Design And Verification Of Combustion Bomb With Variable Axial Temperature

In order to explore the effect of fuel thermal-physical and chemical atmospheres on the autoignition temperature and flame propagation,this paper developed an axial temperature gradient controllable combustion bomb characterized with precise control of fuel concentration,air concentration,pressure and thermal physical state,and explored the ignition temperature and flame extinguishing temperature of n-heptane in the combustion bomb.Part one.The design of the combustion bomb system.Constant volume combustion bomb experiment system mainly consists of following sections:1.Combustion bomb body.The main body of bomb could be divided into three parts:(1)the body of the bombs,(2)the front cover of the bombs,(3)the rear cover of the bombs.,which is connected with flanges.Considering the process performance of the bomb,the bombs body is also divided into four sections for,and the sections are connected by flanges.The key components have been strength check,meeting the experimental requirements of combustion bomb.2.Combustion bomb heating system.The heating method and strategy of bomb is based on the 3D thermal/flow simulation about model.According to the four-structure of combustion bomb body,the heating system about “one main three auxiliary” is formed.3.Intake and exhaust system.Using the reasonable arrangement of the pressure regulating valve and the pipeline,intake and exhaust system could achieve the goal that supplying the certain concentration air and exhaust the waste gas.4.Date acquisition system.Data acquisition system includes some equipment: K-type thermocouple WRNK-191 model temperature sensor,model PA-15-4-1(K)Voltage Transmitter,model Kistler 6125 B cylinder pressure sensor,model Kistler5015 A charge amplifier,Suzhou Heng Rui Feng monitoring and control technology company developed highspeed acquisition card,Labview PC.Temperature pressure sensor could transfer temperature and pressure into electrical signals.Voltage Amplifier is also known as temperature transmitter,which amplify the temperature sensor electrical signal so that the data acquisition card can identify it.Charge Amplifier amplify the cylinder pressure sensor electrical signal so that the data acquisition card can identify the voltage signal;Data Acquisition Card transform analog signal into digital signal and send the signal to Labview PC;Labview PC receive the signal is displayed by visual means.5.Ignition system.Using the glow plug of diesel engine as the ignition plug of the combustion bomb,the temperature of the head of the ignition plug was measured by the temperature sensor.The requirement of ignition system about measurable plug temperature is designed.6.Fuel supply system.It is designed to ensure the injection pressure by adjusting the pressure of the tank.The pulse width of the injector is controlled by a combination of hardware and software.Both of them work together to complete the fuel supply system that injects the certain fuel into the premix chamber.Part two.The functional verification of combustion bomb.In order to verify the function,the additional experience must be done.1.The verification temperature flied in combustion bomb.Adjust the power of the heating wire to verify the temperature field of the bomb.The experiment shows that the maximum temperature inside the shell can exceed 600 ° C,and the lowest temperature within the bomb can be below 80 ° C.The square of the linear correlation coefficient of the temperature inside the bomb can be higher than 0.8.Based on the above experimental verification,the temperature gradient of the combustion bomb meets the design requirements.2.The supply method of fuel and air.The single fuel injection quantity under different pressures and different injection pulse widths was calibrated by the experimental method,and then the intake pressure and the mass of fuel can be calculated according to the experimental operating condition.The certain mass fuel is supplied into the bomb by controlling the injection pressure and the pulse width.Fuel injection pulse width and number of fuel injection is controlled by electrical control system including the Freescale Microcontroller,roller,driver circuit and Lab view.3.The test of autoignition temperature and quenching temperature.The preliminary research on combustion of n-heptane under various concentrations of air and fuel in a combustion bomb shows that low concentrations of n-heptane can not spontaneous even at a high temperature.As the increasing of pressure and " Air-fuel ratio ",the n-heptane can be ignited by the ignition plug and the flame propagates in the axial direction.The phenomenon of the end of flame spread can occur at temperature range 176℃ to 105℃ on operation condition 5bar-0.6,8bar-0.5 and 11bar-0.4.With the increasing of pressure and " burn-air " equivalence ratio,the mixture can be spontaneous combustion at relatively low temperatures,and the flame propagation process will not be interrupted.