scholarly journals Phase Distribution in the Tip Clearance of a Multiphase Pump at Multiple Operating Points and Its Effect on the Pressure Fluctuation Intensity

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 556
Author(s):  
Guangtai Shi ◽  
Zongku Liu ◽  
Xiaobing Liu ◽  
Yexiang Xiao ◽  
Xuelin Tang
Keyword(s):  
Phase Velocity ◽  
Pressure Fluctuation ◽  
Phase Distribution ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Two Phase ◽  
Multiphase Pump ◽  
Fluctuation Intensity ◽  
Operating Points ◽  
Multiple Operating Points

Tip clearance has a great effect on the flow and pressure fluctuation characteristics in a multiphase pump, especially at multiple operating points. The phase distribution and pressure fluctuation in tip clearance in a multiphase pump are revealed using the CFD (computational fluid dynamics) technology and high-speed photography methods. In this paper, the phase distribution, the gas-liquid two-phase velocity slip, and the pressure fluctuation intensity are comprehensively analyzed. Results show with the increase of the tip clearance, the multiphase pump pressurization performance is obviously deteriorated. In the meantime, the gas accumulation mainly occurs at the hub, the blade suction side (SS), and the tip clearance, and the maximum gas-liquid two-phase velocity difference is near the impeller streamwise of 0.4. In addition, the tip clearance improves the gas-liquid two-phase distribution in the pump, that is, the larger the tip clearance is, the more uniform the gas-liquid distribution becomes. Furthermore, the gas leads to the maximum pressure fluctuation intensity in the tip clearance which is closer to the tip leakage flow (TLF) outlet, and has a greater effect on the degree of flow separation in the tip clearance.

Flow Visualization of Unsteady and Transient Phenomena in a Mixed-Flow Multiphase Pump

2016 ◽  
Author(s):  
Alberto Serena ◽  
Lars E. Bakken
Keyword(s):  
Two Phase Flow ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Homogeneous Distribution ◽  
Phase Flow ◽  
Two Phase ◽  
Inlet Flow ◽  
Transient Phenomena ◽  
Multiphase Pump

The flow inside of turbomachines rotating channels, when operating away from the design point, is intrinsically unsteady; two-phase flow and part-load operation further complicate the analysis, introducing additional challenges. Transient phenomena, linked to the typical unsteadiness of multiphase flows (bubble formation, coalescence or breakdown, segregation and gas locking) and to variable inlet flow compositions, as in case of slug flow, require advanced analysis tools which can reveal the local flow mechanisms responsible for performance degradation and instabilities. General trends can be outlined, but the air accumulation zones and two-phase flow patterns are highly dependent on the machine design. The flow regimes vary from a homogeneous distribution of fine bubbles, evenly dispersed and carried away by the main flow, to more complex flow patterns, especially when the phases separate or the bubbles coalesce forming a gas pocket which adheres to a wide portion of the channel wall. Tests are performed on a multiphase pump laboratory, recently installed at the Norwegian University of Science and Technology, which allows a complete optical access to the pump channels and fine adjustments in the inlet configuration and the tip clearance gap; the air can be injected from different locations producing transient regimes too. A high speed camera provides an interesting insight into the transient flow phenomena. This paper focuses on these specific ones: - Irregular backflow and swirl at the inlet section - Gas accumulation zones and contribution of the tip leakage to mixing - Flow pattern shift to phase segregation, as the relative flow is reduced - Origin of pump blockage, when increasing gas contents cannot be carried away by the water phase - Flow and machine parameters response to a variation in the inlet flow Tests are performed at various operating conditions — rotational speed, mixture composition and impeller tip clearance. The study is completed with the time and frequency domain analysis of the pressure pulsations at surging and during specific transient events.

Pressure fluctuation on casing wall and investigation to tip leakage flow of contra-rotating small hydro-turbine

2021 ◽  
pp. 095765092110527
Author(s):  
Ding Nan ◽  
Toru Shigemitsu ◽  
Tomofumi Ikebuchi ◽  
Takeru Ishiguro ◽  
Takuji Hosotani
Keyword(s):  
Pressure Fluctuation ◽  
Rotation Frequency ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Lower Efficiency ◽  
Tip Leakage Vortex ◽  
New Model ◽  
Tip Leakage ◽  
Hydro Turbine

Renewable energy is strongly recommended to replace the traditional fossil fuels to solve the severe environmental pollution. However, small hydro-turbine performs lower efficiency, and it is also easy to be blocked and impacted. Therefore, the contra-rotating rotors are adopted to overcome the disadvantages of small hydro-turbine. The performance and internal flow condition of contra-rotating small hydro-turbine have been clarified. In this paper, a new transparent casing is manufactured, and pressure fluctuation experiments are conducted. The pressure fluctuation experiments are to clarify the pressure fluctuation during the running of contra-rotating small hydro-turbine. Then the hydraulic stability of contra-rotating small hydro-turbine can be further investigated. According to the experiment results, for the new model, most of the amplitudes of pressure fluctuation are decreased. The maximum decreasing percentage of peak-to-peak value is 74.22%, and it is appeared on the point of Pr3. On frequency domain, the dominant frequencies of pressure fluctuation are rotation frequency and blade passing frequency. The investigation to tip leakage flow of contra-rotating small hydro-turbine is conducted based on the pressure fluctuation experiment and numerical simulation. The tip leakage vortex is identified by Q-criterion. The pressure distributions in tip clearance area show that the tip leakage vortex of new model is suppressed, and this helps to reduce the amplitude of pressure fluctuation in tip clearance area.

scholarly journals Energy performance and flow characteristics of a multiphase pump with different tip clearance sizes

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882335 ◽  
Author(s):  
Jinsong Zhang ◽  
Honggang Fan ◽  
Wei Zhang ◽  
Zhifeng Xie
Keyword(s):  
Volume Fraction ◽  
Flow Characteristics ◽  
Energy Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Great Success ◽  
Tip Leakage Flow ◽  
Multiphase Pump ◽  
Gas Volume Fraction ◽  
Gas Volume

Deep sea oil resources worldwide possess great potential for exploration; however, multiphase medium technology requires urgent development. The multiphase pump has achieved great success as one of the most advanced machinery in underwater oil and gas exploration. Tip clearance is inevitable between the rotating and stationary components of the multiphase pump. In this study, tip clearance sizes of 0.0, 0.2, 0.5, and 0.8 mm are selected to investigate the effect of tip clearance on energy performance and flow characteristics of a multiphase pump. Results show that pressure rises decrease by 10.72%, 24.96%, and 41.39% with gas volume fraction = 0% under different tip clearance sizes, while the pressure rises decrease by 17.10%, 25.35%, and 38.11% with gas volume fraction = 10%. The dominant frequencies and maximum amplitudes of pressure fluctuation rise with the increase in tip clearance. The entrainment effect between the tip leakage flow and main flow in the impeller strengthens with the increase in tip clearance size; the induced vortex area and leakage flow rate also increase.

scholarly journals Experimental Investigation on Transient Pressure Characteristics in a Helico-Axial Multiphase Pump

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 461 ◽  
Author(s):  
Yun Xu ◽  
Shuliang Cao ◽  
Takeshi Sano ◽  
Tokiya Wakai ◽  
Martino Reclari
Keyword(s):  
Pressure Fluctuation ◽  
High Speed ◽  
Oil And Gas ◽  
High Efficiency ◽  
Phase Distribution ◽  
Pressure Rise ◽  
Stable Operation ◽  
Transient Pressure ◽  
Multiphase Pump ◽  
Pressure Characteristics

In oil and gas exploitation, the multiphase pump is a vital piece of equipment to guarantee production with high efficiency and stable operation. The complicated pattern of multiphase flow in the multiphase pump affects the pump performance; for this reason, the multiphase performance and the inner flow should be sufficiently investigated. In the present work, a liquid-gas multiphase pump is designed and manufactured, and then tested in a specialized test rig to reveal the transient pressure characteristics of the multiphase pump. Results show that the dominant frequency under water and water-air conditions is the blade passing frequency, which is induced by the rotor stator interaction. In the downstream of the impeller, the pressure fluctuation is obviously weakened, because the splitter-blade design could improve the control ability of flow pattern in the downstream region. In comparison with water condition, the pressure fluctuation of water-air condition greatly increases, and the multiples of impeller rotating frequency are stimulated due to the movement and merging of air bubbles. Finally, the correlation of transient pressure and phase distribution in impeller is revealed by using a high-speed camera. With the gradual pressure rise from impeller inlet to outlet, the relative movement and separation of two phases induce violent pressure fluctuations.

Effect of tip clearance on gas phase distribution of a gas-liquid two-phase pump

2021 ◽  
Author(s):  
Peng Wang ◽  
Hang Xie ◽  
Xingqi Luo ◽  
Runan Mo ◽  
Jinling Lu ◽  
...  
Keyword(s):  
Gas Phase ◽  
Phase Distribution ◽  
Tip Clearance ◽  
Two Phase

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

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