Experimental study on the influence of combustion chamber on the combustion process of a natural gas engine

Under the background of energy transition, natural gas serves as a low-carbon, clean energy source that reduces internal combustion engines' dependence on petroleum and promotes energy diversification. However, the efficient combustion of heavy-duty stoichiometric combustion natural gas engines is still constrained by the contradiction between low fuel consumption and knocking. It has been demonstrated that applying EGR combined with advancing spark timing can improve the thermal efficiency of the engine. However, this improvement is constrained by the EGR intake capacity, combustion stability, and knocking. In this context, research has shown that rapid combustion can enhance engine thermal efficiency under the same EGR rate and spark timing conditions. Additionally, rapid combustion shortens the time required for flame propagation to the end-gas. Therefore, this paper presents an experimental study on the influence of combustion chamber on achieving rapid combustion of a 13L heavy-duty stoichiometric combustion natural gas engine. By optimizing combustion chamber, the heat release process can be significantly enhanced. When the engine is equipped with eccentric half annular combustion chamber, the brake thermal efficiency is increased from 38.10 % to 40.12 %. By organizing the rapid combustion process, combined with EGR and spark timing, the peak heat release rate is controllable in the range of 417–678 J/°CA, and its corresponding phase is controllable in the range of 11–21°CA ATDC. The controllable range of the engine's heat release process has been broadened, providing extensive support for achieving high efficiency and clean combustion in natural gas engines.