scholarly journals Numerical Analysis of a Novel Twin-Impeller Centrifugal Compressor

Computation ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 143
Author(s):  
Van Thang Nguyen ◽  
Amélie Danlos ◽  
Florent Ravelet ◽  
Michael Deligant ◽  
Moises Solis ◽  
...  
Keyword(s):  
Active Control ◽  
Control Method ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Autonomous Systems ◽  
Thermodynamic Characteristics ◽  
Rotating Stall ◽  
Low Flow ◽  
Inlet Guide Vane ◽  
Operating Range

Centrifugal compressors are widely used in many industrial fields such as automotive, aviation, aerospace. However, these turbomachines suffer instability phenomenon when the flow rate is too high or too low, called rotating stall and surge. These phenomena cause the operation failure, pressure fluctuations and vibrations of the thorough system. Numerous mechanical solutions have been presented to minimize these instabilities and expand the operating range towards low-flow rates like active control of the flow path, variable inlet guide vane and casing treatment. Currently, our team has developed a novel compressor composed of a twin-impeller powered by autonomous systems. We notice the performance improvement and instabilities suppression of this compressor experimentally. In this paper, an active control method is introduced by controlling the speed and rotation direction of the impellers to expand the operating range. A CFD study is then conducted to analysis flow morphology and thermodynamic characteristics based on the experimental observations at three special points. Numerical results and experimental measurements of compressor maps are consistent.

scholarly journals CFD Analysis to explain the Operating range extension observed during Operation in Co-rotating Mode of a Twin-impeller Centrifugal Compressor

2021 ◽  
Vol 321 ◽  
pp. 02011
Author(s):  
Van-Thang Nguyen ◽  
Amelie Danlos ◽  
Florent Ravelet ◽  
Michael Deligant ◽  
Moises Solis ◽  
...  
Keyword(s):  
Guide Vane ◽  
Pressure Fluctuations ◽  
Autonomous Systems ◽  
Thermodynamic Characteristics ◽  
Industrial Applications ◽  
Rotating Stall ◽  
Low Flow ◽  
Inlet Guide Vane ◽  
Flow Rates ◽  
Operating Range

Centrifugal compressors are widely used in many industrial applications because of their advantages. However, these turbomachines suffer at a low-flow rate from instabilities, such as rotating stall and surge. That leads to operational failure, pressure fluctuations and vibrations of the thorough system. Many mechanical solutions minimize these instabilities and expand the operating range towards low-flow rates like active control of the flow path, variable inlet guide vane and casing treatment. Currently, our team has developed a new compressor composed of a twin-impeller powered by autonomous systems. We notice the performance improvement and instabilities suppression of this compressor experimentally. In this paper, a CFD study is presented to explain some of these experimental observations by analyzing the inside of twin-impeller, the flow structures and thermodynamic characteristics at low flow rates operating in a co-rotating mode. Numerical results and experimental measurements of compressor maps are consistent.

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.

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.

Numerical Study of Variable Camber Inlet Guide Vane on Low Speed Axial Compressor

2015 ◽  
Author(s):  
Emandi Rajesh ◽  
Bhaskar Roy
Keyword(s):  
High Efficiency ◽  
Numerical Study ◽  
Guide Vane ◽  
Pressure Ratio ◽  
Inlet Guide Vane ◽  
Operating Range ◽  
Clockwise Direction ◽  
High Diffusion ◽  
Stable Operating ◽  
Stagger Angle

The modern engine has the requirement of high pressure ratio compressors. High diffusion blades are used to cater to this requirement. The high diffusion blades suffer from the low incidence range. A variable geometry inlet guide vane is used to improve the incidence range and to have an increased stable operating range. In this paper a variable camber inlet guide is proposed in place of an existing inlet guide vane (IGV) to operate the compressor at increased stable operating range or to operate at improved efficiency at off design point. Numerical analysis is carried out in ANSYS CFX©. The existing compressor consists of IGV (20 blades) , rotor (43 blades) and stator (52 blades). The rotor rotates at 2400 rpm in clockwise direction. The IGV blade is split two part forward blade and aft blade. Numerical studies are conducted to study the effect of varying the stagger angle on the performance of the compressor. The aft blade is given rotation in clockwise direction for +5° and +10°. The numerical results obtained are compared to the same stagger angle with full blades. It is observed that marginal improvement in the pressure ratio and efficiency. 7% stall margin improvement is achieved with slotted blade in place a fixed IGV at 0° setting angle. A new compressor characteristics is estimated which shows that the compressor can be operated to the left of the fixed-IGV-stage peak pressure with high efficiency.

Numerical Results for Axial Flow Compressor Instability

1989 ◽  
Vol 111 (4) ◽  
pp. 434-441 ◽  
Author(s):  
F. E. McCaughan
Keyword(s):  
Guide Vane ◽  
Axial Flow ◽  
Pressure Rise ◽  
Companion Paper ◽  
Extensive Study ◽  
Rotating Stall ◽  
Numerical Results ◽  
Flow Diagram ◽  
Inlet Guide Vane ◽  
Flow Compressor

Using Cornell’s supercomputing facilities, we have carried out an extensive study of the Moore–Greitzer model, which gives accurate and reliable information about compressor instability. The bifurcation analysis in the companion paper shows the dependence of the mode of compressor response on the shape of the rotating stall characteristic. The numerical results verify and extend this with a more accurate representation of the characteristic. The effect of the parameters on the shape of the rotating stall characteristic is investigated, and it is found that the parameters with the strongest effects are the inlet length, and the shape of the compressor pressure rise versus mass flow diagram (i.e., tall diagrams versus shallow diagrams). We also discuss the effects of inlet guide vane loss on the characteristic. An evaluation is made of the h′ = −g approximation, and a spectral analysis of the rotating stall cell given by the full model suggests why this breaks down.

Unstable Characteristics and Rotating Stall in Turbine Brake Operation of Pump-Turbines

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Christian Widmer ◽  
Thomas Staubli ◽  
Nathan Ledergerber
Keyword(s):  
Electricity Market ◽  
Flow Instability ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Vortex Formation ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Momentum Exchange ◽  
Pump Turbine ◽  
Stationary Vortex

Reversible pump-turbines are versatile in the electricity market since they can be switched between pump and turbine operation within a few minutes. The emphasis on the design of the more sensitive pump flow however often leads to stability problems in no load or turbine brake operation. Unstable characteristics can be responsible for hydraulic system oscillations in these operating points. The cause of the unstable characteristics can be found in the blocking effect of either stationary vortex formation or rotating stall. The so-called unstable characteristic in turbine brake operation is defined by the change of sign of the slope of the head curve. This change of sign or “S-shape” can be traced back to flow recirculation and vortex formation within the runner and the vaneless space between runner and guide vanes. When approaching part load from sound turbine flow the vortices initially develop and collapse again. This unsteady vortex formation induces periodical pressure fluctuations. In the turbine brake operation at small guide vane openings the vortices increase in intensity, stabilize and circumferentially block the flow passages. This stationary vortex formation is associated with a total pressure rise over the machine and leads to the slope change of the characteristic. Rotating stall is a flow instability which extends from the runner, the vaneless space to the guide and the stay vane channels at large guide vane openings. A certain number of channels is blocked (rotating stall cell) while the other channels comprise sound flow. Due to a momentum exchange between rotor and stator at the front and the rear cell boundary, the cell is rotating with subsynchronous frequency of about 60 percent of the rotational speed for the investigated pump-turbine (nq = 45). The enforced rotating pressure distributions in the vaneless space lead to large dynamic radial forces on the runner. The mechanisms leading to stationary vortex formation and rotating stall were analyzed with a pump-turbine model by the means of numerical simulations and test rig measurements. It was found that stationary vortex formation and rotating stall have initially the same physical cause, but it depends on the mean convective acceleration within the guide vane channels, whether the vortex formations will rotate or not. Both phenomena lead to an unstable characteristic.

Simulation of air jets for controlling stall in a centrifugal fan

2014 ◽  
Vol 229 (11) ◽  
pp. 2045-2055 ◽  
Author(s):  
Zhang Lei ◽  
Wang Rui ◽  
Yuan Wei ◽  
Wang Songling
Keyword(s):  
Active Control ◽  
Stokes Equations ◽  
Control Method ◽  
Safety Margin ◽  
Stability Margin ◽  
Rotating Stall ◽  
Enhancement Effect ◽  
Centrifugal Fan ◽  
Stall Inception ◽  
Active Control Method

The main goal of the present work is to analyze the three-dimensional unsteady flow field of a centrifugal fan by solving Navier–Stokes equations, coupled with the throttle condition. The results show that rotating stall occurs in the original fan when the flow rate is 4.30 m3/s, and the stall inception first appears at three impeller passages near the volute tongue and front disc. An active control method is proposed to inhibit the stall inception, which involves blowing air at the inlets of the three impeller passages. This blowing control method cannot inhibit the stall inception when the blowing speed is lower than 50 m/s. The stability margin of the centrifugal fan is extended when the blowing speed is increased from 50 to 110 m/s, while no further effect is obvious with a further increase in the blowing speed. At a blowing speed of 110 m/s, rotating stall occurs again when the fan flow reaches 3.46 m3/s. After the application of the nozzle blowing, the safety margin of the centrifugal fan is extended by 13%, and an obvious stability enhancement effect is achieved. From an engineering standpoint, this new active control method for rotating stall offers a valuable means to ensure the safe operation of a centrifugal fan.

Variations in Upstream Vane Loading With Changes in Back Pressure in a Transonic Compressor

1998 ◽  
Vol 122 (3) ◽  
pp. 433-441 ◽  
Author(s):  
Douglas P. Probasco ◽  
Tim J. Leger ◽  
J. Mitch Wolff ◽  
William W. Copenhaver ◽  
Randall M. Chriss
Keyword(s):  
Surface Pressure ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Back Pressure ◽  
Bow Shock ◽  
Navier Stokes ◽  
Inlet Guide Vane ◽  
Transonic Compressor ◽  
Unsteady Surface Pressure ◽  
Upstream Pressure

Dynamic loading of an inlet guide vane (IGV) in a transonic compressor is characterized by unsteady IGV surface pressures. These pressure data were acquired for two spanwise locations at a 105 percent speed operating condition, which produces supersonic relative Mach numbers over the majority of the rotor blade span. The back pressure of the compressor was varied to determine the effects from such changes. Strong bow shock interaction was evident in both experimental and computational results. Variations in the back pressure have significant influence on the magnitude and phase of the upstream pressure fluctuations. The largest unsteady surface pressure magnitude, 40 kPa, was obtained for the near-stall mass flow condition at 75 percent span and 95 percent chord. Radial variation effects caused by the spanwise variation in relative Mach number were measured. Comparisons to a two-dimensional nonlinear unsteady blade/vane Navier–Stokes analysis show good agreement for the 50 percent span results in terms of IGV unsteady surface pressure. The results of the study indicate that significant nonlinear bow shock influences exist on the IGV trailing edge due to the downstream rotor shock system. [S0889-504X(00)00303-2]

Effect of Clocking on the Unsteady Rotor Blade Loading in a 1.5-Stage Low-Speed Axial Compressor

2007 ◽  
Author(s):  
Huixia Jia ◽  
Konrad Vogeler
Keyword(s):  
Guide Vane ◽  
Pressure Fluctuations ◽  
Suction Side ◽  
Rotor Blades ◽  
Inlet Guide Vane ◽  
Mean Values ◽  
Design Point ◽  
Low Speed ◽  
Unsteady Pressure ◽  
Pressure Distributions

This paper presents the effect of clocking on the unsteady loading of the rotor blades in the first stage with an inlet guide vane row (IGV) of the Dresden Low-Speed Research Compressor (LSRC). The unsteady flow field of the Dresden LSRC at 10 IGV clocking positions for the design point was investigated using a 3D time-accurate viscous solver. The time-averaged pressure distributions on the pressure side (PS) and the suction side (SS) of the rotor blades at midspan (MS) are presented for different clocking positions. The effect of the clocking on the time-averaged Root Mean Square-value (RMS) of the unsteady pressure fluctuations of the rotor blades at MS is investigated. The unsteady pressure fluctuations on the PS and the SS of the rotor blades at MS for different clocking positions are presented and discussed. The unsteady blade pressure forces on the rotor blades, which are calculated from the profile pressure distributions, are presented and analysed for different clocking positions. The maximal fluctuation amplitude of the unsteady pressure forces on the rotor blades, which fluctuate around the nearly identical mean values for different clocking positions, can be reduced about 60 percent with the IGV clocking for the design point in the investigated configuration. The effect of the clocking on the time-resolved inlet- and outlet flow fields of the rotor blades is investigated and discussed.

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