Exergy diagnosis of the combustion process in a Diesel engine

Abstract

In this work a single-zone and two-species exergy diagnosis model is developed and applied for characterizing the operation of a diesel engine from a secondlaw standpoint. The model allows to study the in-cylinder process during the closed-valve period, and to determine how the exergy is distributed and what is the exergy potential of the losses. Experiments were carried out in a test bed equipped with an automotive, direct injection, turbocharged diesel engine operating at several loads. Combustion diagnosis was made from instantaneous in-cylinder pressure signal and the main operation parameters of the engine were measured in order to guarantee steady state. Irreversibilities and exergy distribution throughout the process were determined. It was found that combustion is the main source of irreversibilities. Results show that exergy destruction decreases as load increases, which mainly led to an increase in the exergy of exhaust gases. Additionally, the cogeneration potential of the engine was identified, exhibiting significant differences between first and second-law results.