Abstract
Aimed at the problem of exhaust gas recirculation (EGR) performance evaluation and optimal EGR rate determination of turbocharged diesel engines, an optimized decision-making method, based on grey theory and entropy weight, was proposed. The internal combustion pressure, fuel consumption rate, NOX, CO and smoke were selected as the decision-making targets and the initial decision-making model was established based on the traditional grey decision-making theory. According to the characteristics and optimization requirements of EGR, the optimal compromise between combustion and emission performance is proposed to transform into decision-making target weighting problem, then an optimized subjective weighting method based on expert scoring and grey relational analysis is proposed. Finally, the entropy weight method was used to solve the objective weight and the optimized multi-objective grey decision-making model was established, which can not only weaken the human error of subjective empowerment, but also fully explore the intrinsic relationship of the evaluation indexes. At last, an optimization simulation platform for EGR performance evaluation based on MATLB/GUIDE was designed and established. The results show that the optimization simulation platform can effectively improve the efficiency of simulation calculation, which is more convenient for practical engineering applications. The optimized method can successfully realize EGR performance evaluation and optimal EGR rate determination under different working conditions. The decision-making result was consistent with the present EGR control strategies, which provide a new research idea for EGR performance optimization.
Highlights
Exhaust gas recirculation (EGR) is the main measure to reduce NOX emissions of diesel engines
An improved multi-objective grey decision-making method based on subjective and objective comprehensive weighting is proposed to solve the problem of EGR performance evaluation and optimal EGR rate for turbocharged diesel engines
The best compromise between diesel engine combustion and emission performance is transformed into weighting problem between evaluation targets and the weight optimization method is proposed based on the grey relational analysis and entropy theory, which can meet the operating characteristics of the turbocharged diesel engine and make the decision-making results more reasonable
Summary
Exhaust gas recirculation (EGR) is the main measure to reduce NOX emissions of diesel engines. Based on the test data, different researchers establish various evaluation criteria by subjective judgement to achieve the best EGR rate and make a whole-working-condition optimal EGR rate MAP. Zhang [8] proposes taking the particulate matter as not exceeding the original machine as the basic principle; taking into account the degree of increase in fuel consumption, improvement of NOX emission and other comprehensive factors, high EGR rate should be selected at low-load conditions and small EGR rate should be selected at high-load conditions Other researchers, such as Du [9], are using a similar approach. The modelling and simulation efficiency can be improved effectively by the optimization simulation platform which is more convenient for engineering applications It extends the engineering application of multi-objective grey decision making, and provides a new idea for EGR performance optimization of turbocharged diesel engines
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