| Summary: | 碩士 === 國立中興大學 === 機械工程學系 === 89 === The air-pressurized waterjet rocket uses compressed air as the power source and water as the propellant; it often can achieve a better propulsion performance with less energy. Comparatively, it is characterized with simplicity, separated energy and mass, safety, environmentally friendliness, and minimal cost. Recently, news media show that there are various models of air-pressurized waterjet rockets, however, there still lacks the correct concept and total kinetic power equation for advanced analyses in associated basic theories. This problem remained unsolved until a revolutionary propulsion paper was presented by H. J. Lee of National Chung-Hsing University. Traditionally, pioneering countries always launch rockets with the concept of zero initial velocity, which is like shooting backward with fairly low energy efficiency for the rifle, and thus wasting extra cost. Generally, designers tend to increase propellant in order to improve the propulsion performance and attain higher altitude. Alternately, in this paper we use the novel concept of increasing the initial velocity of the rocket before igniting for improving efficiency. The basic theory is reducing the energy loss of the outgoing fluid. This article will synthesize the new concepts of Lagrangian Reynolds'' transport equation, momentum equation, total kinetic power, and thrust power to get a more complete, clear, natural, and systematic analyses of the flying state of air-pressurized waterjet Rocket. Further, we prove the propulsive efficiency enhancing effect of novel concept of increasing initial velocity with numerical simulation. In the solving process, we combine generalized momentum equation and generalized total kinetic power equation first, and then use the concepts of the numerical integration, convolution, and isentropic process to solve the complicated internal flow field completely. The results of numerical simulation clearly and definitely prove that the concept of increasing the initial velocity does have great effect on propulsion performance of air-pressurized waterjet rocket. The improvement may easily reach an amazing several hundred percents. This original study thus has laid a solid foundation for further promoting the original concept of increasing initial velocity to large satellite-launching rockets.
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