Theoretical And Experimental Study On The Pulse Combustion Of Low Concentration Gas

It is very important to exploit CBM vigorously which has high calorific value and lowpollution. This item plays an important role and significance for optimizing energyconsumption structure and promoting development of environment and economy coordinately.However, because of the extremely low methane content, it is difficult to using the lowconcentration mine gas efficiently with regular combustion way. According to this issue, thepaper puts forward a new combustion way to improve the utilization rate of low concentrationmine gas using the pulse combustion theory. The combustion characteristic of lowconcentration mine gas is researched through the ways of theoretical study, numericalsimulation and experimental study.Theoretical study: Gas surge model has been established and according to RayleighCriteria, the mechanism of the steady operation and driven of pulsating combustion arestudied. And the mathematical ignition model of low concentration mine gas is establishedbased on the basic theory of pulse combustion that involves working principle,thermodynamics cycle and thermal sound coupling mechanism. And the NO controlmechanism is discussed during the pulse combustion process. In addition, with the integrationof fuel properties and experimental conditions, it determines the type of a pulseburner-Helmholtz. According to pulse burner design principles, it designs a low density gaspulse combustion device of the rated power which is10kW. The system includes:measurement of gas distribution system, combustion systems and data acquisition systems.Numerical simulation: The mathematical model、physical model and solution model areestablished which suit to the low concentration gas.The automatic control about pulseentrance boundary conditions is realized by preparing UDF entry control procedures. And thecombustion characteristics are researched about low concentration mine gas whose gascontents are lower10%.The numerical simulation results indicates that in a pulse cycle, thepressure field、velocity field and temperature field distribution also represent cyclicalvariation. And the changing trends satisfy the pulse principle; When the intake entrance is90°the temperature field distribution is the most homogeneous; NO distribution is lowerthan the conventional combustion significantly, and mainly is prompt NO; The temperature ofcombustion chamber raises with the temperature rising of air preheating.Experimental study: In order to research the combustion characteristics, the pulsatingcombustion experimental device and the orthogonal experiment scheme are established. Theexperimental simulation results indicates that whether is the pulse condition can be judged through combustion flame voice、the pressure of combustion chamber and the air voiceself-priming phenomenon; By orthogonal experiments, it finds the index pulse parameterswhich impact the burning effectiveness; On10kW rated load, gas pulse combustion of lowconcentrations of the best parameter combination is that Heat load is8kW, tail pipe length is2000mm, and gas concentration is8%.All in all, Compared experimental results with numerical simulation results, both has thesame changing regularity on combustion characteristics: The longer the tail length is, thelower the pulse frequency is; The higher gas concentration is, the higher combustiontemperature is; As the heat load increases to8kW, combustion temperature is maximum. Itverifies the accuracy of numerical simulation results.