摘要: Use of biodiesel in diesel engine is becoming popular due to its advantages such as eco friendly, green fuel, low cost and most importantly it is a renewable fuel. In the recent scenario of increased diesel fuel cost and environmental issues, the use of biodiesel in internal combustion engines in transport sector provides energy security along with environmental protection. The chemically treated vegetable oil called biodiesel can be produced from either edible or non edible oils through commonly known transesterification process. In this investigation, biodiesel produced from non edible jatropha oil has been used in a single cylinder water cooled stationary diesel engine to assess the performance and emission characteristics of the engine. The performance characteristics of biodiesel are similar to that of diesel fuel operation and emission levels are lower than the diesel fuel. The use of low cost biodiesel in diesel engines leads to same power output with lower emission levels which in turn leads to a global revolution in possessing a renewable fuel at stake and also assures energy security and environmental cleanliness.
摘要: Variation of calcium excess, water content and mixing time have been taken into the parameters of the injection test of calcium phosphate paste synthesized via low temperature hydrothermal method. The result indicated that all the parameters are very prominent to influence the material injectability possible to be fully injected out the syringe. Strict control of paste synthesizing parameters has successfully overcome poor injectability of the material.
摘要: Generally, pile foundation is typically chosen to support heavy structures. However, the developments of expressions to determine the pile capacity is usually based on fully saturated and completely dry conditions. In fact, almost 40 percent of natural soils on the earth surface are in an unsaturated state. Thus, in this paper, an expression for pile capacity in homogeneous unsaturated sand layer is developed. The simulations using developed expression are performed and discussed. Typical results show that the pile capacity and the factor of safety are affected by matric suction. However, the influence of matric suction may be ignored for a long pile.
摘要: This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modeling of elevated pressure methane non-premixed sooting flames. The study focuses on comparing the two soot models available in the code for the prediction of the soot level in the flames. A standard k-ε model and Eddy Dissipation model are utilized for the representation of flow field and combustion of the flame being investigated. For performance comparison study, a single step soot model of Khan and Greeves and two-step soot model proposed by Tesner are tested. The results of calculations are compared with experimental data of methane sooting flame taken from literature. The results of the study show that a combination of the standard k-ε turbulence model and eddy dissipation model is capable of producing reasonable predictions of temperature both in axial and radial profiles; although further downstream of the flame over-predicted temperature is evidence. With regard to soot model performance study, it shows that the two-step model clearly performed far better than the single-step model in predicting the soot level in ethylene flame at both axial and radial profiles. With a modification in the constant α of the soot formation equation, the two-step model was capable of producing prediction of soot level closer to experimental data. In contrast, the single-step soot model produced very poor results, leading to a significant under-prediction of soot levels in both flames. Although the Tesner’s soot model is simpler than the current available models, this model is still capable of providing reasonable agreement with experimental data, allowing its application for the purpose of design and operation of an industrial combustion system.
摘要: In all industries which are related to heat, suitable thermal ranges are defined for each device to operate well. Consideration of these limits requires a thermal control unit beside the main system. The Satellite Thermal Control Unit (STCU) exploits from different methods and facilities individually or mixed. The space radiating fin which is combined with a heat pipe can be used to transfer the excess heat from the satellite to outer free space. The finite volume method is employed to simulate numerically the temperature distribution in a space radiating fin and evaluate thermal fin efficiency. Final results are achieved for two different materials (Aluminum and Beryllium) and compared to each other. The present results are compared with the other analytical methods and good agreement is shown.
摘要: Creep damage is an important failure factor of high-temperature alloy. The fatigue crack growth under elevated temperature of the material is investigated for life prediction. In this paper, the numerical simulation of the crack propagation in nickel-based super alloy, IN718, was presented. A modified creep damage model was employed to accumulate the creep damage under cyclic loading conditions. The numerical results exhibit a reasonable agreement in the comparison with the experimental data. The cohesive zone approach, combining with the extended finite element method, has the ability to simulate the creep-fatigue crack propagation even for more complex loading conditions and specimen geometries.
摘要: This paper investigates nonlinear elasto-plastic analysis of the dynamic response of composite spherical shells base on the isotropic hardening and flow rule theorem. elasto-plastic strain-hardening is expressed at this stage and the plastic strain obtains to combine with elastic strain to present the elasto-plastic constitutive relation of composite spherical shells. Analytical solutions of the governing equations are based on the Chebyshev spectral collocation methods and then compare results with ABAQUS FEM. In numerical example, the effective of different external loads on the nonlinear elastic and nonlinear elasto-plastic of composite spherical shell are discussed in details.
摘要: Nowadays, various environmental regulations are being strengthened because of air pollution caused by exhaust gas emission of the automobiles. Biodiesel has been recognized as an alternative energy resource since it can be used without the modification of existing diesel engines and contains oxygen in itself, so the engine performance didn’t have large differences in comparison with the diesel fuel but remarkably reduces smoke emissions. The main objective of this study is to investigate usability of non-esterified biodiesel as an alternative fuel in a common rail direct injection diesel engine. The non-esterified biodiesel has not generated glycerin in esterificaion process and reduced the 20 percent of cost because it has not used methanol in the production process. Experiments were conducted by using the 5 percentage of biodiesel and 4 percentage of biodiesel with 1 percentage of WDP (water dipole power) in diesel fuel. Based on the experimental analysis the smoke emission of biodiesel was reduced significantly, but power, torque, and brake specific energy consumption was similar in comparison with commercial diesel fuel.
摘要: This study adopted a new formula fishing-boat fuel which is based on the existing fishing-boat-fuel A (FBFA) with the addition of viscous agents (RDS0.5, PFO0.5) in two different proportions. FBFA, RDS0.5 and PFO0.5, respectively are tested in three real-scale fishing boats. During the actual ship trial, the engine operating conditions, engine fuel oil consumption, horse power output and navigation speed were assessed and recorded. Furthermore, fuel emissions were sampled and analyzed, fishing-boat diesel engine performance was assessed and differences in exhaust composition were compared. The results showed that the three new viscous agents fules used lack abnormal vibration and noise, and have similar output status in terms of engine operational performance. At the same boat, the fuel oil consumption rates were similar between the new formula and FBFA. Moreover, analysis of contamination displayed that RDS0.5 particulate matter (PM) content was less than that of FBFA. Consequently, RDS0.5 appears to cause less engine wear. Additionally, the exhaust emission analysis results identified RDS0.5 as the best fuel for the engine. Futhermore, regarding pollutant emissions, including CO, CO2, NOx, PM, PAHs, only CO emissions are slightly higher than for FBFA. However, the CO emission value does not exceed exhaust emission standards of the U.S. Environmental Protection Agency (EPA). It is remains within the allowable value range. RDS0.5 should have practical value.