Complete Pump Characteristics Research Articles

A New Prediction Method for the Complete Characteristic Curves of Centrifugal Pumps

Complete pump characteristics (CPCs) are the key for establishing pump boundary conditions and simulating hydraulic transients. However, they are not normally available from manufacturers, making pump station design difficult to carry out. To solve this issue, a novel method considering the inherent operating characteristics of the centrifugal pump is therefore proposed to predict the CPCs. First, depending on the Euler equations and the velocity triangles at the pump impeller, a mathematical model describing the complete characteristics of a centrifugal pump is deduced. Then, based on multiple measured CPCs, the nonlinear functional relationship between the characteristic parameters of the characteristic operating points (COPs) and the specific speed is established. Finally, by combining the mathematical model with the nonlinear relationship, the CPCs for a given specific speed are successfully predicted. A case study shows that the predicted CPCs are basically consistent with the measured data, showing a high prediction accuracy. For a pump-failure water hammer, the simulated results using the predicted CPCs are close to that using the measured data with a small deviation. This method is easy to program and the prediction accuracy meets the requirements for hydraulic transient simulations, providing important data support for engineering design.

Complete and homologous pump characteristics for a reactor coolant pump

A reactor coolant pump is subjected to various abnormal operating modes, so the pump supplier has to provide all the transient pump characteristics to a user. Complete or homologous pump characteristics are the best forms including transient hydraulic information for an abnormally operating pump. Until now, there has been no consideration in the systematic test procedures to obtain the complete or homologous pump characteristics through a hydraulic test. No further research has been done on the relationships among the constant heads in complete pump characteristics. Likewise, no additional discussion has taken place on the direct transformation of the homologous pump characteristics into the complete pump characteristics. In present paper, a mathematical model is introduced to explain how the constant head curves in the complete pump domain are connected to each other. This means that other constant head curves can be obtained without additional hydraulic testing once a constant head curve is obtained for the full flow rate and speed range. It is also shown that the complete pump characteristics can be obtained from the homologous pump characteristics by another mathematical model. For homologous pump characteristics, even though differently enveloped test matrices that consist of different level sets of flow rate and speed are applied in hydraulic testing, the same homologous pump characteristics are obtained. These results indicate that a low-enveloped test matrix is sufficient to obtain the homologous pump characteristics.

Numerical and Experimental Investigation of the 4-Quadrant Behavior of Different Mixed Flow Diffuser Pumps

Besides operating a centrifugal pump under normal conditions there are additional operating conditions possible; for example, a pump operated as turbine. Another example would be a pump trip where there are several abnormal operating conditions possible when the direction of flow and/or the direction of rotation are changing. The machine behavior in every possible operation condition can be represented by the complete pump characteristics, often called the 4-quadrant (4Q) behavior of a centrifugal pump. To gather the 4Q behavior, a test rig allowing the flow direction as well as the rotation direction to be reverted is necessary, with time-consuming measurements at variable positive and negative discharge in both directions of rotation the complete pump characteristics are evaluated. In the present study, an approach to investigate the complete pump characteristics by means of computational fluid dynamics (CFD) calculations is presented. With steady-state calculations and additional transient CFD investigations in the normal operating conditions, the whole pump characteristics were calculated accurately. Two different types of mixed flow diffuser pumps were investigated—one equipped with adjustable impeller blades, the second one with comparable low specific speed. Experimental verifications have shown a remarkably good agreement. Furthermore, an exemplary numerical waterhammer analysis shows the successful application of the presented approach.

Investigation of the 4-Quadrant behaviour of a mixed flow diffuser pump with CFD-methods and test rig evaluation

The complete pump characteristics including its 4-quadrant behaviour are of essential interest for off-design operations such as a pump trip. At this exceptional load case the pump enters the dissipation mode and moves further into the turbine mode while the direction of rotation and the flow direction will change. The time-consuming and expensive experimental investigation of the 4-quadrant behaviour requires a specific test rig, allowing the flow direction as well as the rotational direction of the investigated pump to be reverted. By measuring the pump performance (head and efficiency) at variable positive and negative discharge and rotation the complete pump characteristics are evaluated. Nowadays CFD- analysis allows for the reliable prediction of the hydraulic performance of a pump near the design point. However, abnormal operating conditions lead to complex and unsteady flow phenomena inside the pump. Besides steady-state calculations in the normal operating conditions quite comprehensive transient CFD-investigations are required to simulate the whole pump characteristics accurately. The present study focuses on the comparison of the results obtained on the test rig and by numerical methods and shows a remarkably good agreement between them. It can be shown that it is possible to reliably simulate the 4-quadrant behaviour of a mixed flow diffuser pump based on CFD-methods. Furthermore an exemplary waterhammer calculation shows the successful application of the numerically calculated 4- quadrant behaviour.

Evaluation of centrifugal pump performance in nuclear power plants

A systematic approach is developed for prediction of performance of single, as well as double-entry, centrifugal pumps in a specific speed range of 600 to 2500 engineering units. Complete pump characteristics can be mapped, from shut-off conditions to 130% of the design flowrate. Given the dimensions of a centrifugal pump, as well as the impeller rotational speed, the method can be employed in prediction of head vs flowrate ( H- Q), shaft power vs flowrate (BHP- Q) and efficiency vs flowrate ( E- Q) curves. Pump characteristics can then be used to model pump performance in state-space. This allows for development of optimal control strategies, for design of controllers. and for examination of the sensitivity of operation to changes in design and performance parameters. Hence, optimization of process design and operation becomes attainable. Application of the method to a nuclear-grade coolant pump demonstrated the viability of the model as a tool in simulation of pump response to various inputs. State-space representation is shown to be invaluable in simulation of performance at normal and abnormal operation conditions, synthesis of surveillance schemes and in detection of abnormalities caused by degradation of the components.

Charts for water hammer in high head pump discharge lines resulting from pump failure and check valve closure

Maximum pressure head drops and rises resulting from pump failure and subsequent check valve closure are calculated and plotted for a simple pump discharge line at pump end, midpoint, and three-quarter point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, and pump inertia constant are accounted for in the analyses. Computer studies indicate that pipe friction, pipeline constant, and pump inertia have a major effect on pressure head drops and rises.Studies indicate further that whereas for large pump inertia the pressure head rise or drop at the midpoint is only moderately larger than one-half of the rise or drop at pump end, for small pump inertia this difference is much greater. For very small pump inertia, the pressure head drop or rise at midpoint approaches the values at pump end. This increase in pressure head drop and rise for very small pump inertia is even more pronounced at the three-quarter point.

Charts for water hammer in low head pump discharge lines resulting from water column separation and check valve closure

Maximum pressure head rises resulting from water column separation and check valve closure are calculated and plotted for a simple low head pump discharge line with one well-defined high point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, pump inertia constant, and the relative location of the high point are accounted for in the analyses. The results of this paper can be used to determine (a) when water column separation is expected, (b) how to avoid water column separation, and (c) the necessary wall thickness in cases where no protection against water column separation is provided. Computer studies indicate that both the vertical and horizontal location of the high point as well as the pipe friction, the pipeline constant, and the pump inertia have a major effect on pressure head rises. Water column separation does not always constitute a danger to the pipeline. Key words: waterhammer, water column separation, check valve closure, pressure rise, pump discharge line, chart.

Water-Hammer Charts for Centrifugal Pump Systems

Water-hammer analysis of centrifugal pumping systems following power stoppage can be greatly simplified and expedited with the use of generalized charts. Charts are presented for determining the time of flow reversal at the pump, the minimum and maximum heads at the pump and at the mid-length of the discharge line, and the maximum head at the pump if reverse rotation is prevented. The graphs are applicable to pumps with specific speeds less than approximately 2,700 (rpm-gpm-ft). Pump efficiency and line friction are included in the charts. An examination of the complete characteristics of centrifugal pumps is presented and a set of complete pump characteristics for use in water-hammer analysis is developed. The effects of pump specific speed on the transient following power stoppage are examined.

Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients

This paper presents complete pump characteristics of specific speeds 1800, 7600, and 13,500 (gpm units) in the ν – hP (flow ratio-head ratio) co-ordinate system. The method of developing these complete pump characteristics from test data is described. The three complete pump characteristics are compared, and the effects of specific speed on hydraulic transients caused by power failure or pump shutoff is presented.

Discussion: “Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients” (Donsky, Benjamin, 1961, ASME J. Basic Eng., 83, pp. 685–696)

Discussion: “Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients” (Donsky, Benjamin, 1961, ASME J. Basic Eng., 83, pp. 685–696)

Discussion: “Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients” (Donsky, Benjamin, 1961, ASME J. Basic Eng., 83, pp. 685–696)

Discussion: “Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients” (Donsky, Benjamin, 1961, ASME J. Basic Eng., 83, pp. 685–696)

Closure to “Discussions of ‘Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients’” (1961, ASME J. Basic Eng., 83, pp. 697–698)

Closure to “Discussions of ‘Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients’” (1961, ASME J. Basic Eng., 83, pp. 697–698)