Experimental study on diesel engine exhaust gas recirculation performance and optimum exhaust gas recirculation rate determination method.

In order to study the exhaust gas recirculation (EGR) performance of marine diesel engines, a venturi high-pressure EGR device was established to overcome the exhaust gas reflow problem based on a certain type of turbocharged diesel engine. The EGR performance test is accomplished and an optimal EGR decision-making optimization method based on grey correlation coefficient modified is proposed. The results show that the venturi tube EGR can basically meet the injection requirements of high-pressure exhaust gas and achieve good results. Through the venturi tube EGR, the NO X emissions reduce significantly with the maximum drop of 30.6%. The explosive pressure in cylinder reduces with the EGR rate increases and the cylinder pressure curve shows a single peak at low-speed conditions and double peaks at high-speed condition. However, the fuel consumption rate, NO X and smoke have been negatively affected. Due to small samples, the traditional evaluation method is difficult to determine the optimal EGR rate reasonably, while the proposed method can effectively solve this problem. It can weaken the shortcomings of subjective judgement and greatly improve the rationality of decision-making results.

Preferred Revascularization Strategies in Patients with Ischemic Heart Failure: A Meta-Analysis.

Clinically, coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) is generally used to treat patients with ischemic heart failure. However, the optimal treatment strategy remains unknown. This study examined the efficacy of the two coronary revascularization strategies for severe ischemic heart failure by using a meta-analysis. Studies comparing the efficacy of CABG and PCI were obtained from PubMed, EMBASE, Google Scholar and Cochrane Central Register of Controlled Trials (CENTRAL). The quality of each eligible article was evaluated by Newcastle-Ottawa Quality Assessment Scale (NOS), and the meta-analysis was performed using Stata version 12.0 software. Eventually, 12 studies involving 9248 patients (n=4872 in CABG group; n=4376 in PCI group) were subject to the meta-analysis for subsequent pooling calculation. The pooled hazard ratio (HR) [HR=0.83, 95% CI (0.76, 0.90), P<0.001; heterogeneity, P=0.218, I2=22.9%] of CABG compared with that of PCI revealed a statistical superiority of CABG to PCI in terms of the long-term mortality. Furthermore, CABG showed more advantages over PCI with respect to the incidence of myocardial infarction [HR=0.51, 95% CI (0.39, 0.67), P<0.001; heterogeneity, P=0.707, I2=0%] and repeat revascularization [HR=0.40, 95% CI (0.27, 0.59), P<0.001; heterogeneity, P<0.001, I2=80.1%]. It was concluded that CABG appears to be more advantageous than PCI for the treatment of ischemic heart failure in the given clinical setting.

Optimized modelling and application of exhaust gas recirculation performance evaluation of turbocharged diesel engine.

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.