Numerical Simulation of Flow across a Radial Turbine for Prediction of Shaft Power for Driving Automobile Air Conditioners

The exhaust gas spouting from the exhaust manifold into the radial inflow turbine coupled to an exhaust pipe of a 2.5L petrol engine has been computationally simulated in order to ascertain the extent of exhaust energy recoverability for driving the vehicle auxiliaries, using Autodesk CFD. In order to determine the amount of power available at the turbine shaft at varying engine speeds, properties of the flow and fluid spouting into the turbine from the engine and out of the turbine from the volute outlet were examined by applying the SST k-? turbulence model and advanced Petrov-Galerkin's advection scheme. For the test engine used with the operating range of 2000-6000rpm, at engine speeds up to 3000rpm, the available power was about 0.3kW. At 4000rpm, about 2.8kW of power is available at the turbine shaft, increasing to 7.7kW at 5000rpm and 43.6kW at 6000rpm. Curve-fitting shows that at 5500rpm, as much as 15kW reversible power can be extracted from a shaft coupled to the turbocharger turbine. With an electrically-assisted turbine component of the turbocharger used, the compressor of vapour compression refrigeration system of the vehicle will be efficiently driven at all engine speeds while exhaust energy recovery is achieved.