The Critical Spontaneous Combustion Boundary Relevance Research Of Single Component Fuel

In order to solve the problems of the existing combustion modes,such as nitrogen oxides-particle contradiction,unstable combustion process,narrow application conditions and many incomplete combustion products.The research group proposes the concept of “Reaction Controlled Homogeneous Mixture Sequence Auto-Ignition Combustion Mode” based on early research results and other scholars similar research.The key to the realization of this new combustion mode is to study the critical spontaneous combustion boundary of a single component fuel,to find several kinds of fuels with large differences in spontaneous combustion and to make up homogeneous gas mixture.The micro-field fine control is used to control the fuel the critical thermal-chemical atmosphere appears to achieve this mold of combustion.The premise is the enough difference of a typical single component fuel homogeneous mixed gas critical spontaneous combustion boundary.In this paper,several kinds of single component fuels(methanol,ethanol,n-butanol,n-heptane)were used in the different air-fuel ratio,different fuel volume concentration and different air volume concentration to research the critical auto-ignition temperature.Firstly,solve the problems encountered in the previous work,that is the continuing decline of the cylinder pressure after mixed gas combustion and the phase inconsistency of the pressure curve and the temperature curve.The method is to take the temperature curve and the pressure curve to fix each other to solve the problem.Before and after burning with temperature correction pressure,and pressure to correct the temperature at the instantaneous combustion.According to the ideal gas state equation to carry out the pressure value and temperature correction calculation.The pressure after the correction does not decrease over time,and the pressure after the combustion of the fuel is higher than the pressure before the ignition,and the temperature in the post-combustion incendiary bomb is higher than that before the combustion and the amount of the product is more than the reactant,It is reasonable to burn before.Secondly,establish an analysis index of the typical single component fuel critical ignition temperature boundary condition.Based on the factors influencing on the spontaneous combustion temperature of single component fuels,the boundary conditions of the ignition temperature of the single component fuels are established,that is the combustible mixture equivalent ratio,the fuel carbon atom volume concentration of the combustible mixture,the total oxygen atoms volume concentration of the combustible mixture and the molecular carbon chain structure of the fuel.The experimental data shows that the self-ignition temperature of the fuel is influenced by the carbon chain structure of the fuel molecules,and the change of the fuel concentration or the volume of the air in the carbon chain is greater than or equal to four.Are not sensitive,because the number of carbon atoms and more fuel combustion occurs when the reaction path and the number of carbon atoms less fuel combustion path is also lessFinally,according to the established analysis index,the influence on boundary condition of the critical spontaneous combustion temperature is analyzed.For each study of the fuel,the test to take three sets of test program:(1)keep the air volume unchanged,and to change the amount of fuel by changing the equivalent ratio to determine the fuel spontaneous combustion temperature under different amount of fuel.(2)keep the same amount of fuel unchanged,and to change the amount of air by changing the equivalent ratio,which measured the spontaneous combustion temperature of the combustible mixture under different air consumption.(3)to change the amount of fuel and air simultaneously under the stoichiometric ratio,test fuel spontaneous combustion temperature changes regulation when fuel and air volume change.The conclusions are as follows:1.The spontaneous combustion temperature of n-heptane does not change with the equivalent ratio(about 280 ?)whether in the constant air volume group or in the unchanging fuel quantity group.methanol can only ignite spontaneously in the narrow range of the equivalent ratio of 0.6-1.4 in the constant air volume group,and the change of auto-ignition temperature is also large,from 499 ? at ? = 0.6 to 469 ? at ? = 1.4,that is it is changed by 6.4%;spontaneous combustion phenomenon of methanol occurred in the equivalent ratio of 0.6-2.0 in the constant fuel quantity.And the critical self-ignition temperature of methanol increases with the increase of the equivalent ratio after the equivalent ratio is greater than 1.0.The differences in the results of the two groups is due to the larger fuel volume concentration in the constant air volume experimental group,and the self-ignition temperature of methanol is more sensitive in the larger fuel concentration.The auto-ignition temperature of ethanol in the scheme of fixed air volume is also large with the equivalent ratio,while the auto-ignition temperature change of ethanol is not large in the unchanged fuel quantity scheme.Whether in the fixed air quantity group or fixed fuel quantity group,the temperature varies of the n-butanol is not obvious with the equivalent ratio.2.The critical self-ignition temperature of n-heptane is insensitive to the change of the fuel carbon atoms volume concentration.The critical self-ignition temperature of the three kinds of alcohol fuels decreases with the increase of the fuel carbon atoms volume concentration in the chemical equivalent ratio.The sensitive volume concentration area rank to the critical self-ignition temperature of the three kinds of alcohol is n-butanol> ethanol> methanol,that is,n-butanol has a significant change in the critical auto-ignition temperature when the fuel carbon bomb volume concentration is high,when the atomic volume concentration is low,the critical auto-ignition temperature of methanol changes obviously.3.At the stoichiometric ratio,the critical auto-ignition temperature of n-heptane does not change with the change of oxygen atom volume concentration,while the critical auto-ignition temperature of the three alcohols decreases with the increase of oxygen atom volume concentration.The influence of fuel volume concentration on critical spontaneous combustion temperature is much greater than that of air volume concentration,and the differences between the two is an order of magnitude.In the constant fuel quantity group,the critical auto-ignition temperature of n-heptane remained essentially unchanged,but the critical auto-ignition temperature has a increasing tendency with the increase of oxygen atom volume concentration.When the air is over,n-heptane is not easy to ignite spontaneously.When the equivalent ratio is less than 1,the case of insufficient air,the three kinds of alcohol fuel need a higher temperature to support their spontaneous combustion.When the equivalent ratio is greater than 1,the critical self-ignition temperature of the fuels decrease as the oxygen atom volume concentration increases and then remains constant.Through the three sets of scheme,when the oxygen atomic volume concentration reaches a certain level,the spontaneous combustion temperature of methanol has not been affected by the change amount of fuel.4.As the number of carbon atoms increases,the critical auto-ignition temperature of the fuel tends to decrease,and the critical auto-ignition temperature variation of the fuel is narrowing.The larger the number of carbon atoms contained in the fuel molecular formula,the wider the volumetric concentration of fuel carbon atoms in which the fuel can run smoothly.