Validation of a phenomenological model and investigations of effects of injection timing in four-stroke direct-injection diesel engine performance

Abstract

One of the world’s efforts is to mitigate the greenhouse effect, and the increase in thermal efficiency is a way to reduce the CO2 emissions. Models of simulation of thermodynamic nature are useful to predict the performance of internal combustion engines. Once set up with operational characteristics, the simulation is relatively fast and does not need complex and expansive experimental apparatus to set the engine’s best parameters. The aim of this study is to build a phenomenological model to predict the performance of diesel engines, to evaluate its characteristics with experimental results, and propose thermal improvements by testing new operation parameters. In addition, this simulation model contains a blowby routine, unusual in thermodynamic models. First, a direct-injection diesel engine equipped with turbocharger and aftercooler was simulated under four operating test conditions: (1) max load and speed; (2) max speed and partial load; (3) max load and partial speed; (4) partial load and speed. The results show the experimental heat-release profile by the combustion is essential for the good agreement between the simulation and the experimental results, whose relative errors were −0.766, −0.148, −1.126, and 1.371% to the indicated shaft power for the Tests 1–4, respectively. In a second investigation, the engine simulation was made by varying the start of injection (SOI) of the Test (1). Advancing the SOI from 4.8° to 28° BTDC, the specific fuel consumption decreased 18.26%, and the indicated shaft power increased 22.37%. This article shows that a regular commercial diesel engine has a large field to improve the thermal performance, and the thermodynamic simulation fits well to support the decision of an engine project.