Optimal Design of Clearance in Fuel Injection Pump

Dept. of Mechanical Engineering, Pusan National University (Received March 21, 2015; Revised July 15, 2015; Accepted July 16, 2015)Abstract − In the study, a design process for ensuring optimal clearance in a fuel injection pump(FIP) is sug-gested. Structure analysis and hydrodynamic lubrication analysis are performed to determine the optimal clear-ance. The FIP is simulated using Hypermesh, Abaqus 6.12 to evaluate the reduction of clearance when themaximum supply pressure is applied. The reduction in clearance is caused by the difference in the deformationsbetween the barrel and plunger. When the deformation of the plunger is larger than that of the barrel, a reductionin clearance at the head part occurs. On the other hand, the maximum clearance reduction equals the maximumdeformation in the stem part, because the deformation of barrel does not occur in this region. The clearance ofFIP should be designed to be larger than maximum reduction of clearance in order to avoid contact between theplunger and barrel. In addition, the two-dimensional Reynolds equation is used to evaluate lubrication char-acteristics with variations of viscosity, clearance and nozzle for a laminar, incompressible, unsteady state flow.The equation is discretized using the finite difference method. The lubrication characteristics of FIP are inves-tigated by comparing film parameter, which is the ratio of the minimum film thickness and surface roughness.The optimal clearance of FIP is to be designed by considering the maximum reduction in clearance, lubricationcharacteristics, machining limits and tolerance of clearance. Keywords − fuel injection pump(연료분사펌프), clearance(간극), deformation(변형), minimum film thickness(최소유막두께)