分会场

第十届内燃机可靠性技术国际研讨会

摘要

Previous research on the flow and heat transfer characteristics of cooling gallery inside the piston mainly highlights in-line en-gine applications. Nevertheless, with regard to pistons arranges at a certain spatial angle in V-shaped multi-cylinder diesel engine, the change of the angle between the direction of gravity and the direction of piston motion will lead to the changes of the two-phase flow and heat transfer characteristics inside the piston cooling gallery. For the sake of further investigating the oscil-lating heat transfer process of the cooling gallery at different spatial angles, some gallery simulation models in group A and B at spatial angles of -90°, -45°, 0°, 45° and 90°, respectively, are established, considering the influence of piston spatial angles and the position of the oil inlet and outlet. The buoyancy model is adoped to represent the effect of gravity in the simulation models. The change rules of the oil charge ratio (OCR) and heat transfer coefficient (HTC) of cooling gallery are explored and the oscil-latory heat transfer characteristics of the gallery at different spatial angles have been studied by means of the numerical investiga-tions. The results show that at engine speed of 1000 r/min, both the OCR and HTC of the piston galleries in group A gradually decrease with the increase of the spatial angle. Whereas in the case of group B, the OCR of the piston galleries go down as the spatial angle decreases and approaches 0°, likewise the HTC. Due to the cooling oil is motivated by the gravity, the steady-state oil charge ratio (SOCR) of piston gallery A1 (-90°) reaches as high as 63%, but the SOCR of model A5 (90°) reduces to 34%. The amplitude of instantaneous HTC (IHTC) change rate of model A1 (-90°) reaches up to 23.27%, and the amplitude of model B1 (-90°) reaches to 11.52%. At high engine speed, there is no apparent difference in the flow and heat transfer characteristics of the cooling gallery in terms of each spatial angle. Especially when the engine speed exceeds 2000 r/min, the amplitude of the IHTC change rate is within 5% in group B. Therefore, the influence of gravity needs to be considered in the piston design of multi-cylinder diesel engines, when the piston is not moving in the vertical direction and the engine speed does not exceed 2000r/min.

关键词

iesel engine; piston gallery; spatial angle; flow and heat transfer characteristics.

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