摘要: This study proposes a biomass power and heat cogeneration system that comprised of a gasifier, Stirling engine/alternator, and absorption cooler. Gasification is the most versatile approach to utilize biomass for the flexibility and affectivity of this technology. The flue gas from the combustion of the gasified gas propels a free-piston Stirling engine/alternator, which produces 50 or 60 Hz alternating current as output. The absorption cooler absorbs the residual heat from the flue gas after Stirling engine’s hot end and produces low temperature energy. This cold energy could be used to satisfy air conditioning requirement or be directed to the cold end of Stirling engine to further increase the power efficiency of the Stirling engine. The solid biomass rice husks were tested in this study, in addition, the current power and heat cogeneration system’s gross output exceeded the rated 500w engine gross output for this tested feeds. The total efficiency of this system was approaching to 46%.
摘要: Based on the propeller momentum theory, this paper obtained the momentum model for internal flow of lift fan system for analyzing power characteristics in transition of lift-fan VTOL. This paper mainly focused on total lift, total drag and total power during the whole transition with the increase of freestream velocity. The analysis results show the particular characteristics of total drag and total power in transition, which can be used for selecting parameters at the preliminary phase of designing lift-fan VTOL.
摘要: Based on the propeller momentum theory, this paper obtained the momentum model for internal flow of lift fan system. It analyzed the influence of its conceptual parameters on power characteristics of lift-fan VTOL to analyze the trend changes of the total power required with the increase of freestream velocity. The results can be used for selecting parameters at the preliminary phase of designing lift-fan VTOL and determining the design parameters of lift-fan VTOL.
摘要: It is presented to solve the hunting limit cycles of railway system with multiple degrees of freedom and strongly nonlinear factors by describing function method(DFM). A nonlinear railway vehicle model with several dry friction factors is developed, and the 16 nonlinear transcendental equations of it are deduced using DFM. The modal characteristics of the hunting limit cycle for the vehicle model are obtained by the software programmed to solve complicated equation set. To verify the accuracy of describing function method, the hunting limit cycles of the model are simulated in time domain, and the results from these two methods have good consistence. This shows that the limit cycles of nonlinear rail vehicle systems with strongly nonlinear factors can be solved with high accuracy and efficiency by DFM, which of value in practical engineering application.
摘要: With the widespread use of the water lubricated rubber stern bearing, researches around rubber bearings are becoming hot points in recent years and researches on dynamic characteristic are particularly important. The dynamic characteristics of vibration system depend mainly on its modality parameters. This paper presented experimental modal analysis of water-lubricated rubber stern bearing by hammering method, and by comparing the differences with the finite element simulating result, analyzed the rubber bearing based on linear modal analysis theory. Due to the nonlinearity of rubber material, although the natural frequency range of rubber layer could be gotten, it’s hard to get the precise modal shapes of it, yet the metal layer could get more precise results.
摘要: Composite coatings were prepared using electroless nickel bath containing different concentrations of Al2O3 nano-particles. The analyses of coating compositions, carried out by EDS, showed that there is marginal difference between phosphorus contents of NiP and NiP/nano-Al2O3 deposits. The structure of the coatings was examined by scanning electron microscopy (SEM), and X-ray diffraction (XRD). It has been found that the co-deposition of nano-Al2O3 particles with Ni disturbs the NiP coating’s regular surface structure and increases its surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 3.5wt.% solution of NaCl in order to evaluate their corrosion resistance. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests both showed that, the corrosion resistance of NiP-Al2O3 coatings firstly increases and then decreases when Al2O3 concentration in electroless bath is increasing, but the corrosion resistance of NiP-Al2O3 composite coating is better than that of amorphous NiP coating.
摘要: This paper presents the design and simulation on investment casting mold for metal matrix composite material. The study was investigating the design parameters for the casting mold and simulated the temperature and pressure on the mold. Compressor impeller selected as the product of the study. Among the various types of casting techniques, investment casting process is the most suitable process to produce the compressor impeller. The alternative design of casting mold of investment casting was generated using CAD software. Concept scoring was prepared to select the suitable design for the investment casting process. Material selection of compressor is Aluminum Silicon Carbide. Stainless steel AISI H13 is selected as the material for the mold. The parameter for the mold design is included branch, gating, sprue and runner. The analysis was presented to the mold by using ANSYS simulation tool to determine the temperature and pressure of the mold. In addition, three case studies were presented and compared the static pressure in different velocity and temperature of the mold design. The result showed the runner and the branch size were important to produce the molten metal flow into the mold pattern. As a result, the design of investment casting mold was proposed.
摘要: Based on the basic theory of molecular recognition, we designed an organic molecules model that spontaneously form three-dimensional fibrillar scaffolds to induce the crystallization of hydroxyapatite to synthesized enamel-like calcium phosphate/hydroxyapatite under a controllable way in vitro. Cross-linking of collagen on the dentin surface and silk fibroin with N,N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was optimized by varying the NHS/EDC molar ratio at constant EDC concentration. CaCl2 and Na3PO4-12H2O solution was added with Ca: P odd as 1.67:1 after conjugated. The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there were column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. The results suggest that silk protein monolayer may be useful in the modulation of mineral behavior during in situ dental tissue engineering.
摘要: In this paper, the theory of DR (Delayed Resonator) is employed to investigate the vibration of vehicles, for the first time, and the process to suppress the vibration transmission from the engine to the body using the DR is explored. A simplified half-car model with DR is built for the case of idling, and the critical time delay is obtained by analyzing the stability of the model, additionally, the different effect of the parameters on the stable region is investigated. Method of solving the optimum values of the gain and the delay for maximum vibration suppression is built, afterwards numerical emulation is carried out to check the effect and to compare with the hydraulic engine mount. The results show that the amplitude of the body can be reduced more effectively.
摘要: Based on the assumption of ideal fluid, this paper both employed modes method and pressure variational principle to transfer free boundary value problem describing liquid nonlinear sloshing into infinite dimensional modal system integrated by Runge-Kutta method. The results shows that nonlinear characteristics of liquid sloshing in rectangular tank.