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Present State of Self - Rectifying Air Turbines for Wave Energy Conversion
Toshiaki Setoguchi,Manabu Takao 한국유체기계학회 2003 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper reviews the present state of the art on the self-rectifying air turbines, which could be used for wave energy conversion. The overall performances of the turbines under irregular wave conditions, which typically occur in the sea, have been evaluated numerically and compared from the viewpoints of the starting and running characteristics. The types of turbine included in the paper are as follows: (a) Wells turbine with guide vanes (WTGV); (b) turbine with self-pitch-controlled blades (TSCB); (c) biplane Wells turbine with guide vanes (BWGV); (d) impulse turbine with self-pitch-controlled guide vanes (ISGV) and (e) impulse turbine with fixed guide vanes (IFGV). As a result, under irregular wave conditions it is found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine. Moreover, the authors have explained the mechanism of hysteretic behavior of the Wells turbine and the necessity of links for improvement of the performance of ISGV.
Large eddy simulation of shock vector control using bypass flow passage
Deng, Ruoyu,Setoguchi, Toshiaki,Kim, Heuy Dong Elsevier 2016 The International journal of heat and fluid flow Vol.62 No.2
<P><B>Abstract</B></P> <P>A detail description of the unsteady phenomena of three-dimensional shock vector control (SVC), including recirculation zones and shear layer regions, has been presented in this study. Shock vector control is a really efficient way to achieve flight direction control of high speed vehicle. Large eddy simulation (LES) has been applied to capture the unsteady characteristics of SVC method using bypass flow passage. Comparison of RANS and LES has been conducted in this study. LES model shows better results than others and it is able to capture the unsteady process very well. In this study, the separation bubble upstream of the injection port is the main source of flow unsteadiness. Large scale eddies in the whole flow field have been resolved by the LES model. Unsteady characteristics of SVC method at different nozzle pressure ratios (NPR) have been investigated. The time histories of thrust vector angle at different NPRs have been recorded by the LES model. The results indicate that it is possible to achieve SVC with the range of bypass mass flow ratio less than 7%. It is also revealed that nozzle pressure ratio has a strong effect on the unsteady phenomenon of SVC system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Unsteady phenomenon of shock vector control. </LI> <LI> Large eddy simulation. </LI> <LI> Vortexes in the separation bubble. </LI> </UL> </P>
A Study on the Flow Characteristics of the Spiral Flow Nozzle with the Width Change of Annular Slit
김태훈,이연원,Setoguchi,Toshiaki 한국가시화정보학회 2009 한국가시화정보학회지 Vol.7 No.1
In comparison with previous researches for swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.
Shigeru Matsuo,Toshiaki Setoguchi,Junji Nagao,Miah Md. Ashraful Alam,김희동 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.10
In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.
Prediction of Cascade Performance of Circular-Arc Blades with CFD
Suzuki, Masami,Setoguchi, Toshiaki,Kaneko, Kenji Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.4
Thin circular-arc blade is often used as a guide vane, a deflecting vane, or a rotating blade of low pressure axial-flow turbomachine because of its easy manufacture. Ordinary design of the blade elements of these machines is done by use of the carpet diagrams for a cascade of circular-arc blades. However, the application of the carpet diagrams is limited to relatively low cambered blade operating under optimum inlet flow conditions. In order to extend the applicable range, additional design data is necessary. Computational fluid dynamics (CFD) is a promising method to get these data. In this paper, two-dimensonal cascade performances of circular-arc blade are widely analyzed with CFD. The results have been compared with the results of experiment and potential theory, and useful information has been obtained. Turning angle and total pressure loss coefficients are satisfactorily predicted for lowly cambered blade. For high camber angle of $67^{\circ}$, the CFD results agree with experiment for the angle of attack less than that for shockless inlet condition.
Control of the Asymmetric Flow in a Supersonic Nozzle
Shigeru Matsuo,Toshiaki Setoguchi,Tokitada Hashimoto,Seiya Tokuda,Junji Nagao,Heuy-Dong Kim(김희동) 한국가시화정보학회 2011 한국가시화정보학회지 Vol.9 No.2
Several previous works on rocket nozzle flows have revealed thc existencc of the transition from FSS to RSS and the occurrence of asymmetric flow associated with the boundary layer separation, which can cause excessive side-loads of the propulsion system. Thus, it is of practical importance to investigate the asymmetric flow behaviors of the propulsion nozzlc and to develop its control method. In the present study, the asymmetric flow control method using a cavity system was applied to supersonic nozzle flow. Time-dependent asymmetric flow was experimcntally investigated with the rate of change of the nozzle pressure ratio. The results obtained showed that the cavity systcm installed on nozzle wall would be helpful in fixing the unsteady motions of the boundary layer separation, consequcntly reducing the possibility of the occurrence of the asymmetric flow.
李蓮源,瀨戶口 俊明 釜慶大學校 1998 釜慶大學校 論文集 Vol.3 No.2
A number of self-rectifying air turbines for wave power conversion have been proposed so far. This paper shows the comparison of the performances of all these turbines proposed for use in the near future. As a result, it was found that the impulse turbine with self-pitch-controlled guide vanes has the best performance.
Starting transient flows in a chevron ejector-diffuser system
Fanshi Kong,김희동,Toshiaki Setoguchi,김정수 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3
The vacuum ejector-diffuser system has been widely used in many applications such as refrigeration systems, high altitude test facilitiesand fluid transportation devices. We simulated the starting transient flows of a supersonic vacuum ejector-diffuser system and itsperformance characteristics and analyzed by the numerical methods. Newly designed chevron lobes were installed at the inlet of the primarystream of the vacuum ejector-diffuser system for the purpose of its performance improvement. A CFD method based on transientscheme was applied to simulate the equilibrium flow behavior inside the secondary chamber. Primary numerical analysis results showthat the performance of the vacuum ejector-diffuser system is considerably improved under chevron effects. Compared to the conventionalejector-diffuser system with a convergent nozzle, the updated system with a chevron nozzle leads to a lower equilibrium pressureinside the secondary chamber with less starting time. The flow characteristics obtained from the numerical results highlight the importanceof the vortex generation effects of the chevron nozzle. The generation process of the longitudinal vortexes and its effects on theejector-diffuser performance has been discussed in detail.