Showing papers by "Jihong Wang published in 2011"

Mathematical Modeling Study of Scroll Air Motors and Energy Efficiency Analysis—Part II

Abstract: A scroll air motor, also known as a scroll expander, is a relatively new concept to pneumatic actuators. Its unique structure leads to its feature of high ability in energy conversion. In recent years, scroll air motors have been adopted by combined heat and power boilers, uninterrupted power supplies, and some other energy storage systems as a new mechatronic device for energy conversion. The paper aims to present the work in developing a complete mathematical model of the scroll air motor for analysis of scroll energy efficiency and the factors affecting energy efficiency. The work will be reported in two parts of the paper. The paper describes the derivation of spiral equations, chamber volume calculations, and the driving torque of the scroll air motor. The dynamic process modeling and energy efficiency analysis will be presented in Part II of the paper.

Dynamic Model for an Oxygen-Staged Slagging Entrained Flow Gasifier

Abstract: A dynamic gasifier model including slag flow behavior simulation was established to simulate a new type of oxygen-staged gasifier recently developed in China. A reactor network model (RNM) is used to simulate the internal gas–solid reaction zone of the gasifier, in which the reactor is divided into several zones based on the understanding of the flow characteristics in the gasifier, with each zone represented by either a plug-flow reactor or a well-stirred reactor. This space division concept can provide a more reasonable temperature distribution prediction than one-dimensional models, without costing too much computational expense. In addition, a widely accepted slag layer model is used to simulate the time-varying slag accumulation and flow on the wall and the heat transfer process through the wall. Using the developed model, two kinds of oxygen-staged gasifiers were simulated: the refractory wall gasifier and the membrane wall gasifier. The RNM predictions were compared with industrial data and computa...

Management and control strategy study for a new hybrid wind turbine system

Abstract: Electrical power generation from wind energy has been recognized as one of major realistic energy sources in CO 2 emission reduction worldwide. However, matching power generation with the load demand remains a great challenge, due to the nature of wind energy intermittency. The paper addresses this issue by developing a new system with the structure of a hybrid connection of the wind turbine and compressed air energy storage. A scroll air motor is adopted to serve as an “air-electricity transformer” to compensate the power output during the period of low wind speed. The paper reports our study in developing a suitable management and control strategy for this hybrid system. The mathematical model for the whole hybrid system is derived in the paper. To achieve steady power output, a multi-mode process control strategy is proposed combined with fuzzy logical pitch control and PI air pressure control. The simulation study has demonstrated that the proposed new hybrid wind turbine system is feasible and has potential for industrial applications.

A New Method for Estimating the Maximum Allowable Delay in Networked Control of bounded nonlinear systems

Abstract: In Networked Control Systems (NCSs) the information is exchanged through a real-time communication network among control system components. So the network induced time delay and data dropouts are unavoidable in NCSs. The time delay may degrade the performance of control systems and even destabilize the systems if the systems are designed without considering the effects of the time delays properly. Once the structure of a NCS is confirmed, it is essential to identify what the maximum time delay is allowed for maintaining the system stability which, in turn, is also associated with the process of controller design. This paper proposes a new method for estimating the maximum allowable time delay in networked control system with norm bounded nonlinearity. Some studies have been reported in estimation of the maximum time-delay allowed for retaining the system stability. However, most of the reported methods are normally over complicated for practical applications. A new stability method based on using the finite difference approximation for the delay term is proposed in this paper for estimating the maximum time-delay tolerance in networked control system with bounded nonlinearity, which has a simple structure and is easy to apply.

Real-time control oriented HCCI engine cycle-to-cycle dynamic modelling

Abstract: For homogeneous charge compression ignition (HCCI) combustion, the auto-ignition process is very sensitive to in-cylinder conditions, including in-cylinder temperature, in-cylinder components and concentrations. Therefore, accurate control is required for reliable and efficient HCCI combustion. This paper outlines a simplified gasoline-fueled HCCI engine model implemented in Simulink environment. The model is able to run in real-time and with fixed simulation steps with the aim of cycle-to-cycle control and hardware-in-the-loop simulation. With the aim of controlling the desired amount of the trapped exhaust gas recirculation (EGR) from the previous cycle, the phase of the intake and exhaust valves and the respective profiles are designed to vary in this model. The model is able to anticipate the auto-ignition timing and the in-cylinder pressure and temperature. The validation has been conducted using a comparison of the experimental results on Ricardo Hydro engine published in a research by Tianjin University and a JAGUAR V6 HCCI test engine at the University of Birmingham. The comparison shows the typical HCCI combustion and a fair agreement between the simulation and experimental results.

An energy efficient pneumatic-electrical system and control strategy development

Abstract: Pneumatic actuators are widely used in industry and many other applications, whereas low energy efficiency has been recognized as a critical drawback compared with corresponding hydraulic and electrical actuators. The paper presents a new hybrid pneumatic-electrical system aiming at energy efficiency improvement by recovering exhaust air energy from pneumatic actuator outlets to generate electricity. A closed-loop control strategy is proved to be essential to ensure the exhaust energy recovery work properly and to maintain existed actuator operations simultaneously. The whole system mathematical model and the simulation results are presented in the paper. The laboratory test results are also given. The simulation and experimental study demonstrate that the designed system with the proposed control strategy can operate at the relative higher energy efficiency state for the specified working conditions.

Mathematical Modelling for Coal Fired Supercritical Power Plants and Model Parameter Identification Using Genetic Algorithms

Abstract: The paper presents the progress of our study of the whole process mathematical model for a supercritical coal-fired power plant. The modelling procedure is rooted from thermodynamic and engineering principles with reference to the previously published literatures. Model unknown parameters are identified using Genetic Algorithms (GAs) with 600MW supercritical power plant on-site measurement data. The identified parameters are verified with different sets of measured plant data. Although some assumptions are made in the modelling process to simplify the model structure at a certain level, the supercritical coal-fired power plant model reported in the paper can represent the main features of the real plant once-through unit operation and the simulation results show that the main variation trends of the process have good agreement with the measured dynamic responses from the power plants.

The dynamic neural network model of a ultra super-critical steam boiler unit

Abstract: Thermal power unit is an energy conversion system consisting of the boiler, the turbine and their auxiliary machines respectively. It is a complicated multivariable system with strong nonlinearity, uncertainty and multivariable coupling. These characters will be more evident with the unit tending to large-capacity and high-parameter. It is expensive to build the model of the unit using conventional method. The paper presents modeling of a 1000MW ultra supercritical once-through boiler unit. Based on these field data, two different neural networks are used to model the thermal power unit. The simulation results validate the efficiency of the neural networks in modelling the ultra supercritical unit.

Study of a multivariable coordinate control for a supercritical power plant process

Abstract: The paper presents the recent research work in study of a novel multivariable coordinate control for a 600MW supercritical (SC) power plant. The mathematical model of the plant is described in the first part of the paper. Then, a control strategy is designed based on Model Predictive Control (MPC) theory. It is noticed that the linear MPC alone performs well only within limited small load changes under a constant level of disturbances and measurement noises generalized from the prediction algorithms. So, a dynamic compensator is proposed to work in parallel with the MPC to track large load changes. Because the model has been identified with on-site closed loop response data, the multivariable optimal control signals have been used as a correction to the reference of the plant local controls instead of direct control signal applications. The simulation results show the good performance of the controller in response to the large load changes. Furthermore, it has been proved that the plant dynamic response can be improved by increasing the coal grinding capability and pulverized coal discharging through implementation of suitable coal mill controllers.

Energy-efficient tracking control of pneumatic cylinders

Abstract: Pneumatic actuators have been widely used in industry for over a hundred years. However, it is well-known that pneumatic actuators have very poor energy efficiency. Also, it is difficult to achieve accurate positioning due to the inherent nonlinearity caused by air compressibility. This paper presents recent work in developing an energy-efficient tracking control strategy for pneumatic cylinders. The pneumatic system is initially transformed into a linear system description using the nonlinear input/output feedback linearization method. Then energy efficient velocity profile is derived based on optimal control theory. A servo/tracking controller is then designed to drive the system to follow the derived new energy efficiency velocity profile. The simulation study indicates that energy consumption can be reduced by 3–5%.

Vehicle windscreen wiper mathematical model development and optimisation for model based hardware-in-the-loop simulation and control

Abstract: Hardware-in-the-loop (HIL) simulations have long been used to test electronic control units (ECUs) and software in car manufactures. Accurate Model based HIL simulation (AMHIL) is considered as a most efficient and cost effective way for exploration of new design and development of new products, particularly in calibration and parameterization of vehicle stability controller. The paper presents our recent work in developing an accurate real-time mathematical model for a Jaguar windscreen wiper system, which will be adopted for the HIL tests to the vehicle body control module (BCM). Based on the electro-mechanical engineering principles, the mathematical model of the windscreen wiper system is developed and the unknown model parameters are identified using Genetic Algorithms. Model has been tested by operating at different working conditions, e.g. varied voltage input levels. Real-time implementation of the mathematical model onto dSPACE Ecoline HIL simulator is explained, and the configurations of the laboratory test rig are reported.

Study on a Wind Turbine in Hybrid Connection with a Energy Storage System

Abstract: Wind energy has been focused as an inexhaustible and abundant energy source for electrical power generation and its penetration level has increased dramatically worldwide in recent years. However, its intermittence nature is still a universally faced challenge. As a possible solution, energy storage technology hybrid with renewable power generation process is considered as one of options in recent years. The paper aims to study and compare two feasible energy storage means—compressed air (CAES) and electrochemical energy storage (ECES) for wind power generation applications. A novel CAES structure in hybrid connection with a small power scale wind turbine is proposed. The mathematical model for the hybrid wind turbine system is developed and the simulation study of system dynamics is given. Also, a pneumatic power compensation control strategy is reported to achieve acceptable power output quality and smooth mechanical connection transition.