Study of VCS Design for Energy Optimization of Non-Bleed Electric Aircraft 2014-01-2225
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. For the function of temperature control, system with higher COP should be selected due to energy saving. We define that the appropriate system consists of not ACS but VCS. Especially, on the ground, electrical taxiing without main engine operating makes energy saving of the ECS quite important.
To evaluate performance of the ECS, we select a single aisle MEA in which MDFACs are installed. We try to clarify appropriate VCS, of which specification, configuration, and weight are estimated. To avoid increase of fuel consumption by additional weight, both cooling capacity and target weight of the VCS are the same as those of ACS model. We analyze performances and weights of main components of the VCS. From this analysis, the following results are introduced.
A refrigerant compressor must consist of a high speed motor and centrifugal compressor impellers, which should be configured as 2-stage compression due to low pressure ratio at each stage. It is proper that those impellers are located at both sides of the motor.
Due to small size and light weight in spite of enough heat transfer, evaporator and condenser of the VCS should be designed with larger intake area and lower pressure loss than those of heat exchangers for the ACS model.
Birth of the light weight VCS will make conventional ACS be replaced by the VCS, and energy consumption of aircraft will be reduced especially on the ground on hot day. In case of the aircraft model (single aisle, MEA with MDFACs), energy consumption of maximum cooling on the ground will be cut to almost a half. The reduction is convenient for electrical taxiing without main engine operating.