Study On Working Process Of Coal Bed Methane Engine Based On Numerical Simulation

Under the premise of increasingly serious energy problems and environmental pollution problems,coal bed methane has the characteristics of high combustion heat value and low environmental pollution after combustion,which can be used as an alternative to traditional fuel.Shanxi Province has a large amount of coal bed methane resources.The rational use of coal bed methane can reduce the direct pollution to the environment.On the other hand,the development and utilization of coal bed methane can reduce transportation costs and increase economic benefits.It is one of the best ways to using coal bed methane as an energy source for power generation.The gas engine generator set has advantages of low construction cost and high power generation efficiency.It is easily to manage and high power generation efficiency.The gas engine can be well adapted to the fluctuation of coal bed gas concentration.In this paper,the coal bed methane engine is taken as the research object.The main working parameters of the engine,the ignition energy and the effect of the double spark plug are analyzed by numerical simulation.The purpose of this work is to provide a reference for the optimal design of coal bed methane engines.Based on the working principle of the engine and the characteristics of in-cylinder combustion,the AVL-Boost and AVL-Fire simulation software was used to establish the first and third-dimensional simulation models of the engine which has provided basic parameters and experimental data.The one-dimensional simulation model and three-dimensional simulation model are verified with the experimental results.In order to improve the accuracy of the simulation,the results of one-dimensional model simulation,such as inlet temperature and pressure,are taken as the boundary conditions of the three-dimensional model simulation.Through the one-dimensional simulation model of the coal bed methane engine,this paper analyzes the whole machine performance of the single-parameter influence and multi-parameter interaction.When the other parameters of the engine are initial parameters,a single parameter such as the compression ratio(7.5-14.5),the ignition advance angle(14°-26°),the air-fuel ratio(15.1-29.2),and the valve overlap angle(12°-32°)is analyzed by the one-dimensional simulation model.And this paper gets the simulation results of the maximum explosion pressure,pressure rise rate,power,gas consumption rate,maximum combustion temperature and discharge temperature by the one-dimensional simulation model.Combined with the variation law of each result,the better compression ratio,ignition advance angle,air-fuel ratio and valve overlap angle are obtained,which is provided as the basis parameter for the optimal design of the engine.The orthogonal experiment method is used to design the three parameters of compression ratio,ignition advance angle and air-fuel ratio.And this paper uses the one-dimensional simulation model to complete the multi-parameter interaction law of engine performance.Combining the power and gas consumption rate in the simulation results,the paper analyzes the above three parameters by the range analysis and the variance analysis.At the rated speed of 1500r/min and the full load conditions,this paper by three-dimensional CFD simulation model analyses the influence of the spark plug ignition energy and the double spark plug position on in-cylinder combustion.This paper,under the conditions of ignition energy and double spark plugs at different positions,analysis in the heat release rate,cumulative heat release,average temperature in the cylinder,average turbulent energy in the cylinder,flame propagation in the cylinder,NOx concentration in the cylinder and NOx generation.And combined with these results,this paper analyses the effects of ignition energy and double spark plugs on the combustion process of the engine.