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Li D.-B.,Academy of Electrical Power science | Zhang R.,Zhejiang Agriculture And forestry University
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2012

To perform a reburning modification of a boiler, with the help of a Fluent 6.3 software platform and by adopting a numerical simulation method, studied were the in-furnace gas flow field, temperature field and pollutant emissions characteristics before and after a reburning modification of a 220 t/h tangentially-fired boiler. Furthermore, the influence of the excess air ratio in the reburning zone on the reburning modification effectiveness was also investigated. The realizable k-ε and LES model were used as the turbulent flow model respectively and a comparison of the simulation results was conducted. A contrast and verification of the simulation results obtained by using the LES model with the on-the-spot test data were conducted, including the temperature field, component field and NO x. It has been found that the numerical simulation results obtained by using the LES model are in relatively good agreement with the test results. The calculated results show that after the reburning modification, the temperature distribution in the furnace is more uniform and a reduction atmosphere is formed around the reburning spout, leading to a drop of the NO x concentration. When the excess air ratio in the reburning zone is 0.90, the reburning effectiveness is deemed as the best one and in such a case, the NO x concentration at the outlet of the furnace will decrease by 33.87%. The simulation results obtained by using the LES model are more precise than those obtained by using the realizable k-ε model. Source


Ma S.-X.,Taiyuan University of Science and Technology | Ma Q.-Z.,Academy of Electrical Power science | Zhang L.-Y.,Academy of Electrical Power science
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2010

In the light of the great change in power grid frequency and the poor performance of primary frequency-modulation of the on-line units, the regulating system of an intermediate reheat steam turbine unit was redesigned to superimpose the frequency difference signal to the instructions for HP and IP regulating valve in the form of a feedforward signal to let the HP (High Pressure) and IP (Intermediate Pressure) regulating valve take part in the primary frequency modulation simultaneously. This makes it possible to fully use the heat stored in the intermediate reheat volume. The simulation results show that after the feedforward signals have been provided for the HP and IP regulating valve, the primary frequency modulation performance of the reheat steam turbine unit has been greatly improved with the load response ability being enhanced remarkably, retaining at the same time the stable performance of the regulation system. However, to realize feedforward signal control mode of the IP regulating valve still necessitates the completion of relevant research. Source


Gao J.-L.,Academy of Electrical Power science | Leng J.,Academy of Electrical Power science | Xu H.,Southwest Electrical Power Designing Institute | Wang S.-N.,Southwest Electrical Power Designing Institute
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2012

Experimentally studied was the influence of the dry type deslagging system of a 1000 MW unit in a power plant on the boiler efficiency. Through the test of the influence of the cooling air proportion on the boiler efficiency, the test of the influence of the rotating speed of the steel tape machine on the boiler efficiency, the dry type and wet type deslagging contrast test at the rated load and a low load, obtained was the extent of the influence of the dry type deslagging system on the boiler efficiency. It has been found that with an increase of the cooling air proportion, the boiler efficiency will gradually decrease. When the cold air proportion increases from 0.62% to 1.34%, the boiler efficiency will decrease by 0.22 percentage points. When the rotating speed of the steel tape machine increases from 2 m/min to 3.6 m/min, the boiler efficiency will go down by 0.06 percentage points. With an increase of the rotating speed of the steel tape machine, the boiler efficiency will gradually decrease. When the cooling air proportion is greater than 0.45%, the boiler efficiency by using the dry type deslagging mode will be lower than that by using wet type deslagging mode. Source


Zhu Y.-Q.,Academy of Electrical Power science | Chen S.-H.,Academy of Electrical Power science | Zhang M.,North University of China | Zeng D.-L.,North University of China
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2014

To realize the stable operation of large-sized ultra-supercritical units in a wide range at a variable load, adopted was a conception of the clearance measure. On this basis, the non-linear characteristics of a model for 1 000 MW ultra-supercritical units with three inputs and three outputs were analyzed. Bu adopting the K-mean clustering algorithm, the division of loads of the unit and the selection of its typical operating points were accomplished. By employing the small deviation linearization method, the linear models at each typical operating point were obtained and then, based on the H∞ loop formation, the corresponding robust controllers to each linearization models were designed. Finally, in combination with the fuzzy supervision and control, a fuzzy multi-model supervision and control version was given. The test and simulation results show that the design version of the controller under discussion can realize a quick tracking of the load of a ultra-supercritical unit, thus offering a new method for controlling a non-linear system. Source


Tian F.,Academy of Electrical Power science | Deng S.-X.,Academy of Electrical Power science | Han J.-F.,Academy of Electrical Power science | Xu R.,Academy of Electrical Power science
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2010

On the basis of an on-site test, studied were the bearing characteristics of a domestically-made 600 MW steam turbine during its slide pressure operation under single and sequence valve operation modes respectively. It has been found that the oil temperature on the thrust bearing pad facades and the return oil temperature of the supporting bearings operating under the sequence valve operation mode are generally higher than those operating under the single valve operation mode. The temperature variation of the bearing pad No.1 and 2 of the supporting bearings assume different characteristics. When the single valve operation mode is compared with the sequence valve one, due to its equilibrium steam distribution, the bearing pad temperature of the supporting bearings will undergo a small change with the load. The research results have laid a foundation for carrying out further research work in question. Source

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