scholarly journals Design and Analysis of a Split Deswirl Vane in a Two-Stage Refrigeration Centrifugal Compressor

2014 ◽  
Vol 6 ◽  
pp. 130925 ◽  
Author(s):  
Jeng-Min Huang ◽  
Yue-Hann Tsai
Keyword(s):  
Centrifugal Compressor ◽  
Rotation Angle ◽  
Guide Vane ◽  
Low Flow ◽  
Working Fluid ◽  
Inlet Guide Vane ◽  
Two Stage ◽  
Double Row ◽  
Second Stage ◽  
Better Than

This study numerically investigated the influence of using the second row of a double-row deswirl vane as the inlet guide vane of the second stage on the performance of the first stage in a two-stage refrigeration centrifugal compressor. The working fluid was R134a, and the turbulence model was the Spalart-Allmaras model. The parameters discussed included the cutting position of the deswirl vane, the staggered angle of two rows of vane, and the rotation angle of the second row. The results showed that the performance of staggered angle 7.5° was better than that of 15° or 22.5°. When the staggered angle was 7.5°, the performance of cutting at 1/3 and 1/2 of the original deswirl vane length was slightly different from that of the original vane but obviously better than that of cutting at 2/3. When the staggered angle was 15°, the cutting position influenced the performance slightly. At a low flow rate prone to surge, when the second row at a staggered angle 7.5° cutting at the half of vane rotated 10°, the efficiency was reduced by only about 0.6%, and 10% of the swirl remained as the preswirl of the second stage, which is generally better than other designs.

Study of a Surge-Free Centrifugal Compressor With Automatically Variable Inlet and Diffuser Vanes

1996 ◽  
Author(s):  
Hideomi Harada
Keyword(s):  
Centrifugal Compressor ◽  
Guide Vane ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Low Flow ◽  
Inlet Guide Vane ◽  
Analysis Method ◽  
Unstable Flow ◽  
Flow Angle ◽  
Operating Range

In order to improve the operating range of a centrifugal compressor, computer-controlled variable inlet and diffuser vanes were attached to a compressor with a pressure ratio of 2.5. Low-solidity cascade vanes capable of controlling the vane angle up to 0 degrees from the tangential direction were used for the vaned diffuser. The compressor’s overall performance was then tested using a closed-loop test stand. By automatically adjusting the diffuser vanes to the most suitable flow angle, pressure fluctuations caused by the unstable flow in the diffuser during low-flow operation of the centrifugal compressor could be suppressed, and the compressor could be operated nearly up to the shut-off flow rate without any surge. The author experimentally confirmed the critical operating range of both the impeller and diffuser at two different tip speeds and five inlet guide vane angles. Furthermore, a three-dimensional viscous flow-analysis method was applied to the impeller, and a three-dimensional momentum integral analysis method was applied to the diffuser. Then the critical operating ranges obtained in the experiments were qualitatively validated. The operating range of a centrifugal compressor under low-flow conditions, which has until now been limited because of surge, dramatically improved in this study, thereby demonstrating that it may be possible to develop a surge-free centrifugal compressor.

Experimental analysis of the influence of outlet network volume and inlet guide vane positioning on surge behavior in a single-stage low-speed centrifugal compressor

2017 ◽  
Vol 232 (4) ◽  
pp. 350-363 ◽  
Author(s):  
Kirill Kabalyk ◽  
Michal Jasek ◽  
Grzegorz Liskiewicz ◽  
Longin Horodko
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Guide Vane ◽  
Single Stage ◽  
Low Flow ◽  
Inlet Guide Vane ◽  
Vaneless Diffuser ◽  
Time Resolved ◽  
Low Speed ◽  
Deep Well

The paper focuses on experimental investigation of the influence of outlet network volume and type on the course of surge in a single-stage low-speed centrifugal compressor. The test rig design is based on a 330 mm impeller (tip Mach number of 0.33) coupled with a vaneless diffuser and a scroll. During the measurements, the rig has been successively connected to a four meter long pipe and to an 11.8 m deep well. Time-averaged probing of pressures and temperatures has served to obtain the performance maps with both networks at three different positions of inlet guide vanes. Time-resolved measurements of static pressure were done in three chosen locations of the rig and enabled to trace the formation of flow instabilities at low flow rates. The analysis of received dataset revealed a reasonable impact of network design on the inception moment, quantitative and qualitative traits of deep surge. The most significant changes concerned the frequencies of the first surge harmonics and the nature of the process. “Pipeline-surge” reminded more of a standing wave whereas “plenum-surge”—of a periodic process similar to the ones reported in the referenced studies.

Unsteady Flow Around Suction Elbow and Inlet Guide Vanes in a Centrifugal Compressor

2004 ◽  
Author(s):  
Michael M. Cui
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Guide Vane ◽  
Power Laws ◽  
Working Fluid ◽  
Inlet Guide Vane ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Compressor Design

A suction elbow and inlet guide vanes (IGVs) are typical upstream components in the front of the first-stage impeller in a centrifugal compressor. Since the flow field in the front of the impeller is subsonic, the flow motion induced by the rotating impeller interacts with the elbow and IGVs. These interactions induce turbulent unsteady flows inside compressors. The resulted unsteadiness affects efficiency, vibration, and noise generation of the compressor. To understand the mechanism controlling the interactions between up-steam components and to optimize the compressor design for better efficiency and reliability, the turbulent unsteady flow inside the first-stage of the compressor was simulated. The model includes the suction elbow, inlet guide vane housing, and first-stage impeller. HFC 134a was used as the working fluid. The thermodynamic and transport properties of the refrigerant gas were modeled by the Martin-Hou equation of state and power laws, respectively. The three-dimensional unsteady flow field was numerically simulated. The overall performance parameters were obtained by integrating the field quantities. The force, torque, and the arm of moments acting on the IGVs are then calculated. The results can be used to improve centrifugal compressor design to achieve higher efficiency and improve reliability.

scholarly journals Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor

1998 ◽  
Author(s):  
I. Kassens ◽  
M. Rautenberg
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Guide Vane ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Inlet Guide Vane ◽  
Flow Measurements ◽  
Flow Angle ◽  
Partial Load ◽  
Measurement Location

In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller. The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured. Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.

Low Reynolds-Number Experiments in an Axial-Flow Turbomachine

1964 ◽  
Vol 86 (3) ◽  
pp. 257-295 ◽  
Author(s):  
J. Neustein
Keyword(s):  
Reynolds Number ◽  
Guide Vane ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Low Flow ◽  
Working Fluid ◽  
Low Reynolds Numbers ◽  
Blade Row ◽  
Overall Performance ◽  
Low Reynolds

The performance of a single-stage, axial-flow turbomachine was studied experimentally at low Reynolds numbers. The study was made with a turbomachine modeled from a large jet-engine type of axial-flow compressor. Low Reynolds numbers were obtained by using a mixture of glycerine and water as the working fluid. The overall performance was determined over a range of Reynolds numbers RT (based on rotor-tip speed and rotor chord) from 2000 to 150,000. The flow rate at each Reynolds number was varied from near shutoff to the maximum permitted by the turbomachine-tunnel systems. Blade-row characteristics were studied by means of quantitative flow surveys before and after each blade row, and by means of extensive flow-visualization experiments within each blade row. The investigation established that sudden or critical changes in performance do not occur in the type of machine tested, between RT of 150,000 and 20,000. Below 20,000 the performance deteriorated more rapidly. A relatively sharp change in performance occurred between RT of 20,000 and 10,000. The results clarified many of the viscous flow details in each blade row which are associated with the deterioration of performance. These effects were very pronounced at RT of 4000 and below. Consequently, a considerable part of the paper is concerned with results obtained at these lower Reynolds numbers. From the point of view of a designer, information is presented in regard to overall performance, guide-vane turning, and guide-vane and stator total-pressure losses, all as functions of Reynolds number. These results are expected to be indicative of performance in turbomachines similar to the one tested here. Other details are concerned with problems such as wall boundary layers, flow reversal at low flow coefficients, lip-clearance flow, flow patterns near shutoff, and flow comparisons in stators with rotating and stationary hubs.

scholarly journals Comparison of estimators in one-phase two-stage Poisson sampling in forest inventories

2012 ◽  
Vol 42 (10) ◽  
pp. 1865-1871 ◽  
Author(s):  
Daniel Mandallaz ◽  
Alexander Massey
Keyword(s):  
Small Area ◽  
Two Stage ◽  
Random Sample Size ◽  
Poisson Sampling ◽  
Second Stage ◽  
Forest Inventories ◽  
Unbiased Estimates ◽  
The Mean ◽  
Concentric Circles ◽  
Better Than

In the context of Poisson sampling, numerous adjustments to classical estimators have been proposed that are intended to compensate for inflated variance due to random sample size. However, such adjustments have never been applied to extensive forest inventories. This work investigates the performances of four estimators for the timber volume in one-phase two-stage forest inventories, where trees in the first stage are selected, at the plot level, by concentric circles or angle-count methods and a subset thereof are selected by Poisson sampling for further measurements to get a better estimation. The original two-stage estimator is the sum of two components: the first is the mean of Horwitz–Thompson estimators using simple volume approximations, based on diameter and species alone, of all first-stage trees in each inventory plot, and the second is the mean of Horwitz–Thompson estimators based on the differences between the simple volume approximations and refined volume determinations based on further diameter and height measurements on the second-stage trees within each inventory plot. This two-stage estimator is particularly useful because it provides unbiased estimates even if the simple prediction model is not correct, which is particularly important for small area estimation. The other three estimators rely on adjustments of the second component of the original estimator that are adapted from estimators proposed in the literature by L.R. Grosenbaugh and C.-E. Särndal. It turns out that these adjustments introduce a negligible bias and that the original simple estimator performs just as well or even better than the new estimators with respect to the variance.

Variable Inlet Guide Vane Effect on Centrifugal Compressor Performance in Wet Gas Flow

2016 ◽  
Author(s):  
Levi André B. Vigdal ◽  
Lars E. Bakken
Keyword(s):  
Centrifugal Compressor ◽  
Guide Vane ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Compressor Stage ◽  
Guide Vanes ◽  
Wet Gas ◽  
Compressor Performance

The introduction of variable inlet guide vanes (VIGVs) upfront of a compressor stage affects performance and permits tuning for off-design conditions. This is of great interest for emerging technology related to subsea compression. Unprocessed gas from the wellhead will contain liquid condensate, which affects the operational condition of the compressor. To investigate the effect of guide vanes on volume flow and pressure ratio in a wet gas compressor, VIGVs are implemented upfront of a centrifugal compressor stage to control the inlet flow direction. The guide vane geometry and test rig setup have previous been presented. This paper documents how changing the VIGV setting affects compressor performance under dry and wet operating conditions. The reduced performance effect and operating range at increased liquid content are of specific interest. Also documented is the change in the VIGV effect relative to the setting angle.

Wastewater Minimisation Using a Heuristic Procedure

2004 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhi-Yong Liu ◽  
Zisheng Jason Zhang ◽  
Linna Hu ◽  
Zhaoliang Wu
Keyword(s):  
Mass Balance ◽  
Heuristic Procedure ◽  
Heuristic Rules ◽  
Two Stage ◽  
Flow Rates ◽  
Second Stage ◽  
Better Than

A two-stage procedure is proposed for the minimisation of wastewater. In the first stage, heuristic rules are used to find the initial feasible flowsheet; in the second stage, the flow rates of streams in the initial flowsheet are determined by mass balance of the contaminants. The operations considered in this work include re-use, regeneration, mixing and bypassing of water streams. The proposed procedure is simple and the results of the examples studied are comparable with or better than those found in the literature.

Experimental and numerical analysis of the unsteady influence of an inlet guide vane

2011 ◽  
Vol 226 (3) ◽  
pp. 660-680 ◽  
Author(s):  
L Zhou ◽  
H-Z Fan ◽  
W Wei ◽  
Y-H Cai
Keyword(s):  
Numerical Analysis ◽  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Guide Vane ◽  
Low Frequency ◽  
Inlet Guide Vane ◽  
Vaneless Diffuser ◽  
Basic Frequency ◽  
Low Frequency Oscillations ◽  
And Performance

The unsteady inlet guide vane (IGV)–impeller–diffuser interaction in a centrifugal compressor is investigated numerically and experimentally under different IGV prewhirl angles. The influence of IGV prewhirl angle on the flowfield and the unsteadiness of the impeller and diffuser are studied, and the mechanism of the unsteady IGV–impeller–diffuser interaction is explored. Results show that quite fair quantitative agreements are achieved between the predicted and measured flowfield. The IGV wake can decrease the unsteadiness on the impeller and diffuser, and the reduction of the unsteadiness caused by the IGV is a function of the IGV prewhirl angle. The unsteadiness in the diffuser with negative IGV angles is larger than that for positive prewhirl angles. The low-frequency oscillations inside the flowfield are induced by the IGV. When IGV prewhirl occurs, the basic frequency of the unsteady flow in the vaneless diffuser is mainly half of the blade passing frequency of the impeller. In practice, the IGV prewhirl angle can be adjusted to avoid unsteady vibrations in some off-design conditions, with reliability and performance improved simultaneously.

scholarly journals An Analysis of Spatial Nonuniformity of the Flow at the Entrance Section of the Axial-Radial Impeller of a Centrifugal Compressor Stage Working on Regulation Modes

2019 ◽  
pp. 30-40
Author(s):  
A.D. Vanyashov ◽  
V.V. Karabanova
Keyword(s):  
Centrifugal Compressor ◽  
Guide Vane ◽  
Inlet Guide Vane ◽  
Compressor Stage ◽  
Turning Angle ◽  
Centrifugal Compressor Stage ◽  
Entrance Section ◽  
Spatial Nonuniformity ◽  
Optimum Diameter ◽  
Significant Difference

The article presents an analysis of the experimental data on testing a centrifugal compressor stage on regulation modes by changing the rotational speed of the rotor and the turning angle of the blades in the inlet guide vane unit. The distribution of the angles of attack at the entrance section of the impeller in relation to the blade height is obtained. It is established that a significant difference in the angles of attack from the plug to the periphery influences the polytropic efficiency of the compressor stage. Recommendations are given on the improvement of the mechanism of regulation by the inlet guide vane unit and on the choice of the optimum diameter for the entrance part of the driving impeller blades.

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