Experimental and Numerical Studies of Pump Transient Characteristics During Stopping Period

2014 ◽  
Author(s):  
Peng Wu ◽  
Dazhuan Wu ◽  
Leqin Wang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Rotational Speed ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Hydrodynamic Characteristics ◽  
Rotational Inertia ◽  
Operating Characteristics ◽  
Transient Characteristics ◽  
Numerical Studies

Experimental and numerical studies were carried out to study the transient characteristics of the centrifugal pump during stopping periods. Different stopping schemes were realized by changing the rotational inertia of the flywheels. Transient revolution rotational speed, flow-rate, total pressure rise and torque were measured under different rotational inertia. Experimental results of different operating conditions were compared, and transient hydrodynamics performances of the centrifugal pump model were analyzed. In order to provide boundary conditions for numerical simulations, the revolution curves of the flow-rate and the rotational speed were polynomial fitted. Three dimensional unsteady incompressible viscous flows during stopping periods were studied by using DES model in FLUENT. Results show that the hydrodynamic characteristics of numeric and experiment agree well. The transient effect is not so evident, and the quasi-steady assumption is acceptable during most part of coastdown process. The pump characteristics are further explained by analyzing the relative velocity on the middle stream surfaces. At the end of the stopping period, the transient vortex evolution between blades is the main reason why the transient curves deviates the steady curve. The studies can help understand the operating characteristics of centrifugal pump when power failure accident occurs.

Transient Characteristics of a Closed-Loop Pipe System During Pump Stopping Periods

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Dazhuan Wu ◽  
Peng Wu ◽  
Shuai Yang ◽  
Leqin Wang
Keyword(s):  
Kinetic Energy ◽  
Flow Rate ◽  
Rotational Speed ◽  
Closed Loop ◽  
Transient Flow ◽  
Operating Conditions ◽  
Rotational Inertia ◽  
Transient Characteristics ◽  
Pipe System ◽  
The Impact

In order to study the transient characteristics of a closed-loop pipe system with room temperature water, experiments were carried out based on different pump stopping periods from rate rotational speed to zero. Various stopping periods were realized by changing the rotational inertia of the rotors, controlling the frequency of the motor and braking the shaft. Experimental results of different operating schemes were compared, and transient flow rate of the pipe system and transient characteristics of the pump were analyzed. The influences of the kinetic energy of the loop fluid and pump rotors to the stopping periods were summarized. Results show that rapid change of the pump operating conditions occurs during the stopping period and transient flow rate of the pipe system and characteristics of the pump depend largely on the way of stopping. The kinetic energy stored in the pump can drive the impeller keeping rotating for more time after the motor is shutdown. Due to the kinetic energy stored in the loop pipe, the flow rate does not reach zero immediately after the rotational speed reaches zero. The inertia of pump rotor and fluid inertia affect the impact of fluid flow and the duration of the loop during pump stopping period.

The Response of a Centrifugal Pump to Fluctuating Rotational Speed

1995 ◽  
Vol 117 (3) ◽  
pp. 479-484 ◽  
Author(s):  
H. Tsukamoto ◽  
H. Yoneda ◽  
K. Sagara
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Total Pressure ◽  
Flow Analysis ◽  
Pressure Rise ◽  
Singularity Method ◽  
Measured Flow ◽  
Unsteady Characteristics

A theoretical and experimental study has been made on the dynamic characteristics of a centrifugal pump subject to sinusoidal changes in rotational speed. Time-dependent rotational speed, flow-rate, and total pressure rise are measured for a variety of amplitude and frequency of the fluctuating rotational speed. Measured flow-rate as well as total pressure rise is compared with the quasi-steady ones. Unsteady flow analysis is made for a two-dimensional circular cascade by use of the singularity method. The calculated frequency characteristics are compared with the corresponding experimental ones. The deviation of unsteady characteristics from quasi-steady ones is evident, and the numerical results agree qualitatively with the measured ones. It was found that with the increased frequency of rotational speed fluctuations the dynamic characteristics deviate remarkably from quasi-steady ones. Moreover, a criterion for the assumption of quasi-steady change is presented.

Reduced-Order Modelling of Rotating Stall

2020 ◽  
Author(s):  
Dominik Schlüter ◽  
Robert P. Grewe ◽  
Fabian Wartzek ◽  
Alexander Liefke ◽  
Jan Werner ◽  
...  
Keyword(s):  
Single Cell ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Stability Limit ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Transonic Compressor ◽  
Experimental Findings

Abstract Rotating stall is a non-axisymmetric disturbance in axial compressors arising at operating conditions beyond the stability limit of a stage. Although well-known, its driving mechanisms determining the number of stall cells and their rotational speed are still marginally understood. Numerical studies applying full-wheel 3D unsteady RANS calculations require weeks per operating point. This paper quantifies the capability of a more feasible quasi-2D approach to reproduce 3D rotating stall and related sensitivities. The first part of the paper deals with the validation of a numerical baseline the simplified model is compared to in detail. Therefore, 3D computations of a state-of-the-art transonic compressor are conducted. At steady conditions the single-passage RANS CFD matches the experimental results within an error of 1% in total pressure ratio and mass flow rate. At stalled conditions, the full-wheel URANS computation shows the same spiketype disturbance as the experiment. However, the CFD underpredicts the stalling point by approximately 7% in mass flow rate. In deep stall, the computational model correctly forecasts a single-cell rotating stall. The stall cell differs by approximately 21% in rotational speed and 18% in circumferential size from the experimental findings. As the 3D model reflects the compressor behaviour sufficiently accurate, it is considered valid for physical investigations. In the second part of the paper, the validated baseline is reduced in radial direction to a quasi-2D domain only resembling the compressor tip area. Four model variations regarding span-wise location and extent are numerically investigated. As the most promising model matches the 3D flow conditions in the rotor tip region, it correctly yields a single-cell rotating stall. The cell differs by only 7% in circumferential size from the 3D results. Due to the impeded radial migration in the quasi-2D slice, however, the cell exhibits an increased axial extent. It is assumed, that the axial expansion into the adjacent rows causes the difference in cell speed by approximately 24%. Further validation of the reduced model against experimental findings reveals, that it correctly reflects the sensitivity of circumferential cell size to flow coefficient and individual cell speed to compressor shaft speed. As the approach reduced the wall clock time by 92%, it can be used to increase the physical understanding of rotating stall at much lower costs.

Influences of Impeller Diameter and Diffuser Blades on Air-Water Two-Phase Flow Performance of Centrifugal Pump

2005 ◽  
Author(s):  
Naoki Matsushita ◽  
Akinori Furukawa ◽  
Kusuo Okuma ◽  
Satoshi Watanabe
Keyword(s):  
Centrifugal Pump ◽  
Water Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Flow Condition ◽  
High Performance ◽  
Two Phase Flow ◽  
Water Flow Rate ◽  
Phase Flow ◽  
Two Phase

A tandem arrangement of double rotating cascades and single diffuser cascade, proposed as a centrifugal pump with high performance in air-water two-phase flow condition, yields lower head due to the smallness of the impeller outlet in comparison with a impeller with large outlet diameter and no diffuser. Influences of impeller diameter change and installation of diffuser blades on two-phase flow performance were experimentally investigated under the case of the same volute casing. As the result, the similarity law of the diameter of impeller having the similar blade geometry and the rotational speed is satisfied even in two-phase flow condition. Comparing pump performances between a large impeller without diffuser blades and a small one with diffuser blades, higher two-phase flow performance is obtained by controlling the rotational speed of a small impeller with diffuser blades in the range of small water flow rates, while a large impeller with no diffuser gives high performance in the range of high water flow rate and small air flow rate.

Performance and Development of a Miniature Rotary Shaft Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 752-760 ◽  
Author(s):  
Danny Blanchard ◽  
Phil Ligrani ◽  
Bruce Gale
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Electronics Cooling ◽  
Maximum Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Hydraulic Efficiency ◽  
Potential Applications ◽  
Total Analysis ◽  
And Performance

The development and performance of a novel miniature pump called the rotary shaft pump (RSP) is described. The impeller is made by boring a 1.168 mm hole in one end of a 2.38 mm dia shaft and cutting slots in the side of the shaft at the bottom of the bored hole such that the metal between the slots defines the impeller blades. The impeller blades and slots are 0.38 mm tall. Several impeller designs are tested over a range of operating conditions. Pump performance characteristics, including pressure rise, hydraulic efficiency, slip factor, and flow rate, are presented for several different pump configurations, with maximum flow rate and pressure rise of 64.9ml∕min and 2.1 kPa, respectively, when the working fluid is water. Potential applications include transport of biomedical fluids, drug delivery, total analysis systems, and electronics cooling.

Experimental Investigation of Oil Flowrate in a Hermetic Reciprocating Compressor

2014 ◽  
Author(s):  
Sibel Tas ◽  
Sertac Cadirci ◽  
Hasan Gunes ◽  
Kemal Sarioglu ◽  
Husnu Kerpicci
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
High Speed ◽  
Operating Conditions ◽  
Lubricating Oil ◽  
Reciprocating Compressor ◽  
Oil Flow ◽  
Oil Flow Visualization

The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.

scholarly journals Experimental Study of a Cavitating Centrifugal Pump During Fast Startups

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
O. Roussette ◽  
G. Bois ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Transient Flow ◽  
Flow Behavior ◽  
Rocket Engine ◽  
Rotation Velocity ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Physical Analysis ◽  
Different Types

The startup of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations, which may result in partial flow vaporization, i.e., cavitation. An existing experimental test rig has been updated in the LML Laboratory (Lille, France) for the startups of a centrifugal pump. The study focuses on the cavitation induced during the pump startup. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast startup behaviors have been identified. According to the final operating point, the startup is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed in both the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior.

Performance Evaluation of a Turbine Used in a Regenerative Organic Rankine Cycle

2012 ◽  
Author(s):  
Maoqing Li ◽  
Jiangfeng Wang ◽  
Lin Gao ◽  
Xiaoqiang Niu ◽  
Yiping Dai
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Low Grade ◽  
Low Grade Heat

Due to environmental constraints, the Organic Rankine Cycle (ORC) is widely used to generate electricity from low grade heat sources. In ORC processes, the working fluid is an organic substance, which has a better thermodynamic performance than water for low grade heat recovery. The design of the turbine which is the key component in the ORC system strongly depends on the operating conditions and on the scale of the facility. This paper presents an experimental study on a prototype of an axial-flow turbine integrated into a regenerative ORC system with R123 as working fluid. The power output is 10kW scale, and the single-stage turbine is selected. The turbine is specially designed and manufactured, and a generator is connected to the turbine directly. In the experiment, the turbine is tested under different inlet pressure conditions (0.6–1.5MPa), different inlet temperature conditions (80–150°C) and different flow rate conditions. The experimental data such as the pressures, temperatures of the turbine inlet and outlet, flow rate, rotational speed, and electrical power generation are analyzed to find their inner relationships. During the test, the turbine rotational speed could reach more than 3010 r/min, while the design rotational speed is 3000 r/min. The isentropic efficiency of the turbine could reach 53%. The maximum electrical power generated by the turbine-generator is 6.57KW. From the test data the peak value of the temperature difference between the inlet and the outlet of the turbine is 53 °C, and the expansion ratio reaches about 11. The computational fluid dynamics (CFD) solvers is also used to analyze the performance of the turbine. The distributions of the pressure, Mach number, and static entropy in the turbine flow passage component are examined and the reasons are also obtained. This study reveals the relationships between the performance of the axial-flow turbine and its inlet and outlet vapor conditions. The experiment results and the CFD results lay a foundation for using this type turbine in the ORC systems which product electrical power from a few KW to MW.

Numerical Investigation of Transient Flow in a Prototype Centrifugal Pump during Startup Period

2017 ◽  
Vol 34 (2) ◽  
Author(s):  
Yu-Liang Zhang ◽  
Zu-Chao Zhu ◽  
Hua-Shu Dou ◽  
Bao-Ling Cui ◽  
Yi Li ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Transient Flow ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Transient Performance ◽  
Pipe System ◽  
Incompressible Viscous Flow ◽  
Rotor Stator Interaction ◽  
Startup Period

AbstractTransient performance of pumps during transient operating periods, such as startup and stopping, has drawn more and more attentions recently due to the growing engineering needs. During the startup period of a pump, the performance parameters such as the flow rate and head would vary significantly in a broad range. Therefore, it is very difficult to accurately specify the unsteady boundary conditions for a pump alone to solve the transient flow in the absence of experimental results. The closed-loop pipe system including a centrifugal pump is built to accomplish the self-coupling calculation. The three-dimensional unsteady incompressible viscous flow inside the passage of the pump during startup period is numerically simulated using the dynamic mesh method. Simulation results show that there are tiny fluctuations in the flow rate even under stable operating conditions and this can be attributed to influence of the rotor–stator interaction. At the very beginning of the startup, the rising speed of the flow rate is lower than that of the rotational speed. It is also found that it is not suitable to predict the transient performance of pumps using the calculation method of quasi-steady flow, especially at the earlier period of the startup.

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