Applied Mechanics and Materials Vols. 672-674

Abstract: Abstract. Thermal efficiency is an economical operation index of industrial boilers. There are many factors influencing thermal efficiency. It is difficult to keep the boiler in high efficient operation just using single automatic control method when environment has been changed. Therefore, the control of combustion systems is usually depended on artificial experience. To improve this situation, an operation optimization method is proposed. An identification model which can reflect the thermal efficiency is established by using principal component analysis based on historical data. When the boiler’s operation efficiency decreases, the parameters of influencing boiler efficiency can be directly got by contribution plot method, which can guide operators in real-time to adjust these parameters maintaining boiler efficient operation. Abstract. Thermal efficiency is an economical operation index of industrial boilers. There are many factors influencing thermal efficiency. It is difficult to keep the boiler in high efficient operation just using single automatic control method when environment has been changed. Therefore, the control of combustion systems is usually depended on artificial experience. To improve this situation, an operation optimization method is proposed. An identification model which can reflect the thermal efficiency is established by using principal component analysis based on historical data. When the boiler’s operation efficiency decreases, the parameters of influencing boiler efficiency can be directly got by contribution plot method, which can guide operators in real-time to adjust these parameters maintaining boiler efficient operation.

Abstract: In view of rich resources of corn stalks, cotton stalks forming pellets hot ignition performance, using CFD numerical simulation analysis to study the key parameters of electric ignition such as the surface ignition temperature, air velocity, air flow distribution ratio of influence of hot air outlet temperature. Obtained that increasing electric heating surface temperature, reducing the air flow velocity and convective heat transfer coefficient of the outer tube can significantly improve the ignition temperature of the outlet hot air, the outlet hot air temperature should be higher than 450 °C. Ignition internal and external air passage area ratio affects the allocation of hot air flow, the best area ratio of between 1.8-2.2.

Abstract: The basic characteristics of natural gas with low oxygen air combustion is analyzed, and low oxygen content, excess air ratio, and the change of flue gas composition are studied, the results show that using the technology of low oxygen air combustion for glass tempering furnace in production has directive significance. The composition content of carbon dioxide and water vapor increases in the combustion products. The radiation heat transfer is decreased in glass tempering furnace. The furnace temperatures are maintained in the range of 650 to 800°C.

Abstract: In this paper, the conversion process and the existing forms of mercury in the course of coal firing are first analyzed, and different methods to measure mercury are introduced; To assess the mercury emission levels of boilers in large power plants, through testing the mercury content in combustion products of the boiler in 700 MW unit under different loads in one power plant of Jiangxi Province, we analyzed the formation distribution of mercury emissions and the effect of low temperature economizer on the mercury concentration before and after the ESP, and acquired the mercury emission characteristics of 700 MW boiler. In study, we found that mercury in the coal burnt in 700 MW boiler was mainly discharged in the form of gas, with a small amount existing in burnt solids. The change of gaseous mercury before and after the ESP is not obvious, but the concentration of bivalent mercury is higher than that of zero-valent mercury; and more than 90% of the particulate mercury is removed. The low temperature economizer in operation can obviously reduce the concentration of mercury in flue gas at the ESP outlet by 30.8%.

Abstract: Introduces the concept of the heat metering and charging regulation coefficient, describes its’ calculation and the procedures of regulation, also summarizes the calculate formulas. and analyzes the effect of heat transfer between adjacent units on household heat metering, as well as the influence of different floor and different position in a building, different orientation, the area of window contrast to wall, cold wind infiltrating and the natural capacity of heat preservation of surrounding structure and so on. According to the Heating Company, Heating price is 0.14 yuan/kWh. Heat cost consists of two. One is basic cost,the other is changed cost. The proper temperature being on duty is probably 7°C when there is heat transfer between adjacent units. When nobody lives in the rooms, some cost must be paid. Also introduces the concept of the metering and charging regulation coefficient, describes its calculation and procedures of regulation.

Abstract: With the use of computational fluid mechanics software – FLUENT, the numerical simulation computation of combustion process inside a certain 200MW corner tangential firing boiler whose combustor is transformed by the multi-grade efficient low-nitrogen combustion technology was conducted, thus the furnace temperature, velocity, mixture and NOx concentration field at rated conditions before and after the transformation were obtained. The calculation results were highly identical with the industrial test results. The results show that after using the multi-grade efficient low-nitrogen combustion technology, the NOx emissions significantly lowered down with the drop of about 40% compared with the emissions before transformation, while the furnace coking and high temperature corrosion were effectively controlled, achieving good economic and social benefits and providing a reference to the design and transformation of the same types of boilers.

Abstract: Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed. The active clearance control (ACC) of aero-engine turbine tip clearance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis. The results show that the resultant active tip clearance control system has favorable steady-state and dynamic performance and benefits of increased efficiency, reduced specific fuel consumption, and additional service life.

Abstract: The new wave-energy dynamoelectric equipment has small volume and its transportation is very relaxed for application in the wide ocean area etc. So it has certain competitive power and enhanced researching value. After analyzing the structure of the equipment, it is found that the displacement difference between the floater and reducing-velocity structure validates feasibility and efficiency of the equipment. In this paper, the displacement difference is mainly researched. At first, forces on the upper and lower parts are analyzed respectively. Then investigating their movements, some structural parameters are determined. At the same time, the problem that the discontinuous acceleration change of the movement of the reducing-velocity structure causes the impulsion to the whole equipment is found. In order to solve the problem, the solution that a spring is added to the connecting string is adapted. The improved equipment is checked and finally it is found feasible.

Abstract: TX1600 boring and milling machining center milling part was studied. The Three-dimensional solid model was established based on Solidworks. Simultaneously, modal analysis was carried out by ANSYS Workbench software, the first six natural frequencies and corresponding modes were acquired. Based on the modal analysis, the harmonic response analysis of milling part was conducted,and the response curves of the three main motion orientation were obtained respectively, the vibration performance of milling part under forces was further explored,and the finite element model was validated. The feasibility of the model to simplify the program was verified by modal and harmonic response analysis. The study provides a good basis in terms of selecting a specific material. The structures and material are optimized. Ultimately, a lot of energy is saved.

Abstract: Due to the fact that the low speed pump similarity theory is only applicable to incompressible fluid, this theory cannot be used for extrapolation of compressor performance curve. Considering the compressibility of working medium; therefore, this paper has modified the similarity theory and put forward a new index relationship equation. The two low speed performance lines which are already known were used to get the similar working points and extrapolate the performance lines through the optimization method. Compared with the existing performance lines, the results show that the method is simple, convenient and qualified with practicability and accuracy. This method plays an important role on studying startup process of a gas turbine and improving the accuracy of the simulation of startup process.