Document Type

Thesis

Date of Degree

Fall 2014

Degree Name

MS (Master of Science)

Degree In

Mechanical Engineering

First Advisor

Albert Ratner

Abstract

This paper investigated the effects of swirl number and momentum ratio on the atomization and mixing performance of Swirl-Venturi Lean Direct Injection technology. Mie scattering of liquid water, was used to identify the location of water droplets in a cross section of the injector spray. Experiments were performed with three air swirlers with vane angles of 45, 52 and 60 degrees. The swirl number varied from 0.58 to 1.0 and air-to-liquid ratios from 15.8 to 35.6. A transition was observed in the liquid spray distribution for the 52 degree case, which unexpectedly produced twice as much signal than the 45 and 60 degree cases. The main cause of this increased signal may be due to instabilities in the flow when transitioning from low to high swirl states. The results from investigation of swirl number it was found that the spray pattern for is sensitive to swirl intensity. Two flow states were observed for a lower and higher swirl flow as well as a transition state that occurred with the lower swirl state. This work may aid in the specific inquiry of physical mechanisms relating to the effect of flow states on spray distribution. It is found that improved atomization and mixing performance are a result of increase in swirl number.

Public Abstract

The rising cost of fuels and greater concern for the environment drive efforts in the laboratory to investigate the physics and chemistry of cleaner, more fuel efficient sources of power. Lean combustion has proven to decrease emissions and improve fuel efficiency. In order to achieve the benefits of lean combustion, the method in which fuel and air is mixed becomes critical to the overall performance of the engine. This paper is focused on fuel injection technology for aircraft engines. The objective of this work is to provide qualitative insight into the atomization and mixing process of the Lean Direct Injection. Mie scattering of liquid water was used to identify the location of water droplets in a cross section of the injector spray. High speed photography was used to capture the spray pattern. Experiments were performed with varied the swirl number from 0.58 to 1.0 and air-to-liquid ratios from 15.8 to 35.6 to investigate the effects these have on spray performance. It was found that the spray pattern is sensitive to swirl intensity, that as swirl number increases the spray penetration length decreases and spray pattern moves upstream toward the injector. Both improved atomization and mixing performance are a result of increasing the swirl number. The results of varied air-to-liquid ratio show the mixedness and dispersion of droplets increase with increasing momentum ratio. The results also show decreasing spray penetration length with increasing momentum ratio.

Keywords

publicabstract, Atomization, Fuel injection, Lean Direct Injection, Mie scattering, Mixing, Sprays

Pages

x, 62 pages

Bibliography

Includes bibliographical references (pages 58-62).

Copyright

Copyright 2014 Matthew W Burkhalter

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