The effects of clearance sizes on labyrinth brush seal leakage. The land ring forms a clearance with the knifeedges effecting the seal. Labyrinth seal leakage analysis a thesis by orcun inam. As shown in figure 1, the labyrinth seal is made up of a number of evenly spaced thin strips, sometimes called teeth or fins. Ornltm6373, a fluid mechanics model to estimate the. In 2011, with a non rotating shaft, seal flow rate measurements with increasing inlet air temperatures to 300c show the halotm seal leaks 50% or less than the labyrinth seal.
For labyrinth seals on a rotating shaft, a very small clearance must exist between the tips of the labyrinth threads and the running surface. Effects of clearance sizes on the pressure and leakage characteristics in a shaft labyrinth brush seal were numerically. Tc ratio ofseal tooth tip to clearance tipcr tip labyrinth seal tooth tip m. In many designs, the primary sealing lip is held in position by a garter spring. A rather unexpected finding is that a dramatic increase of swirl velocity occurs near the discharge of smallclearance annular seals, which does not arise in corresponding labyrinth seals. There is a rotating mechanical shaft seal mech seal located in the head. This is the primary type of seal described in the skf seal handbook. Discharge coefficient is also found to be a strong function of tooth clearance, pitch, reynolds number and shaft speed.
Wyssmann sulzerescher wyss ltd zurich, switzerland the prediction of rotordynamic coefficients for gas seals is achieved with the aid of a twovolume bulk flow model based on turbulent rotationally symmetric 3d flow calculations including swirl. Labyrinth seals often use a series of noncontact metal rings or other. The difference in how competing seals perform is in. Steam conduits are provided in the turbine casing communicating with the annular space between the individual packing rings and the grooves in. Disadvantages leakage depends on clearance inevitable wear enlarges clearances and worsens leakage. Performance evaluation of trapezoidal teeth labyrinth seal. Furthermore, adequate clearance should be maintained between reinforcing steel and the waterstop.
On the other hand, synchronous vibration increased in amplitude, presumably due to a large. Results are compared to a data for teethonrotor labyrinth seals with smooth. The teeth of the labyrinth seal may be on the rotating shaft teeth on rotor tor or on the stator tos, or both, in an interlocking configuration. Isotech of illinois inc, usa a labyrinth seal that is designed to allow for radial, axial and angular misalignment of the shaft is described. Base seal externally placed, labyrinth, and split waterstops comprise a special class of pvc waterstops and require. Mounting instructions for labyrinth seals gmn bearing usa. They operate on the principle of positive clearance and do not rub on shafts or housing. Cavity pressures, velocity and leakage computation in. Cavity pressures, velocity and leakage computation in straight through or stepped labyrinth seals. This can be accomplished either by reducing the clearance size, the development of a new geometrical seal configuration and the use of blowing through the seal gland. In jet engines they rotor fluid interactions in stepped labyrinth seal. Results from the model are in reasonable agreement with the limited data available. The gmn noncontact seal has become famous for its compact design. Bearings which call for a high oil throughput are provided with seals with two labyrinth systems type 20.
The experimental results prove that the effects of the circumferential turbulence make. Labyrinth seal design optimization based on quadratic. The mass leak rate is shown to be proportional to the seal clearance and pressure drop in the following functional dependency. They operate on the principle of positive clearance and. The steel inner ring is first surrounded with molded aluminum. Labyrinth seals and clearance seals selection guide. Clearance effects on corresponding annular and labyrinth. Labyrinth seals that do not contact the shaft depend on a tortuous interface, fluid surface tension, and a pumplike design to prevent leakage. The radial deformation which decreases the clearance between the rotating and stationary parts of sealing surface is an indication that centrifugal. Then, the labyrinth seal was replaced with a highly stable seal not specified equipped with inlet preswirl brake. Annular seals are found to leak approximately twenty percent more than corresponding labyrinths over the entire range of realistic clearance.
Wide range of pressures, temperatures, and shaft speeds inexpensive. Air compressors generally will always use a labyrinth seal. Numerical simulation of leakage rates of labyrinth seal. These types of systems provide better particle exclusion and less lubricant leakage than standard lip seals. In this paper, the gambit of 3d model was adopted to divide the labyrinth gap in an unstructured approach. The results were compared with the simulation data of the 2d model. Performance evaluation of trapezoidal teeth labyrinth seal authors. Labyrinth seals, formerly named leidenfrost seals or mini mace, have a very specific manufacturing process that guarantees the identity of the inner and outer ring profiles to ensure they remain inseparable here are the steps taken to produce a labyrinth seal. Having the edge with john crane labyrinth seal solutions seal solutions can make a big difference in the way your rotating equipment performs. Find labyrinth seals and clearance seals on globalspec by specifications. Timken industrial seal technical manual high performance seals large bore assembled seals bearing isolators.
An adjustable labyrinth seal for a steam turbine wherein the packing rings may be displaced from a larger diameter position, affording a relatively larger shaft clearance, to a smaller diameter position, affording a relatively smaller shaft clearance. The end seal of the sleeve bearing serves to retain 90% of the oil vapor splashing oil in the chamber. Generally, springloaded lips are for retaining oil and nonspringloaded are used for low speed grease retention or excluding contaminants. Our business is servicing our customers needs for the repair and manufacture of labyrinth seals and bearings for turbomachinery, either in. The leakage through the seal is directly related to the labyrinth profile and also the clearance between the rotor and. Labyrinth seal article about labyrinth seal by the free. The remaining 5 0% is retained by the labyrinth seals. The present paper investigates the effects of the trapezoidal teeth labyrinth seal on the leakage amount in gas turbines. The labyrinth seal is made up of two separate metal ring components, inner and outer, that have interconnecting grooves that form a labyrinth gap. Please see the comparison with standard contact seals in the table below. Optimization of labyrinth seal for screw compressor. The diametral clearance between each of the seal teeth and the rotating shaft is equivalent to a series of orifices. Comparative analysis of the influence of labyrinth seal configuration.
The measurement and prediction of rotordynamic forces. Simulation was carried out on one of the important factors which affect the labyrinth seal performancethe seal clearance. Radial clearance labyrinth seal figures 1 and 2 show two arrangements of labyrinth seals in which the close running clearance is in a radial direction. Ep0276839b1 ep88101192a ep88101192a ep0276839b1 ep 0276839 b1 ep0276839 b1 ep 0276839b1 ep 88101192 a ep88101192 a ep 88101192a ep 88101192 a ep88101192 a ep 88101192a ep 0276839 b1 ep0276839 b1 ep 0276839b1 authority ep european patent office prior art keywords seal seal holder housing holder axial length prior art date 19870128 legal status the legal status is an.
Pdf turbomachinery sealing is a challenging problem due to the varying clearances caused by thermal transients, vibrations, bearing liftoff. Oil groove clearance reference up to 50 y y y y y 0. Us5002288a positive variable clearance labyrinth seal. A theoretical model for the design of a labyrinth seal gland. This study analyzed the influence of configuration and clearance on the leakage behavior of labyrinth seals. Labyrinth seals and clearance seals are minimumleakage seals that protect machine elements from contamination through a noncontact method. Pdf mechanical growth of labyrinth seal researchgate. Clearance between the shaft and labyrinth is critical. A ring shaped member in a labyrinth seal, which is either a straightwalled cylinder or a cylinder with axial steps.
The radial deformation which decreases the clearance between the rotating and stationary. The seal operates at nominal supply and discharge pressures. The diameter which corresponds to the largestdiameter landstep surface in a stepped labyrinth seal. Pdf progressive clearance labyrinth seal for turbomachinery. The axial clearance as shown in the table of dimensions means the total axial movement of both rings from one end position to the other. The effects of the main labyrinth seal parameters, such as tooth angle, sealing clearance, and cavity depth, were compared using fluent software and iterative.
The basic concept of labyrinth seals is to reduce contaminant ingression not only by restricting the clearance through which particles enter but also by creating areas of turbulent flow to exclude contaminants. A seal is a component used in a turbomachine to reduce internal leakage of the working fluid and to increase the machines efficiency. Many investigators tackled the leakage problem through labyrinth seals for turbomachinery. Well fluid moving into the pump intake will be on the top of this shaft seal.
Other system factors that affect seal leakage rates, besides condition of the seal parts, include pump operation at offdesign conditions, pipe strain, bearing problems, fitting leaks at the seal gland often mistaken as seal leakage, impeller or sleeve gasket damage, etc. The head of the seal will be bolted to the bottom of the pump intake. Typical clearance should be twice the maximum aggregate size of the concrete mix design. Labyrinth seals and clearance seals specifications. Pdf optimization of labyrinth seal for screw compressor. The diameter which corresponds to the larger of the two knifeedge diameter in a staggered labyrinth seal. The labyrinth is a straight through design and a defined clearance on the shaft. Straight through triangular labyrinth seals are one of the most commonly used types of noncontacting annular seals. The toothed labyrinth, interrupted by a vacuum break figure 7, is the most effective. Shorter deliveries are therefore possible in view of the simpler stocks 2.