Research On Forward Design And Strength Optimization Of A National Ⅴ Three-Cylinder Diesel Engine Block For Micro Car

In order to improve the competitive power of the enterprise, expand the coverageof small diesel engine platform, and respond to the "micro-car diesel", the keydemonstration project of China, we developed a1.0L three-cylinder diesel engine forone of the manufactories who has their own brand, on the basis of their1.5Lfour-cylinder diesel engine. The engine we developed meets the "auto-compression-ignition, gas ignition engines and automotive exhaust emission limits andmeasurement methods (National5stage)"(hereinafter referred to National5)emissions regulations.Because of the poor NVH character of three-cylinder engine, the balance shaftsystem and transmission device were increased to satisfy the mini passenger vehiclefor comfort requirements. As per the requirement of National5emission regulation,the strength and the stiffness of an engine body should be increased. However, afterbeing added some relevant structures of balance shaft hole, the power line of bothsides of the body would be asymmetric, which coursed the declines of the enginebody’s strength and the stiffness. So we carried out the forward design focusing onthis problem.First of all, around the development of ideas of reducing the cost and expandingthe low emission diesel engine platform, under the forward system designrequirements, the1.0L three cylinder diesel engine cylinder bore, stroke, crank radiusand other basic boundary were decided. On this basis, we confirmed the height of thecylinder bore and crankcase contours through motion envelope, movementinterference checking and some other methods, and then carried the block waterjacket, lubricating oil and oil return channel original designs. The NVH character hadalso been optimized when the balance system formed with the crankshaft, flywheel,and the balance shaft belt wheel was designed through balance calculation. Accordingto the balance shaft dimensions after optimization, we increased some relevantstructures of the balance shaft hole, arranged corresponding balance shaft lubrication,optimized the oil return channel of the body balance shaft sides, to create theconceptual design model of the three-cylinder body.Secondly, according to the top down design flow of the body, there are three steps we did. I Analyzed and studied the conceptual design model of the body bychecking its stiffness. II Tested and verified the stress distribution and fatigue strengthof the main bearing wall. Main bearing wall was more complex part of the body whobaring the force, and especially after being added some relevant structures of balanceshaft hole, the two sides of the main bearing wall would be asymmetric. So we had tooptimize the main bearing wall according to above reason. III Simulated thedeformation of cylinder bore under the action of the thermal stress and mechanicalstress. As the cylinder bore deformation directly affected the engine oil consumption,power loss and fuel consumption and other parameters, we controlled the deformationwithin the allowable range by calculation for the cylinder bore according to fluid solidcoupling, to satisfy National5.At last, we made the detailed three-dimensional block drawing, considering thedraft type and other factors. As per it, the two-dimensional one was drawn, and weguided to manufacture the1.0L three cylinder diesel engine model. Now this newdeveloped engine was being conducted the preliminary combustion development.External characteristic test data showed that when the calibration was3600rpm,power reached43.8kW, which met the design index. While maximum torque appearsat2000rpm, the value was135.95Nm and the lowest fuel consumption rate under fullload is217g/kW·h. In general, each performance index of the prototype reached orexceeded the target value.