Numerical simulation and experimental study of TR combustion system

TR(Three-Rapidity) combustion system was designed to replace the original deep cave omega combustion in 135-type diesel engine. It is combined of a deep cave omega combustion chamber with contractive throat, an oriented arc in the middle of chamber wall and a nozzle with 4x Phi 0.36 orifices in conic section plus 1 x Phi 0.20 orifice in center. Three-dimensional numerical simulation of TR combustion system was completed by STAR-CD. Computation starts from intake valve close timing (140 degrees CA BTDC) to 140 degrees CA ATDC. Based on the experiment results, the temperature is assumed to be 320K, 520K, 500K and 500K respectively corresponding to initial air, cylinder head, piston top and cylinder wall. And the initial pressure is 0.1MPa. The emphases of investigation are on the mixture formation and combustion process. It was proved that TR system. has 43.84 m2/s2 in the maximal turbulent kinetic energy, but the original omega system has only 8.478m2/s2. The oriented arc on the chamber wall changes the airflow direction and forms a small anticlock-wise eddy near the slope wall. It contributes to the great maximal turbulent kinetic energy. In ignition time, the high temperature is 1462K in TR system and 2095K in the original omega system. In main combustion period, TR chamber has the high temperature in the center and the low temperature near the wall. The flame propagates from the center to the outside. The contractive throat of TR chamber guides the airflow direction and generates a strong turbulence even in late combustion period. The diffusive combustion duration get shorter and the soot significantly minimize. Experimental study shows that TR has low smoke emission in whole load conditions. NOX is lower than that of original engine except for the high load condition. TR combustion system has a promising application in diesel engine.