The geometric parameters of the clearance seal between the plunger and the pump barrel in the stratified oil pump and the structure of the seal groove have an impact on the flow blocking effect.In order to explore the influence of the width and number of sealing groove on leakage under the finite length pump gap,the control equation of produced fluid flow in the gapm was established based on Naiver-Stokes equation,and the numerical simulation on clearance flow field were carried out based on computational fluid dynamics.Taking the widely used FCCYB38-28A stratified oil pump as an example (there are three kinds of matching clearances,which are 0.045,0.095 and 0.145 mm respectively),the law of the sealing effect changing with the size and number of sealing grooves under different pump clearances was analyzed.The results show that the leakage rate of 0.045 mm sealing gap fluctuates with the width of the sealing groove,and firstly decreases and then increases.The leakage rate of 0.095 mm and 0.145 mm sealing gap decreases with the increase of the width of the sealing groove.Under 0.145 mm sealing gap,the leakage rate decreases with the increase in the number of sealing grooves.However,due to the permeability effect caused by the increase in the number of sealing grooves,the decrease of the leakage rate gradually tends to be flat.Under the given sealing length and 0.145 mm sealing gap,the clearance seal has good blocking effect when the sealing groove number is 21 and the sealing groove size is 1.5 mm×1.5 mm.