Numerical And Experimental Study On Axial Vibration Of Poppet Valve

Poppet valve is widely used in hydraulic system, as it has a lot of advantages, such as simple structure, better sealing, quick response, larger pressure-flow coefficient and less susceptibility to contaminant. But the vibration, noise and cavitation it causes enormously limit its application. Nowadays, with the development of hydraulic technology towards high-speed, high-pressure and high-power direction accompanied with impending energy crisis, the advantages of poppet valve are reconsidered. Meanwhile the researches on the vibration, noise and cavitation of poppet valve are drawing more attention from academia and industry.At present, research on poppet vibration hasn’t had a comprehensive consideration of pipeline effect. This thesis focuses on poppet vibration on the basis of considering pipeline effect, and proposes a practical method of structural parameters optimization to depress poppet valve vibration. At the same time, a preliminary study is conducted on the chaotic vibration of poppet valve. The outline of this thesis is as follows:In chapter1, the background and significance of this subject are introduced. The status of research on poppet vibration is reviewed, then the content of this thesis is specified. At the end, the experimental system and the test object are presented.In chapter2, the physical model of self-excited vibration of poppet valve is established, and its mathematical model is fully built, including pipeline effect, volume effect, hydrodynamic force, etc. Then, its governing equations are derived as the basis of further research.In chapter3, local stability of poppet valve is analyzed by linearization techniques of the governing equations. Especially, the strong nonlinear pipeline model is rationally simplified, and the linearized equations for flow entrance pipeline and pressure entrance pipeline are discussed separately. The stability map for a certain poppet valve is derived using the Routh Criterion, and the map is verified by experimental results. The effects of the main structural parameters of the valve system on the stability maps are studied, and some practical methods of structural parameters optimization to depress poppet valve vibration are proposed, including smaller damping orifice in the piston, larger kinetic damping of the poppet, smaller poppet chamber volume, larger spring chamber volume, shorter pipeline, among which smaller damping orifice diameter is a effective method to depress poppet valve vibration.In chapter4, a Matlab/Simulink platform is built to simulate poppet valve vibration according to its governing equations, and finite difference method is used to realize the partial differential calculators in spatial dimension. The effect of different damping orifice diameter in the piston on poppet vibration is simulated using the Matlab/Simulink platform, which is verified by experimental results. Qualitative and quantitative analysis are conducted for the chaotic phenomenon during poppet vibration simulation. Vibratory waveforms, phase plane path and bifurcation diagram are used to conduct qualitative analysis for the chaos, while its largest Lyapunov exponent is calculated by utilizing the method of Wolf, which is used to conduct quantitative analysis.In chapter5, the research work of this thesis is summarized with further prospects.