Suppression of flow instability in the Francis hydro turbine draft tube by J-groove shape optimization at a partial flow rate

2021 ◽  
Author(s):  
Ujjwal Shrestha ◽  
Young-Do Choi
Keyword(s):  
Shape Optimization ◽  
Flow Rate ◽  
Flow Instability ◽  
Draft Tube ◽  
Hydro Turbine ◽  
Groove Shape

scholarly journals Stereo-PIV investigation of the unsteady flow in the draft tube of a model hydro turbine

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Ivan Litvinov ◽  
Dmitry Sharaborin ◽  
Sergey Shtork ◽  
Vladimir Dulin ◽  
Sergey Alekseenko ◽  
...  
Keyword(s):  
Velocity Field ◽  
Unsteady Flow ◽  
Swirling Flow ◽  
Flow Instability ◽  
Draft Tube ◽  
Pressure Pulsations ◽  
Mean Velocity ◽  
Hydro Turbine ◽  
Operation Conditions ◽  
Wide Range

Varying the generator load of a hydro turbine results in short-term changes in the rotation frequency of the runner, leading inevitably to flow instability and strong flow swirling behind the turbine. This may lead to the formation of unsteady flow regimes featured by vortex instability of the swirling flow behind the runner, known as the precessing vortex core (PVC) Dorfler et al. (2012). This effect causes dangerous periodic pressure pulsations that propagate throughout the water column in the draft tube. The present study reports on stereo PIV measurements of the air flow field inside a transparent draft tube of a model hydro turbine for a wide range of operation conditions. The research is focused on the time-averaged flow properties (mean velocity field and the second-order moments of velocity fluctuations), pressure pulsations and coherent flow structures in the velocity field.

Effect of draft tube diameter on nitrogen removal from domestic sewage in a draft tube type reactor

1998 ◽  
Vol 38 (1) ◽  
pp. 319-326
Author(s):  
Taku Fujiwara ◽  
Iso Somiya ◽  
Hiroshi Tsuno ◽  
Yoshio Okuno
Keyword(s):  
Flow Rate ◽  
Nitrogen Removal ◽  
Draft Tube ◽  
Domestic Sewage ◽  
Tube Diameter ◽  
Continuous Treatment ◽  
Anoxic Zone ◽  
Type Reactor ◽  
Tube Type ◽  
Volumetric Loading

The effect of the ratio of draft tube diameter to reactor diameter (Di/Do) on the efficiency of nitrogen removal from domestic sewage is discussed based on liquid-circulating flow rate and continuous treatment data. More than 2.5 minutes of circulation time in the annulus part, which is required to create an anoxic zone, could be maintained under operating conditions in which air flow rate per reactor volume was 2 m3/(m3 · hr) and Di/Do was 0.19. When Di/Do was set at 0.19, the average total organic carbon (TOC), total nitrogen (TN) and dissolved nitrogen (DN) removal efficiencies were 83.2%, 72.1% and 71.6%, respectively, which were higher than those when Di/Do was at 0.26 or 0.36. From these results, it is concluded that 0.19 is the best Di/Do for nitrogen removal in a draft-tube type reactor with an effective depth of 4.0m under the treatment condition in which the BOD volumetric loading rate is in the range 0.22 to 0.46 kgBOD/(m3 · day). More than 80% nitrification and denitrification efficiencies can be achieved simultaneously when both conditions, the aerobic zone ratio being more than 0.2, and the anoxic zone ratio being more than 0.3, are satisfied.

scholarly journals Centrifugal Compressor Stall Control by the Application of Engineered Surface Roughness on Diffuser Shroud Using Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2033
Author(s):  
Amjid Khan ◽  
Muhammad Irfan ◽  
Usama Muhammad Niazi ◽  
Imran Shah ◽  
Stanislaw Legutko ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Flow Instability ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Low Mass

Downsizing in engine size is pushing the automotive industry to operate compressors at low mass flow rate. However, the operation of turbocharger centrifugal compressor at low mass flow rate leads to fluid flow instabilities such as stall. To reduce flow instability, surface roughness is employed as a passive flow control method. This paper evaluates the effect of surface roughness on a turbocharger centrifugal compressor performance. A realistic validation of SRV2-O compressor stage designed and developed by German Aerospace Center (DLR) is achieved from comparison with the experimental data. In the first part, numerical simulations have been performed from stall to choke to study the overall performance variation at design conditions: 2.55 kg/s mass flow rate and rotational speed of 50,000 rpm. In second part, surface roughness of magnitude range 0–200 μm has been applied on the diffuser shroud to control flow instability. It was found that completely rough regime showed effective quantitative results in controlling stall phenomena, which results in increases of operating range from 16% to 18% and stall margin from 5.62% to 7.98%. Surface roughness as a passive flow control method to reduce flow instability in the diffuser section is the novelty of this research. Keeping in view the effects of surface roughness, it will help the turbocharger manufacturers to reduce the flow instabilities in the compressor with ease and improve the overall performance.

scholarly journals Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1182
Author(s):  
Seung-Jun Kim ◽  
Yong Cho ◽  
Jin-Hyuk Kim
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Air Injection ◽  
Low Flow ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Vortex Rope

Under low flow-rate conditions, a Francis turbine exhibits precession of a vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration of the turbine performance as manifested by torque and power output fluctuations. In order to suppress the rope with precession and a swirl component in the tube, the use of anti-swirl fins was investigated in a previous study. However, vortex rope generation still occurred near the cone of the tube. In this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted with a scale-adaptive simulation shear stress transport turbulence model. This model was used to observe the effects of the injection in the draft tube on the unsteady internal flow and pressure phenomena considering both active and passive suppression methods. The air injection affected the generation and suppression of the vortex rope and swirl component depending on the flow rate of the air. In addition, an injection level of 0.5%Q led to a reduction in the maximum unsteady pressure characteristics.

scholarly journals Minimum spoutable gas flow rate in side-outlet spouted bed with inner draft-tube.

1981 ◽  
Vol 14 (6) ◽  
pp. 462-466 ◽  
Author(s):  
HIROTSUGU HATTORI ◽  
KAZUYUKI TANAKA ◽  
KUNIHIKO TAKEDA
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Draft Tube ◽  
Gas Flow Rate ◽  
Spouted Bed ◽  
Side Outlet

Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor With Inlet Distortion

2020 ◽  
Author(s):  
Sasuga Ito ◽  
Masato Furukawa ◽  
Satoshi Gunjishima ◽  
Takafumi Ota ◽  
Kazuhito Konishi ◽  
...  
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Flow Instability ◽  
Pressure Sensors ◽  
Low Flow ◽  
Inlet Distortion ◽  
Transonic Centrifugal Compressor ◽  
Response Pressure ◽  
Surge Phenomena ◽  
Low Flow Rate

Abstract Inlet distortion has influence on the aerodynamic performance of turbomachinery such as compressors, turbines and fans. On turbochargers, bent pipes are installed around the compressor due to the spatial limitations in the engine room of the vehicle. As the result, the compressor is operated with the distorted inflow. In the low flow rate operation, the distorted inflow also affects the flow instability like stall and surge. Especially, the operation range on the low flow rate side is defined based on the flow rate where surge occurs, so it is important to investigate the effect of the distorted inflow on surge. In this study, the effect of the inlet distortion to surge phenomena has been investigated by the experiments with a transonic centrifugal compressor. A bent pipe has been installed at the upstream of the compressor to generate a distorted flow. Experiments have been also conducted under the condition that a straight pipe was installed upstream of the compressor, and unsteady measurements with high response pressure sensors and an I-type hot wire probe have been carried out to each experiments. In addition, Fast Fourier transform (FFT) and Wavelet transform have been applied to the unsteady measurement results obtained from each experiment.

Research on Effects of Groove Shape Optimization on Cavitation and Lubricating Characteristics for Microgroove Rotary Seal

2017 ◽  
Vol 61 (3) ◽  
pp. 569-584 ◽  
Author(s):  
Bing Xue ◽  
Chao Wei ◽  
Ji Bin Hu ◽  
Yi Min Zhao
Keyword(s):  
Shape Optimization ◽  
Groove Shape ◽  
Rotary Seal

Flow-Rate Observers in the Suppression of Compressor Surge Using Active Magnetic Bearings

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Se Young Yoon ◽  
Zongli Lin ◽  
Wei Jiang ◽  
Paul E. Allaire
Keyword(s):  
Flow Rate ◽  
High Performance ◽  
Flow Instability ◽  
Characteristic Curve ◽  
Estimation Method ◽  
Industrial Applications ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Initiation Point ◽  
Surge Margin

Surge is a dynamic flow instability that can cause extensive damage to compressors and other components. One common challenge that many surge control methods in the literature face when implemented in industrial applications is the unavailability of the high performance actuators and accurate flow rate measurements that are required to suppress surge. In this paper we present the experimental results of employing active magnetic bearings in order to suppress the surge instability in a centrifugal compressor. In addition, we compare how the selection of the flow estimation method affects the effectiveness of the implemented surge suppression controller. The experimental data demonstrates that the best combination of controller and flow estimator tested in this work allows the compressor to operate deep into the former surge region when the controller is activated, moving the minimum flow rate at the surge initiation point by 21%. This allows the compression system to operate at the highest efficiency/pressure point in the characteristic curve, while still retaining a very conservative surge margin separating the allowed compressor operating region from the surge inception point even if unexpected system changes occur.

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