Systematic Measurement of Hydrocarbon Fuel Droplet Burning Rate Constants and Ignition Delays

摘要

In this experimental study, a new data reduction approach was developed for measuring droplet burning rate constants that automatically finds the most linear part of the d-squared curve for the longest period of time. The approach, here called K beta, was developed in response to the observation that burning rate constants can vary by up to 10%, depending on the reduction approach used, especially for fuel types such as nonvolatile simple hydrocarbons and kerosenes. To evaluate this new method, burning rate constants were measured for 10 fuels, including two alcohols, four simple hydrocarbons and four kerosene blends. The measured rates ranged from 0.74 to 0.94 mm2/s, typically grouped by similarities in thermophysical properties of the fuel types. Notably, K beta and its simpler equivalent Kend,5,70 yielded burning rates with small statistical uncertainty (approximate to 0.006 mm2/s average) across all fuels and were associated with the highest coefficient of determination for all K measurement approaches, indicating that these two methods are viable options for improved consistency in measuring burning rate constants. In addition, a systematic method is presented for measuring ignition delays tau ign using a short-duration plasma source for ignition. The ignition delays ranged from 65 to 110 ms for most fuels, correlating well with the fuel boiling temperature. Combined, this work provides baseline data and data reduction tools suitable for future droplet combustion studies.