Computational Analysis of Environmental Control System of an Aircraft Using Dry and Moist Air as Medium

For a fighter aircraft to operate effectively in severe weather conditions, an efficient and effective Environmental Control System (ECS) is one of the basic requirements. Accurate working of electronic equipment installed in cockpit and comfort of pilot require temperature, pressure and humidity levels inside the cockpit to be well within limits as defined in the Mil standard MIL-E-18927E(AS). In this paper, computational analysis of cockpit Environmental Control System (ECS) of a fighter aircraft for a designed (dry air) and an off designed condition (moist air) is presented. Certain flight conditions which are defined in the aircraft flight envelope are used to design an effective ECS of the understudy aircraft to ensure comfortable temperature environment for the pilot and electronic equipment. To validate ECS performance, analysis at the most severe environmental conditions (International Standard Atmosphere + 30°C while flying at 0.825 Mach Number at sea level) has been considered. Complete analysis of flow and temperature field inside the cockpit has been performed in FLUENT® for performance verification. In the first analysis, dry air properties have been used as per design. This is possible due to availability of water separator in the system design which removes most of the water vapors in the cold air coming from the cooling turbine before entering the cockpit. In addition, an analysis of ECS performance for an off design condition by assuming saturation/failure of water separator which results into provisioning of moist air in the cockpit has also been presented. ECS performance under both the conditions has been thoroughly evaluated with respect to MIL standard MIL-E-18927E(AS) and the results have been found satisfactory. It has been demonstrated that CFD techniques can be used to analyze the flow and temperature field inside the cockpit of an aircraft.