变工况条件下汽轮机高压缸末级气动及强度性能研究

doi:10.12096/j.2096-4528.pgt.21105

摘要/Abstract

摘要：

采用单向流固耦合分析方法，对4种抽汽量(0%、8%、15%和20%)工况下的汽轮机高压缸末级气动和强度性能进行了数值研究，获得了末级变工况条件下的气动效率和动叶气动载荷分布。以气动载荷为边界条件，对包含叶顶汽封和叶根结构的末级动叶强度性能进行了分析，揭示了末级动叶的最大应力和变形量随抽汽量的变化规律。结果表明：随着抽汽量增大，高压缸末两级输出功率近似呈线性减小，20%抽汽量工况下末两级输出功率比设计工况(0%抽汽)降低了约44%；末级出口总温逐渐上升，20%抽汽量工况下末级出口总温比设计工况下高约10 ℃。抽汽量对叶顶和叶根汽封的泄漏特性影响显著，导致变工况时末级总-总等熵效率、反动度和叶栅出口汽流角沿叶高的分布产生变化，尤其是30%叶高以下区域，20%抽汽量时三者较设计工况的最大偏离量分别为3.8%、1.6%和2.4°。在离心力和气动力的作用下，设计工况时末级动叶的最大应力位于T型叶根进汽侧下倒圆处，叶顶最大变形量为0.443 mm，叶片最大应力和最大变形量均随抽汽量的增大近似呈线性减小。

关键词: 汽轮机, 气动性能, 叶片强度, 高压缸

Abstract:

Using the one-way fluid-structure interaction method, the aerodynamic and strength performance of the last stages in high-pressure cylinder of a steam turbine were numerically investigated at four extraction percentages (0%, 8%, 15% and 20% of the total mass flow rate in stages). The aerodynamic efficiency of last stages, as well as the aerodynamic loads on the blades, was obtained under design and off-design conditions. With the computed aerodynamic loads, the strength performance of the last rotor blade was analyzed, and the maximum stress and deformation in rotor blade at various conditions were derived. The results show that the power output of last two stages is nearly linearly decreased with the increase of extraction percentage. If the extraction percentage equals to 20%, the power output is reduced by 44% as compared with the design case. As the extraction percentage increases, the total temperature at last stage outlet is gradually increased. With 20% extraction rate, the total temperature at last stage outlet is increased by about 10 ℃ compared with the design case. The extraction rate has a significant influence on the leakage performance in the tip and hub labyrinth seals of last stage, resulting in the variations of total-total isentropic efficiency, reaction degree and outlet flow angle distributions along the spanwise direction in the off-design conditions. The influence region in the last stage is mainly existed within 30% blade span near hubs due to varied extractions. Compared with the original design case, the total-total isentropic efficiency, reaction degree and outlet flow angle in the last stage are varied by 3.8%, 1.6% and 2.4° at most as the extraction percentage varies from 0 to 20%. With the centrifugal and aerodynamic forces, the maximum stress in the last stage rotor blade is occurred at the upstream side bottom fillet of T-shape root, and the maximum displacement in blade tip is 0.443 mm. As the extraction percentage increases, the maximum stress and maximum displacement in last stage rotor blade are almost linearly decreased.

Key words: steam turbine, aerodynamic performance, blade strength, high-pressure cylinder

中图分类号:

TK 262

石红晖, 王海波, 曹蓉秀, 姚力, 晏鑫. 变工况条件下汽轮机高压缸末级气动及强度性能研究[J]. 发电技术, 2022, 43(6): 959-969.

Honghui SHI, Haibo WANG, Rongxiu CAO, Li YAO, Xin YAN. Research on Aerodynamic and Strength Performance of Last Stage in High-Pressure Cylinder of Steam Turbine Under Variable Working Conditions[J]. Power Generation Technology, 2022, 43(6): 959-969.

图/表 24

图1 高压缸末两级CFD计算模型

Fig. 1 CFD computational model for the last two stages in high pressure cylinder

表1 叶栅和汽封的主要几何参数

Tab. 1 Main geometrical parameters for blades and seals

叶栅	叶片数	叶高/mm	弦长/mm	汽封间隙/mm
S11	80	106.5	38	0.8
R11	64	110.5	50	0.8
S12	80	114.6	42	0.9
R12	64	118.3	59	0.9

图2 叶栅和汽封的计算网格

Fig. 2 Computational meshes for blades and seals

图3 CFD计算模型子午面视图

Fig. 3 Meridian view of CFD computational model

表2 CFD计算模型的边界条件

Tab. 2 Boundary conditions of CFD computational model

边界	设置(设计工况)
进口总压P_in/MPa	9.834
进口总温T_in/K	708.05
出口静压P_out/MPa	7.76
动、静叶栅交界面(1)(2)(3)	冻结转子
汽封-主通道交界面(4)(6)(8)(10)	一般连接
汽封-主通道交界面(5)(7)(9)(11)	冻结转子

表3 近壁面第1层网格距离无关性分析

Tab. 3 Independency analysis of the first mesh layer distance near wall

y_wall/mm	近壁面平均y⁺	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
0.01	70.6	0.905 8	747.08	2.037
0.005	33.1	0.904 9	746.06	1.897
0.0025	16.9	0.905 2	742.11	1.358
0.001	7.8	0.904 4	734.49	0.317
0.000 5	3.6	0.904 2	732.17	—

表3 近壁面第1层网格距离无关性分析

Tab. 3 Independency analysis of the first mesh layer distance near wall

y_wall/mm	近壁面平均y⁺	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
0.01	70.6	0.905 8	747.08	2.037
0.005	33.1	0.904 9	746.06	1.897
0.0025	16.9	0.905 2	742.11	1.358
0.001	7.8	0.904 4	734.49	0.317
0.000 5	3.6	0.904 2	732.17	—

表4 叶栅网格密度无关性分析

Tab. 4 Independency analysis for grid density of blades

节点数/万	y_wall/mm	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
490	0.001	0.902 3	734.87	0.204
710	0.001	0.904 4	734.49	0.152
1 049	0.001	0.904 9	733.95	0.079

表4 叶栅网格密度无关性分析

Tab. 4 Independency analysis for grid density of blades

节点数/万	y_wall/mm	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
490	0.001	0.902 3	734.87	0.204
710	0.001	0.904 4	734.49	0.152
1 049	0.001	0.904 9	733.95	0.079

表5 汽封网格密度无关性分析

Tab. 5 Independency analysis for grid density of seals

节点数/万	y_wall/mm	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
238	0.001	0.904 9	734.51	0.016
479	0.001	0.904 4	734.49	0.015
958	0.001	0.904 4	734.45	0.010

表5 汽封网格密度无关性分析

Tab. 5 Independency analysis for grid density of seals

节点数/万	y_wall/mm	$η i t$	$m ˙$ /(kg·s^-1)	相对偏差/%
238	0.001	0.904 9	734.51	0.016
479	0.001	0.904 4	734.49	0.015
958	0.001	0.904 4	734.45	0.010

图4 高压缸末级动叶-轮盘FEA计算模型

Fig. 4 FEA computational model for the last stage rotor blade-disk in high pressure cylinder

表6 2Cr13在400 ℃下的主要力学性能参数

Tab. 6 Main mechanical property parameters of 2Cr13 at 400 ℃

参数

弹性模量/

MPa

泊松比

密度/

(kg·s^-3)

屈服强度

σ 0.2

表6 2Cr13在400 ℃下的主要力学性能参数

Tab. 6 Main mechanical property parameters of 2Cr13 at 400 ℃

参数

弹性模量/

MPa

泊松比

密度/

(kg·s^-3)

屈服强度

σ 0.2

/MPa

数值

1.99×10⁵

0.337

7 750

735

图5 叶片-轮盘FEA计算网格

Fig. 5 FEA computational meshes for blade-disk

图6 FEA计算模型边界条件及载荷

Fig. 6 Boundary conditions and loads for the FEA computational model

表7 高压缸末两级变工况总体参数

Tab. 7 Overall parameters of final two stage variable conditions of high-pressure cylinder

工况	P_in/MPa	T_out/K	$m ˙$ /(kg·s^-1)	$P ˙$ /MW	功率占比/%
设计工况	9.834	673.44	738.93	45.36	100
8%抽汽	9.549	676.82	680.18	36.95	81.46
15%抽汽	9.305	680.63	628.22	30.05	66.24
20%抽汽	9.135	683.42	591.30	25.45	56.11

表7 高压缸末两级变工况总体参数

Tab. 7 Overall parameters of final two stage variable conditions of high-pressure cylinder

工况	P_in/MPa	T_out/K	$m ˙$ /(kg·s^-1)	$P ˙$ /MW	功率占比/%
设计工况	9.834	673.44	738.93	45.36	100
8%抽汽	9.549	676.82	680.18	36.95	81.46
15%抽汽	9.305	680.63	628.22	30.05	66.24
20%抽汽	9.135	683.42	591.30	25.45	56.11

图7 20%抽汽工况下汽封泄漏引起的二次流子午面流线

Fig. 7 Secondary flow meridian streamlines caused by steam steal leakage under 20% extraction condition

图8 总-总等熵效率沿叶高的分布

Fig. 8 Total-total isentropic efficiency distributions along spanwise direction

图9 反动度沿叶高的分布

Fig. 9 Reaction degree distributions along the spanwise direction

图10 叶栅出口汽流角沿叶高的分布

Fig. 10 Blade outlet flow angle distributions along the spanwise direction

图11 离心力单独作用时叶片和轮盘应力分布

Fig. 11 Stress distributions in blade and disk with only centrifugal force

图12 设计工况下FEA和CFD交界面上参数分布

Fig. 12 Parameter distributions on the interface between FEA and CFD domain under design condition

图13 离心力、气动力作用时叶片和轮盘应力分布

Fig. 13 Stress distributions in blade and disk with both centrifugal force and aerodynamic force

图14 加载气动力前后的叶片变形位移分布(放大50倍)(a) 只有离心力 (b) 离心力和气动力

Fig. 14 Deformation displacement distributions of blade before and after loading aerodynamic force (magnify 50 times)

图15 叶片、轮盘高应力区位置及编号

Fig. 15 Position and number of high stress area in blade and disk

表8 变工况叶片、轮盘关键部位的应力 (MPa)

Tab. 8 Stress of key parts of blade and disk under variable conditions

工况	位置①	位置②	位置③	位置④	位置⑤	位置⑥
设计工况	236.8	289.1	391.4	214.2	420.7	379.5
8%抽汽	238.7	283.0	375.2	207.7	408.7	374.4
15%抽汽	240.1	278.9	361.2	202.1	398.4	370.0
20%抽汽	240.9	276.2	351.2	198.1	390.9	366.8

表9 变工况叶片顶部最大变形位移 (mm)

Tab. 9 Maximum deformation displacement of blade tip under variable conditions

工况	径向	切向	轴向	总位移
设计工况	0.212	0.029	0.400	0.443
8%抽汽	0.206	0.028	0.363	0.408
15%抽汽	0.200	0.027	0.331	0.379
20%抽汽	0.196	0.027	0.308	0.358

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