Experimental Investigation on the Influence of Brake Mean Effective Pressures up to 30 bar on the Behavior of a Large Bore Otto Gas Engine

For large bore Otto gas engines a high specific power output and therefore high engine load promises a rise in engine efficiency on one hand and on the other hand a reduction of the performance-related investment. However, this can negatively affect the emissions performance, operating limits especially in regards to knocking, and component life. For this reason at the Chair of Internal Combustion Engines (LVK) of the Technical University of Munich (TUM) experiments with a 4.77 l single-cylinder research engine were carried out to investigate the boundary conditions, potentials and downsides of combustion processes with a brake mean effective pressure beyond current series engines and higher than 30 bar. The objective in this investigations was to achieve BMEP > 30 bar with an engine configuration that widely represents the current series-production status. Hence, an unscavenged prechamber spark plug, a series Piston and Valve timing were used. To shift the knocking limit to more fuel-efficient operating points, different intake air temperatures were used. The engine behavior was measured in engine maps with a variation of the air-fuel equivalence ratio λ at different loads. Therefore the shift of the knocking limit, the misfiring limit and further parameters were evaluated. Moreover, the characteristic of the combustion process is analyzed at distinctive points and lines for example alongside the TA Luft [1] NO_x 500 mg/m³ line or at a constant center of combustion, for each, while varying the air-fuel equivalence ratio λ. In addition, a loss analysis showed the benefits of an increase in load and helps to characterize the high load combustion process.