Pressure Control Strategy Research Articles

Predictive co-ordinated control for power-plant steam pressure and power output

This paper describes a new predictive control strategy for power-plant steam pressure and power output control. Two methods are introduced to improve existing boilers following PID control strategies in a reheat power plant to reduce pressure variations with load changes. Firstly, a multi-input multi-output model-based predictive control (MBPC) is used to design co-ordinated control of power, pressure and water level. Secondly, the steam pressure after the governing stage is fed back as an estimate of turbine power output to replace electric power. The proposed control is tested on a real-time hybrid laboratory simulator employing a detailed nonlinear boiler model and a micro-turbogenerator. Results show the significant improvement of overall performance, compared to existing control.

Di Diesel Engine with Variable Geometry Turbocharger (VGT): A Model Based Boost Pressure Control Strategy

The use of a variable geometry turbocharger (VGT) is a very efficienttechnology to improve performance of passenger car direct injection (DI)Diesel engines. In order to take full advantage of the potential of VGT,without penalty on fuel consumption and driveability, electronic control ofboost pressure is desirable. Standard control techniques (i.e.Proportional-Integral) do not assure a reliable VGT behaviour. This paperdescribes a new boost pressure control strategy developed to improve PItechnique, and based on a simplified modelling of VGT operation. Severaltests were carried out on engines to point out which physical quantitiesdirectly influence VGT dynamics, and to find out VGT operation modes (OMs).Simplified models for each OM were developed and model parameters wereidentified. Experimental tests provided a basis to design a control strategyable to meet general performance requirements. Since two different OMs wererecovered, two separate governors were developed, each active under certainconditions. A switching logic was created to manage transitions between thetwo governors. Finally, the new control strategy was validated on the enginewith good results.

Pressure control of a Moscow water supply system using expert system technology

Automating the pressure control of typical Russian types of water distribution systems can result in greater than average benefits. The potential exists for improving the system efficiency and reliability while reducing the on-line operational manning requirements. To this end the paper presents modelling and simulation studies of the current semi-manual and the proposed fully automatic pressure control schemes for the Zelenograd water supply system. Dynamic operational simulations are an essential feature of the project. However, it was necessary to enhance the network hydraulic simulator, to include pressure feedback controls, in order to produce acceptable results. Analyses of the operational requirements and the simulation results provide a basis for the design of an improved controller using an expert system approach. A major part of the paper covers the methods in use for obtaining an adequate set of control rules for the Zelenograd system. Extended time period operational simulations are used to verify the rules and to compare the results with those of existing practice. There are expectations of immediate benefits in terms of operating economies. Typically these will arise from reductions in water leakage, electricity charges and control manpower. Work is now proceeding on actual implementation using a combination of expert system and fuzzy logic methods.

An Intake Manifold Model for Spark Ignition Engines

In this paper a model of the air flow and pressure inside the intake manifold of spark ignition engines is derived from mass and momentum balance equations. The model is capable to predict the physical phenomena inside the engine cycle. Linearization around a nominal point derived from a Mean Value Model allows to determine the tranfer functions relating the throttle angle variation and the poppet valve lift to pressure and air flow in the manifold. The knowledge of these tranfer functions can be the starting point for the design of more accurate pressure control schemes.

LEAKAGE REDUCTION AND SECURITY ENHANCEMENT FOR WATER DISTRIBUTION NETWORKS BY ON-LINE PRESSURE CONTROL

Abstract This paper presents a method for operational leakage reduction and security enhancement of water distribution networks using optimised on-line control of pressure reducing valves and variable speed pumps. An earlier algorithm which uses valve control only has been extended to solve the combined problem of controlling valves and variable speed pumps, and furthermore, new hydraulic constraints have been added. The problem is formulated as an optimisation of the system pressure profile subject to the network hydraulic balance and system operational constraints. A solution technique based on successive linear programming is described. Sparsity techniques are employed to achieve computational efficiency. The effectiveness of the pressure control scheme is illustrated using an example network.

圧力比例弁による電気空気圧制御

The electropneumatic proportional valve controls the airflow rates or pressure in proportion to the electric current by using a proportional magnet. The uniqueness of the magnetic field of the proportional magnet makes it difficult to predict or reproduce its performance due to an incorrect estimation of magnetic flux's saturation and leakage. In this paper, the magnetic field of the proportional magnet is clarified by making the contour lines of flux and flux density with the aid of the FEM magnetic analysis. Next, a three-way type pressure proportional valve is developed, which enables the controlling of the pneumatic pressure in proportion to the electric current of 0.9 MPa/0.8 A within a 30 ms response time with the flow capacity of 1.33x10-2 kg/s at 0.49 MPaAbs. The pressure proportional valve is applied to the position control of servocylinder, which demonstrates that the pressure control strategy improves the fluctuation of dynamic characteristics because of the control of the penumatic compliance.

Contactless instruments and pressure control schemes in glass furnaces

Contactless instruments and pressure control schemes in glass furnaces