IN-202541026959-A - IMPROVEMENT IN THE SEALING CHARACTERISTICS OF THE LABYRINTH PISTON BY THE ADDITION OF CAVITY PATTERN

Abstract

In chemical industries, contact oil seals that block gas leakage are unsuitable for reciprocating compressors because the moving parts can damage these seals due to friction, and the resulting heat from friction heightens the risk of fire hazards. Consequently, employing non-contact sealing is a viable option that optimizes flow resistance for a given pressure difference and decreases the leakage flow rate. The labyrinth configuration is the most favored non-contact sealing component because of its straightforward design and ease of manufacturing. The labyrinth piston compressor's efficiency can be enhanced by minimizing the leakage flow rate. A straight- through labyrinth configuration is a frequently utilized non-contact sealing system for high-pressure liquids. It operates by dissipating the energy of the moving fluid through interactions of turbulent viscosity, accomplished using a sequence of teeth and cavities. In the present invention, the sealing characteristics of the labyrinth piston seal are further improved-by providing a cavity pattern in the-first groove with an angular-spacing of 45?. The piston models with plain surface and cavity patterns in the labyrinth surface are created using the additive manufacturing technique, with Poly lactic Acid (PLA) as the raw material It is identified that the labyrinth piston with a cavity pattern has good sealing characteristics, which could overcome the drawbacks of traditional piston seals.

Inventors

• B VIJAYARAGAVAN
• S P ASOK

Dates

Publication Date

20250404

Application Date

20250324

Priority Date

20250324

Claims (3)

1. We claim, the cavity introduced in the first groove of the labyrinth piston improves itssealing characteristics.
2. 2. We claim, the labyrinth piston with cavity profile fabricated using PETG material canwithstand a maximum pressure of 8 bar.
3. 3. We claim, the present invention reduces leakage by creating a new flow through thecavity profile, which opposes the leakage flow through the annular space between thecylinder casing and the labyrinth piston.

Description

Complete SpecificationField oflnventionHigh-pressure gases are produced in reciprocating compressors, in which the piston isprovided with a contact seal to prevent gas leakage into-the crank region. As reciprocatingpiston compressors in chemical industries deal with flammable gases, ignition is possible dueto the friction heat developed in the contact seal. When the traditional piston with oil rings isreplaced with a labyrinth piston in a reciprocating piston compressor, heat generated by thefriction inside the cy Iinder piston assembly is avoided.A straight-through labyrinth arrangement is a commonly used non-contacting sealingmechanism for high-pressure fluids. It works by dissipating the energy of the flowing fluidthrough turbulent viscosity interaction; which-is achieved with a series of teeth and cavities.The geometric parameters of straight-through labyrinth seals directly impact their ability tocontrol leakage. Research is ongoing to improve the performance of these seals by modifyingtheir geometric parameters.In the present invention, the sealing characteristics of the labyrinth piston seal arefurther improved by providing a cavity pattern in the first groove with an angular spacing of45°. The piston models with plain surface and cavity patterns in the labyrinth surface arecreated using the additive manufacturing technique, with Polylactic Acid (PLA) as the rawmaterial. It is identified that the labyrinth piston with a cavity pattern has good sealingcharacteristics, which could overcome the drawbacks of traditional piston seals.Background of inventionThe efficiency of the labyrinth piston compressor can be increased by decreasing theleakage flow rate. The contact oil seals that prevent gas leakage cannot be used in reciprocatingcompressors in chemical industries as the moving parts will cause damage to the contact sealsthrough friction and the frictional heat increases the risk of fire accidents. Therefore, noncontactsealing is a possible solution that improves the flow resistance for a specified pressuredifference and reduces the leakage flow rate. Labyrinth configuration is the most preferred noncontactsealing component due to its simplicity in design and manufacture. The labyrinth sealconfiguration is further classified into three categories- straight, stepped, and staggered. Thestraight-through labyrinth configuration is most frequently used in labyrinth pistoncompressors. When the gas flows through the annular clearance region above the tooth, thehigh-pressure head of the fluid to be restricted is converted to kinetic energy in the flow, andthe fluid comes out as a jet from the clearance. Only a portion of the jet enters the subsequentclearance, while the remaining part is dissipated by vortex generation in the cavities. As thefluid jet passes the teeth one by one, the jet's kinetic energy is dissipated continuously, resultingin reduced leakage.The leakage control characteristics of the straight-through labyrinth configuration areimproved by modil)'ing the geometric parameters. Numerical analysis is used in the initialresearch stage to improve the sealing, which is to be validated by experiment testing. The test-::1' rig consists of a labyrinth piston seal enclosed inside the cylinder casing and a closing lid with provisions for pressure measurement and air inlet/outlet. The annular region between thelabyrinth piston and the outer cylinder casing forms the seal path to be investigated for bette> leakage control. Conventional manufacturing methods like facing, drilling, and grooving are suitable for fabricating primary labyrinth flow paths with perfect rectangular cavities. It is time-consuming and expensive to fabricate complex labyrinth shapes using conventional methods.Additive manufacturing is the computer-controlled creation of three-dimensional solidsby depositing the materials, usually in layers. Additive manufacturing, also called 30 printing,supports the fabrication of complex labyrinth shapes at reduced time and cost. PolyethyleneTerephthalate Glycol (PETG) is the material chosen for fabrication using the Fused DepositionModelling technique by maintaining the bed temperature at 80°C and the extruder temperaturebetween 220°C and 260°C. Before the labyrinth piston component was fabricated with PETG,the material's ability to withstand the force of the striking air up to a maximum pressure of 8bar was tested in the ANSYS software. The maximum deformation of 3.9xt0·7m is observedfor a maximum pressure of 8 bar, thus making the piston model using PETG suitable fo>carrying out leakage analysis. The dimension of the model taken for numerical analysis isexactly same as the model used for experimental testing.Brief description of drawingsFig. I is the 30 model of the plain pistonFig. 2 is the 30 model of the labyrinth piston with cavity patternFig. 3 is the cross-sectional view of the labyrinth piston leakage test assemblyFig. 4 is the labyrinth piston with cavity pattern fabricated by additive