Blade Thickness Effect on Impeller Slip Factor

2010 ◽  
Author(s):  
Donghui Zhang ◽  
Jean-Luc Di Liberti ◽  
Michael Cave
Keyword(s):  
Factor Model ◽  
Numerical Study ◽  
Flow Direction ◽  
Leading Edge ◽  
Thickness Effect ◽  
Centrifugal Impeller ◽  
Trailing Edge ◽  
Slip Factor ◽  
Blade Thickness ◽  
Blockage Factor

A numerical study of the effect of the blade thickness on centrifugal impeller slip factor is presented in this paper. The CFD results show that generally the slip factor decreases as the blade thickness increases. Changing the thickness at different locations has different effects on the slip factor. The shroud side blade thickness has more effect on the impeller slip factor than the hub side blade thickness. In the flow direction, the blade thickness at 50% meridional distance is the major factor affecting the slip factor. The leading edge thickness has little effect on slip factor. There is an optimum thickness at the trailing edge for the maximum slip factor. For this impeller, the hub side thickness ratio of 0.5 between the trailing edge and the middle of the impeller gives the highest value of the slip factor, while the ratio of 0.25 at shroud side gives the highest value of the slip factor. A blockage factor is added into the slip factor model to include the aerodynamic blockage effect on the slip factor. The model explains the phenomena observed in the CFD results and the test data very well.

Trailing Edge Filings and a Modified Stodola’s Slip Factor for Centrifugal Impeller

2015 ◽  
Author(s):  
Guang Xi ◽  
Huijing Zhao ◽  
Zhiheng Wang
Keyword(s):  
Numerical Simulations ◽  
Good Accuracy ◽  
Centrifugal Impeller ◽  
Pressure Side ◽  
Compressor Stage ◽  
Trailing Edge ◽  
Obvious Effect ◽  
Quantitative Calculation ◽  
Slip Factor ◽  
Stage Efficiency

The paper investigates the effect of trailing edge filing in the impeller on the performances of impeller and compressor stage. The 3D viscous numerical simulations are carried out under different positions, thicknesses and lengths of filing. The results show that, the filing on the trailing edge has an obvious effect on the pressure ratios of impeller and compressor stage. The trailing edge filing has little effect on the impeller efficiency while the filing on the pressure side is favorable to improving the stage efficiency. Then, through correcting the blade angles at the suction and pressure sides, considering the viscosity and 3D characteristics of the flow, a modified slip factor formula is proposed for the centrifugal impeller with a trailing edge filing. The validation to the proposed formula shows that the proposed formula can be used to predict the slip factors of different filing cases with a good accuracy. It can provide a theoretical guidance for the quantitative calculation when using the filing technology to improve the performance of centrifugal impeller as well as the stage.

scholarly journals Numerical Study of Sediment Erosion Analysis in Francis Turbine

2019 ◽  
Vol 11 (5) ◽  
pp. 1423 ◽  
Author(s):  
Md Rakibuzzaman ◽  
Hyoung-Ho Kim ◽  
Kyungwuk Kim ◽  
Sang-Ho Suh ◽  
Kyung Kim
Keyword(s):  
Erosion Rate ◽  
Cavitation Erosion ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Trailing Edge ◽  
Sand Erosion ◽  
Turbine Design

Effective hydraulic turbine design prevents sediment and cavitation erosion from impacting the performance and reliability of the machine. Using computational fluid dynamics (CFD) techniques, this study investigated the performance characteristics of sediment and cavitation erosion on a hydraulic Francis turbine by ANSYS-CFX software. For the erosion rate calculation, the particle trajectory Tabakoff–Grant erosion model was used. To predict the cavitation characteristics, the study’s source term for interphase mass transfer was the Rayleigh–Plesset cavitation model. The experimental data acquired by this study were used to validate the existing evaluations of the Francis turbine. Hydraulic results revealed that the maximum difference was only 0.958% compared with the CFD data, and 0.547% compared with the experiment (Korea Institute of Machinery and Materials (KIMM)). The turbine blade region was affected by the erosion rate at the trailing edge because of their high velocity. Furthermore, in the cavitation–erosion simulation, it was observed that abrasion propagation began from the pressure side of the leading edge and continued along to the trailing edge of the runner. Additionally, as sediment flow rates grew within the area of the attached cavitation, they increased from the trailing edge at the suction side, and efficiency was reduced. Cavitation–sand erosion results then revealed a higher erosion rate than of those of the sand erosion condition.

Study of Particle Ingestion Through Two-Stage Gas Turbine

2014 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Solid Particles ◽  
Two Stage ◽  
Trailing Edge ◽  
Erosion Rates ◽  
Tracking Model ◽  
Over The Top

This paper presents a numerical study of particle laden gas flow through a two-stage hp axial turbine, by means of an in-house code based on the Lagrangian tracking model and the finite element method. As fly-ash solid particles trajectories and locations of impacts are predicted, the local erosion rates and the deteriorations of blades are assessed. The computed trajectories provide a detailed description of particles behaviors and reveal that particle impacts on the aft of vane pressure side usually lead to significant variations in the directions of particles to the next rotor blade, and subsequently particles impact the suction side. The plots of equivalent erosion rates indicate the vanes and blades locations which suffer more erosion. The first vane pressure surface is impacted more than any other component, but higher rates are seen at the top corner from trailing edge. The critical regions of erosion wear in the first rotor are observed over the top of blade leading edge extending along the tip as well as a rounding of the top corner from trailing edge. In the second vane, the regions of higher erosion are revealed over the last third of leading edge and the top corner extending along tip. The erosion in the second rotor is over a large area of suction side till the tip corner. The predicted areas of extreme erosion, also shown by the deteriorated profiles, are indicators for anticipated vanes and blades failures.

Effect of Blade Thickness on High Frequency Gust Response

2005 ◽  
Author(s):  
Peter D. Lysak
Keyword(s):  
High Frequency ◽  
Incompressible Flows ◽  
Leading Edge ◽  
Step Function ◽  
Rotor Blades ◽  
Thickness Effect ◽  
Mean Velocity ◽  
Blade Thickness ◽  
Gust Response ◽  
Unsteady Lift

Turbomachinery rotor blades experience gust loading due to both inflow turbulence and circumferential variation in the mean velocity. The unsteady lift forces that result from these velocity disturbances can be a source of unwanted vibration and radiated noise. For incompressible flows, the blade gust response is often modeled using the well-known Sears function, which acts as a transfer function between a sinusoidal component of the gust and the fluctuating lift. However, the Sears function has a relatively slow high frequency roll-off and overpredicts the unsteady lift when the gust wavelength becomes much smaller than the blade chord. A more accurate model can be obtained by including the effect of blade thickness, which causes the gust to become distorted as it approaches the leading edge. This distortion results in attenuation of the higher-frequency components of the gust near the leading edge, which subsequently leads to reduced unsteady lift. In this paper, a model for the thickness effect is developed based on rapid distortion theory. Numerical calculations are made for a step-function gust encountering an elliptical leading edge with several thickness-to-chord ratios. The unsteady lift is calculated in the time domain, and a Fourier transform is used to obtain the frequency response. The results indicate that the gust response of a thick blade can be closely approximated by modifying the Sears function to include an exponential decay factor based on the thickness.

Application of a CFD-Based Program for the Optimization of a Centrifugal Impeller

2003 ◽  
Author(s):  
Simone Pazzi ◽  
Francesco Martelli ◽  
Marco Giachi ◽  
Michela Testa
Keyword(s):  
New Technologies ◽  
Leading Edge ◽  
Computational Effort ◽  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Geometrical Parameters ◽  
Design Point ◽  
Blade Thickness ◽  
Geometrical Constraints

A typical centrifugal impeller characterized by a low flow coefficient and cylindrical blades is redesigned by means of an intelligent automatic search program. The procedure consists of a Feasible Sequential Quadratic Programming (FSQP) algorithm [6] coupled to a Lazy Learning (LL) interpolator [1] to speed-up the process. The program is able to handle geometrical constraints to reduce the computational effort devoted to the analysis of non-physical configurations. The objective function evaluator is an in-house developed structured CFD code. The LL approximator is called each time the stored database can provide a sufficiently accurate performance estimate for a given geometry, thus reducing the effective CFD computations. The impeller is represented by 25 geometrical parameters describing the vane in the meridional and s-θ planes, the blade thickness and the leading edge shape. The optimisation is carried out on the impeller design point maximizing the polytropic efficiency with more or less constant flow coefficient and polytropic head. The optimization is accomplished keeping unaltered those geometrical parameters which have to be kept fixed in order to make the impeller fit the original stage. The optimisation, carried out on a cluster of sixteen PCs, is self-learning and leads to a geometry presenting an increased design point efficiency. The program is completely general and can be applied to any component which can be described by a finite number of geometrical parameters and computed by any numerical instrument to provide performance indices. The work presented in this paper has been developed inside the METHOD EC funded project for the implementation of new technologies for optimisation of centrifugal compressors.

Three-Dimensional Flow Analysis and Improvement of Slip Factor Model for Forward-Curved Blades Centrifugal Fan

2003 ◽  
Author(s):  
En-Min Guo ◽  
Kwang-Yong Kim
Keyword(s):  
Factor Model ◽  
Pressure Coefficient ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Correction Method ◽  
Factor Models ◽  
Centrifugal Impeller ◽  
Centrifugal Fan ◽  
Slip Factor ◽  
Cfd Analyses

The objective of this work is to develop improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan by investigating the validity of various slip factor models. Both steady and unsteady three-dimensional CFD analyses were performed with a commercial code to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the presented model takes into account the effect of blade curvature. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.

Numerical Study on Three-Dimensional Optimization of a Low-Speed Axial Compressor Rotor

2014 ◽  
Author(s):  
Chenkai Zhang ◽  
Jun Hu ◽  
Zhiqiang Wang ◽  
Chao Yin ◽  
Wei Yan
Keyword(s):  
Numerical Optimization ◽  
Large Scale ◽  
Numerical Study ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Trailing Edge ◽  
Compressor Rotor ◽  
Flow Loss

This paper presents numerical optimization of a compressor rotor, to deepen the knowledge of endwall flow in the large-scale axial subsonic compressor, accordingly reduce its endwall loss and improve its aerodynamic performance. With numerical simulation and numerical optimization tools, three-dimensional stacking principle is optimized to improve the design operation point performance for the rotor. Results show that, hub region of the rotor cannot undertake large blade loading; compared to the prototype rotor, obvious aerodynamic performance improvements locate near the hub area, and a certain degree of positive dihedral in this region effectively helps to reduce its flow loss. The effect of “loaded leading edge and unloaded trailing edge” due to positive dihedral was shown, which suppresses flow separation near the trailing edge, consequently obviously reduces the flow loss and largely improves the rotor aerodynamic performance.

Flow in a Turbine Cascade: Part 1—Losses and Leading-Edge Effects

1984 ◽  
Vol 106 (2) ◽  
pp. 400-407 ◽  
Author(s):  
J. Moore ◽  
A. Ransmayr
Keyword(s):  
Large Scale ◽  
Static Pressure ◽  
Flow Direction ◽  
Turbine Blades ◽  
Leading Edge ◽  
Turbine Cascade ◽  
Trailing Edge ◽  
Linear Cascade ◽  
High Loss ◽  
Downstream Flow

An experimental investigation was conducted to study the effect of the leading-edge shape on the overall losses in a large-scale linear cascade of turbine blades. The leading-edge shapes used were a cylinder and a wedge. The cascade was designed to be geometrically similar to the cascade used by Langston et al. at United Technologies Research Center, with the same span/chord and pitch/chord ratios. Measurements of wall static pressure on the blades and of total pressure and flow direction downstream of the cascade showed only minor changes due to the alteration of the leading-edge shape. The measurements of the flow and loss distributions downstream of the cascade complement the results of Langston et al., which showed the flow development only within the cascade. The downstream flow is important, however, as apppoximately 50 percent of the losses occur downstream of the trailing edge. Regions of high loss were found near midspan at an axial location 40 percent of the axial chord downstream of the trailing edge. The sources of fluid in these regions are determined in Part 2.

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.

Numerical Investigation of the Influence of the Tip Clearance on Wake Formation Inside a Radial Impeller

2003 ◽  
Author(s):  
Carsten Weiß ◽  
Daniel R. Grates ◽  
Hans Thermann ◽  
Reinhard Niehuis
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Trailing Edge ◽  
Flow Solver ◽  
Small Height ◽  
Wake Formation

The objective of the presented work is to investigate the influence of the tip clearance on the wake formation inside a radial impeller. The position and size of the wake region does not only depend on the clearance height, but also on the distribution of the clearance gap along the blade chord. In order to examine this influence, several calculations have been performed with a three dimensional Navier-Stokes flow solver on a centrifugal impeller, which was experimentally investigated in much detail at Aachen University. The original clearance gap was 0.7 mm at the leading edge and 0.48 mm at the trailing edge. These values were independently varied in the computations, such that different distributions of clearance heights could be chosen. The wake position of the smallest clearance height at the leading and trailing edge was closest to the pressure side. The calculations show, that a relatively large clearance height at the leading edge combined with a small height at the trailing edge move the wake further to the suction side, which corresponds very well with the experimental results. Reasons for that behavior are discussed in the paper.

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