Performance of a Low Heat Rejection Diesel Engine With Air Gap Insulated Piston

A threaded air gap insulated piston provided effective insulation without causing sealing problems. The performance of the diesel engine with the air gap insulated piston was obtained with different piston crown materials, at differing magnitudes of air gap with varying injection timings. The engine using Nimonic for the piston crown with an air gap of 3 mmm at an injection timing of 29.5{degree} bTDC reduced the BSFC by 12 percent at part loads and 4 percent at full loads. The performance in terms of P-{theta} and T-{theta} was predicted employing a zero dimensional multizone combustion model, and the model results have been validated with measured pressures and the exhaust gas temperatures. More appropriate piston surface temperatures were employed in Annand`s equation to improve the computer predictions using finite element modeling of the piston. The measured temperatures of air in the air gap using an L-link mechanism provided excellent validation for the finite element prediction of isotherms in the piston.