Influence Of Gradient Magnetic Field On NO_x Formation Characteristics In Methane Laminar Burning

In recent years, with the increasing depletion of traditional fossil fuels, as a new clean fuel,natural gas gradually replace fossil fuels, and has been widely used in industrial and civil field.The NO_Xproduced in the natural gas combustion process will be a serious threat to the ecologicalenvironment and people’s health. Methane is the main component of natural gas, so the NO_Xcontrol for methane combustion is necessary. In the current, the main NO_Xcontrol technologyhas been applied effectively in the industrial field, but not in the civilian areas.In this paper, with themethane laminar diffusion flame as the research object, the gradient magnetic field was generated inthe flame zone through a solenoid placed around the flame. The NO_Xformation characteristics ofmethane laminar diffusion flame were researched under different flow, burner and gradientmagnetic field. The research can provide theoretical basis and technical support for combustionoptimization, flame shape prediction and NO_Xcontrol by using gradient magnetic field.Under the special combustion conditions of applying gradient magnetic field around themethane laminar diffusion flame. The flame sizes under three burner and four flow conditionswere analyzed. Results have shown that the flame length and width are not only depend on theburner inner diameter and methane flow, but rely on the value of gradient magnetic field. Theflame width is positive proportional to the value of gradient magnetic field and the flamelength is inversely proportional to the value of gradient magnetic field. As a result, the gradientmagnetic field can be used to control the shape of the flame and to guide the size design of thecombustion chamber.Through the studies on the effects of gradient magnetic field on the temperature distributionof methane laminar diffusion flame under different conditions, it is found that as the action ofparamagnetic force produced by the gradient magnetic field on the oxygen around the flame, theoxygen will move to the larger magnetic field gradient area and form an downward oxygen flowaround the flame. The flow will promote mixing of methane gas and air, and lead the combustionproducts to leave the reaction zone timely. As a result, the combustion conditions are improvedand the methane fuel combustion is promoted. The flame temperature is proportional to thevalue of gradient magnetic field. The gradient magnetic field provides another effective methodfor the optimization of combustion conditions and efficient combustion. Further analyzing the NO_Xformation of methane combustion in different conditions underthe effect of gradient magnetic field, it is found that in a large magnetic field gradient area, theamount of NO_Xis reduced and the reduction is inversely proportional to the value of gradientmagnetic field under the gradient magnetic field. As the additional flow to the oxygenproduced by the gradient magnetic field, the concentration of OH radicals in the flame areaincreases. The OH radical is an important antioxidant, which can both inhibit the formation ofNO and directly restore NO into other substances. In a word, it is pregnant to explore thegradient magnetic field as a new method to control the NO_Xin the combustion process.