Berührungsfreies Wellendichtungen für Anwendungen im Allgemeinen Maschinen- und Fahrzeugbau

FKM 2001
Booklet No. 257
Project No. 227

Abstract:

The aim of the work was to investigate the functionality of non-contact shaft seals (BFWD) under the special operating conditions in units of general mechanical engineering. The focus was on verifying the design guidelines known for low-viscosity fluids for higher-viscosity fluids. For this purpose, individual functional elements of BFWD were methodically and experimentally investigated. In order to carry out the work in a practice-oriented manner, an industry survey was carried out in advance to determine the boundary conditions for the tests. An FVA reference oil with viscosity class ISO VG 320 was selected as the test oil. The tests on individual functional elements with viscous oils proved a similar functional behavior as with the sealing of water-thin liquids. However, due to the up to 500 times higher viscosity, a flow rate up to 100 times lower could be determined for the same geometric dimensions. Comparative calculations showed that with the corresponding quantities of liquid to be processed in the sealing system, the gap heights when sealing such viscous fluids can be four to five times higher than when sealing low-viscosity liquids. A favorably designed inlet area reduces the penetrating liquid flow by up to 95% compared to an unfavorably designed one. To achieve this, the radial inlet gap must be covered and a stationary catch channel installed. The design guidelines for interception chambers known for low-viscosity liquids also apply to the sealing of viscous oils. In order to take into account the poorer flow behavior, the volume of the interception chamber must be larger. If the transition from the interception chamber to the return flow is funnel-shaped, higher viscosity liquids also exhibit more favorable flow characteristics. The drainage channels should be as large as possible. In order to record the operational influences on BFWD, the flow rate with oil injection lubrication was determined for six common bearing types. Depending on the bearing type and arrangement, the flow rate is between 5 and 95% of the injection flow. The results were used, among other things, to verify the seal loading in laboratory operation. With the help of finite element analysis (FEA) and experimental investigations, it was proven that non-contacting shaft sealing systems can actively convey air and thus also oil vapor or oil mist. As a remedy, a sealing system optimized for air flow was developed. The FEA used for the first time for this purpose has proven to be a useful tool in the design of non-contact sealing systems. Alternatively, the possibility of integrating oil-separating filter elements into BFWD was considered. The axial shaft displacements caused by thermal expansion, manufacturing tolerances and bearing clearance result in an increased penetration current in BFWDs. Using a displacement device, these increased penetration currents could be quantitatively determined in the test. To simplify installation of the complex non-contact sealing system, design variants were developed that can be used in practice as axially pluggable systems. The aim of the project was achieved. Scope of report:
90 p., 69 ill., 6 tab., 48 lit. Start of work:
01.01.1998 End of work:
31.10.2000 Funding body:
BMWi IAIF-No. 11341 Research center:
Institute for Machine Elements at the University of Stuttgart Commissioning director:
Prof. Dr.-lng. B. Bertsche Project management:
Privatdozent Dr.-lng. habil. W. Haas Editor and author:
Dipl.-lng. B. Stiegler Chairman of the working group:
Dr.-lng. D. Frey, Zahnradfabrik Friedrichshafen Chairman of the advisory board:
Mr. Rabe, Sachsenring AG, Zwickau