A method to determine ignition delay times for Diesel surrogate fuels from combustion in a constant volume bomb: Inverse Livengood–Wu method

In this work a method to determine the ignition delay of Diesel surrogate fuels using data from a constant volume combustion bomb is presented. The studied fuels are n-heptane (a common PRF) and a mixture of 50% of n-heptane and 50% of toluene (in mass) because both fuels have been proposed as Diesel fuel surrogates under HCCI. There are different concepts of spontaneous ignition times in engines or other devices. Auto-ignition times are experimentally obtained in a constant volume combustion bomb or in compression ignition engines, for variable conditions of pressure and temperature. In this work they are obtained in a combustion bomb using four different criteria (pressure, mechanical vibrations, OH* and CH* chemiluminescence emissions). The paper describes an original approach based on an inverse Livengood–Wu method to obtain the ignition delays (as a function of pressure and temperature) from the auto-ignition times. The obtained expressions for the fuels and their mixtures are compared with those of other authors with a reasonable agreement.