Turbine oil is normally used in gas turbines and other applications that require the highest quality turbine oil. Turbine oil purity remains a concern because the oil must be substantially clean for optimal performance. The present inventions of turbine oil filtration are broadly categorized under different types of filtration methods depending on its purpose or applications.
The existence of iron components in industrial turbine oil makes magnetic filters an effective tool for capturing and recycling small magnetic particles. The method used in designing the magnetic filter is modeling and simulation software. After performing calculations and software simulation, the best method for filtering particles in used turbine oil is to use an offline magnetic filter. The current inventions of turbine oil filtration are generally categorized under different types of filtration methods depending on their objectives or applications.
Almost all machines today use lubrication to smooth the operation of the machine, and one of the most important media in turbine oil. The author had simplified the process by focusing only on removing particles in the used turbine oil by using magnet in off-line filtration system.
Objectives and scope of Study
This problem had inspired the author to develop a new design of magnetic filter, which is smaller in size and has a simpler process for removing particles from used turbine oils. Magnetic filter is a filtering device in which the filter screen is magnetized to capture and remove fine iron from liquids or liquid suspensions being filtered.
Method of removal particles from used turbine lubrication oil
One of the typical problems with circulating turbine oil is a change in color from yellow to dark green after about three months of service. Young and Roberton (1989) had carried out a laboratory inspection of the oil and indicated that the dark green oil contained a significant amount of sediment consisting of iron, aluminium, phosphorus and silicon (quartz). The color change can be explained by the combination of the primary dyes, yellow from the turbine oil, and the bluish tint of the pollutants, producing a dark green color. Due to the massive concentration of metal debris, it is recommended to change the oil and examine the cause of rapid wear.
It shows that continuous effective monitoring of turbine oils in use is required to maintain effective turbine lubrication and ensure long turbine oil life. Sedimentation filter A sedimentation or gravity bed filter ensures that contaminants heavier than oil can settle to the bottom of a container under the influence of gravity. Centrifugal Filter A centrifugal oil cleaner is a rotating sedimentation device that uses centrifugal force instead of gravity to separate contaminants from the oil.
Compared to other filters, such as mechanical filters and membranes, magnetic filters have other significant design and regime advantages, although they cannot be used effectively in all industrial areas. The unit removes metal cuttings from the transmission fluid using an auxiliary housing that is attached to the transmission housing solely by magnetic attraction, and the fluid moves in and out of the auxiliary housing during normal transmission operation.
Type of magnet
This study uses an electromagnet instead of a permanent magnet and is attached to the outer tube parallel to the direction of fluid flow. A mixed flow propeller will work equally well if mounted vertically or at any angle (Mittai, 1995).
Design of magnetic filter
The fluid flow can be defined manually by long complicated mathematical formulas such as discretization method, but with the ongoing research, a simpler method had been invented using computer software. Piero and Emesto (1997) had resolved the effect of low impeller clearance from the bottom with changing stirring speed by using exponential function. Derksen (2003) had published a study on solving solid suspension problem in stirred tank using numerical simulation method.
Taking water as the working fluid and the glass beads as the solid particles, the behavior of the particles is observed and how the flow of the fluid is changed by the presence of the particles. In this study, the flow is driven by a Rushton turbine coupled to a Lagrangian description of spherical, solid particles immersed in the flow. Sytjanen, Haavisto, Koponen, and Manninen (2009) also published measurements and modeling of particle velocity and concentration profiles of sand water slurry in stirred tank using CFD.
The time-dependent 3D studies of the slurry flow in the tank were carried out using algebraic slip mixture model and full Eulerian multiphase model. The agreement of particle velocity components was generally good in the center of the tank, while some deviation occurred near the wall. The relation between number of iterations and time step is mentioned in Computational Fluid Dynamics Review book by Hafez, Oshima & Kwak (2010).
As the book states, larger time steps can be used efficiently provided enough iterations are performed to converge the solution and eliminate any spurious behavior. Magnetic Filtration: Production of Dan Norrgran (2008) Magnetic Field for Effective Particles Limited particle size and collection of high purity raw materials is determined by the magnitude of the particle's magnetic field values. Solid suspension in turbulent ~avi, Juvekar Analyzed the behavior of solid suspension Need for a high level tank: UVP measurements and and Vivek (2011) in turbulent tank using machine and time of ultrasound velocity technology.
Effect of layers from below Piero and IERnesto Solve the effect of layers from below fan Boring and complicated fan clearance on the (1997) clearance with changing impeller speed by. Numerical simulation of solids Derksen (2003) Study on solving problem of solids No magnetic components and suspension in a stirred tank suspension in stirred tank using numerical different fluid types. Particle velocity and SyYjanen, Haavisto, Study of particle velocity and volume No magnetic components and concentration profiles of sand- Koponen and fri~:tions using CFD simulation.
The choice of an unstructured grid versus a structured one was made due to the tact that in a complex flow such as the present, details of the flow field everywhere in the tank and especially in the rotation area of the impeller and around the magnets must be captured. After the Gambit file is introduced to Fluent software, the grid is checked to determine the modeling part of Gambit. By checking the grid, the volume of the design previously modeled should be the same as the grid appears in Fluent.
In Flow simulation, turbulent flow is modeled using k-e model with wall functions as shown in Figure 3.7. The grid will be split into two reference frames to account for stationary and rotating part. The rotating part of the grid contained the impeller blade, and the stationary part contained the magnets and the tank.
The gravitational acceleration is set to -9.81 m/s2 on the z-axis because the fluid is directed downward.
- The best method to remove particles from used turbine oil
- Design of magnetic filter
In this project, the model consists of the following boundary conditions as given in Figure 3.10. Below the frame of reference there are two options which are absolute or relative to the Cell Zone values. For this project, a magnetic filtration method is used to filter used turbine oil because it contains iron particles that can be best filtered using magnets.
Its flexibility to be in any shape is vital because this project requires magnets that can be assembled into the small size of the magnetic filter. The power of the permanent magnet is lower than the electromagnet, but it is sufficient for magnetic filter applications and can be manufactured to produce stronger fields than similarly sized electromagnets. The permanent magnet material with suitable magnetization value is barium iron oxide magnet, BaFe12019. Barium iron oxide magnet is a part of the composite magnet that is cheap and can be easily produced, which makes it the best choice.
Range of shaft speed is used to observe the flow pattern in the rotation zone. The fan rotation speed is started at 0.603 rad/s (based on calculations). Figure 4.2 shows the X velocity at the initialization of 0.603 rad/s shaft speed. When shaft speed is increased, the oil will flow faster into the tank and increase the radial velocity.
At a shaft speed of 0.603 rad/s, the oil flow can be calculated depending on the oil volume in the tank. As shown in Figures 4.3 and 4.4, there are particles flowing around the impeller with zero velocity. The area that can be looked at to solve this problem is to change the type of impeller or adjust the shaft speed.
The volume of oil that can be cleaned per time is approximately 0.ot m3 based on the tank dimensions. The simulation shows that at a shaft speed of 0.603 rad/s the particles will move in the tank and be attracted to the magnets. The recommendation that can be made to improve the results is to model the exact design of a mixed type impeller.
Automatic devices can be used to check the number of particles attracted by the magnets instead of reading results from simulation. Laboratory tests can be performed to observe the number of particles that can be filtered.