Behavior Of Tip Leakage Flow Research Articles

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Groove型ケーシングトリートメントが圧縮機直線翼列内の翼端漏れ流れの挙動に及ぼす影響 (ミッドコードに設けた単－Grooveの影響)

Groove型ケーシングトリートメントが圧縮機直線翼列内の翼端漏れ流れの挙動に及ぼす影響 (ミッドコードに設けた単－Grooveの影響)

Influence of Circumferential Groove Casing Treatment on Behavior of Tip Leakage Flow in Low Speed Axial Compressor

Influence of Circumferential Groove Casing Treatment on Behavior of Tip Leakage Flow in Low Speed Axial Compressor

Numerical Investigation of Circumferential Groove Casing Treatment in a Highly-Loaded Low-Reaction Transonic Compressor Rotor

In this paper, a computational investigation of circumferential groove casing treatment in a highly-loaded low-reaction transonic compressor rotor is conducted, in which the stage reaction is significantly reduced due to a larger meridional contraction with respect to conventional transonic compressors. Steady computation at near-stall point is performed first to capture the stall inception of the rotor with smooth casing. Detailed observations, which mainly focus on the tip leakage flow behavior, obstruction and vortical structures in the tip region, determine the reason for the compressor stall. There is tip leakage vortex breakdown in the tip region. Moreover, it yields passage obstruction, and finally leads to the compressor stall. Then, attempts are made to investigate how the circumferential grooves can be applied for the compressor’s stall margin enhancement without compromising efficiency. Three configurations are obtained and analyzed by changing axial position and the number of the circumferential grooves. The results of computational parametric study indicate the optimal location of the groove is near the leading edge and the downstream grooves combine their influence on the compressor’s stabilization and performance in a cumulative manner. The optimal circumferential groove configuration produces an increase of 1% in total pressure ratio at the near-stall point and a gain of 3.7% in stall margin, without any penalty in efficiency. Furthermore, the impact the grooves will exert on the flow mechanisms between the grooves and the main flow is also considered.

Influence of Incidence Angle on Behavior of Tip Leakage Flow in Linear Compressor Cascade

Influence of Incidence Angle on Behavior of Tip Leakage Flow in Linear Compressor Cascade

Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Influence of Groove Location and Depth on Flow Instability

The effect of circumferential single grooved casing treatment on the stability enhancement of NASA Rotor 37 has been examined with computational fluid dynamics analysis. Stall inception mechanism of Rotor 37 is presented first with principal focus on the tip leakage flow behavior, passage blockage, and the vortical flow structures. Detailed observation showed that the combined interaction of the stagnated flow of tip leakage vortex breakdown and the jetlike leakage flow from the midchord region leads to the blade tip-initiated stall inception. The result of numerical parametric study is then demonstrated to show the effect of varying the axial location and the depth of a circumferential single groove. The evaluation based on stall margin improvement showed a higher potential of deeper grooves in stability enhancement, and the optimal position for the groove to be located was indicated to exist near the leading edge of the blade.

Effects of casing treatment on behavior of tip leakage flow in an isolated axial compressor rotor blade row

This article deals with enhancement in aerodynamic performance of an isolated axial compressor rotor blade row while applying treated casing. Three dimensional unsteady flow is assumed and a flow solver, utilizing Large Eddy Simulation (LES), is undertaken for the numerical calculations. Unsteady tip leakage flow and its propagation trajectory are simulated in detail for both smooth and treated casings. Oscillatory nature of tip leakage flow is depicted and its frequency is calculated by the calculation of pressure distribution along the rotor blade tip, for smooth and treated casings. For the smooth casing and in comparison with experimental data, results showed that in contrast with the Reynolds Averaged Navier–Stokes method, the LES realizes dependency of frequency characteristics of the tip leakage flow on the blade tip clearance size, and also can recognize different frequency characteristics of the tip leakage flow along the blade chord. Results also demonstrated that performing casing treatment causes the amplitude of unsteadiness of tip leakage flow to reduce and its frequency to get closer to the blade passing frequency. This in turn, causes flow blockages and losses in total pressure to reduce.

Experimental and numerical investigation on compressor cascade flows with tip clearance at a low Reynolds number condition

High flow rate aeroengines typically employ axial flow compressors, where aerodynamic loss is predominantly due to secondary flow features such as tip leakage and corner vortices. In very high altitude missions, turbomachinery operates at low density ambient atmosphere, and the recent trend toward more compact engine core inevitably leads to the reduction of blade size, which in turn increases the relative height of the blade tip clearance. Low Reynolds number flowfield as a result of these two factors amplifies the relative importance of secondary flow effects. This paper focuses on the behavior of tip leakage flow, investigating by use of both experimental and numerical approaches. In order to understand the complex secondary flow behavior, cascade tests are usually conducted using intrusive probes to determine the loss. However relatively few experimental studies are published on tip leakage flows which take into account the interaction between a rotating blade row and its casing wall. Hence a new linear cascade facility has been designed with a moving belt casing in order to reproduce more realistic flowfield as encountered by a rotating compressor row. Numerical simulations were also performed to aid in the understanding of the complex flow features. The experimental results indicate a significant difference in the flowfield when the moving belt casing is present. The numerical simulations reveal that the leakage vortex is pulled by the shearing motion of the endwall toward the pressure side of the adjacent blade. The results highlight the importance of casing wall relative motion in analyzing leakage flow effects.

Experimental Aeroacoustic Studies on Improved Tip Configurations for Passive Control of Noise Signatures in Low-Speed Axial Fans

This paper presents the findings of an investigation on the use of several blade-tip configurations (modified by the addition of various end plates at the blade tip) for passive noise control in industrial fans. Utilizing an experimental technique developed to investigate noise sources along the radius of the blades, together with cross-correlation and coherence analyses of the near field and far field, the modified blade-tip configurations are shown to reduce the rotor-only aeroacoustic signature of the fan as a direct consequence of changes induced in tip-leakage flow behavior. These changes in the nature of flow mechanisms in the region of the blade tip are correlated with the spanwise noise sources, and their role in the creation of overall acoustic emissions is thus clarified. The tip-leakage flow structures are analyzed to identify their contribution to overall noise and interaction with other noise sources. Coherence spectra are also analyzed to investigate the relevance of the noise sources. The cross-correlations reveal distinctive acoustic signatures that are described in detail. The methodology has been demonstrated to be effective in identifying (i) the blade-tip configuration with the best acoustic performance, and (ii) other significant noise sources along the blade span. The modified tip configurations are shown to have a significant effect on the multiple vortex behavior of leakage flow, especially with respect to the near-wall fluid-flow paths on both blade surfaces. The reduction in fan acoustic emissions is assessed and correlated with the control of tip-leakage flows achieved by the modified blade tips.

입사각 변화에 따른 터빈 블레이드에서의 열전달 특성 변화 (I) - 블레이드 끝단면 -

The present study investigated local heat/mass transfer characteristics on the tip of the rotating turbine blade with various incoming flow incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with a mean tip clearance of 2.5% of the blade chord. The incoming flow Reynolds number is 1.5×10? at design condition. To examine the effect of off-design condition, the experiments with various incidence angles ranging between -15° and +7° were conducted. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. The results indicated that the incidence angle strongly affects the behavior of tip leakage flow around the blade tip and consequently plays an important role in determining heat transfer characteristics on the tip. For negative incidence angles, the heat/mass transfer in the upstream region on the tip decreases by up to 20%. On the contrary, for positive incidence angles, much higher heat transfer coefficients are observed even with small increase of incidence angle.

G601 動翼可変軸流ファンでのモーダル型旋回失速発生過程に及ぼす動翼先端流れの影響(2)(GS6 翼,渦,一般セッション)

Flow fields at the rotor tip region in a low-speed axial-flow fan were experimentally and computationally investigated to clarify the flow mechanism behind a modal stall inception pattern. The behavior of tip leakage flow at the modal stall inception was different from that at the spike stall inception. The interface between the incoming flow, tip leakage flow, and end-wall backflow did not parallel to the rotor leading edge plane. Leading edge separation occurred when the tip leakage vortex broke down. This separation grew and formed three-dimensional separation vortex, which stood on the suction side near the leading edge. We concluded from these results that this three-dimensional separation vortex influenced on the initiation of the modal disturbance.