The Advanced Injection Low Pilot Ignited Natural Gas Engine: A Combustion Analysis

The Advanced (injection) Low Pilot Ignited Natural Gas (ALPING) engine is proposed as an alternative to diesel and conventional dual fuel engines. Experimental results from full load operation at a constant speed of $1700rev∕min$ are presented in this paper. The potential of the ALPING engine is realized in reduced $NOx$ emissions (to less than $0.2g∕kWh$⁠) accompanied by fuel conversion efficiencies comparable to straight diesel operation. Some problems at advanced injection timings are recognized in high unburned hydrocarbon (HC) emissions $(25g∕kWh)$ and poor engine stability reflected by high $COVIMEP$ (about 6%). This paper focuses on the combustion aspects of low pilot ignited natural gas engines with particular emphasis on advanced injection timings (45°–60° BTDC). Ignition phasing at advanced injection timings (⁠$∼60°$ BTDC), and combustion phasing at retarded injection timings (⁠$∼15°$ BTDC) are recognized as important combustion parameters that profoundly impact the combustion process, HC emissions, and the stability of engine operation.