The energy and exergy analysis on a novel onboard co-generation system based on the mini scale compressed air energy storage

Abstract

There are serious energy waste and fluctuation during the aircraft flight due to off-design operating mode. In this paper, a co-generation system based on the mini scale compressed air energy storage is proposed to address this problem. It is expected to reduce the fuel consumption, the fluctuation of aircraft bleed air and energy loss of the aircraft. The OCSM can improve the flight performance of the aircraft which can be well integrated with the original parts of the aircraft. Since the system can uniformly produce and distribute cooling energy, electricity and thermal energy, it further improves the aircraft energy efficiency and reduces the complexity of aircraft component. The detailed thermodynamic and transmission models of the system are established. The study is focused on the influence of inlet fuel flow, valves opening conditions and demand fluctuation. The energy efficiency, the exergy efficiency and the exergy loss indicators have been put forward to assess the performance of the system under the key parameters changing and load disturbance. Then the energy flow under different energy charging/discharging conditions is discussed. Thereafter, the components with the largest energy loss and the stored energy of the air tank are obtained. It is found that the energy utilization efficiency of the system first increases and then decreases as the fuel flow rate grows. When the flow rate is 0.015 kg/s, the energy utilization efficiency reaches the maximum, which is 81.70%. The loss of burning room is largest of 179.4 kW when the stored air gets into expanders. The biggest stored energy is 44.2 kW. The exergy analysis applied to the system shows that the exergy loss of the burning room is largest in both energy charging and discharging. The exergy released by the air tank has significantly increased the exergy efficiency which is 39.16% in charging and 49.37% in totally discharging. Under electric load fluctuation condition, the inlet air flow of compressor increases with the rising disturbance, while the inlet flow hardly changes under cold load fluctuation condition. The exergy loss of the burning room is maximum in both conditions which gets maximum at 60% disturbance under electric load fluctuation of 312 kW.