Concetual design of ultra-efficient cores for mid-century aircraft turbine engines
Paper in proceeding, 2019

For today’s best turbofans propulsive efficiencies are now higher than 80% whereas thermal efficiencies only reach values around 50%. The introduction of the geared engine architecture gives some hope for continued improvement in propulsive efficiency. On the other hand, for the thermal efficiency the progress pace is fairly modest despite the much larger room for improvement. Further rapid progress is primarily challenged by small turbomachinery size and efficiency, high pressure compressor exit and turbine entry temperatures and losses associated with cooling. Fundamental thermodynamics also make progress more difficult than it used to be, e.g. for the ideal Brayton cycle an increase in overall pressure ratio from 50 to 70 will only yield a 3% unit improvement.

In 2015, the EU launched a research project, the ULTIMATE project, investigating new core engine architectures. In particular, it was argued that cycle synergy could be a way forward and that the combination of several radical concepts could potentially lead to ultra-efficient cores with less technical challenges than power plants involving single radical concepts. After an initial extensive screening and down-selection, the project developed the most promising propulsion systems to TRL 2. To evaluate the environmental improvement potential the new radical propulsion systems were integrated onto advanced tube-and-wing aircraft and evaluated against the EU SRIA 2050 targets. The paper reviews key findings from the research activities, describing design choices and the architectural evolutions that the different concepts underwent. As a first, the paper also collects the top-level achievements on CO2 emissions to draw conclusions on radical core engine cycle selection.

The most notable observation on core engine down-selection is that all concepts integrating pressure rise combustion achieved very large improvements, in particular when synergies with intercooling were explored. Large cuts in CO2 emissions were retained even when compared to year 2050 reference technology.

pulse detonation topping

composite cycle

Constant volume combustion

slotted nacelle


nutating-disc topping

ACARE 2050 targets

tube-and-wing aircraft


open rotor.


Tomas Grönstedt

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

Carlos Xisto

Chalmers, Mechanics and Maritime Sciences (M2), Fluid Dynamics

V. Sethi

Cranfield University

Andrew M. Rolt

Cranfield University

Nicolás García Rosa

Institut Superieur de l'Aeronautique et de l'Espace

D. Missirlis

Aristotle University of Thessaloniki

J. Whurr

Rolls-Royce PLC

Nicholas Tantot

SAFRAN Aircraft Engines

Martin Dietz


Anders Lundbladh

Chalmers, Mechanics and Maritime Sciences (M2)

24th ISABE conference

24th ISABE conference
Canberra, Australia,

Ultra Low emission Technology Innovations for Mid-century Aircraft Turbine Engines (ULTIMATE)

European Commission (EC) (EC/H2020/633436), 2015-09-01 -- 2018-09-01.

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Other Mechanical Engineering

Aerospace Engineering

Energy Engineering

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