Comparative Evaluation of Turbochargers for High Horsepower Diesel-Electric Locomotives

Indian Railways have a fleet of high-horsepower diesel-electric locomotives rated at 2310 kW. These high horsepower diesel-electric locomotives have evolved from original design of 1940 kW locomotives. Adoption of new design turbochargers was essential for this upgrading efforts and a series of new design turbochargers were evaluated on the engine test-bed before their use on the diesel locomotives. The objective was to increase engine power output, improve fuel efficiency and limit thermal loading. Test-bed evaluation of different turbochargers was carried out for comparing five different turbochargers. Each turbocharger had different size nozzle ring, diffuser, turbine blade assembly, impeller and inducer. The compressor maps of turbochargers were used to plot the engine load lines and to calculate surge margins. The tests involved measuring critical parameters for various combinations of engine speed and load for every turbocharger. Some of these measured parameters were air inlet temperature to the compressor, peak firing pressures, inlet temperature to the turbine, cylinder head temperature, brake specific fuel consumption (BSFC), engine boost and air manifold temperature. This paper discusses the methods adopted for carrying out these evaluations and the results obtained thereof along with the decision criteria for making final selection of turbocharger for locomotives.