 Figure 4: PDM schematic and performance curve (Delucia, PDM vs. Turbodrill) ............ 6 Figure 5: Turbodrill schematic and performance curve (Delucia, PDM vs. Turbodrill) .... 7 Figure 6: Pelton Wheel schematic and performance curve (nptel, Fluid Machinery) ........ 9 Figure 7: Francis turbine schematic (Manual on Pumps used as Turbines) ..................... 10 Figure 8: Kaplan Turbine schematic and performance curve (Kaplan Turbines) ............ 10 Figure 9: Turbo Turbine model (Turgo Turbine) ............................................................. 11 Figure 10: Turbine velocity vectors .................................................................................. 12

Appendices Appendix A: SolidWorks Drawing Appendix B: Gearbox and Transmission Research Appendix C: Bearing Research Appendix D: Housing Research Appendix E: Berkeley Vertical Submersible Pump


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1.0 Introduction 1.1 Background The design project undertaken by Group 5 for the ENGI 8926 course is in relation to research work being completed by the Advanced Drilling Group (ADG) in the engineering faculty at the Memorial University of Newfoundland (MUN). A major issue that has presented itself during drilling operations in the oil and gas industry is reduced rate of penetration (ROP) due to the negative impact of downhole vibrations within the drill string. Conventionally, drilling engineers try to design the drill string to avoid excess vibrations and to maximize the ROP. However, the ADG at MUN has conducted research that indicates by inducing high-frequency, low-amplitude, axial vibrations near the drill bit, the ROP can be increased. To further test this theory, members of the ADG are designing a downhole tool that can induce high-frequency, low-amplitude vibrations to the drill bit. However, this vibration tool requires a power source. The design of a tool that can provide power to the vibration tool and other downhole tools is the main objective of Group 5’s design project.

1.2 Scope To meet the power requirements of downhole tools, a downhole turbine assembly will be designed to be used during drilling operations. The turbine assembly will use the flow of drilling fluid inside the drill string to turn a drive shaft. The rotating drive shaft can be used to power or actuate other drilling tools such as turbodrills, electrical generators, hydraulic motors, and a variety of other mechanical, electrical or hydraulic devices. The downhole turbine assembly design will be focused on providing the necessary output parameters to service other downhole tools. The design will use commercially available components and/or designs when applicable and will not involve research and development activities to design new components. Lastly, the design and incorporation of other downhole tools necessary to run coincident with the downhole turbine assembly lie outside the scope of this project effort.

1.3 Design Methodology This project will be completed in three main phases. First, background research will include a comprehensive review of existing commercial and pre-commercial downhole turbines to develop a comprehensive understanding of the configurations and variations between these systems. This will involve review of published scientific literature, product catalogues and technical manuals and guides, patent applications, and fluid mechanics analysis of turbine operation. Secondly, concept generation and selection will take place based upon relevant information gathered during the research phase. This will involve the selection of the turbine power section and the development of high-level design drawings. Lastly, the detailed design phase will include all necessary analysis to design the downhole turbine in its entirety. This includes but is not limited to fluid flow


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analysis, stress analysis, selection and sizing of all components, and system optimization.

1.4 Project Constraints Downhole tools used during drilling operations must be designed with many factors in mind. These factors mainly arise from the conditions in which the tools must operate. The table below highlights the major design constraints for the downhole turbine assembly. Constraint Description Size • Diameter = 6.0”

• Length = 6.0’ Output • 600-800 RPM Input • Flow range = 150-300 gal/min

• ∆P < 500psi Strength (Axial, Compressive, and Torsional)

• Tool strength designed to API drill pipe specifications

Operational Conditions • Water-based drilling mud system Modular Design • Couple multiple turbine assemblies Cost • Minimize Health, Safety & Environment • Pressure build-up mitigation device,

compliance tool

2.0 Background Research 2.1 Existing Industrial Solutions

2.1.1 Vertical Submersible Pumps Deep-water submersible pumps are used in the agricultural, irrigation and oil and gas industries. These pumps transport fluid vertically from wellbore to surface by providing energy or head to the fluid. Most of these pump units are centrifugal pumps that convert rotational kinetic energy from a motor to hydrodynamic energy that moves the working fluid. A typical submersible pump comprises impellers, bearings, bushings, and rotary shafts. Depending on power requirements, several stages (or impellers) can be added to pumps. Typically, these pumps are powered by an electric motor. Working principle In a typical multi-stage pump, fluid enters from an intake screen where it experiences high centrifugal forces caused by high rotational speeds of the driven impeller. The fluid exits the impeller and moves to a diffuser, which directs the flow axially to the next stage of the pump. Each stage pushes the fluid upwards by providing pressure head. These impellers are rotated using a driven shaft that runs by means of a downhole motor (Takacs, 2009, pg. 53). Figure 1 below highlights the basic configuration of a standard vertical submersible pump.


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!Figure 1: Vertical Submersible Pump (TrimLine 4" Submersible Pumps)

One approach to address this design challenge is to reverse engineer the working of a vertical submersible pump to convert potential energy of the fluid into mechanical energy for rotating a shaft. According to research conducted by Williams, centrifugal pumps running in reverse provides a great high-power, low-cost solution to generate power (Williams, 1995, pg 2-8). However, based on our project constraints some limiting factors must be considered before using centrifugal pumps as turbines. Some of these constraints are: • To achieve high efficiency, the turbines require significant operating head (~30 m) or

high flow rates • Centrifugal pumps used as turbines lead to change in flow directions resulting in non-

axial flow • The blade angle and arrangement of guide vanes in a pump can lead to loss of fluid

energy when used as a turbine. The loss of fluid energy restricts the use of additional stages to increase the overall turbine efficiency.

To check the compatibility of the centrifugal pumps to be used as turbines, an experiment to dissemble a used Berkeley’s TrimLine 4” Vertical Submersible Pump was conducted. Table!1 below tabulates key objectives, observations, and results from the experiment.

Pump!Unit!

Water!intake!screen!

Motor!!


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Table 1: Berkeley Vertical Submersible Pump

Parts Objective Observation Results/ Conclusions Rotor- Stator System

Compatibility of blade shape and angle. Direction of flow when used as a turbine.

Blades design not optimum to be used as turbine. Vanes on stator obstructs the flow when used as turbine.

Required impeller design should direct flow in axial direction. Guide vanes not necessary. Try turbine pumps.

Shaft Shaft Diameter; Connection between rotor and shaft

Diameter of shaft 1.25 cm. Shaft was fitted using shaft key

Similar shaft key can be used in connecting turbine with drive shaft.

Bearing Types and location of bearings.

Both thrust and ball bearings were used in center and each end of shaft

Location and type of bearings can be used

Motor Check if motor can be used in future

Windings on the motor were damaged

Motor was damaged beyond repair

* See Appendix E for pictures of Berkeley Vertical Submersible Pump

2.1.2 Electrical Submersible and Sub-turbine Pumps (Turbine Pumps) One of the main limitations for a centrifugal pump to be used as a turbine is the blade design of the rotor-stator assembly. This limitation can be resolved by using turbine pumps. The working principle of turbine pumps is similar to centrifugal pumps. However, instead of using a rotor-stator assembly, turbine pumps have impellers that move the fluid in the vertical direction. Hence, Berkeley’s 6T Sub-turbine Series was considered, as it has a better impeller design compared to centrifugal pumps. Figure 2 below shows the section view of both these pumps.

Figure 2: Berkeley's 6T Sub-‐turbine Series Pump (6T SubTurbine Series)


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Initial analysis of the impeller design, lead to the conclusion to use turbine pumps as turbines to meet the requirements of the project. However, discussions with a representative from Berkeley Pumps concluded that when fluid direction is reversed, these pumps provide poor performance resulting in significantly low efficiencies in the range of approximately 5-15% (Drew Taylor, personal communication via telephone, Jan 20, 2014).

2.1.3 Axial-Flow Propeller Pumps Axial-flow propeller pumps consist of a propeller instead of rotor-stator or impeller assembly. In addition, some of these pumps have guide vanes to direct the flow. Figure!3 below illustrates the propeller and guide vanes of a standard axial pump assembly. These axial-flow pumps are currently being in used in both the agricultural and irrigation industries. They are commercially used in sewage treatment plants for drainage and water control purposes. In order to analyze the use of axial-flow propeller pumps as turbines, the team discussed the feasibility of the propellers for the purpose of our project with Dr. M. Hinchey. From the discussions the team concluded following key points: • Propeller pumps used as turbines can achieve higher efficiencies while

operating at low head. However, high flow rate will be required. • Blade (and guide vane) design is easy to manufacture, analyze, configure and

optimize. • The spacing between the blades provides flexibility to use fluid with varying

rheology. • Detailed design analysis of propeller type turbines is currently ongoing within

the Faculty of Engineering at Memorial University of Newfoundland supervised by Dr. M. Hinchey.

!Figure&3:&Axial<Flow&Pump&Guide&and&Propeller&(Axial&Flow&Pumps)

Guide!Vanes!

Propeller!


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2.1.4 Positive Displacement Motors (PDMs) According to Schlumberger’s oilfield glossary definition, a positive displacement motor (PDM) is used to provide power to the drill bit or other downhole tools in directional drilling applications. (Positive Displacement Motors) The internal make-up of a PDM contains a steel rotor with a plastic stator assembly. The rotor is designed to have a number of lobes (n), while the stator has a number of lobes equal to (n+1). The open space developed due to the differing number of lobes develops a region of high pressure, which ultimately turns the rotor. When fluids flow through the motor, the tool is running free of bottom. The fluid circulating pressure increases as the bit touches the bottom and weight is added. This increase in pressure is known as pressure drop across the motor, Pm. Pm varies proportionally to the bit weight. (Delucia, PDM vs. Turbodrill)

The constructional drawing and theoretical performance curve along with some performance characteristics for a PDM are summarised in the table below. (Delucia, PDM vs. Turbodrill)

!Figure&4:&PDM&schematic&and&performance&curve&(Delucia,&PDM&vs.&Turbodrill)&

Performance Characteristic: • Eefficiency: Maximum at motor pressure drop slightly above nominal

operating motor • Torque, T ; Horsepower, Pout Proportional to Pm • Rotational Speed, N: Proportional to fluid volume, Q circulating through

motor. Remains constant despite change in torque requirement (Delucia, PDM vs. Turbodrill)

2.1.5 Turbodrill A turbodrill assembly contains a staged turbine section. A stage consists of a rotor and stator pairing. The turbodrill design includes several of these stages in series to extract the maximum amount of energy from the passing fluid. The rotor in a turbodrill contains blades extending radially from the drive shaft, and the rotor provides vanes to align the flow in the necessary direction to maximize efficiency. (Works, Madden) Power is developed as the fluids to pass through stator to the


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rotor blades, thus creating rotation. The entrance and exit angle of the blades profile are manipulated to optimize the velocity triangle, thus optimizing the output power. (Delucia, PDM vs. Turbodrill) The constructional drawing and theoretical performance curve along with some performance characteristics for a turbodrill is summarised in the table below. (Delucia, PDM vs. Turbodrill)

!Figure&5:&Turbodrill&schematic&and&performance&curve&(Delucia,&PDM&vs.&Turbodrill)&

Performance Characteristic: • Efficiency: Maximum at motor speed slightly above or below maximum

output horsepower • Drilling Torque: Zero at runway speed. Maximum at stall (Ts). Operating

Torque (To) is half Ts at operating speed • Horsepower Output: Zero at stall point and runway speed. Maximum at

operating speed or half the runway speed. • Pressure Drop: Maximum at slightly above or below maximum horsepower

output (Delucia, PDM vs. Turbodrill)

2.1.6 PDM versus Turbodrill Selection Criteria The selection between PDM and Turbodrill should be made to achieve optimal drilling parameters in order to maximize the rate of penetration (ROP). The following criteria require consideration during the decision-making process. (Delucia, PDM vs. Turbodrill) 1. Rotational Speed Industry experience suggests the ideal condition for drilling motor is 100-200 rpm for rock bits and 250-1500 rpm for diamond bits. PDM and Turbodrill have been widely used for straight-hole drilling. However, PDM is the primary choice for directional operations using rock or diamond bits. Both bits in PDM can meet the rotational speed requirements. The high rotating output speed offered by


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Turbodrill can cause issues with bearing components. (Delucia, PDM vs. Turbodrill) 2. Power Output The power-producing element in a PDM is the motor. The power output for a turbodrill depends primarily on the number of stages and the exit blades’ angle. However, the permissible total stand length limits the upper limit of the number of stages. (Delucia, PDM vs. Turbodrill) 3. Operating Temperature and Pressure One of the major restrictions for PDMs is the maximum permissible operating temperature and resistance to oil based mud systems. This is because elastomer is used as the stator material. However, new techniques and procedures have been introduced to allow PDM usage under hot temperature environments. For example, with current nitrile compounds, PDMs can drill formations up to 340 degrees Fahrenheit. Turbodrill is designed to perform in high temperature and oil based mud environments. (Delucia, PDM vs. Turbodrill) 4. Durability Although Turbodrill has a higher operational cost than PDM, it is more favorable when considering the tool’s performance and durability. The rotor and stator in Turbodrill is expected to have a longer lifespan because there is no mechanical contact between the two components. Therefore, only the drilling mud causes the abrasion and erosion on the rotor and stator. (Delucia, PDM vs. Turbodrill) PDM, on the other hand, is more susceptible to wear due to the constant contact and movement between rotor and stator.

2.1.7 Pelton Wheel Turbine Pelton wheel turbines are classified as impulse turbines. That is, the Pelton wheel converts kinetic fluid energy into mechanical rotational energy through the use of a nozzle and high-velocity jet. The jet strikes buckets located on the perimeter of the wheel causing the rotation of the turbine shaft. The Pelton turbine is most efficient when high-head and low-flow rate is available, and low power generation is required. (Hinchey, Fluid Power Machines) The Pelton turbine contains three main components: a nozzle, a runner, and a casing. The runner contains multiple buckets, which turn the incoming jet approximately 180 degrees to maximize the momentum transfer from the flow to the wheel. The plot below indicates the expected efficiencies of a laboratory sized Pelton wheel based on the relationship between flow rate vs. rotational speed. (Hinchey, Fluid Power Machines)


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!Figure&6:&Pelton&Wheel&schematic&and&performance&curve&(nptel,&Fluid&Machinery)&&

Pelton!wheel!turbines!offer!little!advantage!with!respect!to!the!operation!of!downhole! tools.! Firstly,! they! require! high! head,! and! low! flow! rate! flows,!which!does!not!comply!with!drilling!operation!requirements.!(Hydropower)!Secondly,! the! use! of! a! nozzle! in! the! tool! would! develop! high! differential!pressures! and! increase! the! potential! of! blockages.! Lastly,! due! to! flow!restriction,! Pelton! wheels! would! not! be! suitable! for! the! development! of! a!modular!downhole!assembly.!!

2.1.8 Francis Turbine Francis turbines are classified as a reaction turbine. Instead of using an external nozzle, reaction turbines are completely filled with fluid that imparts a momentum change as it flows over the blades. Francis turbines are the most popular turbines used in hydroelectric generation because they can be used efficiently over a broad range of operating conditions (Head: 45 – 400m, Flow rate: 10-700 m3/s) (Working of Francis Turbine) The most important feature of Francis turbines is their blade design. They have a thin airfoil-like cross-section and are bucket shaped, as shown in Figure 7 below. The airfoil and bucket shape characteristics of the blades results in the development of lift and impulse forces that combine to rotate the turbine shaft. Francis turbines intake flow radially and output flow axially. Therefore, they are equipped with an inlet flow channel that distributes the flow evenly about the perimeter of the inlet. They also require the use of guide vanes to angle the inlet flow to maximize efficiency. (Working of Francis Turbine) Francis turbines have some of the desirable characteristics required for a downhole turbine assembly. The main one being that they are able to operate in a broad range of efficient operating conditions, such as in the high flow, low head conditions in drilling operations. However, they have many undesirable features as well including the radial flow at the inlet, and flow restrictions. These features would restrict the implementation of a modular tool. (Working of Francis Turbine)


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!Figure&7:&Francis&turbine&schematic&(Manual&on&Pumps&used&as&Turbines)

2.1.9 Kaplan Turbine Kaplan turbines are classified as a reaction turbine. They are axial flow devices that intake and output water in the axial direction (parallel to the rotating shaft). The blades of a Kaplan turbine are analogous to a propeller. They have a thin airfoil-like cross-section, which leads to the development of a lift force that rotates the turbine. In many Kaplan turbines, the blades have adjustable angles to accommodate for a variety of operating conditions. In general, Kaplan turbines are used in systems with low head and high flow rate. In addition, as shown in Figure 8 below, Kaplan turbines are efficient across a broad range of flow rates or loads. (Working of Kaplan Turbine) Kaplan turbines have great characteristics for implementation in a downhole turbine assembly. They have a wide range of operating conditions, large flow areas, and they are easily staged to develop a modular downhole tool assembly. (Working of Kaplan Turbine)

!Figure&8:&Kaplan&Turbine&schematic&and&performance&curve&(Kaplan&Turbines)

2.1.10 Turgo Turbine Turgo turbines are classified as an impulse turbine and were initially developed as development upon the Pelton wheel. Turgo turbines are designed to use a higher flow rate and be manufactured cheaper than Pelton wheels. However, other than that, both the Pelton wheel and the Turgo turbine offer mainly the same characteristics with respect to practical application. (Turgo Turbine)


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!Figure&9:&Turbo&Turbine&model&(Turgo&Turbine)

2.2 Fluid Mechanics Theory The field of fluid dynamics involves many components. One area of relevant interest is the interaction between fluids and machines. Specially, the means by which fluids can power machines, or vice versa, the means by which machines can perform work on fluids. Machines that interact with fluids in this manner are called fluid machines. (Fox and Macdonald) In general, there are two classifications of fluid machines: pumps and turbines. Pumps are classified as machines that perform work/power on a fluid, whereas turbines extract work/power from a fluid. Pumps and turbines are similar and share many mathematical relationships that can be used to evaluate the output of a system or performance characteristics. Turbines The main objective of a turbine is to extract work/power from a fluid. One of the most common turbines used today is called a hydraulic turbine for which water is the working fluid. Hydraulic turbines are used in a broad range of applications and are subdivided into two main classes: impulse and reaction turbines. (Fox and Macdonald) In general, a turbine consists of a stator and rotor pairing, called a stage (Figure 10). A stator is used to accelerate the flow and convert some of its pressure energy into kinetic energy. While a rotor is used to extract the flow’s kinetic energy via a set of blades, vanes or buckets mounted on a wheel connected to an output shaft. Impulse turbines are driven through the use of a high-speed jet. Therefore, the entire pressure drop across them takes place within the nozzle generating the jet and not on the turbine blades. The jet comes in contact with buckets on the turbine wheel. The buckets cause the jet’s flow stream to turn and exit the bucket in a direction approximately opposite to that which it entered (Figure 10). This change in flow direction results in a large momentum change of the fluid, which is ultimately responsible of the extraction of work from the fluid. (Fox and Macdonald) Reaction Turbines are driven by the turning of an external fluid stream to contact the angled turbine blades to maximize efficiency. Therefore, the pressure drop across reaction turbines is due to the external acceleration required to turn the


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fluid and also due to the moving blades within the turbine. Similar to the impulse turbine buckets, reaction turbine blades turn the flow that contacts the blades, which results in a change in momentum and thus an extraction of work from the fluid. Due to the fact that reaction turbines flow full of fluid, they are often capable of producing more power output for a given size compared to impulse turbines. (Fox and Macdonald)

!Figure&10:&Turbine&velocity&vectors&

The Angular-Momentum Principle: The Euler Turbomachine Equation The equations described below were developed by Leonhard Euler and can be used to calculate the net torque output from a hydraulic turbine. Equation 1 below describes the conservation of angular momentum for a fluid passing through a fluid machine. An arbitrary specific group of fluid particles passing through a fluid machine is represented in Equation 2 with volume V and surface area S. A differential volume dV within V contains an angular momentum equal to (r x ρdV v), where ρ is the fluid density, r is the radius vector measured from the axis of rotation, and v is the velocity vector. Performing integration over the volume V and surface S results in the total angular momentum of the group of particles. According to the Euler formula, this is equal to the net torque input or output from a fluid machine. (Hinchey, Fluid Machinery)

Equation 1: !!" !!×! ρ!! dV = !!"#$%

Equation 2: !!× !! !!!!! !dV+ !!×! ρ! !! ∙ !!dS = !!"#$% The result of the integration can be represented as a scalar equation. Equation 3 below indicates that the net torque output is equal to the difference of the product of mass flow rate and tangential velocity at the inlet and exit of the fluid machine. In equation 3: R = radius, ρ = density, Q = flow rate, VT= tangential fluid velocity (Hinchey, Fluid Machinery)

Equation 3: !!!!"# = !"#!! !" − !"#!! !"# Figure 10 above shows the velocity vectors of flow on a turbine blade. The respective tangential components of the inlet and outlet streams can be calculated by using equations 4 and 5 below. Where VN is the normal component of flow velocity and VB is the speed of the turbine blade. (Hinchey, Fluid Machinery)

Equation 4: !":!!! = !!!!"#$ Equation 5: !"#:!! = !!!!"#$ + !!!


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3.0 Concept Selection The generation of possible concepts to address the challenge of designing a downhole power assembly was approached from a perspective to utilize existing solutions wherever possible. The concepts presented below are for the power turbine section only. That is, the section of the turbine that converts fluid energy into a rotational mechanical output. This section of the turbine is the most crucial with respect to ensuring project constraints are met. All other components will be selected and/or designed during the preliminary design and detailed design stages. The concepts below were selected based upon background research that was conducted and is summarized in Section 2.0 above. Next, these concepts were scored based upon weighted criteria, which are described in Table 2 below.

Table&2:&Turbine&Concepts&

Concepts 1 Reversed Centrifugal Pump 2 Reversed Axial Pump 3 Compressor 4 Turgo Turbine 5 Pelton 6 Francis 7 Kaplan

Table&3:&Design&Selection&Criteria&

Criteria Weight (%) Description Size Compatibility 30 The downhole tool must have a maximum

outer diameter of 6.0” and length of 6.0’ Flow Direction 15 The turbine power section should provide axial

flow through the tool to minimize friction and pressure losses

Efficiency/Stage 10 The turbine power section should be selected to maximize the tool’s efficiency

Operational Conditions 5 The downhole assembly must be able to operate under high flow rates and low head

Fluid Rheology 5 The downhole assembly must be able to operate with drill cuttings in a water-based fluid system

Industrial Application 10 The selected concept should have sufficient relevant previous industrial application

Modular Flexibility 20 The turbine power section must allow for the modular implementation of multiple turbine assemblies in series within the drill string

Maintenance & Reliability

5 The turbine power section should be selected to ensure a reliable tool and to allow for easy maintenance work


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Table 4 below displays the detailed results of the concept scoring process.

The Kaplan turbine was selected based upon background research and the scoring process shown above. The use of a Kaplan turbine in the power section of the downhole turbine assembly proves to be the best option to address this challenge. The table below provides further justification for this selection.

Table&4:&Kaplan&Turbine&criteria&justification&

Criteria Description Size Compatibility Kaplan turbines are readily available in the market to

fit within a 6.0” downhole tool. In addition, simplified models can be manufactured for prototyping and testing purposes

Flow Direction Kaplan turbines require axial flow, which reduces frictional and pressure losses as compared to radial flow devices

Efficiency/Stage Kaplan turbines are classified as a reaction turbine, which in general are more efficient than impulse turbines for a given size.

Operational Conditions Kaplan turbines are used in applications with high flow rate and low head, which is ideal for drilling operations

Fluid Rheology Kaplan turbines have a large flow area that allow the passage of contaminants or particles in the fluid to pass without excessive damage

Industrial Application Kaplan turbines are used is many axial flow devices in a broad range of industries. There is plenty of information available on these devices.

Modular Flexibility The rotor of a Kaplan turbine allows for the multiple staging of the turbine. In addition, it is an axial flow device, which encourages modular flexibility.

Maintenance & Reliability

Kaplan turbines are reliable flow devices because they can allow the passage of solids within the flow. In addition, their simple staged design allows for easy tool maintenance.


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4.0 Conclusion The team considered seven different alternatives to decide the concept that fits the project constraints and requirements. After, an in-depth background research was done to evaluate each concept based on a particular set of criterion. These concepts were then evaluated during concept scoring session described in Section 3.0. The concept scoring session was concluded with decision of using Kaplan Turbines as the power unit for a preliminary design phase. The availability of smaller sized Kaplan turbines along with its capability to provide desired output while maintaining the axial flow of the working fluid makes it an appropriate choice for the project. The second best alternative is to reverse the working of axial flow pumps to meet the project requirements. As explained in Section 2.1.3, there are axial downhole pumps in market that uses Kaplan wheel to provide energy to the fluid. These pumps have spacing between the blades that allows fluid with containments and other solid materials to flow through them without any obstruction. The spacing between the blades also provides ease of maintenance. However, reversing the working of a pump to be used as turbine, leads to low overall turbine efficiency. Using the Kaplan turbines as a power generating unit, the team drafted a conceptual design of the tool. Appendix A shows the SolidWorks model of the conceptual design of downhole turbine unit. The size, location and configuration of components are decided to meet preliminary project constraints. The next phase of the project will conduct an in-depth evaluation of individual parts and components to optimize the system to fulfill the project requirements.

5.0 Recommendation 5.1 Compatibility Tool During the preliminary design phase the team was approached by the Advanced Drilling Group to provide a mechanism that will dampen the vibrations of the turbine tool while it is operating downhole. From initial discussions with the ADG Group, the team analyzed the possibility of placing springs and dampers close to turbine units to minimize vibrations. However, more research and detailed analyses needs to be done to addresses the over design requirements. Thus this will be highlighted in the next phase of the project.

5.2 Pressure Relief Valve The use of Pressure Relief Valve is recommended to divert the flow in case of a pressure build up. The stalling of the turbine during operation can lead to a significant pressure build up. This build up can cause serious damage to turbine blades and other components. This pressure relief valve will be activated once the pressure in the tool reaches a threshold limit. This will allow the fluid to bypass the turbine stages without damaging the components.


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5.3 Gearbox To achieve the output rotational speed of greater than 600 RPM, the tool will require a set of gearbox. From the initial background research team found the harmonic transmission system (see Appendix B for more detail) is the best alternative that meets the project’s sizing and power requirement constraints. The design parameters of the gearbox will be evaluated and analyzed in the next phase of the project.

5.4 Bearings The selection of bearings to support the main drive shaft within the turbine is an important consideration for this project. Thus far, research has been conducted regarding the types of bearings that are best suited for this downhole application and also to determine the products that are available in the market. A summary of the research that has been completed can be found in Appendix C.

5.5 Housing The housing of the downhole turbine assembly is the enclosure in which all other components will be contained. The housing will be designed to be compatible with standard drill pipe connections within the industry and will be designed to have a strength greater than the drill pipe for which it is connected. A summary of the research that has been completed can be found in Appendix D.

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6.0 References "Axial!Flow!Pumps"!Working!of!Axial!Flow!Pumps.!N.p.,!n.d.!Web.!27!Jan.!2014.!http://nuclearpowertraining.tpub.com/h1018v1/css/h1018v1_99.htm!!"Ball Bearings." SFK. N.p., n.d. Web. 10 Jan. 2014. <http://www.skf.com/ca/en/products/bearings-units-housings/ball-bearings/index.html>.!!Budynas, Richard G., J. Keith. Nisbett, and Joseph Edward. Shigley. Shigley's Mechanical Engineering Design. New York: McGraw-Hill, 2011. Print. !Delucia, F. V., and R. P. Herbert. "4. PDM vs. Turbodrill: A Drilling Comparision." PDM vs. Turbodrill: A Drilling Comparison. N.p., n.d. Web. 20 Jan. 2014. <https://www.onepetro.org/conference-paper/SPE-13026-MS>.

"Fluid Machinery." Fluid Machinery. N.p., n.d. Web. 13 Jan. 2014. <http://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/machine/chapter_7/7_1.html>. Fox, Robert W., and Alan T. McDonald. "10: Fluid Machinery." Introduction to Fluid Mechanics. New York: Wiley, 1985. 514-613. Print.

Hinchey, Michael. "Fluid Power Machines." Fluid Mechanics II. MUN Engineering, n.d. Web. <http://www.engr.mun.ca/~hinch/6961/NOTES>. "Hydropower." Pelton Turbine Manufacturers. N.p., n.d. Web. 15 Jan. 2014. <http://www.gilkes.com/Pelton-Turbines>. Inglis, T. A. Directional Drilling, Petroleum Engineering and Development Studies Volume 2. N.p.: n.p., n.d. 63-77. Print.

"Kaplan Turbines." Renewables First. N.p., n.d. Web. 14 Jan. 2014. <http://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/machine/chapter_7/7_1.html>.

!"Kaplan Turbine Working and Design." YouTube. YouTube, 02 May 2013. Web. 15 Jan. 2014. <http://www.youtube.com/watch?v=0p03UTgpnDU>. "Manual on Pumps Used as Turbines." Fluid Machinery. N.p., n.d. Web. 05 Feb. 2014. <http://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/machine/chapter_7/7_1.html>. NOV Drilling Products and Services. Rep. NOV, n.d. Web. 22 Jan. 2014. <http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=tool%20joint>.


!18!

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"Positive Displacement Motors." SLB Oilfield Glossary. Schlumberger, n.d. Web. 22 Jan. 2014. <http://www.glossary.oilfield.slb.com/en/Terms/p/positive_displacement_motor.aspx>. Specification for Drill Pipe. Rep. no. ISO 11961:2008. ANSI/API SPECIFICATION 5DP, n.d. Web. 24 Jan. 2014. <http://ussbearings.com/bearings_site/products_article/24/>. Taylor,!Drew.!"Working!of!Turbine!Pump!Units."!Telephone!interview.!20!Jan.!2014.!!"Tilting Pad Thrust Bearings & Fixed Pad Hydrodynamic Thrust Bearing." Tilting Pad Thrust Bearings & Fixed Pad Hydrodynamic Thrust Bearing. N.p., n.d. Web. 25 Jan. 2014. <http://www.kingsbury.com/thrust_bearings.shtml>. "Tool Joint." - Schlumberger Oilfield Glossary. N.p., n.d. Web. 23 Jan. 2014. <http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=tool%20joint>. "Turgo Turbine." Wikipedia. Wikimedia Foundation, 20 Dec. 2013. Web. 12 Jan. 2014. <http://en.wikipedia.org/wiki/Turgo_turbine>. "TrimLine!4"!Submersible!Pumps."!TrimLine!4"!Submersible!Pumps.!N.p.,!n.d.!Web.!27!Jan.!2014.!http://www.berkeleypumps.com/ResidentialProduct_Series_MGS.aspx!!"US Synthetic Bearings Site." Radial Bearing. N.p., n.d. Web. 23 Jan. 2014. <http://ussbearings.com/bearings_site/products_article/24/>.!

Works, Madden T. Turbodrill. Madden T Works, Joseph A Mitchell, Mooney John Russell, assignee. Patent 2,990,895. 20 Oct. 1958. Print. "Working of Francis Turbine." YouTube. YouTube, 24 July 2013. Web. 15 Jan. 2014. <http://www.youtube.com/watch?v=3BCiFeykRzo>. "6T!Subturbine!Series."!6T#Subturbine#Series.!N.p.,!n.d.!Web.!28!Jan.!2014.!<http://www.berkeleypumps.com/ResidentialProduct_Series_6T_Subturbine.aspx>!!

!!!!!


A1!!

!!!!!!!!!!!!!!!!!

!APPENDIX A: SOLIDWORKS

DRAWING

ITEM NO. Description QTY.

1 Housing 1

2 Seating for Bearing 1

3 Shaft 1 14 Ball Bearing 2 1

5 Seating 2 for Bearing 1

6 Ball Bearing 1 1

7 Shaft 2 1

8 Gear Box 1

9 Rotor/Stator 6

APPV'D

CHK'D

DRAWN

D

E

F

C

1 2 3 4

B

A

321 5

C

D

4 6 7 8

A

B

Downhole Turbine Tool02-FEB-14LL

WEIGHT:

A3

SHEET 1 OF 1SCALE:1:5

DWG NO.

TITLE:

REVISIONDO NOT SCALE DRAWING

MATERIAL:

DATE

MFG

Q.A

NAME

DEBUR AND BREAK SHARP

SIGNATURE

ANGULAR:

FINISH:

EDGES

UNLESS OTHERWISE SPECIFIED:DIMENSIONS ARE IN MILLIMETERSSURFACE FINISH:TOLERANCES: LINEAR:

Assembly001

67 81

4

2 3

5

9

60.00

3.5


B1!!

APPENDIX B: GEARBOX &

TRANSMISSION RESEARCH


!B2!

!

Planetary Gear System Planetary Gear Systems are gear trains that allow transfer of motion between two non parallel – non intersecting shafts. Typical planetary gear system includes following components:

a. One Sun Gear: Gear located at the centre of the assembly b. One or more planet gears: Same sized gears that are meshed with sun gear and

ring gear c. Ring gear: Ring with inward facing teeth that meshes with planet gears d. Carrier: Connects sun gear to planet gears

(http://hades.mech.northwestern.edu/index.php/Gears)

Depending on the speed-torque requirements the input and output gears are selected. In most cases one of the gear types is held stationary and other two types are rotated to achieve desired gear ratios. Table x below shows some key relations between input-output gear, teeth numbers, and gear ratios. Here R and S represents teeth number (or diameter) of ring and sun gear respectively. (http://science.howstuffworks.com/transport/engines-equipment/gear7.htm)

Input Output Stationary Gear Ratio Sun Planet Carrier Ring 1+R/S

Planet Carrier Ring Sun 1/(1+S/R) Sun Ring Planet Carrier -R/S


!B3!

!

Harmonic Transmission Harmonic transmission is a type of planetary gear system that provides higher gear ratios, higher torque transfer capabilities compactness, and minimum backlash. This type of transmission is best for transmitting power between co-axially aligned input and output shafts. A typical harmonic gear transmission includes three major components (as illustrated in the figure below):

a. Wave Generator: It is a specially designed ball-bearing that is distorted into an ellipse. Input shaft is usually connected to a wave generator.

b. Flex Spline: It is a thin-walled flexible cup with gear teeth cut on the outside diameter. The wave generator is placed inside this flexible spline and it takes an elliptical shape.

c. Circular Spline: It is a rigid ring with teeth cut internally. Circular spline usually has two more teeth then flex spline and it connected to output shaft.

Applications: In the design of the downhole turbine, a harmonic drive transmission can be used to achieve desired output torque and speed. The current conceptual design includes a harmonic transmission gear system connecting drive shaft of turbine with input wave generator and an output shaft with output circular spline. (http://www.gearproductnews.com/issues/0406/gpn.pdf Pg 33)


C1!!

APPENDIX C: BEARING RESEARCH


!C2!

!

Bearings Bearings are used in many mechanical devices with the purpose of reducing friction between components, such as between a drive shaft and supporting joints. Through the use of bearings, the drive shaft can rotate freely with little energy dissipated due to frictional losses. Ultimately, bearings increase the efficiency of power transmission through a supported drive shaft assembly by decreasing the coefficient of friction at select shaft supporting joints. To determine the bearings that are best suited for a downhole turbine application, there are several initial considerations that must be taken into account. First, the bearing must be selected to fit within the confined space of the tool housing. In addition, the bearing must be able to withstand the expected load conditions for the application. Lastly, the bearing must have a satisfactory life under the specified conditions. (Shigley, 570) There are multiple types of bearings available to choose from for use with rotating shaft applications. However, to address the specific design requirements of a downhole turbine assembly outlined in Section 1.0, there are 3 main bearing types that are worth further consideration. These include rolling-contact (ball and roller bearings), hydrodynamic, and sliding bearings. 1. Rolling-Contact Bearings Rolling-contact bearings can be further subdivided into two classes: ball and roller bearings. In general, ball bearings are used in applications with high speeds, low loads, and small diameter shafts. While, roller bearings are best used for applications with large radial loads and shafts with large diameters. However, both bearings can be used in applications that require high-speed, combined (axial and thrust) loading, and high precision. Many applications employ a combination of ball and roller bearings to gain the added advantages of both bearing types. Rolling-contact bearings are readily available in the market for the range of shaft diameters required for this application. (SFK) 2. Hydrodynamic Bearings Hydrodynamic bearings operate on the theory of using a thin layer of viscous fluid to separate rotating surfaces to greatly reduce the coefficient of friction. Hydrodynamic bearings are available in both thrust and journal configurations. Therefore, for combined loading applications, both a thrust and journal bearing must be used to resist axial and radial loads. In addition, to provide proper lubrication to the bearings, oil must be supplied through small channels in the bearing in a sealed environment. Lastly, hydrodynamic thrust and journal bearings are available in the market for the range of shaft diameters required for this application. (Kingsbury Inc.) 3. Sliding Bearings Sliding bearings work under the same principal as hydrodynamics bearings through the use of a viscous fluid to separate rotating surfaces. The main difference between the two is that sliding bearings often contain circular polycrystalline diamond (PDC) pads rather than continuous sliding surface like hydrodynamic bearings. PDC bearings have the ability to operate in high-speed, corrosive, high-loading applications and can be lubricated through the use of surrounding fluid such as drilling mud. Lastly, PDC bearings are available in the market to be manufactured for custom applications and can resist both axial and radial loads. (US Synthetic Bearings)


D1!!

APPENDIX D: HOUSING RESEARCH


D2!!

Housing

The outer case or housing of the tool generally contains two major pieces of hallow cylindrical pipes with multiple shoulders inside. One piece hosts the turbine section and the other piece supports the bearing section. Since the housing is directly connected to drill pipes, API Specification 5 DP (Specification for Drill Pipe) is used as a guide to design and evaluate the housing. Discussion of the housing body and tool joints is conducted below to indicate the requirements in design, manufacture, inspection, etc. Housing Body

The requirements for drill-pipe body in API 5 DP are used to initiate the housing body design. Since the maximum outer diameter for the tool is restricted to 6 in. Study of the API specification is only on 6 in below. Based on the availabilities in the specification, options for outer diameters are limited to 2-7/8 in, 3-1/2 in, 4 in, 4-1/2 in, 5 in, and 5-1/2 in. Each size has 4 grades available: Grade E, X, G, and S in which X, G, and S are high-strength grades. Since the housing will be exposed to the downhole torque and compression, the high-strength grades hold a more favorable edge. Detailed size options can be found in Appendix A (P90-93 in API 5 DP). Multiple shoulders inside the housing body are required to provide support to the various components in the turbine section and bearing section. (Specification for Drill Pipe) Tool Joints

The connection between the housing and the adjacent drill pipe is performed by tool joints which are threaded ends of drill pipes. Tool joints are manufactured separately from the body and then welded onto the pipe. (Tool Joint, SLB) The dimensions and properties of tool joints vary based on the size of the pipe body, grade, upset type and connection type. (NOV Drilling Products and Services) Multiple options are available for pipe body and tool joints from the API specification and even more options can be provided by different suppliers, so the selection and modification will be established through detailed calculations in the next phase of the project.


E1

APPENDIX E: BERKELEY VERTICAL SUBMERSIBLE PUMP


E2


E3

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