A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item CHARACTERIZATION OF THE INITIAL SPRAY FROM A JET IN CROSSFLOW(2009) Zheng, Yinghui; Marshall, André; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An experimental study on the initial spray from a liquid jet in air crossflow was conducted using Shadowgraphy and Particle Image Velocimetry (PIV) techniques. Momentum ratio and gas Weber number were varied to study their effects on the column trajectory, spray trajectory, breakup locations and spray characteristics after column breakup. Correlations for column trajectory, spray trajectory, breakup locations in terms of momentum ratio and gas Weber number were obtained using linear regression of the experimental data. Two breakup modes were recognized in the test (Column breakup and Bag breakup), a breakup mode regime map was provided including effects of momentum ratio and gas Weber number. Drop characteristics in the spray were also investigated.Item FLOW AND ATOMIZATION CHARACTERISTICS OF CRYOGENIC FLUID FROM A COAXIAL ROCKET INJECTOR(2007-11-28) Gautam, Vivek; Gupta, Ashwani K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)High thrust-to-weight ratio and consistent performance over a range of operating conditions make cryogenic rocket engines one of the best options for space propulsion. However, future space explorations and missions to moon, mars and beyond require improvements in our present knowledge of the rocket engine combustion technology. In order to help improve the performance and reliability of current rocket engine combustors, several key issues need to be considered. Injector performance is one such issue related to the development of a new generation of rocket engine combustors. Previous research has suggested that coaxial injectors are most preferable for injection of cryogenic propellants inside the combustion chamber because of their simple design, low losses and high combustion stability. An experimental facility was designed and fabricated to simulate a single element shear coaxial injector. Gases of different densities were injected through the annulus between the two injector tubes over a large range of velocities, while liquid nitrogen flows through the inner tube. In this research, liquid nitrogen was used to simulate liquid oxygen because it is very similar to liquid oxygen, chemically inert, easy and safe to install in laboratory testing. High speed cinematography and Schlieren imaging have been used to examine the evolutionary flow behavior and global features of the liquid nitrogen jet, while PIV imaging was used to characterize the gaseous flow. This research has analyzed the transient behavior and unfolds the detailed evolutionary characteristics of both the cryogenic liquid and gaseous phase evolving from the shear coaxial injector for the first time. The effect of density ratio, velocity ratio and momentum ratio on the behavior of steady-state liquid nitrogen jet from a coaxial injector at atmospheric pressure has also been examined in detail. The impact of these parameters on primary instability of liquid core, the shear/spreading angle and its potential core length have been examined. Furthermore, the impact of some of the important non-dimensional numbers such as, Reynolds number, Weber number and Prandtl number, have been examined to develop scaling laws for the prediction of cryogenic potential core lengths. New correlations have been provided that describes the cryogenic jet behavior under simulated rocket injector operating conditions.Item Analysis of the initial spray from canonical fire suppression nozzles(2007-08-10) Ren, Ning; Marshall, André W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The performance of a fire suppression spray is governed by injector discharge characteristics. An atomization model based on the theoretical evolution of a radially expanding sheet generated by an impinging jet has been established in this study. The atomization model predicts characteristic initial drop location, size, and velocity based on injector operating conditions and geometry. These model predictions have been compared with measured discharge characteristics from three nozzle configurations of increasing geometrical complexity over a range of operating conditions. Differences between the predicted and measured initial spray are critically evaluated based on the experimentally observed atomization behavior.