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To date, many experiments have been performed to study how the internal geometrical shapes of the annular liquid seal can reduce internal leakage and increase pump efficiency. These can be time-consuming and expensive as all rotordynamic coefficients must be determined in each case.
Nowadays, accurate simulation methods to calculate rotordynamic coefficients of annular seals are still rare. Therefore, new numerical methods must be designed and validated for annular seals.
The present study aims to contribute to this labour by providing a summary of the available test rig and seals dimensions and experimental results obtained in the following experiments:
− Kaneko, S et al., Experimental Study on Static and Dynamic Characteristics of Liquid Annular Convergent-Tapered Seals with Honeycomb Roughness Pattern (2003) [1] − J. Alex Moreland, Influence of pre-swirl and eccentricity in smooth stator/grooved rotor liquid annular seals, static and rotordynamic characteristics (2016) [2]
A 3D CAD simulation with Siemens NX Software of the test rig used in J. Alex Moreland’s experiment has been made. The following annular liquid seals have also been 3D modelled, as well as their fluid volume:
− Smooth Annular Liquid Seal (SS/GR) (J. Alex Moreland experiment)
− Grooved Annular Liquid Seal (GS/SR)
− Round-Hole Pattern Annular Liquid Seal (𝐻𝑑=2 mm) (GS/SR)
− Straight Honeycomb Annular Liquid Seal (GS/SR)
− Convergent Honeycomb Annular Liquid Seal (No. 3) (GS/SR)
− Smooth Annular Liquid Seal (SS/SR) (S. Kaneko experiment)
In the case of the seals used in S. Kaneko’s experiments, the test rig has been adapted to each seal, defining interpart expressions which can be easily modified.
Afterwards, it has been done a CFD simulation of the Smooth Annular Liquid Seal using Ansys CFX Software. To do so, the fluid volume geometry has been simplified to do a first approximation. Results have been compared for an eccentricity 𝜀0=0.00 for the following ranges of rotor speeds and differential of pressure:
− Δ𝑃= 2.07, 4.14, 6.21, and 8.27 bar,
− 𝜔= 2, 4, 6 and 8 krpm.
Even results obtained have the same trend as the one proportionated by the literature, they cannot be validated as the error is above 5%. It is also observed that as the pressure drop increases, the relative error decreases considerably.
One of the main problematics of the seals tests is the time and money consuming they are. Up to now, there are few tries to do a digitalisation of a test where the seals behaviour can be known.
This work aims to digitally reproduce a seal test to extract their behaviour when working under different operation conditions to see their impact on the pimp’s efficiency. In this thesis, due to the Lomaking effect, the leakage and the forces applied on the stator will be the base of analysis.
First of all, among all the literature available for very different kind of seals and inner patterns, it has been chosen the most appropriate and precise data. The data chosen is “Test results for liquid Damper Seals using a Round-Hole Roughness Pattern for the Stator” from Fayolle, P. and “Static and Rotordynamic Characteristics of Liquid Annular Seals with Circumferentially/Grooved Stator and Smooth Rotor using three levels of circumferential Inlet-Fluid” from Torres J.M.
From the literature, dimensions of the test rig and the seals will be extracted to model them into a 3D CAD software. With the 3D CAD digitalisation, the fluid volumes for a rotor-centred position, meaning without eccentricity, will be extracted, and used. The following components have been modelled:
- Smooth Annular Liquid Seal (Grooved Rotor)
- Grooved Annular Liquid Seal (Smooth Rotor)
- Round-Hole Pattern Annular Liquid Seal (𝐻𝑑=2 𝑚𝑚) (Smooth Rotor)
- Straight Honeycomb Annular Liquid Seal (Smooth Rotor)
- Convergent Honeycomb Annular Liquid Seal (Smooth Rotor)
- Smooth Rotor / Smooth Annular Liquid Seal (Smooth Rotor)
As there is just one test rig, all the components have been adapted to the different dimensions of the seals by referencing some measures. This allows to test any seal with the same test rig.
Afterwards a CFD simulation that will be used to obtain leakage and stator forces. The parameters that will be changed are the rotational velocity of the fluid (2000 rpm, 4000 rpm, and 6000 rpm) and the pressure drop (2,068 bar, 4,137 bar, 6,205 bar, and 8,274 bar).
Those results will be compared to the literature ones, and they will determine if digitalisation can be validated or not. Even though the relative error is higher than 5% but the tendency is the same and it is thought that by changing some parameters the test results can be even closer to the literature ones.