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Spark ignition natural gas engines with prechamber, having high thermal efficiency and low exhaust emissions, have been developed due to energy resources and air pollution problems in recent ten years. A lot of significant results on experimental have been given, but the reports on combustion model were few seen so far. This paper discribles a quasidimensional combustion model for the engines with prechamber. A simulation method for calculating turbulent intensity in cylinder and a submodel for jet orifices between two chambers are put forward. It showed by testing that calculated data showed good general agreement with the corresponding experimental values.

This paper describes the development of a natural gas engine with a prechamber. The comparison between a conventional gas engine and the engine with the prechamber is given. The testing results show that the new combustion system is reliable and practical. The performance of the engine, compared to the conventional gas engine, is greatly improved due to stable ignition and quick flame propagation in the prechamber and a high burning rate and short burning period in main chamber. The analyses of the combustion processes and lean combustion potential in the engine are further discussed.

Experimental research was carried out by a high speed camera to observe the effects of the ambient temperature, the pressure and the parameters of injection nozzle on spray development, the ignition delay, the location of ignition, the flame propagation and the combustion rate in a constant-volume bomb which simulates the high temperature and pressure condition of Low Heat Rejection (LHR) engines. The experimental results show that at high temperature the ignition delay becomes very short and the ignition occurs near the nozzle tip. The decreased premixed combustion can't provide enough energy for subsequent air fuel mixing. The spray is enveloped totally by the flame that prevents the air entrainment to the spray. Therefore the combustion duration is prolonged at high temperature compared with low temperature.

Experimental results revealed that in many case, the performance of heat insulated engines was worse than that of the water-cooled engines due to the deteriorated combustion process at high air temperature in the insulated chamber. The observation of combustion process in high temperature air had been carried out in a constant volume bomb by the authors in a former research. In this paper, the image processing and thermodynamic analysis were applied to investigate the effects of ambient temperature on ignition, flame development and air entrainment into the spray. Based on the experimental results, the main reasons leading to the degraded combustion process at high temperature were indicated.