Abstract : This paper presents an application of ultrasonic tomography for detecting the multiphase flow through reconstruction of the cross sectional image of flow. The image is based on the distribution of ultrasonic wave velocity in the flowing medium and reconstructed from measuring the propagation time of ultrasonic wave on the transducers placed around the pipe. We measure the propagation time of ultrasonic wave traveled crossing the pipe from a transmitter to a receiver and we calculate the average velocity as the projection data for the reconstruction process. By using the filtered...
Coriolis mass flowmeters (CMF) are claimed to be not affected by the properties of the liquid such as heat conductivity, heat capacity and viscosity. They are direct mass flowmeters and form a real mean along the flow profile. However, there is some evidence from field applications that the devices, in particular with single straight pipe, suffer under the null drift. Therefore, the zero shift must be adjusted to the properties of liquid, installation site and operating conditions. The zero shift is caused by asymmetry of the oscillating system. A change in the asymmetry leads to the zero...
The volume of a cylindrical storage tank with a vertical axis changes - besides of the influence of other quantities - with the hydrostatic pressure applied by the liquid stored in the tank. The formula of M. K. Sayadi describes the influence of the liquid head on the expansion of storage tanks best having the handicap that it can be evaluated individually for each tank only by means of a numerical program because the explicit solution works only for a tank consisting of a single course. The author tried to meet two requirements: to give a formula for an explicit solution for tanks...
Cavitation is in most cases harmful and undesired phenomenon in fluid power systems. When actions for preventing cavitation are considered, it is essential to recognise the existence of cavitation and location of cavitation inception point. In fluid power components and systems cavitation can occur in various locations where the access for measuring instruments is limited. Therefore, the existence of cavitation is often very difficult to detect. In addition, very high speed of the cavitation phenomenon makes the task difficult. At the Institute of Hydraulics and Automation several cavitation...
Miniaturized flow sensors based on thin film germanium thermistors offer high flow sensitivities and short response times. The thermistors are placed on a silicon nitride diaphragm carried by a silicon frame. Using the controlled overtemperature scheme the measurable airflow velocity ranges from 0.001 m/s to 200 m/s. The response time to large step changes of the air velocity is less than 20 ms. Our experiments show that the sensor is also applicable to acoustic flow measurements.
Designing bluff-bodies for the ultrasonic vortex frequency measurement almost leads to very different geometries as they are used for the vortex detection method by pressure sensors. In some cases they have the same form but they are facing their backside to the inflow. The developing process is not only restricted by the demand for a constant Strouhal number and a strong linear dependency of the vortex frequency to the mean flow velocity but also by the vortex detection method.
The paper presents an algorithm for detection and location single parametric faults in analogue electronic circuits based on making use of input-output measurements. It utilises two circuit functions (for instance: voltage transmittance K U and input opened admittance Y in ) measured on the same frequency for the fault location. Each of circuit functions is regarded as bilinear transformation. When we put together these transformations into a three-dimensional space (for instance: Re ( K U ), Im ( K U ), | Y in |) it is wrested a family of curves representing the changes of respective...
This paper illustrates the design and the development of a thick-film mass flow sensor based on the frequency shift of a resonating ceramic structure. The mechanical oscillator realized uses a measurement principle of thermoanemometric type. The sensor can measure mass flows up to 15 × 10 4 sccm (sccm: 10 sccm = 0.17 mg/s), with high sensitivity. Here we report on the first prototype consisting of a beam 0.254 mm thick , 4 mm large and 17 mm long, in which the temperature variations induced by flow, affect the resonance frequency. Predicted and measured values for the shift of the resonance...
Installation effects can not be exhaustively analysed due to the wide variety of plant configurations. On the other hand installation effects are one of the most important causes of flow meters inaccuracy. In the present paper the authors analyse the effects of two important low level perturbations in a downstream straight pipe on insertion flow meters. The aim of the work is to evaluate: i) the minimum distance between the flow meter and the perturbation that makes negligible the installation uncertainty, ii) the systematic error of different insertion flow meters.
This paper is concerned on the new type of the sensing elements for a particle volume of flow rate measurements based on cross correlation flowmeters. The new type of sensing elements exploit the fact that the solid particles being carried by a flowing air and impacting a properly formed obstacle generate an acoustic surface wave (acoustic emission - AE). The acoustic signal is indicated by the aid of a high sensitive transducer, which converts the acoustic signal to an electric one. If we use two sensing elements in the flow channel with defined distance, we may use cross correlation...