Optimum Number Of Blades Research Articles

Numerical modeling and CFD simulation of diffuser augmented dual vertical axis hydrokinetic Banki-Michell turbine

Hydrokinetic Banki turbines present an affordable, technically feasible, environmentally friendly technology. Their construction without requiring more expensive structures like diversion weirs, canals, forebay, and penstock, makes their initial investment much lower than commonly used horizontal Banki turbine of the same capacity. The possibility to install in the existing canals for Ultra Low Head applications is the additional motivating factor for this research. The system studied includes two Banki runners without internal shafts mounted vertically side by side surrounded by nozzle and diffuser structures. In the first scenario, Nozzle and then the Nozzle-diffuser augmented structures were separately studied to enhance the output of the runner for ultra-low head application, and the effects of each on the speed, pressure, and power output were analyzed. For the case of commonly used Banki, without nozzle and diffuser augmentation the speed for Ultra Low Head was minimum and determined to be 344 rpm, which is far below the recommended value of 800 rpm for safe operation at a flow rate of 1 m^3/s. In view of this, in the present study the enhanced speed on account of improvement was found to be 850 rpm and 1025 rpm for the design without and with diffuser assemblies respectively. Besides, the performance is seen to be improved by 7.6% with the diffuser as compared with the one without diffuser assembly. Detailed simulation results are presented and discussed: 3D ANSYS-FLUENT optimization result provided optimum number of blades for each runner to be 19 and with the optimum throat width in both cases as 202 mm. On account of the lack of any results reported so far for this innovative geometry, validation of the simulated results was carried out with reported results for the dual horizontal axis Banki turbines with good agreement.

Multiple Performance Optimization of a Single Stage Centrifugal Pump using an Intelligent System Approach

This study aims the use of an intelligent system to analyze and enhance the performance of a single stage centrifugal pump (SSCP) with respect to the blade number of impeller, which is crucial for the centrifugal pump design. In general, maximizing the efficiency (h) is the most common performance cost. Moreover, maximizing the pump head (H) and minimizing the power (P) are the other important criteria that should be considered for the optimal blade number. These goals are not simultaneously considered usually in the studies on this topic. The motivation of this study is to expand the system management perspective by evaluating the performance of the system with these multiple criteria. The centrifugal pump design is a typical Multi-Objective Optimization (MOO) problem. The MOO approach consists of five decision variables and three objective functions with different blade numbers for impellers. To determine the optimal solution of this MOO problem, the experimental data is initially expanded using a learning by examples methods based on an intelligent network model training. Then, extended data is used for calculating performance measures at each input-output pairs. In order to evaluate the results of the proposed approach on a real-time system, B50-200/100 type model pump with the speed of 2950 rpm and an outlet angle of 22.150 was tested at State Sugar Machine Plant, Eskisehir (Turkey). Since the main purpose is to determine the optimal blade number, different blade numbers has been used while other geometric parameters were kept constant. To determine the optimal solution, experimental data has used to train a selected soft computing model known as FWNN model. This model has advanced to express the relationship between the inlet and outlet values of the centrifugal pump. FWNN model achieves the general characteristics of the performance measure. The analysis with the use of FWNN model shows that, the optimum number of blades by considering the specified performance parameters for the centrifugal pump design is seven. Comparing with pump impeller with number of blades 5, 6, 8 and 9 increases in efficiency rates are 0.4%, 2.57%, 6.4% and 7.2%, respectively. The FWNN model over the performance analysis algorithm completes the missing data if exists and indicates the best performance solution as given.

An analytical method for determining the optimum number of blades of the compound impeller in a low specific speed centrifugal pump

Reasonable methods for determining the optimum number of blades in a low specific speed centrifugal pump with closed-type impeller with splitters, i.e. compound impeller have been rather rare in the literature so far. In the article, a new analytical method was put forward to determine such an optimum number of blades by including the effect of turbulent boundary layer over impeller blades. Three conventional impellers with different numbers of full-length blades and two compound impellers with different numbers of splitters were designed and manufactured. The corresponding performance tests were then conducted. Results showed that the optimum numbers of blades exist for two kinds of impeller in terms of head at design point, pump efficiencies at design point and best efficiency point, and slope of head-flow rate curve at shut-off point. The estimated optimum numbers of blades are in good agreement with the numbers based on the experiments. The conventional impellers with full-length blades are more prone to the hump phenomenon than the compound impellers at the optimum numbers of blades. For the compound impellers, however, the hump effect is negligible at the optimum number of blades, and their head and efficiency are higher than those for the impellers with full-length blades. The method is applicable to compound impeller design in low specific speed centrifugal pumps.

Optimum Design of the Dental Air-Turbine Handpiece System Using the Design of Experiment Method

An air-turbine and associated air supply tube was optimized as a dental air-turbine handpiece system. The system consists of an air-turbine with an impeller and a housing, and an air supply tube which supplies compressed-air to the air-turbine. The flow characteristics of the dental air-turbine handpiece system were investigated using ANSYS CFX. The study aimed to find the significant design parameters, and optimize them in terms of the maximum torque. The number of blades, the blade angle of the impeller and the gap between the impeller and the housing were chosen as the three major design parameters. The design of experiment technique was used to optimize two dental air-turbine handpiece systems: Type 1 was an air turbine alone and Type 2 was the air-turbine with an air supply tube. The optimization results showed that the gap between the impeller and the housing was not a significant parameter for Type 1. The maximum torque was lower for Type 2 than for Type 1. The optimized optimum blade number was the same for both types, but the blade angle and the gap differed between the two types. The blade angle and blade number were significant for Type 1, and all three design parameters were significant for Type 2. The performance improvement was greater for Type 2 than for Type 1. The performance of both optimized handpiece systems was reviewed in terms of the experimental measurements of noise level, rotational speed, and withdrawal force.

A novel approach to determine splitter vane length for an extremely high hub/tip ratio mixed-flow compressor impeller

This paper presents an approach to determine splitter vane length in radial compressor impellers based on a modified 1D performance prediction model, which considers the effects of splitter vane length and blade number on impeller internal losses. The splitter vane length corresponding to optimum blade number is investigated to achieve the maximum efficiency of a mixed-flow compressor impeller with an extremely high hub/tip ratio. An empirical formula for calculating splitter vane length is proposed. CFD results show that blade number and splitter vane length have a complex coupling interaction which makes it inappropriate to be described by equivalent solidity or effective blade number. 1D results and CFD verification indicate that optimum full-length blade number is 42 and corresponding splitter vane length is 20% of full-length blade length at design flow rate. The impeller peak efficiency mainly depends on minimum loss superposition of blade loading, skin friction and tip clearance. With the increase of splitter vane length and blade number, blade loading loss and clearance loss decline while skin friction loss increases.

Design for the turbine of solar chimney power plant system with vertical collector

Based on the design theory of the wind turbine, a turbine applied to solar chimney power plant with a vertical collector is designed, and the performance of the wind turbine is conducted by wind tunnel test. The results point out that the experimental performance is consistent with the designed performance. Then the number of blades and tip speed ratio are conducted, as well as we obtained the optimum blade number and tip speed ratio of turbine for the system.

Experimental study on performance assessment of Savonius rotor type wave energy converter in an experimental wave flume

The power generation of regular water waves from a horizontal-axis single Savonius rotor is experimentally investigated in an experimental wave flume in the context of the performance assessment of the rotor in intermediate-to-shallow water depths for different parametric conditions. A number of prototypes with multiple blades of 3–5 with the same diameter and blade curvature angle are fabricated in-house and tested to measure both the long-term average torque and power generated at different submergence levels, wave heights and wave periods. The experiments are performed in the wave-current flume equipped with a piston-type wave maker with an active wave absorption capability. The energy performance of the rotor is comparatively assessed for each experimental test case based on quantitative comparison of obtained wave-to-mechanical energy conversion efficiency (ECE) to suggest a possible optimum blade number, positioning and wave physical conditions for the investigated range of wave flow characteristics. It is found that higher ECE values can be achieved at higher wave heights and blade numbers for the lower wave periods when the rotor is placed at the water surface and/or just below the surface. This study provides a proper guideline for performance analysis of such device(s) for further studies.

NUMERICAL STUDY ON THE EFFECTS OF NUMBER OF BLADES ON THE PERFORMANCE OF TORQUE CONVERTERS

Number of blades of torque converter elements plays an important role in the design and performance of torque converters. In this paper, effects of the number of pump and turbine blades on the performance of torque converters are investigated numerically at different speed ratios, using a commercial software, ANSYS-CFX. Two torque converters, with the same outer diameter of 245 mm, were studied. Number of blades of the first torque converter is (32, 36 and 17) and for the second torque converter is (41, 37 and 17) for the pump, turbine and stator respectively. Blade shape and angles for the torque converter elements are the same. Numerical simulation results were compared and verified with the available literature and experimental results. A satisfactory agreement is presented between numerical and experimental results. Results showed that increasing the number of the blades of both of the pump and the turbine caused an increase of both of pump and turbine torque while the stall torque ratio is decreased and the coupling point occurred at lower speed ratio. Also, increasing the number of blades caused the maximum efficiency to be decreased. This may be explained by the change of slip factor of different number of blades as well as the effect of friction on shock losses. The study showed that there is an optimum number of blades required to improve the performance of torque converter.

발전용 소형가스터빈의 축류터빈 공력설계

본 논문은 두산중공업㈜에서 개발 중인 소형 가스터빈의 축류 터빈 설계 과정을 기술하였다. 축류 터빈의 설계 과정은 크게 유로설계, 익형설계, 3D 성능 계산의 세 단계로 구성되며. 최적의 유로를 설계하기 위해 자오면의 형상, 평균 반경, 블레이드간 간격, 유로 형상각 등 여러 형상 변수에 대해 통과유동계산 및 손실계산을 수행한다. 익형 설계는 유로 설계시 스팬 방향으로 계산된 입출구 유동각을 기준으로 실험상관식을 적용하여 최적의 블레이드 개수를 결정한 후 2D 익형 단면을 설계하며 2D NS 계산을 통해 캐스케이드 유동구조를 검토하여 설계한 단면의 설계적정성을 평가한다. 설계된 2D 익형 단면을 스팬 방향으로 적층하여 3D 익형을 생성하고, 다단 Euler 계산, 단익렬, 다단 NS 계산을 수행하여 3D 유동 특성을 고찰한다.

Optimization techniques for designing an inward flow radial turbine rotor

The choice of the principal dimensions of a turbine rotor for a given set of inlet design specifications can be found by solving aerodynamic equations. An analytical method is indeed difficult and can be very time consuming, especially if the complete procedure has to be repeated for different cases. In view of this, numerical optimization techniques can be a useful tool to problems involving a large number of variables. However, turbines commonly operate at high temperature and at high speeds, therefore the design process is an interactive one between the aerodynamic requirements and the mechanical, thermal limitations. This paper describes the complete design work of a turbine rotor based on using a nonlinear optimization technique to calculate the optimum principal dimensions of the rotor including optimum number of blades. Also, a prescribed mean stream velocity approach is used to determine the optimum axial length and the flow passage. For mechanical consideration, structure and thermal stresses and modal (vibration) analyses were carried out to satisfy design requirements.

VARYING THE NUMBER OF BLADES ON THE ROLLER-GIN ROTARY KNIFE

An experiment was run to determine the optimum number of blades and frequency of the rotary knife on a rollergin stand. The knife designs tested included a 2-, 3-, 4-, and 6-blade rotary knife. Each knife design was run at a knifefrequency of 14.5, 18.2, 24.2, 36.3, and 72.8 stroke/s. The criteria used for determining the optimum knife design includedany damage to the seed or fiber, and differences in carryover and ginning rate. With respect to cottonseed properties, foreignmatter content in the seed decreased as knife frequency increased, and seed linters content was highest at the highest knifefrequency. With respect to fiber properties, foreign matter content in the lint decreased as the number of blades increased,and increased as the knife frequency increased. Fiber properties such as length, strength, uniformity, short fiber, and nepcontent were not compromised by either rotary knife design or frequency. Ginning rate was highest at a knife frequency of36.3 stroke/s. The recommended running frequency for the rotary knife is 36 stroke/s, and ginning with a 3-, 4-, or 6-bladedesign is acceptable.

THEORETICAL PERFORMANCE OF WIND WHEEL TURBINES

A wind wheel turbine designed for low wind speed applications has been analytically investigated. The turbine is simple constructed from a bladed-assembly rotor directly exposed to the free wind on the upper half and exposd to the wind through a multiple ducting system on the lower half. A theoretical analysis using an engineering model based on the impulse momentum theory is described for a range of blade numbers. The computed results of the torque and power coefficients for two-, three-. and four-blade-wheels are presented. The optimum number of blades was found to be three, using the maximum power coefficient as the performance criterion. The computed values of the power coefficients are found to be higher than those associated with other wind machines for tip speed ratios up to a value of unity. The results also show that the 3-blade-wheel, with accelerating flow through the ducting system, has increased the power coefficient by 3.5 times as much as the ideal propeller type windmill. Torque coefficients which may have potential use in some domestic applications are also described. A starting torque coefficient as high as 6.0, for example, is computed for a 2-blade-wheel.

Parametric Study on Performance of Cross-Flow Turbine

In the present experimental study, the effect of blade number, nozzle entry arc, and head on the performance characteristics of a cross-flow turbine have been investigated. It has been observed that the efficiency of the turbine increases with increase in blade number, nozzle entry arc, and head. The present investigation has also shown that there is an optimum number of blades for a given nozzle entry arc beyond which the performance of the cross-flow turbine deteriorates. It has also been shown that cross-flow turbines at higher heads do not behave as pure impulse turbines.

Refinement of Cross‐Flow Turbine Design Parameters

This paper discusses experiments that were conducted to refine some of the key cross‐flow turbine runner parameters for better performance. The parameters studied were identified by previous studies as key design parameters. The research included narrowing the range of the number of blades, the determination of the impact of the first‐stage exit angle, and the effect of flow stream spreading on the performance of the cross‐flow turbine. The results indicate an optimum number of blades that would produce maximum efficiency of the turbine, and a clear trend of the effect of the first‐stage exit angle and flow stream spreading on the efficiency. For the best nozzle‐runner combination, the maximum efficiency closest to the discharge averaged maximum efficiency is determined to be 92%, with an uncertainty of ±2.4%. This result is an improvement over the reported maximum efficiency of any cross‐flow turbine.

Experimental Study of Cross‐Flow Turbine

The performance of the cross‐flow turbine, CFT, also known as the Banki turbine, was studied experimentally by varying the number of blades, the runner diameter, and the nozzle entry arc under flow/head variations. The results, as presented in this paper, show that the maximum efficiency of the CFT at any flow/head combination increases as the nozzle entry arc increases or the aspect ratio of the runner decreases. Equations have been suggested to obtain the optimum number of blades for maximum efficiency of the turbine and to find the specific speed of the CFT as a function of unit discharge and nozzle entry arc.

The Recovery of Rotational Energy in Propeller Slipstream by Fins installed after Propellers

At first, the fundamental equation of the energy distribution in the flow field around a propeller and fins are derived. Next, the theoretical and experimental studies on the recovery of the rotational energy in the propeller slipstream show the following results : a) In the propeller slipstream between 0.125 D and 2.0 D behind propellers (D ; propeller diameter), the dissipation of the rotational energy is very weak and the rotational flow is same at every cross sections. b) The fins after propellers decrease the rotational energy in the propeller slipstream and convert the most of the energy into the work done by fin thrust.c) With increasing the number of blades, fin improve the rotational energy recovery. The increase of fin drag, however, makes the optimum blade number finite. It mainly depend on propeller loading conditions and fin chord length.d) The rudder with fins recovers the rotational energy more efficiently than without fins.