Reformulation of the pressure-time method for application without flow rate cut-off

One of the basic flow rate measurement methods applied in hydropower plants and recommended by the International Standard IEC 60041–1999 and American National Standard ASME PTC 18–2002 is the pressure-time method, generally known as Gibson method. The method consists in determining the flow rate (discharge) by integration of the recorded time course of pressure difference variations between two cross sections of the hydropower plant penstock. The accuracy of measurement depends on numerous factors and, according to the International Standard, generally is confined within the range 1.5–2.3%. Following the classical approach, the pressure-time method applicability is limited to straight cylindrical pipelines with constant diameters. However, the International Standard does not exclude application of this method to more complex geometries, i.e., curved pipeline (with elbows). It is obvious that a curved pipeline causes deformation of the uniform velocity field in pipeline cross sections, which subsequently causes aggravation of the accuracy of the pressure-time method flow rate measurement results. The influence of a curved penstock application on flow rate measurements by means of the considered method is discussed in this paper. The special calculation procedure for the problem solution has been developed. The procedure is based on the FLUENT computational fluid dynamic solver. Computations have been carried out in order to find the so-called equivalent value of the geometric pipe factor F required when using the pressure-time method. An example of application of this method to a complex geometry (two elbows in a penstock) is presented. The systematic uncertainty caused by neglecting the effect of the elbows on velocity field deformation has been estimated.

Download Full-text

Uncertainty analysis of liquid flow rate measurement with the pressure-time method

Measurement ◽

10.1016/j.measurement.2021.109866 ◽

2021 ◽

pp. 109866

Author(s):

Adam Adamkowski ◽

Waldemar Janicki ◽

Mariusz Lewandowski ◽

Edson da Costa Bortoni

Keyword(s):

Uncertainty Analysis ◽

Flow Rate ◽

Liquid Flow ◽

Liquid Flow Rate ◽

Rate Measurement ◽

Flow Rate Measurement ◽

Pressure Time

Download Full-text

Measurement of the Flow in a 170 MW Hydraulic Turbine Recording the Pressure-Time Rise in One Section of the Penstock

Volume 2: Fora ◽

10.1115/fedsm2006-98529 ◽

2006 ◽

Cited By ~ 1

Author(s):

F. Sierra ◽

J. Kubiak ◽

G. Urquiza ◽

A. Adamkoski ◽

W. Janicki ◽

...

Keyword(s):

Flow Rate ◽

Flow Simulation ◽

Hydraulic Turbine ◽

Operating Conditions ◽

Measuring System ◽

Recirculation Region ◽

Flow Recirculation ◽

Pressure Time ◽

On Line ◽

Region Size

The objective of the present work is to evaluate the performance of a hydraulic turbine by means of the measurement of flow using the Gibson method based on recording pressure–time rise in one section of the penstock and relate it to the pressure in the upper reservoir to which the penstock is connected. Volumetric flow is determined by integration of the time function of a differential pressure (between the section and the inlet to the penstock). Flow measurement was possible this way because the influence of penstock inlet was negligible as far as an error of the measurement is concerned. The paper presents the results obtained with this method for the case of a 170 MW hydraulic turbine. The length of the penstock was 300 m. Previous experience and a standard IEC-41-1991 were the criteria adopted and applied. An efficient and fast acquisition system including a 16 bit card was used. The flow rate was calculated using a computer program developed and tested on several cases. The results obtained with the Gibson method were used for calibration of the on-line flow measuring system based on the Winter-Kennedy principles. This last method is used for continuous monitoring of the turbine flow rate. Having calculated the flow rate and output power the efficiency is calculated for any operating conditions. A curve showing the best operating conditions based on the highest efficiency is presented and discussed. Flow simulation allowed having an estimation of a flow recirculation region size.

Download Full-text

Flow rate measurements in hydropower plants using the pressure-time method – Experiences and improvements

Flow Measurement and Instrumentation ◽

10.1016/j.flowmeasinst.2019.101584 ◽

2019 ◽

Vol 68 ◽

pp. 101584 ◽

Cited By ~ 1

Author(s):

Adam Adamkowski ◽

Waldemar Janicki ◽

Zbigniew Krzemianowski ◽

Mariusz Lewandowski

Keyword(s):

Flow Rate ◽

Hydropower Plants ◽

Pressure Time

Download Full-text

Numerical Investigation of the Pressure-Time Method Considering Pipe With Variable Cross Section

Journal of Fluids Engineering ◽

10.1115/1.4040718 ◽

2018 ◽

Vol 140 (10) ◽

Cited By ~ 2

Author(s):

Simindokht Saemi ◽

Mehrdad Raisee ◽

Michel J. Cervantes ◽

Ahmad Nourbakhsh

Keyword(s):

Shear Stress ◽

Cross Section ◽

Flow Rate ◽

Three Dimensional ◽

Variable Cross Section ◽

Navier Stokes ◽

Variable Cross ◽

Pressure Time ◽

Viscous Losses ◽

Contraction Angle

A common method to calculate the flow rate and consequently hydraulic efficiency in hydropower plants is the pressure-time method. In the present work, the pressure-time method is studied numerically by three-dimensional (3D) simulations and considering the change in the pipe cross section (a contraction). Four different contraction angles are selected for the investigations. The unsteady Reynolds-averaged Navier–Stokes (URANS) equations and the low-Reynolds k–ω shear stress transport (SST) turbulence model are used to simulate the turbulent flow. The flow physics in the presence of the contraction, and during the deceleration period, is studied. The flow rate is calculated considering all the losses: wall shear stress, normal stresses, and also flux of momentum in the flow. The importance of each term is evaluated showing that the flux of momentum plays a most important role in the flow rate estimation while the viscous losses term is the second important factor. To extend the viscous losses calculations applicability to real systems, the quasi-steady friction approach is employed. The results showed that considering all the losses, the increase in the contraction angle does not influence the calculated errors significantly. However, the use of the quasi-steady friction factor introduces a larger error, and the results are reliable approximately up to a contraction angle of ϴ = 10 deg. The reason imparts to the formation of a local recirculation zone upstream and inside the contraction, which appears earlier as the contraction angle increases. This feature cannot be captured by the quasi-steady friction models, which are derived based on the fully developed flow assumption.

Download Full-text

Discharge Measurements Using the Classic Gibson Method With Instrumentation Installed Inside a Pipeline

Volume 2: Fora ◽

10.1115/fedsm2008-55309 ◽

2008 ◽

Cited By ~ 1

Author(s):

Adam Adamkowski ◽

Waldemar Janicki ◽

Gustavo Urquiza ◽

Janusz Kubiak ◽

Miguel Basurto

Keyword(s):

Flow Rate ◽

Pressure Difference ◽

Pressure Transducer ◽

Dynamic Properties ◽

Differential Pressure ◽

Computer Data ◽

Discharge Measurement ◽

Differential Pressure Transducer ◽

Pressure Time ◽

Measurement Results

The Gibson method (pressure-time method) is one of the basic methods of discharge (flow rate) measurement applied in hydropower plants. Flow rate is determined by integrating the recorded variation of pressure difference between two measuring (hydrometric) sections in a pipeline (penstock). The Gibson method in its classic version consists in direct measurement of pressure difference variation between two hydrometric sections of a pipeline. Particular difficulties, related to application of the method in its various versions, arise in conditions of no access to the hydrometric sections from the outside of a pipeline. In such cases, it is necessary to install dedicated measuring instrumentation inside the pipeline. Such instrumentation has been implemented for the purpose of efficiency tests of two Francis turbines (upgraded and not upgraded) fed from a common penstock of 10 m diameter. The hydrometric sections were furnished with pressure taps connected by means of small copper tubes (impulse tubes) and hermetic manifolds to the differential pressure transducer. The transducer was installed in a hermetic housing and its electric signal was sent from the inside of the penstock to a computer data acquisition system. Using this method, the efficiency characteristics of the tested hydraulic turbines were determined. According to the authors’ knowledge, the pressure-time method has not been used in such an application so far. The method under consideration requires transmitting pressure signals from both penstock sections to the differential pressure transducer by means of impulse tubes. This raises the question on the influence exerted by dynamic properties of the connecting pipes / transducer system on the discharge measurement results. The previously developed computational method incorporating dynamic models of the piping and the transducer has been applied in order to determine this influence. In result of calculations conducted, the piezometric tubes / transducer system has been found to exert a negligible influence on the discharge measurement results.

Download Full-text

Determination of the transfer function between the injected flow-rate and high-pressure time histories for improved control of common rail diesel engines

International Journal of Engine Research ◽

10.1177/1468087416647238 ◽

2016 ◽

Vol 18 (3) ◽

pp. 212-225 ◽

Cited By ~ 6

Author(s):

Alessandro Ferrari ◽

Emanuele Salvo

Keyword(s):

Transfer Function ◽

Working Conditions ◽

Flow Rate ◽

Diesel Engines ◽

Time History ◽

Common Rail ◽

Rail Pressure ◽

Experimental Estimation ◽

Pressure Time ◽

Time Histories

Theoretical and experimental methodologies have been proposed and illustrated to determine the transfer function between the injected flow-rate and the rail pressure for common rail injection systems. An analytical transfer function has been calculated in the frequency domain, utilizing a previously developed lumped parameter model of the overall hydraulic layout of a common rail system. The predicted transfer function has been compared, in a Bode diagram, with an experimental estimation of the transfer function, based on the measured rail pressure and injected flow-rate time histories that were acquired at the hydraulic rig for different working conditions. The experimental estimation of the transfer function has been worked out by applying a selective spectral technique in order to reduce the effects of measurement noise on the rail pressure and injected flow-rate time histories. The accuracy of the model-derived transfer function has been improved significantly by integrating a pressure control system sub-model, which includes the action of the electronic control unit on the rail pressure time history through the pressure regulator, in the hydraulic model of the common rail circuit. Finally, the time histories of the rail pressure, predicted by means of the complete injection apparatus model, have been compared with the corresponding experimental traces at different working conditions and a very satisfactory agreement has in general been found. The methodologies proposed for the accurate evaluation of the transfer function between the injected flow-rate and the rail pressure time histories can be applied to diesel engines in order to implement innovative closed-loop strategies for the injected mass control.

Download Full-text

A Novel Reconstitution Method for Inducing the Formation of Regular 2-Dimensional Arrays of Membrane Proteins and Lipids

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102845 ◽

1988 ◽

Vol 46 ◽

pp. 152-153 ◽

Cited By ~ 1

Author(s):

A. Engel ◽

A. Holzenburg ◽

K. Stauffer ◽

J. Rosenbusch ◽

U. Aebi

Keyword(s):

Membrane Proteins ◽

Flow Rate ◽

Lipid Membranes ◽

Functional Characterization ◽

Dimensional Structure ◽

Electron Crystallography ◽

Peltier Element ◽

Protein Ratio ◽

Precise Control ◽

3 Dimensional

Reconstitution of solubilized and purified membrane proteins in the presence of phospholipids into vesicles allows their functions to be studied by simple bulk measurements (e.g. diffusion of differently sized solutes) or by conductance measurements after transformation into planar membranes. On the other hand, reconstitution into regular protein-lipid arrays, usually forming at a specific lipid-to-protein ratio, provides the basis for determining the 3-dimensional structure of membrane proteins employing the tools of electron crystallography.To refine reconstitution conditions for reproducibly inducing formation of large and highly ordered protein-lipid membranes that are suitable for both electron crystallography and patch clamping experiments aimed at their functional characterization, we built a flow-dialysis device that allows precise control of temperature and flow-rate (Fig. 1). The flow rate is generated by a peristaltic pump and can be adjusted from 1 to 500 ml/h. The dialysis buffer is brought to a preselected temperature during its travel through a meandering path before it enters the dialysis reservoir. A Z-80 based computer controls a Peltier element allowing the temperature profile to be programmed as function of time.

Download Full-text

Novel epoxy/anhydride alternatives for biological electron microscopy: Physical and performance characteristis of embed 812 and LX 112 in combination with NSA/NMA/DMAE

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156985 ◽

1989 ◽

Vol 47 ◽

pp. 1000-1001

Author(s):

Joe A. Mascorro ◽

Gerald S. Kirby

Keyword(s):

Electron Microscopy ◽

Flow Rate ◽

Succinic Anhydride ◽

Volume Flow Rate ◽

Mass Density ◽

Uranyl Acetate ◽

Volume Flow ◽

Base Resin ◽

And Performance ◽

Acid Anhydrides

Embedding media based upon an epoxy resin of choice and the acid anhydrides dodecenyl succinic anhydride (DDSA), nadic methyl anhydride (NMA), and catalyzed by the tertiary amine 2,4,6-Tri(dimethylaminomethyl) phenol (DMP-30) are widely used in biological electron microscopy. These media possess a viscosity character that can impair tissue infiltration, particularly if original Epon 812 is utilized as the base resin. Other resins that are considerably less viscous than Epon 812 now are available as replacements. Likewise, nonenyl succinic anhydride (NSA) and dimethylaminoethanol (DMAE) are more fluid than their counterparts DDSA and DMP- 30 commonly used in earlier formulations. This work utilizes novel epoxy and anhydride combinations in order to produce embedding media with desirable flow rate and viscosity parameters that, in turn, would allow the medium to optimally infiltrate tissues. Specifically, embeding media based on EmBed 812 or LX 112 with NSA (in place of DDSA) and DMAE (replacing DMP-30), with NMA remaining constant, are formulated and offered as alternatives for routine biological work.Individual epoxy resins (Table I) or complete embedding media (Tables II-III) were tested for flow rate and viscosity. The novel media were further examined for their ability to infilftrate tissues, polymerize, sectioning and staining character, as well as strength and stability to the electron beam and column vacuum. For physical comparisons, a volume (9 ml) of either resin or media was aspirated into a capillary viscocimeter oriented vertically. The material was then allowed to flow out freely under the influence of gravity and the flow time necessary for the volume to exit was recored (Col B,C; Tables). In addition, the volume flow rate (ml flowing/second; Col D, Tables) was measured. Viscosity (n) could then be determined by using the Hagen-Poiseville relation for laminar flow, n = c.p/Q, where c = a geometric constant from an instrument calibration with water, p = mass density, and Q = volume flow rate. Mass weight and density of the materials were determined as well (Col F,G; Tables). Infiltration schedules utilized were short (1/2 hr 1:1, 3 hrs full resin), intermediate (1/2 hr 1:1, 6 hrs full resin) , or long (1/2 hr 1:1, 6 hrs full resin) in total time. Polymerization schedules ranging from 15 hrs (overnight) through 24, 36, or 48 hrs were tested. Sections demonstrating gold interference colors were collected on unsupported 200- 300 mesh grids and stained sequentially with uranyl acetate and lead citrate.

Download Full-text