基于模型的汽车电动助力转向系统故障诊断

汽车转向系统是汽车正常行驶的重要保障,转向系统故障是造成交通事故的重要因素之一。汽车转向系统操纵的稳定性,直接影响汽车的行驶安全。电动助力刹车系统能提升驾驶者的安全系数,在进而保证交通稳定、安全、通畅地运行。文章对电动助力转向系统结构进行了分析,并在汽车模型下验证了电动助力转向系统的实用性,旨在为电动助力转向系统的创新提供参考。

Three-Dimensional Dynamic Modeling of a Tangentially Fired Utility Boiler Furnace

The tangentially fired utility boiler furnace is divided into several sections. The dynamic mathematical models for each section are presented. In the combustion zone, three dimensional model is used, while for the upper sections, lumped parameter model is used instead. With the combination of different models, we can get detailed distributions of gas velocity, temperature, chemical species, heat flux, etc. in the furnace, but with less CPU time. The radiation through the interfaces of each section is cons...

Computational Modeling of Tangentially Fired Boiler(Ⅱ) NO_x Emissions

The paper describes numerical and experimental study on reduction of NOx emissions in a 600 MW tangentially fired boiler furnace under different operating conditions. A simplified NOX formation mechanism model, along with the gas-particle multiphase flow model, is adopted. The prediction yields encouraging results as compared to experimental data.

Optimal dynamic dispatch of surplus gas among buffer boilers in steel plant

As valuable energy in iron-and steel-making process,by-product gas is widely used in heating and technical processes in steel plant.After being used according to the technical requirements,the surplus by-product gas is usually used for buffer boilers to produce steam.With the rapid development of energy conservation technology and energy consumption level,surplus gas in steel plant continues to get larger.Therefore,it is significant to organize surplus gas among buffer boilers.A dynamic programming model of that issue was established in this work,considering the ramp rate constraint of boilers and the influences of setting gasholders.Then a case study was done.It is shown that dynamic programming dispatch gets more steam generation and less specific gas consumption compared with current proportionate dispatch depending on nominal capacities of boilers.The ignored boiler ramp rate constraint was considered and its contribution to the result validity was pointed out.Finally,the significance of setting gasholders was studied.

Model prediction of the operating behavior of a circulating fluidized bed boiler

An improved mathematical model for a circulating fluidized bed (CFB) boiler based on the model developed earlier by the authors was applied to simulate the operation of a 12 MW CFB boiler. The influences of the excess air ratio, primary air ratio, coal particle size distribution, coal properties (ash content and volatile content) and Ca/S ratio on the boiler operation were analyzed. The results showed that the model simulation may be applied to the optimum design and economic operation of the CFB boiler.

Study on mathematical model of steam coal blending

It is necessary to set up a new mathematical model of steam coal blending instead of the old model. Indexes such as moisture content, ash content, volatile matter, sulfur content and heating value in the new mathematical model have linear relation. The new mathematical model can also predict ash-fusion temperature precisely by considering coal ash ratio in steam coal blending, therefore it is possible to obtain linear relation of ash-fusion temperature between single coal and steam coal blending. The new mathematical model can improve precision of steam coal blending and perfect the old mathematical model of steam coal blending.

Computational Modeling of Tangentially Fired Boiler (I) Models, Flow Field and Temperature Profiles

In this work, an Eulerian/Lagrangian approach has been employed to investigate numerically the flow characteristics, heat transfer and combustion in a tangentially fired furnace. The RNG (Re-normalization group) k-ε model and a new method for cell face velocity interpolation based on a non-staggered grid system are employed. To avoid pseudo-diffusion that is significant in modeling tangentially fired furnaces, attempts are made at improving the differential volume scheme. Some new developments on turbulent diffusion of particles are also taken into account. Thus, computational accuracy is improved substantially.

Paper Machine Influence on Industrial Energy System

In this paper, the influence of low power factor on electricity system and the influence of paper breaking on heat system are presented. For that, a mathematical model and a case study for a paper mill are realised. The electric mathematical model is based on the relations of energy losses in cables and in transformers as a function of power factor. The thermal mathematical model includes characteristic energy and efficiency of boiler depending on its load. Characteristic of efficiency is modeled by a quadratic dependence between fuel consumption and steam flow. In the case, study were estimated to reduce energy losses for factor neutral （0.92） against real power factor （0.75） for the electrical scheme of a paper machine. Analytical expression of the boiler characteristic and variation of boiler efficiency depending on its load were estimated, too.

Modelling and Simulation of tile 50 MWe CFBC Boiler

A general mathematical model of CFBC boiler by taking the 50 MWe Tsinghua CFBC boiler as the object is established. The model has some distinguished feature.Firstly,in order to describe the CFBC precisely, emphasis is paid to tak t the broad size distribution of feeding coal and bed inventory into consideration. Secondly, the employingiof cell model makes it possible to show the distribution of any interested variable inside furnace.Thirdly ,since partial aspects such as hydrodynamics,devolatilisation of coal, combustion of char and the formation and reduction of harmful substances are considered in detail, therefore the emission at the outlet of the furnace can be estimated. By using the model, simulation is carried out to predict the performance of the 50 MWe Tsinghua CFBC boiler for both design and off-design operation. The results are useful for designers and possible improvement of desian.

Computational Modelling of Retrofitting a Coal Fired Boiler Type OP-230 for Predicting NOX Reduction

This study focuses on a CFD modelling of biomass-derived syngas co-firing with coal in an older mid-sized PC-fired boiler of type OP-230 with low-emission burners on the front wall. The simulations were performed to determine whether the boiler can be retrofitted for the fulfilment of the prospective environmental protection regulations relating to levels of NO_X emissions. The improvement of the air staging via the dual-fuel technique was based on the indirect co-firing technology. The impact of two arrangements of dedicated syngas nozzles(below and above the existing coal burners), two syngas compositions and two heat replacements(5% and 15%) on the course of thermal processes in a furnace was tested. The reductions in NO_X emissions were predicted relative to the baseline when only coal is combusted. The highest reduction of about 38% was achieved with the syngas nozzles below the existing coal burners and 15% heat replacement. This arrangement of nozzles offers the residence time sufficient to co-fire coal with waste derived syngas. A lower reduction in NO_X emissions was obtained with the nozzles above the burners as the enlargement of local fuel rich zone near syngas injection becomes significant for 15% heat replacement. Results provide for the decreasing impact of methane content along with the increase of syngas heat input. The avoided CO_2 emissions through the syngas indirect co-firing with coal in the boiler are linear function of heat replacements.

Modeling Study of a New Circulating Fluidized Bi-BedBoiler Combustion System

This paper presents a set of general dynamic mathematical models for the combustion system of acirculating fluidized bi-bed boiler. The models fully consider the flow, combustion and heat transfercharacteristics, and describe the physical and chemical processes inside the bi-bed, including the gassolid flow, multiple particles combustion, gas chemical reactions, heat transfer and pressure balances,etc.

Three Dimensional Modeling of Pulverized Coal Combustion in a 600 MW Corner Fired Boiler

The three-dimensional code ESTET developed at the LNH has been used to predict the reactive flow in a 600 MW coal fired boiler. Assuming a no-slip condition between the gas and the coal, the equations for a gas-particle mixture can be written. The pulverized coal particle size distribution is represented by a discrete number of particle size groups determined by the measured fineness distribution. The combustion models taking into account the pyrolysis of the particle and the heterogeneous combustion of char have been validated using intensive measurements performed on the 600 MW utility boiler. Heat fluxes were measured along the walls of the furnace and satisfactory agreement between computation and measurements has been achieved in terms of maximum flux location and heat flux intensity. Local measurements of velocities using LDV probe, gas temperature and gas species concentrations were performed in the vicinity of one burner and compared with the computed variables. Again we have observed a good agreement between the computations and the measurements in terms of jet penetration, temperature distribution, oxygen concentration and ash content.

Analysis and Numerical Simulation Research of the Heating Process in the Oven

How to use the oven to bake delicious food is the most concerned problem of the designers and users of the oven.For this intent,this paper analyzed the heat distribution in the oven based on the basic operation principles and proceeded the data simulation of the temperature distribution on the rack section.Constructing the differential equation model of the temperature distribution changes in the pan when the oven works based on the heat radiation and heat transmission,based on the idea of utilizing cellular automation to simulate heat transfer process,used ANSYS software to proceed the numerical simulation analysis to the rectangular,round-cornered rectangular,elliptical and circular pans and giving out the instantaneous temperature distribution of the corresponding shapes of the pans.The temperature distribution of the rectangular and circular pans proves that the product gets overcooked easily at the corners and edges of rectangular pans but not of a round pan.