| The rotary engine is another high-efficiency internal combustion engine other than the reciprocating piston engine.Because of its simple structure,few parts,smooth operation,and multiple fuels,it is widely used in military and civilian fields.In recent years,with the traditional petroleum energy crisis and environmental pollution problems becoming intensifying,a variety of new alternative fuels have been widely tried on rotary engines,such as natural gas,hydrogen,biodiesel and so on.Among them,natural gas is considered as one of the ideal fuels for rotary engines as its rich reserves,clean and high efficiency.However,the narrow combustion chamber and unidirectional flow of the rotary engine will hinder the rapid propagation of flame,and when natural gas is burned,the slower combustion speed of natural gas will further exacerbate this problem.The problem of slow combustion of natural gas can be effectively solved by blending hydrogen but it cannot be ignored that the inherent structure and operation mode of the rotary engine have led to the inevitable leakage of the radial seal.Once the two gas fuels gas and hydrogen are applied,the leakage of fuel will become worse.Therefore,it is of great scientific significance and practical value to improve the performance of this type of rotary engine by deeply analyzing the working process of the natural gas hydrogen-doped rotary engine considering air leakage of apex seals.In this paper,a side-ported natural gas hydrogen-doped rotary engine is taken as the research object.By analyzing the existing research dynamics,it is clear that the focus of the research should be on the formation and combustion mechanism of the mixed gas in the cylinder to improve the combustion efficiency of this type of engine.To this end,a numerical simulation model of a side-ported natural gas hydrogen-doped rotary engine considering radial seal leakage is established,and the model is verified by experimental data of PIV(Particle Image Velocimetry)flow field test and cylinder pressure test.On the basis of this numerical simulation model,the effects of operating parameters and structural parameters on the flow field,combustion and emissions in the cylinders of natural gas hydrogen-doped rotary engines are further studied systematically.The research achievements with academic significance and practical value obtained during the research process are as follows:(1)A numerical simulation model of a side-ported natural gas hydrogen-doped rotary engine considering radial seal leakage is constructed.First,in order to account for the radial seal leakage between the three combustion chambers,the simultaneous modeling and meshing of the three combustion chambers of the rotary engine are realized.Then,based on the FLUENT software,the dynamic grid program is completed,the three-dimensional grid motion in the combustion chamber is realized,and the appropriate turbulence model,ignition model,combustion model and simplified chemical reaction mechanism are added to construct A numerical simulation model of a natural gas hydrogen-doped rotary engine considering radial seal leakage.Finally,the experimental data of PIV test flow field results and cylinder pressure test results verify the reliability of the model.(2)The formation rule of the three-dimensional flow field in the combustion chamber under the action of radial seal leakage is revealed.The results of numerical simulation research show that the effect of the size of the leakage gap on the flow field: During the intake and compression stages of the engine,the small leakage gap will enhance the vortex intensity at the front end of the combustion chamber and delay the vortex dissipation time of the entire combustion chamber;The large leak gap will destroy the vortex at the front end of the combustion chamber and accelerate the dissipation of the vortex in the entire combustion chamber.Then,it is further found that with the same leak gap,the effect of the above leak gap on the flow field will decrease with the increase of the rotation speed.(3)The influence of hydrogen injection position on the formation and combustion process of the mixed gas in the cylinder is obtained.With the change of the injection conditions of natural gas,the results of numerical simulation show that when the position of the hydrogen nozzle on the cylinder is at the intersection between the long axis of the cylinder profile and the cylinder profile,it can be Hydrogen is mainly distributed in the middle and front of the combustion chamber,and the concentration around the spark plug is high,while the leakage of hydrogen to the adjacent combustion chamber is small.This hydrogen distribution is conducive to the formation of fire nuclei early in the combustion process and accelerates the rapid combustion of natural gas located in the front of the combustion chamber during flame propagation.(4)The influence of hydrogen injection angles on the formation and combustion process of the mixed gas in the cylinder is clarified.Under the condition that the injection conditions of natural gas are unchanged,and when the hydrogen nozzle is located at the intersection point between the long axis of the cylinder profile and the cylinder profile itself,a numerical simulation study shows that in order to distribute as much hydrogen as possible in In the middle and front of the combustion chamber and to ensure that the concentration around the spark plug is higher,then as the timing of hydrogen injection changes,the angle of hydrogen injection should also change accordingly.Specifically: when hydrogen is injected during the intake stroke of the engine,the injection angle should be-30 °.When hydrogen is injected during the compression stroke of the engine,the injection angle should be + 60 °.Some theoretical guidance for the improvement of combustion efficiency of sideported natural gas hydrogen-doped rotary engines are provided in this paper.At the same time,the research methods and conclusions presented are also valuable to the development of other fuel rotary engines. |
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