Performance of a High Pressure Liquid Reciprocating Pump with a PistonCoated with a Thin Self-lubricant Material

摘要

It has been found that the output power and the thermal efficiency of hydrogen fueledengines are increased by the direct injection of hydrogen fuel into the engines. In orderto obtain the high pressure enough for the direct injection onboard, a high pressureliquid hydrogen pump with a self-lubricant material and a radius clearance of 1 to 4micro-meters between the piston and the cylinder is required even when the pump is inthe ambient temperature or in the liquid hydrogen temperature of 20 K. A compositematerial consisting of a 1.5 ～ 2.5 thick self-lubricant resin with carbon fine powdercontained and a ultra-low thermal expansion nickel alloy lined with the resin was usedfor the material of the piston. However, the coefficient of thermal expansion of theresin was subject to change by lot by lot. The change of the coefficient of thermalexpansion was too large to control the radius clearance of 1 to 4 micro-meters. Tocontrol the radius clearance, the composite material was adjusted by measuring theradius clearance in liquid hydrogen whenever the lot of the resin was changed. If thethickness of the self-lubricant resin is small, the change in the radius clearance isexpected to be small enough to neglect the large coefficient of thermal expansion. Abasic experiment was carried out to find an appropriate material which has thecharacter of self-lubrication and low friction coefficient and a method to fix the materialstrongly on the surface of the piston. The material and the method were found. Thiswork here was carried out to find whether the material and the method could bepractically used for liquid hydrogen pumps. This paper shows the performance of thepump, the material coated on the surface of the piston before and after the experiment.