Cable-Driven Parallel Robot (CDPR) with mobile crane can be an alternative solution for helping evacuation process in post-disaster sites. This paper aims to carry out the trajectory planning of CDPR with mobile crane and hence the reconfiguration of mobile crane can be executed to avoid instability. This instability occurs due to high cable tension. Trajectory was generated based on fifth-degree polynomial that provides position, velocity, and acceleration profiles of the end-effector. Then, the end-effector moves along the trajectory while the mobile crane adjusting its length. The prototype of CDPR with mobile crane was built to verify the theoretical results. Reconfiguration of CDPR is also proposed to lift higher payload capacity while maintaining stability of the mobile crane.
The feature selection in classification tasks as a need for diagnosing a fault in rotating machinery exceedingly plays a very notable role in the machine learning framework. Consequently, this study proposes a combination of a correlation technique with exhaustive search as a feature selection method for diagnosing rotating machinery faults. In any case, this method can be called as a hybrid method because it combines between the correlation technique as a filter method and an exhaustive search as a wrapper method. The correlation of each feature with the target of labeling normal and abnormal information is measured by Pearson’s correlation matric, in which abnormal conditions indicate a failure in the rotating machinery. The top five best correlations at this stage are taken as the selected feature in the filtering stage. Based on these features selected, each feature is combined and its performance is considered through the training of a classification model. The combination of features with the highest accuracy is the final selected feature subset. Finally, the proposed method is able to successfully demonstrate the diagnosis of rotating machinery faults with normal and abnormal classification.KeywordsCorrelation techniqueExhaustive searchFeature selectionRotating machineryFaultDiagnosisClassifications
There are two flow control methods for reducing drag force on the cylinder: active and passive control. The passive control method regulated the airflow by varying the body shape or installing additional rods or surface roughness. This airflow control procedure is applied to the returning blade of the Savonius wind turbine by installing a circular cylinder to reduce pressure drag and improve its performance. A circular cylinder varies with a stagger angle −10° ≤ α ≤ 90° and within the center to a center distance fixed at S/D = 1.4 were investigated numerically. The transient numerical calculation was performed with Ansys Fluent 19.1 to identify the dynamic nature of the 2D modeled turbine. The numerical calculation set with constant freestream velocity (U∞) 5 m/s at Reynolds number Re = 105.000. The two-equation URANS and k-ε enhance wall function turbulence models are used in this simulation. The simulation was also verified with experimental data and showed healthy agreement so that the boundary conditions, grid, turbulent model, and solver setup settings can be maintained for further consideration. The analysis is carried out on the power coefficient and moment coefficient compared between conventional cylinders and cylinders with staggered cylinders. The result shows that staggering cylinder circular enhances the conventional turbine performance by 9% higher. The optimum staggered angle was founded at α = 70° within TSR = 0.8.KeywordsSavonius wind turbineCylinder circularCFDPressure dragCoefficient of power
The present work focuses on the performance modeling of surface grinding to attain an optimum parameter setting for the minimum coefficient of friction and surface roughness. The experimental data were collected during the surface grinding process using dry conditions and minimum quantity lubrication (MQL) as a clean technology lubricant. The usage material was SKD 61 tool steel. The varied surface grinding parameters were the depth of cut and table speed, wherein each had three levels. The surface grinding operation was performed by using a full factorial design 2 × 3 × 3. Backpropagation neural network (BPNN) was first applied to obtain the modeling of the surface grinding experiment, the objective function, the predictions of coefficient of friction, and surface roughness. The objective function is then modified into a fitness function. Finally, this fitness function is utilized in multi-objective optimization using the teaching–learning-based optimization (TLBO) method to attain the surface grinding parameters’ levels that simultaneously produce a minimum coefficient of friction and surface roughness. Based on our experimental results, the combination of BPNN-TLBO can be applied to simultaneously minimize the coefficient of friction and surface roughness in the grinding of SKD 61 by implementing MQL and setting the feeding speed at 150 mm/s and the depth of cut at 0.01 mm. As the result, the minimum surface roughness is 0.376 μm, and the coefficient of friction is 0.333.KeywordsBackpropagation neural networkClean technologyMinimum quantity lubricationSurface grindingTeaching–learning-based optimization
There is a power plant with a capacity of 3 × 315 MW which has a tangential pulverized boiler type. This power plant uses an LRC and MRC Coal type for the fuel to produce steam which is used to rotate steam turbine that coupled with a generator to produce electric power. The Indonesian government is striving used biomass to decrease using coal fuel until 23%. Previous sub-critical power plant not designed to be a co-firing fuel, and the best way to implement that system is using the direct co-firing method. This power plant has been an experiment using biomass until 1%, and there is no significant effect for the equipment. For the effectiveness combustion still need to do research. In this research are using 3 types fuels, 97.5% coal and 2.5% biomass, 95% coal and 5% biomass, 92.5% coal and 7.5% biomass. And it is also using excess air variation of 15%, 17%, and 20%. Efficiency’s formula was carried out to find optimum variables with biomass and excess air at this power plant that the CFD numerical analysis was carried out to find an optimum model to analyze in more detail the effect to temperature contour, velocity particle combustion. In the end, we obtained that the efficiency biomass is still underusing coal but 97.5% biomass is the best for efficiency between the other variable.KeywordsPulverizerCoal pulverizedExcess airBiomassCo-firingCFD
The vehicle suspension system must isolate or reduce the vibrations that occur in the vehicle body due to road disturbance. Series Active Variable Geometry Suspension (SAVGS) is a suspension system that offers much better performance than passive suspension and can overcome the disadvantages of active suspension. This study will discuss the effect of single link length on SAVGS, especially on comfort and road-holding performance. The suspension system is modeled as a quarter car, where the effect of a single link length is analyzed in the form of equivalent stiffness and damping. The linear quadratic regulator is considered for the control design. The control system's performance was tested on a non-linear model with road disturbances consisting of bumpy roads and highway roads. The simulation results show that the longer the single link, the greater the vehicle's comfort and road holding on the vehicle increase. However, the longer the single link, the more the control input is needed.KeywordsVariable geometry suspensionLinear quadratic regulatorActive suspension
Refuse derived fuel (RDF) is waste that can’t be reprocessed. One way to use RDF is to convert it to alternative fuels. A gasification is a tool that can be used to convert RDF into syngas (gas fuel) so that it can be used for internal combustion engines and power plans. This research was conducted using a downdraft gasifier with a three-stage gasifying agent with variations in the air ratio (AR) at the air intake in the pyrolysis, oxidation, and reduction zones (0:10:0, 2:6:2, 1:6:3, 3:6:1, 2:5:3, 3:5:2, 1:8:1, 2:7:1, and 1:7:2), besides that the temperature control system in the oxidation zone is varied from 600 ℃, 700 ℃, 800 ℃, 900 ℃, to 1000 ℃. Parameters in the gasification process were measured such as combustible syngas composition, LHV syngas, and tar content. The results obtained using AR 1:7:2 and setting 1000 ℃ are the most optimal results, where the highest combustible syngas such as CO is 2.67 %vol and H2 is 11.54 %vol while the LHV was obtained at 4201.02 kJ/kg and the tar content was obtained at 61.89 mg/Nm3. The presence of the air is limited to the pyrolysis and reduction of the gasification process. KeywordsRefuse derived fuel (RDF)Multi-stage downdraftAir ratio (AR)SyngasGasification temperature control
In the new supercritical boilers, a combination of tubing is used to achieve mechanical integrity at the most economical cost. The boiler uses dissimilar metal welding (DMW) to obtain the joint. The DMW process poses several challenges that are caused by differences in the physical properties of the base metals. In the present work, the effect of the type of filler metals (Inconel ERNiCr-3 and ERNiCrMo-3) and a buttering process on the creep properties of DMW between ferritic steel T91 and austenitic stainless steel 347H characteristics are presented. Creep testing results show that ERNiCr-3 produced slightly better creep strength compared with ERNiCrMo-3. Nevertheless, the buttering layer has a significant impact on the creep properties. The data was analyzed using the Weld Strength Reduction Factor using time initiation of tertiary creep (WTRF) to material capability. WTRF of direct Welding with ERNiCr-3 and ERNiCrMo-3 both are 0.32 and at 600 °C application. WTRF of ERNiCrMo-3 is 0.6 and on the minimum requirement. WTRF of buttering using ERNiCr-3 is 0.65, and above the minimum requirement of the tube, boiler operated at 600 °C application.KeywordsDMWT91347HButtering layerInconel
A multiplanar tubular joint is the most common tubular joint type of jacket offshore platforms. Nevertheless, previous studies subjected to this topic were relatively limited. The chosen tubular joint analyzed in this paper is obtained from an existing minimum jacket platform and numerically analyzed by using FE model. This research has the objective to obtain stress distribution along the brace-chord intersection lines of a two-planar DKDT welded tubular joint under three modes of axial loading: tension, compression, and combination of both. The stress distribution will be evaluated at the weld toe of both on the chord and the brace sides. The result shows that stresses occurred on the chord side are greater than on the brace side. Though the stress distribution trend for both side of the weld toe is close to similar, there are several shifting on the exact location. Hotspot stress from the tension axial loading case has the greatest value followed by compression axial loading and combined axial loading cases.KeywordsDKDT multiplanar tubular jointFinite element analysisLocal stress distribution
Many investigations had been done both numerically and experimentally, on the characteristics of multiple-arranged cylinders especially in terms of the induced fluid forces and responses caused by external fluid flows acting on them. This paper discusses the investigation result on induced drag of two cylinders helically wrapped around by triple rods with certain gap in air flow fields. The model cylinders were installed in the test section of a wind tunnel as a side-by-side arrangement and treated as roll supports at ends of the cylinders. The model was executed at subcritical regime of incoming uniform air flow acting perpendicular to the cylinders that related to Reynolds number of 3.9 × 104 and evaluated for different gaps between the cylinder of 1.75D, 2.0D, and 2.50D, respectively, where D is diameter of the bare cylinder. Load cells were used for measuring the drag occurring on the cylinders. For all gap variety evaluated results demonstrated that greater coefficient of drag (CD) happened in the two cylinders which was caused by more prominent interference between them. The CD increased greater than other gaps for the cylinder’s gap of 2.0D that was well confirmed against others relevant works. For this side-by-side configuration, the CD of the lower and upper cylinders significantly increased in contrast with the single cylinder case by 55.8% and 55.5%, respectively.KeywordsExperimental studyDragSide-by-side arrangementTriple rods
The wind turbine is owned by PT Pembangkit Jawa Bali (PT.PJB); the wind turbine is a research project conducted by PT. PJB. This study aims to determine the appropriate airfoil for a horizontal type wind turbine installed at the Wind Power Plant—Tulungagung, East Java. The installed turbine airfoil cannot produce the expected power at wind speeds, at the site, in the range of 3–5 m/s. Three types of airfoils, namely SD 7080, SG 6043, and NACA 4412, are proposed to be selected as the best compared to each other and with the installed turbine over the wind speed range at the site. A QBlade software was used to assess the performance of the four types of airfoils. The simulation results show that the SD 7080 type airfoil can produce the highest power compared to the other three airfoils; it gives 49.77 Watts at a wind speed of 5 m/s. This power is 4.25% higher than the airfoil of the installed turbine.KeywordsHorizontal turbineSimulationQBladeAirfoil SD7080SG6043And NACA 4412
This paper will discuss computational fluid dynamics (CFD) modeling based on a 400 MWe boiler with the once-through tower type which is operated using low-rank coal to determine the effect of secondary air and primary air (SA/PA) ratios on boiler performance. This model was made with confidence after conducting an independence test and validation data on the boiler design. Then the boiler is simulated with SA/PA ratio conditions with different values, namely, 4.89, 3.87, and 3.15. The results show that the recommended SA/PA ratio, in this case 4.89 and 3.15, indicates a lower temperature value and lower flue gas flow velocity, which is also related to the ideal gas. The heat is too high which can potentially cause local heating and slagging in the heat exchanger area. However, low temperatures also indicate a decrease in boiler efficiency. It can be concluded that the SA/PA ratio based on recommendation can produce a temperature that is not too high which is good enough for avoiding slagging, fouling, and local heating but can reduce the efficiency of the boiler. where the low temperature is caused by the increasing number of primary air used can reduce the temperature in the combustion chamber. KeywordsSA/PA ratioCombustionComputational fluid dynamics
Energy is a basic need that cannot be separated from human’s life. Almost all sectors in life require energy to meet human needs. One of the renewable energy sources is wind energy. Offshore wind turbine is a renewable energy source that recently has developed rapidly. Wind turbines built offshore have several advantages over onshore. To support the offshore wind turbine, there are several structural options that can be used. The jacket structure can be used for medium to deep seas. The jacket structure that supports the offshore wind turbine is composed of steel tubular members that are joined together by welding will then receive various loads acting on the jacket structure that finally will dictate the integrity of the structure. The purpose of this study is to investigate local stress distribution of critical tubular joint of an offshore wind turbine jacket by using finite element model. Normally, there are two conditions of operation on wind turbine, which are operating when the environmental conditions are normal, and parked when the environmental conditions are extreme. The result showed interesting local stress distribution due to all three types of loading which are axial, in-plane bending moment (IPB), and out-of-plane bending moment (OPB) loading conditions.KeywordsRenewable energyOffshore wind turbineJacket structureTubular jointLocal stress analysis
Oxyfuel combustion is considered to be one of the most effective methods to improve thermal efficiency for high temperature processes such as boiler water of steam power plant. In the oxyfuel combustion, the combustion characteristics such as temperature and CO2 emission are largely influenced by the process parameters such as the mixing between fuel gas and oxygen and the nitrogen content in the oxidant and fuel. A numerical simulation of 200 MW gaseous tangential firing boiler with varying O2 content 25%, 30%, 35% is presented. Simulations demonstrate the characteristics of temperature distribution and CO2 form rate in the furnace. The results show that by increasing O2 percentage in air combustion there is an increase in temperature level and CO2 forms rate by 6.8% and 13.92% in Oxy25, 16.9% and 15.02% in Oxy30, and 19.14% and 15.72% in Oxy35 compared to airfuel combustion.KeywordsOxyfuelGas fired furnaceCFD
An integrated approach has been applied to predict and optimize multi-performance characteristics, namely, cutting force (CF) and surface roughness (SR), in the end-milling process of glass fiber-reinforced polymer (GFRP) composites. The experiments were performed by varying spindle speed, feeding speed, and depth of cut. The quality characteristics of cutting force and surface roughness were the smaller, the better. Full factorial design 3 × 3 × 3 was used as the design of experiments. Backpropagation neural network (BPNN) was used to model the end-milling experiment and also to determine the objective function. This objective function will be modified into a fitness function optimized by using a differential evolution algorithm (DEA) to find the combination of drilling parameters’ levels that yield minimum cutting force and surface roughness simultaneously. As a result, the minimum cutting force can reduce the energy consumption, and the end-milling process can be performed with higher energy efficiency. Based on BPNN-DEA, the depth of cut of 2 mm, the spindle speed of 4797.5 rpm, and the feeding speed of 579.7 mm/min can simultaneously minimize the cutting force and surface roughness in the end milling of GFRP.KeywordsGlass fiber-reinforced polymerEnd millingBackpropagation neural networkDifferential evolution algorithmEnergy consumption
Photocatalytic degradation of Methylene Blue (MB) by zinc oxide/zeolite socony mobile-5 (ZnO/ZSM-5) composites was investigated. The ZSM-5 material was synthesized from red mud by a two-step hydrothermal method to which ZnO loadings at different mass ratios were subsequently performed. Characterizations using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy were carried out to identify the formation of ZSM-5 and ZnO/ZSM-5. ZSM-5 and ZnO/ZSM-5 have cubic microcrystallite morphologies. ZnO loading in the ZnO/ZSM-5 composites was successfully performed and confirmed by the appearance of wurtzite peaks in the XRD spectra that matched the Joint Committee on Powder Diffraction Standards data. The presence of ZnO in ZSM-5 leading resulted in a decrease in the surface area and pore size as confirming by nitrogen adsorption-desorption isotherm experiments. The band gap of the samples was measured using UV-Vis diffuse reflectance spectroscopy. The optimum photocatalytic degradation of MB was observed at a ZnO loading of 34% w/w dubbed 34-ZnO/ZSM-5. The influence of the initial concentration of MB was also investigated at 80, 90, and 100 mg L − 1 using 34-ZnO/ZSM-5 and ZSM-5. Liquid chromatography–mass spectrometry characterization was performed to analyze the degradation products.
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Kampus ITS Sukolilo, 60111, Surabaya, East Java, Indonesia
Head of institution
Prof. Dr. Ir. Mochammad Ashari
031-5994251-54, 5947274, 5945472 (Hunting)