System Matched 3D Radial Impeller Design With Variable Inlet Angle Distributions

2012 ◽  
Author(s):  
Matthias Semel ◽  
Henrik Smith ◽  
Philipp Epple ◽  
Oliver Litfin ◽  
Antonio Delgado ◽  
...  
Keyword(s):  
Rotational Speed ◽  
High Efficiency ◽  
Low Flow ◽  
Hydraulic Efficiency ◽  
Linear Variation ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Flow Rates ◽  
Lower Flow ◽  
Inlet Angle

In vacuum cleaners radial impellers with high rotational speed are very often used. A high rotational speed is connected with a best efficiency point of the radial impeller at a high flow rate. This is contrary to the working point of the whole system. Thus there is need for a radial impeller designs having a high efficiency at low flow rates under the restriction of a high rotational speed. One important parameter connected to the hydraulic efficiency characteristics of the radial impeller is the blade inflow angle β1. In order to shift the best efficiency point towards lower flow rates radial impellers with double curved blades and a linear β1 distribution were designed and CFD simulations were done in order to investigate the effect of this approach. A linear variation of the inflow angle β1 enables the designer to shift the efficiency characteristics of the impeller towards lower flow rates with a gain in hydraulic efficiency and pressure increase.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

Deterministic Decomposition of the Unsteady Flow in a Unidirectional Axial Turbine for OWC Plant

2018 ◽  
Author(s):  
Nuria Alvarez Bertrand ◽  
Jesús Manuel Fernández Oro ◽  
Bruno Pereiras García ◽  
Manuel García Díaz
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Low Flow ◽  
Oscillating Water Column ◽  
Turbine Stage ◽  
Flow Rates ◽  
Aerodynamic Efficiency ◽  
Axial Turbine ◽  
Deterministic Framework ◽  
Energy Plants

The “twin-turbine” configuration has recently emerged as a feasible possibility for unidirectional turbines to be introduced in Oscillating Water Column wave energy plants without requiring auxiliary rectifying systems. Previous investigations by the authors have been focused on the development of a numerical CFD model to analyze the performance of a unidirectional axial turbine for twin turbine configuration in an OWC system. In this paper, all these numerical databases are further post-processed using a deterministic framework to give more insight about the flow patterns within the turbine. The final objective is the analysis of the unsteady features of the flow and the stator-rotor interactions using a deterministic decomposition. The present study reveals that levels of deterministic unsteadiness in the inter-row region are moderate, being more intense as the flow rate is decreased. Turbulence intensities are also observed to be clearly prominent in case of lower flow rates. Although these findings appear to be contradictory with the high-efficiency low flow rates of the turbine, the major levels of stator-rotor unsteadiness at higher flow rates (shown by the deterministic decomposition) justify the serious penalty in the aerodynamic efficiency as the turbine flow rate is increased. Finally, some advices with respect the design of the vane row in the turbine stage are given to control the generation of turbulence and stator-rotor interaction.

Speed Matching of the Second Rotor in a Counter-Rotating Fan Under Off-Design Conditions

2017 ◽  
Author(s):  
Zijian Ai ◽  
Guoliang Qin ◽  
Xuefei Chen ◽  
Jingxiang Lin ◽  
Wenqiang He
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
High Efficiency ◽  
Pressure Rise ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Fan Performance ◽  
Power Characteristics ◽  
Equal Power

A method for speed matching of the second rotor (R2) with equal power for two rotors was proposed to improve the performance of the counter-rotating fan under off-design conditions. In this method, the speed of R2 is adjusted until the power of R2 is equal to the power of the first rotor (R1). The fan performance during constant speed operation and during R2 speed matching operation is presented and discussed using theoretical analysis, numerical simulation, and experimental research. The results show that R2 speed matching improves the power and efficiency characteristics of R2. Thus, the pressure rise and power characteristics of the fan were improved. The load of R2 under low flow rates condition was decreased, and the pressure rise and efficiency of R2 under high flow rates condition were increased. The blocking condition margin increased from 37.2% to 48.0%, and the high-efficiency working range of the fan increased from 33.2% to 37.9%.

scholarly journals Flow Characteristics in the Volute and Tongue Region of a Centrifugal Pump

1984 ◽  
Author(s):  
R. B. Brownell ◽  
R. D. Flack
Keyword(s):  
Rotational Speed ◽  
Separation Zone ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Pressure Profiles ◽  
Instantaneous Position ◽  
Centrifugal Process

A centrifugal process pump was tested at two rotational speeds and five flow rates. Nine piezometer taps around the volute were used to measure time averaged pressure profiles and streak photography was used to visualize the flow patterns near the volute tongue. Flow patterns for four different instantaneous impeller orientations (blade positions) were studied. Nondimensionalized results were independent of rotational speed. At 100% capacity the volute pressures were uniform within 15%. At off-design condition, however, the pressure near the tongue varied by as much as 28% from the average. At 100% capacity the streamlines were smooth and well behaved. At low flow rates the tongue stagnation point moved between the impeller and tongue and a separation zone appeared in the discharge. The instantaneous position of the impeller was seen to affect the streamlines primarily near the impeller, although at high flow rates the separation zone was also seen to depend on the impeller position.

Experimental and Numerical Study on Hydraulic Performances of a Turbopump With and Without an Inducer

2018 ◽  
Author(s):  
Yanxia Fu ◽  
Meng Fan ◽  
Giovanni Pace ◽  
Dario Valentini ◽  
Angelo Pasini ◽  
...  
Keyword(s):  
Total Pressure ◽  
Pressure Rise ◽  
Hydraulic Performance ◽  
Numerical Results ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Lower Flow ◽  
Inlet Duct

The hydraulic performance of a centrifugal turbopump with and without a 3-bladed axial inducer has been studied both experimentally and numerically. A 3D numerical model has been used to simulate the flow through from the inlet to the outlet ducts of the turbopump with and without an inducer using the ANSYS CFX code. The sensitivity of the numerical results has been analyzed with reference to the adopted turbulent flow models, to the length of the input and output ducts included in the simulations, to the reference positions used for the evaluation of the total pressure rise and to the temperature of the operating fluid. The measured and predicted hydraulic performances of the turbopump with and without the inducer have been compared under different operating conditions. As expected, the predicted hydraulic performance of the turbopump is significantly influenced by the lengths of the inlet and outlet ducts, the turbulence models and, at low flow rates, the reference positions of the total pressure rise measurements. The pressure rise coefficients obtained from the simulations using an inlet duct with length of 3 rTi and 10 rTi were significantly lower than the experimental results, while at low flow rates those referring to the inlet duct with length greater than 10 rTi were significantly higher than those obtained for the shorter inlet duct. With reference to the effect of the pressure measurement locations, the difference between the numerical results of the pressure rise coefficient and the experimental values was much higher when the data were obtained at the locations where the transducers was mounted in the experimental tests at lower flow rates. Moreover, the hydraulic performance of the turbopump at lower flow rates can be significantly influenced by the use of the upstream inducer, with a pressure drop of 20% in particular at 60% of the design flow rate.

Grinding Combination of Electrochemical Smoothing On SKH 51 Surface

2008 ◽  
Vol 389-390 ◽  
pp. 410-416
Author(s):  
Pai Shan Pa
Keyword(s):  
Current Density ◽  
Rotational Speed ◽  
High Efficiency ◽  
Great Contribution ◽  
High Rotational Speed ◽  
Workpiece Surface ◽  
Design Change ◽  
Full Form ◽  
Electrochemical Smoothing ◽  
Thin Electrode

A new finish mode combination of grinding and electrochemical smoothing executes a finish processes on SKH 51 surface is investigated. In the experiment, a high rotational speed of finish tool produces a better finish. A thin electrode associated with higher current density provides a larger discharge space for a better finish. The design change from a full form finish-tool to a partial finish-tool leads more discharge space, which creates better finishes than full form tool. It is a great contribution that the synchronous finish processes has a high efficiency than the electrochemical smoothing to make the workpiece surface smooth and bright.

Structural Analysis of Small Scale Radial Turbine for Solar Powered Brayton Cycle Application

2018 ◽  
Author(s):  
Ahmed Mahmood Daabo ◽  
Saad Mahmoud ◽  
Raya K. Al-Dadah
Keyword(s):  
Rotational Speed ◽  
High Efficiency ◽  
Fluid Dynamic ◽  
Small Scale ◽  
Brayton Cycle ◽  
High Rotational Speed ◽  
Radial Turbine ◽  
Solar Powered ◽  
Maximum Increment ◽  
Cfd Optimization

Developing small scale turbines pauses challenges in terms of increased stresses due to high rotational speed leading to increase in component thicknesses and turbine overall weight. Therefore this study assesses both; the structural and aerodynamic performance of a Small Scale Radial Turbine SSRT by integrating finite-element methods FEM and Computational Fluid Dynamic CFD. Using Vista preliminary design model in ANSYS and detailed 3D CFD optimization, SSRT with 1–5 kW power for solar powered Brayton cycle was developed with high efficiency of 89.2%. Then both; the turbine’s hub and blades were structurally analysed under various loading conditions to investigate the effect of various rotational speeds and blade shapes on the stress distribution and deformation of the blades. The results of the current study showed that a maximum increment of 65% stress and 57% deformation was noticed when reaching the maximum studied rotational speed at inlet air temperature of 450 K.

scholarly journals Effects of Soil Conservation Practices on Sediment Yield from Forest Road Ditches in Northern Iran

2020 ◽  
Vol 41 (2) ◽  
pp. 299-308
Author(s):  
Rasoul Khandouzi ◽  
Aidin Parsakhoo ◽  
Vahedberdi Sheikh ◽  
Aliakbar Mohamadali Pourmalekshah
Keyword(s):  
Flow Rate ◽  
Sediment Yield ◽  
Festuca Arundinacea ◽  
High Efficiency ◽  
Sediment Concentration ◽  
Low Flow ◽  
Road Maintenance ◽  
Northern Iran ◽  
Flow Rates ◽  
Forest Road

The fine-textured soil in forest road ditches is very susceptible to water erosion especially in rainy seasons in Hyrcanian forest. This study examined the yield of ditch segment-scale sediment after releasing two flow rates of 5 l s-1 and 10 l s-1 in segments treated by riprap (RR), grass cover by Festuca arundinacea L. (GC), compacted cotton geotextile (CG) and wooden wattle by local slash (WW). Sediment sampling from the runoff was carried out at the end of each segment every minute. Runoff flow velocity in different treatments was measured using an electromagnetic flow meter. Sediment concentration and runoff velocity in treatments of RR, GC, CG, WW was significantly lower than that of the control plot (Ctl). Increasing flow rate from 5 l s-1 to 10 l s-1 caused no significant change in sediment concentration (except for Ctl and RR) and runoff velocity (except for Ctl and CG), which means that some water might have penetrated into treated soil by RR, GC and WW and this is not acceptable in forest road maintenance practices. Sediment yield from RR (0.36 g l-1) and Ctl (0.50 g l-1) under the flow rate of 10 l s-1 was significantly higher than that of 5 l s-1 with values of 0.21 g l-1 and 0.38 g l-1, respectively. Minimum amount of sediment concentration was observed for CG (0.20 g l-1) with compacted ditch bed. Moreover, runoff velocity in CG and Ctl under the flow rate of 10 l s-1 was significantly higher than that of 5 l s-1. For a forest road with dimension 30×50 cm, slope of 5%, and clay soil with porosity of 57%, treatments of compacted CG can be used in ditch with low flow rates (5 l s-1) and high flow rate (10 l s-1) because of their high efficiency in reducing sediment yield.

Detailed CFD Analysis of the Steady Flow in a Wells Turbine Under Incipient and Deep Stall Conditions

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
M. Torresi ◽  
S. M. Camporeale ◽  
G. Pascazio
Keyword(s):  
High Efficiency ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Main Stream ◽  
Tip Leakage Flow ◽  
Complex Flow ◽  
Wells Turbine ◽  
High Rotational Speed ◽  
Flow Rates ◽  
Low Efficiency

This paper presents the results of the numerical simulations carried out to evaluate the performance of a high solidity Wells turbine designed for an oscillating water column wave energy conversion device. The Wells turbine has several favorable features (e.g., simplicity and high rotational speed) but is characterized by a relatively narrow operating range with high efficiency. The aim of this work is to investigate the flow-field through the turbine blades in order to offer a description of the complex flow mechanism that originates separation and, consequently, low efficiency at high flow-rates. Simulations have been performed by solving the Reynolds-averaged Navier–Stokes equations together with three turbulence models, namely, the Spalart–Allmaras, k-ω, and Reynolds-stress models. The capability of the three models to provide an accurate prediction of the complex flow through the Wells turbine has been assessed in two ways: the comparison of the computed results with the available experimental data and the analysis of the flow by means of the anisotropy invariant maps. Then, a detailed description of the flow at different flow-rates is provided, focusing on the interaction of the tip-leakage flow with the main stream and enlightening its role on the turbine performance.

scholarly journals Numerical and experimental characterization of splitter blade impact on pump as turbine performance

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199324
Author(s):  
Daniel Adu ◽  
Jianguo Du ◽  
Ransford O Darko ◽  
Eric Ofosu Antwi ◽  
Muhammad Aamir Shafique Khan
Keyword(s):  
Rotational Speed ◽  
Simulated Data ◽  
Maximum Deviation ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Turbine Performance ◽  
Hydropower Dams ◽  
The Impact ◽  
Good Agreement

Several rivers and streams are available in Africa and Asian regions with great potentials not applicable for constructing large hydropower dams but feasible for small and mini hydro generation. This study strive for investigating the impact of splitter blade on pump as turbine performance considering different speed and flow rates. Two specific centrifugal pump models one with six blades without splitter and another with four blades and four splitters were used for the study. The inlet diameter and outlet diameters of both impellers were 104 mm/116 mm, and 160 mm respectively at a designed flow rate Q = 12.5 m3/h, head H = 16 m, rotational speed n = 1450 rpm and efficiency of 56%, outlet impeller width of 0.006 m, a blade outlet angle of 30° was used for the study. CFD simulations were conducted with the use of k-ε turbulence model. The influence of splitter blade position on the performance of pump as turbine in the selected specific pumps with and without splitter blades has been investigated both experimentally and numerically at three different flow rates and rotational speed. The simulated data were in good agreement with the experimental results, the maximum deviation error between the CFD and test for each model are 5.6%, 2.6%, for the head and efficiency; 7.5% and 3.6% at different flow conditions.

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