Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions

2010 ◽  
Author(s):  
Xuwen Qiu ◽  
David Japikse ◽  
Jinhui Zhao ◽  
Mark R. Anderson
Keyword(s):  
Test Data ◽  
Slip Velocity ◽  
Factor Model ◽  
Flow Coefficient ◽  
Slip Model ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
New Model ◽  
Slip Factor

This paper presents a unified slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or slip velocity at impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the slip velocity using Stodola’s assumption. The final form of the slip factor model can be successfully related to Carter’s rule [1] for axial impellers and Stodola’s [2] slip model for radial impellers, making the case for this model to be applicable to axial, radial, and mixed-flow impellers. Unlike conventional slip factor models for radial impellers, the new slip model suggests that the flow coefficient at the impeller exit is an important variable for the slip factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for slip factor observed from experiments, such as the rise of the slip factor with flow coefficient in the Eckardt A impeller [3]. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the slip factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the slip factor are compared at both design and off-design flow conditions. In total, over 1,650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional slip factor correlations, such as the Busemann-Wiesner model [4], when off-design conditions are considered.

Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Xuwen Qiu ◽  
David Japikse ◽  
Jinhui Zhao ◽  
Mark R. Anderson
Keyword(s):  
Test Data ◽  
Slip Velocity ◽  
Factor Model ◽  
Flow Coefficient ◽  
Slip Model ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
New Model ◽  
Slip Factor

This paper presents a unified slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or the slip velocity at the impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the slip velocity using Stodola’s assumption. The final form of the slip factor model can be successfully related to Carter’s rule for axial impellers and Stodola’s slip model for radial impellers, making the case for this model applicable to axial, radial, and mixed-flow impellers. Unlike conventional slip factor models for radial impellers, the new slip model suggests that the flow coefficient at the impeller exit is an important variable for the slip factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for slip factor observed from experiments, such as the rise of the slip factor with flow coefficient in the Eckardt A impeller. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the slip factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the slip factor are compared at both design and off-design flow conditions. In total, over 1650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional slip factor correlations, such as the Busemann–Wiesner model, when off-design conditions are considered.

A New Slip Factor Model for Axial and Radial Impellers

2007 ◽  
Author(s):  
Xuwen Qiu ◽  
Chanaka Mallikarachchi ◽  
Mark Anderson
Keyword(s):  
Factor Model ◽  
Important Variable ◽  
Flow Coefficient ◽  
Slip Model ◽  
Mixed Flow ◽  
Velocity Difference ◽  
Blade Loading ◽  
Axial Compressors ◽  
Slip Factor ◽  
Proposed Model

This paper proposes a unified slip model for axial, radial, and mixed flow impellers. For many years, engineers designing axial and radial turbomachines have applied completely different deviation or slip factor models. For axial applications, the most commonly used deviation model has been Carter’s rule or its derivatives. For centrifugal impellers, Wiesner’s correlation has been the most popular choice. Is there a common thread linking these seemingly unrelated models? This question becomes particularly important when designing a mixed flow impeller where one has to choose between axial or radial slip models. The proposed model in this paper is based on blade loading, i.e., the velocity difference between the pressure and suction surfaces, near the discharge of the impeller. The loading function includes the effect of blade rotation, blade turning, and the passage area variation. This velocity difference is then used to calculate the slip velocity using Stodola’s assumption. The final slip model can then be related to Carter’s rule for axial impellers and Stodola’s slip model for radial impellers. This new slip model suggests that the flow coefficient at the impeller exit is an important variable for the slip factor when there is blade turning at the impeller discharge. This may explain the interesting slip factor trend observed from experiments, such as the rise of the slip factor with flow coefficient in Eckardt A impeller. Some validation results of this new model are presented for a variety of applications, such as radial compressors, axial compressors, pumps, and blowers.

Validations of Some Slip Factor Models for Mixed-Flow Impellers

2008 ◽  
Author(s):  
Shengqin Huang ◽  
Zhenxia Liu ◽  
Yaguo Lu ◽  
Yan Yan ◽  
Xiaochun Lian
Keyword(s):  
Inclination Angle ◽  
Factor Model ◽  
Critical Value ◽  
Factor Models ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Correct Prediction ◽  
Mixed Flow ◽  
Blade Number ◽  
Slip Factor

Accurate modeling of the slip factor is essential for correct prediction of the mixed-flow impeller performance, but the slip factor model well-known for mixed-flow impeller is relatively rare. Two ways for calculating mixed-flow impeller slip factor are present in this paper: (1) Using impeller exit inclination angle correction to transform the slip factor for centrifugal impeller to mixed-flow machine. (2) Setting up model that can be used to mixed-flow machine directly. Based on these two ways, there are six slip factor models chosen for mixed-flow impeller, including models of Wiesner, Stodola, Staniz, Paeng, Backstrom and Qiu. And they are need to be validated by experiments data to find a proper method for mixed-flow machine. The test data are reproduced from Wiesner’s work and nine mixed-flow impellers are included. Experiment and simulation (including six slip factors) have been conducted and the results show that: (1) slip factor models of centrifugal impeller can be used to mixed-flow impeller while no proper mixed-flow slip factor models exist. If the impeller discharge inclination angle is greater than 45 degree, then these models can be used for mixed-flow impellers directly without transformation. (2) Equivalent blade number exists in mixed-flow impeller and it may have critical value. There are only little differences between results calculated by various slip factor models in the condition of equivalent blade number beyond the critical value. Otherwise it has to choose proper slip factor models as different situations while the equivalent blade number is less than the critical value. (3) Blade number, impeller exit inclination angle and exit blade angle of mixed-flow impeller are dominated over slip factor, but blade turning rate and flow coefficient have to be taken into account for more exact solution.

A Transonic Mixed Flow Compressor for an Extreme Duty

2014 ◽  
Author(s):  
Hamid Hazby ◽  
Michael Casey ◽  
Ryusuke Numakura ◽  
Hideaki Tamaki
Keyword(s):  
Test Data ◽  
Pressure Rise ◽  
High Flow ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Aerodynamic Optimization ◽  
Mixed Flow ◽  
Axial Compressors ◽  
Blade Shape ◽  
Flow Compressor

This paper describes the design of a transonic mixed flow compressor stage for an extreme duty, with an extremely high flow coefficient (Φ) of 0.25 and a high isentropic pressure rise coefficient (ψ) of 0.56. The impeller design makes use of modern aerodynamic practice from radial and transonic axial compressors, whereby the aerodynamic blade shape involved arbitrary surfaces on several spanwise sections. Some aspects of the aerodynamic optimization of the design were limited by mechanical considerations, but nevertheless the test data obtained on a prototype stage demonstrates that acceptable performance levels can be achieved at these extreme design conditions, although map width enhancement devices were needed to obtain an acceptable operating range. The test data is compared with CFD predictions to demonstrate the validity of the design methods used.

A Transonic Mixed Flow Compressor for an Extreme Duty

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Hamid Hazby ◽  
Michael Casey ◽  
Ryusuke Numakura ◽  
Hideaki Tamaki
Keyword(s):  
Test Data ◽  
Pressure Rise ◽  
High Flow ◽  
Flow Coefficient ◽  
Aerodynamic Optimization ◽  
Mixed Flow ◽  
Axial Compressors ◽  
Blade Shape ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Compressor

This paper describes the design of a transonic mixed flow compressor stage for an extreme duty, with an extremely high flow coefficient (φ) of 0.25 and a high isentropic pressure rise coefficient (ψ) of 0.56. The impeller design makes use of modern aerodynamic practice from radial and transonic axial compressors, whereby the aerodynamic blade shape involved arbitrary surfaces on several spanwise sections. Some aspects of the aerodynamic optimization of the design were limited by mechanical considerations, but nevertheless the test data obtained on a prototype stage demonstrates that acceptable performance levels can be achieved at these extreme design conditions, although map width enhancement (MWE) devices were needed to obtain an acceptable operating range. The test data are compared with computational fluid dynamics (CFD) predictions to demonstrate the validity of the design methods used.

PRESSURE DISTRIBUTION ON THE BLADE SURFACE OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE UNDER PULSATING FLOW CONDITIONS

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
M.H. Padzillah ◽  
S. Rajoo ◽  
R.F. Martinez-Botas
Keyword(s):  
Weight Ratio ◽  
Pulsating Flow ◽  
World Population ◽  
Transportation Industry ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
Torque Generation ◽  
Computational Fluid Dynamics Cfd ◽  
Stroke Engine

The increment of the contribution to CO2 release by transportation industry as other sectors are decarbonizing is evident. As number of world population continue to increase, the task of developing highly downsized high power-to-weight ratio engines are critical. Over more than a hundred years of invention, turbocharger remains a key technology that enable highly boosted efficient engine. Despite its actual operating environment which is pulsating flow, the turbocharger turbine that is available to date is still designed and assessed under the assumption of steady flow conditions. This is attributable to the lack of understanding on the insight of the flow field effect towards the torque generation of the turbine blade under pulsating flow conditions. This paper presents an effort towards investigating the influence of pulsating flow on the blade loading and its differences from steady state conditions through the use of Computational Fluid Dynamics (CFD). For this purpose, a lean-vaned mixed-flow turbine with rotational speed of 30000 rpm at 20 Hz flow frequency, which represent turbine operation for 3-cylinder 4-stroke engine operating at 800 rpm has been used. Results presented in terms of spanwise location of the blade indicated different behavior at each location. Close to the hub, there are strong flow separation that hinders torque generation is seen while at mid-span more torque is generated under unsteady flow as compared to its steady counterpart. Moreover, close to the shroud, the pressure difference between steady and pulsating flow is almost identical

An Validation on A New Slip Factor Model for Mixed-flow Impellers

2008 ◽  
Author(s):  
Shengqin Huang ◽  
Zhenxia Liu ◽  
Yaguo Lu ◽  
Yan Yan ◽  
Xiaochun Lian
Keyword(s):  
Factor Model ◽  
Mixed Flow ◽  
Slip Factor

scholarly journals Introduction of an Universal Scale-Up Method for the Efficiency of Axial and Centrifugal Fans

2014 ◽  
Author(s):  
Peter F. Pelz ◽  
Stefan S. Stonjek
Keyword(s):  
Test Data ◽  
Scale Up ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Total Efficiency ◽  
Scaling Method ◽  
Centrifugal Fans ◽  
Axial Fans ◽  
Definition Of ◽  
Acceptance Tests

Acceptance tests on large fans to prove the performance (efficiency and total pressure rise) to the customer are expensive and sometimes even impossible to perform. Hence there is a need for the manufacturer to reliably predict the performance of fans from measurements on down-scaled test fans. The commonly used scale-up formulas give satisfactorily results only near the design point, where inertia losses are small in comparison to frictional losses. At part- and overload the inertia losses are dominant and the scale-up formulas used so far fail. In 2013 Pelz and Stonjek introduced a new scaling method which fullfills the demands ( [1], [2]). This method considers the influence of surface roughness and geometric variations on the performance. It consists basically of two steps: Initially, the efficiency is scaled. Efficiency scaling is derived analytically from the definition of the total efficiency. With the total derivative it can be shown that the change of friction coefficient is inversely proportional to the change of efficiency of a fan. The second step is shifting the performance characteristic to a higher value of flow coefficient. It is the task of this work to improve the scaling method which was previously introduced by Pelz and Stonjek by treating the rotor/impeller and volute/stator separately. The validation of the improved scale-up method is performed with test data from two axial fans with a diameter of 1000 mm/250mm and three centrifugal fans with 2240mm/896mm/224mm diameter. The predicted performance characteristics show a good agreement to test data.

An assessment of a new model of dynamic fragmentation of soil with test data

2012 ◽  
Vol 120 ◽  
pp. 61-68 ◽  
Author(s):  
A.S. Gregory ◽  
N.R.A. Bird ◽  
C.W. Watts ◽  
A.P. Whitmore
Keyword(s):  
Test Data ◽  
New Model ◽  
Dynamic Fragmentation

Loss and Flow Path Studies on Centrifugal Compressors—Part II

1970 ◽  
Vol 92 (3) ◽  
pp. 287-300 ◽  
Author(s):  
O. E. Balje´
Keyword(s):  
Boundary Layer ◽  
High Efficiency ◽  
Flow Path ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Mixed Flow ◽  
Path Design ◽  
Balanced Flow ◽  
Efficiency Data ◽  
Rotor Flow

The flow conditions in a mixed flow rotor are investigated for a “pressure balanced” flow path design. Boundary layer arguments are applied to calculate the losses in the rotor as well as in the subsequent diffuser section. The resulting efficiency data imply a comparatively high efficiency potential for mixed flow compressors with multiple cascaded components, designed on the premise of a “pressure balanced” rotor flow path.

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