Power recovery of a variable nozzle turbocharged diesel engine at high altitude by response surface methodology and sequential quadratic programming

Based on a review of the research methods about diesel engine performance recovery at high altitude and an experimental investigation, by optimizing variable nozzle turbocharger (VNT) and fuel supply system calibration parameters a novel method is proposed to enhance the performance of a turbocharged diesel engine at high altitude. At an altitude of 1920 m, four calibration parameters deeply affecting performance of the diesel engine were selected at the rated power condition, that is, injection quantity, injection timing, injection pressure, and VNT nozzle opening. In order to reduce thermal load of the diesel engine running in the plateau environment, reasonable coded levels of Design of Experiments (DoE) factors were chosen, and an experimental design matrix was selected based on the Box–Behnken design. The interaction effects of the four calibration parameters on engine performance were investigated using the response surface methodology. Power recovery optimization was carried out by means of sequential quadratic programming under a minimum smoke limit and durability constraints. The results show that this performance optimization method can effectively recover engine performance at high altitude. Moreover, it can, to an extent, alleviate the problems such as deterioration of fuel consumption and high thermal load induced by the rise in elevation. With optimized calibration parameters, the rated power of the diesel engine at an altitude of 1920 m proved to be recovered to that at sea level, and there was an increase of brake specific fuel consumption by less than 3% compared with that in the plain area, which met the performance and durability requirements for general turbocharged internal combustion engines at altitudes lower than 2000 m.