Multi-component heavy fuel drop histories in a high-temperature flow field

Abstract

This study is the latest in a series, conducted at The University of Wisconsin, to elucidate the behaviour of combustible fuel drops. Concurrent analytical and experimental studies of temperature and mass histories during the vaporization, combustion and thermal decomposition of a multi-component liquid-fuel drop in a high-temperature flow field have been performed. The fuel investigated is of residual type, a mixture of heavy liquid hydrocarbons. Irregular burning of drops of these fuels has been attributed mainly to asphaltenes and partly to unstable resin components. In the analytical work, temperature-dependent mean properties of both the liquid drop and the boundary layer of air/ fuel vapour mixture have been employed. Assumptions have been adopted to simplify the analytical model. Four governing differential equations in combination with three boundary conditions are reduced by the Zeldovich method to two simultaneous ordinary differential equations for drop mass and drop temperature histories. These are solved numerically by the Runge-Kutta method on a CDC 3600 computer. A simple extension gives a breakdown of the heat balance. The analytical predictions improve on previous predictions using constant properties 1 . It is found that the heat of decomposition and the total heat input to the drop per unit initial drop mass during the liquid phase are unaffected by airstream temperature and initial drop size in the range studied.