Performance of a low heat rejection diesel engine with air gap insulated piston

A threaded air gap insulated piston provided effective insulation without c ausing 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 min at an injectio n timing of 29.5 degrees bTDC reduced the BSFC by 12 percent at part loads and 4 percent at full load. The performance in terms of P-theta and T-theta was predicted employing a zero dimension multizone combustion motel, and t he model results have been validated with measured pressures and the exhaus t gas temperatures. More appropriate piston surface temperatures were emplo yed in Annand's equation regulation to improve the computer predictions ris ing finite element modeling of the piston. The measured temperatures of air in the air gap using an L-link mechanism provided excellent validation for he finite element prediction of isotherms in the piston.