Performance assessment of the Water Enhanced Turbofan engine

• Parametric analysis of the Water Enhanced Turbofan • Best cruise parameter combinations lead to excessive take-off TIT • Close to 10% reduction in TSFC • Heat exchanger installation effects cancel benefits in specific range • High specific power of humid core flow lead to high LPT temperatures An engine performance model of the Water Enhanced Turbofan (WET) is developed. The parametric analysis includes water-air ratio (WAR), turbine inlet temperature (TIT), overall pressure ratio (OPR), bypass ratio (BPR), fan pressure ratio (FPR) and six additional heat exchanger design parameters. An A350/XWB-type reference aircraft is modeled to quantify installation effects via cruise specific range. A 9.6% reduction in cruise TSFC is achieved, with a maximum reduction potential of 12.9% based on a Chilton–Colburn performance bound. However, once additional heat exchanger pressure losses, weight, and increased engine size are accounted for, no improvement in cruise specific range could be observed. Notably, the engine weight is expected to increase with 66% and the nacelle length and diameter are expected to increase with 22% and 40%, respectively, for which the condenser dominates the added heat exchanger volume. The study further highlights challenges that emerge from inherent features of the WET cycle. While higher WAR improves cruise specific range, it becomes increasingly difficult to limit TIT during take-off because reduced water recovery at elevated ambient temperature requires compensating by increasing TIT. The option of carrying additional water is evaluated as an alternative remedy, showing that for high-WAR designs more than 20 k g s − 1 of water may be required at take-off. A further challenge with the WET cycle is that as WAR increases, core specific power rises, slowing the temperature drop across the turbines. Consequently, the cooling requirement extends further into the turbine system and may require cooling of multiple low-pressure turbine stages in the WET cycle.