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

2008 ◽  
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.

In-phase rejection requirements for measuring respiratory input impedance

1984 ◽  
Vol 56 (3) ◽  
pp. 804-809 ◽  
Author(s):  
R. Peslin ◽  
P. Jardin ◽  
C. Duvivier ◽  
P. Begin
Keyword(s):  
Pressure Difference ◽  
Input Impedance ◽  
Pressure Transducer ◽  
Absolute Pressure ◽  
Impedance Measurements ◽  
Differential Pressure Transducer ◽  
Rejection Ratio ◽  
Respiratory Flow ◽  
In Series ◽  
The Subject

Respiratory flow is commonly obtained by measuring the pressure difference across a pneumotachograph. When respiratory input impedance is studied, that pressure difference may be very small with respect to the absolute pressure swings inside the pneumotachograph. Then the in-phase rejection of the differential pressure transducer is expected to markedly influence the accuracy of the data. The problem was investigated by computer simulation and by measurements on a mechanical analog of the respiratory system made of a resistance, an inertance, and a compliance arranged in series. Both studies demonstrated that comparatively small differences in the volumes of the chambers or in the lengths or diameters of the connecting tubes led to artifactual frequency dependence of resistance and serious misestimation of compliance and inertance. Errors were larger when the resistance of the pneumotachograph was smaller and the impedance of the subject larger. In practice, with usual pneumotachographs accurate impedance measurements require using the most symmetrical transducers presently available (common-mode rejection ratio of about 70 dB at 30 Hz).

Pressure Measurements Around a Rotating Cylinder With and Without Crossflow

1993 ◽  
Vol 115 (3) ◽  
pp. 526-528 ◽  
Author(s):  
A. A. Tawfek ◽  
B. V. S. S. S. Prasad ◽  
A. K. Mohanty
Keyword(s):  
Pressure Transducer ◽  
Static Pressure ◽  
Rotating Cylinder ◽  
Differential Pressure ◽  
Pressure Measurements ◽  
Orthogonal Axis ◽  
Differential Pressure Transducer ◽  
Slip Ring

Static pressure measurements around a cylinder rotating about an orthogonal axis with and without superimposed crossflow are carried out by using a capacitance type differential pressure transducer in conjunction with a slip-ring apparatus. A coefficient of pressure (Cp) is defined for the rotating cylinder and typical variations of Cp along its length and periphery are presented.

Sign in / Sign up

Export Citation Format

Share Document