Showing papers by "Dominicus Danardono Dwi Prija Tjahjana published in 2019"

Mini review on the design of axial type eddy current braking technology

Abstract: Eddy Current Brake (ECB) is a type of electric braking that uses eddy current to produce braking forces. This article delivers a solid review of the design of Axial ECB, which is very promising for an alternative braking system. Several types of axial ECB are classified and named as a single disk, double disk, and unipolar model. The classification of axial ECB is based on the design of coil placement, which induces axial area of the disk as well as the electromagnet source. A potential issue for the development of axial ECB is also discussed to explore the braking performance improvement of the axial type ECB. It was highlighted that research on how to change the direction of magnetic field vectors by changing the shape of the pole-shoe on the electromagnetic ECB in axial type has not been widely studied. Therefore, this issue would be interesting for future investigation.

Design and simulation of a combined serpentine t-shape magnetorheological brake

Abstract: A magnetorheological brake (MRB) is a device to dissipate rotational energy using magnetorheological fluids (MRF). MRB can change its braking torque quickly in response to external magnetic field strength. The brake is rotational, utilizing the MRF in shear mode. In this study, the geometrical design of the MRB, magnetic circuit and MRF flow path is addressed. Mathematical models are presented that describe the braking torque of the MRB. A novel prototype is introduced combining T-shape rotor model with serpentine flux magnetic circuit configuration. The rotor member is selected to direct the flux concentration at that location. Serpentine flux configuration is selected to achieve higher torque without increasing the size of MRB by activated more surface area of MRF with the magnetic flux. The finite element method is used to evaluate the magnetic flux density in MRB using FEMM 4.2. FEMM results showed that this novel design could provide sufficient magnetic flux along MRF flow path. Finally, the influence of input current to the MRB on braking torque is investigated. It is found that the braking torque in MRB increases with the increase of the input current. The prototype is formulated as foot-drop prevention orthotic. The MRB would be further integrated into ankle-foot orthoses for post-stroke patients. The design is formulated as a preliminary geometrical design, aiming to obtain the minimum required braking torque.

Failure Analysis of Super Hard End Mill HSS-Co

Abstract: Abstract The failure of tools will make a large impact to the productivity, so it must be investigated to avoid the next failure. In this case, the super hard end mill HSS-Co list 4SE code 6210 was broken when it was used for side milling processing of mild steel AISI A36 with rotation speed, cutting speed and cutting depth of 540 rpm, 0.10 m/min (4 ipm) and 16 mm respectively. Standard procedure of failure analysis was performed including macro-micro investigation using Scanning Electron Microscopy (SEM) with energy-dispersive spectrometry (EDS) attachment, micro hardness test, and Finite Element Methods (FEM) simulation. The results of failure analysis showed that fracture occurred due to stress concentration and micro defects of the super hard end mill. Two parts of fracture surface, rough and fine surface were found. Based on SEM-EDS investigation, it was known that the content of tungsten (W) and cobalt (Co) elements on the rough and fine surface was inhomogeneous. Excessive Co and W elements appeared on the fine surface while they disappeared on the rough surface. Excessive Co will diffuse with tungsten and carbon and lead to the separation of tungsten and carbon elements, so it greatly destroyed the alloys and lead to form the non-stoichiometry carbide points. Hence, the defective manufacturing processes which made the elements distribute inhomogeneous is concluded as the reason of the super hard end mill failure.

Performance investigation of the crossflow water turbine by using CFD

Abstract: Crossflow water turbines can be an alternative energy for the development of pico-hydro power plants. Multiple interactions that occur from the flow of fluid that collides with the blade is one of the advantages of the crossflow type so that this turbine has a high power coefficient. The power coefficient of a turbine is influenced by several factors, including the blade depth ratio and blade number. The objective of this research was to study the effect of blade depth ratio and blade number on the power coefficient of crossflow water turbines. This research was done in 2 dimensions method (2D) using ANSYS Fluent software. Variations of blade depth ratios used in this study were 10%, 20%, and 30%, while variations of the blade number were 16, 19, and 22. Each variation was tested at tip speed ratio (TSR) 0, 0.109, 0.218, 0.327, and 0.436 with a constant water velocity of 3 m/s. The results of this research indicated that the crossflow water turbine at TSR 0.436 with blade depth ratio of 10% and blade number of 16 generated the highest power coefficient, which was equal to 0.187.

Study of the wind farm arrangements and wake characteristic using numerical simulation for crossflow wind turbine

Abstract: Among of the renewable energy sources, wind energy is the fastest growing. To achieve economic scale, the wind turbines are usually built as wind farms. There are some designs of wind farm that most of them are proposed for horizontal axis wind turbine type. However, there is no wind farm design for vertical axis wind turbine, such as crossflow wind turbine, yet. The crossflow wind turbine could be used to extract wind energy in low wind speed and has a high power coefficient. In order to be able to work perfectly, a proper arrangement of wind turbines on the wind farm should be determine to decrease wake. The objective of this research was to study the effect of the crossflow wind turbine arrangement in wind farm with 2 dimensional numerical analysis using ANSYS FLUENT CFD software. The variations of the wind farm in the study were aligned and staggered configuration, in which the distance between the turbines were 0.5D, 1D and 1.5D, where D was the turbine outer diameter. Each variation was tested at the wind speed of 2 m/s and tip speed ratio (TSR) of 0.1. The study revealed that the best arrangement of crossflow wind turbine configuration is staggered arrangement within the distance S1:S2 of 0.5D:0.5D. The wake effect in staggered arrangement doesn’t disturb surrounding the crossflow wind turbine in wind farm area, because the wind is blowing in streamline flow. The appropriate distance between wind turbines would increase the power density of the wind farm. Compare to an isolated crossflow wind turbine, there is 10% increase of power density.

Slow pyrolysis of Tectona Grandis and Albizia Chinensis sawdust with thermogravimetry analysis

Abstract: Sawdust waste has a great potential to be developed into alternative energy in Indonesia. It has varying methods to process it into certain products, e.g., pyrolysis process. However, the sawdust pyrolysis process still not very popular, especially not so many people understand its thermal characteristics. In this study, thermogravimetry analysis was carried out to analysis three samples of sawdust, i.e., Tectona Grandis Sawdust, Albizia Chinensis Sawdust, and the mixture of both sawdust. This research was conducted to obtain pyrolysis characteristics, including devolatilization profiles and kinetic energy. This study used three samples each has a mass of 20 grams. Each sample is heated in a furnace with a heating rate of 15 °C/min until the temperature reaches 600°C and hold it for 10 minutes. During the data retrieval, the furnace flowed with nitrogen, thus the condition of no oxygen is present in the reactor. The results of this study indicate that the mixture of Tectona Grandis and Albizia Chinensis has the highest activation energy value of all pyrolysis samples with 80.79 kJ/mol.

Combustion characteristics of Albizia Chinensis and Tectona Grandis sawdust and a mixture of both using thermogravimetry analysis

Abstract: Biomass is an alternative energy that can be produced from various sources. In order to obtain the best raw materials needed to produce the biomass, a characteristic test should be conducted. In this experiment, several materials are tested using the combustion characteristic test; The sawdust waste of Albizia Chinensis, Tectona Grandis, and the mixture of both of them. A 20-gram sample is heated up in the thermo-macrobalance furnace with the heating rate of 10 oC/mins until the masses are no longer reduces significantly. The thermogravimetry analysis is also conducted to understand the fuel resistance of a sawdust waste. The result shows that the mixture of Albizia Chinensis and Tectona Grandis has a higher fuel resistance than both of Albizia Chinensis and Tectona Grandis, with ITVM (initiation temperature volatile matter) values is 183.7 °C, ITFC (initiation temperature fixed carbon) value is 223.8 °C, PT (peak temperature) value is 378.6 °C, BT (burning temperature) value is 441.9 °C, and burning the char reaches a temperature of 620.1 °C. This shows that the mixed sample of Albizia Chinensis-Tectona Grandis has a burn resistance at high temperatures