Takashima, Y., Tanaka, H., and Sako, T., "Evaluation of the Effects of Combustion by Multi-Ignition in Natural Gas Engines," SAE Technical Paper 2012-32-0065, 2012, doi:10.4271/2012-32-0065.
Recently, producing energy with reduced CO₂ emissions has been one of the most important topics of global discussion. Combined heat and power (CHP) systems, which use natural gas to produce thermal energy and electric energy simultaneously, are considered to contribute significantly to the efficient use of energy and environmental conservation. The prevalence of CHP systems is expected. From an energy security point of view, promoting the introduction of distributed energy systems, which use natural gas, is highly recommended. In a CHP natural gas engine, enhancing engine efficiency is required to save energy. The challenge with spark ignition (SI) engines is how to improve destabilizing firing in the situation of a mixed lean burn and exhaust gas recirculation (EGR) condition. This is especially important in large size of lean combustion natural gas engines, which use a pre-chamber to maintain spark ignition performance, while also avoiding knocking. The purpose of this study is to investigate the feasibility of multi-ignition in natural gas engines. Although there have been many studies of multi-ignition in gasoline engines, there have been very few studies of natural gas engines, which use higher-octane fuel. A multi-ignition engine with 8 spark plugs installed around its cylinder liner and a spark plug in the center was used in the experimental setup. The ignition time of each spark plug was controlled individually. The results of this study are given below. The combustion stability and thermal efficiency were both improved by multi-ignition from the cylinder liner. In the case of early combustion fluctuation, by increasing the number of ignitions, early combustion fluctuation was reduced, thus stabilizing main combustion. In the case of a misfire, it was found that decreasing the distance of flame propagation was better than increasing the number of spark ignitions.