Transpiration Cooling Systems for Jet Engine Turbines and Hypersonic Flight

Lead Research Organisation: University of Oxford
Department Name: Engineering Science

Abstract

This grant will deliver a step change in the understanding and predictability of next generation cooling systems to enable
the UK to establish a global lead in jet engine and hypersonic vehicle cooling technology.
We aim to make transpiration cooling, recognised as the ultimate convective cooling system, a reality in UK produced jet
engines and European hypersonic vehicles. Coolant has the potential to enable higher cycle temperatures (improving efficiency following the 2nd law of thermodynamics) but invariably introduces turbine stage losses (reducing efficiency). Cooling system improvement must enable higher Turbine Entry Temperature (TET) while using the minimum amount of coolant flow to achieve the required component life. For high speed flight, heat transfer is dominated by aerodynamic heating with gas temperatures on re-entry exceeding those at the surface of the sun. Any
reduction in heat transfer to the Thermal Protection System will ultimately lead to lower mass, allowing for decreased launch costs Furthermore, the lower temperatures could serve as an enabler for higher performance technologies which are currently temperature limited.

The highest temperatures achievable for both jet engines and hypersonic flight are limited by the materials and cooling
technology used. The cooling benefits of transpiration flows are well established, but the application of this technology to aerospace in the UK has been prevented by the lack of suitable porous materials and the challenge of accurately modelling both the aerothermal and mechanical stress fields. Our approach will enale the coupling between the flow, thermal and
stress fields to be researched simultaneously in an interdisciplinary approach which we believe is essential to arrive at the best transpiration systems. This Progreamme Grant will enable world leaders in their respective fields to work together to solve the combination of cross-disciplinary problems that arise from the application of transpiration cooling, leading to rapid innovations in this technology. The
application is timely since the proposed research would enable the UK aerospace industry to capitalise on recent
developments in materials, manufacturing capability, experimental facilities/measurement techniques and computational
methods to develop the science for the application of transpiration cooling.
The High Temperature Research Centre at Birmingham University will provide the means to cast super alloy turbine aerofoils with porosity. The
proposed grant would allow innovation in the cast systems arising from combining casting expertise with aerothermal and
stress modelling in recent EPSRC funded research programmes. It also builds upon material development of ultra-high
temperature ceramics and carbon composites undertaken in EPSRC funded research, by use of controlled
porosity and multilayer composites. It will also provide the first opportunity to undertake direct coupling of the flow with the
materials (porous and non-porous) at true flight conditions and material temperatures.
Recent investment in the UK's wind tunnels under the NWTF programme (EPSRC/ATI funded) at both Oxford University and
at Imperial College will allow for direct replication of temperatures and heat fluxes seen in flight and interrogated using
advanced laser techniques. Recent development of Fourier superposition in CFD grids for modelling film cooling can now
be extended to provide a breakthrough method to predict cooling flow and metal effectiveness for high
porosity/transpiration cooling systems.
The European Space Agency has recently identified the pressing requirement for alternatives to one-shot ablative Thermal
Protection Systems for hypersonic flight. Investment in this area is significant and transpiration cooling has been identified
as a promising cooling technology. Rolls-Royce has embarked upon accelerated investment in new technologies for future jet engines including the ADVANCE

Planned Impact

will benefit the UK engine aero-engine manufacturing sector by addressing the need for blue-sky research to provide crucial engineering science for future engines. The sector is highly competitive (with fierce competition from the USA and growing competition from Asia) and research in this field is vital for future aerospace products. Our intent is that this grant will play a significant part in underpinning the hot stage technology that is vital for future turbofans and future hypersonic vehicles. Our grant is technically very ambitious and funding from EPSRC at this stage is essential for the UK to make the progress we need.

We expect our work to lead to other R&D / BIS funded research (co-funded by industry) to integrate the technology into engines - for example, research into air system innovations to remove particles from the cooling air. Several associated programmes have already been identified and confirmed in the letter of supports from Rolls-Royce, DSTL, MBDA and LMCO. We will disseminate the results internationally through conferences, journals and research networks which will broaden international collaboration and present opportunities for future international collaborations and funding.

The jet engines are likely to be manufactured in the UK. The UK aerospace sector employs over 300,000 people in the UK both directly in the OEMs and in the specialised supply chain. Salaries paid to the high value jobs in this successful sector benefit the UK economy and these benefits are especially welcome in the East Midlands and the Bristol areas where manufacturing employment is key to the economy.

Passengers will benefit from improvements in engine efficiency reducing fuel costs and ticket prices. Similarly, this technology will eventually enable commercial hypersonic flight and improve launch costs by moving to reusable air-breathing engines such as those proposed by Reaction Engines. The airlines will be able to improve competitiveness through using more fuel efficient jet engines.

The cost of air travel is dominated by fuel costs, so the fuel efficiency improvements will support reduction in ticket costs. The aero-engine industry is committed to developing technology to reduce engine fuel burn so that
modern engines can replace older, less efficient engines.

The environment will benefit from reduced CO2 emissions from improved jet engines. Estimates of the benefits from the theoretical performance of transpiration cooling show that, for a certain class of turbofan, the engine efficiency gain from the potential reduction in coolant is estimated as capable of reducing CO2 emissions by over 180,000kg per engine per year.

Pupils and students inspired by the research will seek careers in aerospace and engineering. Jet engines and hypersonic vehicles are naturally inspiring to many pupils, students and the wider public. This will ensure that this exciting and world leading research enables us to advocate engineering and STEM subjects at outreach and public engagement activities. If successful, we envisage that the research will culminate in a flight demonstration of the transpiration cooling technology both in jet engines research (through Rolls-Royce) and in a rocket test (through DSTL).

Development of transpiration cooling has direct impact in future capabilities for the UK defence. This can be applied to improve performance and reliability of high speed missile interceptors and to understand capability of external weapon system. The new numerical approaches can not only be applied in simulating the cooling, but also as a basis for ablation modelling.

Other UK industry will gain from recruiting the students and postdoctoral researchers who work on this research. The research and engineering skills acquired by postgraduates and postdoctoral researchers will read across well into other fields of mechanical engineering.

Publications

10 25 50

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Belrhiti Y (2024) Manufacturing UHTC composites: brazing ZrB2 and Zr metals in Advances in Applied Ceramics: Structural, Functional and Bioceramics

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Belrhiti Y (2023) Gel-casting for manufacturing porous alumina ceramics with complex shapes for transpiration cooling in Advances in Applied Ceramics: Structural, Functional and Bioceramics

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Atkins C.W.C. (2020) Towards a strand/cartesian amr solver for modelling hypersonic flows in thermochemical nonequilibrium in 23rd AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2020

 
Description The grant confirmed the excellent cooling performance of a double skin cooling system when applied to a turbine blade using aerofoils manufactured at engine size using. The collaboration between the Oxford Thermofluids Institute and the High Temperature Research Centre (Birmingham University) led to the development of demonstration aerofoils being manufactured using advanced investment casting of single crystal Nickel super alloy aerofoils which were then tested under representative flow conditions in the wind tunnels. Knowledge gained and published was being applied in several civil and defence research organisations, as well as by aerospace contractors. There were almost 100 research publications funded by this grant. There were over 20 doctoral students supported by this grant. An Amelia Earhert Scholarship was awarded to Suria Subiah; an IUK Research Leaders Fellowship awarded to Dr Toby Hermann; a Schmidt Fellowship to Dr Gladys Ngetich( for further research at MIT) and Faculty positions were gained by Dr Adriano Cerminara Dr Jeremy Basley.
Exploitation Route Additional research funds were awarded by DARPA, Reaction Engines, DSTL - hypersonic vehicle, ATI / Rolls-Royce (Cordite) and MoD/Rolls-Royce (Tapas). A new grant has just been awarded to Oxford, Birmingham and Rolls-Royce by the ATI to research transition of double skin cooling systems for application to civil airliner engines.
Sectors Aerospace

Defence and Marine

Energy

Environment

Manufacturing

including Industrial Biotechology

Transport

 
Description Knowledge gained and published was being applied in several civil and defence research organisations, as well as by aerospace contractors.
First Year Of Impact 2020
Sector Aerospace, Defence and Marine,Education,Manufacturing, including Industrial Biotechology,Transport
Impact Types Economic

 
Description Membership of SPAC Committee and attendance at meeting 17th February by the PI
Geographic Reach Europe 
Policy Influence Type Membership of a guideline committee
 
Description ATI Programme - Batch 41 Research Projects
Amount £2,088,383 (GBP)
Funding ID TSB Reference: TS/Y023129/1 
Organisation Aerospace Technology Institute 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2024 
End 02/2028
 
Description Advanced HP Blade aerofoil and vane cooling
Amount £147,692 (GBP)
Funding ID DFR06950 
Organisation Rolls Royce Group Plc 
Sector Private
Country United Kingdom
Start 03/2021 
End 03/2022
 
Description Advanced HP Blade aerofoil and vane cooling SUPPLEMENT 1
Amount £110,769 (GBP)
Funding ID DFR06950 
Organisation Rolls Royce Group Plc 
Sector Private
Country United Kingdom
Start 03/2022 
End 03/2023
 
Description Bursary and fees for D Phil Student in Transpiration Cooling for Gas Turbine Application
Amount £73,000 (GBP)
Organisation University of Oxford 
Department Department of Engineering Science
Sector Academic/University
Country United Kingdom
Start 09/2016 
End 03/2020
 
Description Department of Engineering Science - University of Oxford: - Bursary and fees for M Sc in Transpiration Cooling for Hypersonic Applications
Amount £730,000 (GBP)
Organisation University of Oxford 
Sector Academic/University
Country United Kingdom
Start 09/2016 
End 03/2020
 
Description Fundamental understanding of turbulent flow over fluid-saturated complex porous media
Amount £344,938 (GBP)
Funding ID EP/W03350X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 06/2023 
End 09/2026
 
Description Impact of unsteady external and internal boundary conditions on film effectiveness and pressure margins in high effectiveness dual wall cooling systems.
Amount £194,000 (GBP)
Funding ID DFR08570 
Organisation Rolls Royce Group Plc 
Sector Private
Country United Kingdom
Start 12/2022 
End 11/2026
 
Description Studies of compressible flow over rough surfaces using Direct Numerical Simulation
Amount £240,237 (GBP)
Funding ID 20200512 
Organisation Defence Science & Technology Laboratory (DSTL) 
Sector Public
Country United Kingdom
Start 04/2020 
End 05/2022
 
Title Application of LES to transpiration cooling 
Description Professor Luca Di Mare leads the CFD modelling for the turbomachinery component of this grant. He has recently shown that Large Eddy Simulation can be applied to the process of mixing between coolant and main-stream. Furthermore, his group has shown that porous media continuum modelling can be included in the industrial CFD code used to design jet engines. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact The development of the key system (CFD code) used in the design of the gas path aerofoils for jet engines will lead to significant impact. 
 
Title Development and characterization of PILOT: a transportable instrument for laser-induced grating spectroscopy 
Description This data was created during the characterisation of the PILOT instrument. The "Accuracy and precision" dataset was collected by a Wavesurfer 3074 oscilloscope from Teledyne LeCroy, while the remaining datasets were collected by a Picoscope 6424E from Pico Technology. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL https://ora.ox.ac.uk/objects/uuid:75ae16b3-6ffc-4048-b318-a65353de5603
 
Title Polarised-depolarised Rayleigh scattering for simultaneous composition and temperature measurements in non-isothermal gaseous mixtures 
Description The data was collected between February 2018 and May 2019. The data stored are raw image (.tif) files, some experimentally-acquired, and some software-generated. There are 3 main datasets. The first of these are from polarised-depolarised Rayleigh scattering experiments conducted on a gaseous mixture of CO2 and N2. Data was collected from two opposite facing cameras imaging a single area of interest where a mixture of gases was illuminated with a laser sheet. The goal of this experiment was to demonstrate PDRS as a plausible optical diagnostic technique for non-isothermal gaseous mixtures. The second dataset was obtained by taking pictures of a white wall using varying lens apertures. This was to obtain an estimate for the shot noise characteristic of the camera, which could then be used in a numerical sensitivity analysis. The final dataset consists of an arbitrary 2D mixture fraction and temperature field (in image form), also used in the numerical sensitivity analysis. These images were produced using Paint. 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://ora.ox.ac.uk/objects/uuid:8067185e-0634-4637-910b-9122404b70cd
 
Description Collaboration with High Temperature Research Centre 
Organisation University of Birmingham
Country United Kingdom 
Sector Academic/University 
PI Contribution Definition of the aerothermal boundary conditions for effusion cooled turbine blades.
Collaborator Contribution Know how in the methods of manufacturing ( casting and machining) Nickel Super Alloy turbine blades. Knowledge of the spark eroding supply chain and introduction to specialist companies in the UK that can machine turbine blades and associate materials.
Impact On going
Start Year 2016
 
Title Method of Manufacturing an Article 
Description This invention relates generally to a method of manufacturing a component for use in high temperature environments, e.g. jet engines, using bonding materials. More specifically, although not exclusively, this invention relates to a method of manufacturing a component having an internal structure using bonding materials. One such use for an internal structure might be to provide or facilitate cooling, e.g. to form or facilitate an effusion or transpiration internal cooling system. 
IP Reference PCT/GB2023/052283 
Protection Patent / Patent application
Year Protection Granted
Licensed No
Impact The examiners report has been received and the University of Birmingham is commencing the process of identifying potential licensees.
 
Description Meeting of the International Advisory Committee 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact In October, our International Advisory Committee met in Oxford to review our research activities and plans. We spent a day going through the aims and achievements of all the work packages. Other colleagues from industry and academia attended. The panel includes colleagues from Japan, USA, Germany and Australia. The feedback was completely positive, with some advice on routes to impact.
Year(s) Of Engagement Activity 2017
 
Description SCIENCE FESTIVAL ( IF OXFORD) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact BLAST - Today's skills / tomorrow's technology. This event was part of the Oxford Science Festival. It was held in a Community Centre in Oxford. It took place during autumn term school half term. We demontrated aerospace and space technology and instrumentation to an audience of school children (and their parents/carers). The presentations were from Postgraduate students and Postdocs working on the grant.
Year(s) Of Engagement Activity 2019
URL https://if-oxford.com/if-oxford-2019-programme-available-now/
 
Description Seminar from colleagues from Korea engaged in Transpiration Cooling research 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Dr Jungho Lee Ph.D. / Principal Researcher from the Department of Extreme Thermal Systems at the Korean Institute of Machinery and Materials (KIMM), Daejeon, 305-343, Korea visited Oxford in October and gave a talk on his recent work on transpiration cooling the Thermofluids Group in the Department of Engineering Science. A reciprocal visit by Prof Mc Gilvray to KIMM is planned in late 2016.
Year(s) Of Engagement Activity 2016
URL http://www.eng.ox.ac.uk/thermofluids/seminars