Testing System And Parameters Determination Of Performance On Spiral Groove Dry Gas Seals

Spiral groove dry gas seal is widely used in petrochemical industry. The stability andreliability of its operation are key to petrochemical enterprise security. The dynamiccharacteristic parameters have been the hot spot of domestic and foreign research, and also thedifficulty of research. In view of the above situation, this article focuses on parameters thatinfluence spiral groove dry gas seal face, including seal face performance parameters (gasfilm pressure, friction torque and face temperature, speed, leakage, friction powerconsumption) and seal face stability parameters (gas film thickness and vibrationdisplacement of dynamic and static ring). Because the research of vibration is very few bothat home and abroad, and only stay in theory, so this article focuses on the vibration of thesealing ring system test, and introduces the test method and data processing. Based onLabview, the test system software development platform, spiral groove dry gas seal facetest-bed is established, Through selecting and installing specific sensors, conditioner, thedata acquisition card and other corresponding hardware equipments, and taking particular testmethod and necessary anti-interference measures, the performance parameters and stabilityparameters of spiral groove dry gas seal face are being debugged, checked, demarcated andmeasured. Based on post-processing procedure of Labview software, the test data is processed;the test value and the theoretical value are compared and analyzed. The factors of influencingthe end flow field parameters, the influence of running condition to seal parameters and themethod of improving sealing performance are researched. This paper mainly researches thefollowing contents:In this paper flow field parameters are calculated and simulated by using FLUENTsoftware. To measure the impact factors of trepanning in static ring face to gas film pressureof flow field by installing sensor, the three-dimensional spiral groove model of dry gas seal isbuilt by the solidworks software in this paper. The model also includes opening andnon-opening hole in static ring face corresponding slot root in the moving ring groove. In thespecific conditions, two different flowing states of three-dimensional microscale gas flow aresimulated in internal spiral groove dry gas seal by the Fluent software. The leakage of thistwo models is gained, and the theoretical value is very close to the experimental value, whichindicates that the analysis of micro-dimension spiral groove flow field can be simulated byFLUENT software, and thus the pressure of different models are accurate. The impact factorsof trepanning sensor to seal face can be calculated, which has practical value in determining the pressure or revising the monitoring data and also in seeking the real data in laterexperiments.The stability of the end face, namely gas film stiffness, is calculated. Three-dimensionalmodels of spiral groove dry gas seal with five different gas film thicknesses are built bySolidworks software. In specific conditions, the five kinds of models are numericallycalculated by FLUENT software and the pressure distribution and gas film thrust are obtained.The polynomial of opening force and film thickness are obtained by the least squares method.Polynomials of gas film stiffness and gas film thickness are obtained through derivation offilm thickness. The results show that the gas film stiffness decreases with the increase of thefilm thickness, and gas film stiffness curve tends to be stable with the increase of gas filmthickness. In order to stabilize the dry gas seal system, the generation of gas film with enoughstiffness is necessary.Three-dimensional micro-scale model of flow field of spiral groove dry gas seal end faceis built, which is used to research end performance parameters. The model with various gasfilm thickness is numerically calculated in the form of laminar flow by Fluent software.According to the calculated dynamic pressure effect and radial flow rate of gas film flow field,it is accomplished to determine gas film thickness that makes the end face generate gas filmthrust and leakage and achieve the most optimal at the same time. It is obtained that differentmedia pressure and rotational speed take effect on power consumption and leakage of endface in the determining condition of the gas film thickness. Results show that the overalleffect is the most optimal within the film thickness of3-5μm. Leakage and powerconsumption increase with the increase of rotational speed when gas film thickness andpressure are determined, and their relationships are linear. Leakage and power consumptionincrease with the increase of pressure when gas film thickness and rotational speed aredetermined, and their relationships are linear as well.Because the clearance between dynamic and static ring for dry gas seal is only3-5μm, sothe analysis of its seal system axial vibration stability is particularly important. Adopting thehigh precision improved eddy current miniature sensors and Labview software, and a series ofanti-disturbance measures, the axial vibration of dry gas seal gas film sealing ring system isbeing measured, and the axial vibration displacement of gas film and dynamic and static ringand the time domain waveform are also measured. Through changing pressure and speed,three of the vibration displacement are measured, the influence of the pressure and speed tovibration displacement is researched, and the spectrum analysis of the measured time domainwaveform is finished. Experimental study indicates that, the dynamic and static ring and gasfilm vibration displacement all decrease with the rise of the speed and the medium pressure and the increase of gas film thickness, which coincides with that the dynamic pressure effectincreases with the increase of speed and air pressure. The three vibration frequency areindustrial frequency, and belong to the same frequency vibration. The axial vibrationamplitude of dynamic and static ring corresponding place is approximately same, and thecharacteristic that static ring follows dynamic ring is good. So, the plane degree and installedvertical degree of dynamic ring end face should be guaranteed in order to reduce vibrationdisplacement of static ring.