A Study was conducted on the raw emissions of a heavy duty diesel engine

which was in the process of upgraded from China Ⅴ compliance to China Ⅵ compliance and the raw emissions of which exceeded the target set by the enterprise. A method was proposed to reduce the raw emissions by controlling the unevenness of the exhaust gas recirculation(EGR) rate of each cylinder. The emissions test system and methodology were established for testing the unevenness of the EGR rates among cylinders of the diesel engine. The EGR rates in the intake manifold and the engine operating conditions were determined by analyzing the universal emissions characteristic curves. The EGR rate of each cylinder was explored by measuring CO2 concentrations under steady state conditions

the influence of uneven EGR rate of each cylinder on the emissions performance was analyzed

and the range was determined of difference of the EGR rate of each cylinder by which the set raw emissions target can be reached. The purposes were satisfied of reducing the raw emissions of the diesel engine and alleviating the difficulty and cost of matching an after treatment system to meet the emissions requirements of China Ⅵ by controlling the difference of the EGR rate of each cylinder.