Minoru Fukuhara

Behavior of Tip Leakage Flow Behind an Axial Compressor Rotor

Performance testing and detailed flow measurements were made in an axial compressor rotor with various tip clearances. The experiments were conducted on the condition of the same incidence angle at midspan. Thus, the effect of tip clearance distinguished from that of incidence angle was investigated on the overall performance, work-done factor, blockage factor, and increases in displacement, momentum, and blade-force-deficit thicknesses of the casing wall boundary layer, The phase-locked flow patterns obtained by the multisampling technique show clear evidence of a leakage vortex core behind the rotor. Behavior of the leakage vortex was clarified for various tip clearances by examining loci of the vortex center, decay characteristics of the vorticity at the center, and the total amount of vorticity shed from the blade tip. These results were compared with the leakage vortex model presented by Lakshminarayana.

Studv on Flow Characteristics oi Compouna Swirl Jet (Effect of Nozzle Depth)

湯 之 谷 祥 平 ッ 鹿 児 島 大 院 ) , 福 原 稔 ( 鹿 児 島 大 ) 片 野 田 洋 ( 鹿 児 島 大 ) , 危 田 昭 雄 ( 鹿 児 島 大 ) Studv on Flow Characteristics oi Compouna Swirl Jet (Effect of Nozzle Depth) Syohei YUNOTANI, Minoru FUKUHARA Hiroshi KATANODA and Akio K A M E D A A B S T R A C T A c o m p o u n d s w i r l j e t w h i c h cons i s t s of a n a n n u l a r s w i r l i n g j e t a n d a c o a x i a l f r ee j e t i s e f f e c t i v e as a p u s h flow o f t h e p u s h p u l l v e n t i l a t o r . I n t h i s p a p e r , to e n h a n c e t h e c o l l e c t i n g c a p a b i l i t y o f t h e j e t f l o w , t h e e x p e r i m e n t w a s c a r r i e d o u t u n d e r t h e c o n d i t i o n o f l o c a t i n g t h e i n n e r t u b e o f f r ee j e t to t h e u p s t r e a m . T h e c o l l e c t e d flow r a t e o f t h e j e t flow w a s c a l c u l a t e d f o r v a r i o u s flow r a t e o f t h e s w i r l i n g j e t a n d nozz le d e p t h b y t h e m e a s u r e m e n t o f v e l o c i t y d i s t r i b u t i o n . A s a r e s u l t , i t w a s f o u n d t h a t t h e o p t i m u m c o l l e c t e d f l o w r a t e is o b t a i n e d w i t h o u t t h e s w i r l i n g f l o w , w h e n t h e nozz le d e p t h i n c r e a s e s . T h e g e n e r a t i o n m e c h a n i s m w a s c l a r i f i e d b y t h e flow v i s u a l i z a t i o n n e a r n o z z l e e x i t u s i n g P I V . T h e f l o w d e v e l o p i n g p r o c e s s o f t h e j e t f l o w w a s c o n f i r m e d b y s h o w i n g t h e c o l l e c t e d f l o w r a t e . K e y W o r d : F r e e j e t , S w i r l i n g f l o w , P u s h P u l l v e n t i l a t o r , P a r t i c l e i m a g e v e l o c i m e t r y

Effect of Depth of Discnarging Plates for Sediment Removal on Hydraulic Conveying Characteristics

A B S T R A C T I n t h e h y d r a u l i c c o n v e y i n g o f s o l i d l i q u i d f l o w i n t h e c o n d u i t , t h e d i s c h a r g i n g p l a t e s w e r e p r o p o s e d by t h e a u t h o r s to t r a n s p o r t t h e p a r t i c l e s t h a t h a d p i l e d u p . I n t h i s pape i ., t h e d e p t h o f t h e p l a t e s i n s t a l l e d f o r t h e p a r t i c l e beds w a s c h a n g e d a n d t h e f l o w o f t h e p a r t i c l e s w a s e x a m i n e d b y t h e f l o w v i s u a l i z a t i o n . A s a r e s u l t , i t w a s f o u n d t h e o p t i m u m d e p t h o f t h e p l a t e s f o r t h e p a r t i c l e beds ex i s t s . I t w a s c o n f i r m e d t h a t t h e e f fec ts o f i n t e r v a l a n d o v e r a l l l e n g t h o f t h e p l a t e s i n t h i s o p t i m u m c o n d i t i o n a re q u a l i t a t i v e l y s i m i l a r w i t h t h e case t h a t t h e d e p t h o f t h e p l a t e f o r t h e p a r t i c l e beds is s h a l l o w as t h e p r e v i o u s r e p o r t . K e y w o r d s : H y d r a u l i c c o n v e y i n g . S o l i d l i q u i d f l ow, Scour , S l u r r y

Effect of Pipe-Diameter Ratio on Heat Transfer and Flow Characteristics of Impinging Jet from Coaxial Circular Pipe

The impinging jet is widely used in the industrial field, as high heat transfer characteristics are obtained in the vicinity of a stagnation point on the object surface. In this paper, the heat transfer characteristics on the impinging wall after being blown off through a coaxial circular pipe were examined by changing the pipe-diameter ratio and the velocity ratio. As a result, the optimum values of the pipe-diameter ratio and the velocity ratio were found in the given conditions. The influence of the pipe-diameter ratio and the velocity ratio on the flow structure was clarified by the flow visualization.

Study on Particle Transport Characteristics of Doublet Type Suction Nozzle

In the pneumatic transportation, it was proposed by the authors that the effective and stable feeding of the particles can be attained by mounting the injection flow at the center of the suction nozzle. In this paper, we examined the influence of pipe diameter ratio on the nozzle performance. As a result, it was found that the optimum pipe diameter ratio exists. The various particles movement from different pipe diameter ratio was clarified by the flow visualization nearthe suction nozzle.

Study on Hydraulic Transport Characteristic by Discharging Plates

In the hydraulic transportation of lquid-solid flow in the conduit, to transport the particles that had piled up, the discharging plates were proposed by the author. In this paper, the installation interval of the plates was changed and the flow of the particles was examined by the flow visualization. As a result, it was found that the optimum installation interval of the plates exists, a downward jet flow influences the transportation of the particles when the interval of the plates is too wide and the jet flow in the direction of the flow influences when it is too narrow.

Visualization of Circular Impinging Jet Accompanying Annular Suction Flow

The effects of a length of suction pipe on the flow characteristics of a circular impinging jet accompanying an annular suction flow was examined experimentally at a fixed suction flow rate. The velocity field in the jet was visualized by using PIV(Particle Image Velocimetry). When the length of suction pipe increases, the flow field shows the phenomenon what the suction flow increases. And it is found that there exists the optimum size of the length of suction pipe.

Visualization of Particles Transport by Discharging Plates

A Rotating Drum Type Solid-Liquid Separator which operates in two different modes : one is a separating mode and another a discharging one is proposed by the authors. It is necessary to discharge solid particles out of the drum which pile up on the drum wall as soon as possible. In this paper, during the discharging mode, the flow visualized experiments were carried out using a two-dimensional model, in order to clarify the effects of the discharging plates. As a result, it was found that the aspect of particles transportation changes the distance of the discharging plates and a clearance between the plate edge and the surface of the particles bed and there exists the most probable distance of plates and clearance. In the case of large distance of the discharging plates, the transportation by the scour is predominant

Flow and Heat Transfer Characteristics of Circular Impinging Jet Accompanying Annular Suction Flow

Experiments were conducted on the effects of a wall distance and velocity ratio of suction flow to injection flow on the flow and heat transfer characteristics of a circular impinging jet accompanying an annular suction flow. As a result, it is found that in the case of accompanying suction flow, a higher Nusselt number can be obtained compared with in the case without suction flow, under a condition of the wall distance within eight times of injection pipe diameter from the near pipe exit edge. In addition, when the effect of velocity ratio is examined at a fixed arbitrary wall distance, it is found that there exists an optimum velocity ratio where the Nusselt number becomes the maximum. It is shown that these heat transfer characteristics are closely associated with the fluctuating velocity and the mean velocity in the two-dimensional velocity field observed by Particle Image Velocimetry (PIV).

Flow and Heat Characteristics on Circular Impinging Jet Added Annular Suction Flow

The existence of the improvement of cooling characteristics of the heating wall plane by circular impinging jet in adding the annular suction flow was examined. Following the previous report, the experiment was carried out on the case where the impinging wall was placed in transition and development region of circular free jet. As the result, in the transition region, there is the improvement of Nusselt number, when there is the suction flow in comparison with the case in which there is no suction flow. In the meantime, there is no improvement in the development region. It is proven that there is the close relation with fluctuating velocity and average flow rate using PIV on these heat transfer characteristics.