| Compared with ethanol,2,5-dimethylfuran as a renewable energy has the advantages of high energy density,high boiling point and insoluble in water.And in recent years,the production cost has been greatly reduced due to breakthroughs in preparation technology.As a biomass fuel that can replace gasoline,2,5-dimethylfuran has very broad application prospects.This paper independently designed and built a 2,5-dimethylfuran/air hightemperature and high-pressure constant-volume combustion bomb experimental system,and carried out the 2,5-dimethylfuran/air laminar premixed combustion experiment under different equivalence ratios,initial temperatures and initial pressures.The propagation characteristics of 2,5-dimethylfuran/air laminar premixed flame,the evolution of flame front structure,instability and acceleration characteristics are studied.At the same time,it also provides the basic combustion data required for the simulation calculation.First,we independently designed and built a high-temperature and high-pressure constant-volume combustion bomb experiment system,which mainly includes: the combustion bomb and premix tank main body,intake and exhaust system,heating and insulation system,ignition system and data acquisition system.The initial temperature of the experiment can reach 250℃,and the initial pressure can reach 2MPa.It can be used for combustion experiments of a variety of liquid fuels.And by collating and calculating the experimental data,the 2,5-dimethylfuran/air laminar combustion velocity is compared with the previous laminar combustion velocity data,and it is found that the consistency is very good,which verifies the reliability of the experimental system.Combined with the high-speed schlieren system,different equivalent ratios,different initial temperatures and different initial pressures were developed.2,5-dimethylfuran/air laminar premixed combustion experiment.Use MATLAB program to extract the key information of the flame image,and get the main information such as flame radius,area and contour circumference.Use CHEMKIN software to calculate the density before and after the flame burns.Parameters such as stretching propagation velocity,non-stretching propagation velocity,laminar burning velocity and laminar mass burning velocity are calculated.The effects of equivalence ratio,initial temperature and initial pressure on the stretching propagation velocity,non-stretching propagation velocity,laminar combustion velocity and laminar mass combustion rate of 2,5-dimethylfuran/air laminar premixed flame are studied.The front structure evolution and instability of the 2,5-dimethylfuran/air laminar premixed flame during the development and propagation process are studied.The study found that with the increase of equivalence ratio,initial temperature and initial pressure,the flame front surface cracks and cell structure gradually increased.By comparison,it is found that within the experimental measurement range(R=6～25mm),the cell structure on the flame front is mainly concentrated in the experimental conditions with high equivalence ratios,high temperatures and high pressures.The effects of Markstein length,density ratio,flame thickness and critical radius on the stability of 2,5-dimethylfuran/air laminar premixed flame under different equivalence ratio,initial temperatures and initial pressures conditions are also studied.The acceleration characteristics of 2,5-dimethylfuran/air laminar premixed flame are studied.Studies have found that the acceleration phenomenon is often at the time when many cracks have been split on the front of the flame,but the uniform cell structure has not yet formed,and the corresponding radius of acceleration is smaller than the critical radius.The acceleration characteristics are quantitatively analyzed through the acceleration index and the type overweight.The results show that the larger the equivalence ratio,the higher the initial temperature,and the higher the initial pressure,the greater the acceleration index and the classification excess,and the stronger the acceleration characteristics of the flame. |
