| An experimental study of the ignition of preheated fuel sprays, with particular consideration of dependence upon temperature and pressure, was performed. The tests were conducted in a stainless steel cylindrical chamber located in an oven, provided with quartz windows for optical access in the axial direction. Spray formation and ignition were observed by high-speed schlieren cinematography with simultaneous measurements of chamber pressure and injector needle displacement. Ignition events were studied for air temperatures of 600 to 875 K and pressures of 4.4 to 28.2 atm. Fuel temperatures prior to injection were between 100 to 200 K lower than the air temperatures in the cell.; The laboratory measurements of the induction period displayed an Arrhenius type behavior with an activation temperature of 9032 K and a pre-exponential coefficient equal to 2.69 x 10('-8) seconds. In addition, a relative insensitivity to initial pressure was observed. Comparison with other experimental studies indicated that preheating the fuel significantly decreased the induction period by diminishing vaporization and mixing times. The low temperature ignition events were similar to an homogenous charge type of combustion while the high temperature events displayed a diffusive burning of the fuel jet.; Thermodynamic properties for the fuel, dodecane, and additional other heavy hydrocarbons were derived. This required a numerical implementation of the extended principle of corresponding states. The algorithm developed for this purpose used a grid containing up to two thousand data points for the determination of coefficients in the equation of state. Internal energy, entropy, isothermal and isobaric compressibilities, and the speed of sound were thus calculated for normal paraffins, from octane to hexadecane, and the results presented in both graphical and tabular form. Accuracies for the derived results were estimated by comparison with data from other works for octane and hexadecane which indicated agreement to within five percent for the specific volume, enthalpy, and entropy. |
