Pressure Loss Due to the Tip Clearance of Impeller Blades in Centrifugal and Axial Blowers

1986 ◽  
Vol 108 (1) ◽  
pp. 32-37 ◽  
Author(s):  
Y. Senoo ◽  
M. Ishida
Keyword(s):  
Experimental Data ◽  
Pressure Gradient ◽  
Pressure Loss ◽  
Present Model ◽  
Tip Clearance ◽  
Fair Agreement ◽  
Leakage Flow ◽  
Flow Through ◽  
Annular Clearance ◽  
Special Case

The pressure loss based on the tip clearance of impeller blades consists of the pressure loss induced by the leakage flow through the clearance and the pressure loss for supporting fluid against the pressure gradient in the channels and in the thin annular clearance space between the shroud and the impeller. Equations to evaluate these losses are derived and the predicted efficiency drop is compared with experimental data for two types of centrifugal impellers. Furthermore, the equations are simplified for axial impellers as a special case, and the predicted efficiency drop is compared with the experimental data for seven cases in the literature. Fair agreement demonstrates plausibility of the present model.

Effect of Blade Tip Configuration on Tip Clearance Loss of a Centrifugal Impeller

1990 ◽  
Vol 112 (1) ◽  
pp. 14-18 ◽  
Author(s):  
M. Ishida ◽  
H. Ueki ◽  
Y. Senoo
Keyword(s):  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Meridional Plane ◽  
Leakage Flow ◽  
Clearance Ratio ◽  
Contraction Coefficient ◽  
Blade Tip ◽  
Flow Through ◽  
Annular Clearance ◽  
Blade Tip Clearance

According to the theory presented by the authors, the tip clearance loss of an un-shrouded centrifugal impeller mainly consists of two kinds of loss; one is the drag due to the leakage flow through the blade tip clearance and the other is the pressure loss to support the fluid in the thin annular clearance space between the shroud and the blade tip against the pressure gradient in the meridional plane without blades. The former is proportional to the leakage flow or the contraction coefficient of leakage flow. The authors have conducted performance tests using an impeller with 16 backward-leaning blades in three configurations of the blade tip: round edge, sharp square edge, and edge with an end-plate. The experimental tip clearance effects can be predicted by the theory assuming reasonable contraction coefficients. They are 0.91, 0.73, and 0.53 for the respective tip configurations. The impeller efficiency is improved by about 1.5 point by reducing the contraction coefficient from 0.91 to 0.53, providing that the tip clearance ratio at the exit of impeller is 0.1. More improvement is expected for an impeller with highly loaded blades where the leakage loss shares the major part of the tip clearance loss.

Effect of Blade Tip Configuration on Tip Clearance Loss of a Centrifugal Impeller

1989 ◽  
Author(s):  
Masahiro Ishida ◽  
Hironobu Ueki ◽  
Yasutoshi Senoo
Keyword(s):  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Meridional Plane ◽  
Leakage Flow ◽  
Clearance Ratio ◽  
Contraction Coefficient ◽  
Blade Tip ◽  
Flow Through ◽  
Annular Clearance ◽  
Blade Tip Clearance

According to the theory presented by the authors, the tip clearance loss of an unshrouded centrifugal impeller mainly consists of two kinds of loss; one is the drag due to the leakage flow through the blade tip clearance and the other is the pressure loss to support the fluid in the thin annular clearance space between the shroud and the blade tip against the pressure gradient in the meridional plane without blades. The former is proportional to the leakage flow or the contraction coefficient of leakage flow. The authors have conducted performance tests using an impeller with sixteen backward-leaning blades in three configurations of the blade tip: round edge, sharp square edge and edge with an end-plate. The experimental tip clearance effects can be predicted by the theory assuming reasonable contraction coefficients. They are 0.91, 0.73 and 0.53 for the respective tip configurations. The impeller efficiency is improved by about 1.5 point by reducing the contraction coefficient from 0.91 to 0.53 providing that the tip clearance ratio at the exit of impeller is 0.1. More improvement is expected for an impeller with highly loaded blades where the leakage loss shares the major part of the tip clearance loss.

Theoretical Modelling of Relative Wall Motion Effects in Tip Leakage Flow

1995 ◽  
Author(s):  
I. K. Nikolos ◽  
D. I. Douvikas ◽  
K. D. Papailiou
Keyword(s):  
Wall Motion ◽  
Tip Clearance ◽  
Calculation Procedure ◽  
Theoretical Modelling ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Complete Calculation ◽  
Flow Through ◽  
Good Agreement

The influence of relative wall motion in modifying the leakage flow through the tip clearance is investigated. A theoretical model is developed, in order to calculate the mass flow rate through the gap. The physical mechanism by which relative wall motion affects the leakage flow is analyzed and the differences between the turbine and compressor case are identified. This model, being an extension of an already existing one, not taking into account relative wall motion, is incorporated into the tip clearance calculation procedure, already developed by the authors. Theoretical results of the complete calculation procedure (secondary flow plus tip clearance model) are compared with experimental data, for the case of compressor and turbine cascades, as well as for the case of a single rotor. Good agreement between theory and experiment is obtained.

On the Pressure Losses Due to the Tip Clearance of Centrifugal Blowers

1981 ◽  
Vol 103 (2) ◽  
pp. 271-278 ◽  
Author(s):  
M. Ishida ◽  
Y. Senoo
Keyword(s):  
Pressure Gradient ◽  
Pressure Loss ◽  
Relative Velocity ◽  
Pressure Rise ◽  
Input Power ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Clearance Ratio ◽  
Local Pressure ◽  
Pressure Losses

The pressure distribution along the shroud is measured for three types of centrifugal impeller at seven different values of tip clearance each. The change of input power due to a change of tip clearance is related to the effective blockage at the impeller tip. Since the change of input power is little for the test cases, the variation of local pressure gradient along the shroud is mostly attributed to the change of local pressure loss. The local pressure loss is related to the local tip clearance ratio and to the local pressure gradient based on the deceleration of relative velocity in the impeller. Since the local pressure gradient is largest near the throat of the impeller, for many impellers the clearance ratio at the throat is used as the representative value. The tip clearance loss is related to the clearance ratio and the pressure rise based on the deceleration of relative velocity in the impeller. A good correlation is observed in all cases at various flow rate.

Effects of inducer tip clearance on the performance and flow characteristics of a pump in a turbopump

2017 ◽  
Vol 231 (5) ◽  
pp. 398-414 ◽  
Author(s):  
Changhyun Kim ◽  
Semi Kim ◽  
Chang-Ho Choi ◽  
Jehyun Baek
Keyword(s):  
Flow Characteristics ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Cfd Analysis ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Ansys Cfx ◽  
Performance Deterioration ◽  
Flow Through ◽  
High Thrust

A turbopump is used to pressurize propellants to gain high thrust in a projectile and consists of two pumps and a turbine. The pumps usually employ an inducer upstream to prevent performance deterioration by lowering net positive suction head required of the main impeller. However, several types of cavitation and instabilities take place in the flow field. Therefore, numerous experiments and CFD analysis for turbopumps have been conducted. Especially, there were some previous studies on inducer tip clearance, but they were limited to inducer regions due to the complexity of simulating the entire pump. In this study, the flow through an oxidizer pump in a turbopump was numerically investigated with four different sizes of inducer tip clearances. ANSYS CFX 13.0 with Rayleigh–Plesset equation was used to test flows in both non-cavitating and cavitating conditions. In the non-cavitating condition, the pump with the largest inducer tip clearance showed the worst head rise, efficiency and huge size of backflow arose near inducer casing. Also, the vortex was generated between the inducer blades in the case of large inducer tip clearance due to weak tip leakage flow. In the cavitating condition, the inducer with large tip clearance was found to be vulnerable to low suction pressure and floating cavity was observed between the inducer blades. However, the heads of the pumps with different inducer tip clearances were broken down at similar cavitation numbers due to the blade cavitation near the impeller throat. In addition, the transferred cavity from the inducer region also induced head breakdown of the pump.

Investigation Into Core Compressor Tip Leakage Modelling Techniques Using a 3D Viscous Solver

2001 ◽  
Author(s):  
Jonathan P. Glanville
Keyword(s):  
Transport Model ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Modelling Techniques ◽  
Flow Through ◽  
Tip Leakage Flows

The leakage flow through the tip clearance gap of an axial compressor has a significant effect on loss production and stall behaviour. Accurate modelling is essential if improved designs are to be developed which control such flows. Studies have been carried out using the DERA TRANSCode 3D Reynolds-Averaged Navier-Stokes code to predict the tip leakage flows in a low speed research compressor. Calculations were carried out using both a simple pinched-tip model and an improved mesh which allowed the true square-tip geometry to be represented. Comparisons between the Baldwin-Lomax algebraic turbulence model and the Spalart-Allmaras one-equation transport model were also made. The results showed that the predictions of both the detailed flows and the loss levels were sensitive to the modelling and that substantial improvements in accuracy were possible.

Numerical Study on the Effects of Casing Treatment on Unsteadiness of Tip Leakage Flow in an Axial Compressor

2012 ◽  
Author(s):  
Yoojun Hwang ◽  
Shin-Hyoung Kang
Keyword(s):  
Numerical Study ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Operating Range ◽  
Compressor Rotor ◽  
Flow Through

A low speed axial compressor with casing treatment of axial slots was numerically investigated. Time-accurate numerical calculations were performed to simulate unsteady flow in the rotor tip region and the effects of casing treatment on the flow. Since the compressor rotor had a large tip clearance, it was found that the tip leakage flow had an inherent unsteady feature that was not associated with rotor rotation. The unsteadiness of the tip leakage flow was induced by changes in the blade loading due to the pressure distribution formed by the tip leakage flow. This characteristic is called rotating instability or self-induced unsteadiness. The frequency of the flow oscillation was found to decrease as the flow rate was reduced. On the other hand, as expected, the operating range was improved by casing treatment, as shown by calculations in good agreement with the experimentally measured data. The unsteadiness of the tip leakage flow was alleviated by the casing treatment. The interaction between the flow in the tip region and the re-circulated flow through the axial slots was observed in detail. The removal and injection of flow through the axial slots were responsible not only for the extension of the operating range but also for the alleviation of the unsteadiness. Analyses of instantaneous flow fields explained the mechanism of the interaction between the casing treatment and the unsteady oscillation of the tip leakage flow. Furthermore, the effects of changes in the amount of re-circulation and the location of the removal and injection flow on the unsteadiness of the tip leakage flow were examined.

scholarly journals On the Pressure Losses due to the Tip Clearance of Centrifugal Blowers

1980 ◽  
Author(s):  
M. Ishida ◽  
Y. Senoo
Keyword(s):  
Pressure Gradient ◽  
Pressure Loss ◽  
Relative Velocity ◽  
Pressure Rise ◽  
Input Power ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Clearance Ratio ◽  
Local Pressure ◽  
Pressure Losses

The pressure distribution along the shroud is measured for three types of centrifugal impeller at seven different values of tip clearance each. The change of input power due to a change of tip clearance is related to the effective blockage at the impeller tip. Since the change of input power is little for the test cases, the variation of local pressure gradient along the shroud is mostly attributed to the change of local pressure loss. The local pressure loss is related to the local tip clearance ratio and to the local pressure gradient based on the decleration of relative velocity in the impeller. Since the local pressure gradient is largest near the throat of impeller is used as the representative value. The tip clearance loss is related to the clearance ratio and the pressure rise based on the deceleration of relative velocity in the impeller. A good correlation is observed in all cases at various flow rate.

Numerical simulation of unsteady tip clearance flow in an isolated axial compressor rotor blades row

2011 ◽  
Vol 226 (1) ◽  
pp. 82-93 ◽  
Author(s):  
R Taghavi-Zenouz ◽  
S Eslami
Keyword(s):  
Experimental Data ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Clearance Flow

Three-dimensional unsteady numerical simulations were carried out to analyse tip clearance flow in a low-speed isolated axial compressor rotor blades row. A flow solver has been used for the current study utilizing the large eddy simulation (LES) technique. Periodic tip leakage flow and its propagation trajectories were simulated in detail. A number of pseudo pressure transducers were imposed on the pressure side of the blade for detection of unsteady surface pressures to provide a calculation of tip leakage flow frequencies. Two different sizes of tip clearance were considered for simulations and analyses. Non-dimensional frequencies of the tip leakage flow were calculated and final results were compared to those of existing numerical and experimental data. Final results demonstrated that in contrast to the Reynolds averaged Navier–Stokes (RANS) model, the LES method shows considerable dependency of frequency characteristics of the tip leakage flow to the gap size and can detect different frequency spectrums along the blade surface. All the results obtained through the current numerical approach were in close agreement with those of existing experimental data.

Characteristics of Tip-Leakage Flow at High Stagger-Angle Setting for Rotor Blade in an Axial Flow Fan

2012 ◽  
Author(s):  
Takahiro Nishioka ◽  
Masayoshi Joko
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Maximum Efficiency ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Stagger Angle

Rotor-tip flow fields at high stagger-angle setting were investigated to clarify the loss generation mechanism in a high specific-speed axial-flow fan. The tip clearance flow in the cases of large and small clearances, which are 2.0% and 1.0% of the rotor tip chord length respectively, are experimentally and numerically evaluated at the maximum efficiency point and the operating limit. At the maximum efficiency point, the tip leakage vortex reached to the rotor exit in both cases of large and small tip clearances. However, the leakage vortex in the case of large tip-clearance passed closer to the pressure side of the adjacent blade than that in the case of small one. Moreover, in the case of large tip clearance, the tip leakage vortex generated the large total pressure loss in the blade passage, and the interaction between the tip leakage vortex and the wake also generated the large total pressure loss at the rotor exit. Therefore, the maximum efficiency of the rotor and the fan was lower than that in the case of small tip clearance. At the operating limit, the tip-leakage vortex extended inside the blade passage and reached to the front part of the pressure side of the next blade in the case of small tip-clearance. Moreover, the double leakage flow occurred in the case of small tip clearance. In contrast, the leakage vortex reached to the leading edge of the next blade, and the spillage of the tip leakage flow from the leading edge occurred in the case of large tip clearance. The spillage of the tip leakage flow induced the larger total pressure loss than that induced by the double leakage flow. Therefore, the pressure rise in the case of large tip clearance is lower than that in the case of small tip clearance at the operating limit. It was concluded from the experimental and numerical results at the high stagger-angle setting for rotor blade that the loss generation mechanism depended on the behavior of tip-leakage vortex and that this behavior also depended on the tip-clearance.

Sign in / Sign up

Export Citation Format

Share Document