Visualization And Analysis Of The Characteristics Of High-pressure Gas Jets For A Natural Gas Engine

Internal combustion engine on the consumption of energy is increasing, emissions of environmental pollution has become increasingly serious.The natural gas engine has got people’s attention with its good economy, low NOx and particulate matter emissions.The mixture of gas and air directly determines the combustion and emissions performancenatural gas engine,but the change law of gas injection characteristics is not sufficient now.The research is often about macroscopic properties of gas spray direct injection in cylinder under the condition of high pressure,lack of study on gas injection in inlet. And people only consider the influence of the injection pressure and back pressure on the gas characteristic.In fact,the nozzle aperture,working medium,the accumulator cavity volume of nozzle will have an effect on gas injection characteristic.For the natural gas engine,the insufficient power,CO and HC emissions,the poor fuel economy,the difficulty of improving rule alternative rate and other issues also is closely related with gas injection characteristics.Therefore, this paper uses the mathod of experiment combined with simulation to carry out research on basic visualization problems of natural gas engine injection characteristics.As the actual gas injection process is very complex, often accompanied by sophisticated air movement, it is difficult to directly recognize the law of development, so constant volume vessel and visualization Inlet are used respectively as an experimental test environment to build a test platform to study the the gas injection characteristics. The visualization measurement of the gas injection process is based on schlieren method, and the collected schlieren images are automatically processed through MATLAB programming, access to gas injection parameters.In the measurement of fuel gas jet characteristics with constant volume vessel, the gas jet characteristic of single hole nozzle was studied with different diameters, injection pressure,back pressure, medium and conditions. The development regularity of characteristic parameters of gas were obtained such as jet penetration distance, cone angle, jet velocity and proportion of frontal area, global equivalent ratio. Mean while, in the test with visualization of air inlet, the influence of different injection pressure and inletair velocity to the jet characteristics of porous nozzle were analyzed based on the visual image. It is shown that the flow characteristic of fuel gas outlet in the experiments were impacted by parametric variation of gas in the pressure storage chamber, therefore the vary regularity of mass flow rate of fuel gas out of the spout is analyzed by simulation.The study about gas jet characteristics of natural gas engine, which based on the visualiz ation experiment and simulation analysis, provide the basis for the establishment of gas injecti on numerical model, and make preparations for the development of efficient and clean natural gas engines.