Thermal and Structural Analysis of a Semi-adiabatic Diesel Engine (SADE) with Air-gap Insulated Piston of Airgap Thicknesses 2.6MM and 2.8MM, Fueled with Plastic Oil Blends

Abstract

Aims: To determine the amount of heat dissipated across an air-gap insulated piston with airgap thickness of 2.6mm (SADE-1) and 2.8mm(SADE-2) through steady state thermal analysis. The maximum von mises stress along with the maximum deflection of SADE-1 and SADE-2 are determined through static structural analysis. Study Design: To reduce the non-exhaust emissions and the heat dissipated to other parts of a piston in diesel engines fueled with alternative fuels, an air-gap insulation of specific thickness is created between the piston crown and the piston body which acts as a thermal barrier which is expected to reduce the amount of heat dissipated. Methodology: An air-gap between the piston crown and the body is created by using an insert- which usually is known as a shim. Two shims of thickness 1.0mm and 1.2mm, made of stainless-steel are used to assemble the airgap insulated pistons of thicknesses 2.6mm (SADE-1) and 2.8mm (SADE-2) respectively. The 3-D models and the required air-gap piston assemblies is designed and exported to ANSYS workbench for thermal analysis. The analysis was performed by using the vertical sectional view of the 3-D models, as the effect of the air-gap insulation would be more clearly visible. The impact of the air-gap insulation on the structural integrity of the SADE is evaluated by determining the maximum deflection and the maximum von-mises stresses induced for each blend. The analysis results are then compared for the thickness of the airgap insulation in all blends. Results: Heat dissipated across the piston and the maximum deflection were the lowest for the PBO30 blend. However, the maximum von-mises stress was marginally higher than the other blends. Conclusion: PBO30 has the lowest heat dissipated rate among all the blends and hence can be used as a fuel to test the performance and emissions of the engine.