Flow in a Single Stage Centrifugal Fan With Vaneless Diffuser and Peripheral Louver Outlets

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Hongmin Li

This paper presents an analysis on the air flows in a single stage centrifugal fan with a vaneless diffuser and peripheral louver outlets. The performance data of the fan are obtained experimentally. A numerical fluid flow model is developed. The agreements between the numerical and experimental results are reasonably good. The performances of the fan under various working conditions are explained by the flow structures and pressure distributions. Flow energy analysis shows that the major energy losses in the fan are the impeller loss, the diffuser loss, and the gap leakage loss. Suggestions on the design and application of fans with such architecture are given.

2000 ◽  
Author(s):  
Fahua Gu ◽  
Abraham Engeda ◽  
Mike Cave ◽  
Jean-Luc Di Liberti

Abstract A numerical simulation is performed on a single stage centrifugal compressor using the commercially available CFD software, CFX-TASCflow. The steady flow is obtained by circumferentially averaging the exit fluxes of the impeller. Three runs are made at design condition and off-design conditions. The predicted performance is in agreement with experimental data. The flow details inside the stationary components are investigated, resulting in a flow model describing the volute/diffuser interaction at design and off-design conditions. The recirculation and twin vortex structure are found to explain the volute loss increase at lower and higher mass flows, respectively.


2001 ◽  
Author(s):  
Tarek Mekhail ◽  
Zhang Li ◽  
Du Zhaohui ◽  
Willem Jansen ◽  
Chen Hanping

Abstract The PIV (Particle Image Velocimetry) technology is a brand-new technique of measuring velocity. It started in the 1980’s with the development of high-speed photography and the image processing technique of computers. This article deals with PIV applied to the study of unsteady impeller-vaneless diffuser interaction in centrifugal fen. Experiments were carried out at The Turbomachinery Laboratory of Shanghai Jiaotong University. The test rig consists of a centrifugal, shrouded impeller, diffuser and volute casing all made of plexiglass. A series of performance measurements were carried out at different speeds and different vaneless diffuser widths. PIV measurements were applied to measure the unsteady flow at the exit part of the impeller and the inlet part of the diffuser for the case of the same width vaneless diffuser. The absolute flow field is measured at medium flow rate and at maximum flow rate. It is informative to capture the whole flow field at the same instant of time, and it might be more revealing to observe the unstable flow in real time.


2018 ◽  
Vol 46 (5) ◽  
pp. 17-25
Author(s):  
Timothy Galpin

Purpose Mergers and acquisitions (M&As) have become the preferred growth strategy for many executives. However, simply “doing deals” is not enough to create a competitive advantage for their companies. Only focusing on M&A as a financial transaction is too narrow of an approach, which is easily duplicated across firms. Using Woodward, Inc. as a case example, this article shows how using an actionable, end-to-end process model, and embedding integrated capabilities within the organization, across the entire process, managers can make M&A a core competence to provide a valuable, rare, and inimitable advantage for their firms. Design/methodology/approach A mixed-methods approach, combining action research with a narrative synthesis of empirical and practice literature was used to develop a comprehensive M&A process model - the Deal Flow Model - consisting of ten stages across three phases. The resource-based view, core competencies, and the VRIO framework provide a theoretical foundation for the model. An application of the Deal Flow Model using Woodward Inc. as a case example is also presented. Findings Only focusing on M&A as a financial transaction is too narrow of an approach, which is easily duplicated across firms. Instead, using an actionable, end-to-end process model, and embedding integrated capabilities within the organization across the entire M&A process provides a valuable, rare, and inimitable advantage for firms. Research limitations/implications Researchers will find the Deal Flow Model useful as a structure to examine the M&A process as a whole or to frame single-stage, single-discipline research in the broader context of the overall M&A process. Practical implications A practice-oriented Deal Flow Model, providing a cross-disciplinary, end-to-end view of the M&A process is presented. The model is designed to be actionable by managers, who can apply the process to build the M&A competence of their organization. Originality/value The Deal Flow Model is unique as it is designed to be actionable by managers, who can apply the process to build the M&A competence of their organization. Likewise, researchers will find the model useful as a structure to examine the M&A process as a whole or to frame single-stage, single-discipline research in the broader context of the overall M&A process.


Author(s):  
Horst Saathoff ◽  
Udo Stark

The paper describes an investigation of the overtip end-wall flow in a single–stage axial–flow low–speed compressor utilizing an oil flow technique and a periodic multisampling pressure measurement technique. Representative oil flow pictures and ensemble averaged casingwall pressure distributions with standard deviations — supplemented by selected endwall oil flow pictures from a corresponding 2D compressor cascade — are shown and carefully analysed. The results enable the key features of the overtip endwall flow to be identified and changes with flow rate — or inlet angle — to be determined.


Energy ◽  
2018 ◽  
Vol 147 ◽  
pp. 1299-1310 ◽  
Author(s):  
José Ramón Serrano ◽  
Roberto Navarro ◽  
Luis Miguel García-Cuevas ◽  
Lukas Benjamin Inhestern

Author(s):  
Robin R. Jones ◽  
Oliver J. Pountney ◽  
Bjorn L. Cleton ◽  
Liam E. Wood ◽  
B. Deneys J. Schreiner ◽  
...  

Abstract In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimise the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream-egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile and EWC on the rotor endwall. This paper presents the design of, and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress-mainstream flow interactions. To the authors’ knowledge this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry and planar laser induced fluorescence are also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seals geometries. The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes at three different spanwise locations; pitchwise static pressure distributions downstream of the nozzle guide vane at four axial locations on the stator platform.


2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Xu Yang ◽  
Yao Qin ◽  
Zongchang Qu

The working performance of the synchronal rotary multiphase pump (SRMP), alike other types of positive-displacement multiphase pumps, is strongly affected by leakage loss. In this paper, the leakage loss in the SRMP with a full range of inlet gas volume fractions (GVFs) was theoretically and experimentally investigated. The leakage flows in the SRMP were modeled as the one-dimensional gas–liquid flows through narrow gaps. Two types of leakage flow models, homogeneous leakage flow model (HLFM) and separated leakage flow model (SLFM), were developed. The experimental work was conducted to measure the volumetric flow rate of the SRMP using the mixtures of air and N32 oil as working fluids under various inlet GVFs and differential pressures. Comparisons between the simulated and experimental pump flow rates showed that both the accuracies of the HLFM and SLFM related to the inlet GVF. In addition to the differential pressure, the leakage loss of the SRMP was affected by the inlet GVF. The leakage flow rate increased with the inlet GVF due to the changes in physical properties of the gas–liquid leakage flow. Parametric analysis showed that leakage loss in the SRMP can be effectively reduced by reducing the rotor radial clearance without much effect on its mechanical efficiency, whereas the optimum geometric parameters of the rotor and cylinder must be calculated by means of the optimization study with consideration of both the leakage loss and friction loss.


1995 ◽  
Vol 117 (1) ◽  
pp. 36-44 ◽  
Author(s):  
M. J. Braun ◽  
V. V. Kudriavtsev

This paper contains numerical experiments that model fluid flow through a staggered array of cylinders and represents a continuation of work previously performed by the authors (Braun et al., 1993; Kudriavstsev et al., 1993). The results shown here concentrate on the analysis of the physics of flow and pressure distribution in (i) one row of cylinders, and (ii) seven rows of cylinders. The test section is the same square channel described by Braun et al. (1993). The numerical experiments were run in transient mode at Reynolds numbers (Re = umaxd/v) ranging from 86 to 869. The primary purpose of this paper is to report qualitative results regarding the attached near-wall jet phenomenon and to discuss its flow mechanics. The authors compare various stages of the transient evolution of the flow structures for geometric configurations that contain one, and seven rows of pins respectively. The associated pressure distributions in the arrays of pins are also discussed.


Author(s):  
Chien-Chang Chen ◽  
Cheng-Hsiung Kuo

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.


Sign in / Sign up

Export Citation Format

Share Document