Piston Cooling Nozzle Oil Jet Evaluation Using CFD and a High Speed Camera

摘要

Piston cooling nozzles/jets play several crucial roles in the power cylinder of an internal combustion engine. Primarily, they help with the thermal management of the piston and provide lubrication to the cylinder liner and the piston's wrist pin. In order to evaluate the oil jet characteristics from various piston cooling nozzle (PCN) designs, a quantitative and objective process was developed. The PCN characterization began with a computational fluid dynamics (CFD) turbulent model to analyze the mean oil velocity and flow distribution at the nozzle exit/tip. Subsequently, the PCN was tested on a rig for a given oil temperature and pressure. A high-speed camera captured images at 2500 frames per second to observe the evolution of the oil stream as a function of distance from the nozzle exit. An algorithm comprised of standard digital image processing techniques was created to calculate the oil jet width and density. Finally, the results of the CFD model were compared to the key metrics identified by the high-speed imaging and were found to be in good agreement. It was discovered that the percentage deviation between the CFD model's velocity profile along a line at the PCN exit and a perfectly uniform, symmetric profile was a good indicator of the oil jet quality. Therefore, the CFD method has been validated using experimental observations, so it can be implemented to optimize novel PCN concepts early in the development process long before the stages when hardware is procured.