LEMCOTEC: Improving the Core-Engine Thermal Efficiency

Abstract

This paper describes the research carried out in the European Commission co-funded project LEMCOTEC (Low Emission Core Engine Technology), which is aiming at a significant increase of the engine overall pressure ratio. The technical work is split in four technical sub-projects on ultra-high pressure ratio compressors, lean combustion and fuel injection, structures and thermal management and engine performance assessment. The technology will be developed at subsystem and component level and validated in test rigs up to TRL5. The developed technologies will be assessed using three generic study engines (i.e. regional turbofan, mid-size open rotor, and large turbofan) representing about 90% of the expected future commercial aero-engine market. Two additional study engines from the previous NEWAC project will be used for comparison. These are based on intercooled and intercooled-recuperated future engine concepts. The compressor work is targeting efficiency, stability margin and flow capacity by improved aerodynamic design. High-pressure and intermediate-pressure compressors are addressed. The mechanical and thermo-mechanical functions, including the variable-stator-systems, will be improved. Axial-centrifugal compressors with impeller and centrifugal diffuser are under investigation too. Three lean burn fuel injection systems are developed to match the technology to the corresponding engine pressure levels. These are the PERM (Partially Evaporating Rapid Mixing), the MSFI (Multiple Staged Fuel Injection) and the advanced LDI (Lean Direct Injection) combustion systems. The air flow and combustion systems are investigated. The fuel control systems are adapted to the requirements of the ultra-high pressure engines with lean fuel injection. Combustor-turbine interaction will be investigated. A fuel system analysis will be performed using CFD methods. Improved structural design and thermal management is required to reduce the losses and to reduce component weight. The application of new materials and manufacturing processes, including welding and casting aspects, will be investigated. The aim is to reduce the cooling air requirements and improve turbine aerodynamics to support the high-pressure engine cycles. The final objective is to have innovative ultra-high pressure-ratio core-engine technologies successfully validated at subsystem and component level. Increasing the thermal efficiency of the engine cycles relative to year 2000 in-service engines with OPR of up to 70 (at max. condition) is an enabler and key lever of the core-engine technologies to achieve and even exceed the ACARE 2020 targets on CO2, NOx and other pollutant emissions: • 20 to 30 % CO2 reduction at the engine level, exceeding both, the ACARE 15 to 20% CO2 reduction target for the engine and subsequently the overall 50% committed CO2 and the fuel burn reduction target on system level (including the contributions from operations and airframe improvements), • 65 to 70 % NOx reduction at the engine level (CAEP/2) to attain and exceed the ACARE objective of 80% overall NOx reduction (including the contributions from both, operational efficiency and airframe improvement), reduction of other emissions (CO, UHC and smoke/particulates) and • Reduction of the propulsion system weight (engine including nacelle without pylon).

A Composite Cycle Engine Concept with Hecto-Pressure Ratio

“…The presented CCE concept was investigated in the LEMCOTEC project Work Package "Future Cycle Studies" targeting concepts for an Entry Into Service year range of 2030 to 2050. The improvement potential of the CCE concept is evaluated in contrast to a generically defined Regional Turbofan (RTF) reference engine with an expected technology standard of year 2025 18 . The RTF is a two spool geared turbofan with a maximum OPR of 50.…”

Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

“…Present goals in the development of turbomachines for flight propulsion are oriented towards a further increase of pressure ratio and efficiency with a simultaneous reduction of the number of blades and stages of compressor and turbine [1]. For stationary gas turbines used to generate electric power, challenging demands on flexibility and operation under partial load result from the volatile availability of renewable energies [2].…”

Aero-thermal flow characterization downstream of an NGV cascade by five-hole probe and filtered Rayleigh scattering measurements

“…The introduction of lean burn combustion concepts is considered a promising path on the route of increasing the overall efficiency of aero-engines while at the same time meeting tightened emission targets (von der Bank et al, 2014). Novel fuel injector designs are required, which eventually lead to a substantial redirection of air mass inside the core engine.…”

“…As a consequence, highly swirling flows, characterized by severe temperature gradients (hot streaks) and significant turbulence approach the turbine. These unsteady flow fields significantly challenge the reliability of common design procedures (von der Bank et al, 2014;Chevrier and Bertrand, 2017).…”