Analysis Of Steady Performance For Diesel Using Two Unequal Turbo Chargers

One of the most effective measures to increase specific power is to increase boost pressure, but with high-pressure ratio, high efficiency turbocharger adoption, the diesel engine and supercharger matching contradictions become even more prominent. Turbocharger engine can not meet all the needs of the operational state, resulting in the part-load torque inadequate and heat load increases. In order to improve the part-load performance of diesel engine, as to better meet the performance requirements of marine engine , a marine V-type diesel engine with two unequal size turbochargers using sequential turbo charging (STC) was proposed and the feasibility of three- area supercharging was investigated in this paper.Firstly, mathematics description of physical subsystem of supercharging diesel engine is developed. Zero-dimension model of the working process in cylinder and one-dimension unsteady flow mode of the gas flow in intake and exhaust systems whose partial differential equations were discredited by finite volume method have been used. According to exhaust turbine supercharger balance conditions, the exhaust turbocharger mathematical model has been established.Secondly, the conventional turbocharged diesel engine steady-state Simulation model has been established by simulation software GT-Power. With the model, a calculation to the conventional turbo charging has been performed first, and the result tends to be in agreement with the experimental one. Then, the simulation model of the STC system with two unequal size turbochargers has been established and more than one group unequal size turbochargers, which were mainly from T-series turbocharger of Garrett Company, have been matched to 234V12 diesel engine by the cube propeller characteristic. According to the matching line of diesel engine in the compressor map and the performance parameters by the propeller characteristic running, the better groups of turbochargers have been selected.Finally, the load characteristics, limiting characteristics of the matching successfully diesel engine in smaller turbocharger, larger turbocharger, and two combined turbocharger status have been calculated, analyzed and compared. Based on both load and limiting characteristics, universal characteristics in the three states have been drawn. The results indicate that with two unequal size turbochargers using STC, the scope of power and torque have been enlarged and fuel consumption and exhaust temperature have been decreased in the low load .This shows that with two unequal size turbochargers using STC technology is an effective measure, which improve the low load status of high P_e diesel engine and further enlarge the scope of the diesel engine operation.