Heat Transfer And Strength Analysis In High Pressure Common Rail Injection System Considering Fluid Structure Interaction

In response to the energy crisis and environmental pollution as well as to satisfy the demand of increasingly stringent emission regulations,It is an effective way to strengthen various aspects of diesel engines to improve its economy performance and emission performance,Therefore,the diesel engine is developing towards the direction of high pressure ratio and high power density,However,with the improvement of those parameters,the thermal load and mechanical load of the components of diesel injection system such as fuel injector and high pressure pipes increase significantly,which poses a challenge to the reliability of diesel engine.Therefore,accurate analysis for the mechanical characteristics of high-pressure fuel pipe and injector heat transfer process is particularly important.First of all,the model of high-pressure fuel pipe is established by SolidWorks,the mechanical analysis of the high-pressure fuel pipe is carried out by the unidirectional fluid-structure interaction method,and then compared with the vibration data,the result shows that high-frequency percussion from the oil pressure is the main reason for fuel pipe rupture.In order to improve the anti-fatigue performance of the fuel pipe,the influence of preload,sealing surface grooving and autofrettage on absorbing highfrequency percussion from the oil the high-frequency impact of oil pressure reduction were investigated respectively.The result shows that before autofrettage,the maximum stress of the oil pipe under working pressure is 328.16 MPa and the maximum stress position is located on the inner wall of the oil pipe;after autofrettage,the maximum stress of the oil pipe under working pressure is 234.64 MPa,and the maximum stress position is transferred from the inner wall to the middle layer of the pipe,the maximum stress decreased by 28.5 %,indicating that autofrettage can reduce the wall stress to extend the service life of the the oil pipe.the general formulas of residual stress distribution and optimum autofrettage pressure are deduced,provides a reference for solving similar problems.Secondly,the coupling model of injector-fuel and cooling liquid is established,the boundary conditions and initial conditions of the actual working conditions were adopted,and the simulation analysis of two rounds of cross-iteration of the injector was carried out,the results show that the temperature of the injector orifice in the highest,the highest can reach 231.1 ?.On the basis of fluid-solid coupling heat transfer analysis,thermal load and mechanical load are considered for the thermal-solid coupling strength analysis,the influence of cooling liquid temperature on the heat dissipation performance was emphatically analyzed,and the temperature of the stress concentration zone was optimized by reducing the inlet temperature of the cooling liquid to strengthen the heat dissipation and structure optimization,results show that the inlet temperature of cooling fluid can effectively reduce the fuel injector temperature,and thus reduce the thermal stress,when the coolant inlet temperature reduced from 75 ? to 35 ?,the highest fuel injector temperature was reduced by 12.93%.On the basis of this,the stress concentration can be reduced effectively by a 1 mm thickening of the joint of the compression cavity flange,and the superimposed stress can be reduced by 18.6% by the optimization of two aspects.