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This work presents development and results of experimental and numerical investigations of an advanced ignition system with a scavenged pre-chamber for a natural gas fueled engine with a bore of 102 mm and stroke of 120 mm. Two combustion concepts are taken into account. The lean burn concept is used to minimize engine out emissions of nitric oxides (NOx) and to achieve high thermal efficiency at low load. The in-house designed scavenged pre-chamber enables the engine to be operated up to the air-excess ratio (lambda) of 2. A stoichiometric (lambda=1) operation is also possible. It is compatible with a three-way catalyst concept, at high load and potentially transient modes and can provide as high as possible engine power density. The influence of the scavenged pre-chamber volume on the combustion and performance within the range of the operational points of the naturally aspirated engine is presented in this paper.

In this article the development of a combustion system with a fuel-scavenged pre-chamber is described. Such a system is commonly used in large-bore engines operated with extremely lean mixtures. The authors implemented the scavenged pre-chamber into a light duty truck-size engine with a bore of 102 mm. The lean burn strategy is intended to achieve very low nitrogen oxide (NOx) emissions at low load. At full load a stoichiometric mixture strategy is applied to achieve sufficient power density while simultaneously enabling the use of a relatively simple three-way catalytic converter for exhaust gas aftertreatment. This work outlines the pre-chamber design features and introduces the results of an experimental investigation of the effect of pre-chamber ignition on a single cylinder testing engine.

New regression approach for heat release pattern prediction for various operating conditions for gas fuelled SI engines has been developed and verified. This procedure has been implemented in our engine working cycle simulation code. Crankshaft angle positions of combustion start-point, maximum rate-of-heat-release point and combustion end-point are expressed by the use of regression method as the function of engine operating point specification. Base heat-release pattern is employed in the model in a tabular form. The pattern at a new operating point is derived by stretching the pattern along the crank angle coordinate, fitting it in the most relevant points of the heat release pattern. The regression model is based on the results of experiments of both homogeneous stoichiometric and lean burn SI turbocharged engines fuelled by natural gas.