The performance and emissions of a single-cylinder natural gas fueled engine using a pilot ignition strategy have been investigated. Small diesel pilots (2–3% on an energy basis), when used to ignite homogeneous natural gas-air mixtures, are shown to possess the potential for reduced NOx emissions while maintaining good engine performance. The effects of pilot injection timing, intake charge pressure, and charge temperature on engine performance and emissions with natural gas fueling were studied. With appropriate control of the above variables, it was shown that full-load engine-out brake specific NOx emissions could be reduced to the range of 0.07–0.10 g/kWh from the baseline diesel (with mechanical fuel injection) value of 10.5 g/kWh. For this NOx reduction, the decrease in fuel conversion efficiency from the baseline diesel value was approximately one to two percentage points. Total unburned hydrocarbon (HC) emissions and carbon monoxide (CO) emissions were higher with natural gas operation. The nature of combustion under these conditions was analyzed using heat release schedules predicted from measured cylinder pressure data. The importance of pilot injection timing and inlet conditions on the stability of engine operation and knock are also discussed.
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.
The performance and emissions of a single-cylinder, natural gas fueled engine using a pilot ignition strategy have been investigated. Small diesel pilots (2–3 percent on an energy basis), when used to ignite homogeneous natural gas-air mixtures, are shown to possess the potential for reduced NOx emissions while maintaining good engine performance. The effect of pilot injection timing, intake charge pressure, and charge temperature on engine performance and emissions with natural gas fueling was studied. With appropriate control of the above variables, engine-out brake specific NOx emissions could be reduced to the range of 0.07–0.10 g/kWh from the baseline diesel (with mechanical fuel injection) value of 10.5 g/kWh. For this NOx reduction, the decrease in fuel conversion efficiency from the baseline diesel value was approximately 1–2 percent. Total unburned hydrocarbon (HC) emissions and carbon monoxide (CO) emissions were higher with natural gas operation. Heat release schedules obtained from measured cylinder pressure data are also presented. The importance of pilot injection timing and inlet conditions on the stability of engine operation and knock are also discussed.
The Advanced 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 1700 rev/min are presented in this paper. The potential of the ALPING engine is realized in reduced NOx emissions (less than 0.2 g/kWh) at all loads accompanied by fuel conversion efficiencies comparable to straight diesel operation. Some problems at advanced injection timings are recognized in high unburned hydrocarbon (HC) emissions (25 g/kWh), poor engine stability reflected by high COVimep (about 6 percent), and tendency to knock. This paper focuses on the combustion aspects of low pilot ignited natural gas engines with particular emphasis on advanced injection timings (45°–60°BTDC).
Research has shown that a large amount of natural gas (NG) is unburned at light loads in an NG fuelled/micro-pilot diesel compression ignition engine. A mechanism of unburned hydrocarbon (HC) reduction using multiple injections of micro-pilot diesel has been proposed in this paper. Multidimensional computations were carried out for a dual-fuel engine based on a modified CAT3401 engine configuration. The computations show that a split injection with a small percentage (e.g. 30 per cent of diesel in the second injection pulse) can significantly reduce HC, CO and NOx emissions. Based on parametric studies to optimize the timing of both of the injection pulses, HC emissions could be reduced by 90 per cent, with a reduction in CO emissions of 50 per cent and NOx emissions of 70 per cent in comparison to a single-injection pulse-base case configuration.
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