Abstract: Huaneng Shantou Power Plant No. 1 turbine under the rated parameters and rated load Bearing No. 1 bearing temperature is too high. The main reason is that the bearing to withstand excessive load, some oil thinning, causing the temperature rise. Can change the control valve opening difference to solve the problem of bearing temperature is too high? The test study confirmed that the valve opening difference between the bearing temperature and the relationship. By reducing the control valve opening difference, can reduce the bearing load, thereby properly increasing the thickness of the oil film to reduce the bearing temperature. In practice, the use of change 3, 4 valve opening difference is the exchange of 3, 4, the opening of the control valve approach to the No. 1 bearing temperature problem is solved, spend less, quick. Steam turbine; Bearing load; Bearing temperature; Opening degree of control valve; Opening sequence Huaneng Shantou Power Plant No.1 steam turbine with a capacity of 300 MW is a Russian product, model K-300-170-3, Subcritical reheat condensing intermediate once. Turbine a total of five bearings, in addition to No. 2 bearing thrust - support joint spherical self-aligning sliding bearings, bearings are all other fixed sliding bearings, all bearing materials for the tin-based Babbitt alloy. During the trial operation of the unit at the end of 1996, it was found that the temperature of the bearing pad at the rear of No. 1 bearing of this unit was 95 ~ 102 ℃ under the rated parameters and rated load. Other bearing temperature is below 75 ℃. After the middle of the No. 1 bearing block the middle of the oil drain plugged a quarter, an increase bearing bearing area, No. 1 bearing temperature dropped to 90 ~ 92 ℃, the tile temperature is still too high. Open No. 1 bearing inspection and found that the rear bearing obvious signs of friction. The main reason for the high temperature of the bearing pad is due to the fact that the design of the manufacturer neither considers the self-aligning bearing where appropriate bearing capacity is adopted, nor does it take into account the external forces that cause additional forces on the bearing and the change of the shaft end angle Affect, causing the bearing to withstand excessive load, causing the temperature rise. The author has made a theoretical discussion on the relationship between the difference between the opening degree of the steam turbine governing valve and the bearing load and the bearing temperature. It is found that for the steam turbine with reaction, the opening difference (including the opening sequence) of the regulating valve is not the same as the steam thermodynamic performance And the throttling of the state have an impact, but also with the bearing load, shaft deflection, shaft end angle, the bearing film thickness and the relationship between the bearing temperature, and the valve opening difference caused by the role of the additional load on the bearing into Proportional relationship (due to space limitations, not repeat them here). To solve the bearing design due to improper factors such as bearing temperature and oil film oscillation problems, within a certain range, you can change the control valve opening difference to reduce the bearing load or pressure and shaft angle to start. 1, the control valve opening difference between the bearing film thickness and bearing temperature relationship between According to the lubrication theory, for dynamic pressure type sliding bearing, if the bearing load is too light, the bearing oil film is too thick, the oil film is prone to instability and oil film oscillation occurs; if the bearing Heavy load, easy to rupture of the oil film and shaft bearings and local dry friction caused by bush temperatures. In order to make the bearing oil film not too thick and not too thin, that does not occur oil film shock nor too high bearing temperature, it is necessary to find out the film thickness and bearing load and other parameters between the relationship. Figure 1 shows the radial bearing geometry. From Figure 1, we can get the bearing vertical component F = μ × v × B × Fy / Ψ2, (1) F - the bearing vertical component, N; μ - the absolute viscosity of lubricating oil, MPa · s; - Relative clearance of the bearing, Ψ = C / R, mm; C - Radial clearance of the bearing, C = Rr, mm; R - Radius of the bearing, in mm; r - Radius of the journal, in mm; Working length, mm; v-- journal peripheral speed, v = Rω, mm / s; Fy-- Bearing bearing factor; ω-- journal angular velocity, rad / s. Figure 1 radial bearing geometric relationship between the minimum film thickness hmin = Ce, (2) hmin - the minimum film thickness, mm; e - journal eccentricity in the bearing center, mm. The above formula into the (1) type, the appropriate rectification F - bearing load, F = F0 + FB, N; F0 - bearing the original load, N; FB - caused by the valve opening difference caused by the load N From the control valve opening difference and the role of the bearing on the additional load proportional relationship, so that FB = ΔH / a, where ΔH is the valve opening difference, a is the scale factor, then F = F0 + ΔH / a, and substituted (3), the formula (4) reveals the relationship between the bearing oil film thickness hmin and the control valve opening degree difference ΔH. Under the certain bearing parameters Fy, μ, ω, R, B and other parameters, The larger the smaller the hmin, the smaller the ΔH, the larger the hmin. For the bearings and journal between the film is too thin caused by the temperature of the bearing high, the general solution is to increase the bearing width B, adjust the load distribution of bearings, or replace self-bearing to adapt to excessive shaft deflection and shaft End corner. These measures involve the need to change the type of bearing structure or bearing installation, the workload, cost more. The use of changing the valve opening difference method can reduce the valve opening difference ΔH, its purpose is to reduce the bearing load FB, and then reduce the total bearing load F, the appropriate increase in film thickness and reduce the shaft angle, reduce the bearing temperature . As the theoretical calculation of the existence of errors, the film thickness is not easy to measure directly, so the best valve opening difference ΔH, the best test to determine. 2, the opening degree difference and the bearing temperature test In order to confirm whether to change the valve opening difference to reduce Huaneng Shantou Power Plant 1 No. 1 turbine bearing temperature, the unit with 70% and 100% rated load conditions, On the 3rd, 4th control valve opening difference between the different and No. 1 bearing temperature between the test carried out (on the 1st and 2nd control valve are maintained fully open state, the opening difference is 0). The experimental data are shown in Table 1 and Table 2, respectively. Table 1 No. 3, No. 4 valve opening difference with the No. 1 bearing temperature relationship (with 70% of the rated load) Table 2 No. 3, No. 4 valve opening difference and No. 1 bearing temperature (with 100% rated load) According to Table 1 and Table 2 test data, you can draw No. 3, No. 4 valve opening difference ΔH3, 4 and No. 1 bearing temperature t1 between the curve, shown in Figure 2, Figure 3. Figure 2 70% of the rated load, ΔH3,4 and t1 relationship curve test curve 3 100.0% of the rated load, ΔH3,4 and t1 relationship curve from Figure 2, Figure 3 shows, No. 1 bush temperature and No. 3, On the 4th control valve opening difference is almost linear, that is, the greater the ΔH3,4, the first bearing temperature t1 is higher, and vice versa. According to the change of No. 1 bearing temperature and the difference of the opening degree of the No. 3 and No. 4 regulating valves, the method of reducing the difference of the opening degree of the regulating valve is adopted to the problem of the high temperature of No. 1 bearing bush, that is, the No. 3 and No. 4 adjustment Valve to open the order, that is, first opened on the 4th, after opening on the 3rd method. In this way, the original ΔH3,4 positive, by changing the opening sequence, ΔH3,4 negative. In order to ensure the control valve characteristics are not affected, the No. 3, No. 4 regulating valve oil motivation and other related components swap. 3, the effect According to this method to improve the temperature of No. 1 bushings from 92 ℃ down to 65 ℃ stable operation. Bearing vibration changes little, there is no case of oil film oscillation. At the same time, because the replacement of No. 3, No. 4 valve opening sequence, ΔH3,4 from the positive to negative, but the absolute value of the opening has not changed (that is, the valve opening overlap did not increase ), Did not bring additional throttling loss. Practice has proved that the use of changing the control valve opening difference and open the order of the way, the No. 1 bearing temperature problem is solved, spend less, quick, and achieved significant economic benefits. References [1] Qiao Xiao Chun, Niu Xi Chuan, Zhen Zhennan, mechanical design [M]. Xi'an: Xi'an Jiaotong University Press, 1986 [2] Shandong Electric Power School. Steam turbine equipment and operation [M]. Beijing: Electric Power Industry Press , 1979 [3] Zhu Long root. Concise mechanical parts design manual [M] Beijing: Mechanical Industry Press, 1997
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