Effect Of Diesel Fuel Blended With The Mixed Alcohols Oxalates Combined With EGR On Diesel Engine Performance

In the context of the carbon peaking and carbon neutrality strategy,the internal combustion engine industry,as a major energy consumer,has the greatest potential in the implementation of energy conservation and emission reduction.In order to alleviate the non renewable energy consumption and environmental pollution caused by burning fossil fuels in diesel engines,this article adopts a new type of oxygenated alternative fuel-mixed oxalate(m MAO),which can be used for diesel engine blended combustion.The physical and chemical properties of m MAO indicate that it can have an impact on the combustion and emissions of diesel engines.Considering that oxygen rich combustion can lead to an increase in NO_X emissions from diesel engines,this article combines exhaust gas recirculation(EGR)technology to study the effect of m MAO/diesel blend fuel on the combustion and emissions of diesel engines.Firstly,using the TBD234V6 marine diesel engine as the original engine,the fuel supply system of the original engine test bench was modified to prepare m MAO/diesel blend fuels with different mixing ratios.Through experiments,the effects of the blend fuel on the combustion and emissions of the diesel engine under different operating characteristics were studied.The results showed that the power and economy were improved,carbon smoke and CO emissions were reduced,and NO_X emissions were increased after mixing m MAO,HC emissions decrease overall but increase relatively at full load;Based on the experimental results,taking into account the power,economy,and emissions of diesel engines,the impact of blended fuels on diesel engine performance is evaluated through a multi-objective optimization evaluation method.Taking the rated operating conditions as an example,compared to the original engine,the maximum combustion pressure of the M30 has increased by 0.16%,the equivalent fuel consumption has decreased by 2.98%,the carbon smoke emissions have decreased by 43.05%,and the NO_X,CO,and HC emissions have increased by 3.04%,4.32%,and 44.38%,respectively;The optimal mixing ratio of m MAO was determined to be 30%.Secondly,based on the original machine,the EGR system is designed and a Venturi tube device is installed to solve the pressure difference problem in the EGR circuit.On the premise of meeting the application and structural requirements of the Venturi tube,combined with the actual situation of the test bench,the basic structure of the Venturi tube is determined through calculation;Based on CFD simulation data of the internal flow field of a Venturi tube,the response surface method is used to optimize its structure;A second-order response surface model was established through Design Expert,and the optimal parameter combination of the Venturi tube structure was obtained after solving.Simulation calculations and analysis of different EGR rates were conducted under this structure,and the results showed that the Venturi tube could meet the required EGR rate;Based on the simulation optimization results,process the Venturi tube and build a bench.Finally,based on the optimal m MAO blending ratio,experiments were conducted to investigate the effect of blended fuel combined with EGR on the combustion and emission characteristics of diesel engines under different operating characteristics.The results showed that the introduction of a small amount of exhaust gas had little effect on the power performance of the diesel engine.However,with the increase of EGR rate,the peak cylinder pressure decreased and the phase shifted backward.The high oxygen content of M30 can offset some of the negative effects brought by exhaust gas.The effect of EGR rate on carbon smoke varies under different loads.Under load characteristics,carbon smoke emissions increase with the increase of EGR rate,while under propulsion characteristics,they first increase and then decrease;And NO_X emissions have significantly improved;CO and HC emissions have increased.Considering the deterioration of power and economy after adopting the EGR system,the reduced fuel consumption rate is taken as the main decision-making objective to determine the optimal EGR rate under different operating conditions,and all comply with the principle of EGR rate control.Taking rated operating conditions as an example,compared to M0 without EGR rate,the maximum combustion pressure of M30 combined with EGR decreased by 2.17%,equivalent fuel consumption decreased by1.17%,NO_X and soot emissions decreased by 47.56%and 36.96%,respectively,CO and HC emissions increased by 17.41%and 53.01%respectively.