Mean Streamline Analysis Research Articles

An Algorithm for the Design of an Axial Flow Compressor of a Power Generation Gas Turbine

This paper focuses on the development of an algorithm for designing an axial flow compressor for a power generation gas turbine and attempts to bring to the public domain some parameters regarded as propriety data by plant manufacturers. The theory used in this work is based on simple thermodynamics and aerodynamics principles in a mean stream line analysis that assumes that the flow conditions prevailing at the mean radius fully represent the flow at all other radii. Gas Turbine Unit II (GT-II) in Omotosho Power Plant Phase I located in Ondo state was used to validate this work. The specifications used include mass flow rate, rotational speed, number of stages, pressure ratio, ambient air temperature and pressure etc. A computer program was written based on the formulated algorithm and the code was implemented in Microsoft Excel. The axial velocity was obtained using an iterative process that converged to a value of 163.74m/s for the design condition. The blade camber angles for each stage of the compressor were also determined using iterative processes. The results showed a compressor overall stagnation temperature rise of 354.5 0 C and work input of 51.5MW at an ambient air temperature of 15 0 C. The stagnation temperature rise and compressor work input were computed to be 369 0 C and 53.6MW respectively at an ambient air temperature of 27 0 C and which agrees reasonably well with the measured values of 375 0 C and 54.6MW in GT-II. The total to total efficiency was 0.86 for both ambient air temperature values. http://dx.doi.org/10.4314/njt.v34i2.16

Optimization of Loss Models for Centrifugal Compressor Performance Prediction Based on Numerical Analysis Results

An optimization of loss models for performance prediction of centrifugal compressors has been conducted in this paper. A centrifugal compressor with vaneless diffuser (VLD) and vaned diffuser (VD) is selected for the present study. The study begins with a numerical analysis, using commercial software ANSYS CFX. The numerical result is used to modify mean streamline analysis loss models. Matlab optimization toolbox is used for this purpose. Also, a matlab program is compiled to calculate the off-design performance of the centrifugal compressor. The results show that after optimizating the loss models, mean streamline analysis has a better accuracy than before.

Mean streamline analysis for performance prediction of cross-flow fans

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

A practical approach to the hydraulic design and performance analysis of a mixed-flow pump for marine waterjet propulsion

The hydraulic design optimization and performance analysis of a mixed-flow pump for marine waterjet propulsion has been carried out using mean streamline analysis and three-dimensional computational fluid dynamics (CFD) code. In the present study, conceptual design optimization has been formulated with a nonlinear objective function to minimize fluid dynamic losses and then a commercial CFD code was incorporated to allow for detailed flow dynamic phenomena in the pump system. The newly designed mixedflow model pump has been tested in the laboratory. Predicted performance curves by the CFD code agree fairly well with experimental data for a newly designed mixed-flow pump over the normal operating conditions. The design and prediction methods presented herein can be used efficiently as a unified hydraulic design process of mixed-flow pumps for marine waterjet propulsion.

워터제트 선박추진용 사류펌프의 설계 및 성능해석

The hydraulic design optimization and performance analysis of mixed-flow pumps for waterjet marine vehicle propulsion has been carried out using mean streamline analysis and three-dimensional computational fluid dynamics (CFD) code. In the present study, the conceptual design optimization has been formulated with a non-linear objective function to minimize the fluid dynamic losses, and then the commercial CFD code was incorporated to allow for detailed flow dynamic phenomena in the pump system. Newly designed mixed-flow model pump has been tested in the laboratory. Predicted performance curves by the CFD code agree very well with experimental data for a newly designed mixed-flow pump over the normal operating conditions. The design and prediction method presented herein can be used efficiently as a unified hydraulic design process of mixed-flow pumps for waterjet marine vehicle propulsion.

유전적 최적화 기법을 이용한 축류 펌프의 설계

The optimal design code of an axial flow pump has been developed to determine geometric and fluid dynamic variables under hydrodynamic as well as mechanical design constraints. The design code includes the optimization of the complete radial distribution of the geometry by determining the coefficients of 2nd order polynomials to represent the three-dimensional geometry. The optimization problem has been formulated with a nonlinear multivariable objective function. maximizing the efficiency and stall margin. while minimizing the net positive suction head required. Calculation of the objective function is based on the mean streamline analysis and through-flow analysis using the present state-of-the-art model. The optimal solution is calculated using the penalty function method in which the genetic optimizer is employed. The optimized efficiency and design variables are presented in this paper as a function of non-dimensional specific speed in the range, 2≤㎱≤10. The results can be used in preliminary design of axial flow pumps.<br/>

Systematic two-zone modelling for performance prediction of centrifugal compressors

This paper presents systematic two-zone modelling for reliable performance prediction of centrifugal compressors. In order to improve the predictive capability, a modified jet slip factor is developed and new corrections for the wake flow deviation and mass fraction are suggested on the basis of the comprehensive experimental data of the three Eckardt impellers. The proposed two-zone modelling is tested against nine sets of measured data of centrifugal compressors. The results are also compared with those obtained by mean streamline analysis. It was found that the predictions by the present two-zone modelling agree fairly well with experimental data for a variety of centrifugal compressors over the wide operating conditions.

Mean streamline performance analysis of mixed-flow fan impellers covering the low flowrate characteristics

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and a suction recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.

Conceptual design optimization of mixed-flow pump impellers using mean streamline analysis

A conceptual design optimization code for mixed-flow pump impellers has been developed to determine the geometric and fluid dynamic variables under appropriate design constraints. In the present study the optimization problem has been formulated with a non-linear objective function to minimize the fluid dynamic losses. The optimal solution is obtained by means of the Hooke-Jeeves direct search method. Computations are performed using mean streamline analysis and the present state-of-the-art loss correlations. Changes in the optimized efficiency and design variables of mixed-flow pump impellers are presented in this paper as a function of non-dimensional specific speed in the range 1.9 ≤ Ns ≤ 2.5. The diagrams presented herein can be used efficiently in the preliminary design phase of mixed-flow pump impellers.

Performance Prediction of Cross‐Flow Fans Using Mean Streamline Analysis

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross‐flow fans. Comparison of overall performance predictions with test data of a cross‐flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross‐flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross‐flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general‐purpose cross‐flow fans.

Optimum values of design variables versus specific speed for centrifugal pumps

An optimal design code for centrifugal pumps has been developed to determine the geometric and fluid dynamic variables under appropriate design constraints. The optimization problem has been formulated with a non-linear objective function to minimize one, two or all of the fluid dynamic losses, the net positive suction head required and the product price of a pump stage depending on the weighting factors selected as the design compromise. The optimal solution is obtained by means of the Hooke-Jeeves direct search method. The performance analysis is based on the mean streamline analysis using the present state-of-the-art loss correlations. The optimized efficiency and design variables of centrifugal pumps are presented in this paper as a function of non-dimensional specific speed in the range, 0.5 ≤ Ns ≤ 1.3. The diagrams presented herein can be used efficiently in the preliminary design phase of centrifugal pumps.

Performance prediction of mixed-flow pumps

This paper presents the mean streamline analysis using the empirical loss models for performance prediction of mixed-flow pumps with high specific speeds. A new internal loss model to describe the effect of flow separation on the characteristic head-capacity curve with a dip in the low flow range is developed and a modified recirculation loss model for calculation of parasitic loss due to flow recirculation at the impeller exit is suggested in this study. The prediction performance of the proposed method here is tested against four sets of measured total heads and efficiencies of mixed-flow pumps, and it is also compared with that based on two-dimensional cascade theory. Predicted results by the present set of loss models agree very well with experimental data for a variety of mixed-flow pumps over the normal operating conditions.

Experimental and Theoretical Analysis of the Flow in a Centrifugal Compressor Volute

Detailed measurements of the swirling flow in a centrifugal compressor volute with elliptical cross section are presented. They show important variations of the swirl and throughflow velocity, total and static pressure distribution at the different volute cross sections and at the diffuser exit. The basic mechanisms defining the complex three dimensional flow structure are clarified. The different sources of pressure loss have been investigated and used to improve the prediction capability of one-dimensional mean streamline analysis correlations. The tangential flow loss model under decelerating flow conditions and the friction loss model are confirmed. New empirical loss coefficients are proposed for the exit cone loss model and the tangential flow loss model for the case of accelerating flow in the volute.

Performance prediction of multi element torque converters

An analysis procedure for predicting the performance of multi-element torque converters is presented. The analysis has been formulated and programmed so that any hydrokinetic device from a two element fluid coupling to an ‘ n’ element torque converter can be handled. The procedure is based upon a mean streamline analysis with the rate of circulation of the fluid calculated in an iterative manner with the aid of empirical loss models. The program structure is such that any number of bladed and unbladed components can be included, and the empirical loss models used can be readily modified and updated as necessary. The procedure is varified by comparison firstly with experimental performance and direct prediction of three element torque converters, and secondly by comparison with published five element torque converter performance.