螺旋槽干气密封高压端面变形机理的理论与实验研究

发布时间：2018-01-18 08:38

本文关键词：螺旋槽干气密封高压端面变形机理的理论与实验研究　出处：《浙江工业大学》2014年博士论文　论文类型：学位论文

【摘要】：随着流体机械向高速、高压等工况的发展,密封环端面高压机械变形导致的磨损失效问题日益突出。论文对高压工况下干气密封的气膜特性、端面变形机理和变化规律开展了理论与实验研究,主要工作包括：首先,在对气膜实际特性影响分析中,基于气体润滑理论,综合考虑密封气膜的热力学特性和表面微尺度效应,建立了高压气膜润滑密封特性分析模型,揭示了高压工况下热粘效应、表面粗糙度效应、界面滑移效应对密封端面气膜压力分布及密封性能的影响规律。研究发现,高压实际热力过程与等温过程相近；热粘效应能提高密封承载力,并对密封性能影响起主导作用；表面粗糙度有利于提高密封动压效应及稳定性,降低泄漏量；滑移流效应使泄漏率增大。接着,分别基于圆环理论和弹性力学基本理论,建立扭转变形无量纲计算模型和流固耦合计算模型,提出端面膜压引起端面扭转变形的计算方法,结果表明：膜压变形可提高密封稳定性和动压效应,但泄漏率增大；当po≥3MPa时,开启力受其影响较小,而泄漏率和稳定性影响相对较大；当h0≥3μm时,膜压变形的影响可忽略不计。本文操作条件下螺旋槽端面几何参数优选值为槽数Ng=12,槽深比H2=3,螺旋角α15°,槽坝比ψ=0.7,槽台宽比e=1.0。扭转变形使端面沿泄漏方向形成发散间隙,复杂截面密封环上台阶的长或宽小于3mm时,可直接忽略台阶影响。扭转角随台阶半径比和长度比以及O形圈位置的长度比的增大而增大,随台阶宽度比、内径的增大而减少,其中台阶宽度比的影响最为显著；相比密封结构,O形圈位置影响较小。综合变形使端面形成发散间隙,其中以扭转变形的影响为主,结构因素在高压干气密封设计中占主导地位。综合变形使开启力降低,泄漏率增大；高压条件下,转速对密封膜压、膜厚和变形的影响不大。单位面积所受承载力大的静环(结构b)端面变形和膜厚大于承载力小(结构a)的环,结构a的开启力大于结构b,结构a的泄漏量小于结构b。当0型圈的位置远离密封端面(a处)时,端面变形影响较大,密封端面开启较为困难,泄漏量大；当O型圈的位置接近密封端面(1)处)时,端面变形影响较小,开启相对容易,泄漏量小,但影响不如结构尺寸的影响显著。最后,通过搭建高压干气密封实验台,测试膜厚、泄漏率、端面磨损等数据,研究了高压干气密封端面的变形机理。实验表明：实测泄漏率及膜厚与理论计算值趋势一致,数值结果基本吻合。5MPa压力下各结构因素的膜厚在4.0μm至6.1μm之间,此时密封具有良好的静压开启性能。结构因素对密封开启性能影响较大,结构尺寸对变形和密封性能的影响大于密封圈位置的影响,运行后的密封端面外径处出现磨损,沿径向的磨损长度、磨损量、粗糙度及泄漏率的分布或变化规律与理论计算结果一致,验证了高压干气密封变形和磨损之间的关系和上述分析计算模型的合理性。论文的研究成果系统地完善了干气密封高压变形的理论,可为高压干气密封端面抗变形设计及其工程应用提供理论依据。
[Abstract]:With the high-speed development of fluid machinery, high pressure conditions, high pressure mechanical deformation of seal rings wear caused problems have become increasingly prominent. The characteristic of gas film under high pressure dry gas seal, deformation mechanism and variation law carried out theoretical and experimental research, the main work includes:
First of all, in the analysis of the actual effect on properties of the film, based on gas lubrication theory, considering the thermodynamic properties and the surface of the gas film seal effect of micro scale, a high pressure gas film lubrication analysis model of sealing characteristics, reveals the thermal viscosity effect under high pressure, the effect of surface roughness, interface slip effect on the influence of gas seal film face pressure distribution and sealing performance. The study found that the high pressure thermal process and isothermal process similar; thermo viscosity effect can improve the sealing capacity, and the leading role of the sealing performance effect; surface roughness can improve the sealing effect of dynamic pressure and stability, reducing leakage; slip flow effects of the leakage rate increased.
Then, based on the theory of ring and the basic theory of elasticity, the torsional deformation dimensionless calculation model and fluid solid coupling calculation model are established, and the calculation method of torsional deformation caused by end face pressure is put forward.
The membrane deformation can improve the sealing stability and dynamic pressure effect, but the leakage rate increases; when the Po is greater than or equal to 3MPa, the opening force is less affected, while the effect of leakage rate and stability is relatively large; when H0 is larger than 3 m, the effect of membrane deformation can be ignored. The preferred geometric parameters of spiral groove face the operation under the condition of Ng=12 value for the slot number, groove depth ratio H2=3, spiral angle of 15 degrees, slot dam than w =0.7, groove width ratio e=1.0.
The torsional deformation of surface forming along the direction of leakage clearance divergence, complex cross section sealing ring on the steps of the length or width is less than 3mm, can be directly affected. Ignore the torsion angle with the step step radius ratio and length ratio and O ring position length ratio increases with step width ratio, reduced diameter increases the effect of the step width than the most significant; compared with the O shaped sealing structure, smaller ring position.
Comprehensive deformation makes the surface forming divergent gap, the torsional deformation effects, structural factors in high pressure dry gas seal design is dominant. Comprehensive deformation makes the opening force is reduced, the leakage rate increased; under the condition of high pressure, speed of sealing film pressure, film thickness and deformation has little effect. The static unit area the bearing ring (structure b) face deformation and film thickness is greater than the carrying capacity of small (structure a) ring structure a opening force structure is greater than B, the structure of a leakage is less than B. when the structure type 0 circle position away from the sealing surface (a), large end effect, seal face opening is difficult, the large amount of leakage; when the O ring is located close to the seal (1) at the time), effect of end face deformation is small, relatively easy to open, a small amount of leakage, but the influence as structure size significantly.
Finally, through the dry gas seal experimental platform to build test pressure, film thickness, leakage rate, surface wear and other data, the deformation mechanism of high pressure dry gas seal. The experimental results show that the measured leakage rate and film thickness are consistent with theoretical calculation, numerical results coincide each factor structure of.5MPa under pressure in the film thickness between 4 m to 6.1 m, the seal has good static performance. Open structure factors on seal opening performance influence, effects of structure size on the sealing performance of the sealing ring is greater than the effect of deformation and the position of the seal at the outer radius of the end after running wear, wear along the length of the radial wear quantity calculation roughness and leakage rate distribution or variation is consistent with the theoretical result, verified the high pressure dry gas seal deformation and the relationship between the wear and the analysis on the rationality of the model.
The research results of the paper improve the theory of high pressure deformation of dry gas seal, and provide theoretical basis for the design and engineering application of high pressure dry gas seal face.

【学位授予单位】：浙江工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH136

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