Steady state counterbalance valve modeling with the inuence of synthetic ester oils using CFD

Abstract

This study looks in details at the effects of synthetic esters being applied to a counterbalance valve from the perspective of a system engineer. There is limited literature on the subject of applied synthetic esters and as such limited unbiased sources for information. This creates reluctance against the use of these fluids in sectors and regions with no prior experience and knowledge of what to expect. This study expands the applied literature by investigating a commercially available valve using commercial oils, a basic synthetic ester, a fully saturated synthetic ester and a typical mineral oil type for benchmarking. The investigation is based on both computational fluid dynamics and experiments and is performed at 20, 40 and 60 deg. The product is a steady-state valve model including fluid dynamics and a parameter-dependent Coulomb friction. The CFD model reveals minimal oil type dependence in the resulting fluid dynamics model with flow forces and discharge coefficient being the same for mineral oil and esters. The experiments show that the esters primarily produce different levels of hysteresis with up to 40% less and 15% more hysteresis. The friction investigation showed that the relationship between hysteresis and pilot pressure was different for all oil types, and that the relationship between hysteresis and temperature was similar for all oil types. With full knowledge of mineral oil and the oil specific knowledge of the hysteresis and pilot pressure relationship at a single temperature, ester hysteresis was predicted with better than 88% accuracy across the three temperatures.