Flow Characteristics Of Valve Research Articles

Doppler forward flow profiles of St. Jude Medical prosthetic valves in pediatric patients

In summary, this data on baseline and follow-up Doppler flow characteristics of small caliber SJM prosthetic valves should be extremely valuable for identifying valve dysfunction in children. Because of the high risk of developing valve obstruction, these children should be closely monitored with serial Doppler examinations.

Experimental Investigation of Flow and Force Characteristics of Hydraulic Poppet and Disc Valves

Tests have been performed on a range of different poppet and disc valves operating under steady flow, non-cavitating conditions, for Reynolds numbers greater than 2500. The working fluid was water, and the axisymmetric valve housing was constructed from clear perspex to facilitate flow visualization. Measured flow coefficients and force characteristics show marked differences depending on valve geometry and opening. These differences are explained with reference to visualized flow patterns.

Flow Characteristics of Bioprosthetic Heart Valves

A review of the in vivo and in vitro fluid dynamic performance of three bioprosthetic heart valves is presented. Data on Hancock porcine valves (standard models 242 aortic and 342 mitral and modified orifice model 250 aortic), Carpentier-Edwards porcine valves (model 2625 aortic and 6625 mitral), and the Ionescu-Shiley pericardial valve are reviewed. These valves were chosen because of their past or present popularity in clinical use and because of the variation in fluid dynamic performance reported by different investigators. The flow parameters that are reported include in vivo and in vitro mean pressure drop, cardiac output or cardiac index, regurgitant volume, effective orifice area, and performance index. These data provide a framework for differentiation of normal and abnormal bioprosthetic valve function.

An Analysis of a Pneumatic Servo System and Its Application to a Computer-Controlled Robot

Pneumatic actuators are capable of providing high power output levels at a relatively low cost. In addition, they are clean, lightweight, and can be easily serviced. The difficulty of achieving a high-bandwidth, stable, pneumatic control system has limited its use in robotic position control applications. For open-loop control applications, such as many robot grippers, pneumatic actuators are often used. In this paper, direct-drive pneumatic servo-actuators are examined for their potential use in robotic applications. A complete mathematical model of the actuator is derived, and several control algorithms are tested numerically and experimentally. Our analysis shows that pneumatic systems are practical for use in servo-control applications. The main limitation is that of the system response time, which is determined by the valve flow characteristics and supply pressure. Large output forces can be obtained and accurately controlled with the servo-valve and differential pressure transducer used in the experiments.

An Investigation of Compressible Flow Characteristics of Butterfly Valves

Compressible flow characteristics including mass flowrate, onset of “choked” flow, stagnation pressure loss, and static pressure recovery have been investigated for butterfly valves. A simplified sudden-enlargement in flow area theoretical model has been used to characterize the overall mass flowrate and pressure characteristics of the valve flow. A series of small-scale compressible flow experiments has also been conducted using sudden-enlargement configurations with different nozzle geometries and using geometrically similar model valves. These experiments provided a database for augmenting the simplified theoretical model with needed empirical information and for assessing the range of applicability of the theoretical model. This method can be used to predict the mass flow and pressure characteristics of full-scale valves based on model experiments and/or to determine the overall operating characteristics of full-scale valves from in situ pressure measurements.

Flow characteristics of exhalation valves of diving regulators

This study presents the flow-resistance characteristics of conventional exhalation valves used in underwater diving regulators. Evaluation of such characteristics is essential to quantifying the effect of the main design parameters of these valves on the diver's exhalation effort. Plain, tapered as well as tapered supported valves of different materials have been considered in this study. Valves seats of different geometrical configurations which varied from the simple multi-circular hole seats to the more imaginative Posiden-like seats have been studied. Triangular, multi-quadrant as well as full diaphragm exhalation valves have also been tested in details. New designs of exhalation valves have also been developed and tested in an attempt to define the optimum configuration as well as the best combination of the valve and its seat that would reduce the exhalation effort to a minimum. Among the considered new designs are the vortex and nozzle-assisted exhaust valves. The obtained results show that full diaphragm exhalation valves offer the least breathing resistance followed by the 13-hole Posiden-like exhalation valve, the nozzle-assisted valves and the vortex-assisted valves. Nonetheless, the 2.9-cm diameter plain, unsupported and untapered valve on the six-triangle seat exhibits flow characteristics that are not too far from the most fancy designs. The obtained results presents design guides, for improving the breathing characteristics of the exhalation valves, which can be extremely important to the designers and manufacturers of diving regulators.

A First Principles Model for Steam Turbine Control Analysis

A first principles model of a steam turbine is presented. Its intended use is to aid the design and analysis of control systems in which thermal and fluid interactions between the turbine and balance-of-plant are of primary concern. Thus the focus is representation of aggregate steam flow dynamics. Modeling of individual governor valve flow characteristics as well as an algorithm for representing governor valve overlap are two distinguishing factors of this model.

Theoretical Prediction of Flow Characteristics of Certain Flow Control Valves Used in Hydraulic and Pneumatic Systems

Valve selection is of major importance in hydraulic and pneumatic control systems. The suitability of any flow control valve for throttling service can be judged from its flow characteristics. This is also important from the consideration of actuator mechanism and the mode of control.At present, the valve design and selection is mostly done in an empirical way based on manufacturer’s data. Mathematical models predicting complete flow characteristics are not available.In the present investigation, the development of “equivalent orifice theory” for theoretical prediction of complete flow characteristics has been reported. The new correlation developed by present authors along with the development of theory of equivalent orifice leads to the final result.Two typical valves: butterfly valve and diaphragm-operated poppet valve, have been analysed. The theoretical predictions agree very well with experimental results. Computer aided analysis has been developed. Useful comparison is made in respect of many important performance criteria.

Determination of Orifice Characteristics of Spool Type Control Valves

A method of obtaining the flow characteristics of spool type control valves is outlined.

An improved method for determining the flow characteristics of prosthetic mitral heart valves.

The flow characteristics of most prosthetic mitral valves recommended for clinical use have not been adequately investigated. As a result vital information about their performance is lacking and, until this is published, comparisons between different prostheses cannot easily be made. In this paper the design and construction of a suitable rig for the testing of such valves is described. The results obtained will be presented in a subsequent paper.

A new method of testing mitral valve flow characteristics.

A new method of testing mitral valve flow characteristics.

Discussion of “Flow Characteristics of Butterfly and Spherical Valves”

Discussion of “Flow Characteristics of Butterfly and Spherical Valves”

Flow Characteristics of Butterfly and Spherical Valves

Discharge coefficients of butterfly and spherical valves are given. The data were obtained from tests of 10-in. diam models. Four butterfly valve disks were tested, all lenticular in shape. One of them had the disk offset in relation to the shaft. Four spherical valve rotors were tested. These data can be used to predict the flow and torque for a given set of conditions as illustrated in the numerical examples. In testing spherical valve models, hydrodynamic force on the valve also was measured. These data can be used to size the trunnions of such valves. The tests were conducted with air as working fluid. The results can be applied to flow of liquids provided that cavitation does not occur.

Flow characteristics of control valves: T J Black and A Brown,The Engineer, Nov 1965, 874–876.

Flow characteristics of control valves: T J Black and A Brown,The Engineer, Nov 1965, 874–876.

Closure to “Butterfly Valve Flow Characteristics”

Closure to “Butterfly Valve Flow Characteristics”