Browsing by Author "Ger, JS"

Now showing 1 - 4 of 4

A concise method for determining a valve how coefficient of a valve under compressible gas flow
(1998-12-01)
Fu, WS
;
Ger, JS
;
機械工程學系
;
Department of Mechanical Engineering
This work presents a novel method of determining a valve flow coefficient for a valve and transient mass flow rate of compressible gas discharged from a reservoir. The proposed method consists of a set of equations to express the physical phenomena and measurement equipment to measure the indispensable data used in the above equations. Regardless of the kind of valve, the Valve flow coefficient can be obtained efficiently and feasibly. The results of this study indicate not only that the valve flow characteristics of the diaphragm valve significantly differ from those of the ball valve, but also that the C-v flow equation conventionally used is no longer valid for the diaphragm valve. The valve flow coefficient of the ball valve determined by the proposed method is about 48 and the representative one proposed by the ANSI/ISA is about 56. In addition, the mass flow rate of gas flow through a valve under transient process can be estimated without using a flow meter. Moreover, the cumulated masses discharged predicted by the method proposed herein are consistent well with those of the experimental results. The deviations are smaller than 6%. (C) 1999 Elsevier Science Inc. All rights reserved.
A concise method for determining a valve how coefficient of a valve under compressible gas flow
(1998-12-01)
Fu, WS
;
Ger, JS
;
機械工程學系
;
Department of Mechanical Engineering
This work presents a novel method of determining a valve flow coefficient for a valve and transient mass flow rate of compressible gas discharged from a reservoir. The proposed method consists of a set of equations to express the physical phenomena and measurement equipment to measure the indispensable data used in the above equations. Regardless of the kind of valve, the Valve flow coefficient can be obtained efficiently and feasibly. The results of this study indicate not only that the valve flow characteristics of the diaphragm valve significantly differ from those of the ball valve, but also that the C-v flow equation conventionally used is no longer valid for the diaphragm valve. The valve flow coefficient of the ball valve determined by the proposed method is about 48 and the representative one proposed by the ANSI/ISA is about 56. In addition, the mass flow rate of gas flow through a valve under transient process can be estimated without using a flow meter. Moreover, the cumulated masses discharged predicted by the method proposed herein are consistent well with those of the experimental results. The deviations are smaller than 6%. (C) 1999 Elsevier Science Inc. All rights reserved.
A two-reservoir model to simulate the air discharged from a pulse-jet cleaning system
(1999-08-01)
Fu, WS
;
Ger, JS
;
機械工程學系
;
Department of Mechanical Engineering
This work presents a novel two-reservoir model to simulate, for a pulse-jet cleaning system, the air discharged from an air reservoir via a diaphragm valve to a blowpipe and ultimately into the atmosphere. The air reservoir and blowpipe are referred to reservoir 1 and reservoir 2, respectively. The proposed model consists of (1) a set of governing equations that are solved by a finite difference and (2) an iterative calculation method to describe the physical phenomena. The feasibility of the proposed model is also evaluated via experiments performed herein. Comparing the mass flow rates predicted by the proposed model with those of the benchmark solutions reveals that the model predictions are about 10% overestimated. In addition, the proposed model is more accurately simulated by considering the friction effects induced by the exit of the air reservoir and the nozzles on the blowpipe. The former increases the Mach number of the air and equals that of a frictional pipe of 4fLe/D-h. The latter decreases the mass flow rate discharged from the nozzles. A discharge coefficient Cd-n is introduced to represent the ratio of the mass flow rate discharged from a real nozzle and an ideal one. Moreover, experimental methods are developed to determine the values of 4fLe/D-h and Cd-n. When the parameters of 4fLe/D-h and Cd-n were included in the model, the accuracy of the model predictions was significantly improved. The deviations between the mass flow rates of the model predictions and the bench mark solutions were markedly reduced to 3%.
Numerical and experimental studies to predict properties of gas discharged from a number of nozzles on a blow pipe
(1999-07-01)
Fu, WS
;
Ger, JS
;
機械工程學系
;
Department of Mechanical Engineering
This study numerically and experimentally investigates the properties of pressure, temperature and mass flow rate of air discharged from a number of nozzles drilled on a blow pipe. In addition to deriving a set of equations to express the physical phenomena, this study also uses measurement equipment to measure the indispensable data used in the above equations. Consequently, the theoretical and experimental works complement each other. According to the results, the mass flow rate of the air pulse discharged from a nozzle depends on the position and diameter of the nozzle on the blow pipe. Furthermore, the direction of the discharged air pulse is not perpendicular to the blow pipe and has an inclined angle which also depends on the position of the nozzle on the blow pipe. Employing the model proposed herein, a uniform mass flow rate discharged from each nozzle can be obtained by adjusting the sizes of the nozzles on the blow pipe.