Experimental Investigation of the Blade Surface Pressure Distribution in an Axial Flow Fan for a Range of Flow Rates

2015 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Experimental Technique ◽  
Surface Pressure ◽  
Static Pressure ◽  
System Modeling ◽  
Axial Flow ◽  
Numerical Data ◽  
Blade Surface ◽  
Local Flow ◽  
Flow Rates ◽  
Additional Tool

Numerical modeling of the flow field in the vicinity of large axial flow fans finds application in various engineering investigations, whether for fan design purposes, fan induced flow fields or fan system modeling. These three-dimensional fan models generally require verification with experimental results to establish validity. For this purpose a comparison is generally made between the numerically and experimentally obtained fan performance characteristics (fan static pressure and static efficiency curves) to verify the model. Although this method provides a means to validate the numerical model on a global flow level, some uncertainty on the accuracy of this validated model on a local flow level (flow structures close to the fan blade) might still exist. In the present study an experimental technique is presented to measure blade surface static pressures that can be used to validate numerical fan models on a local flow level. These measurements are obtained for a specific fan by means of piezo-resistive pressure transducers mounted in a capsule on the fan axis and connected to pressure taps in specially manufactured fan blades. The transducers are also coupled to a telemetry system that samples the measured pressures and enables wireless communication between the fan and a laptop/PC. Blade surface pressure measurements are obtained for a series of volumetric flow rates through the fan and compared to the numerical data simulated using a RANS approach. A good comparison between the experimental and numerical blade surface static pressure data exists, with the largest discrepancies occurring near the hub as well as the leading and trailing edges of the blade. The reason for this discrepancy could be attributed, amongst others, to low y+ values (y+ < 30) on the blade surface in these regions, leading to errors in the calculation of the wall condition by the wall function. The experimental technique therefore provides CFD engineers with an additional tool for numerical fan model validation on a local flow level.

Blade Surface Pressure Measurements on a Low Pressure Rise Axial Flow Fan

2020 ◽  
Author(s):  
Johannes Rohwer ◽  
Sybrand J. van der Spuy ◽  
Theodor W. von Backström ◽  
Francois G. Louw
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Surface Pressure ◽  
Static Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Test Facility ◽  
Pressure Measurements ◽  
Blade Surface ◽  
Axial Flow Fan

Abstract Fan performance characteristic tests of axial flow fans provide information on the global flow field, based on stable inlet flow field distribution. More information is often required on the local flow distribution existing in the vicinity of the fan blades under installed conditions. A 1.542 m diameter scale model of an axial flow fan, termed the M-Fan is tested in an ISO 5801, type A, test facility. The M-fan was specifically designed for low-pressure, high flow rate application in air-cooled or hybrid condensers. The scaled version of the M-fan was designed to have a fan static pressure rise of 116.7 Pa at a flow rate of 14.2 m3/s. Two specially constructed M-Fan blades are manufactured to conduct blade surface pressure measurements on the blades. The fan blades are equipped with 2 mm diameter tubes that run down the length of the fan blades in order to convey the measured pressure. Piezo-resistive pressure transducers, located on the hub of the fan, measure the static pressure distribution on the blades and the data is transferred to a stationary computer using a wireless telemetry setup. The blade pressure measurement setup is re-commissioned from a previous research project and its performance is qualified by testing and comparing to experimental results obtained on the B2a-fan. Excellent correlation to previous results is obtained. The experimental M-fan results are compared against results from a periodic numerical CFD model of a fan blade modelled in an ISO 5801, Type A test facility configuration. The experimental tests and numerical model correlate well with each other. The experimental blade surface pressure measurements have a minimum Pearson correlation to the numerically determined values of 0.932 (maximum 0.971).

Validation of Surface Pressure Predictions for Nozzle Airfoil and Endwall Film Cooling Design Using Transonic Cascade Measurements

2013 ◽  
Author(s):  
Jason E. Dees ◽  
James A. Tallman ◽  
Michael A. Heminger ◽  
Daniel Wilde
Keyword(s):  
Surface Pressure ◽  
Film Cooling ◽  
Static Pressure ◽  
Experimental Studies ◽  
Tangential Direction ◽  
Maximum Deviation ◽  
Pressure Measurements ◽  
Local Flow ◽  
Cooling Design ◽  
Transonic Cascade

This study compares surface pressure measurements and predictions for a high pressure turbine first-stage nozzle vane. The surface pressure measurements were taken in a 3D annular cascade, consisting of four airfoils and five passages. The cascade was uncooled, axisymmetric at both inner and outer endwalls, and reproduced the design intent Reynolds and Mach numbers of the real engine component. Static pressure measurements were taken along the airfoil profile at 15, 50, and 85% span, with duplicate midspan measurements across the four airfoils for assessing the tangential periodicity of the flow. Static pressure measurements were also taken on the inner and outer endwall surfaces of the center airfoil passage, with 40 measurement points uniformly distributed over each endwall. Three methods of surface pressure prediction were compared with the data: (1) a 2D inviscid CFD solution of a single airfoil passage at fixed spanwise locations, (2) a 3D RANS CFD solution of a single airfoil passage, and (3) a 3D RANS CFD solution of the full five-passage cascade domain. Both of the single-passage solutions assumed flowfield periodicity in the tangential direction and compared favorably to the center passage airfoil data. This finding suggested that the cascade center passage was sufficiently representative of the full-annulus turbomachine environment and validated the cascade for further experimental studies. The adjacent airfoil pressure measurements quantified the passage-to-passage variation in the cascade flowfield, and the 3D full-cascade CFD compared favorably with the peripheral airfoil data. The full-cascade CFD also compared favorably with the data on both endwalls: with an average and maximum deviation of 0.5 and 2%, respectively. These findings provide confidence in the 3D CFD methods for use in determining local flow rates from cooling/leakage geometry, and serve as an important first step toward validating the methods for real-engine blockage effects like coolant and endwall contouring.

scholarly journals A Simple Method to Estimate Blade Surface Pressure in Axial-Flow Turbomachines and Its Application

1971 ◽  
Vol 14 (74) ◽  
pp. 791-799
Author(s):  
Taijiroo KASAI ◽  
Sigenori MATSUNAGA ◽  
Yukio KUNIKIYO ◽  
Haruo ISIBASI
Keyword(s):  
Surface Pressure ◽  
Axial Flow ◽  
Blade Surface ◽  
Simple Method

The Simulation of an Axial Flow Fan Performance Curve at Low Flow Rates

2011 ◽  
Author(s):  
S. J. van der Spuy ◽  
F. N. le Roux ◽  
T. W. von Backstro¨m ◽  
D. G. Kro¨ger
Keyword(s):  
Static Pressure ◽  
Axial Flow ◽  
Low Flow ◽  
Operating Point ◽  
Pressure Curve ◽  
Flow Rates ◽  
3 Dimensional ◽  
Air Cooled Condensers ◽  
Actuator Disc ◽  
Experimental Values

Simplified fan models are often used to simulate the effect of axial flow fans in large arrays of air-cooled condensers. The actuator disc method and its shortcomings are discussed and illustrated using computational fluid dynamics. A full 3-dimensional analysis of the fan is also performed at a single operating point to evaluate the flow conditions around the blade. This analysis confirms the results of the actuator disc method at the specific operating point. An adaptation of the actuator disc method, to improve its ability to model fan operation at low flow rates, is proposed. The effectiveness of the adaptation is evaluated by comparing the fan static pressure curve obtained from experimental results to the fan static pressure curve obtained from the simulations. The comparison shows that an analysis using the adapted actuator disc method produces results that correlate well with experimental values.

Blade Surface Pressure Measurements on a Low Pressure Rise Axial Flow Fan

2021 ◽  
Author(s):  
Johan Van Der Spuy ◽  
Theodor Von Backstrom ◽  
Johannes Rohwer ◽  
Francois Louw
Keyword(s):  
Surface Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Low Pressure ◽  
Pressure Measurements ◽  
Blade Surface ◽  
Axial Flow Fan

Design Optimization of Cryogenic Pump Inducer Considering Suction Performance and Cavitation Instability

2011 ◽  
Author(s):  
Hiroyoshi Watanabe ◽  
Hiroshi Tsukamoto
Keyword(s):  
Pressure Distribution ◽  
Design Optimization ◽  
Surface Pressure ◽  
Design Approach ◽  
Inverse Design ◽  
Blade Surface ◽  
Free Vortex ◽  
Surface Pressure Distribution ◽  
Cavitation Instability ◽  
Suction Performance

This paper presents the result of design optimization for three-bladed pump inducer using a three-dimensional (3-D) inverse design approach, Computational Fluid Dynamics (CFD) and DoE (Design of Experiments) taking suction performance and cavitation instability into consideration. The parameters to control streamwise blade loading distribution and spanwise work (free vortex or non-free vortex) for inducer were chosen as design optimization variables for the inverse design approach. Cavitating and non-cavitating performances for inducers designed using the design variables arranged in the DoE table were analyzed by steady CFD. Objective functions for non-cavitating operating conditions were the head and efficiency of inducers at a design flow (Qd), 80% Qd and 120% Qd. The volume of the inducer cavity region with a void ratio above 50% was selected as the objective function for inducer suction performance. In order to evaluate cavitation instability by steady CFD, the dispersion of the blade surface pressure distribution on each blade was selected as the evaluation parameter. This dispersion of the blade surface pressure distribution was caused by non-uniformity in the cavitation length that was developed on each inducer blade and increased when the cavitation number was reduced. The effective design parameters on suction performance and cavitation instability were confirmed by sensitivity analysis during the design optimization process. Inducers with specific characteristics (stable, unstable) designed using the effective parameters were evaluated through experiments.

Influence of Turbulent Flow Characteristics and Coherent Vortices on the Pressure Recovery of Annular Diffusers: Part A — Experimental Results

2015 ◽  
Author(s):  
Marcus Kuschel ◽  
Bastian Drechsel ◽  
David Kluß ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Static Pressure ◽  
Turbulent Transport ◽  
Axial Flow ◽  
Pressure Recovery ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Wide Range ◽  
Operating Points

Exhaust diffusers downstream of turbines are used to transform the kinetic energy of the flow into static pressure. The static pressure at the turbine outlet is thus decreased by the diffuser, which in turn increases the technical work as well as the efficiency of the turbine significantly. Consequently, diffuser designs aim to achieve high pressure recovery at a wide range of operating points. Current diffuser design is based on conservative design charts, developed for laminar, uniform, axial flow. However, several previous investigations have shown that the aerodynamic loading and the pressure recovery of diffusers can be increased significantly if the turbine outflow is taken into consideration. Although it is known that the turbine outflow can reduce boundary layer separations in the diffuser, less information is available regarding the physical mechanisms that are responsible for the stabilization of the diffuser flow. An analysis using the Lumley invariance charts shows that high pressure recovery is only achieved for those operating points in which the near-shroud turbulence structure is axi-symmetric with a major radial turbulent transport component. This turbulent transport originates mainly from the wake and the tip vortices of the upstream rotor. These structures energize the boundary layer and thus suppress separation. A logarithmic function is shown that correlates empirically the pressure recovery vs. the relevant Reynolds stresses. The present results suggest that an improved prediction of diffuser performance requires modeling approaches that account for the anisotropy of turbulence.

Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage

1994 ◽  
Vol 116 (2) ◽  
pp. 327-332 ◽  
Author(s):  
T. Green ◽  
A. B. Turner
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Three Dimensional ◽  
Computer Code ◽  
Rotor Blades ◽  
Rotor Speed ◽  
Turbine Stage ◽  
Flow Rates ◽  
Static Pressure Distribution ◽  
Axial Clearance

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

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