Pressure Control Method Research Articles

Research on Pressure Control Method of some Wind Tunnel Spraying Water Supply System

By analyzing pressure control process of some wind tunnel spraying water supply system, a simplified method is presented, which can avoid interference between different pressure control circuits. Regulating valve is the key control equipment, and its regulating formula is given after detailed calculations and analysis. The simulation of pressure control for spraying water supply system is researched based on AMESim, which provides the theoretical support for experiment. In the end,experimental results show that the control method is effective, and water pressure precision can meet the technical requirements.

Heat pump control method based on direct measurement of evaporation pressure to improve energy efficiency and indoor air temperature stability at a low cooling load condition

The control systems of conventional heat pumps have an input of refrigerant temperature at the evaporator outlet to maintain superheat at proper level. In order to develop a control method that can be used to achieve better indoor thermal comfort and energy efficiency at a low cooling load condition than the current control method, a new method of the evaporation pressure control based on the evaporator outlet pressure reading (EPCP) was developed. The changes in the stability of indoor air temperature and power consumption were measured while changing the compressor frequency in accordance with the new control method. Compared with the evaporation pressure control based on the evaporator outlet temperature reading, the EPCP control method appeared to improve the stability of room air temperature or occupant thermal comfort significantly.

The Thickness of Immediate Roof and Surrounding Rock Control Theoretical Research

Somewhere on the specific geological conditions of surrounding rock, adopt the different method, calculates the thickness of immediate roof in the area, the thickness of immediate roof was got, which to explore the suitable method for formation conditions of pressure control method, good effects have been achieved.

A historical perspective on peripheral reflex cardiovascular control from animals to man.

Although drug treatment of human hypertension has greatly improved, there is renewed interest in non-drug methods of blood pressure reduction. Animal experiments have now shown that arterial baroreflexes do control long-term blood pressure levels, particularly by nervously mediated renal excretion of sodium and water. This Paton Lecture provides a review of the historical development of knowledge of peripheral circulatory control in order to supplement prior Paton Lectures concerned with cerebral cortical and other areas of influence. I also discuss how improved understanding of nervous control of the circulation has led to current methods of non-drug blood pressure control in man by implanted carotid baroreceptor pacemakers or by renal denervation. Finally, the role of other therapy, particularly listening to music, is reviewed.

Advanced Linear Proportional Control of a Pressure Valve for an Electric Pressure Cooker

This paper describes the advanced control of solenoid for pressure valve for electric pressure cooker. To remove the problem of the on/off non-proportional pressure control method which was used to control the existing solenoid, newly redesigned solenoid was adopted and the advanced control method, linear proportional control method, was proposed. The control system by the pressure sensor and AVR was manufactured and its validation was proved through the experiment.

Pressure Control Method of Work Chamber of Shield Machine Based on Dynamic Pressure Balance

Pressure Control Method of Work Chamber of Shield Machine Based on Dynamic Pressure Balance

Width-modulated square-wave pulses for ultrasound applications

A method of output pressure control for ultrasound transducers using switched excitation is described. The method generates width-modulated square-wave pulse sequences that are suitable for driving ultrasound transducers using MOSFETs or similar devices. Sequences are encoded using an optimized level-shifted, carrier-comparison, pulse-width modulation (PWM) strategy derived from existing PWM theory, and modified specifically for ultrasound applications. The modifications are: a reduction in carrier frequency so that the smallest number of pulses are generated and minimal switching is necessary; alteration of a linear carrier form to follow a trigonometric relationship in accordance with the expected fundamental output; and application of frequency modulation to the carrier when generating frequency-modulated, amplitude- tapered signals. The PWM method permits control of output pressure for arbitrary waveform sequences at diagnostic frequencies (approximately 5 MHz) when sampled at 100 MHz, and is applicable to pulse shaping and array apodization. Arbitrary waveform generation capability is demonstrated in simulation using convolution with a transducer's impulse response, and experimentally with hydrophone measurement. Benefits in coded imaging are demonstrated when compared with fixed-width square-wave (pseudo-chirp) excitation in coded imaging, including reduction in image artifacts and peak side-lobe levels for two cases, showing 10 and 8 dB reduction in peak side-lobe level experimentally, compared with 11 and 7 dB reduction in simulation. In all cases, the experimental observations correlate strongly with simulated data.

상수관망에서 누수탐지를 위한 역추적계산법

【In this study, Back Tracing Calculation Method was developed to determine the leakage location and leakage amount. Previously developed determination method of monitoring location and newly developed Back Tracing Calculation Method were applied to the sample pipe network and real size pilot plant. After leakage was assumed in the pilot plant, leakage location and leakage amount could be traced by Back Tracing Calculation Method. From the results, it was found that Back Tracing Calculation Method can be applied for the leakage detection in water distribution system. Furthermore, this method can be applied for the pressure management or leakage detection as a pressure control method in water distribution system.】

Frequency pressure regulation in water supply systems

In water supply systems, pressure management in most cases is proven to be the most cost-effective activity related to water loss control. As an advanced method of pressure control, it is possible to use variable frequency drives for centrifugal pump control. Pressure regulation can be performed with constant pressure or with proportional pressure control. The application of proportional pressure control is particularly applicable in water supply systems as the operating pump performance is constantly adapting the pressure to the actual demand. Along with lower leakage losses, it also results in lower energy consumption and the elimination of non-stationary phenomena, thereby extending the pump lifetime. Therefore, the paper presents a theoretical discussion of the proportional pressure control. Possible savings are shown on the numerical example of water supply system of the city of Velika Gorica.

Experimental analysis of the thermal stability of the pressure control method for a variable flow air-conditioning water system

In this study, we investigate the stability of a pipe network for differential pressure (DP) control of a variable flow air-conditioning chilled water system. First, the hydraulic properties of the pipe network and the thermal properties of the terminal air-conditioning equipment are presented, and the thermal stability is defined to serve as an indicator of the impact that flow regulation in the active branches has on the energy supply capacity of the passive branches. An evaluation indicator of the thermal stability is also developed for online applications. Second, dynamic changes in the hydraulic and thermal properties of the passive branches of a primary pump variable flow dual loop air-conditioning water system were experimentally studied during an active branch regulating valve action stroke cycle using an uncontrolled hydraulic pump, constant DP control and variable DP set-point control. The feasibility and energy savings of various DP control strategies were evaluated in terms of the thermal stability and energy savings for hydraulic pumps. The results show that using a variable DP set-point control strategy produced significant energy savings; however, the thermal stability must be considered when setting the step size in adjusting the DP set-point.

Ultra High Pressure Control Technology on Small Cavity

Based on the current key problem of the ultra high pressure control technology on the small cavity, an analysis method of the ultra high pressure control was put forward on 500ml small cavity. The mathematical model was derived on pressure-volume change of the small cavity. A pressure control system was set up on the small cavity according to the model. Control program was done using labview software, test process was completed automatically, test data was displayed in real time and the output data and report form was received. The test results show that the system have achieved the function of a increasing ultra pressure. The capacity of system increasing pressure is up to 150Mpa, controlling pressure accuracy up to 0.31% and the holding pressure accuracy up to 0.48%.

Research on Pressurizer Pressure Control System of 900MW Pressurized Water Reactor Nuclear Power Plant

It is of vital importance for the pressurizer to maintain the pressure of primary coolant because the sharp change of coolant pressure has a direct impact on the security of reactor. The study of pressurizers pressure control method is highly important and meaningful. This paper presents the researching and designing on pressure control system of a pressurizer implemented in a nuclear power plant. Both the present situation of the nuclear power and some relevant background have been briefly introduced. Proceeding on the records of simulation, we succeed in establishing the applied modeling of pressurizer and further propose the PID control technology working as control algorithm. The best set of controller parameters are chosen through comparing the results including regulation time, overshoot suppression and stability. On the base of such control method, we attempt to add neural network control technology to achieve further improvement, which turns out available and satisfying.

Modeling and Control of Heave-Induced Pressure Fluctuations in Managed Pressure Drilling

Automatic managed pressure drilling is an advanced pressure-control method which is intended to meet the increasingly high demands in drilling operations in the oil and gas industry. In this method, the circulating drilling fluid, which takes the cuttings out of the well, is released at the surface through a controlled choke. This choke is used for active control of the fluid pressure in the well. The corresponding automatic control system keeps the pressure at the bottom of the well at a specified setpoint despite various disturbances. One such disturbance, i.e., the vertical motion of the drill string, causes severe pressure fluctuations which need to be actively attenuated. In this paper, we present two different disturbance rejection strategies based on discretized partial differential equations for the well hydraulic system. The performance of the controllers is shown through simulations both under idealized conditions and on a high-fidelity drilling simulator.

Molten Metal Pressure Control for Defect Prevention with Generalized Predictive Control in Rapid Press Casting

This paper presents a technique for controlling the pressure of molten metal when using a new type of the iron production method called greensand mold press casting to realize high productivity and obtain high-quality castings. In this method, molten metal is poured into a lower mold first, and the after upper mold is moved down toward the lower mold, then both molds are matched. Casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing process. Therefore, we proposed a pressure control method with a mathematical model of molten metal pressure, and with it we achieved confirmation simulation of the successful pressing production at the different pressing condition such as mold shape. Results show that the proposed pressing production considering the generalized predictive control: GPC can realize sound, penetration-free casting production under the pressure constraint for defect prevention. Here a simple simulation of model predictive pressing control and water pressing experiment using feed-forward motion input calculated by off-line GPC are presented. Discussions of the theoretical control design for the process as well as its practical confirmation result of water pressure behavior in pressing experiment are concluded.

Invariant Method of Load Independent Pressure Control in Steam Boiler

Abstract The paper considers the possibility of steam production and supply process improvement by perfection of the steam boiler control system, applying invariance principle that makes possible preemptive compensation of the influence of steam expenditure as a disturbance on the control process quality and efficiency. For the development of invariant control system, the mathematical modeling and simulation in MATLAB - SIMULINK environment is made. The control unit is low pressure steam boiler with one input impact to control - the heat flow of burning gas mixture fuel, one measured output parameter of the process - the steam pressure, and the main disturbance as a load impact - the steam expenditure. The mathematical and virtual models and block-diagrams for transient process simulation is compiled, allowing to start practical design and investigation of steam boiler invariant control system with high operation stability under essentially fluctuating load. The simulation results prove that the optimal solution for the transient process improvement in steam boiler, taking in account fluctuating load, is invariant PID-DPC two loop control system with disturbance impact on steam pressure preemptive compensation. Under invariant control the steam pressure overshoots decreases substantially in comparison with the traditional PID-feedback control method.

Research on the Key Technology of NC Abrasive Belt Grinding for the Leading and Trailing Edges of Aeroengine Blades

This document provides an analysis of the structure characteristics and grinding process requirements of leading and trailing edges, and proposes a grinding process of leading and trailing edges, established a uneven grinding margin model, research the quantitative grinding pressure control method of uneven margin, as well as the error compensation technology of blade machining deformation, and experiments were carried out on the basis of theories above. The experimental results demonstrate that: after grinding, the edge roundness improved greatly, dimensional accuracy of edge radius can reach ±0.07mm.Compared with the traditional manual polishing method, the grinding quality improved significantly.

A method to generate pressure gradients for molecular simulation of pressure-driven flows in nanochannels

One of the difficulties in molecular simulation of pressure-driven fluid flow in nanochannels is to find an appropriate pressure control method. When periodic boundary conditions (PBCs) are applied, a gravity-like field has been widely used to replace actual pressure gradients. The gravity-fed method is not only artificial, but not adequate for studying properties of fluid systems which are essentially inhomogeneous in the flow direction. In this paper, a method is proposed which can generate any desired pressure difference to drive the fluid flow by attaching a “pump” to the nanofluidic system, while the model is still compatible with PBCs. The molecular dynamics model based on the proposed method is applied to incompressible flows in smooth nanochannels, and the predicted velocity profiles are identical to those by the gravity-fed method, as expected. For compressible flows, the proposed model successfully predicts the changes of fluid density and velocity profile in the flow direction, while the gravity-fed method can only predict constant fluid properties. For fluid flows in nanochannels with a variable cross-sectional area, the proposed model predicts higher mass flow rates as compared to the gravity-fed method and possible reasons for the difference are discussed.

J113032 ノズルフラッパ型空気圧サーポ弁の動特性を考慮した圧力制御

Softness peculiar to pneumatics is suitable for the pressure control. A servo valve is used when a highly precise pressure control is required. Although it is known that the performance of a pressure control has the great influence of the dynamic characteristic of a valve, the dynamic characteristic of a valve has been disregarded in the conventional research. In previous studies, we showed a control system design method for pressure control considering the dynamic characteristics of this spool type servo valve with a feedback of the valve displacement, and confirmed its effectiveness. However, this design method can not apply to the servo valve without a feedback, such as a nozzle-flapper type servo valve which does not have a valve displacement sensor. In this research, we proposed a control system design method for pressure control using a nozzle flapper type servo valve and conducted the experiment to various conditions containing modeling errors. Suitable responses were obtained in any condition, its validity and effectiveness of the proposed control system design method was verified.

2A1-D07 可逆化学反応現象を利用したガス圧制御システムの開発 : 第1報;水の分解/合成を利用した試作実験(アクチュエータの機構と制御(1))

Recently, the need of mobile compressors with portability, silence and high efficiency are strongly required for pneumatic actuators, while conventional pressure sources generated by air compressors are large, heavy, noisy, and low-efficient. This paper proposes a new mobile pressure control system using reversible chemical reactions. This report shows its basic mechanism and basic experiments using the first prototype, which show a big possibility of this new idea. This device consists of a PEM fuel cell and a current controller is able to change the internal pressure with electric current. In addition, we have developed a pressure control method by electrical current.

Feed Forward Active Disturbance Rejection Control Method for Common-Rail Pressure Control of Diesel Engine

The precise pressure control in common rail is the prerequisite for the excellent performance of common rail diesel engine. Because of the complexity of engine working conditions, conventional PID controller cannot meet the demand of flexible control of common rail pressure, especially when engine load changes largely and rapidly. To overcome the shortcomings of conventional PID, feed forward Active Disturbance Rejection Control (ADRC) has been applied in the common rail pressure control system. The high pressure common rail system layout is drawn and the principle of common rail pressure control is introduced. Four control functions are carried out: “Rail pressure set point calculation”, “Feed forward controller”, “ADRC controller”, and “Flow to duty cycle”. Finally, experimental results comparing between feed forward ADRC controller and conventional PID controller shows that: feed forward ADRC controller is more effective than conventional PID controller because it is smaller in error, quicker in track speed and stronger in anti-jamming ability. It ensures the common rail engine meet the strict specification of the law based on the good dynamic performance.