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A new electric air-cycle system of aircrafts is investigated focusing on energy recovery from the exhaust air. The working fluid of air has the higher energy level in the cabin than in the outside during the cruise because the outside air is at low pressure and low temperature. In the system, by setting a recovery turbine behind the cabin, the discharged energy can be collected, although the working fluid through the system has been only discharged from the cabin into the outside. We perform a thermodynamic cycle-analysis, where the temperature, pressure, entropy, etc. are calculated at each position of the cycle by considering the two pressure ratios of the compressors as variable parameters to show T-s diagram. In addition, we obtain an energy recovery rate of the recovery energy to the necessary power for the electric compressor. The energy recovery rate is roughly estimated 40-80% under the reasonable practical operating conditions.

Electrical power management is a key technology in the AEA (All-Electric Aircraft) system, which manages the supply and demand of the electrical power in the entire aircraft system. However, the AEA system requires more than electrical power management alone. Adequate thermal management is also required, because the heat generated by aircraft systems and components increases with progressive system electrification, despite limited heat-sink capability in the aircraft. Since heat dissipation from power electronics such as electric motors, motor controllers and rectifiers, which are widely introduced into the AEA, becomes a key issue, an efficient cooling system architecture should be considered along with the AEA system concept. The more-electric architecture for the aircraft has been developed; mainly targeting reduced fuel burn and CO2 emissions from the aircraft, as well as leveraging ease of maintenance with electric/electronic components.

To improve an energy optimization issue of ECS for MEA, we propose our concept in which ACS is replaced with VCS. A VCS is generally evaluated as auxiliary or limited cooling system of an aircraft. Cooling demand of commercial aircraft usually becomes large due to ventilation air at hot day conditions. In case of using conventional VCS for whole cooling demand, the ECS becomes too heavy as aircraft equipment. Though ACS's light weight is advantageous, the issue that VCS will be available for aircraft ECS is important for saving energy. ECS of commercial aircraft should work for three basic functions, i.e. pressurization, ventilation, and temperature control. The three functions of the ECS for bleed-less type of MEA can be distributed among equipment of the ECS. MDFAC works for pressurization and ventilation. Therefore, we should select appropriate system for only temperature control.

This paper describes the concept of an air/fuel integrated thermal management system, which employs the VCS (Vapor Cycle System) for the refrigeration unit of the ECS (Environment Control System), while exchanging the heat between the VCS refrigerant and the fuel into the engine, and presents a feasibility study to apply the concept to the future all electric aircraft systems. The heat generated in an aircraft is transferred to the ECS heat exchanger by the recirculation of air and exhausted into the ram air. While some aircraft employ the fluid heat transfer loop, the transferred heat is exhausted into the ram air. The usage of ram air for the cooling will increase the ram drag and the fuel consumption, thus, less usage of ram air is preferable. Another source for heat rejection is the fuel. The heat exchange with the fuel does not worsen the fuel consumption, thus, the fuel is a preferable source.