Transpiration Cooling Systems for Jet Engine Turbines and Hypersonic Flight

Lead Research Organisation: University of Oxford


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.


10 25 50
Description The turbine work (experiments and modelling) showed a cooling benefit to the double skin system that will be used by the aero-engine partners to reduce the fuel consumption for future jet engines. Our partners at Birmingham University developed a very clever way of casting the super alloy blades that should be scalable.
Exploitation Route Follow on work is underway in industry, at Oxford and at Birmingham to refine the approach to enable the benefits of the science to be used for UK built jet engines.
Sectors Aerospace, Defence and Marine

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 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 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 03/2023 
End 09/2026
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  
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
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
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
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