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Control valves I
Published in Ian C. Turner, Engineering Applications of Pneumatics and Hydraulics, 2020
The flow control valve (Figure 6.9) restricts or throttles the fluid in a particular direction to reduce the flow rate of the fluid and hence control the signal flow. If the flow control valve is left wide open then the flow should be almost the same as if the restrictor were not fitted. In some cases it is possible to infinitely vary the restrictor from fully open to completely closed. If the flow control valve is fitted with a non-return valve then the function of flow control is uni-directional with full free flow in one direction. A two-way restrictor restricts the fluid in both directions of flow and is not fitted with the non-return valve. The flow control valve should be fitted as close to the working element as possible and must be adjusted to match the requirements of the application.
Creation and Control of Fluid Flow
Published in John S. Cundiff, Michael F. Kocher, Fluid Power Circuits and Controls, 2019
John S. Cundiff, Michael F. Kocher
Flow control valves are used in constant-flow (fixed displacement pump) circuits to control actuator speed. The simplest type of flow control valve is a needle valve. The formal name for a needle valve is a non-pressure-compensated flow control valve. Turning the manual adjustment on a needle valve causes the needle to move down into the orifice, thus reducing the orifice area. Pressure drop across the valve (ΔPfc) is increased by continuously restricting the orifice until enough pressure is produced to cause the system relief valve to crack open. At this point, extra turns will further reduce the orifice, increase the ΔPfc, increase the pressure at the relief valve, dump more fluid to the reservoir, and thus slow the actuator. The sequence of events is exactly the same as using a directional control valve (DCV) to control actuator speed. If load pressure changes over a narrow range, the needle valve will give fairly good flow control. Again, a reminder is given. Flow across the relief valve represents an energy loss. A needle valve is inexpensive, but the operating cost is high because of the energy loss.
Hydraulic Systems
Published in Anton H. Hehn, Fluid Power Troubleshooting, 1995
When flow rates must be changed, the simplest method is to add a flow control valve in the system at an appropriate place. A flow control valve is a device that controls flow rate through use of an orifice. In simpler valves, the orifice and its associated pressure drop provide the throttling effect. In others, an orifice is used to detect changes in rate of flow, and the changing pressure drop through the orifice operates a valve member which controls the flow.
Influence of rotating twisted tape turbulator and nanofluids on heat transfer characteristics in a tube
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Pavan Kattedoddi Nagaraju, Chethan Kedage Srikanth, Sathish Govind
Experimental trials were carried out with water and different NFs (0.2% vol. concentration) to estimate the flow and heat transfer in a tube with (0–300 RPM) and without rotating TTT of different geometric configurations at different flow rates (1–6 LPM). The desired heat input is adjusted using dimmer stat, it maintains the uniform voltage across the heater and provides constant heat flux on the wall. The working fluid filled in the storage tank is pumped through inlet valve of the test section. The flow control valve is used to adjust the rate of flow of the working fluid to conduct the experiments. Further, when the steady state conditions are achieved, the contributed power and the temperatures at different locations are recorded. The heat transfer coefficients for water and different NFs (0.2% vol. conc) with and without rotating TTT up to 6 LPM are estimated. During the experimentation, the test section pipe wall temperatures, inflow and outflow working fluid temperatures, mass flow rates and pressure drops are measured.
Design and implementation of an intelligent digital pitch controller for digital hydraulic pitch system hardware-in-the-loop simulator of wind turbine
Published in International Journal of Green Energy, 2021
V. Lakshmi Narayanan, R. Ramakrishnan
In the full load region, the pitch angle controller will aim at increasing the lift force and reducing the drag on the blade. Thus, the pitch control system is one of the most widely used control methods for improving the power generation in medium to large-scale WT (Abdelbaky, Liu, and Jiang 2020; Yin et al. 2015; Yuan, Chen, and Tang 2020). Nowadays, modern large-sized WT is deployed to increase the power extraction from the wind. Pitching control of large-sized turbine requires Hydraulic Pitch System (HPS) because of its high power-to-weight ratio and robustness (Venkaiah and Sarkar 2020; Yin et al. 2015). It exhibits better pitching action when compared with its electrical counterpart. At the same time, HPS uses a Proportional Flow Control Valve (PFCV) to control the fluid flow and direction of the actuator, as shown in Figure 2a. These conventional valves have some drawbacks such as high power loss, throttling loss, internal leakage, and high cost (Siivonen et al. 2009; Linjama 2011; Scheidl, Linjama, and Schmidt 2012).
Artificial neural network model for the flow regime recognition in the drying of guava pieces in the spouted bed
Published in Chemical Engineering Communications, 2020
Yago Matheus da Silva Veloso, Marcello Maia de Almeida, Odelsia Leonor Sanchez de Alsina, Manuela Souza Leite
The spouted bed dryer system consists of a plexiglass conical cylindrical column and the dryer wall allows visual observation of the changes that take place in the flow regimes during drying. The column has 1 m height, 10.8 cm internal diameter, and 4.6 mm thickness; the conical base was 9 cm tall and had an internal angle of 60°; and the diameter of spout nozzle was 2.8 cm. The experimental apparatus was completed with an air supply system, that included a blower (model S100L2, 4 hp, 2920 rpm, Eberle), a rotameter (model R.2.V.C, capacity of 400 m³ h−1, Omel), and a flow control valve (globe valve, Emerson). The pressure drops (Δp) in the bed was measured by a “U” type manometer, filled with oil (density 0.86 g cm−3). Later, this variable was expressed as mm of oil in Figure 1.