A PLIF Observation of The Doublet Impingement of NTO/MMH Simulants for a 5-lbf Rocket
| Autor: | Berlin Huang, 黃柏霖 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Low-thrust bipropellant propulsion systems are mainly applied on the attitude and altitude controls of satellites. The hypergolic phenomenon of NTO/MMH impingement constructs the required combustion for thrust generation and the flame temperature distribution has significant effect on thruster’s performance. This research utilized simulants which matching the physical properties (density, surface tension and viscosity) of NTO/MMH to perform the cold-flow impinging experiments of a 5-lbf rocket. The O/F ratios of NTO and MMH were varied from 1.0 to 2.4 while the total mass flow rate (~8g/sec), impinging angle(60°) and injector orifice(0.3mm) were kept constants. PLIF technique was adopted to observe the 2-dimensional probability distributions of mass for either or both liquids. The distributions of local mixture ratios and adiabatic flame temperatures were deduced from mass distributions. The experimental results revealed that the ratio of momentum flux and differences of physical properties affected the mass and mixture ratio distributions. The liquid jet with a larger momentum flux was more concentrated. However, when the ratio of momentum flux reached 1.7(O/F=1.6), the break-up of MMH jet having a lower momentum flux was less dispersed for its lack of hydrodynamic instability at very low speed. Although the most uniform and symmetrical mass distribution of spray appeared at O/F=1.2 that corresponding to the ratio of momentum flux close to unity, the pseudo combustion efficiency estimated from the adiabatic flame temperature distribution was not the optimum. The optimum combustion efficiency occurred at O/F=1.8 (the ratio of momentum flux�l2.1), where the total and NTO mass distributions were not uniformly dispersed and shifted from the centerline. This thesis research also performed the study of the effect of viscosity on the breakup of impinging jets. Like- and unlike -doublet impingements of test solution B (��= 0.85�e10-3N�泅/m2) and solution C (��= 1.59�e10-3N�泅/m2) were performed with various total mass flow rates while keeping the ratio of momentum flux to unity. The observations of the like-doublet impingements showed that a higher jet velocity was required to reach the fully-developed spray pattern for the higher viscosity fluid. The results of the unlike-doublet impingements revealed that the mass distribution of spray C (higher viscosity fluid) was more concentrated (more difficult to be dispersed) than that of spray B at low total mass flow rates (��6.0g/sec) and both sprays were concaved to the side of the low viscosity jet. The difference of the uniformity of mass distributions due to their viscosity difference between two fluids became vague as the increase of the flow rates, however still distinguishable at the highest rate of 12.0g/sec. The analysis of the observations indicated that either viscosity or momentum flux affects the flow pattern inside the tube, that is, either laminar or turbulent flows. And, turbulent flow is easier to be atomized due to its higher hydrodynamic instability than laminar flow. As a result, viscosity and momentum flux, which are directly related to jet’s Reynolds number, have crucial effects on the spray pattern of impinging jets. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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