Study On The Characteristics Of Catalytic Ignition Of Methane/Moist Air In Micro Channel

Micro devices and systems include sensors, mav, regulator, the micro medicalinstruments, micro pump, and micro motor. They have been widely applied in areassuch as national defense, scientific research, medical and industrial applications. Microburner energy density is much higher than traditional energy supply. Thereby microscalecombustion research interest has attracted the majority of scholars at home and abroad.It has become a hot topic. But the micro burner has many problems such as lowconcentration fuel is difficult to fire, difficult to fire rapidly, and difficult to achievestable combustion. These problems must be solved rapidly. This article puts forward toresearch on methane/wet air catalytic ignition process in the micro channel. Researchmainly adopts the numerical simulation method to study characteristics of methanecatalytic ignition temperature, methane limit ignition, combustion stability, catalyticignition transient state, and methane catalytic combustion under the constant walltemperature. The operating conditions (CH4/O2equivalent ratio, flow and size of reactor)and water vapor which has big effects on methane catalytic ignition characteristics arestudied by experimental method.Aiming to the problems of combustion instability and ignition difficulty，this paperadopt numerical simulation and experiment to study methane catalytic ignition process.Results indicate that: As the CH4/O2equivalent ratio reduces, inlet velocity increases,and Wall catalyst load density reduces in the numerical simulation, the ignitiontemperature increases correspondingly.They need higher preheat energy to catch fire. Asinlet pressure increases with constant fuel air volume flow, ignition temperatureincreases. It goes against to fire. The addition of water vapor results in a higher ignitiontemperature of methane. And it needs more heat to catch fire. At last, it needs toimprove preheating temperature to make the fuel catach fire with high surface heat lossfor microscale combustion. The ignition temperature of the experimental and numericalresults is similar. Ignition can occur at lower temperature in larger size of reactor withconstant volume flow. In the transient process of iginition, As the CH4/O2equivalentratio increases, the ignition will happen faster. As the inlet velocity increases resulting inshort residence time, the methane will be on fire faster, and stable time is shorter. Asinlet pressure increases leading to a high ignition temperature and unit heat quantity, theignition happen faster.The addition of water vapor delays methane catalytic ignition.The bigger the water vapor concentration is, the more the methane catalytic ignition delays.Adopt numerical simulation method to study the influence of property parametervalues of different wall material on methane catalytic ignition. Results indicate that: AsWall thermal conductivity increases, methane catalytic ignition extreme equivalent ratiodecreases, and fire interval expands. In low speed section, the main reason is the heatloss which decided to shut down. In high speed section, blow out limits flameout whichincreases sharply. When inlet velocity is high, increase of methane concentration canobviously increase the methane combustion stability. Wall temperature and inletvelocity have a bigger influence on the catalytic oxidation of methane under theconstant wall temperature.When the temperature does’t reach the ignition temperature,increased equivalent ratio and inlet velocity contributes to methane catalytic oxidation.Using experimental method to analysis the influence of water vapor on themethane catalytic ignition characteristic, the following conclusions are obtained. Aswater vapor concentration increases, T10and T90improve accordingly. Ignitiontemperature of methane is525℃without water vapor. When water vapor concentrationis5%,10%,15%and20%, the ignition temperature is respectively575℃,590℃,610℃and645℃. When the wall temperature is550℃, the methane conversion hasobviously decreased in the long time operation because of water. The increased walltemperature which breaks the water vapor adsorption/desorption equilibrium weakensthe influence of water vapor on the catalytic oxidation of methane.This article’s research is helpful to improve and optimize the micro combustor.And it promotes depth study of microscale combustion technology. It has certainacademic significance and engineering value in the design of micro devices.