Performance Enhancement by Dynamic Valve Timing of a Multistage Vacuum Micropump

2010 ◽  
Author(s):  
Karthik Kumar ◽  
Luis P. Bernal ◽  
Khalil Najafi
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Pressure Difference ◽  
Performance Enhancement ◽  
High Vacuum ◽  
Operating Pressure ◽  
Transient Operation ◽  
Valve Timing ◽  
Steady State Operation ◽  
Valve Leakage

This paper presents the results of a theoretical analysis of dynamic valve timing on the performance of a multistage peristaltic vacuum micropump. Prior work has shown that for optimum steady state performance a fixed valve timing which depends on the operating pressure can be found. However, the use of a fixed valve timing could hinder performance for transient operation when the pump is evacuating a fixed volume. At the beginning of the transient the pump operates at low pressure difference and a large flow rate would be desirable. As the pump reaches high vacuum the pressure difference is large and the flow rate is necessarily small. Astle and coworkers1–3 have shown using a reduced order model that for steady state operation short valve open time results in lower inlet pressure and flow-rate and conversely. Here we extend the model of Astle and coworkers to include transient operation, multiple coupled stages and non-ideal leaky valves, and show that dynamic valve timing (DVT) reduces the transient duration by 30% compared to high vacuum pressure valve timing. The results also show a significant reduction in resonant frequency of the pump at low pressures, and quantify the effect of valve leakage.

scholarly journals Vehicular Quality Biomethane Production from Biogas by Using an Automated Water Scrubbing System

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
R. Chandra ◽  
V. K. Vijay ◽  
P. M. V. Subbarao
Keyword(s):  
Steady State ◽  
Control Systems ◽  
Flow Rate ◽  
Packed Bed ◽  
Operating Pressure ◽  
Absorption Column ◽  
Automatic Control Systems ◽  
Steady State Operation ◽  
Biomethane Production ◽  
Column Pressure

This paper presents the results of an automated water scrubbing system used for enrichment of methane content in the biogas, to produce vehicular grade biomethane fuel. Incorporation of automatic control systems for precisely regulating the water level and maintaining constant operating pressure in the packed bed absorption column of water scrubbing system resulted in steady-state operation of the scrubbing system and a consistent supply of methane-enriched biogas from the gas outlet. The improved automated water scrubbing system was found to enrich 97% methane at an operating column pressure of 1.0 MPa with 2.5 m3/h biogas in-flow rate and 2.0 m3/h water in-flow rate into the scrubbing column unit.

scholarly journals Determination of Permeability and Inertial Coefficients of Sintered Metal Porous Media Using an Isothermal Chamber

2018 ◽  
Vol 8 (9) ◽  
pp. 1670 ◽  
Author(s):  
Wei Zhong ◽  
Xiang Ji ◽  
Chong Li ◽  
Jiwen Fang ◽  
Fanghua Liu
Keyword(s):  
Porous Media ◽  
Steady State ◽  
Flow Rate ◽  
Pressure Difference ◽  
Testing Time ◽  
Sintered Metal ◽  
Steady State Method ◽  
Volume Limit ◽  
Inertial Coefficient

Sintered metal porous media are widely used in a broad range of industrial equipment. Generally, the flow properties in porous media are represented by an incompressible Darcy‒Forchheimer regime. This study uses a modified Forchheimer equation to represent the flow rate characteristics, which are then experimentally and theoretically investigated using a few samples of sintered metal porous media. The traditional steady-state method has a long testing time and considerable air consumption. With this in mind, a discharge method based on an isothermal chamber filled with copper wires is proposed to simultaneously determine the permeability and inertial coefficient. The flow rate discharged from the isothermal chamber is calculated by differentiating the measured pressure, and a paired dataset of pressure difference and flow rate is available. The theoretical representations of pressure difference versus flow rate show good agreement with the steady-state results. Finally, the volume limit of the isothermal chamber is addressed to ensure sufficient accuracy.

scholarly journals A LABORATORY SYSTEM FOR INVESTIGATING OF FLUIDS FLOW CAPACITY THROUGH UNCONSOLIDATED SAND SAMPLES

2020 ◽  
Vol 17 (36) ◽  
pp. 634-645
Author(s):  
Izzat Niazi SULAIMAN ◽  
Yahya Jirjees TAWFEEQ
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Steady State ◽  
Relative Permeability ◽  
Flow Rate ◽  
Pressure Difference ◽  
Absolute Permeability ◽  
Sand Sample ◽  
Flow Capacity ◽  
State Process

Practically all studies of reservoir engineering involve detailed knowledge of fluid flow characteristics. The fluid flow performance in porous media is affected by pressure, flow rate, and volume of single fluid phases. Permeability is a measure of how well a porous media allows the flow of fluids through it. Permeability and porosity form the two significant characteristics of reservoir rocks. This research aimed to present the design of laboratory equipment to test the ability of fluid flow through different sandstone samples. Two sand core samples (coarse sand sample and fine sand sample) were tested. The laboratory findings measurements of porosity, saturation, total permeability, effective permeability, and relative permeability were evaluated. The laboratory tests were performed on partially saturated, unconsolidated core sand for two-phase fluid flow. The experimental work was developed for measuring the flow capacity achieved under the steady-state conditions method. Various grain sizes sands were selected as a porous medium to determine petrophysical properties and fluid flow capacity of the rock sample. Nitrogen and air were utilized as gas-phases, and, for liquid-phases, water was chosen as an injection fluid. The steady-state process method was used to determine the permeability and relative permeability of unconsolidated sands to water flow. Different flow rates were measured for different pressure gradients in a viscose flow. As the flow rate increases, the pressure difference also increased. It can be observed that there are a direct correlation and relationship between the flow rate and the pressure difference. The core plug's absolute permeability was measured using Darcy Equation. Absolute permeability does not depend on fluid characteristics but only on media properties. The sample container contains a more significant amount of sand, decrease the permeability, and therefore requires high pressure for fluid flowing within the sample.

Work With Chemical Additives Advances Understanding of Relative Permeability Shifts

2021 ◽  
Vol 73 (09) ◽  
pp. 37-38
Author(s):  
Chris Carpenter
Keyword(s):  
Steady State ◽  
Relative Permeability ◽  
Flow Rate ◽  
Pressure Difference ◽  
Effective Permeability ◽  
Constant Flow ◽  
Chemical Additives ◽  
Flow Rates ◽  
Steady State Method ◽  
Tight Rocks

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201520, “Advances in Understanding Relative Permeability Shifts by Imbibition of Surfactant Solutions Into Tight Plugs,” by Mohammad Yousefi, Lin Yuan, and Hassan Dehghanpour, SPE, University of Alberta, prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 5–7 October. The paper has not been peer reviewed. Various chemical additives have been proposed recently to enhance imbibition oil recovery from tight formations during shut-in periods after hydraulic fracturing operations. In the complete paper, the authors develop and apply a laboratory protocol mimicking leakoff, shut-in, and flowback processes to evaluate the effects of fracturing-fluid additives on oil regained permeability. A conventional coreflooding apparatus is modified to measure oil effective permeability (koeff) before and after the surfactant-imbibition experiments. Methodology Proposed Technique for Measuring Oil Effective Permeability. Despite the simplicity of the steady-state method, measuring permeability of tight rocks with this technique is challenging because of its time-consuming nature and the fact that accurate measurement is necessary of extremely low flow rates corresponding to low injectivity of tight rocks. The authors use a pair of plugs from a well drilled in the Montney formation that is a stratigraphic unit of the Lower Triassic age in the western Canadian sedimentary basin located in British Columbia and Alberta. It is mainly a low-permeability siltstone reservoir. In the modified coreflooding apparatus, the authors reduce the effect of compressibility in order to reduce the duration of the transient period by approximately one order of magnitude. Because monitoring changes in pressure is much easier and more accurate than monitoring flow-rate changes, a constant flow-rate mode is used and pressure is recorded with time. Oil is injected at different constant flow rates (qo), and the inlet pressure is monitored. The stable pressure difference across the plug is recorded for each flow rate. After steady-state conditions are reached based on the pressure profile, the qo is increased. This process is repeated until four stable pressure differences corresponding to four different qo are obtained. After the highest qo is reached, it is decreased in similar steps to check the repeatability of each data point. The permeability is calculated with the Darcy equation and slope of the qo vs. stable pressure difference across the plug.

Detection of Cavitation in a Venturi Injector With a Combined Method of Strain Gauges and Numerical Simulation

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Yuncheng Xu ◽  
Yan Chen ◽  
Jianqiang He ◽  
Haijun Yan
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Strain Gauges ◽  
Maximum Pressure ◽  
Operating Pressure ◽  
Average Growth ◽  
Rate Of Increase ◽  
Suction Flow

The fertilizer suction capability of a Venturi injector is dependent on the vacuum pressure in the throat portion. As the vacuum level drops below the saturation vapor pressure, the pressure decreases to a particular value corresponding to the maximum pressure difference (Δpmax) between inlet and outlet pressures, and critical cavitation is likely to occur, leading to an unstable suction flow rate and low fertilization uniformity. A new method of using strain gauges to detect cavitation in Venturi injectors was explored experimentally and verified numerically under various operating conditions. The standard deviation (SD) of the measured strain values and the simulated values of the vapor-phase volume fraction (Vf) were used to evaluate the influence of cavitation. The results showed that both the rate of increase (ηm) of the average SD and the average growth rate (AGR) of the simulated cavitation length reach relatively large values at the maximum pressure difference (Δpmax), where the measured suction flow rate simultaneously reaches a maximum. In addition, SD and Vf shared similar variation trends at pressure differences larger than the corresponding Δpmax under various conditions. This new cavitation detection method has been proved to be feasible and reliable. It helps to determine accurately the value of Δpmax at different inlet pressures and to ensure that the Venturi injector runs in a safe operating-pressure range.

Regenerator Effectiveness During Transient Operation

1996 ◽  
Vol 118 (3) ◽  
pp. 661-667
Author(s):  
D. S. Beck
Keyword(s):  
Heat Capacity ◽  
Steady State ◽  
Gas Turbines ◽  
Transient Operation ◽  
Operating Cycle ◽  
High Effectiveness ◽  
Engine Efficiency ◽  
Time Period ◽  
Steady State Operation ◽  
Long Time

Current designs of regenerative gas turbines include high-effectiveness rotary regenerators. The regenerators make the gas turbines highly efficient during steady-state operation. During engine transients, however, engine efficiency can be low because high-effectiveness regenerators tend to have large cores with large thermal masses, and it can take a long time (minutes for example) for these regenerators to reach their steady-state effectivenesses. The following criterion determines the response time of regenerators: τss˜(mc)R/Cx, where τxx (S) is the time period of transient operation; (mc)R (J/K) is the heat capacity of the core; and Cx (W/K) is the heat-capacity rate of the exhaust. This criterion has been verified through analysis and experimentation. The criterion enables the designer to estimate the fraction of an operating cycle during which the regenerator will have reduced effectiveness.

Centrifugal Pump Performance During Transient Operation

1995 ◽  
Vol 117 (1) ◽  
pp. 123-128 ◽  
Author(s):  
P. J. Lefebvre ◽  
W. P. Barker
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Rotational Speed ◽  
Hydrodynamic Performance ◽  
Test Facility ◽  
Transient Operation ◽  
Transient Effects ◽  
Pump Impeller ◽  
Simultaneous Control ◽  
Steady State Operation

The effect of transient operation on the hydrodynamic performance of a centrifugal pump impeller was investigated experimentally. All experiments were conducted in the Naval Undersea Warfare Center’s Impeller Test Facility (ITF), which was designed and built for transient and steady-state operation impeller research. The ITF provides transient operation through simultaneous control of both impeller rotational speed and flow rate over time. The impeller was accelerated from rest with peak angular accelerations up to 720 radians/s2 and inlet flow mean accelerations up to 1.7 g, reaching a peak rotational speed of 2400 rpm and a flow rate of 416 l/s. The impeller was then decelerated to rest. Results showed substantial transient effects in overall impeller performance and demonstrated that the quasisteady assumptions commonly used for the design of impellers that operate under high transient (accelerating or decelerating) conditions are not valid.

Experimental and Modelling of Aqueous Radioactive Waste Treatment by Ultrafiltration

2018 ◽  
Vol 69 (5) ◽  
pp. 1149-1151
Author(s):  
Laura Ruxandra Zicman ◽  
Elena Neacsu ◽  
Felicia Nicoleta Dragolici ◽  
Catalin Ciobanu ◽  
Gheorghe Dogaru ◽  
...  
Keyword(s):  
Flow Rate ◽  
Suspended Solids ◽  
Waste Treatment ◽  
Operating Pressure ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Independent Variables ◽  
Opposite Trend ◽  
Process Factors ◽  
Volumetric Flux

Ultrafiltration of untreated and pretreated aqueous radioactive wastes was conducted using a spiral-wound polysulphonamide membrane. The influence of process factors on its performances was experimental studied and predicted. Permeate volumetric flux and permeate total suspended solids (TSS) were measured at different values of feed flow rate (7 and 10 m3/h), operating pressure (0.1-0.4 MPa), and feed TSS (15 and 60 mg/L). Permeate flux (42-200 L/(m2�h)) increased with feed flow rate and operating pressure as well as it decreased with an increase in feed TSS, whereas permeate TSS (0.1-33.2 mg/L) exhibited an opposite trend. A 23 factorial plan was used to establish correlations between dependent and independent variables of ultrafiltration process.

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