Applied Mechanics and Materials Vol. 889

Abstract: This paper presented vibration analyses of a tapered composite thin-wall box beam with rectangular section. In the numerical results, the effects of taper angle on natural frequencies and the corresponding mode shapes, transient responses of the beam were considered. The algorithm and Matlab code using nine nodded rectangular isoparametric plate element with five degree of freedom per node developed to solve the problems.

Abstract: This paper analyzed how capacitor has an effect on the hybrid ignition system; especially the accumulated energy. Matlab was used to simulate the primary current, self – induced emf, oscillation frequency and accumulated energy. The experiment data - primary current, self-induced emf, oscillation frequency and dwell time - was collected via PicoScope 4425 Automotive Oscilloscope. Simulation results show that the accumulated energy in capacitors is greater than the required ignition energy, which ensure hybrid system working fluently.

Abstract: This paper indicates the early experimental results of a Ricardo model CNG engine R&D activity in Vietnam, the experiments were mainly focused on the effects of compression ratio on operating parameters of the tested single cylinder CNG engine particularly designed and fabricated for varying compression ratio purpose. The compression ratio was set in the range of ε = 10 to 15 with the change step of Δε = 1. For each compression ratio, the engine speed were varried from 1000rpm to 2200rpm with the change step of Δn = 200. The early spark angle was also changed to find out the maximum break torque. The limitation of compression ratio and engine speed at each operating point was determined by vibration signal and abnormal sound. The experimental results indicated the early spark angle must be adjusted premature in case of compression ratio and/or engine speed enhenced. Especially, the portion of indispensable power to perform the compression stroke is smaller in comparison with the portion to execute the both strokes of intake and exhaust. In addition, the shape of combustion chamber affected strongly the operating characteristics also found in this study.

Abstract: Aeroelasticity on airplane wing has a significant impact on the efficiency and the safety of a flight. Therefore, the study of aeroelasticity problems is a great attention in wing design process. To analyze this, three primary subjects of aeroelastic phenomena that the examination has to focus on, which are wingtip oscillation amplitude, flutter frequency and critical flutter velocity of the wing. [1] As these subjects are highly dependent on structures and materials of the wings, therefore, the aim of this paper is to introduce a structural calculation which is the combination of three experimental models and the infinite element method. Supercritical is chosen as the sample airfoils of the simulation. The model wings are made from different materials and size in order to create varied wing structures, thereby a comprehensive analysis is accomplished and the flutter velocity is also restricted to appropriate values within the working range of experiment devices. Simultaneously, Infinite element method using ANSYS software to simulate the phenomena on the same model wings is also conducted as a verification for the precision of the experimental models. In conclusion, obtained results from the structural calculation have a high applicability in the preliminary design stage of airplane wings, by making comparisons between two or more chosen airfoils to conclude which is the better one in term of wing sustainability and aeroelasticity resistance.

Abstract: Vertical Axis Wind Turbine (VAWT) can perform better than Horizontal Axis Wind Turbine (HAWT) because VAWTs are relatively simple, quiet, and easy to install. It can take wind from any directions, and operate efficiently in urban areas where turbulent wind conditions usually happen. The weakest point for its configuration, however, is its low efficiency so more intensive research is required.Actual VAWT performance can be predicted based on a determination of the forces acting on blades that produce the turbine’s torque. Thus, this paper proposed a new model of force analysis for calculation of VAWT’s performance and a way to enhance the efficiency of VAWT through proper variations of the pitch angles. Additionally, in order to increase the efficiency of the VAWT for a given tip speed ratio, the solidity in term of blade’s number can be adjusted.Results show that right changes in the value of pitch angles and proper selection of the number of blades can considerably increase the efficiency of the turbine and reduce amplitude of turbine’s torque variation. The new model of force analysis can be helpful for aerodynamic analysis of the VAWT turbine for its better design.

Abstract: We are now living in an era of advanced technology, where every part of daily life is related to each other via many kinds of wireless connection. The fourth industrial revolution is now heading toward many kinds of network connecting in real-time which can boost productivity and performance among many manufacturers. In particular, a production manager wanted to know how many automated guided vehicles (AGV) were deployed in a warehouse at that moment; modern farmers wanted to know how many harvesting robots were operating, etc. Therefore, navigating is one of the main elements to handle these tasks. Although we have already applied Global Positioning System (GPS) to the outdoors so far, they still had some limitations, especially on deploying between indoor like houses, buildings which GPS signals are unable to reach. In this paper, we proposed a technique in order to recognize AGV and the distance between them via Received Signal Strength Indicator (RSSI) technique. In addition, we developed a way to store these data on a server for last long usage.

Abstract: In the last several decades past, Helicopters UAVs (Unmanned Aerial Vehicles) have quickly developed and day by day, they play an important role in human life. As it is well-known, helicopters UAV make some outstanding characteristics such as light weight, flexibility and particularly automatically controlled. By applying these characteristics, we research and manufacture Helicopter UAV using for spraying pesticide in agriculture. One of the most important components is main rotor because main rotor generated thrust, drag and momentum. Helicopters UAV efficient changed depending on main rotor. The research works focus on aerodynamics characterization of main rotor in helicopter UAV. This work uses CFD tool in ANSYS CFX software to calculate the aerodynamics parameters generated by main rotor using in UAV. The aim is to characterize the aerodynamics characteristics such as thrust, drag, pressure, aerodynamics quality on the different flight modes (hover, vertical and forward flight). Firstly, the simulations are carried out in hover flight mode with different blade pitch angles. The results are compared to experiment date in another research to validate numerical results. Then, the simulations are carried out in vertical flight mode and forward flight mode. The results showed that thrust and drag coefficient creased with increasing blade pitch angle. When blade pitch angle started from 1800, thrust coefficient decreased but drag coefficient increased sharply. The rotor performance was measured by aerodynamics quality and numerical results showed that the best rotor performance was at 900. In the vertical flight mode, the thrust and drag coefficient decreased with increasing vertical velocity but rotor performance increased slightly. The best vertical velocity for vertical flight is around 2 m/s and 3 m/s. Finally, in forward flight mode, the aerodynamics characterizations of rotors depended on azimuthal angular position of blade or time. Our helicopter operates in environment with light gust. The results showed the change of aerodynamics coefficient to time. Both thrust and drag coefficient changed but the rotor performance did not change much.

Abstract: This paper aims to estimate the effect of turbulent inlet flow to vortices on Delta wing with four different turbulence intensity from 0.5% to 15% and the effect of taper ratios to aerodynamic characteristics of Delta wings with four taper ratios: 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7. The main purpose of this paper is to find out the formation, development, and breakdown of vortices on Delta wings when changing taper ratios and turbulence intensity thence determining the center of vortices with the range of attack angles from 5o to 40o in low velocities about 2.5 m/s. This research uses Delta wing models with a 40o swept-back leading edge, the root chord length 150 mm, and a thickness 5 mm. The problem is simulated by using ANSYS fluent and experiment in the subsonic wind tunnel to compare and validate results. The Delta wing models are meshed by using ICEM to improve the mesh quality and using the turbulence model for low Reynolds number flows Transition SST (4 equations) to calculate aerodynamic characteristics such as lift coefficient, drag coefficient, pressure coefficient... find the paths which connect centers of the vortices, and show the contours of pressures and velocities to evaluate the change of centers of the vortices. The results showed that the two vortices grow up and tend to move inward when the attack angle increase, the vortices are broken strongly in high attack angles, the aerodynamic quality of Delta wings change insignificantly when changing turbulent intensity at inlet. This research also carried out that the stall angle increase when increasing the taper ratio.

Abstract: At present, we are aiming to improve the localization rate and cost reduction in Vietnam, the bus manufacturing units have made their own chassis on the basis of appropriate selection. Passenger bus body frame design is an important process to ensure the suitability and quality of the product before the manufacturing. According to the governmental regulations, the vehicle manufacturing sector in Vietnam must comply with a design approval process and type approval test. Designs must be approved by the competent authority prior to the commencement of manufacturing. There are some applicable regulations in Vietnam such as the standard QCVN 09:2015/BGTVT and QCVN 10:2015/BGTVT on the standards for passenger buses to ensure technical safety and environmental protection. However, there is no specific regulation on the evaluation of bus durability to ensure the passive safety of such vehicles. During the design process, it is possible to calculate the durability accurately that determines the quality of the passenger bus body frame. It could enable automobile manufacturers as well as the competent authorities of design quality approval to control the bus body frame quality, resulting in the improvment of the pruduct, the competitiveness of the product and reducing the production cost. This presentation is the result of structural studies which calculated the deformation of the passenger bus body frame in frontal crash in accordance with the standard ECE R33 and the case of flipping in accordance with the standard ECE R66 for the 46-seat passenger bus, manufactured in Vietnam by Ansys/LS-Dyna software. Accordingly, this evaluation was implemented to assess the quality of the passenger bus body frame in the design process. The result shows that the passenger bus body frame meets the requirement of durability and passive safety in accordance with the calculated standards.

Abstract: The pocketed orifice structure for the air-nozzles of an aerostatic bearing is usually a particular pocketed orifice. This structure can not help the shaft to reach high stiffness in working process, so the applicability of the aerostatic bearing in machines with large centrifugal or horizontal force is not focused. A common pocketed orifice structure for the air-nozzles of the aerostatic bearing to meet the demand of high stiffness of the journal shaft has been developed.. Experimental results show that the stiffness of the aerostatic bearing increases, the eccentricity is only about 0.03 mm at a pressure of 2 to 2.5 bar compared to the structure of particular pocketed orifice. Besides operating at high pressure, a common pocketed orifice structure does not suffer from air congestion (blockage) as in a particular pocketed orifice structure. This results in reducing vibration and avoiding damage inside the aerostatic bearing.