Study On Growth Characteristics Of Cavitation Bubble In Throttling Grooves Of Hydraulic Valve

Cavitation is one of the most common and important noise-induced factors in hydraulic components. It directly affects environmental protection and comfort of the hydraulic system. In this thesis, theoretical analysis, numerical simulation and experimental study are used to investigate the relationship between two typical structures of throttling grooves and the growth laws of cavitation and bubbles. A simplified grooves model is proposed, which is able to maintain the interior pressure characteristics. Based on numerical simulation, a kind of estimation method of bubble size is proposed as well. Numerical simulation and test results show that the growth of bubble and cavitation is mainly correlated with minimum pressure, the back pressure of outlet boundary and the flow time though the region near minimum pressure. The main content of this thesis:In chapter 1, the background and significance of this thesis is presented. The history and current research progress on hydraulic steering system of wheel loader are reviewed. Lastly, the main research subjects are presented.In chapter 2, based on the theory of bubble and cavitation dynamics and the mathematic flow models of two typical grooves, theoretical analysis of growth law of canvitition and bubble is carried out.In chapter 3, two simplified models of typical grooves are proposed. Based on the models, numerical simulations of the interior pressure field in grooves are carried out. A kind of cavitation flow visualization equipment is designed, by which the cavitation flow visualization of one type of sloping groove is obtained. The results show that cavitation is chiefly appeared near the corner of the groove and its size is concerned with minimum pressure and the back pressure of outlet.In chapter 4, the main factors of grooves determing bubble scale are investigated. A kind of estimation method of bubble size is put forward. Analyzing results show that the numer of bubbles is increased with low minimum pressure and large size of shear flow region. Maximum radius of bubble is relatived to the flow time through the region near minimum pressure.At the end, some conclusions in this thesis are summarized and the future research proposals are suggested.