Relationship between engine in-cylinder flow and heat release under varying equivalence ratios and fuel stratification conditions

In-cylinder pressure-based heat release analysis and flow characteristics were used to investigate the effect of bulk flow and mixture stratification on combustion in a CI engine. Particle imaging velocimetry was employed to acquire the velocity flow field at a plane (z = 5 mm) from the fire deck at 1600 revolutions per minute engine speed. The intake port configuration was varied to induce different bulk flow features in the in-cylinder air motion. An injection timing sweep from conventional to advanced injection timings (5 to 40 degrees before the top dead centre) was performed to understand the impact of spray-swirl on the combustion. The global intake equivalence ratio was varied to attain different fuel stratification levels for the same injection timing. A statistical analysis of velocity and combustion parameters has been presented in this study. The sensitivity of combustion to the intake port configuration has been discussed. The experimental findings suggested that the investigated swirl ratios can control combustion rate for fuel injection timing near the TDC. The instantaneous reaction rate becomes constant at intermediate injection timings. The effect of swirl intensity is non-monotonic on combustion rate at the most advanced injection timings investigated. Bulk flow fluctuation can be a crucial parameter influencing the combustion stability and combustion rate in the early injection condition. The combustion characteristics can be used to understand the role of the pilot injection in dual-fuel CI combustion.