Courtesy of SHW

Modern internal combustion engines have a very high oil supply requirement, due to piston cooling needs and oil-consuming devices such as camshaft adjusters, for example. Modern vehicles also have increased demands for passenger comfort and silent and smooth operation, which can be met with add-on components like balance shafts, used to stabilize the engine during operation. With the addition of an item such as this, the already limited available space inside the engine compartment is reduced even more. To cope with these issues, SHW, the German pump manufacturer, has developed an integrated oil pump for an add-on balance shaft system, for the next generation of four cylinder engines.

To address the large oil supply needs of the engine in a compact space, a pump with a small diameter but larger than average length was developed to be positioned inside the engine block. The cut away picture shows the oil case with the oil pump housing (gray), the rotor set (dark green and blue), and the pump cover (light green). The balance shaft, not shown, is driven by a chain, as is the pump shaft (pink). Due to the high speed of the pump rotor (up to 6000 rpm), the design of the oil intake and the internal structure of the pump are critical to the effectiveness of this unit. If the oil f low through the intake and the interior of the case is not optimal, a restricted and nonuniform flow will develop, reducing the efficiency of oil replenishment in the pump.

Contours of velocity magnitude in a plane that cuts through the middle of the pump and the intake pipe

Beginning with a 3D CAD geometry of the pump internals, SHW carried out a numerical investigation of the intake (suction) pipe to the pump. This pipe splits so that it can feed oil into the pump from both ends of the rotor set, and the challenge for the SHW engineers was to ensure that as much oil as possible would be fed evenly into the pump, even when operating at high speeds. By performing a series of CFD simulations using FLUENT, they were able to optimize the design of the intake channel. In doing so, the point at which the pump throughput begins to saturate was increased from 4000 rpm to approximately 5000 rpm. In addition, an increase of about 15% in the oil flow rate through the pump was achieved at speeds greater than 4500 rpm, making the design well suited to the targeted operating regime.

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