Analytical Theory of Three Dimensional Flow in Centrifugal Compressors

1981 ◽  
Vol 23 (4) ◽  
pp. 179-191 ◽  
Author(s):  
C. Bosman
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Surface Flow ◽  
Centrifugal Compressors ◽  
Three Dimensional Flow ◽  
Stream Tube ◽  
Stream Surface ◽  
Dimensional Flow ◽  
Passage Vortex ◽  
Turbomachine Blade

Inviscid, compressible flow along a rotating elemental stream-tube is taken as a model for flow through a turbomachine blade passage. For this model an analytic expression for the relative secondary vorticity of the flow is derived which permits the mean stream-surface twist about the tube axis to be evaluated. This twist implies a migration of the fluid particles from one tube corner to the contiguous tube corner, a flow feature suppressed by all existing stream-sheet flow calculations in turbomachine blade rows. The analysis is applied to a centrifugal compressor configuration where the effects on the secondary flow of hub/shroud geometry, blade shape, compressibility, and meridional diffusion are investigated. The stream-surface twist, not being primarily dependent upon the elemental nature of the stream-tube is taken as a measure of stream-surface twist and consequent surface flow migration in finite blade passages. The levels of twist obtained from the analysis are similar to those obtained in three dimensional flow calculations using primitive variables as illustrated by Bosman (1) (2)‡ and show that existing streamsheet and streamsheet stacking methods, all of which suppress the relative passage vortex are an inadequate model of the flow in centrifugal compressors. The analysis clearly shows that contrary to common assumption, centrifugal compressor impellers are capable of generating a passage vortex in the same direction as that of blade rotation.

Calculation of Complete Three-Dimensional Flow in a Centrifugal Rotor With Splitter Blades

1988 ◽  
Author(s):  
Liu Dian-Kui ◽  
Ji Le-Jian
Keyword(s):  
Mass Flow ◽  
Three Dimensional ◽  
Present Calculation ◽  
Flow Ratio ◽  
Three Dimensional Flow ◽  
Stream Surface ◽  
Dimensional Flow ◽  
Flow Capacity ◽  
The Given ◽  
Mass Flow Ratio

The flow within a centrifugal rotor has strong characteristics of three-dimensional effect. A procedure called “stream-surface coordinates iteration” for the calculation of complete three dimensional flow in turbo-machinery is first described. Splitter blade techniques have been used in many rotors, especially in centrifugal compressors and pumps with high flow capacity. The difficulty of the calculation of the flow field for this type of rotor lies on that the mass flow ratio between the two sub-channels is unknown for the given total flow capacity. In the second part of this paper, an assumption about how to determine this mass flow ratio and a procedure to calculate the complete three-dimensional flow are presented. Finally, some design criteria about the splitter blades are put forward. Experimental data from two centrifugal pump impellers equipped with different splitter blades are also given to demonstrate the availability of the present calculation method.

scholarly journals Experimental and Theoretical Study of the Swirling Flow in Centrifugal Compressor Volutes

1989 ◽  
Author(s):  
R. A. Van Den Braembussche ◽  
B. M. Hände
Keyword(s):  
Centrifugal Compressor ◽  
Theoretical Study ◽  
Swirling Flow ◽  
Three Dimensional ◽  
Simplified Model ◽  
Three Dimensional Flow ◽  
Dimensional Flow

Measurements of the three-dimensional flow in a simplified model of a centrifugal compressor volute at design and off-design operation are presented.

Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part I—Velocity and Pressure Fields

1993 ◽  
Vol 115 (3) ◽  
pp. 435-443 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Surface Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Compressor Cascade ◽  
Three Dimensional Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Dimensional Flow

Experimental results from a study of the three-dimensional flow in a linear compressor cascade with stationary endwall at design conditions are presented for tip clearance levels of 1.0, 2.0, and 3.3 percent of chord, compared with the no-clearance case. In addition to five-hole probe measurements, extensive surface flow visualizations are conducted. It is observed that for the smaller clearance cases a weak horseshoe vortex forms in the front of the blade leading edge. At all the tip gap cases, a multiple tip vortex structure with three discrete vortices around the midchord is found. The tip leakage vortex core is well defined after the midchord but does not cover a significant area in traverse planes. The presence of the tip leakage vortex results in the passage vortex moving close to the endwall and the suction side.

A Photographic Study of the Three-Dimensional Flow in a Radial Compressor

1968 ◽  
Vol 90 (3) ◽  
pp. 237-243 ◽  
Author(s):  
Y. Senoo ◽  
M. Yamaguchi ◽  
M. Nishi
Keyword(s):  
Secondary Flow ◽  
Centrifugal Compressor ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Working Fluid ◽  
Vaneless Diffuser ◽  
Three Dimensional Flow ◽  
Radial Compressor ◽  
Dimensional Flow

In order to visualize the three-dimensional flow in the impeller and the vaneless diffuser of a centrifugal compressor, water is used as the working fluid and streak lines of colored water are photographed and examined. The test is made at an extremely low speed so that streak lines do not diffuse due to turbulent mixing. The streak lines clearly demonstrate several types of secondary flow, some of which agree with what have been speculated to exist in actual compressors. Most of observed secondary flow patterns are qualitatively understandable with existing theories.

Molecular Tagging Fluorescence Velocimetry (MTFV) to Measure Meso- to Micro-Scale Thermal Flow Fields

2000 ◽  
Author(s):  
J. S. Park ◽  
K. D. Kihm ◽  
D. M. Pratt
Keyword(s):  
Capillary Flow ◽  
Three Dimensional ◽  
Surface Flow ◽  
Three Dimensional Flow ◽  
Molecular Tagging ◽  
Dimensional Flow ◽  
Thermally Driven ◽  
Thermocapillary Stress ◽  
Flow Effects ◽  
Capillary Pore

Abstract The development of a molecular tagging fluorescence velocimetry (MTFV) system is discussed and measurement results are presented for a meso-scale flow field of thermally driven capillary pore of 5-mm inner diameter that is tilted 5° from the horizon. The developed technique uses caged Dextran conjugates of caged fluorescene dyes of less than 10 nm in size for tracers. The frequency-tripled UV band (λ = 355 nm) of a pulsed Nd:YAG laser uncages the molecules by photo-cleaving that is decomposition of a caging chemical group and a fluorescence chemical group. Then a CW blue Argon-ion laser (λ = 488 nm) pumps the fluorescence of only those uncaged molecules, whose emmission band is centered at λ = 518 nm, and a sequential recording of the fluorescence images are digitally recorded and analyzed for Lagrangian velocity field mapping. The use of the technique allows detailed measurements of the thermally driven three-dimensional flow inside a heated capillary pore. The measurement shows that the meniscus surface flow is mainly driven by the thermocapillary stress field, occurring due to the surface temperature gradient, while the bulk flow inside the pore is driven largely by the natural convection buoyancy. The whole capillary flow is made by a combination of these two different flow effects. As to the heater position, above or below the interface, the three dimensional flow patterns are measured totally in the opposite way.

scholarly journals Experimental and Computational Investigation of the NASA Low-Speed Centrifugal Compressor Flow Field

1993 ◽  
Vol 115 (3) ◽  
pp. 527-541 ◽  
Author(s):  
M. D. Hathaway ◽  
R. M. Chriss ◽  
J. R. Wood ◽  
A. J. Strazisar
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Surface Flow ◽  
Computational Investigation ◽  
Complex Flow ◽  
Centrifugal Compressors ◽  
Impeller Blade ◽  
Low Speed

An experimental and computational investigation of the NASA Low-Speed Centrifugal Compressor (LSCC) flow field has been conducted using laser anemometry and Dawes’ three dimensional viscous code. The experimental configuration consists of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational analysis, and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the rotor as well as surface flow visualization along the impeller blade surfaces provide independent confirmation of the laser measurement technique. The results clearly document the development of the throughflow velocity wake, which is characteristic of unshrouded centrifugal compressors.

Three-Dimensional Flow Measurements in Conical and Straight Wall Centrifugal Compressor Vaneless Diffusers

1996 ◽  
Vol 210 (1) ◽  
pp. 51-61
Author(s):  
A Pinarbasi ◽  
M W Johnson
Keyword(s):  
Centrifugal Compressor ◽  
Velocity Fluctuation ◽  
Three Dimensional ◽  
Wake Flow ◽  
Three Dimensional Flow ◽  
Impeller Blade ◽  
Flow Measurements ◽  
Flow Angle ◽  
Dimensional Flow ◽  
Straight Wall

In the current work three-dimensional flow measurements in two types of centrifugal compressor vaneless diffuser were obtained using hot wire anemometry. The first diffuser was conical, designed to give a constant flow area, while the second straight wall diffuser had a constant axial width. Measurements of mean velocity, flow angle and velocity fluctuation level were obtained on eight cross-sectional planes in each diffuser. The jet-wake flow pattern and the impeller blade wakes are clearly visible at the inlet of both diffusers. Mixing out of the blade wake proceeds more rapidly in the straight diffuser. The hub boundary layer also develops more rapidly in this diffuser because of the adverse pressure gradient. Velocity fluctuation level measurements highlight the mixing regions within the diffusers. Recommendations are also made for the design of vaned diffusers. A larger vaneless space would be required with a straight wall diffuser and significant twisting of the vane would be required for both diffuser geometries if significant incidence losses are to be avoided.

Three-Dimensional Flow in a Low-Pressure Turbine Cascade at Its Design Condition

1987 ◽  
Vol 109 (2) ◽  
pp. 177-185 ◽  
Author(s):  
H. P. Hodson ◽  
R. G. Dominy
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Low Pressure ◽  
Surface Flow ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Three Dimensional Flow ◽  
Low Pressure Turbine ◽  
Dimensional Flow

This paper describes an experimental study of the three-dimensional flow within a high-speed linear cascade of low-pressure turbine blades. Data were obtained using pneumatic probes and a surface flow visualization technique. It is found that in general, the flow may be described using concepts derived from previous studies of high-pressure turbines. In detail, however, there are differences. These include the existence of a significant trailing shed vortex and the interaction of the endwall fluid with the suction surface flow. At an aspect ratio of 1.8, the primary and secondary losses are of equal magnitude.

An Analysis of Three-Dimensional Flow in a Centrifugal Compressor Impeller

1980 ◽  
Vol 102 (3) ◽  
pp. 619-625 ◽  
Author(s):  
C. Bosman
Keyword(s):  
Velocity Distribution ◽  
Centrifugal Compressor ◽  
Calculation Method ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Three Dimensional Flow ◽  
Blade Passage ◽  
Passage Vortex ◽  
Compressor Impeller ◽  
Blade Tip

This paper presents detailed results of the three-dimensional kinematic flow detail in a centrifugal compressor impeller of common form with inducer and straight radial blade tip sections. The calculation method, which is inviscid and is reported elsewhere, shows the development of a passage vortex in a sense counter to that of blade rotation, initiated in the inducer and disappearing as the flow becomes radial. This vortex unloads the blade shroud sections and combined with slip at the blade tips, produces a jetwake velocity distribution at the blade passage exit. General features of the calculation are at variance with two-dimensional calculations but are in agreement with the experimental results of other workers.

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