scholarly journals Analysis of Unsteady Flow Characteristics of Centrifugal Pump under Part Load Based on DDES Turbulence Model

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tang Xin ◽  
Liu Zhili ◽  
Zhao Meng ◽  
Yang Haotian ◽  
Jiang Wei ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Radial Velocity ◽  
Centrifugal Pump ◽  
Turbulence Model ◽  
Vortex Structure ◽  
Guide Vane ◽  
Load Condition ◽  
Wake Flow ◽  
Part Load ◽  
Load Conditions

To better reveal the mechanism of the rotor-stator interference between the impeller and the guide vane and the evolution process of the stall vortex under the part-load conditions, numerical simulation is carried out based on the DDES turbulence model, which can better capture vortex structure. And the pressure pulsation and the radial velocity distribution of the centrifugal pump are studied. The vortex structure and pressure fluctuation of pump internal flow field under part-load condition of Q = 0.4 Qdes are mainly analyzed. The analysis results show that the stall vortex is formed at the inlet of the impeller and evolves to the outlet of the impeller, the front cover to the rear cover according to the fluid flow direction, and then disappears. Besides, under the part-load condition, the vorticity of the impeller outlet is always obviously less than that of the impeller inlet as the flow rate increases. Due to the asymmetric action of the volute, the radial velocity distribution law of flow channel C1 is different from other flow channels at different blade heights. By analyzing the radial velocity, the phenomenon that the jet-wake flow impacts the guide vane with the rotation of the impeller is the main reason for the rotor-stator interference. And large radial velocity gradients appear at the front and rear cover plates, which will cause high energy loss and reduce pump efficiency. Besides, the conclusion can be drawn that the region with the strongest rotor-stator interference is the inlet region of the guide vane suction surface. It also occurs near the volute tongue but is lower due to the effect of the guide vane. This research may serve as a reference for the safe operation of centrifugal pumps under part-load conditions.

A Study of Cavitation Flow in a Centrifugal Pump at Part Load Conditions Based on Numerical Analysis

2012 ◽  
Author(s):  
Jianping Yuan ◽  
Yanxia Fu ◽  
Shouqi Yuan
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Inlet Pipe ◽  
Part Load ◽  
Cavitation Inception ◽  
Wide Range ◽  
Load Conditions

In order to predict cavitation performance of the centrifugal pump, including cavitating structures and vapour volume at the blade suction side, as well as its relationship with the backflow in the impeller eye, a 3D numerical simulation of detailed steady and unsteady cavitating flow was applied to reproduce its inner flow fields at part load conditions (0.5Qd and 0.4Qd). The comparisons of cavitation characteristics of the current centrifugal pump at an on-design point (1.0Qd) and a high flow rate (1.2Qd) were achieved as well. In addition, Frequency analysis of pressure fluctuations at the blade passages and the inlet pipe were also obtained during cavitation for a flow coefficient of 50%. The results further show that successive blade cavitation patterns and the creeping cavitation number dropping appear for a wide range of flow rates when the inlet total pressure decreases from cavitation inception to the breakdown of the centrifugal pump, as is quite different from that when cavitation occurs at 1.0Qd or 1.2Qd. Unbalanced attached cavities on the blade suction side were also observed at 0.5Qd. Meanwhile, the unsteady behaviour of cavities attached to the blade suction side and cavitation number dropping depend on the flow rate and cavitation number. Another significant characteristic of the phenomenon is that all the domain frequencies in blade passages and inlet pipe at part load conditions are 0.048Hz∼48.285Hz, which is typically lower than the shaft rotational frequency of the model centrifugal pump.

Multi-Cycle Simulation of the Mixture Formation Process of an High Performance Engine at Part Load Condition

2012 ◽  
Author(s):  
Claudio Forte ◽  
Gian Marco Bianchi ◽  
Enrico Corti ◽  
Stefano Fantoni
Keyword(s):  
High Performance ◽  
Load Condition ◽  
Experimental Tests ◽  
Fuel Mixture ◽  
Critical Issue ◽  
Transient Condition ◽  
Mixture Formation ◽  
Part Load ◽  
Cycle Simulation ◽  
Load Conditions

Transient operation of engines leads to air fuel (A/F) ratio excursions, which can increase engine emissions. These excursions have been attributed to the formation of fuel films in the intake port, which are caused by a portion of the intake fuel impinging and adhering on the relatively cool port surface. These films act as a source or sink which cause the AF variations depending upon the transient condition. Gaining a fundamental understanding of the nature and quantity of such films may assist in future fuel mixture preparation designs that could aid in emission reductions, yet would not require overly expensive nor complicated systems. The control of air to fuel ratio is a critical issue for high performance engines: due to the low stroke-to-bore ratio the maximum power is reached at very high regimes, letting little time to the fuel to evaporate and mix with air. The injector located upstream the throttle causes a lot of fuel to impinge the throttle and intake duct walls, slowing the dynamics of mixture formation in part load conditions. The aim of this work is to present a CFD methodology for the evaluation of mixture formation dynamics applied to a Ducati high performance engine under part load conditions. The phenomena involved in the process are highly heterogeneous, and particular care must be taken to the choice of CFD models and their validation. In the present work all the main models involved in the simulations are validated against experimental tests available in the literature, selected based on the similarity of physical conditions of those of the engine configuration under analysis. The multi-cycle simulation methodology here presented reveals to be a useful tool for the evaluation of the mixture dynamics and for the evaluation of injection wall film compensator models.

A Computer Program for Simulating Transient Behavior in Steam Turbine Stage Pressure of AHWR

2006 ◽  
Author(s):  
Anu Dutta ◽  
I. Thangamani ◽  
G. Chakraborty ◽  
A. K. Ghosh ◽  
H. S. Kushwaha
Keyword(s):  
System Analysis ◽  
Mathematical Formulation ◽  
Load Condition ◽  
Low Pressure ◽  
Research Centre ◽  
Turbine Stage ◽  
Feed System ◽  
Part Load ◽  
Desalination Plant ◽  
Load Conditions

It is proposed to couple the Advanced Heavy water reactor (AHWR), which is being developed by Bhabha Atomic Research Centre, India, with a desalination plant. The objective of this coupling is to produce system make-up and domestic water. The proposed desalination plant needs about 1.9 kg/sec of steam and the minimum pressure requirement is 3 bars. The desalination plant can be fed with bled steam extracted from a suitable stage in low pressure turbine. As the turbine stage pressure changes with the load, it is essential to know the availability of bled steam at aforesaid pressure for various load condition. The objective of the present study is to identify a suitable extraction point so as to ensure availability of steam at desired condition for desalination plant, even at part load conditions. In order to fulfill the above objective a steam and feed system analysis code was developed which incorporates the mathematical formulation of different components of the steam and feed system such as, high pressure (HP) and low pressure (LP) turbines, re-heater, feed heaters etc. The dynamic equations are solved simultaneously to obtain the stage pressure at various load conditions. Based on the results obtained, the suitable extraction stage in LP turbine was selected. This enables to determine the lowest possible part load operation up to which availability of desalination plant could be ensured.

scholarly journals Instability analysis under part-load conditions in centrifugal pump

2019 ◽  
Vol 33 (1) ◽  
pp. 269-278 ◽  
Author(s):  
Weixiang Ye ◽  
Renfang Huang ◽  
Zhiwu Jiang ◽  
Xiaojun Li ◽  
Zuchao Zhu ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Instability Analysis ◽  
Part Load ◽  
Load Conditions

scholarly journals A Turbulence Model Assessment for Deep Part Load Conditions of a Francis Turbine

2021 ◽  
Vol 774 (1) ◽  
pp. 012072
Author(s):  
J Wack ◽  
J Beck ◽  
P Conrad ◽  
F von Locquenghien ◽  
R Jester-Zürker ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Francis Turbine ◽  
Model Assessment ◽  
Deep Part ◽  
Part Load ◽  
Load Conditions

scholarly journals OPERATION OF CENTRIFUGAL PUMP AT PART LOAD CONDITIONS

2010 ◽  
Vol 33 (4) ◽  
pp. 363-375
Author(s):  
M. A. Hosien ◽  
S. M. Selim
Keyword(s):  
Centrifugal Pump ◽  
Part Load ◽  
Load Conditions

scholarly journals RANS CFD Analysis of Hump Formation Mechanism in Double-Suction Centrifugal Pump under Part Load Condition

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6815
Author(s):  
Yong Liu ◽  
Dezhong Wang ◽  
Hongjuan Ran ◽  
Rui Xu ◽  
Yu Song ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Formation Mechanism ◽  
Stokes Equations ◽  
Load Condition ◽  
Simulation Method ◽  
Energy Balance Equation ◽  
Dynamics Simulation ◽  
Hydraulic Loss ◽  
Part Load

The RANS (Reynolds-averaged Navier–Stokes equations) with CFD (Computational Fluid Dynamics) simulation method is used to analyze the head hump formation mechanism in the double-suction centrifugal pump under a part load condition. The purpose is to establish a clear connection between the head hump and the microcosmic flow field structure, and reveal the influence mechanism between them. It is found that the diffuser stall causes a change in the impeller capacity for work, and this is the most critical reason for hump formation. The change in the hydraulic loss of volute is also a reason for hump, and it is analyzed using the energy balance equation. The hump formation mechanism has not been fully revealed so far. This paper found the most critical flow structure inducing hump and revealed its inducing mechanism, and greatly promoted the understanding of hump formation. The impeller capacity for work is analyzed using torque and rotational speed directly, avoiding large error caused by the Euler head formula, greatly enhancing the accuracy of establishing the connection between the impeller capacity for work and the coherent structure in the flow field under a part load condition. When a pump is running in the hump area, a strong vibration and noise are prone to occur, endangering the pump safety and reliability, and even the pump start and the transition of different working conditions may be interrupted. Revealing the hump formation mechanism provides a key theoretical basis for suppressing hump. Hump problems are widespread in many kinds of pumps, causing a series of troubles and hazards. The analysis method in this paper also provides a reference for other pumps.

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