Final Report Summary - ADEPT (High Efficiency Fuel Pumping)
Executive Summary:
The development of this high efficiency fuel pump will ultimately deliver higher efficiency and lower emissions part of the Cleansky key objective. With the likely smaller engine core in combination with evolving engine architectures and advanced cycles, there will be a trend for increased heat rejection into fuel. The design and material choices deployed in this technology project have started to demonstrate
The project aimed to develop and demonstrate a high efficiency fuel pump that will support engine technologies that deliver higher efficiency and lower emissions, helping to reduce the environmental impact of aviation. With the likely smaller engine core in combination with evolving engine architectures and advanced cycles, there will be a trend for increased heat rejection into fuel. The fuel pump proposed in this project will feature novel component technologies that will minimise the heating of the fuel from the engine control system. This in turn will assist in minimising any additional engine heat exchanger equipment, thereby reducing engine drag and weight. This will have a direct contribution to reductions in fuel consumption and emissions.
The global market for engines required for regional and large civil aircraft from 2016 onwards is of the order of 3,000 per year. This equates to a potential market of 3000 fuel pumps per year, sustaining operational capacity for around 400 skilled employees per annum. Additionally, this will support a much larger supply chain base. Although this project directly impacts on specialist suppliers, the wider impact in terms of engine sales will have an impact many times more significant than the direct impact alone.
Project Context and Objectives:
Overall Objective
The concept of this project is the TRL 6 demonstration of a high speed, light weight, large capacity variable displacement piston pump for medium and large aero-engine fuel system applications.
Piston pumps currently find application on the fuel systems of small and medium engines. This project aims to build on AEC’s pedigree and inherent high reliability in this market while addressing the speed limitations of the current piston pumps. By increasing the maximum speed capability the large flow output can be achieved with a smaller displacement pump. Higher speed requires a greatly increased duty, a term used to compare the relative levels of stress and velocities of the pumping elements. This higher duty performance will be achieved through application of modern materials, coatings, manufacturing technologies and advanced analysis methods. The pump shall be designed to retain the current high mean time before failure.
The project is split into eight work packages, with the overall aim being to design and manufacture a variety of options for the high duty pump’s internal components to be tested within a flexible demonstrator vehicle. The optimum combination will then be identified and subjected to further testing to demonstrate TRL6, resulting in a final design proposal for a large engine application.
AEC has in-house pump design, manufacture and performance and environmental test capability. However, this technology programme will require external capabilities relating to specific design and manufacturing processes and capabilities, and materials technology. Therefore, the overall strategy is for AEC to integrate the research establishments and the SMEs’ capabilities to design, make and evaluate the key component technologies.
Concept Rationale
There are two fundamental pumping types, namely roto-dynamic and displacement. Roto-dynamic pumping solutions have been ruled out, primarily because across such a wide range of fuel flow and pump speed, these devices are inherently not as efficient as a displacement type. Fixed displacement pumps, as currently in use on commercial large commercial aero-engines, require the fuel to be re-circulated during the majority of the flight envelope, resulting in an undesirable increase in fuel temperature. Variable displacement pumping is a key solution to effective thermal management of the fuel system since it enables the output of the pump to be precisely matched to the fuel required by the engine, and removes the necessity for high pressure fuel flow recirculation, thereby reducing the heat rejected to the fuel.
The concept is to re-design key features of the existing low duty, axial piston pump to demonstrate a high duty capability for a medium-large commercial aero-engine. Piston pumps are one type of variable displacement pump. Aero Engine Controls1 (AEC) has designed, manufactured and tested low duty piston pumps since the 1940’s. Such pumps have accumulated over 300 million flying hours on small and medium engines, and have achieved reliability levels of 300,000 hours mean time between failure (MTBF). Attempts in the 1950’s and 1960’s to increase the duty of these piston pumps to meet the increasing demands of medium-large turbo-fans, and to make the piston pump competitive with fixed displacement alternatives, were not successful. This was partly due to limitations of the then-available materials, processes and analytical techniques. In addition, the issues associated with the thermal management of fuel were not so great, so the customer did not require the added complexity of the variable displacement function.
The technical challenge of this Project is to build on Aero Engine Controls’ pedigree and inherent high reliability while addressing the speed limitations of the current piston pumps. By increasing the maximum speed capability, the output of the pump can be achieved with a smaller displacement pump. This is necessary to meet the required mass target but will require a greatly increased duty. This will be achieved through application of modern materials, coatings, manufacturing technologies and advanced analysis methods to produce low inertia, wear resistant parts. (For displacement pumps, the term “duty” is used to compare the relative levels of stress and velocities of the pumping elements, such that a higher duty implies higher stresses and velocities.)
The technical challenge is to demonstrate a high duty, increased service life axial piston pump, whilst retaining the inherent reliability of today’s low duty technology.
Technical Objectives
The technical objectives are:
1) Development of mathematical analyses to calculate the performance (e.g. loadings, speeds, dynamics, lubrication) of the pumping components in current inservice pump designs, followed by validation of these mathematical analyses via test.
2) Assessment via analysis and test of current pump designs to identify the lifelimiting design features/components at the higher duty and longer life requirements
3) Application of the validated analyses to create a parametric design model for thenew high duty pump whose constraints are based on improving the life-limiting features as well as optimising for size and weight.
4) Use of the predicted performance duties of the new components to allow selection of modern materials and coatings, optimised for the specific duty of the part. This will involve material sample and component level testing, sub-contracted and inhouse.
5) Investigation into engineering ceramic materials and novel coatings to benefit from their low mass and low wear properties.
6) Design of a flexible demonstrator pump housing as a test vehicle for different designs and material options of internal components for the high duty pump
7) Design of components for the high duty pump, to be manufactured by SME prototype specialists
8) Development of novel manufacturing and assembly methods, using the expertise of various Institutes
9) Test programme to be performed on new component designs to assess pump performance and the material performance. This will be complemented by laboratory analysis of the parts.
10) Selection of the best combination of pump internal components and then further testing to demonstrate performance up to TRL6.
11) To demonstrate a route to meeting the SAGE03-003 requirements.
Progress beyond the state-of-the-art
Piston pumps currently find application on the fuel systems of small and medium engines. To provide a variable displacement piston pump for large engines a significant increase in the duty is necessary as the pump will be required to run at high speeds in order to reduce size and weight. This project aims to demonstrate a pump capable of operating at this duty.
Current State of Pumping Technology
Patent and public domain literature searches have been performed, and are periodically up-dated. Although there is still development activity on hydraulic (as opposed to fueldraulic) piston pumps, there is no evidence of work on such high duty pump technology, implying that this proposal represents a significant step from the state of the art. Alternative approaches such as the variable displacement vane pumps have received much investment aimed at developing a design suitable for the medium to large engine market, but a robust model is yet to be proven. The bearing dynamics for the larger displacement vane pump are complex, and when solved, introduce significant complexity and associated issues with weight and cost. The proposed solution of a high duty variable displacement piston pump will be superior in terms of weight and cost for the medium and large engine market.
Proposed Technology
The pump shall be designed to retain the inherent reliability of today’s smaller capacity piston pumps. By designing out or reducing the rate of wear, through appropriate understanding of the dynamics and associated stresses, and the use of advanced materials and coatings, the proposed pump will have increased overhaul life.
Lubrication Considerations
Industrial piston pumps typically operate at lower speeds and duties, using oil as a lubricant. Oil is not available to the moving parts of the aero-engine fuel pump. The significantly lower lubricity of aviation fuel presents a challenge to the running surfaces within the piston pump. This must be addressed within the design by appropriate load distribution and material selection to ensure suitable surface friction and resistance to wear. This project aims to demonstrate a robust design and materials solution to address the high duty operation Lubrication analysis of sliding surfaces will be developed to predict performance for varying fuel lubricity.
Material and Process Selection
The application of modern materials, coatings and processes is key to the development of this fuel pump. Significant investment will be made in material testing with emphasis on high wear resistance and low friction surfaces. Material choices will be based on providing a low weight pump, whilst ensuring acceptable whole-life costs and compliance to REACH legislation.
Overall strategy and general description
The aim within the project timeframe is to design and manufacture a variety of options for the high duty pump’s internal components to be tested within a flexible demonstrator vehicle. The optimum combination will then be identified and subjected to further testing to demonstrate TRL6. Mathematical analysis of piston pumps and materials testing will be performed prior to the design and manufacture phase. The outputs will be validated design and material selection guidelines for large piston pumps, and a final design solution for a large engine application. Aero Engine Controls’ has in-house pump design, manufacture and performance and environmental test capability. However, this technology programme will require tasks to be sub-contracted to organisations with external capabilities relating to specific design and manufacturing processes and capabilities. Therefore, the overall strategy is for Aero Engine Controls to integrate the research establishments and the SMEs’ capabilities to design, make and evaluate the key component technologies that will enable the pump to operate at such elevated levels of duty.
Project Results:
Key Reports
The following key reports, which are deliverables in the project, have been issued:-
NUMBER TITLE ISSUE
JTT110/0017 Next Generation High Speed Piston Pump Specification - Future Large Engine 2
JTT100/0110 Kinematic analysis of a piston pump 3
JTT100/0149 Summary of the Recent Development of Piston Pump Technology 2
JTT100/0204 Summary of the Recent Testing of Piston Pump Technology 1
JTT100/0211 Summary of the Recent Testing of Piston Pump Technology 1
JTT100/0227 Flexible Demonstrator Piston Pump Design Review 2
JTT100/0238 Materials Testing utilising GD502 Pumps to evaluate materials for high speed piston pump 1
JTT100/0294 Flexible Demonstrator Piston Pump Test Strategy 2
JTT100/0253 Test Procedure for Flexible Demonstrator Piston Pump 1
JTT100/0322 Initial test results for Flexible Demonstrator Piston Pump 1
JTT100/0327 Test Results for the Flexible Demonstrator Piston Pump 1
Presentations
Presentations given during the project give an overview of the work and are were provided to the Topic Manager’s Representative during the project.
AEC established a monthly Pumps Steering Group as a technical discussion forum, so the presentations contain technical information and special topics. The monthly AdEPT reviews presented progress within the workpackages of the AdEPT programme.
Project Personnel
The following people were involved at some time during the project:-
• Project Coordinator: Greg Wells
• Project manager: John Macarthur
• Project technical lead: Catherine Todd
• Designers: Blair Ramsay, Andy Syska, Ray Johnston
• Project engineers: Simon Turner, Paul Fryer, Dan Waters
• Materials Laboratory: Terry Hirst, Andy Lewington, Hannah Davies, Heather Wilson, Melissa Leung
• Design Analysis: Martin Yates, David Neate, Jeremy Heald
• Sourcing: Ian Darby
Legacy pistons pumps
AEC has a long history of piston pumps for aircraft engine, marine engine and industrial applications. A comprehensive summary of piston pump development since the original design by Dick Ifield in the 1940s is available within AEC.
The capacity of the pistons pumps is indicated by letter A to D with A being the smallest. They are scaled designs based on displacement. Various applications have seen these types of pumps.
Research & investigations
A large number of journal papers pertaining to different aspects of piston pump design and analysis have been obtained. Electronic copies are available from AEC.
External research - A report was commissioned from Prof John Watton, Emeritus Professor of Fluid Power at Cardiff University, “A Review of Axial Piston Pumps”. The first part (“Published works and patents related to design”) covers state of the art information on pistons pumps and specific aspects of their design. Part 2 (“Modelling techniques and measured data”) covers methods for mathematical analysis of different elements of an axial piston pump.
Research into legacy designs - Much development engineering occurred during the 1950s and 1960s but few reports exist which explain why particular features were so designed. A number of design schemes of previous pumps were looked at in an attempt to understand the development of the key components within the Lucas piston pumps. Despite all this research it was not possible to draw many conclusions from the records so some ideas have been trialled within this project which have been tried before.
Investigation of hardware
Overhaul and life assessment reports from in-service pumps were reviewed for a range of pumps to identify the components which exhibit high wear and assess measurements. This was reported in an internal report JTT100/0135.
A large number of parts scrapped on overhaul were looked at to determine the wear mechanisms. The Materials Laboratory performed materials analysis on these parts, recorded in CM17551.
Significant design drivers
During the early stages of testing, research and investigations several aspects of piston pump design were identified as requiring improvement when embodied in the high speed piston pump design. The approach was to trial new designs and materials in D-size pumps, to later implement the best options within the high speed piston pump. These aspects are listed here as a context for the following sections which give more detail on materials, designs and hardware.
Addressing Speed-limitation
The project addressed speed limitations and the output is contained in the project reports.
Addressing Life-limitation
One key life-limiting aspect of the legacy designs is wear which is described in the project reports. This has led to new designs, materials and testing.
Addressing weight
It is desirable to reduce the weight and the parts count of the pump due to airframe and engine life costs. This has led to re-design of the rotor assembly, using alternative materials.
New D-size pump designs & hardware
Over 100 new parts to fit into D-size pumps were designed and made, to address speed- or life-limitations of the current design or for investigations.
Design workshops were held to look at improvements to the designs of several components and reported in the project reports.
Pumps A-D
A number of parts of existing design were made with from new materials in order to test the running couples. These were tested but insufficient hours were accrued (see JTT100/238).
Testing of pumps
Testing totalled over 4500 hours. There was also significant analysis of failed components and witness filter debris carried out throughout the project by the Material Laboratory staff, reported as MERs.
Special test equipment
A double headed gearbox was procured in order to run two D-size pumps on one rig drivehead.
Piston & Slipper test rig
A bespoke rig was made for testing the wear. Originally intended to simulate the motion within a pump, this was too complex for a bench top rig. The rig allows comparative testing of components. It is located in the Mechanical Wear laboratory and is described in report JTT100/0229; the test procedure and results are described in CM17607.
Analysis
MathCAD models
The key models are briefly discussed below. Further models have been created for interest. They are all held in the “Analysis & research” folder.
Kinematic analysis
At the start of the project a kinematic model was developed for the D-size piston pump.
Axial balance
An axial balance model has been written for the D-size pump to calculate the summation of static forces acting on the rotor for any given operating conditions.
The dynamic analysis is performed using the CCLM, using the forces and moments calculated within the static axial balance model. A guideline has been written containing a methodology for calculating these forces and moments acting on the rotor, AG-EP-MDVPP01. This methodology has been included within the Flexible Demonstrator piston pump kinematic model.
Lubrication models
The pumps team within Design Analysis has developed a common core lubrication model (CCLM) written in Fortran.
Thermal models
One of the AdEPT project deliverables was to provide assessment of the thermal performance of the piston pump in comparison with the gear pump. Two approaches were used: firstly mathematical analysis based on the power consumption and mechanical losses; secondly a finite element model. Both models require further validation from test data. They are reported in JTT100/428.
Model validation and performance analysis – D-size
The data from the D-size pump testing was analysed for a number of different aspects. This included comparison with predictions made by mathematical models. All the worksheets and relevant test data is stored within AEC’s network.
Guidelines & design rules
A Piston Pump Design Guideline (AG-EP-MDVPP) was written in 2011 with the intention of updating it as more is learnt about the pump operation and the key design features of the components.
It is intended to create a set of validated design rules for the piston pump based on analysis, which could be merged with the Guideline.
During the design phase a document “Design Log” was written to record the design decisions. A Design Review was held and is reported in JTT100/227 issue 2.
A number of assembly tools and fixtures were also designed and given ENGT numbers. A comprehensive Assembly Instruction Sheet has been written, AIS1253A issue 2. This contains a list of the tools and fixtures, fittings and connectors.
Each build of a pump is given a serial number and has an accompanying Build Record Sheet (AIS1253B). The serial number is printed on a mod plate and bolted onto the housing. The Build Record Sheet is updated on every strip examination and rebuild of the pump to record the condition of the components and any changes.
Rotor assembly
This is a complex design involving a significant number of manufacturing operations. Assembly problems on the first variant led to a long investigation of the factors involved in a successful assembly. This is captured in report JTT100/339.
Housings
The pump body comprises two housings. Three complete bodies have been procured.
Design workshop
A workshop was held on 11th October 2012 to generate new ideas to answer five questions. The ideas were collated but have not yet been ranked to enable selection of the best options to take forward.
Pump testing
The overall test strategy for the piston pump is laid out in report JTT100/294 issue 2. This includes what is involved in demonstration of TRL6.
The Flexible Demonstrator first ran on a test rig in May 2011. Subsequent design assurance testing on a production rig was reported in JTT100/322. Full performance testing was planned and has been started. All testing so far undertaken is reported in JTT100/327. This includes a methodology for performance analysis.
Technical issues to be addressed & Lessons Learnt
Various technical issues were resolved and reported in the project documentation. Lessons learnt were also added to the lessons learnt database.
Potential Impact:
Conclusions
The project has determined the speed limitation of existing pumps, trialling 12 different types of pumps. 1700 hours of testing has been performed to determine effect on performance and component condition when running fast, and what parameters or parts can affect this. This has identified the limiting factors not known before.
Clear benefits developed in the project include:-
1) Modelling
Mathematical modelling has been utilised to design large pump to calculate loads at key interfaces such that the optimum loading can be obtained for the optimised geometry. The cause of high speed damage and how to prevent it by calculating loadings within mathematical kinematic model has been understood. New parametric model to design the large pump for optimum loadings at high speed have been developed.
Lubrication modelling of interface led to an improved design. The model provided understanding of instability, new design modelled then proved on test to improve high speed performance.
2) Lifing
The project has also determined the life limitations of existing pumps by investigating overhaul parts through endurance testing of pumps including hot and low lubricity fuel and materials laboratory investigation.
3) Design Guidelines
New designs for assembly have been created and developed welded design techniques on a bespoke rig. Through design workshops held with our specialists key components for attention for large pump design have been identified
4) Materials
New material combinations have been tested - 825 hours testing of new materials in pumps; lightweight rotor assembly designed for large pump and tested.
The project also saw a first for visualisation testing to show the motion of key components.
Specific testing of materials for components affected by high speed operation has been developed. Materials testing of several different options resulted in various options.
5) Testing
3 variety of pumps have been subjected to performance testing on the large pump
As a by-product the project also performed mechanical efficiency assessment - torque sensor allows measurement of power consumption; method of performance analysis to evaluate efficiencies established and started to understand causes of inefficiency. Mechanical losses were calculated – several contributors
6) Manufacturability
Designed a productionised version of the large piston pump and identified potential weight savings.
The project has demonstrated good supplier development for potential future manufacturing capability. Such items as for complex assemblies include processing, hand-offs, tolerance, surface finish and cost control
7) Wider societal implications
In terms of capability learning for our professional and future engineering staff, considerable research has been accomplished during this project including the analysis of 55 journals and 2 state of the art reports. Our materials laboratory have provided vital support, especially at the start looking into wear. Much of our assessment of pump performance is visual, or provided by microscopy, SEM analysis or surface interferometry.
The development of this high efficiency fuel pump will ultimately deliver higher efficiency and lower emissions part of the Cleansky key objective. With the likely smaller engine core in combination with evolving engine architectures and advanced cycles, there will be a trend for increased heat rejection into fuel. The design and material choices deployed in this technology project have started to demonstrate
The project aimed to develop and demonstrate a high efficiency fuel pump that will support engine technologies that deliver higher efficiency and lower emissions, helping to reduce the environmental impact of aviation. With the likely smaller engine core in combination with evolving engine architectures and advanced cycles, there will be a trend for increased heat rejection into fuel. The fuel pump proposed in this project will feature novel component technologies that will minimise the heating of the fuel from the engine control system. This in turn will assist in minimising any additional engine heat exchanger equipment, thereby reducing engine drag and weight. This will have a direct contribution to reductions in fuel consumption and emissions.
The global market for engines required for regional and large civil aircraft from 2016 onwards is of the order of 3,000 per year. This equates to a potential market of 3000 fuel pumps per year, sustaining operational capacity for around 400 skilled employees per annum. Additionally, this will support a much larger supply chain base. Although this project directly impacts on specialist suppliers, the wider impact in terms of engine sales will have an impact many times more significant than the direct impact alone.
Project Context and Objectives:
Overall Objective
The concept of this project is the TRL 6 demonstration of a high speed, light weight, large capacity variable displacement piston pump for medium and large aero-engine fuel system applications.
Piston pumps currently find application on the fuel systems of small and medium engines. This project aims to build on AEC’s pedigree and inherent high reliability in this market while addressing the speed limitations of the current piston pumps. By increasing the maximum speed capability the large flow output can be achieved with a smaller displacement pump. Higher speed requires a greatly increased duty, a term used to compare the relative levels of stress and velocities of the pumping elements. This higher duty performance will be achieved through application of modern materials, coatings, manufacturing technologies and advanced analysis methods. The pump shall be designed to retain the current high mean time before failure.
The project is split into eight work packages, with the overall aim being to design and manufacture a variety of options for the high duty pump’s internal components to be tested within a flexible demonstrator vehicle. The optimum combination will then be identified and subjected to further testing to demonstrate TRL6, resulting in a final design proposal for a large engine application.
AEC has in-house pump design, manufacture and performance and environmental test capability. However, this technology programme will require external capabilities relating to specific design and manufacturing processes and capabilities, and materials technology. Therefore, the overall strategy is for AEC to integrate the research establishments and the SMEs’ capabilities to design, make and evaluate the key component technologies.
Concept Rationale
There are two fundamental pumping types, namely roto-dynamic and displacement. Roto-dynamic pumping solutions have been ruled out, primarily because across such a wide range of fuel flow and pump speed, these devices are inherently not as efficient as a displacement type. Fixed displacement pumps, as currently in use on commercial large commercial aero-engines, require the fuel to be re-circulated during the majority of the flight envelope, resulting in an undesirable increase in fuel temperature. Variable displacement pumping is a key solution to effective thermal management of the fuel system since it enables the output of the pump to be precisely matched to the fuel required by the engine, and removes the necessity for high pressure fuel flow recirculation, thereby reducing the heat rejected to the fuel.
The concept is to re-design key features of the existing low duty, axial piston pump to demonstrate a high duty capability for a medium-large commercial aero-engine. Piston pumps are one type of variable displacement pump. Aero Engine Controls1 (AEC) has designed, manufactured and tested low duty piston pumps since the 1940’s. Such pumps have accumulated over 300 million flying hours on small and medium engines, and have achieved reliability levels of 300,000 hours mean time between failure (MTBF). Attempts in the 1950’s and 1960’s to increase the duty of these piston pumps to meet the increasing demands of medium-large turbo-fans, and to make the piston pump competitive with fixed displacement alternatives, were not successful. This was partly due to limitations of the then-available materials, processes and analytical techniques. In addition, the issues associated with the thermal management of fuel were not so great, so the customer did not require the added complexity of the variable displacement function.
The technical challenge of this Project is to build on Aero Engine Controls’ pedigree and inherent high reliability while addressing the speed limitations of the current piston pumps. By increasing the maximum speed capability, the output of the pump can be achieved with a smaller displacement pump. This is necessary to meet the required mass target but will require a greatly increased duty. This will be achieved through application of modern materials, coatings, manufacturing technologies and advanced analysis methods to produce low inertia, wear resistant parts. (For displacement pumps, the term “duty” is used to compare the relative levels of stress and velocities of the pumping elements, such that a higher duty implies higher stresses and velocities.)
The technical challenge is to demonstrate a high duty, increased service life axial piston pump, whilst retaining the inherent reliability of today’s low duty technology.
Technical Objectives
The technical objectives are:
1) Development of mathematical analyses to calculate the performance (e.g. loadings, speeds, dynamics, lubrication) of the pumping components in current inservice pump designs, followed by validation of these mathematical analyses via test.
2) Assessment via analysis and test of current pump designs to identify the lifelimiting design features/components at the higher duty and longer life requirements
3) Application of the validated analyses to create a parametric design model for thenew high duty pump whose constraints are based on improving the life-limiting features as well as optimising for size and weight.
4) Use of the predicted performance duties of the new components to allow selection of modern materials and coatings, optimised for the specific duty of the part. This will involve material sample and component level testing, sub-contracted and inhouse.
5) Investigation into engineering ceramic materials and novel coatings to benefit from their low mass and low wear properties.
6) Design of a flexible demonstrator pump housing as a test vehicle for different designs and material options of internal components for the high duty pump
7) Design of components for the high duty pump, to be manufactured by SME prototype specialists
8) Development of novel manufacturing and assembly methods, using the expertise of various Institutes
9) Test programme to be performed on new component designs to assess pump performance and the material performance. This will be complemented by laboratory analysis of the parts.
10) Selection of the best combination of pump internal components and then further testing to demonstrate performance up to TRL6.
11) To demonstrate a route to meeting the SAGE03-003 requirements.
Progress beyond the state-of-the-art
Piston pumps currently find application on the fuel systems of small and medium engines. To provide a variable displacement piston pump for large engines a significant increase in the duty is necessary as the pump will be required to run at high speeds in order to reduce size and weight. This project aims to demonstrate a pump capable of operating at this duty.
Current State of Pumping Technology
Patent and public domain literature searches have been performed, and are periodically up-dated. Although there is still development activity on hydraulic (as opposed to fueldraulic) piston pumps, there is no evidence of work on such high duty pump technology, implying that this proposal represents a significant step from the state of the art. Alternative approaches such as the variable displacement vane pumps have received much investment aimed at developing a design suitable for the medium to large engine market, but a robust model is yet to be proven. The bearing dynamics for the larger displacement vane pump are complex, and when solved, introduce significant complexity and associated issues with weight and cost. The proposed solution of a high duty variable displacement piston pump will be superior in terms of weight and cost for the medium and large engine market.
Proposed Technology
The pump shall be designed to retain the inherent reliability of today’s smaller capacity piston pumps. By designing out or reducing the rate of wear, through appropriate understanding of the dynamics and associated stresses, and the use of advanced materials and coatings, the proposed pump will have increased overhaul life.
Lubrication Considerations
Industrial piston pumps typically operate at lower speeds and duties, using oil as a lubricant. Oil is not available to the moving parts of the aero-engine fuel pump. The significantly lower lubricity of aviation fuel presents a challenge to the running surfaces within the piston pump. This must be addressed within the design by appropriate load distribution and material selection to ensure suitable surface friction and resistance to wear. This project aims to demonstrate a robust design and materials solution to address the high duty operation Lubrication analysis of sliding surfaces will be developed to predict performance for varying fuel lubricity.
Material and Process Selection
The application of modern materials, coatings and processes is key to the development of this fuel pump. Significant investment will be made in material testing with emphasis on high wear resistance and low friction surfaces. Material choices will be based on providing a low weight pump, whilst ensuring acceptable whole-life costs and compliance to REACH legislation.
Overall strategy and general description
The aim within the project timeframe is to design and manufacture a variety of options for the high duty pump’s internal components to be tested within a flexible demonstrator vehicle. The optimum combination will then be identified and subjected to further testing to demonstrate TRL6. Mathematical analysis of piston pumps and materials testing will be performed prior to the design and manufacture phase. The outputs will be validated design and material selection guidelines for large piston pumps, and a final design solution for a large engine application. Aero Engine Controls’ has in-house pump design, manufacture and performance and environmental test capability. However, this technology programme will require tasks to be sub-contracted to organisations with external capabilities relating to specific design and manufacturing processes and capabilities. Therefore, the overall strategy is for Aero Engine Controls to integrate the research establishments and the SMEs’ capabilities to design, make and evaluate the key component technologies that will enable the pump to operate at such elevated levels of duty.
Project Results:
Key Reports
The following key reports, which are deliverables in the project, have been issued:-
NUMBER TITLE ISSUE
JTT110/0017 Next Generation High Speed Piston Pump Specification - Future Large Engine 2
JTT100/0110 Kinematic analysis of a piston pump 3
JTT100/0149 Summary of the Recent Development of Piston Pump Technology 2
JTT100/0204 Summary of the Recent Testing of Piston Pump Technology 1
JTT100/0211 Summary of the Recent Testing of Piston Pump Technology 1
JTT100/0227 Flexible Demonstrator Piston Pump Design Review 2
JTT100/0238 Materials Testing utilising GD502 Pumps to evaluate materials for high speed piston pump 1
JTT100/0294 Flexible Demonstrator Piston Pump Test Strategy 2
JTT100/0253 Test Procedure for Flexible Demonstrator Piston Pump 1
JTT100/0322 Initial test results for Flexible Demonstrator Piston Pump 1
JTT100/0327 Test Results for the Flexible Demonstrator Piston Pump 1
Presentations
Presentations given during the project give an overview of the work and are were provided to the Topic Manager’s Representative during the project.
AEC established a monthly Pumps Steering Group as a technical discussion forum, so the presentations contain technical information and special topics. The monthly AdEPT reviews presented progress within the workpackages of the AdEPT programme.
Project Personnel
The following people were involved at some time during the project:-
• Project Coordinator: Greg Wells
• Project manager: John Macarthur
• Project technical lead: Catherine Todd
• Designers: Blair Ramsay, Andy Syska, Ray Johnston
• Project engineers: Simon Turner, Paul Fryer, Dan Waters
• Materials Laboratory: Terry Hirst, Andy Lewington, Hannah Davies, Heather Wilson, Melissa Leung
• Design Analysis: Martin Yates, David Neate, Jeremy Heald
• Sourcing: Ian Darby
Legacy pistons pumps
AEC has a long history of piston pumps for aircraft engine, marine engine and industrial applications. A comprehensive summary of piston pump development since the original design by Dick Ifield in the 1940s is available within AEC.
The capacity of the pistons pumps is indicated by letter A to D with A being the smallest. They are scaled designs based on displacement. Various applications have seen these types of pumps.
Research & investigations
A large number of journal papers pertaining to different aspects of piston pump design and analysis have been obtained. Electronic copies are available from AEC.
External research - A report was commissioned from Prof John Watton, Emeritus Professor of Fluid Power at Cardiff University, “A Review of Axial Piston Pumps”. The first part (“Published works and patents related to design”) covers state of the art information on pistons pumps and specific aspects of their design. Part 2 (“Modelling techniques and measured data”) covers methods for mathematical analysis of different elements of an axial piston pump.
Research into legacy designs - Much development engineering occurred during the 1950s and 1960s but few reports exist which explain why particular features were so designed. A number of design schemes of previous pumps were looked at in an attempt to understand the development of the key components within the Lucas piston pumps. Despite all this research it was not possible to draw many conclusions from the records so some ideas have been trialled within this project which have been tried before.
Investigation of hardware
Overhaul and life assessment reports from in-service pumps were reviewed for a range of pumps to identify the components which exhibit high wear and assess measurements. This was reported in an internal report JTT100/0135.
A large number of parts scrapped on overhaul were looked at to determine the wear mechanisms. The Materials Laboratory performed materials analysis on these parts, recorded in CM17551.
Significant design drivers
During the early stages of testing, research and investigations several aspects of piston pump design were identified as requiring improvement when embodied in the high speed piston pump design. The approach was to trial new designs and materials in D-size pumps, to later implement the best options within the high speed piston pump. These aspects are listed here as a context for the following sections which give more detail on materials, designs and hardware.
Addressing Speed-limitation
The project addressed speed limitations and the output is contained in the project reports.
Addressing Life-limitation
One key life-limiting aspect of the legacy designs is wear which is described in the project reports. This has led to new designs, materials and testing.
Addressing weight
It is desirable to reduce the weight and the parts count of the pump due to airframe and engine life costs. This has led to re-design of the rotor assembly, using alternative materials.
New D-size pump designs & hardware
Over 100 new parts to fit into D-size pumps were designed and made, to address speed- or life-limitations of the current design or for investigations.
Design workshops were held to look at improvements to the designs of several components and reported in the project reports.
Pumps A-D
A number of parts of existing design were made with from new materials in order to test the running couples. These were tested but insufficient hours were accrued (see JTT100/238).
Testing of pumps
Testing totalled over 4500 hours. There was also significant analysis of failed components and witness filter debris carried out throughout the project by the Material Laboratory staff, reported as MERs.
Special test equipment
A double headed gearbox was procured in order to run two D-size pumps on one rig drivehead.
Piston & Slipper test rig
A bespoke rig was made for testing the wear. Originally intended to simulate the motion within a pump, this was too complex for a bench top rig. The rig allows comparative testing of components. It is located in the Mechanical Wear laboratory and is described in report JTT100/0229; the test procedure and results are described in CM17607.
Analysis
MathCAD models
The key models are briefly discussed below. Further models have been created for interest. They are all held in the “Analysis & research” folder.
Kinematic analysis
At the start of the project a kinematic model was developed for the D-size piston pump.
Axial balance
An axial balance model has been written for the D-size pump to calculate the summation of static forces acting on the rotor for any given operating conditions.
The dynamic analysis is performed using the CCLM, using the forces and moments calculated within the static axial balance model. A guideline has been written containing a methodology for calculating these forces and moments acting on the rotor, AG-EP-MDVPP01. This methodology has been included within the Flexible Demonstrator piston pump kinematic model.
Lubrication models
The pumps team within Design Analysis has developed a common core lubrication model (CCLM) written in Fortran.
Thermal models
One of the AdEPT project deliverables was to provide assessment of the thermal performance of the piston pump in comparison with the gear pump. Two approaches were used: firstly mathematical analysis based on the power consumption and mechanical losses; secondly a finite element model. Both models require further validation from test data. They are reported in JTT100/428.
Model validation and performance analysis – D-size
The data from the D-size pump testing was analysed for a number of different aspects. This included comparison with predictions made by mathematical models. All the worksheets and relevant test data is stored within AEC’s network.
Guidelines & design rules
A Piston Pump Design Guideline (AG-EP-MDVPP) was written in 2011 with the intention of updating it as more is learnt about the pump operation and the key design features of the components.
It is intended to create a set of validated design rules for the piston pump based on analysis, which could be merged with the Guideline.
During the design phase a document “Design Log” was written to record the design decisions. A Design Review was held and is reported in JTT100/227 issue 2.
A number of assembly tools and fixtures were also designed and given ENGT numbers. A comprehensive Assembly Instruction Sheet has been written, AIS1253A issue 2. This contains a list of the tools and fixtures, fittings and connectors.
Each build of a pump is given a serial number and has an accompanying Build Record Sheet (AIS1253B). The serial number is printed on a mod plate and bolted onto the housing. The Build Record Sheet is updated on every strip examination and rebuild of the pump to record the condition of the components and any changes.
Rotor assembly
This is a complex design involving a significant number of manufacturing operations. Assembly problems on the first variant led to a long investigation of the factors involved in a successful assembly. This is captured in report JTT100/339.
Housings
The pump body comprises two housings. Three complete bodies have been procured.
Design workshop
A workshop was held on 11th October 2012 to generate new ideas to answer five questions. The ideas were collated but have not yet been ranked to enable selection of the best options to take forward.
Pump testing
The overall test strategy for the piston pump is laid out in report JTT100/294 issue 2. This includes what is involved in demonstration of TRL6.
The Flexible Demonstrator first ran on a test rig in May 2011. Subsequent design assurance testing on a production rig was reported in JTT100/322. Full performance testing was planned and has been started. All testing so far undertaken is reported in JTT100/327. This includes a methodology for performance analysis.
Technical issues to be addressed & Lessons Learnt
Various technical issues were resolved and reported in the project documentation. Lessons learnt were also added to the lessons learnt database.
Potential Impact:
Conclusions
The project has determined the speed limitation of existing pumps, trialling 12 different types of pumps. 1700 hours of testing has been performed to determine effect on performance and component condition when running fast, and what parameters or parts can affect this. This has identified the limiting factors not known before.
Clear benefits developed in the project include:-
1) Modelling
Mathematical modelling has been utilised to design large pump to calculate loads at key interfaces such that the optimum loading can be obtained for the optimised geometry. The cause of high speed damage and how to prevent it by calculating loadings within mathematical kinematic model has been understood. New parametric model to design the large pump for optimum loadings at high speed have been developed.
Lubrication modelling of interface led to an improved design. The model provided understanding of instability, new design modelled then proved on test to improve high speed performance.
2) Lifing
The project has also determined the life limitations of existing pumps by investigating overhaul parts through endurance testing of pumps including hot and low lubricity fuel and materials laboratory investigation.
3) Design Guidelines
New designs for assembly have been created and developed welded design techniques on a bespoke rig. Through design workshops held with our specialists key components for attention for large pump design have been identified
4) Materials
New material combinations have been tested - 825 hours testing of new materials in pumps; lightweight rotor assembly designed for large pump and tested.
The project also saw a first for visualisation testing to show the motion of key components.
Specific testing of materials for components affected by high speed operation has been developed. Materials testing of several different options resulted in various options.
5) Testing
3 variety of pumps have been subjected to performance testing on the large pump
As a by-product the project also performed mechanical efficiency assessment - torque sensor allows measurement of power consumption; method of performance analysis to evaluate efficiencies established and started to understand causes of inefficiency. Mechanical losses were calculated – several contributors
6) Manufacturability
Designed a productionised version of the large piston pump and identified potential weight savings.
The project has demonstrated good supplier development for potential future manufacturing capability. Such items as for complex assemblies include processing, hand-offs, tolerance, surface finish and cost control
7) Wider societal implications
In terms of capability learning for our professional and future engineering staff, considerable research has been accomplished during this project including the analysis of 55 journals and 2 state of the art reports. Our materials laboratory have provided vital support, especially at the start looking into wear. Much of our assessment of pump performance is visual, or provided by microscopy, SEM analysis or surface interferometry.