This paper presents a numerical simulation and experiment on the effect of the variable pitch angle on the performance of a small vertical-axis wind turbine (VAWT) with straight blades. The power coefficient of the VAWT was measured in an open-circuit wind tunnel. By conducting two-dimensional unsteady computational fluid dynamics simulations using the RNG k-ε, Realizable k-ε, and SST k-ω models, the power and torque of the VAWT and the flow around the straight blades were also analyzed. The numerical simulation of the power performance results were validated using wind tunnel experimental data. The results of both the numerical simulations and experiments showed that a VAWT with variable-pitch blades has better performance than a VAWT with fixed-pitch blades. The numerical simulation of the performance using the RNG k-ε turbulence model had good qualitative agreement with the experimental results. The numerical simulation was able to capture the flow separation on a blade, and it was shown that a variable-pitch blade can suppress the flow separation on its blades at a tip speed ratio lower than that of fixed-pitch blades. with the NACA0018 can be further improved by setting the wings at an outward angle of 5 degrees. Yamada et al. (2011) have also studied the effects of the camber and thickness of a blade (NACA0020, 3520, 6518, 6520, 6525, 6530, and 8520) on the performance of a small straight-bladed VAWT. Their report showed the mean and temporal torque variation at any azimuth angle of one and two blades.As part of a numerical simulation, Chen and Kuo (2013) have studied the effects of pitch angle and blade camber on the unsteady flow characteristics and the performance of a small-size Darrieus wind turbine with the NACA0012, 2412, and 4412 blade profiles. Their results indicated that the self-starting ability and the moment coefficients of a VAWT that has blades with large cambers (NACA4412) are better than those with the other blades (NACA0012 and 2412). Chen and Zhou (2009) used the SST k-ω model to investigate the aerodynamic performance of a VAWT via a two-dimensional numerical simulation. The results showed the optimum pitch angle for the power coefficient of the VAWT. Aresti et al. (2013) conducted two-and three-dimensional numerical simulations of the performance and flow through a small scale H-type Darrieus wind turbine by using the RNG k-ε, standard k-ε, and standard k-ω turbulence models. The self-starting capabilities of the VAWT were found to increase with the increasing mount angle of attack of the blades. Almohammadi et al. (2013) investigated the mesh independence of the predicted power coefficient of a VAWT with straight blades by employing a two-dimensional numerical simulation. Roh and Kang (2013) investigated the effects of a blade profile, the Reynolds number, and the solidity on the performance of a straight-bladed VAWT by using the numerical procedure of the multiple stream tube method. McNaughton et al. (2014) presented a two-dimensional numerical investigation of a VAWT, wh...

Diesel engined vehicles are one of the biggest causes of air pollution. Exhaust emissions will continue to increase along with the growth in the number of motorized vehicles, especially for commercial vehicles. The main purpose of this study is to determine the quality of fuel can affect the level of smoke density in diesel engines. This research was conducted by testing sampling on a motor vehicle that is commonly used by the public, namely the Mitsubishi L300 in 2007 production using a Smoke Tester. The test mechanism utilizes different fuel variables, namely: Bio Solar with Additive Substances, Solar Dexlite and Pertamina Dex. From the test results, the highest smoke density value was achieved on Bio Solar fuel with additives at 4200 rpm engine speed with a value of 34.1%. Keywords: Vehicles, Diesel Engines, Smoke Density, Fuel Quality, Additives

The very rapid development of the automotive world nowadays has made it a daily necessity for the community, in everyday human life it cannot be far from the name automotive, both in terms of transportation, and all kinds of supporting household needs. This can be seen from the number of motorbikes operating more when compared to other types of land transportation vehicles such as: cars. As we know, all transportation vehicles today still use non-renewable fuels. In line with the growing demand for fuel in the transportation, industrial and household sectors. Then this will result in unfavorable impacts on the environment, namely the residual exhaust gases from combustion. The remaining exhaust gases cause air pollution which can pollute the environment and can even destroy ozone which is very useful for living things on earth. In this study we use a reference concept which is then used as a concept, how is the effect of variations in the addition of ethanol fuel to exhaust gas emissions of Yamaha 125cc motorcycles by using variations in the percentage of ethanol 10%, 20%, 30% and variations in engine speed during testing, at 4600rpm, 5700rpm, and 6200rpm. It was found that the best torque and power were produced at a percentage of 10% ethanol at 6200 rpm indicating a power of 6.4 Hp and a torque of 10.6 Nm, and the best results on 30% preentae ethanol at 4600rpm showed 0.01% CO gas, 37 ppm HC gas, 1.8% CO2 gas and 18.06% O2 gas.

This paper describes the influence of the number of rotor blades the performance of the orthopter wind turbine. The orthopter wind turbine is combination between a drag-type and a lift-type vertical axis wind turbine which each blade combines a rotating movement around its own axis and a rotating movement around turbine's axis. In this case, the pitch of the blades was controlled by using a chain and sprockets arrangement to ensure that the blades rotated around their own axis by 360 degrees during the each two full revolution of the main rotor. To improve the performance of this wind turbine, the number of blades, was investigated by wind tunnel. By conducting two-dimensional unsteady CFD simulations, the power and torque of the vertical axis wind turbine and the flow around blades were also analyzed. The numerical simulation by using turbulence model predicted good agreement of the performance with experiment qualitatively.

Welding is a process of uniting two or more materials into a form of connection using heat energy. Friction Stir Welding (FSW) is a solid-state welding method that can produce high-quality welding joints for some materials with low weldability such as aluminum. The research objective was to determine the effect of process parameters on the distortion and resistance of aluminum AA6061-T651 material through the Brinell hardness test. The FSW tool used has a hexagonal pin geometry. The experimental design used the Taguchi method. This study uses 4 factors and each factor has 4 levels, the elements used are tool rotation speed, welding speed, tool tilt angle, and concave shoulder angle. The responses analyzed are distortion and hardness of the welded joint material. The effect of process parameters on the response was analyzed using ANOVA. The results of ANOVA on distortion obtained the value of Brinell hardness in the weld metal area, and in the TMAZ area. Specimen 13 with tool rotation speed parameters of 3022 rpm, welding speed of 43 mm/min, tool tilt angle of 3.5°, and concave shoulder angle of 2° with a distortion value of 0.117°. Then we get the results of the Brinell hardness of the weld metal which is close to the target of the base metal with the parameter tool rotation speed of 3022 rpm, welding speed of 90 mm/min, tool tilt angle of 2.5°, and concave shoulder angle of 8° with a Brinell hardness value of 75. 7 BHN, and the Brinell hardness value at TMAZ with tool rotation speed parameters of 1208 rpm, welding speed of 65 mm/min, tool tilt angle of 2.5°, and concave shoulder angle of 2° with a Brinell hardness value of 74.7 BHN.