April 21, 2023, ©. Leeham News: This is a summary of the article New aircraft technologies. Part 9P. Engine core advances. The article discusses how developments for the next-generation airliner engine cores will increase the thermal efficiency of next-generation engines.
In the last Corner article, we looked at the propulsive efficiency improvements we can expect for the next generation heart of the market airliner engines.
Now we looked at what improvements in thermal efficiency we can expect from the cores that drive these engines’ fans/open rotors.
We look at what defines the efficiency of a core and what sets its size relative to the fan/open rotor it shall drive.
The efficiency is set by the Overall Pressure Ratio (OPR) of the core together with the component efficiencies of the compressors and turbines.
We can expect the next-generation engines to come close to the pressure levels of today’s best longhaul engines, with cruise values around 50:1.
Figure 1 shows how this can be achieved with a compact core. The high core RPMs of a geared engine enable high compressor and turbine stage pressure changes, making for a high OPR core with few compressor and turbine stages (at the expense of a gearbox to the fan).
The core’s Turbine Inlet Temperature, TIT, decides the shaft power level it can deliver to the fan/open rotor.
Better high-temperature coatings and materials and more efficient cooling solutions will increase the TIT on these high-cycle engines close to the level of today’s long-haul engines.
If more heat-resistant materials like Ceramic Matrix Composites can be used for turbine components (Figure 2), the cooling air sapped from the compressor can be reduced. It will benefit the efficiency of the core.
Overall we can expect the next generation of high-cycle cores to reach the efficiency and power levels of today’s best long-range engines.