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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>
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.
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.
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.
The Effect of the Secondary Annular Stream on Supersonic Jet
Kwon Hee Lee,Toshiaki Setoguchi,Shigeru Matsuo,Hyeu Dong Kim 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.11
The present study addresses an experimental investigation of the near field flow structures of supersonic, dual, coaxial, free, jet, which is discharged from the coaxial annular nozzle. The secondary stream is made from the annular nozzle of a design Mach number of 1.0 and the primary inner stream from a convergent-divergent nozzle. The objective of the present study is to investigate the interactions between the secondary stream and inner supersonic jets. The resulting flow fields are quantified by pitot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the primary jet are varied to obtain over-expanded flows and moderately under-expanded flows at the exit of the coaxial nozzle. The pressure ratio of the secondary annular stream is varied between 1.0 and 4.0. The results show that the secondary annular stream significantly changes the Mach disc diameter and location, and the impact pressure distributions. The effects of the secondary annular stream on the primary supersonic jet flow are strongly dependent on whether the primary jet is underexpanded or over-expanded at the exit of the coaxial nozzle.