Numerical & Experimental Investigation of Flow through Pressure Relief Passage of Gerotor Oil Pump of a Passenger Car Diesel Engine

The main challenge in designing the oil pump for gasoline & diesel engines is to optimize the pressure relief passage. Pressure relief passage is critical from design point of view as it maintains the oil pressure in the engine. Optimal levels of oil pressure and flow are very important for satisfactory performance and lubrication of various engine parts. Low oil pressure will lead to seizure of engine and high oil pressure leads to failure of oil filters, gasket sealing, etc. Optimization of pressure relief passage area will also reduce the power consumed by the pump. The Pressure relief system for this study consists of Pressure relief valve, spring, retainer, pressure relief passages. It is difficult to directly measure the flow through the pressure relief passage and is arrived based on the drop in flow at the delivery port. Numerical tool will be handy to predict the flow through the pressure relief passage and this can be used to optimize the flow through the bypass passage. In the numerical investigation, various pressure relief valve profiles were considered to predict the flow. In addition to this, spring load was considered to understand the dynamic operating conditions which also simulate the actual engine conditions. The oil pressure to the pressure relief passage was varied with a pre-determined time step, which corresponds to various engine operating speeds. The numerically predicted flow through the pressure relief system for different pressure relief profiles were validated with experiments indirectly and good correlation was found between numerical and experimental results. This investigation helped in optimizing the flow rate of the pump and maintaining the engine pressure at all speeds. The optimized profile reduced the flow rate by 5% and still in excess of the engine requirement with the current profile. This will directly benefit in reducing the power consumption.