Improvement in Efficiency and Stall Margin of Centrifugal Blower Impeller by Multi-Objective Optimization

2011 ◽  
Author(s):  
Kiyotaka Hiradate ◽  
Takahiro Nishioka ◽  
Toshio Kanno ◽  
Kazuyuki Sugimura ◽  
Yasushi Shinkawa ◽  
...  
Keyword(s):  
Flow Rate ◽  
Flow Separation ◽  
Optimization Technique ◽  
Design Flow ◽  
Flow Coefficient ◽  
Multi Objective Optimization ◽  
Suction Surface ◽  
Stall Margin ◽  
Multi Objective ◽  
Design Flow Rate

We investigated a multi-objective optimization technique that can control a trade-off relationship between the efficiency and the stall margin of two-dimensional impellers using only a calculation result at the design flow rate. The suction flow coefficient at the design flow rate of the impeller we designed was 0.04. We used a multi-objective genetic algorithm and three-dimensional steady Reynolds Averaged Navier-Stokes (RANS) simulation with a blade-to-blade passage in the optimization. To determine a flow field index that can evaluate the stall margin of an impeller, the inner flows of two impellers were investigated. Results showed that the throat deceleration ratio correlates with the inception flow rate of the flow separation that occurs on the blade suction surface in the shroud side near the throat surface. Here, the throat deceleration ratio means a ratio of the relative velocity at the inlet to that at the throat surface in the shroud side of the impeller. We selected the adiabatic efficiency and the throat deceleration ratio at the design flow rate as the objective functions and performed an optimization. A 1.8% improvement in the efficiency and a 5% improvement in the stall margin were demonstrated in the optimized impeller from the detailed calculations. Moreover, it was found that an additional objective function was required to control the flow separation caused by the excessive increase of the blade loading in the rear part of the impeller.

scholarly journals РЕЗУЛЬТАТЫ УСОВЕРШЕНСТВОВАНИЯ СТУПЕНИ ВЫСОКОНАГРУЖЕННОЙ ТУРБИНЫ НИЗКОГО ДАВЛЕНИЯ

2019 ◽  
pp. 30-37
Author(s):  
Игорь Федорович Кравченко ◽  
Сергей Александрович Хомылев
Keyword(s):  
Flow Separation ◽  
Wedge Angle ◽  
Operating Conditions ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Energy Losses ◽  
Suction Surface ◽  
Experimental Development ◽  
Leading Edges

One of the characteristic features of high loaded low-pressure turbine (LPT) with a low flow coefficient is the high-level flow deflection in the blade rows, which have sufficiently thin and strongly curved cross-section profiles. Such profiles are very sensitive to off-design flow angles, especially to positive incidence. Therefore, the effectiveness of a high loaded LPT strongly depends on the working conditions. At the same time, for various reasons, in the process of research tests or operating the engine, the operating conditions may differ greatly from the design ones. Therefore, the creation of a robust LPT design is an actual task. The article considers the computational approbation of the method of increasing the resistance to large off-design angles of attack of vane and blade rows of the intermediate stage of a high loaded LPT of an experimental engine by changing the shape of the leading edges. The turbine was previously tested as part of a full-scale engine, where it was determined that the operating conditions of the LPT and its efficiency are significantly different from the calculated ones. Numerical (CFD) analysis of the flow showed that one of the reasons for the low efficiency is the large angles of attack on the vane and blade rows of the second stage, which lead to the flow separation and an increase of the energy losses coefficients at final. The modernization of the profiles was carried out by reducing the radius and a local increase of the leading edges wedge angle without changing the basic profiles. According to the calculation results, it was allowed to significantly improve the stream. The intensity of the flow deceleration behind the shock wave at the point of transition from the circumference of the edge to the suction surface was reduced, this made it possible to eliminate or reduce the intensity of the flow separation in the vane row and significantly reduce the energy losses coefficient. A more favorable flow was also achieved in the blade row, where a slight decrease in the losses coefficient was also obtained. As a result, the efficiency of the stage and the whole LPT was increased at the off-design operating conditions. This approach can be recommended both to increase the efficiency of the turbine at the experimental development, and when designing new turbines to increase their robustness.

Multipoint Multi-Objective Optimization of a Low Solidity Circular Cascade Diffuser in Centrifugal Blowers

2014 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Hiroshi Hayami ◽  
Lasse Mueller ◽  
Zuheyr Alsalihi ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Flow Rate ◽  
Flow Separation ◽  
Multi Objective Optimization ◽  
Rate Condition ◽  
Flow Effect ◽  
Design Point ◽  
Operating Range ◽  
Multi Objective ◽  
Small Flow

In radial compressors or blowers, a low solidity circular cascade diffuser (LSD) is one of the effective devices to improve the pressure recovery at design flow rate while guaranteeing a wide operating range. The improvement is mainly attributed to the so called secondary flow effect, which reduces the flow separation on the LSD blade at small flow rates. However, it is very difficult to find out the effective shape of the blade in order to promote this secondary flow effect. In this paper, a multipoint and multi-objective optimization technique is applied to design the LSD blade of a centrifugal blower. The optimization method has been developed at the von Karman Institute for Fluid Dynamics (VKI), which makes use of an evolutionary algorithm, a metamodel as a rapid exploration tool, and a high fidelity 3D Navier-Stokes solver. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Seven detailed design parameters describing the shape and position of the LSD vane were introduced, e.g. the radial spacing between impeller exit and the LSD leading edge, the radial chord length and the mean camber angle distribution of the LSD blade with five control points. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect. This is fully corresponding to the CFD predictions and demonstrates the effectiveness of the optimization methodology, by limiting the experimental testing to only two geometries.

Multi-objective optimization of squirrel cage fan for range hood based on Kriging model

2021 ◽  
pp. 095440622199586
Author(s):  
Qianhao Xiao ◽  
Jun Wang ◽  
Boyan Jiang ◽  
Weigang Yang ◽  
Xiaopei Yang
Keyword(s):  
Flow Rate ◽  
Optimization Design ◽  
Volume Flow Rate ◽  
Kriging Model ◽  
Volume Flow ◽  
Design Parameters ◽  
Multi Objective Optimization ◽  
Nsga Ii ◽  
Multi Objective ◽  
Squirrel Cage

In view of the multi-objective optimization design of the squirrel cage fan for the range hood, a blade parameterization method based on the quadratic non-uniform B-spline (NUBS) determined by four control points was proposed to control the outlet angle, chord length and maximum camber of the blade. Morris-Mitchell criteria were used to obtain the optimal Latin hypercube sample based on the evolutionary operation, and different subsets of sample numbers were created to study the influence of sample numbers on the multi-objective optimization results. The Kriging model, which can accurately reflect the response relationship between design variables and optimization objectives, was established. The second-generation Non-dominated Sorting Genetic algorithm (NSGA-II) was used to optimize the volume flow rate at the best efficiency point (BEP) and the maximum volume flow rate point (MVP). The results show that the design parameters corresponding to the optimization results under different sample numbers are not the same, and the fluctuation range of the optimal design parameters is related to the influence of the design parameters on the optimization objectives. Compared with the prototype, the optimized impeller increases the radial velocity of the impeller outlet, reduces the flow loss in the volute, and increases the diffusion capacity, which improves the volume flow rate, and efficiency of the range hood system under multiple working conditions.

Enhancement of Labyrinth Seals Efficiency by Means of a Multi-Objective Optimization Technique

2018 ◽  
Author(s):  
Mikhail Gritckevich ◽  
Kunyuan Zhou ◽  
Vincent Peltier ◽  
Markus Raben ◽  
Olga Galchenko
Keyword(s):  
Optimization Technique ◽  
Leakage Flow ◽  
Multi Objective Optimization ◽  
Labyrinth Seals ◽  
Engine Operation ◽  
Turbine Engine ◽  
Multi Objective ◽  
Single Objective ◽  
Ansys Workbench ◽  
Comprehensive Study

A comprehensive study of several labyrinth seals has been performed in the framework of both single-objective and multi-objective optimizations with the main focus on the effect of stator grooves formed due to the rubbing during gas turbine engine operation. For that purpose, the developed optimization workflow based on the DLR-AutoOpti optimizer and ANSYS-Workbench CAE environment has been employed to reduce the leakage flow and windage heating for several seals. The obtained results indicate that the seal designs obtained from optimizations without stator grooves have worse performance during the lifecycle than those with the stator grooves, justifying the importance of considering this effect for real engineering applications.

scholarly journals Power Loss Calculation in 11-Level Cascaded H-Bridge Inverter using Harmony Search Optimized Switching Scheme

2019 ◽  
Vol 8 (6) ◽  
pp. 5200-5205
Keyword(s):  
Optimization Algorithm ◽  
Power Loss ◽  
System Analysis ◽  
Search Algorithm ◽  
Optimization Technique ◽  
Harmony Search ◽  
Multilevel Inverter ◽  
Total Power ◽  
Multi Objective Optimization ◽  
Multi Objective

Power loss is the most significant parameter in power system analysis and its adequate calculation directly effects the economic and technical evaluation. This paper aims to propose a multi-objective optimization algorithm which optimizes dc source magnitudes and switching angles to yield minimum THD in cascaded multilevel inverters. The optimization algorithm uses metaheuristic approach, namely Harmony Search algorithm. The effectiveness of the multi-objective algorithm has been tested with 11-level Cascaded H-Bridge Inverter with optimized DC voltage sources using MATLAB/Simulink. As the main objective of this research paper is to analyze total power loss, calculations of power loss are simplified using approximation of curves from datasheet values and experimental measurements. The simulation results, obtained using multi-objective optimization method, have been compared with basic SPWM, optimal minimization of THD, and it is confirmed that the multilevel inverter fired using multi- objective optimization technique has reduced power loss and minimum THD for a wide operating range of multilevel inverter.

scholarly journals Single- and Multi-Objective Optimization of a Dual-Chamber Microbial Fuel Cell Operating in Continuous-Flow Mode at Steady State

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 839
Author(s):  
Ibrahim M. Abu-Reesh
Keyword(s):  
Flow Rate ◽  
Pareto Optimal ◽  
Pareto Optimal Solutions ◽  
Optimal Solutions ◽  
Multi Objective Optimization ◽  
Dual Chamber ◽  
Worst Case ◽  
Multi Objective ◽  
Model Based ◽  
Conflicting Objectives

Microbial fuel cells (MFCs) are a promising technology for bioenergy generation and wastewater treatment. Various parameters affect the performance of dual-chamber MFCs, such as substrate flow rate and concentration. Performance can be assessed by power density ( PD ), current density ( CD ) production, or substrate removal efficiency ( SRE ). In this study, a mathematical model-based optimization was used to optimize the performance of an MFC using single- and multi-objective optimization (MOO) methods. Matlab’s fmincon and fminimax functions were used to solve the nonlinear constrained equations for the single- and multi-objective optimization, respectively. The fminimax method minimizes the worst-case of the two conflicting objective functions. The single-objective optimization revealed that the maximum PD ,   CD , and SRE were 2.04 W/m2, 11.08 A/m2, and 73.6%, respectively. The substrate concentration and flow rate significantly impacted the performance of the MFC. Pareto-optimal solutions were generated using the weighted sum method for maximizing the two conflicting objectives of PD and CD in addition to PD and SRE   simultaneously. The fminimax method for maximizing PD and CD showed that the compromise solution was to operate the MFC at maximum PD conditions. The model-based optimization proved to be a fast and low-cost optimization method for MFCs and it provided a better understanding of the factors affecting an MFC’s performance. The MOO provided Pareto-optimal solutions with multiple choices for practical applications depending on the purpose of using the MFCs.

scholarly journals Modeling Study of Design Flow Rates for Cascade Water Supply Systems in Residential Skyscrapers

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2580
Author(s):  
Yang Zhou ◽  
Eric Lee ◽  
Ling-Tim Wong ◽  
Kwok-Wai Mui
Keyword(s):  
Water Supply ◽  
Mathematical Models ◽  
Flow Rate ◽  
Supply System ◽  
Water Supply System ◽  
Design Flow ◽  
Water Volume ◽  
Water Supply Systems ◽  
Supply Systems ◽  
Design Flow Rate

Skyscrapers are common nowadays around the world, especially in cities with limited development area. In order to pump water up to the higher level of a skyscraper, a cascade water supply system has to be installed. Currently, cascade water supply systems are mainly designed based on practical experiences or requirements of existing standards/guidelines that, in fact, are not specifically for skyscrapers. However, thorough studies on cascade water supply system designs are still limited in the literature. This study proposes mathematical models and uses Monte Carlo simulations to evaluate the design flow rate of a typical cascade water supply system that feeds various appliances in a residential skyscraper in Hong Kong. Graphs that showed the correlations between the inflow rate in the supply pipe and water volume in the tank are obtained. While tank storage volume is confirmed, the design flow rate of the cascade water supply system can be determined from these graphs. The proposed mathematical models can also be applied to evaluate the design flow rate of cascade water supply systems in other types of skyscrapers (e.g., office, commercial building) as well as with the changes in water demand patterns in the models.

scholarly journals Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 126
Author(s):  
Houlin Liu ◽  
Ruichao Xia ◽  
Kai Wang ◽  
Yucheng Jing ◽  
Xianghui He
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Dominant Frequency ◽  
Design Flow ◽  
Signal Source ◽  
Vaned Diffuser ◽  
Impeller Outlet ◽  
Variation Tendency ◽  
Design Flow Rate

Experimental measurements to analyze the pressure fluctuation performance of a centrifugal pump with a vaned-diffuser, which its specific speed is 190. Results indicate that the main cause of pressure fluctuation is the rotor-stator interference at the impeller outlet. The head of the pump with vaned-diffuser at the design flow rate is 15.03 m, and the efficiency of the pump with a vaned-diffuser at the design flow rate reaches 71.47%. Pressure fluctuation decreases gradually with increasing distance from the impeller outlet. Along with the increase of the flow rate, amplitude of pressure fluctuation decreases. The amplitude of pressure fluctuation at the measuring points near the diffusion section of the pump body is larger than other measuring points. The variation tendency of pressure fluctuation at P1–P10 is the same, while there are wide frequency bands with different frequencies. The dominant frequency of pressure fluctuation is the blade passing frequency. The rotor-stator interference between the impeller and the vaned-diffuser gives rise to the main signal source of pressure fluctuation.

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