Applied Mechanics and Materials Vols. 284-287

Abstract: The combustion of hydrocarbon fuels produces large amounts of carbon dioxide. In order to cope with the challenge of greenhouse effect and global environmental protection. H2, as a cleaner and more energy-burning fuel, is being considered in many of the practical applications of combustion equipments. However, H2 fuel combustion will still produce pollutant NOx. Thus, the study of NOx emission is one of the most important topics in H2 combustion. With the classical counterflow burner, a numerical simulation of NO emission was carried out on the H2 diffusion flames. The stretch effects on flame temperature, NO concentration, and EINO are analyzed; the contribution of different NO generation routs are also quantified and analyzed. The major parameters influencing NO emission are flame temperature, radical concentration, and residence time, the observed relationship between stretch rate and NO emission is explained with the three major parameters.

Abstract: This investigation studies the speed design of lift-up mechanism in a welfare vehicle that lowers and raises a seat from the side door of the vehicle. The seat functions like a wheelchair as it is landed to the ground. A parallelogram configuration is adopted in the mechanism design. A parallelogram linkage, in which a link rod is shaped as a cam, governs the motion of the mechanism. The cam pair mechanism, like a motion-generator cam, determines the motion to expand the lift-up mechanism. The system is kinematically analyzed. The constraint relations, velocity equations, and acceleration equations of the mechanism are obtained. The kinematic characteristics of the lift-up mechanism are investigated, which gives the guidance to design the speed of the system. The speed of the lift-up mechanism is investigated, in which the method of linear function with parabolic blends for a path with via-points is adopted in the trajectory planning.

Abstract: According to the documents, an ancient Chinese carpenter named Lu Ban invented a four-legged wooden horse carriage in the Chou Dynasty in ancient China, around 480 B.C. This wooden horse carriage could simulate the walking gait of a horse very well but it needed a carriage to keep balance while walking. This paper proposes a method of stability analysis model for the locomotion of a quadruped wooden horse without the support of a carriage. First of all, four most unstable conditions are constructed based on the gait theory of the quadruped wooden horse. The stability areas are obtained by taking the intersections of supporting boundaries that are constructed under various unstable conditions for walking on even and uneven terrain. These results of the stability analysis model are useful for supervising the stability of locomotion of a quadruped.

Abstract: Turbine blades used in large-scale, horizontal-axis wind turbines are usually made from composite materials to reduce the weight while attaining a reasonable strength to weight ratio. The design of large wind turbine blades must consider both their aerodynamic efficiency and structural robustness. This paper presents an optimum design scheme for composite wind turbine blades. The first optimization phase produces the aerodynamic outer shape of a blade framed by airfoils with optimum cord lengths and twist angles along the blade spanwise direction. The second phase provides optimal material distribution for the composite blade. Loadings on the blade are simulated using wind field and wind turbine dynamics codes. The maximum loads on the turbine blade are then extracted and applied to a parameterized finite element model. A design example of a 3 MW wind turbine blade considering one critical load case with a mean wind speed of 25 m/s is demonstrated. The optimization result shows that although the initial blade model is an infeasible design, the optimization process eventually converges to a feasible solution with an optimized mass of 8750.2 kg.

Abstract: Rigid body displacements have different form existing in shell element trial function, and there is a different opinion about its influence. It is borne out by adding rigid body displacements in isoperimetric shell element and solving numerical examples with several methods, that rigid displacement is so important for the convergence of shell element that shouldn’t be neglected.

Abstract: This study was carried out to analyze the dynamic characteristics of the seed plate which is the main part of the vacuum precision planter. The vacuum precision planter is a working machine which is attached to a tractor. The vacuum pump is operated by PTO-shaft which rotates in three types; 540 rpm (9 Hz), 750 rpm(12.5 Hz) and 1,000 rpm(16 Hz). Seeds are sucked into the holes of the seed plate by vacuum, and then they are transported by rotation. At that time, the mode shape of seed plate is important because dynamic characteristics of the seed plate decide seeding rates. If the natural frequency of seed plate corresponds with the frequency of PTO-shaft, the resonance occurs. For this reason, modal analysis of the seed plate was made with FlexPDE(PDE solutions, inc) and ANSYS(ANSYS, inc). Mode shape was observed for 5th mode. First, modal analysis of the seed plate was performed by FlexPDE. According to the result of FlexPDE, natural frequency of each mode was obtained 35.7 Hz, 35.8 Hz, 45.3 Hz, 60.8 Hz and 61.0 Hz respectively. The other modal analysis of the seed plate was performed by ANSYS. As a result of the ANSYS analysis, natural frequency of each mode was obtained 35.6 Hz, 36.0 Hz, 45.6 Hz, 60.9 Hz and 61.1 Hz respectively. The results of the FlexPDE and ANSYS were similar. Natural frequency of the seed plate was confirmed by the above results. So, it was confirmed that the resonance didn't happen by comparing the frequency of PTO-shaft and natural frequency of seed plate. In conclusion, the vacuum precision planter is expected to efficiently sow.

Abstract: The purpose of this paper is to present a design approach based on the geometric constraints of joints for synthesizing differential mechanisms with two degrees-of-freedom, including some mechanisms with the same functions but distinct structures. The concept of virtual axes is presented. And, there are five steps in the design process. Step 1 is to decide fundamental entities by the properties of existing mechanisms and the technique of number synthesis, and 10 suitable fundamental entities of differential mechanisms are available. Step 2 is to compose geometric constraints, and 14 items are obtained. Step 3 is to compose links, and 15 items are derived. Step 4 is to assign fixed constraints for inputs or outputs, and 15 results are found. The final step is to particularize the obtained events by the properties of existing mechanisms and the structures of fundamental entities. As a result, 8 feasible results for differential mechanisms with two degrees-of-freedom and two basic loops are obtained in which 2 are existing designs and the other 6 are novel.

Abstract: Motorcycle is invented so far more than 100 years. Because of having the advantages of light weight, cheap and fast-moving, motorcycle becomes the most popular traffic vehicle. Traditionally, the power systems of motorcycles are internal combustion engines. Recently, due to the reason of energy-saving, and carbon reduction, the engine in motorcycle is substituted by electric motor. Hence, due to the reason of pollution-free, electric motorcycle become more and more popular in city traffic. Planetary gear trains can be used as the transmission systems for electric motorcycles. The purpose of this work is to do the kinematic design of three-speed planetary gear type automatic transmissions for electric motorcycles. First, according to the train value equation of planetary gear train, The reduction ratio equations of planetary gear type automatic transmissions can be derived. Then , based on these reduction ratio equations, the kinematic design of three-speed planetary gear type automatic transmission is accomplished. Based on the proposed methodology, all three-speed planetary gear type automatic transmissions can be synthesized.

Abstract: A design method of the novel adjustable mechanisms is presented for exact multi-path generation. A novel adjustable mechanism with minimal structure error corresponding to required exact paths and with a rotational input link and a linear input link is proposed also. The derivations of instantaneous displacement of the linear input link corresponding to angular displacement of the rotational input link are proposed as well. The required exact paths can be generated by varying the instantaneous displacement of linear input link while rotational input link rotates with a constant angular speed in a cycle. The design procedure of this proposed method is presented either. The examples are provided to verify the feasibility and effectiveness of this proposed method.

Abstract: The presented paper compares results of measured temperature fields achieved by digital holographic interferometry (DHI) and hot wire anemometry. It shows the possibility of using holographic interferometry for the visualization of temperature fields in periodically moving fluids. The measurement of temperature fields in moving fluids has many inherent difficulties. The usage of point temperature measurement methods, such as Constant Current Anemometry (CCA), is limited to frequencies up to 3000 Hz. This frequency should be the limiting factor for using CCA in fluids when a rapid change of temperature occurs. This shortcoming of CCA measurements could be overcome through the use of optical methods such as digital holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain parameters sufficient for the studied case. This setup is not as light-efficient as the Mach-Zehnder type but has double sensitivity. The special technique of acquiring and phase averaging the results from holographic interferometry is presented. The paper also shows the first results of an evaluated 3D temperature field.