Aplikasi CFD - Josiah Enrico S (1906356286)

Contoh Aplikasi Dynamic Mesh dan 6DoF - Aplikasi Modelica/19 November 2020

Vertical Axis Wind Turbine

VAWT atau singkatan dari Vertical Axis Wind Turbin adalah salah satu mesin tenaga yang mengubah energi mekanis dari aliran angin menjadi kerja. ciri khas mesin tipe ini adalah turbin memiliki poros yang tegak lurus dengan aliran fluida dan vertikal dengan tanah seperti gambar di samping. Desain ini memungkinkan aliran angin dari arah manapun dapat dimanfaatkan untuk menjadi kerja asalkan tidak sejajar dengan poros turbin ini. Dalam insdustri, mesin ini juga dikenal sebagai "transverse axis wind turbine" atau "cross-flow wind turbine." Dalam artikel ini, diperlihatkan simulasi komputer yang menggambarkan dinamika fluida ketika turbin sedang beroperasi (dengan variasi massa jenis).

Untuk mengimplementasikan simulasi CFD dalam desain berikut, digunakan metode Dynamic Mesh dan 6DoF (6 Degree of Freedom). Dynamic Mesh berarti mesh tidak rigid tapi fleksibel misalnya bergerak dalam suatu jalur atau berputar dalam suatu axis, sedangkan 6DoF berarti simulasi dilakukan dengan memperhatikan kebebasan gerak suatu mesh ketika dialiri fluida (Dalam 3 dimensi kebebasan ini berderajat 6)

Bentuk Meshing Geometri

Simulasi Dengan Perbedaan Massa Jenis

rho=1,2 kg/m^3	rho=4.8 kg/m^3

Analisa

CFD Simulation for Economizer Hopper - Aplikasi Modelica/24 November 2020

Economizer Hopper adalah salah satu fitur ducting yang biasanya terdapat dalam PLTU yang menggunakan batu bara. Fitur ini berfungsi menangkap dan menampung fly ash (abu terbang) yang dihasilkan pembakaran batu bara. Tanpa Economizer Hopper, debu tersebut bisa menimbulkan berbagai masalah operasional seperti menghambat aliran fluida di preheater, merusak blade IDF dan Guide Vane, menumpuk di ducting dan bahkan juga mencemari lingkungan. Dalam artikel ini, akan ditunjukkan simulasi CFD yang menggambarkan perbedaan efektifitas sistem yang menggunakan Economizer Hopper dan tanpa Hopper.

Model Simulasi dalam CFD:

• 3D
• Transient
• Incompressible
• Turbulent
• No Heat Transfer
• Multi-phase

Simulasi Economizer Hopper

Economizer dengan Hopper	Economizer tanpa Hopper

Analisa:

CFD Simulation for Cyclone Separator - Aplikasi Modelica/26 November 2020

Cyclone Separator

Cyclone separators or simply cyclones are separation devices (dry scrubbers) that use the principle of inertia to remove particulate matter from flue gases. Cyclone separators is one of many air pollution control devices known as pre-cleaners since they generally remove larger pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on. In addition, several cyclone separators can operate in parallel, and this system is known as a multi-cyclone.

It is important to note that cyclones can vary drastically in their size. The size of the cyclone depends largely on how much flue gas must be filtered, thus larger operations tend to need larger cyclones. For example, several different models of one cyclone type can exist, and the sizes can range from a relatively small 1.2-1.5 meters tall to around 9 meters —which is about as tall as a three-story building.

source: https://energyeducation.ca/encyclopedia/Cyclone_separator

Verification:

Validation:

Effect of Air-Particle Density Difference

Air-particle density difference (ρp − ρg) is a key parameter in cyclone efficiency calculations. Efficiency prediction by Li and Wang modified model for different particle density is shown in Figure 4. The numerical simulation result shows that the critical particle size, dpc, for particle with density 3000 kg/m3 is around 2.2 µm and is around 4.2 µm for 1000 kg/m3 particle density. A bigger particle density tends to result in a larger air-particle density difference since the air density remains constant. Bigger air-particle density difference led to a higher resultant centrifugal force acting on the particle, and the higher centrifugal force in cyclone has led to higher separation efficiency. It can be concluded from this finding that the bigger the particle density is, the smaller the critical particle size (dpc) would be obtained, or by other means, the sharper the separations would be.

Effect of Inlet Velocity

Inlet gas velocity, vi, is an important factor for cyclone sizing in order to achieve a desired separation efficiency. Inlet cyclone velocity is a result of dividing the inlet gas flow rate, Q, to the cyclone inlet area (a.b). At a high flow rate, the inlet velocity becomes larger thus, the tangential velocity, vi, also increases. The cut-off diameter varies inversely with the square root of the inlet velocity. The effect of inlet velocity to the cyclone performance is shown in Figure 5. It shows that for the identical size and configuration of cyclone, the higher the gas inlet velocity is, the sharper the efficiency would be. However, a very high inlet velocity would decrease the collection efficiency because of increased turbulence and saltation/re-entrainment of particles. Shepherd and Lapple recommended that the optimum cyclone operating velocity is around 18 m/s. However, the range of practicable cyclone inlet velocity is around 15 – 30 m/s.

Source: https://www.researchgate.net/publication/314555880_Prediction_of_the_Effect_of_Dimension_Particle_Density_Temperature_and_Inlet_Velocity_on_Cyclone_Collection_Efficiency

Simulation Result:

Variation of Particle Diameter

Analysis:

As we can see in the simulation above, the geometry of the cyclone separator will generate swiveling fluid inside the cylinder. This cyclone-like flow is started by the tangential velocity of fluid entering the inlet of the chamber. While whirling along the chamber surface, gravity takes place by driving the multiphase stream downward creating a vortex. Since larger particles tend to have heavier mass relative to the density and worse compliant to the high-speed spiral motion of the vortex, the particles hit the inside walls, lose momentum, and drop down into the bottom of the container. In reverse, the cleaner gas or fluid with smaller particles (blue particles) go along the cone-shaped wall following the high-speed movement of the vortex, float upward and escape out the top of the chamber. This effect is also related to the inertia of every particle itself, less for the smaller particulate and more for the larger ones. Unfortunately, we cannot see the complete upward movement of smaller particles as the duration of the simulation is not long enough respectively, but at the end of the illustration, we may see a glimpse of those particulates (blue particle) are raising upward.

Project Synopsis - Aplikasi Modelica/1 Desember 2020

As elutriator, or an apparatus used to separate suspended solid particles according to size, have been used in the plastic industry regarding dust particles such as streamer or angel hair elimination, there is a need to observe the effectiveness of this control process to produce cleaner plastic pellet. In doing so theoretically, some recent studies show differences in particle size are exploited when they are subjected to an upward flowing current of fluid, leading to separation into size-based underflow and overflow streams. The tendency of a particle to report to either stream is dependent on its terminal sedimentation velocity, as well as the upward velocity of the fluid. Where the terminal velocity exceeds the fluid velocity, the particle will settle against the current and report to the underflow and vice versa. This research will recreate the flow using computational fluid dynamics application to help us understand the variation of particle size or density of particles leading to different sedimentation velocities in the separation process.