Number Of Pump Stages Research Articles

Experimental assessment of the impact of number of stages on vertical axis multi-stage centrifugal PATs

The pursuit of Best Management Practices (BMPs) for pressurized water systems has intensified interest in Pumps As Turbines (PATs), given that PAT use enables coupling of pressure regulation with small-scale hydropower generation. Installing PATs instead of micro-turbines provides for several advantages, such as cheaper procurement and maintenance costs, and importantly, the ability to select the most reliable model from among a wide variety of devices available in the market. Nevertheless, the current state of knowledge regarding PAT performance leaves out critical aspects that remain to be adequately addressed, especially for some models, such as centrifugal vertical axis multi-stage pumps running in reverse mode, despite such devices having attractive features that offer particularly advantageous benefits when high head in the system is exploitable.In contributing key experimental findings on four vertical multi-stage (single-, two-, three-, and four-stage) PATs, this paper thus extends the performance related knowledge about vertical multi-stage PATs: prior models from the literature are demonstrated to reliably predict performance, with the contribution additionally consisting in assessing performance dependence on number of pump stages. The results showed both head and power to be highly correlated with the variable number of stages, especially for predicting PAT characteristics at the Best Efficiency Point (BEP) for multi-stage models. However, the single-stage model exhibited slightly lower performance values.

A 115× Conversion-Ratio Thermoelectric Energy-Harvesting Battery Charger for the Internet of Things

This article presents a high-conversion-ratio (HCR), high-voltage-tolerant (HVT) energy-harvesting battery charger using 0.18-μm standard CMOS for Internet of Things (IoT). To reduce conversion ratio (CR) of inductive power converter and optimize overall power efficiency, the proposed charger cascades a boost converter and reconfigurable charge pump. Different from the high-voltage device, the standard CMOS process has lower parasitic capacitance and on-resistance; therefore, it can reduce switching and conduction loss. The reconfigurable charge pump dynamically changes the number of pumping stages according to the output voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</sub> ) by automatic configuration selector (ACS). To manage the limited power from a thermoelectric generator (TEG), the converter works under the discontinuous conduction mode (DCM). The zero-current detector (ZCD) employs an analog comparator with digital offset compensator and digital comparator to control off-time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ) quickly and accurately. The self-idle constant on-time (SI-COT) and idle mode both control the mechanism, helping to further reduce static power dissipation. As a result, the proposed converter can achieve peak efficiency of up to 76% at a 92× conversion ratio with output power ranging from 10 μW to 1.9 mW. The available input voltage ranges are 40 to 400 mV, and the dual output voltage ranges are 1 to 1.6 V and 2 to 4.6 V for V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BOOST</sub> and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</sub> , respectively.

Gas Effect in Electrical-Submersible-Pump-System Stage-by-Stage Analysis

Summary One of the main problems regarding the use of the artificial-lift method of electrical-submersible-pump (ESP) systems is the presence of gas in the pump. This paper presents and describes an analysis of ESP systems with a stage-by-stage calculation to determine intake and discharge pressures to adjust total dynamic head (TDH) for each stage of the pump. The modeling was designed to acknowledge free gas in the pump, and iterative calculations are applied to recalculate, for each stage, fluid characteristics and physical properties, such as viscosity, density, formation volume factor (FVF), surface tension, solubility ratio, gas/oil ratio (GOR), and other flow characteristics along the tubing, such as temperature and pressure. Developed modeling validation was achieved by comparisons in two scenarios. In the first one, fixed values of intake pressure and changeable values of GOR were used to assess gas effect. In the tests for the second scenario, fixed values of GOR and changeable values of intake pressure were used. Necessary research was conducted through a developed computational tool used to size ESP components. The results were different from those obtained with the usual calculations, and it may be implied that the developed modeling is more accurate to determine parameters related to this artificial-lift method. Also, the results were more consistent and closer to the actual behavior of multiphase-flow phenomena within the tubing because each stage has its characteristics individually evaluated. These observations may have an effect on the number of pump stages and influence in choosing the adequate equipment of the system.

Design of Multistage Pumping Main

Long-distance pipelines transporting fluids against gravity and frictional resistance involve multistage pumping. Equations for the optimal diameter and the pumping head for a single-stage pumping main are available. However, in the case of multistage pumping, the optimal number of pumping stages are worked out by an enumeration process. Such a process does not indicate functional dependence of input parameters on the design variables. In this paper, the multistage pumping main design is formulated as a geometric programming problem having a single degree of difficulty. The constant friction factor case of the problem yielded a closed-form solution for a long pipeline with relatively flat topography. The variation of the friction factor with diameter has been accounted for iteratively.

Accommodation Pumping—A New Principle for Low Pressures

A new principle of vacuum pumping, termed accommodation pumping, has been tested experimentally. Two volumes at room temperature are joined by a passage, the walls of which are alternately atomically rough and atomically smooth. When alternate smooth-rough junctions are held at a temperature other than room temperature, a pumping action develops and gas is transferred from one volume to the other. Experimental parameters studied are: time, location of temperature transition, pressure, number of pumping stages, nature of gas, nature of surfaces, effect of preadsorbed layers, and temperatures. A simple theory is given which yields first order agreement with pumping performance.