Pump Characteristic Curves Research Articles

An MILP approach for detailed scheduling of multi-product pipeline in pressure control mode

Scheduling with hydraulic constraints is one of the crucial aspects to guarantee multi-product pipeline safety. This paper develops a discrete-time mixed-integer linear programming (MILP) model for a single-source multi-product pipeline in pressure control mode, minimizing the pump cost as well as the labor cost of pump stoppage/restart. Instead of limiting pressure through flowrate constraints, this paper adopts piecewise linear approximation to deal with pump characteristic curves and frictional loss associated to flowrate and establish corresponding pressure constraints. The pressure at all key points along the pipeline should be within the allowable range to ensure transport safety. In this way, the proposed model can attain the integrated optimization of the pipeline scheduling and pump scheduling, thereby avoiding the possible mismatch between pressure and flowrate obtained by two-step solving strategy. Finally, the proposed method is compared with another discrete-time MILP model (Chen et al., 2017) which sets the minimum pump rate variation as objective function for the operating economy. Two cases tested on a Chinese real-world pipeline are given to demonstrate that the optimal detailed schedules obtained by the proposed model perform better in both economy and the convenience of pump operations.

Centrifugal Pump Monitoring and Determination of Pump Characteristic Curves Using Experimental and Analytical Solutions

Centrifugal pumps are widely used in the industry, especially in the oil and gas sector for fluids transport. Classically, these are designed to transfer single phase fluids (e.g., water) at high flow rates and relatively low pressures when compared with other pump types. As part of their constructive feature, centrifugal pumps rely on seals to prevent air entrapment into the rotor during its normal operation. Although this is a constructive feature, water should pass through the pump inlet even when the inlet manifold is damaged. Modern pumps are integrated in pumping units which consist of a drive (normally electric motor), a transmission (when needed), an electronic package (for monitoring and control), and the pump itself. The unit also has intake and outlet manifolds equipped with valves. Modern systems also include electronic components to measure and monitor pump working parameters such as pressure, temperature, etc. Equipment monitoring devices (vibration sensors, microphones) are installed on modern pumping units to help users evaluate the state of the machinery and detect deviations from the normal working condition. This paper addresses the influence of air-water two-phase mixture on the characteristic curve of a centrifugal pump; pump vibration in operation at various flow rates under these conditions; the possibilities of using the results of experimental investigations in the numerical simulations for design and training purposes, and the possibility of using vibration and sound analysis to detect changes in the equipment working condition. Conclusions show that vibration analysis provides accurate information about the pump’s functional state and the pumping process. Moreover, the acoustic emission also enables the evaluation of the pump status, but needs further improvements to better capture and isolate the usable sounds from the environment.

A precision pump schedule optimization for the water supply networks with small buffers

The study addresses the problem of finding an energy-efficient pump and valve configuration of a water supply network. It is motivated particularly by scantily buffered networks which require both method precision and algorithm efficiency that tightly chase notably dynamic water demand. The model unprecedentedly comprehends physical and hydraulic laws that govern pump-valve configuration along with ensuing flow and energy level. The solution method combines hydraulic relaxation of individual pump characteristic curves to a station curve and an LP-based search performing optimal trade-off between water head and discharge beyond the minimum energy level for each station. With a hamming-distance-type shortest path formulation incorporated into the search steps, it can also minimize both frequency and magnitude of pump-valve reconfiguration. The proposed method achieved an energy-cost saving of 5.9% and did so more consistently than manual operation, while retaining computation time suitable for unit period as short as 15 min.

Semi-empirical model of a multi-diaphragm pump in an Organic Rankine Cycle (ORC) experimental unit

Organic Rankine Cycle (ORC) power systems represent an effective option to exploit low grade heat fluxes. Several papers have been published on ORCs systems, most of them dealing with the maximization of overall system performance and selection of the working fluid. Recently, the attention has moved also to system components with specific focus on the expander. Less attention was paid to the pump which, however, may contribute significantly to the system consumption, especially in small size systems.This paper presents a semi-empirical thermodynamic model of a displacement pump integrated into an ORC experimental unit. The pump behavior at design and off-design conditions is modeled as a set of thermodynamic processes the main geometrical parameters of which are calibrated using experimental data. Calibration is performed by setting an optimization procedure which minimizes the error between operation parameters calculated by the model and measured in the test rig. Maximum errors were in the range 0.06%–7%. Differently from the few papers on similar models in the literature, this model takes into account the trapped mass flow rate, and is used to calculate the pump characteristic curves and identify incipient cavitation. A good agreement with experimental data was found in both cases.

Experimental verification of a virtual water flowmeter applicable to air conditioning systems

The main purpose of this research is to suggest a virtual water flowmeter applicable in hydraulic systems with low-cost sensors. Practical procedures for realizing virtual water flowmeters for constant flow pumps (i.e., Cases 1 and 2) and variable flow pumps (i.e., Cases 3 and 4) are proposed in this paper. In Case 1, for measuring the water flow rate through a constant flow pump, the pump head was measured and the water flow rate was estimated using the pump characteristic curve obtained from the manufacturer or by deriving an empirical model based on the field measurement data. In Case 2, the water flow rate through a valve with a constant flow pump was estimated by measuring the pressure head between the valve and the valve opening position. The valve characteristic curve can be obtained by deriving an empirical model based on the initial field test results. The water flow rate through the variable flow pump was calculated, using the pump affinity laws and an empirical model, by measuring the frequency (i.e., Case 3) or input power (i.e., Case 4). The initial setup and test procedures for virtual flowmeters are also proposed in this research for practical use in the field. To verify the proposed procedures, experiments were conducted using constant and variable flow pumps in a pilot system. It was found that the virtual water flowmeters showed 2.9% to 6.7% of root mean square error from Case 1 to Case 4, compared with an ultrasonic water flowmeter, through long-term experimental verification.

The effect of wear ring clearance on flow field in the impeller sidewall gap and efficiency of a low specific speed centrifugal pump

In this paper, the flow in the impeller sidewall gap of a low specific speed centrifugal pump is analyzed to study the effect of wear ring clearance and the resultant through-flow on flow field in this cavity and investigate the overall efficiency of the pump. Centrifugal pumps are commonly subject to a reduction in the flow rate and volumetric efficiency due to abrasive liquids or working conditions, since the wear rings are progressively worn, the internal leakage flow is increased. In the new operating point, the overall efficiency of the pump cannot be predicted simply by using the pump characteristic curves. The flow field is simulated with the use of computational fluid dynamics and the three-dimensional full Navier–Stokes equations are solved using CFX software. In order to verify the numerical simulations, static pressure field in volute casing and pump performance curves are compared with the experimental measurements. The results show that, for the pump with minimum wear ring clearance, the disk friction efficiency is the strongest factor that impairs the overall efficiency. Therefore, when the ring clearance is enlarged more than three times, although volumetric efficiency decreases effectively but the reduction in overall efficiency is remarkably smaller due to improvement in the disk friction losses.

Sensitivity analysis and optimal operation control for large-scale waterflooding pipeline network of oilfield

Waterflooding development is one of the most common methods in oilfields. The energy consumption of waterflooding system accounts for a large proportion of the total in oilfield development. Therefore, the optimization of waterflooding system is able to further decrease operation cost and enhance development efficiency. But it is complicated to optimize operation control of large-scale waterflooding pipeline networks as a result of lots of wells and complex waterflooding pipeline networks. Although previous scholars have done much research, few have considered technical constraints of waterflooding networks. This paper puts forward a quantitative evaluation approach to pressure and flowrate sensitivity of waterflooding pipeline networks firstly, and concludes that the pressure and flowrate sensitivity are related to network topological structures, pipeline parameters and current operation flowrates. Meanwhile, an operation optimization approach to large-scale oilfield waterflooding system based on mixed integer linear programming (MILP) is proposed, which considers pump characteristic curves, adopts Hazen–William formula to simulate hydraulic pressure drop of pipe segments and deals with nonlinear items by phased linearization method. With the demand flowrate, the optimal pumping scheme of waterflooding station, pumping flowrate and throttling pressure of each well can be efficiently worked out. Finally, this approach is successfully applied to a virtual waterflooding system with 15 wells and a large-scale real one with 82 wells in China. Results show that the model has better practicality for the operation control optimization of waterflooding pipeline networks with larger scale and stronger sensitivity.

Transient behavior of a centrifugal pump during starting period

A theoretical analysis on transient flow inside a centrifugal pump was carried out, building on unsteady and incompressible fluid equations applied to the impeller during the starting periods. The transient flow behavior is governed by two hyperbolic partial differential equations; namely continuity and motion equations. The characteristics method of the specified time intervals was used to analyze the dynamic characteristic of the pump. To follow the dynamic behavior of the pump during startup periods, a numerical study was performed on the pump impeller with different openings of the discharge valve. The comparison between the numerical and experimental results of the pump characteristic curve has shown a good concordance. The results have also revealed that the pressure increase is important in the case of a short starting period of the pump and a large mass of water in the pipelines. In this study, the effect of the impeller diameter and number of blades on the pressure evolution was also analyzed.

Research on Capacity Modulation Mechanisms of Variable Composition Heat Pump

In order to solve the contradiction of building heat pump characteristic curve of demand and supply of heat pump, put forward by changing concentration of mixture refrigerant capacity regulation to increase heat production purposes. The capacity control is analyzed, and verified by theoretical calculation and experiment. The results show that, the heat pump system can be obtained by changing concentration of mixture refrigerant to achieve the purpose of regulating capacity.

The influence of SiO2 nanoparticles on cavitation initiation and intensity in a centrifugal water pump

The main objective of this paper is to examine the effect of SiO2 nanoparticles on cavitation initiation in a centrifugal water pump. A backward-curved blade centrifugal pump with a nominal head and flow rate of 2.4m and 12l/min has been used. Furthermore, 7nm SiO2 particles are added to deionized water in order to prepare the nanofluid with 0.1%, 0.4%, and 0.7% (ml SiO2/ml H2O) concentrations. The tests are also performed at three different temperatures (10°C, 25°C and 40°C) to investigate the cavitation initiation and its intensity through the blade passages of the pump. The key parameters of this research are: (a) SiO2 nanoparticles concentration and (b) fluid temperature. Cavitation initiation through the blade passages is identified using two different methods: (a) visually observing the population of bubbles in the flow with a high speed camera and (b) pump characteristic curves analysis. Results show that SiO2 nanoparticles can effectively postpone cavitation initiation and notably decrease the cavitation growth rate. Moreover, it has been found that the bubble growth is reduced when increasing the nanoparticles concentration and this is more pronounced at higher temperatures.

Discussion of “Effective Approach for Solving Battle of Water Calibration Network Problem” by Zheng Yi Wu and Thomas M. Walski

Discussion of “Effective Approach for Solving Battle of Water Calibration Network Problem” by Zheng Yi Wu and Thomas M. Walski

Correcting for heavy oil viscosity

Pump characteristic curves generally refer to water. An appropriate correction procedure is thus required when a medium of much higher viscosity is to be handled. This article tests the validity of the Hydraulic Institute's formula method for correcting pump performance by applying it to real data from a Chinese oil pipeline.

Optimal Design of Pumping Mains Considering Pump Characteristics

AbstractThe total cost of a pumped water supply system includes the capital costs of the pipeline and pumping units, the replacement costs of various components included, and the energy costs related to the system’s operation. The capital cost of pipeline and energy cost are nonlinear functions of the pipe diameter. In addition, the pump characteristics, the replacement costs of components, and the escalating energy costs are of a nonlinear nature. In this paper, a nonlinear optimization model is developed to design a pumping main for required discharge, static head, pump characteristics, and economic parameters. The optimization model minimizes the total annual cost of the pumping main and pump, satisfying the pump characteristic curve equations. The applicability of the developed model is demonstrated with the help of a design example. The optimization model determines the optimal diameter of pumping main with pump efficiency for a required discharge or optimal discharge range with pump efficiency for a...

Filling dynamics and phase change of molten salt in cold receiver pipe during initial pumping process

The filling dynamics and phase change performances of molten salt in cold receiver pipe during initial pumping process are numerically analyzed with variable inlet velocity due to pump characteristic curve. In general, cold receiver pipe during initial pumping process will be frozen for molten salt solidification as the inlet temperature is lower than critical temperature, or else it will be unobstructed with melting process at higher inlet temperature. During pumping process with melting, the flow velocity will first decrease by solidification and then increase by melting effect, and the melting time decreases with inlet temperature. As the freezing phenomena appears during pumping process, the flow velocity will decrease to zero, while the pressure loss reaches the maximum pressure head, and the freezing time increases with inlet temperature. Since a solid layer exists adjacent to the pipe wall in phase change region, the flow velocity and pressure loss remarkably increases along flow direction, and the phase change region will dominate the pressure loss. As the inlet temperature decreases, the phase change region remarkably enlarges, and the filling time rises.

Working Condition Diagnostics System for Electrical Submersible Pump in Geothermal Well

The situation of the global energy is tending to be in short supply, but geotherm is the inexhaustible renewable energy. Extracting reservoir geothermal water from old oil well can achieve economic benefits of oil - heat joint production. Since 2005, Huabei oilfield has been engaging in geothermal comprehensive utilization research projects and developed the large displacement electrical submersible pumps suitable for high temperature. For the operation management of this equipment, the working condition diagnosis analysis research has been carried out, 16 kinds of current curve template and 73 kinds of pump characteristic curve template have been established using ADO remote data access technology, and the volume efficiency and energy efficiency dynamic control model and chart have been established as well. The production situation analysis using the chart can timely find out the problems existing in the production and puts forward the improvement measures to achieve the purpose of energy saving and consumption reduction.

Energy Cost Optimization in a Water Supply System Case Study

The majority of the life cycle costs (LCC) of a pump are related to the energy spent in pumping, with the rest being related to the purchase and maintenance of the equipment. Any optimizations in the energy efficiency of the pumps result in a considerable reduction of the total operational cost. The Fátima water supply system in Portugal was analyzed in order to minimize its operational energy costs. Different pump characteristic curves were analyzed and modeled in order to achieve the most efficient operation point. To determine the best daily pumping operational scheduling pattern, genetic algorithm (GA) optimization embedded in the modeling software was considered in contrast with a manual override (MO) approach. The main goal was to determine which pumps and what daily scheduling allowed the best economical solution. At the end of the analysis it was possible to reduce the original daily energy costs by 43.7%. This was achieved by introducing more appropriate pumps and by intelligent programming of their operation. Given the heuristic nature of GAs, different approaches were employed and the most common errors were pinpointed, whereby this investigation can be used as a reference for similar future developments.

Optimal plant operation of brackish water reverse osmosis (BWRO) desalination

Optimal plant operation of brackish water reverse osmosis (BWRO) desalination is studied in this work to reduce specific energy consumption (SEC). A comprehensive first-principles based mathematical model, which explicitly accounts for membrane area and hydraulic permeability, pump characteristic curves, and pressure drops along the RO train, is developed and validated by plant data. A constrained nonlinear optimization is formulated and solved for two RO trains with different service times. It is shown that a 16% reduction in SEC is possible by optimizing operating conditions within the normal operating range of the pump while maintaining the same permeate rate. Results are discussed using dimensionless parameters derived in the author's previous work. Suggestions are made to further reduce SEC in BWRO plant operation.

Technical Note: An Analytical Method for Evaluating Pumps for a Storage-Pump System

Runoff can be captured and stored for a wide variety of uses; the practice is known as rainwater harvesting (RWH). Storage-pump systems are an efficient means of collecting runoff, storing it for later use, and pumping it to satisfy demand when needed in a RWH system. Evaluating pumps for storage-pump systems can be complex for two reasons. First, there are nonlinearities in the friction factor equation, which is needed to calculate head loss in the system. This head loss is used in both the demand curve and suction head relationship. Second, quickly assessing the pump characteristic curves is difficult because they are typically provided in non-digital form. This article compares various approximate explicit methods to a more exact, implicit solution for the friction factor. The system demand curve is calculated with both, and the relative error for a selected RWH example is provided. A tracing program is used to digitize a pump characteristic curve selected for this example. The Serghides (1984) method was selected due to a low relative error and is recommended for wide use in calculation of similarly configured systems. The reader can adapt this method by modifying this example to quickly assess the pumping and demand characteristics of their design.

Validation of an Axial Flow Blood Pump: Computational Fluid Dynamics Results Using Particle Image Velocimetry

A magnetically suspended axial flow blood pump is studied experimentally in this article. The pump casing enclosed a three-blade straightener, a two-blade impeller shrouded by a permanent magnet-embedded cylinder, and a three-blade diffuser. The internal flow fields were simulated earlier using computational fluid dynamics (CFD), and the pump characteristic curves were determined. The simulation results showed that the internal flow field was basically streamlined, except the diffuser region. Particle image velocimetry (PIV) measurement of the 1:1 pump model was conducted to validate the CFD result. In order to ensure the optical access, an acrylic prototype was fabricated with the impeller driven by a servomotor instead, as the magnet is opaque. In addition to the transparent model, the blood analog fluid with the refractive index close to that of acrylic was used to avoid refraction. According to the CFD results, the axial flow blood pump could generate adequate pressure head at the rotating speed of 9500rpm and flow rate of 5L/min, and the same flow condition was applied during the PIV measurement. Through the comparisons, it was found that the experimental results were close to those obtained by CFD and had thus validated the CFD model, which could complement the limitation of the measurement in assessing the more detailed flow fields of the axial flow pump.

Investigation on complete characteristics and hydraulic transient of centrifugal pump

An improved method was developed to obtain the complete characteristic of centrifugal pump. The conversion formula of complete characteristics is established based on the normal performance curve. An example was presented to illuminate the new method, and the complete characteristic curves of 14SA-10 centrifugal pump were obtained by the new method. The hydraulic transient of the centrifugal pump failure and start-up was simulated by method of characteristics (MOC), which quote the complete characteristics data. The results show that the inversion method is available to obtain the complete pump characteristic curves provided the normal performance curve. For hydraulic transient simulation, more accurate numerical result can be obtained, if the new model is adopted to convert the experimental normal performance curve to complete characteristics curve of centrifugal pump.