LUBRICATION BEHAVIOR OF THE POE/R452A MIXTUREAT DIFFERENT SLIDING VELOCITIES UNDER STARVED LUBRICATION CONDITIONS

Abstract

There are no international standards guiding tribological testing in oil-refrigerant mixtures. The conditions fortribological tests, including sliding velocity, are chosen arbitrarily. The article presents an attempt to examinethe influence of the sliding velocity of friction pair elements on the coefficient of friction and lubricatingproperties of compressor polyester oil (POE) and its mixture with the R452A refrigerant (POE/R452A) understarved lubrication conditions. The R452A refrigerant is currently widely used in transportation refrigeration.The authors’ original test procedure with the use of a model block-on-ring type friction pair was applied toevaluate the lubricating properties of the oil-refrigerant mixture. Tests were conducted in three operationalsituations: no lubrication, starved lubrication with POE oil, and starved lubrication with the POE/R452Amixture. In each case, the tests were performed at different sliding velocities and the same sliding distance.A series of tests was also conducted where the load was increased in steps by 20 N to determine the relationshipbetween the coefficient of friction, sliding velocity, and load on the friction pair.The results support the potential use of higher sliding velocities and the reduction in test duration. For starvedlubrication with the POE oil and the POE/R452A mixture, the differences in wear at specific velocities forthe same sliding distance reached up to 30%, and the rankings of lubricating properties at different velocitiesremained unchanged.