Estimation of Piston Surface Temperature During Engine Transient Operation for Emissions Reduction

Abstract

Piston surface temperature is an important factor in reducing harmful emissions in modern Gasoline Direct Injection engines. In transient operation, the piston surface temperature can change rapidly, increasing the risk of fuel puddling. The prediction of the piston surface temperature provides the means to significantly improve multiple-pulse fuel injection strategies by avoiding fuel puddling. It can also be used to intelligently control the Piston Cooling Jet (PCJ) which are common on modern engines. Considerable research has been undertaken to identify generalized engine heat transfer correlations and to predict piston and cylinder wall surface temperatures during operation. Most of these correlations require in-cylinder combustion pressure as an input, as well as the identification of numerous model parameters, these render such an approach impractical. In this study, the authors have developed a thermodynamic model of piston surface temperature based on the Global Energy Balance (GEB) methodology, which includes the effect of PCJ activation. The advantages are the simple structure, no requirement for in-cylinder pressure data, and only limited experimental tests are needed for model parameter identification. Moreover, the proposed model works well during engine transient operation, with maximum average error of 6.68% during rapid transients. A detailed identification procedure is given. This, and the model performance, have been demonstrated using experimental piston crown surface temperature data from a prototype 1-liter 3-cylinder turbocharged GDI engine, operated in both engine steady-state and transient conditions with an oil jet used for piston cooling turned both on and off.