Stephen D. Heister

Droplet size control in liquid jet breakup

A Boundary Element Method (BEM) has been developed to investigate the nonlinear evolution of the surface of liquid jets injected from circular orifices under unsteady inflow conditions. For fixed wavelength perturbations, the model predicts the formation of main and satellite droplets. The size of the droplets is affected by changes in the perturbation wavelength, perturbation magnitude and Weber number. Satellite droplet velocities are less than main droplet velocities due to the sequential shedding of droplets from the orifice. Using this information, one can determine the likelihood of droplet recombinations downstream of the initial pinching event.

Characterization of pintle engine performance for nontoxic hypergolic bipropellants

Using rocket-grade hydrogen peroxide and a nontoxic, hypergolic miscible fuel, a 150-lbf thrust class pintle injector engine has been developed and tested with the aim of characterizing injector performance under a variety of design and operating conditions. Rapid, reproducible ignition was sustained under a wide range of operating conditions using the new hypergolic propellant combination. Parametric studies were undertaken to assess the influence of characteristic chamber length L*, chamber diameter-to-pintle diameter ratio, total momentum ratio, secondary-to-primary hole diameter ratio, and the pintle length-to-pintle diameter ratio. High performance has been achieved in both steady-state and pulse mode operation.

NONLINEAR MODELING OF JET ATOMIZATION IN THE WIND-INDUCED REGIME

A boundary element method (BEM) has been developed to solve for the nonlinear evolution of a liquid jet acting under the influence of both surface tension and the aerodynamic interactions with the surrounding atmosphere. For longer waves, aerodynamic effects are shown to cause a ‘‘swelling’’ of the liquid surface in the trough region. The model predicts the presence of satellite drops in the first wind‐induced regime, and predicts the evolution of a ‘‘spiked’’ surface at the periphery of the jet for conditions consistent with the second wind‐induced regime. The effects of the disturbance wave number, the liquid Weber number, and the density ratio between the liquid jet and the surrounding gas on the breakup of the jet have been examined. Transition points between various flow regimes have also been identified.

Nonlinear modeling of an infinite electrified jet

Abstract A nonlinear model has been developed to assess the time-dependent evolution of an infinite electrified jet. The model assumes inviscid, axisymmetric flow in the jet and utilizes boundary element methods to describe unsteady jet evolution. Droplet sizes are predicted for various charging conditions and disturbance wave-lengths. Results indicate that nonlinear contributions from the electrostatic force are very important and can differ substantially from those predicted by linear theory.

Modeling the Effect of Unsteady Chamber Conditions on Atomization Process

AP e The response of fluid flow through an orifice to chamK ber pressure oscillations and the evolution of the corp responding liquid jet has been investigated through & the use of a two-dimensional model based on the <£ Boundary Element Method. A series of parametric

Characterization of Pintle Engine Performance for Nontoxic Hypergolic Bipropellants

simulations have been performed using this tool to Subscripts evaluate the effect of orifice length, injection condi£ tions, and the amplitude and frequency of chamber g pressure oscillations on the dynamic orifice massflow, j phase lag, and jet surface shape. Results indicate osc substantial differences between the 2-D simulations ss and 1-D theory, particularly in the case where the oo orifice passage is short. Simulations have also been rnin performed to address the velocity profile at the exit max plane under these unsteady injection conditions. pressure drop across the orifice ratio of gas to liquid density surface curvature density surface tension velocity potential phase lag liquid phase properties gas phase properties nodal location oscillation amplitude steady state value far field condition minimum value maximum value

A BOUNDARY-ELEMENT METHOD FOR ATOMIZATION OF A FINITE LIQUID JET

Using rocket grade hydrogen peroxide (RGHP) and a nontoxic, hypergolic miscible fuel (NHMF), a 150-lbf thrust class pintle injector engine has been developed at Purdue University for the purposes of determining parameters leading to high combustion efficiency. The parameters investigated include characteristic length, chamber diameter-to-pintle diameter ratio, total momentum ratio (TMR), secondary-to-primary hole diameter ratio, and the pintle length-to-pintle diameter ratio. High performance has been achieved in both steady-state and pulse mode operation. Nomenclature RGHP Rocket grade hydrogen peroxide NHMF Nontoxic, Hypergolic, Miscible Fuel TMR Total Momentum Ratio NTO Nitrogen tetroxide MMH Monomethyl hydrazine TMR Total Momentum Ratio ISP Specific impulse ISPv Vacuum Specific Impulse ρISPv Vacuum density specific impulse PC Chamber pressure ∈ Nozzle area ratio DSEC Secondary hole diameter DPRI Primary hole diameter L* Characteristic length c* Characteristic velocity sps Samples per second fps Frames per second