Thrust and Specific Impulse Optimization of Eight-Centimeter Valveless Pulsejets at Low Subsonic Flight Speeds
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Date
2008-12-02
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Abstract
The purpose of this research was to develop a method of accurately measuring the thrust
and specific impulse of valveless pulsejets that are approximately eight centimeters in
length. Previous methods of doing such were largely unsuccessful. A vertically arranged
thrust stand and electronic balance were ultimately able to produce reliable results.
Seven inlets were then tested on a forward facing arrangement. The maximum thrust
achieved was 24.4 mN and specific impulse peaked at 295 seconds. Comparison
revealed that increasing inlet length has a positive effect on pulsejet performance. Each
inlet was tested at simulated forward flight speeds as well, showing that shorter inlets
perform optimally at lower speeds than longer inlets. Additionally, a relationship
between pulsejet performance, frequency and exhaust temperature was identified.
Similar tests were performed on hybrid configurations as well, which combine forwardfacing
and rearward-facing inlets. Of the five hybrid configurations tested, maximum
thrust was 31.2 mN and maximum specific impulse was 232 seconds. This series of tests
revealed that these configurations also showed improvement in performance at higher
forward flight speeds and at smaller inlet areas. In all cases, hydrogen was used as the
fuel, due to its very short chemical time. Pulsejets at this scale are also shown to be
capable of operating on acetylene, although with reduced performance.
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Keywords
subsonic, pulsejet, thrust, miniature, specific impulse
Citation
Degree
MS
Discipline
Aerospace Engineering
