The impact of design space constraints on the noise and emissions from derivative engines for civil supersonic aircraft

In recent years, there has been growing interest in the development of new commercial supersonic transport (SST) aircraft. Historically, the propulsion systems used in commercial supersonic aircraft, such as the Concorde, have employed derivative engines that have repurposed engines or cores from existing donor engines, as opposed to purpose-designed clean-sheet engines. A similar approach is actively being adopted by current industry players for future commercial SST. In this work, we quantify the impact of design space constraints on the noise and emissions from such derivative engines relative to clean-sheet engines. We design a clean-sheet and derivative engine for a NASA-designed, notional 55-tonne commercial SST. We use an engine cycle model combined with the P3-T3 method and the SAE ARP876 jet power level method to quantify the impact of the constrained donor core on the noise and emissions from derivative engines. We evaluate the design space constraints imposed by the donor core using a first-principles approach. We find that a clean-sheet engine design can result in a 0.6% improvement in thrust specific fuel consumption (SFC) at cruise relative to a derivative engine at the same technology level and a ~1% reduction in take-off NOx emissions while incurring a 0.86 dB increase in take-off jet noise power. We also find that a clean-sheet design can be optimized for minimum SFC by using higher pressure ratio compressors (within material limits) to obtain ~2.2% reduction in SFC relative to the derivative engine at the cost of ~37% increase in take-off NOx emissions and a 1.1 dB increase in take-off jet noise power.