The Vibration Analysis Of Simulating Experimental Table Of Hydraulic Valve Train

Valve train is an important source of diesel engine noise.Nowadays the low vibration design of valve train mainly focus on traditional cam-rocker structure,neglecting deep research on vibration of hydraulic valve train.With the development of requirement from acoustic quality of powers and legislation,the vibration of hydraulic valve train has become an important research subject.This thesis aims to explore the characteristics of excitation and vibration,especially,the mechanism of percussion force and flow field characteristics while valve is seated.The specific study is as follows:Firstly,based on CY4102 BC diesel engine,the hydraulic valve simulation experimental table was designed and built.Meanwhile,the geometric model and flow field model of hydraulic valve were established.With computational fluid dynamics,three-dimensional steady calculation is carried out for valve under the condition of different lift and constant trigger pressure,obtaining steady-state pressure distribution which is taken as the initial condition to lay a foundation for the subsequent transient calculation.Considering difficulty that the valve seated force only serves as fluid boundary condition,Fluent cannot be directly used to calculate,the solution method of "fluid calculation and experimental test combined simulation" is proposed.The valve movement process is divided into two stages: before and after the seat.Firstly,researching before sitting,the force equation of driving piston of valve before sitting is established by UDF dynamic grid technology,which is used as fluid motion boundary to calculate valve lift curve and compare with experiment.On the premise calculation is consistent with experimental results,the post-seating stage is studied.A section of data after seat taken from measured lift curve to fit and compile into UDF.the dynamic equation of valve after seating is constructed on the basis of original equation to realize the real dynamic simulation of whole process that valve opening and closing.Analyzing the transient flow characteristics inside the valve,the internal and external excitation forces in running process of valve are finally solved,focusing on slapping force while valve seated.The finite element model of hydraulic valve simulation experimental table which is modified by comparing with the modal experiment results is established,loading the contact force of valve seat into finite element model uniformly.The vibration response of structure is calculated to analyze vibration characteristics of hydraulic experimental table under seat contact excitation force by transient dynamic method in time domain.Finally,the correctness and feasibility of analysis method in this thesis are verified by comparing with measured data,which provides a reference for research on vibration and noise reduction of diesel hydraulic valve train.