Study On Performance Influence Of Natural Gas Engine Based On On-line Methane Value Measurement

In response to increasingly stringent emission regulations and the challenges of energy transition,natural gas fuel is widely used as an alternative fuel for internal combustion engines due to its superior physical and chemical properties.However,due to the in-situ difference of natural gas fuel and the variability of the use process,the concentration composition of natural gas fluctuates.The influence of the change in the characteristics of natural gas fuel on engine performance is something that internal combustion engine manufacturers and end users want to avoid.Methane number is an index to evaluate the anti-explosion performance of natural gas and the change of component concentration.In order to solve the influence caused by the fluctuation of fuel component concentration on the engine,the methane value as its evaluation index must be measured online.First,build a methane concentration measurement platform based on TDLAS technology,and innovatively build a multi-component concentration online measurement system based on the principle of multi-wavelength absorption difference.After multiple sets of test gases,the accuracy meets the test requirements.Through the interpretation of the ISO/TR22302:2014 "Natural Gas-Methane Value Calculation" report,the relationship between the multi-component concentration of natural gas and the methane value is explored,and a methane value calculation model is proposed,and the application scope of the model is restricted to make the model The calculation result is very close to the results of Cummins and W?rtsil? methane number calculation software,and the calculation error is≤2%.Subsequently,a bench test was carried out on the YC6K295LN-C30 natural gas engine of Yuchai Company,and the fuel methane value was calculated on the basis of measuring the concentration of the fuel components used in the test,which provided boundary conditions and model verification for the establishment of the whole machine simulation model.Using GT-power software to build a simulation model of the whole machine,introduced the modeling process and theoretical basis of important components.Compared with the bench test data,the calculation results of the established simulation model of the whole machine have a higher model accuracy.Finally,using the built simulation model of the whole machine,the influence of methane number on engine performance was studied.The simulation selects 9 groups of natural gas fuels with methane values ranging from 66.51 to 93.8,and divides them into low(65<MN≤75),medium(75<MN≤85),and high(MN>85)regions based on the methane value.As the methane value increases,the maximum explosion pressure and average effective pressure in the cylinder decrease.The methane value ranges from 66.51 to 93.8.The maximum explosion pressure under A working condition is reduced by 2.82%,and the average effective pressure under D working condition is reduced by 8.88%(From 16.032 bar to 14.724 bar);in terms of knock characteristics,as the value of methane increases,the knock index decreases significantly,from 66.51 to 93.8,the knock index decreases from 159.35 to85.34 under D working conditions,a drop of 46.44%;According to the difference in methane value of natural gas,reasonable adjustment of the ignition advance angle can effectively reduce engine knock.The ignition advance angle of low methane value fuel should be delayed by 10° on the basis of the original 41° BTDC,and the best ignition advance angle is 31°BTDC;Summarize the MAP chart of methane value and average effective pressure under different equivalent knock lines.Through the analysis of MAP,it can provide data for the control system to suppress engine knock under the known natural gas methane value and the average finite pressure in the cylinder refer to.