环境因素影响下火电直接空冷系统性能研究

发布时间：2018-03-03 20:17

本文选题：直接空冷凝汽器　切入点：轴流风机群　出处：《华北电力大学》2014年博士论文　论文类型：学位论文

【摘要】：近年来,空冷技术在我国北方火力发电中得到了大力的发展。环境因素与火电直接空冷机组的耦合比较复杂,环境风速与风向、环境温度以及轴流冷却风机的性能等因素都对火电直接空冷机组性能产生影响,并且受轴流风机群运行中的群抽效应和环境风影响下的热风回流的耦合影响,轴流风机群外围的空冷凝汽器单元受环境风影响大。在四台联建火电直接空冷机组上进行了春、夏与秋三个季节不同工况下的机组热力性能实验,并在夏季主导风向下,基于两台联建火电直接空冷机组的轴流风机群分区调节的基础上,进行了不同工况下的机组热力性能实验。然后建立火电直接空冷机组性能的灰关联度模型,定量分析火电直接空冷机组自身运行实验变量与环境条件以及轴流风机群各风机的性能对火电直接空冷系统性能的影响,并基于上述两个热力性能实验数据,分别应用神经网络(ANN)与最小二乘支持向量机(LS-SVM)等算法,建立汽轮机背压预测模型。接着,在选定的基准工况下应用火电直接空冷机组汽轮机背压LS-SVM预测模型,分析出处于夏季主导风向下的轴流风机群不同分区风机转速降低和升高对环境风下游与上游火电直接空冷机组抵御环境风影响的作用规律。建立由太阳辐射引起的直接空冷系统附加热负荷计算模型,对太阳辐射影响空冷凝汽器热负荷的程度进行分析。基于火电直接空冷机组热力性能实验数据,应用建立的火电直接空冷机组性能灰关联度模型进行分析,结果显示出,文中选定的机组自身运行与环境实验变量对火电直接空冷机组的性能影响不同,并且处于不同位置的轴流冷却风机的性能对火电直接空冷机组性能的影响也不同,处于外围的轴流冷却风机的性能对火电直接空冷机组性能的影响最强烈。以北方地区某135MW火电直接空冷机组凝汽器的全年太阳辐射量为主线,假定汽轮机排汽量不变,环境温度为月平均日温度,揭示出由太阳辐射引起的月平均附加热负荷在1-5月期间升高,5月时达到最大值,为371.75kW,而后逐步降低,与日照时数的变化趋势基本一致。假定方位角为零时,凝汽器由太阳辐射引起的月平均附加热负荷增加而导致汽轮机背压升高,1-7月间汽轮机背压变化增加,7月时达到最大值,为0.2097kPa,8-12月相应的影响会减弱,与环境温度的变化趋势大致相同,并且由太阳辐射引起的直接空冷系统附加热负荷平均占空冷凝汽器总热负荷的0.134%。基于LM-BP算法,建立火电直接空冷机组的汽轮机背压ANN预测模型,其预测值与汽轮机背压的真实值基本一致,模型的平均相对误差,MRE,为9.27%；平均均方差,RMSE,为1.827kPa；绝对变异分数,R2,为0.9859。为检测模型的鲁棒性与可靠性,分别将空冷凝汽器的环境输入变量,如自然环境风速、自然环境风向、空冷岛挡风墙上环境风速和空冷岛挡风墙上环境风向等参数,加入±5%的随机波动后,输入到模型中,其MRE分别为14.57%,12.21%,11.22%和11.16%,RMSE分别为2.773,2.130,1.844和1.895kPa,R2分别为0.9641,0.9779,0.9836和0.9824,说明模型的稳定性很好,数据波动产生的相对误差能得到有效的抑制。针对夏季主导风向下的两台联建火电直接空冷机组,分别建立相应的汽轮机背压LS-SVM预测模型,讨论轴流风机群不同分区风机转速降低与升高时,轴流风机群环境风下游与上游火电直接空冷机组汽轮机背压的变化规律：(1)轴流风机群不同分区的轴流冷却风机转速发生变化时,汽轮机背压变化明显不同；(2)改变其中一台机组轴流冷却风机的转速,也会对另一台机组的汽轮机背压产生影响；(3)单纯提高轴流冷却风机转速并非总能够起到降低机组汽轮机背压的效果,适当降低受热风回流影响较大分区的轴流冷却风机转速,反而可以起到降低轴流风机群环境风下游机组汽轮机背压的作用,并且轴流风机群环境风上游机组汽轮机背压也不会升高。
[Abstract]:In recent years, air cooling technology has been developed vigorously in the north of China's thermal power plants. The coupling of direct air cooling unit of environmental factors and the power is more complex, the environment of wind speed and wind direction, the ambient temperature and the axial cooling fan performance and other factors of the direct air cooling unit of thermal power can affect the coupling effect of hot air reflux and axial flow fan cluster in the operation group pumping effect and environmental wind under the influence of the axial flow fan cluster outside condenser unit by environmental wind influence.
The spring in four the construction of thermal power direct air cooling unit, summer and autumn three seasons under different conditions of the thermal performance of the unit test, and in the summer the dominant wind direction, based on the construction of two units of power direct air cooling unit axial flow fan cluster partition adjustment on the thermodynamic performance experiments under different conditions the grey correlation model. Then establish the power performance of direct air cooling unit, quantitative analysis of the influence of thermal performance of direct air-cooled unit operation and environmental conditions as well as the experimental variable axial flow fan cluster the fan on the performance of the power of the direct air cooling system, and based on the two thermal performance experimental data were used to neural network (ANN) and least squares support vector machine (LS-SVM) algorithm, the establishment of the steam turbine back pressure prediction model. Then, using the power of direct air-cooled unit steam turbine back pressure LS-SVM in the benchmark under the selected conditions Prediction model, analysis of provenance in the summer the dominant wind direction under different axial flow fan cluster partition fan speed decreased and increased effect of wind withstand environmental impact on the environment downstream and upstream wind power direct air cooling unit. Calculation model of direct air cooling system of heating load caused by solar radiation, the solar radiation influence space the condenser heat load is analyzed.
The power of direct air-cooled unit thermal performance based on experimental data were analyzed using the established power direct air cooling unit properties of grey correlation model, results show that the performance of the selected unit operation and environment experimental variables on the thermal power of direct air cooling units and different effects in the performance flow cooling fan in different positions the axial thermal effect of direct air cooling unit performance is different, in the performance of the cooling fan shaft of the thermal effect of the periphery of the direct air cooling unit performance most strongly.
In the northern region of a 135MW power direct air cooling condenser of the annual amount of solar radiation as the main line, assuming that steam turbine exhaust quantity, ambient temperature for monthly average daily temperature, revealing the radiation caused by the sun's monthly average of the heating load increased in 1-5 during the month of May, reached the maximum value is 371.75kW, then sunshine and gradually reduce the trend change is consistent. We assume that the azimuth angle is zero, the condenser from solar radiation caused by the monthly average of the heating load increase caused by steam turbine back pressure, increase the steam pressure change in 1-7 months, in July reached the maximum value for 0.2097kPa, 8-12 month corresponding effect will be weakened. Roughly the same as the trend of environmental temperature, radiation and direct air cooling system of heating load caused by the average duty total heat load of condenser 0.134%. by the sun
Based on the LM-BP algorithm, the power of direct air cooling unit of steam turbine back pressure ANN prediction model, the prediction value and the real value of the steam turbine back pressure is basically the same, the average relative error of the model, MRE, 9.27%; average variance, RMSE, 1.827kPa; the absolute variation fraction, R2, robustness and reliability of 0.9859. detection model the environmental input variables are the condenser, such as natural environment, natural environment of wind direction, wind speed, air cooling island wind wall wind and air cooling island wind wall environment, wind direction and other parameters, random fluctuations add + 5%, input to the model, the MRE were 14.57%, 12.21%, 11.22% and 11.16% RMSE, 2.773,2.130,1.844 and 1.895kPa respectively, R2 0.9641,0.9779,0.9836 and 0.9824 respectively, indicating the stability of the model is very good, the relative error data fluctuation can be effectively suppressed.
In summer two the construction of leading power direct air cooling unit under the wind direction, establish the corresponding steam turbine back pressure LS-SVM prediction model, the discussion of axial flow fan cluster in different zones of fan speed and reduce the rise, variation of axial flow fan cluster environment downstream wind and upstream power direct air cooling unit steam turbine back pressure: (1). Axial flow fan cluster partition of different flow cooling fan speed change when the steam pressure changes were significantly different; (2) the change of one unit of axial cooling fan speed, but also the other units of the steam turbine back pressure generating effect; (3) improve speed of the machine is not always able to play to reduce the effect of back pressure steam turbine axial flow cooling fan, appropriate to reduce the influence of hot air recirculation by the partition of the axial cooling fan speed, it can reduce the axial flow fan cluster environment wind downstream unit steam turbine backpressure It does not increase the back pressure of the steam turbine in the axial-flow wind turbine group.

【学位授予单位】：华北电力大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM611

【参考文献】