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柔性箔片气膜密封实际表面状态下的声发射信号特征

王学良, 陈金鑫, 陆俊杰, 张炜, 蒋敏, 吴雪静, 吴磊波

王学良, 陈金鑫, 陆俊杰, 张炜, 蒋敏, 吴雪静, 吴磊波. 柔性箔片气膜密封实际表面状态下的声发射信号特征[J]. 摩擦学学报, 2023, 43(11): 1319-1329. DOI: 10.16078/j.tribology.2023224
引用本文: 王学良, 陈金鑫, 陆俊杰, 张炜, 蒋敏, 吴雪静, 吴磊波. 柔性箔片气膜密封实际表面状态下的声发射信号特征[J]. 摩擦学学报, 2023, 43(11): 1319-1329. DOI: 10.16078/j.tribology.2023224
WANG Xueliang, CHEN Jinxin, LU Junjie, ZHANG Wei, JIANG Min, WU Xuejing, WU Leibo. Variation of Surface Roughness on Acoustic Emission Signal Characteristics of Compliant Foil Gas Seal[J]. TRIBOLOGY, 2023, 43(11): 1319-1329. DOI: 10.16078/j.tribology.2023224
Citation: WANG Xueliang, CHEN Jinxin, LU Junjie, ZHANG Wei, JIANG Min, WU Xuejing, WU Leibo. Variation of Surface Roughness on Acoustic Emission Signal Characteristics of Compliant Foil Gas Seal[J]. TRIBOLOGY, 2023, 43(11): 1319-1329. DOI: 10.16078/j.tribology.2023224
王学良, 陈金鑫, 陆俊杰, 张炜, 蒋敏, 吴雪静, 吴磊波. 柔性箔片气膜密封实际表面状态下的声发射信号特征[J]. 摩擦学学报, 2023, 43(11): 1319-1329. CSTR: 32261.14.j.tribology.2023224
引用本文: 王学良, 陈金鑫, 陆俊杰, 张炜, 蒋敏, 吴雪静, 吴磊波. 柔性箔片气膜密封实际表面状态下的声发射信号特征[J]. 摩擦学学报, 2023, 43(11): 1319-1329. CSTR: 32261.14.j.tribology.2023224
WANG Xueliang, CHEN Jinxin, LU Junjie, ZHANG Wei, JIANG Min, WU Xuejing, WU Leibo. Variation of Surface Roughness on Acoustic Emission Signal Characteristics of Compliant Foil Gas Seal[J]. TRIBOLOGY, 2023, 43(11): 1319-1329. CSTR: 32261.14.j.tribology.2023224
Citation: WANG Xueliang, CHEN Jinxin, LU Junjie, ZHANG Wei, JIANG Min, WU Xuejing, WU Leibo. Variation of Surface Roughness on Acoustic Emission Signal Characteristics of Compliant Foil Gas Seal[J]. TRIBOLOGY, 2023, 43(11): 1319-1329. CSTR: 32261.14.j.tribology.2023224

柔性箔片气膜密封实际表面状态下的声发射信号特征

基金项目: 浙大宁波理工学院人才引进基金项目(20220913Z0210)、宁波市自然科学基金项目(2023J271)和宁波市科技创新2025重大专项(2022Z005, 2022Z007, 2023Z009)资助.
详细信息
  • 中图分类号: TH136

Variation of Surface Roughness on Acoustic Emission Signal Characteristics of Compliant Foil Gas Seal

Funds: This project was supported by Tanlent Introduction Found Project of NingboTech University (20220913Z0210), Ningbo Natural Science Found Project (2023J271) and Ningbo 2025 S&T Megaprojects (2022Z005, 2022Z007, 2023Z009).
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  • 摘要:

    柔性箔片气膜密封技术是1种先进的非接触式柱面气膜密封技术,可满足极端参数下高性能旋转机械的密封需求,然而该柱面密封结构不同表面状态运转下的信号特征规律较少研究. 因此,本文中通过搭建密封试验台采集不同表面状态下的AE信号频率,进而利用AE波形图和傅里叶变换对其不同表面状态下AE特征规律进行分析与探讨, 对比获得不同压力、转速以及膜厚变化时的AE频率特征,从而确定AE信号与气膜密封表面状态相关的幅频信息. 结果分析表明:不同表面状态下,AE信号特征频率呈现中心幅频特征不同,且柔性箔片气膜密封结构的AE信号特征至少存在两种明显的中心频率变化,这是由柔性箔片气膜密封的楔形间隙结构变化导致;另外,当密封试验压差和转速变化时,AE频率特征发生了一定程度的变化,但AE中心频率分布基本不变;最后,由于AE高频信号会随着膜厚增加发生衰减,相同表面状态在不同膜厚下呈现出不同的AE频率特征.

    Abstract:

    Compliant foil gas seal technology is one of the advanced non-contact cylindrical gas film seal technology. Under extreme operation parameters, including high boundary velocity, high differential pressure, high vibration and high temperature, the compliant foil gas seal can meet the requirements of high performance rotary machines. However, there is less research on the dynamic signal characteristics mechanism of compliant foil gas seal technology with different surface roughness running. Therefore, the acoustic emission signal characteristics with different surface roughness were collected from acoustic emission source of gas seal rig, which was firstly constructed. Then, the acoustic emission signal characteristics with different surface roughness were extracted and further discussed by making use of the waveform diagram and Fast Fourier Transform. The acoustic emission frequency characteristics were applied and analyzed with the variation of different surface roughness, differential pressure, boundary velocity and film thickness, in order to obtain the information of the amplitude frequency and acoustic emission frequency characteristics. The results showed that the frequency characteristics of acoustic emission signal on different surface characteristics were significantly different, especially in the surface roughness. In addition, there were obviously at least two center frequency distribution of the acoustic emission signal characteristics of compliant foil gas seal system. The phenomenon was probably caused by the variation of the wedge gap structure of cylindrical structure gas seal, which was the operating principle of compliant foil gas seal. Furthermore, with the variation of the differential pressure and velocity in this paper, the acoustic emission frequency distribution changed, but the acoustic emission center frequency distribution hardly changed. Finally, the frequency distribution of acoustic emission signal characteristics with same surface roughness of the film thickness was different. It was on account of the rapidly decrease of high frequency characteristics with the increase of film thickness.

  • 由于气浮支承接近于零摩擦和发热低等特点而广泛应用于超精密机械中[1],而气浮支承有限的刚度、承载能力及动态性能限制了其发展[2-3]. 随着机电一体化技术的快速进步,压电主动控制技术已经成为提高气浮支承动态特性的有效方法[4-6].

    压电主动控制技术根据气浮支承所调控的参数不同可以分为两个方面,一方面是气膜形状控制:Colombo等[7]设计了一种主动控制气膜厚度的气浮支承,试验验证了该模型有良好的抗扰动能力;Aguirre等[8-9]设计了一种主动控制气膜锥度的气浮支承,建立了多物理场有限元模型,试验证明了模型对主动控制气膜锥度气浮支承优化设计的必要性;朱定玉[10]设计了一种压电主动控制气膜锥度气浮支承,并对其动刚度增强机制进行理论和试验研究,试验表明主动控制气膜锥度气浮支承有良好的动刚度性能. 另一方面是流量控制:Park等[11-12]设计了一种主动控制节流器,通过改变小孔节流器的节流面积来提高气浮支承的动刚度;Mizμmoto等[13]提出了一种压电主动固有小孔节流器,试验表明主动固有小孔节流器能增强气浮支承的静刚度,但对气浮支承动态性能的提升程度有限. 在现有的研究中,对于压电主动控制流量方面做的研究较少.

    本文中在传统小孔节流气浮支承的基础上增加压电陶瓷促动器和柔性铰链,设计了一种基于流量控制的可变节流高度气浮支承,并通过Fluent软件仿真计算得出小孔节流器的结构参数、运动参数和气浮支承工作参数对可变节流高度气浮支承动态性能的影响规律,为主动控制气浮支承的设计提供参考.

    可变节流高度气浮支承主要由上端盖、压电陶瓷促动器、促动器接头、柔性铰链、小孔节流器和止推板组成. 可变节流高度气浮支承结构示意图如图1所示,结构参数列于表1中. 柔性铰链工作时处于振动状态,因此需要具有良好的韧性和弹性,其材料选用弹簧钢(65Mn)[14],其他零件主要承受载荷,其材料选用铝合金[15]. 小孔节流器镶嵌在柔性铰链中心,柔性铰链、压电陶瓷促动器和促动器接头之间用螺栓连接,上端盖、柔性铰链和止推板之间用螺栓连接. 可变节流高度气浮支承的工作原理是高压气体由上端盖进气孔流入,经促动器接头流入小孔节流器,通过小孔节流器的节流作用,止推板和基座之间会产生1层气膜,从而产生向上的承载力. 压电陶瓷促动器在受到正弦激励电压后推动柔性铰链和小孔节流器一起做如图2所示的幅值为A、频率为f的正弦运动. 小孔节流器的运动会引起气浮支承质量流量变化,从而影响均压腔和气膜区域的压强分布,改变气浮支承的承载力.

    图  1  可变节流高度气浮支承结构示意图
    Figure  1.  Schematic diagram of aerostatic bearing
    表  1  气浮支承各项参数
    Table  1.  Parameters of the aerostatic bearing
    ParametersSpecifications
    The outside diameter of flexure hinge, D1/mm65
    The diameter of the aerostatic bearing, D2/mm100
    The diameter of the orifice restrictor (the diameter of equalizing cavity), D3/mm2/3/4/5
    The diameter of orifice, D4/mm0.2
    The outer diameter of the annular slit, D5/mm5.2
    The thickness of flexure hinge, H1/ mm2
    The height of the orifice, H2/mm0.5
    The height of the orifice restrictor, H3/mm6
    The height of the circular slit, H4/mm3
    The throttling height (the height of equalizing cavity), ha/μm10/15/20/25/30
    The thickness of gas film, hf/μm10/15/20/25/30
    Supply pressure, Ps/MPa0.2/0.3/0.4/0.5/0.6
    Atmospheric pressure, Pa/MPa0.1
    下载: 导出CSV 
    | 显示表格
    图  2  柔性铰链运动示意图
    Figure  2.  Diagram of flexure hinge movement

    可变节流高度气浮支承工作时的气体实际流动情况是十分复杂的,因此根据经典润滑理论[16]做出了如下假设:

    (1) 润滑气体为牛顿流体;

    (2) 润滑气体是单相、连续介质;

    (3) 气浮支承内壁无热交换;

    (4) 忽略惯性力的作用;

    (5) 忽略阻尼腔质量流量的变化对气浮支承承载力的影响.

    基于以上假设,可以将复杂的N-S方程运用一维分析方法来表示,对柱坐标系下的气体运动方程进行简化得式(1~3).

    $$ \frac{{\partial p}}{{\partial r}} = \eta \frac{{{\partial ^2}{v_{\text{r}}}}}{{\partial {z^2}}} $$ (1)
    $$ \frac{{\partial p}}{{\partial \theta }} = 0 $$ (2)
    $$ \frac{{\partial p}}{{\partial z}} = 0 $$ (3)

    式中:η为空气动力黏度,vr为气体在半径方向上的速度.

    由式(1)、(2)和(3)可知压力p$ \theta $z没有关系,因此式(1)可以写为式(4).

    $$ \frac{{{\text{d}}p}}{{{\text{d}}r}} = \eta \frac{{{\partial ^2}{v_{\text{r}}}}}{{\partial {z^2}}} $$ (4)

    根据质量守恒原理:

    $$ {q_{{{\text{m}}_1}}} = {q_{{{\text{m}}_2}}} $$ (5)

    式中:$ {q_{{{\text{m}}_1}}} $为单位时间流入均压腔的质量流量,$ {q_{{{\text{m}}_2}}} $为单位时间流入气膜的质量流量.

    $$ {q_{{{\text{m}}_{\text{1}}}}} = 2{\text{π}}r\int_0^{{h_{\text{f}}} + {h_{\text{a}}} + \Delta {h_{\text{a}}}} {\rho {v_{\text{r}}}} {\text{d}}z $$ (6)
    $$ {q_{{{\text{m}}_{\text{2}}}}} = 2{\text π} r\int_0^{{h_{\text{f}}}} {\rho {v_{\text{r}}}} {\text{d}}z $$ (7)

    r方向速度表达式[17]如式(8)所示:

    $$ {v_{\text{r}}} = - \frac{1}{{2\eta }}\frac{{{\text{d}}p}}{{{\text{d}}r}}\left( {h - z} \right)z $$ (8)

    气体的状态方程:

    $$ p = \rho {\rm R}T $$ (9)

    式中:T为绝对温度,R为气体常数,ρ为空气密度.

    将式(8)带入到式(6)和(7)中,整理可得质量流量:

    $$ {q_{{{\text{m}}_{\text{1}}}}} = \frac{{{\text{π}}r\rho {{\left( {{h_{\text{f}}} + {h_{\text{a}}} + {{\Delta }}{h_{\text{a}}}} \right)}^3}}}{{6\eta }}\frac{{{\text{d}}p}}{{{\text{d}}r}} $$ (10)
    $$ {q_{{{\text{m}}_{\text{2}}}}} = \frac{{{\text{π}}r\rho {h_{\text{f}}}^3}}{{6\eta }}\frac{{{\text{d}}p}}{{{\text{d}}r}} $$ (11)

    把式(9)带入到式(10)和(11)中,整理可得:

    $$ p{\text{d}}p = \frac{{{\text{6}}\eta {\rm R}T{q_{{{\text{m}}_1}}}}}{{{\text{π}}{{\left( {{h_{\text{f}}} + {h_{\text{a}}} + \Delta {h_{\text{a}}}} \right)}^3}}}\frac{{{\text{d}}r}}{r} \quad ({R_1} \leqslant {r_1} \leqslant {R_2}) $$ (12)
    $$ p{\text{d}}p = \frac{{6\eta {\rm R}T{q_{{{\text{m}}_2}}}}}{{{\text{π}}{h_{\text{f}}}^3}}\frac{{{\text{d}}r}}{r} \quad ({R_2} \leqslant {r_2} \leqslant {R_3}) $$ (13)

    式(12)和(13)分别在对应区段上积分得:

    $$ {P_1}^2 - {P_{\text{b}}}^2 = \frac{{12\eta {\rm R}T{q_{{{\text{m}}_{\text{1}}}}}}}{{{\text{π}}{{\left( {{h_{\text{f}}} + {h_{\text{a}}} + \Delta {h_{\text{a}}}} \right)}^3}}}\ln \frac{{{r_1}}}{{{R_2}}} \quad ({R_1} \leqslant {r_1} \leqslant {R_2}) $$ (14)
    $$ {P_2}^2 - {P_{\text{a}}}^2 = \frac{{12\eta {\rm R}T{q_{{{\text{m}}_2}}}}}{{{\text{π}}{h_{\text{f}}}^3}}\ln \frac{{{r_2}}}{{{R_3}}} \quad ({R_2} \leqslant {r_2} \leqslant {R_3}) $$ (15)

    式中:$ {P_{\text{d}}} $为进气小孔出口处压强,$ {P_{\text{b}}} $为均压腔和气膜交界处压强,$ {R_1} $为小孔半径,$ {R_2} $为均压腔半径,$ {R_3} $为气浮支承半径.

    利用边界条件,当$ {r_1}{\text{=}}{R_1} $时,$ {P_1}{\text{=}}{P_{\text{d}}} $,当$ {r_2}{\text{=}}{R_2} $时,$ {P_2}{\text{=}}{P_{\text{b}}} $,可以求得均压腔区域的压力:

    $$ \begin{aligned}{P_1} = &\sqrt {\frac{{12\eta {\rm R}T{q_{{{\text{m}}_{\text{1}}}}}}}{{{\text{π}}{{\left( {{h_{\text{f}}} + {h_{\text{a}}} + \Delta {h_{\text{a}}}} \right)}^3}}}\ln \frac{{{r_1}}}{{{R_2}}} + \frac{{12\eta {\rm R}T{q_{{{\text{m}}_{\text{2}}}}}}}{{{\text{π}}{h_{\text{f}}}^3}}\ln \frac{{{R_2}}}{{{R_3}}} + {P_{\text{a}}}^2} \\ &({R_1} \leqslant {r_1} \leqslant {R_2})\end{aligned} $$ (16)

    气膜区域压力:

    $$ {P_2} = \sqrt {\frac{{12\eta {\rm R}T{q_{{{\text{m}}_2}}}}}{{{\text{π}}{h_{\text{f}}}^3}}\ln \frac{{{r_2}}}{{{R_3}}} + {P_{\text{a}}}^2} \quad ({R_2} \leqslant {r_2} \leqslant {R_3}) $$ (17)

    小孔节流器的运动方程:

    $$ \Delta {h_{\text{a}}} = A\sin 2{\text{π}}ft $$ (18)

    气浮支承的承载力等于均压腔的承载力和气膜的承载力之和减去环境压力,因此气浮支承的承载力方程如下所示:

    $$ {W_1} = 2{\text{π}}\int_{{R_1}}^{{R_3}} {Pr{\text{d}}r} - {\text{π}}{R_3}^2{P_{\text{a}}} $$ (19)
    $$ {W_2} = \int_{{R_2}}^{{R_1}} {{P_1}(A,f,r,t){\text{d}}r} + \int_{{R_3}}^{{R_2}} {{P_2}\left( {A,f,r,t} \right){\text{d}}r} - {\text π} {R_3}^2{P_{\text{a}}} $$ (20)
    $$ \Delta W = {W_2} - {W_1} $$ (21)
    $$ k = \frac{{\Delta W}}{{\Delta {h_{\text{a}}}}} $$ (22)

    式中:$ {W_1} $为气浮支承稳态承载力,$ {W_2} $为气浮支承瞬态承载力,k为气浮支承动刚度.

    由式(20)和式(22)可见,气浮支承的承载力与小孔节流器运动幅值、运动频率和小孔节流器直径有相关性,气浮支承的动刚度与小孔节流器运动频率有相关性.

    由于圆形气浮支承具有对称性,为了提升计算速度仅计算1/4气域模型. 为了保证仿真计算精度,对气浮支承气域模型进行六面体网格划分,且网格总数不少于200万. 由于节流口和压力出口部分压力梯度很大,因此对节流小孔和均压腔流域进行了网格加密处理,气膜流域压力较小则网格划分相对稀疏. 可变节流高度气浮支承CFD模型如图3所示.

    图  3  可变节流高度气浮支承CFD模型
    Figure  3.  CFD model of aerostatic bearing with variable height restrictor

    可变节流高度气浮支承气域模型可分为4个部分:小孔流域(fluid 1)、均压腔流域(fluid 2)、阻尼室(fluid 3)和气膜流域(fluid 4). 气域部分边界条件设置:小孔上表面设为压力入口(pressure-inlet),气膜外边界设为压力出口(pressure-outlet),左右侧为对称面(symmetry),均压腔上表面为动网格边界(move)和耦合面(interface 1、interface 2),其他边界均为壁面(wall). 假设气浮支承内部气体为理想气体,瞬态仿真计算运用realizable k-ε湍流模型,动网格边界运动形式采用用户自定义程序(User Defined Functions,UDF)进行定义,动网格及时更新方法采用动态铺层法,气浮支承边界条件示意图如图4所示.

    图  4  气浮支承边界条件示意图
    Figure  4.  Schematic diagram of boundary conditions of aerostatic bearing

    为了验证本文中基于realizable k-ε模型的数值仿真方法对可变节流高度气浮支承动态性能分析的适用性,运用相同气浮支承模型,将Ishibashi等[18]利用层流模型瞬态仿真计算结果和在realizable k-ε模型下瞬态仿真计算结果进行对比. 参考文献[18]中的气浮轴承结构为小孔节流无腔圆形气浮支承,其结构示意图如图5(a)所示. 主要参数包括:小孔半径r1=0.25 mm,气浮支承半径r2=5 mm,小孔高度h1=1 mm,气膜厚度h2=6 μm,供气压强Ps=0.49 MPa,出口压强Pa=0. 气膜下表面为动网格边界,动网格运动边界的运动幅值A=0.05 μm,运动频率f=125 Hz. realizable k-ε模型和层流仿真结果如图5(b)所示.

    图  5  气浮支承结构示意图和仿真结果对比图
    Figure  5.  Schematic diagram of aerostatic bearing and comparison of calculation results

    通过对比分析可知,层流模型和realizable k-ε模型的承载力仿真结果均呈正弦规律变化,且两者承载力波动量基本吻合,仅在静态承载力上存在约0.04 N的误差,证明了本文中所采用的计算模型和CFD动网格数值仿真方法在可变节流高度气浮支承动态性能分析上的可行性和有效性.

    利用Fluent软件通过上述气浮支承CFD模型和边界条件设置对可变节流高度气浮支承动态特性进行瞬态仿真,可以得到小孔节流器的结构参数、运动参数和气浮支承工作参数对可变节流高度气浮支承动态性能的影响规律.

    为了分析小孔节流器运动幅值和供气压强对气浮支承承载力的影响,取初始条件:气膜厚度hf=10 μm,运动频率f=1000 Hz,节流高度ha=10 μm,小孔节流器直径D3=2 mm,供气压强Ps=0.2/0.3/0.4/0.5/0.6 MPa,运动幅值A=5/7.5/10/12.5/15 μm,其他结构参数保持不变. 小孔节流器运动幅值和供气压强对承载力的影响曲线如图6(a~e)所示.

    图  6  运动幅值和供气压强对承载力的影响
    Figure  6.  Influence of motion amplitude and supply pressure on the load capacity

    图6(a~e)能够分析出:气浮支承承载力呈周期性规律变化,且在t=0~0.0005 s的承载力波动量均小于t=0.0005~0.001 s的承载力波动量. 当供气压强相同时,气浮支承的承载力波动量随着小孔节流器的运动幅值的增大而增大. 当运动幅值相同时,随着供气压强的增大,气浮支承的承载力波动量会明显增大.

    为了分析小孔节流器运动幅值和膜厚对气浮支承承载力的影响,取初始条件:小孔节流器初始位置ha=10 μm,运动频率f =1 000 Hz,供气压强Ps=0.6 MPa,小孔节流器直径D3=2 mm,运动幅值A=5/7.5/10/12.5/15 μm,气膜厚度hf=10/15/20/25/30 μm,其他结构参数均保持不变. 小孔节流器运动幅值和膜厚对承载力的影响曲线如图7(a~e)所示.

    图  7  运动幅值和膜厚对承载力的影响
    Figure  7.  Influence of motion amplitude and film thickness on the load capacity

    图7(a~e)能够分析出:当小孔节流器运动幅值一定时,气浮支承的承载力波动量受气膜厚度的影响较大,并且随着气膜厚度的减小,气浮支承的承载力波动量会明显增大. 当气膜厚度一定时,气浮支承承载力的波动量随着运动幅值的增加而增大. 当膜厚hf=10 μm、t=0.00075 s时,由于运动幅值A=15 μm,此时均压腔高度减小为5 μm,气浮支承质量流量迅速减小,承载力也随之迅速减小,因此图7(d)和图7(e)中会出现承载力变化曲线相交的现象.

    为了分析小孔节流器运动幅值和节流高度对气浮支承承载力的影响,取初始条件:气膜厚度hf=10 μm,运动频率f=1 000 Hz,供气压强Ps=0.6 MPa,小孔节流器外径D3=2 mm,运动幅值A=5/7.5/10/12.5/15 μm,节流高度ha=10/15/20/25/30 μm,其他结构参数保持不变. 小孔节流器运动幅值和节流高度对气浮支承承载力的影响曲线如图8(a~e)所示.

    图  8  运动幅值和节流高度对承载力的影响
    Figure  8.  Influence of motion amplitude and throttling height on the load capacity

    图8(a~e)能够分析出:当小孔节流器的节流高度不变时,气浮支承承载力的波动量随运动幅值的增加而增加. 当小孔节流器的运动幅值不变时,节流器的节流高度由10 μm增至30 μm,气浮支承承载力的初始位置会由326 N增至340 N,而气浮支承的承载力波动量随着节流高度的增大而减小.

    为探究小孔节流器直径和运动频率对气浮支承承载力的影响,取初始条件:节流高度ha=10 μm,气膜厚度hf=10 μm,运动幅值A=10 μm,供气压强Ps=0.6 MPa,小孔节流器直径D3=2/3/4/5 mm,运动频率f=100/1000/5 000/10000 Hz,其他结构参数均保持不变. 小孔节流器直径和运动频率对气浮支承承载力的影响曲线如图9(a~d)所示.

    图  9  小孔节流器的直径和运动频率对承载力的影响
    Figure  9.  The influence of the diameter and movement frequency of the restrictor on the load capacity

    图9(a~d)能够分析出:当运动频率不变时,小孔节流器的直径由2 mm增大至5 mm,气浮支承质量流量随之增大,气浮支承承载力初始位置由297 N增大至315 N. 当小孔节流器直径D3=2 mm时,随着运动频率的增加,气浮支承的承载力波动量增幅几乎为0. 当小孔节流器直径增加至D3=5 mm时,气浮支承的承载力波动量随着运动频率的增加而明显增加,且最大波动量达到190.9 N.

    为了探究小孔节流器直径和运动频率对气浮支承动刚度的影响,取初始条件:节流高度ha=10 μm,气膜厚度hf=10 μm,运动幅值A=10 μm,入口压力Ps=0.6 MPa,小孔节流器直径D3=2/3/4/5 mm,运动频率f为100/500/1000/5000/10000 Hz,其他结构参数保持不变. 小孔节流器的直径和运动频率对气浮支承动刚度的影响曲线如图10所示.

    图  10  小孔节流器的直径和运动频率对动刚度的影响
    Figure  10.  The influence of the diameter and movement frequency of the restrictor on the dynamic stiffness

    分析图10结果可得出:当小孔节流器运动频率f为100~1000 Hz时,增加小孔节流器直径对气浮支承的动刚度几乎无影响;但当小孔节流器运动频率f为1000~10000 Hz时,增加小孔节流器直径会使气浮支承的动刚度得到明显提升.

    a. 对于可变节流高度气浮支承,可以通过调节节流高度来改变气浮支承的承载力.

    b. 当可变节流高度气浮支承的其他参数一定时,增加小孔节流器的运动幅值会使气浮支承的承载力波动量明显增大;但当气浮支承供气压强减小时,小孔节流器的运动幅值对气浮支承承载力的影响随之减弱.

    c. 当可变节流高度气浮支承的其他参数一定时,增加小孔节流器的运动幅值会使气浮支承的承载力波动量明显增大;但当气膜厚度逐渐增加时,小孔节流器的运动幅值对气浮支承的承载力影响随之减弱.

    d. 当可变节流高度气浮支承的其他参数一定时,增加小孔节流器的运动幅值会使气浮支承的承载力波动量明显增大;但当节流高度增加时,小孔节流器的运动幅值对气浮支承的承载力影响随之减弱.

    e. 当气浮支承小孔节流器直径较小时,随着小孔节流器运动频率的增加,气浮支承的承载力波动量和动刚度的增幅不明显;但当气浮支承小孔节流器直径增大时,气浮支承的承载力波动量和动刚度会随着小孔节流器的运动频率的增加而明显提升.

  • 图  1   柔性箔柱面气膜密封示意图

    Figure  1.   Schematic diagram of compliant foil gas seal

    图  2   柔性箔片气膜密封压力分布

    Figure  2.   The pressure distribution of compliant foil gas seal

    图  3   声发射工作原理

    Figure  3.   The operational principles of acoustic emission detection

    图  4   轴套的表面粗糙度纹理图

    Figure  4.   The surface topography with different roughness

    图  5   高超气膜密封试验台的AE监测系统

    Figure  5.   The system of acoustic emission detection in gas seal test rig

    图  6   不同表面状态下的AE信号特征

    Figure  6.   AE signal characteristics with different roughness

    图  7   不同压差下的AE信号特征(Ra 0.2)

    Figure  7.   AE signal characteristics under the variation of differential pressure (Ra 0.2)

    图  8   不同压差下的AE信号特征(Ra 0.4)

    Figure  8.   AE signal characteristics under the variation of differential pressure (Ra 0.4)

    图  9   不同压差下的AE信号特征(Ra 0.8)

    Figure  9.   AE signal characteristics under the variation of differential pressure (Ra 0.8)

    图  10   不同压差变化下的AE信号特征(Ra 1.6)

    Figure  10.   AE signal characteristics under the variation of differential pressure (Ra 1.6)

    图  11   Ra 0.2的样品在不同转速下的AE信号特征

    Figure  11.   AE signal characteristics with different speed of Ra 0.2

    图  12   气膜膜厚30 μm下的AE信号特征

    Figure  12.   AE signal characteristics detection with gas film thickness of 30 μm

    表  1   气膜密封-转子高速试验台运行参数

    Table  1   Operation parameters of high speed gas seal-rotor test rig

    Operation parameters Specifications
    Boundary speed 6 000~18 000 r/min
    Inlet pressure 100~300 kPa
    Outlet pressure 100 kPa
    Eccentricity ratio 0.5~0.7
    下载: 导出CSV

    表  2   气膜密封不同表面状态对应的AE信号特征

    Table  2   The AE signal characteristics with different surface roughness

    Average surface roughness/μm Center frequency distribution/kHz Highest center frequency distribution/kHz
    0.2 125、240、375 240、375
    0.4 125、200、275 200、275
    0.8 125、240、275 125、240
    1.6 125、190、240、275 125
    下载: 导出CSV

    表  3   气膜密封不同压差下对应的AE信号特征

    Table  3   The AE signal characteristics of different surface roughness

    Average surface roughness/μm Center frequency distribution/kHz Highest center frequency distribution/kHz
    0.2 125、240、375 240、375
    0.4 125、200、275 200、275
    0.8 125、240、275 125、240
    1.6 125、190、240、275、etc 125、190
    下载: 导出CSV

    表  4   气膜膜厚约为30 μm时不同表面状态下AE信号特征

    Table  4   The AE signal characteristics of different surface roughness with 30 μm

    Average surface roughness/μm Center frequency distribution/kHz Highest center frequency distribution/kHz
    0.2 125, 240, 275 240, 275
    0.4 125, 275 125, 275
    0.8 125, 240, 275 125, 240
    1.6 125, 240, 275, etc 125, 240
    下载: 导出CSV
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  • 期刊类型引用(2)

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  • 收稿日期:  2023-05-20
  • 修回日期:  2023-10-24
  • 录用日期:  2023-10-25
  • 网络出版日期:  2023-11-05
  • 发布日期:  2023-11-27
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