Feasibility Study of a 6V-92TA Homogeneous Auto-Ignited Two-Stroke (HAT) Compressed Natural Gas Engine. Topical Report August 1989-May 1990

摘要

The objective of the project was to modify a two-stroke 6V-92TA diesel engine to operate on natural gas using a simple system with gas addition to the compressor inlet and a spark plug for cold start and non-autoignition engine operation. The engine was to be operated at most speed-load conditions by autoignition of the premixed gas-air mixture. This concept is referred to as the Homogeneous Auto-Ignited Two-Stroke (HAT). Autoignition of carbureted natural gas was achieved at various loads and speeds in a 6V-92TA engine modified for operating on natural gas with the HAT concept. However, HAT engine operation up to 277 hp at 2100 rpm (diesel coach rating) was not achieved because early ignition in some cylinders caused knock and excessive heat transfer. Instead, the engine was operated up to 226 hp (767 N.m) at 2100 rpm, 181 hp (780 N.m) at 1650 rpm, 130 hp (773 N.m) at 1200 rpm, and 34 hp (368 N.m) at 650 rpm. Maximum brake thermal efficiency measured was 33.4% at 2100 rpm/219 hp. The corrected efficiency (to compensate for the unburned natural gas lost during the scavenging process) was higher than this. Steady-state emissions show very low NOx, total unburned HC lower than expected and reasonable CO levels. The lean air-fuel mixture and unburned exhaust gases in the cylinder resulted in very low NOx emissions.