High Pressure Ignition and Combustion Characteristics of Single Drop Fuel

With hanging drop method under normal gravity condition, the droplet of heptadecane in high pressure ignition and combustion phenomena is detailedly researched. Embedded thermocouple inside the droplet and high-speed cameras record the droplet temperature variation and droplet development images. The experiment shows that with environment pressure increasing, the fire region of droplet reduces and tends to liquid drop surface, the carbon smoke generated in burning flame increases and flame width reduces; in subcritical pressure environment, the temperature curve of droplet after the corresponding mutation of burning maintains a flat process; in supercritical pressure environment, the temperature of droplet rises at a high rate, and the interface temperature gets over the fuel critical one. When ambient pressure is less than 0.6 time of critical pressure, the ignition temperature of droplet increases rapidly with ambient pressure and stops near critical pressure, but when environmental pressure is higher than 1.2 times of the critical pressure, the ignition temperature of droplet continues to increase with the increasing pressure. The droplet combustion time under subcritical pressure decreases rapidly with the increasing ambient pressure, and the droplet combustion rate is controlled by the phase equilibrium; under supercritical environment pressure, droplet combustion time no longer continues to decrease but tends to stable, droplet phase transition does not exist in this period, and the diffusion coefficient begins to affect combustion rate.