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The turbopump inducer cavitation is very important for the success of a liquid rocket engine. In this study the performance test and cavitation performance test were carried out at various rotational speed with two different diameter inducers. The rotational speed were varied 4000, 6000, 8000 rpm and the variation to the diameter of an inducer were taken as design size and 2 times enlarged size.<br/> The major results of the present study were as follows.<br/> 1. The hydraulic performance results showed that the similarity was met over the entire test range of the present study.<br/> 2. The blade thickness effect was examined and showed that the increased blade thickness resulted in decreased efficiency and worse cavitation performance for large tip clearance.<br/> 3. The cavitation performance test results showed that the breakdown NPSH increases as the flow coefficient and does not affected by the rotational speed.
Periodic pulsations in the static pressure near turbine surfaces as blade rows move relative to each other is one of the important sources of turbine unsteadiness. The present experiment aims to investigate the effect of the static pressure pulsations on the interaction of film coolant flows from two rows of staggered holes with mainstream and its effect on film cooling heat transfer. Potential flow pulsations are generated by the rotating shutter mechanism installed downstream of the test section, The free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033 - 0.33, and the amplitude of about 10-20%. Measured are time-averaged and phase-averaged velocity variations, pressure variations and temperature distributions of the flow field. Experimental conditions are identified by boundary layer measurements. Injectant behavior is characterized by the measurements of unsteady pressure in the plenum chamber and free-stream static pressure. The film cooling effectiveness is evaluated from the insulated wall temperature measurement. It has been found that bulk flow pulsation provides very large diffusion of the injectants and the effectiveness is significantly reduced by the flow pulsations.
Research on shock structures of supersonic jet through visualization experiments in low-pressure environment have not been actively conducted. Therefore, in this study, shock waves and supersonic jets were analyzed and compared by numerical analysis and Schlieren technique at low-pressure. Schlieren technique is commonly used to visualize the shock waves generated by density gradient as interferometric methods. Pressure ratio of entrance and ambient was set around 4 to observe moderate under-expanded jet. For validation of experimental and numerical results, the shock structure and frequency were compared. In the case of ST and C nozzle, the results were shown that the difference of shock cell distance was within 10%. The Mach number gradually decreased due to energy reduction, and the error rate was within 7%. D nozzle was not fitted to be observing the shock structure. Because the interface between rarefaction fan and supersonic jet was ambiguous and oscillating phemenoma occurred at end of jet, the supersonic jet in low ambient pressure was observed and analyzed.
An experimental study on heat transfer and flow characteristics of a circular impinging jet on a flat plate has been carried out. Of particular interests are the effects of nozzle wall thickness and nozzle exit pressure. Experimental apparatus has been designed to view heating plate coated by TLC from the opposite side of the nozzle in order to measure heat transfer rates for cases of very small nozzle to plate spacings. A visualization study of jet flows has also been performed. As the nozzle wall thickness increases at small nozzle to plate spacings, the effect of mixing is inhibited due to the confinement caused by the finite nozzle wall, consequently, heat transfer rates have been decreased. At small nozzle to plate spacings, heat transfer rates and nozzle exit pressures are increased together, therefore, enhancement of heat transfer at small nozzle to plate spacings should be considered in conjunction with the need of more fan power to generate the same Reynolds numbers.
‘Ionic wind' is phenomenon induced by corona discharge which occurs when large electric potential is applied to electrodes with high curvature. The ionic wind has advantage that it could generate forced convective flow without any external energy like separate pump. In this study, ‘pin-mesh' arrangement is utilized for experiments. First, optimization of configuration is conducted with local momentum of ionic wind behind the mesh. Empirical equation for prediction about velocity profile was derived using the measured results. Secondly, the enhancement of mass transfer rate of acetone with ionic wind was analyzed. Also, the drying efficiency using a fan which has same flow rate was compared with ionic wind for identification of additional chemical reaction. At last, the drying process of organic solvent was visualized with image processing. As a result, it was shown that the use of ionic wind could dry organic matter four times faster than the natural condition.
As a demand for highly integrated mechanical systems such as precision robots increases, research on miniaturization as well as performance improvement of devices is getting more attention. Recently, development of smart materials such as a piezo has been accelerated for the miniaturization of the power source, and researches on the development and miniaturization of the driving device have been increased. In this study, the membrane pump using the piezoelectric actuator was analyzed. First, the pump was designed and fabricated to verify the performance, and the basic flow rate experiment was conducted. The body of the pump is made of a transparent material to measure the internal flow for precise analysis of the flow field. Numerical analysis for the performance was also performed using the FSI-2way method, which is suitable for simulating the movement of the membrane valves. Both the experimental and CFD results showed that the maximum flow rate was obtained at 30 Hz and the maximum flow velocity was 5.88 mm/s for the experiment and 5.33 mm/s for the numerical analysis, and the error was 9.35 %. The reliability of the numerical analysis could be obtained by the comparison with the experiment, and it is expected that the FSI-2way technique can be reliably used for the research on performance improvement of the pump.