Intake and exhaust position optimization in the cooling duct of diesel helicopters

CRDID (Common Rail Direct Injection Diesel), automotive derived engine, main advantage is the enormous amount of experimental data. These engines are produced in millions of units and reliability data based trillions of hours are available. It is also possible to run automotive CRDIDs with jet fuel. It is also possible to mix the two fuels with a proper ECU (Electronic Central Unit) mapping. Therefore, the necessity to refuel in airports can be eliminated. Moreover, the additional mass of CRDIDs is largely compensated by the reduced fuel amount necessary to exploit the same mission/flight. However, an additional cooling system duct should be added. For this purpose, fans are replaced by ejector exhaust (augmenter) that does not need fan additional power. Solid Works Flow Simulation confirmed the feasibility of an ejector-exhaust-powered cooling. However, pressure fields around the helicopter varies in a very significant way in the different flight conditions. High cooling duct efficiency requires pressure and clean air at the intake port and negative pressure at the duct nozzle. Therefore, a optimization of the cooling duct positioning has been carried out on a common light helicopter (Eurocopter EC 120). Several different solutions have been simulated with Solid Works Flow Simulation. CFD confirms the ejector choice and the design criteria. The best configuration is a derivation of a Formula 1 intake duct. This solution proved to be the most effective for the CRDID-exhaust powered cooling duct. The result is that the ejector exhaust (augmenter) is extremely effective. With two small intakes at the side of the mast, the pressure differential between the intake and the nozzle of the duct proved to be extremely stable in every flight condition, even with crosswind.