Research On N-hexane Explosion Basing On Aviation Fuel Safety

As the basic fuel of aircraft power plant,people has paid more and more attention to aviation kerosene with the development of aviation industry.Meanwhile,there is also a great danger of fuel leakage in the transportation and storage.Volatilization after fuel leakage produces steam and air to form a combustible mixture,which frequently cause deflagration and result in catastrophic consequence.Therefore,research on the explosion characteristics and basic principles of aviation fuel has significance to control and reduce the occurrence of such types of accidents,as well as improve the fuel combustion efficiency.However,the composition of fuel is quite complex,and the property also has a great relationship with types making the experimental and numerical study on the properties of fuel very difficult.At present,using alternative fuels with physical and chemical properties similar to aviation kerosene has been considered as quite a simple and effective method.N-hexane is a good alternative fuel since it has a similar ignition point to aviation fuel and is volatile.A constant volume combustion chamber suitable for liquid fuel was designed and built.Using this system,the explosion pressure of premixed mixtures under different conditions were measured with a pressure sensor The development of flames were studied by the use of schlieren and high-speed camera.The explosion and laminar burning characteristics of n-hexane over the pressure range of 60-100 kPa,temperature range of 353-393 K,and the equivalence ratio range of 0.7-1.7 were investigated.Results show that the maximum explosion pressure and rates of pressure rise versus equivalence ratio share a similar trend at all initial conditions,which first increase and then decrease gradually.The explosion pressure and maximum rate of pressure rise show an uptrend trend with the increase in initial pressures or decrease in initial temperatures.However,the non-dimensional explosion pressure is independent of the initial pressure.The Markstein length of premixed fuel is positively correlated with the equivalence ratio and initial pressure.So that the flame front stability decreases gradually,but the Markstein length has little relation with the initial temperature.With the increase in the fuel concentration,namely,when the equivalence ratio changes from 0.7 to 1.7,the laminar burning velocity presents an uptrend firstly and then gradually decreases.The laminar burning velocity reaches its maximum value near the stoichiometric ratio.Furthermore,when the initial pressures decreases or the initial temperatures increases,the laminar burning velocity of aviation kerosene increases gradually.To study the influence of hydrogen on the flame combustion and explosion performance of n-hexane,experiments over the temperature of 353 K,the pressure of 100 kPa,and equivalence ratio of 0.8-1.7 were carried out in a cylindrical combustion vessel.It is found that both of the explosion pressure and rate of pressure rise depend on fuel concentration.With the increase of hydrogen addition,the maximum values of peak pressure shifts to the leaner mixture.For lean and rich fuels,the explosion behavior of hydrogen on premixed mixtures is opposite,and the influence on the maximum explosion pressure and rate of pressure rise is more obvious for excessively lean or rich fuels.Meanwhile,adding hydrogen to the fuel obviously increases the unstretched flame propagation speed and the laminar burning velocity of n-hexane/hydrogen premixed mixtures.