Evaluation on liquid film cavitation capacity in reverse Rayleigh step and cavitation suction effect in its mechanical seals

doi:10.11949/0438-1157.20200665

Abstract

Abstract:

Aiming at the Rayleigh step configuration, the finite element method is used to solve the Reynolds equation based on the JFO cavitation boundary conditions to establish a hydrodynamic lubrication numerical model. Film pressure and density ratio distributions of the Rayleigh step (RS) and reverse Rayleigh step (RRS) are compared. Liquid film cavitation capacity in RRS is evaluated under the different geometrical structures and operating conditions. Cavitation suction mechanism in the mechanical seal with RRS is developed and its sealing performance is comparably analyzed to evaluate the cavitation suction effect. The results show that cavitation occurs fully in the main groove zone of RRS under proper structure design with considering operation conditions, and its mechanical seal has good cavitation suction effect to achieve zero leakage or reverse suction of sealed medium.

Key words: reverse Rayleigh step, cavitation capacity, mechanical seal, cavitation suction effect, finite element method

摘要：

针对瑞利台阶构型，采用有限单元法基于JFO空化边界条件求解Reynolds方程，建立了流体动压润滑数值模型。对比了正向和反向瑞利台阶构型的液膜压力与密度比分布，评价了反向瑞利台阶构型在不同操作工况与结构参数下的液膜空化性能。阐释了反向瑞利台阶机械密封液膜空化抽吸机理并对比分析了其密封性能，评价了液膜空化抽吸效应水平。结果表明，结合操作工况在合理的结构设计下，反向瑞利台阶主槽区域可产生充分的液膜空化效应，从而使其机械密封具有良好的空化抽吸效应，可实现密封介质的零泄漏或反向抽吸。

关键词: 反向瑞利台阶, 空化性能, 机械密封, 空化抽吸效应, 有限单元法

CLC Number:

TH 117.2

MA Xuezhong,MENG Xiangkai,ZHANG Weizheng,PENG Xudong,DING Xuexing. Evaluation on liquid film cavitation capacity in reverse Rayleigh step and cavitation suction effect in its mechanical seals[J]. CIESC Journal, 2020, 71(12): 5715-5724.

马学忠,孟祥铠,张伟政,彭旭东,丁雪兴. 反向瑞利台阶构型液膜空化性能与机械密封空化抽吸效应评价[J]. 化工学报, 2020, 71(12): 5715-5724.

Figures/Tables 12

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参数	数值
静止表面宽度, b₀/mm	40
环境压力, p_a/Pa	1×10⁵
空化压力, p_c/Pa	4×10³
动力黏度, μ/(Pa?s)	0.8×10^-3
平行织构表面量纲一化因数, Λ_b	50
量纲一化静止表面长度, L₀	6
量纲一化主槽长度, L₁	5.25
量纲一化主槽宽度, B₁	0.5
量纲一化主槽深度, H₁	3
量纲一化进口长度, L₂	0.25
量纲一化进口深度, H₂	12
量纲一化堰区宽度, B₂	0.25
量纲一化堰区长度, L₃	0.25

参数	数值
静止表面宽度, b₀/mm	40
环境压力, p_a/Pa	1×10⁵
空化压力, p_c/Pa	4×10³
动力黏度, μ/(Pa?s)	0.8×10^-3
平行织构表面量纲一化因数, Λ_b	50
量纲一化静止表面长度, L₀	6
量纲一化主槽长度, L₁	5.25
量纲一化主槽宽度, B₁	0.5
量纲一化主槽深度, H₁	3
量纲一化进口长度, L₂	0.25
量纲一化进口深度, H₂	12
量纲一化堰区宽度, B₂	0.25
量纲一化堰区长度, L₃	0.25

参数	数值
密封环内半径, r_i/mm	47
动力黏度, μ/(Pa·s)	0.8×10^-3
环境压力, p_a/Pa	1×10⁵
空化压力, p_c/Pa	4×10³
量纲一化环境压力, P_a	1
量纲一化密封压力, P_o	1.5
量纲一化密封数, Λ_s	1000
量纲一化外半径, R_o	1.255
RS主槽圆周角, α/(°)	39
RRS量纲一化主槽内半径, R₁	1.043
RRS量纲一化主槽外半径, R₂	1.106
RS量纲一化主槽内半径, R₃	1.170
RS量纲一化主槽外半径, R₄	1.234
RRS量纲一化主槽深度, H₁	6
RRS 和 RS量纲一化进口深度, H₂	25
RS量纲一化主槽深度, H₃	5
RRS堰区圆周角, ?/(°)	6
RRS 和 RS进口圆周角, β/(°)	2

参数	数值
密封环内半径, r_i/mm	47
动力黏度, μ/(Pa·s)	0.8×10^-3
环境压力, p_a/Pa	1×10⁵
空化压力, p_c/Pa	4×10³
量纲一化环境压力, P_a	1
量纲一化密封压力, P_o	1.5
量纲一化密封数, Λ_s	1000
量纲一化外半径, R_o	1.255
RS主槽圆周角, α/(°)	39
RRS量纲一化主槽内半径, R₁	1.043
RRS量纲一化主槽外半径, R₂	1.106
RS量纲一化主槽内半径, R₃	1.170
RS量纲一化主槽外半径, R₄	1.234
RRS量纲一化主槽深度, H₁	6
RRS 和 RS量纲一化进口深度, H₂	25
RS量纲一化主槽深度, H₃	5
RRS堰区圆周角, ?/(°)	6
RRS 和 RS进口圆周角, β/(°)	2

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