Atomization and Sprays, Vol.21, No.3, 221-235, 2011
IMPACT OF PHYSICAL PROPERTIES ON PRIMARY BREAKUP FOR A DIESEL NOZZLE CONFIGURATION
Fuel-dependent jet breakup was investigated by resolving the microscopic and macroscopic structures of a spray leaving a diesel nozzle orifice. Liquid structures and their corresponding velocities were analyzed using a light-scattering technique in combination with a two-dimensional cross correlation of double-frame images. A weighing method has been applied for determination of the fuel-dependent exit velocity. A wide range of Reynolds numbers (1700-80,000) and gaseous Weber numbers (145-1121) has been covered by means of eleven different fuels and six different injection pressures. Different time regimes of the injection were defined and investigated separately: the opening, the acceleration regime, and the stationary regime. In the opening phase, an impact of bulk modulus of compressibility on injector opening delay has been identified. In the acceleration regime, it has been found that the beginning of breakup during spray emergence mainly depends on fluid viscosity. In the stationary regime of the injection, a correlation for the exit velocity has been developed using the Bernoulli velocity in combination with the Blasius approach for estimation of the nozzle hole friction factor. The dispersion of the jet has been found to be mainly a function of turbulence in the injected fluid. Based on this result, a new empiric correlation for the microscopic cone angle in the stationary regime of the injection has been developed.