Optimization of Intercooled Turbofan Jet Thermodynamic Cycle Considering Weight Penalty and Pressure Loss of Heat Exchanger

Abstract

Thermal cycles of a turbofan jet engine equipped with an intercooler are optimized for two different engine sizes to understand the engine characteristics. The optimization tool consists of a thermodynamic cycle analysis module, a weight evaluation module, a heat exchanger model and an optimization routine. It is confirmed that the tool searches for a reasonable design point within a ten-dimensional design space. The pressure ratio of a conventional turbofan is restricted by the compressor exit temperature. In contrast, intercooling enables higher pressure ratios and hence higher core thermal efficiency. The net decrease in fuel consumption is small however, because the thermal efficiency improvement, weight penalty and pressure loss are all at the same order of several percent. The minimum blade height at the compressor exit imposes another restriction on the pressure ratio increase for small intercooled engines, and net fuel consumption in small engines may increase by intercooling. The performance of an intercooled turbofan is determined by a balance between thermal efficiency improvement through the increase in pressure ratio and disadvantages resulting from additional weight and pressure losses. The development of a light, low-pressure-loss heat exchanger and optimization of the thermodynamic cycle are important.