Evaluation of Steel Cap Piston for Upgradation of Diesel Electric Locomotives for Indian Railways

This paper deals with the evaluation of steel cap pistons for up-gradation of diesel electric locomotives for Indian Railways. These engines are four stroke, medium speed compression ignition engines (CR 12.5: 1) with output of 121 kW per cylinder on series 1 and 167 kW per cylinder on series 2. The series 1 engine uses single piece aluminum pistons, with rating of 0.295 kW/cm² of piston crown area. A higher version of the series 1 engine with higher fuel efficiency and improvement in lube oil consumption was developed. As part of this improvement program, a composite steel cap piston with forged aluminum skirt was used. The whole engine up-gradation kit including the higher capacity turbocharger, higher fuel delivery pressure fuel pump, modified cam shaft, larger after-cooler along with the steel cap piston were evaluated for performance. Subsequently more designs of the composite steel cap pistons having varied crown profiles including Mexican hat, deep bowl, dish top etc. were also evaluated. The nozzle spray angle and the fuel injection timing were also varied to see the effect on bsfc, peak firing pressures and temperatures. Based on the evaluations, improvements were done in an iterative process. A final design was accepted for fitment on the locomotive engines. This paper brings out the various designs evaluated, results and the justification for selecting the final design.