An experimental technique for determination of intrinsic burning rate constants of liquid fuels

Abstract

The burning rate constant of the droplets of a liquid fuel solely characterized by the thermo-physical properties of the fuel and the oxidizer is an intrinsic characteristic of the fuel. The classical quasi-steady approach enables estimation of such a parameter in a highly idealized scenario with a range of simplifying assumptions. Furthermore, this quasi-steady method requires the knowledge of the thermo-physical properties of the fuel along with the expected adiabatic flame temperature. The current study utilizes droplet combustion experiments in natural gravity for the estimation of the intrinsic burning rate constants of pure fuels. A semi-empirical technique has been utilized to establish a correlation between the experimental and classical quasi-steady burning rate constants. The dimensions of the droplet flame were an important aspect of the model. The experiments have been conducted in a quiescent atmosphere of ambient air with droplets of n-heptane, n-decane, and nitromethane. Quartz fibers with a range of diameters were utilized to support the droplets and obtain a variation of the initial droplet diameters. The observed variation of the burning rate constant was recognized to be the result of the augmentative effects of natural convection and the conductive heat transfer through the supporting fiber.