Forward Engineering Research On Cylinder Bore Deformation Of Automotive Diesel Engines

Closely linked with engineering practices, this paper uses the widely-used 493 automotive diesel engine as the research object and analyzes comprehensively an important issue in the forward engineering development of automotive diesel engines—the mechanism, evaluation methods and optimization designing of cylinder bore deformation. The objective is to solve the difficult problem of how to further decrease oil consumption and particulates emission, a thorny problem that domestic enterprises often encounter due to excessive cylinder bore deformation in the development of new diesel engines or the optimization of existing models. The paper is a breakthrough in forward engineering designing, making it possible to gradually improve independent innovation capabilities.The integral contact multi-field indirect coupling method is put forward and an integral contact relation model including the complete cylinder block, cylinder head, cylinder liners, cylinder head gasket and cylinder head bolts is established to avoid the disadvantages of partial model and single component researches. The temperature field of coolant is obtained through the CFD simulation of flow field to reduce the errors arising from boundary conditions given by simple empirical formulas. The temperature field and deformation under thermal stress fields are solved respectively to decrease the computational complexity and the indirect coupling calculation of cylinder bore deformation in mechanical stress fields and thermal stress fields is implemented.Based on the mechanical properties of different parts of the cylinder head gasket and cylinder head gasket loading tests, a non-linear combined model of the cylinder head gasket is put forward to simplify the model as well as reflect the accurate mechanical relationship between the different parts. Through numerical simulation and static measurements of cylinder bore deformation under cylinder head bolt screw pre-moment, the integral contact relation model and boundary conditions are calibrated and verified. On this basis, the simulation of cylinder bore deformation in mechanical stress fields and thermal stress fields is conducted respectively. By utilizing the comprehensive optimization designing scheme devised according to the results of coupling simulation, the clearance between the cylinder liner and the piston of the new 493 prototype diesel engine is reduced effectively. The performance and emission tests show that the optimized prototype engine has a 10% increase in maximum torque and 35% decrease in oil consumption compared with the original engine. ESC test results show that the particulates emission is 0.09 g/kW?h, far below 0.13 g/kW?h, the required level of the third phase national emission regulation.Both the simulation and experimental measurement results are total cylinder bore deformation. This research shows that the total deformation can be divided into two kinds: displacement deformation and out-of-roundness deformation. Displacement deformation and part of out-of-roundness deformation can be made up by the clearance between the connecting rod and the piston or the elastic forces of the piston rings, thus unable to cause the failure of the sealing circular-bands of the piston ring . Based on the fast Fourier transformation of the cross-section deformation of the cylinder bore, an evaluation parameter of cylinder bore deformation, the maximum effective deformation ?r e ffect?max, is defined. Using this parameter, the effects of bore deformation on oil consumption and particulates emission can be predicted much more accurately, making it possible to establish an effective approach to cylinder bore deformation in forward engineering, an approach of great practical value in engineering.