Study of the transient release of water vapor from a fuel bed of wet biomass in a reciprocating-grate furnace

The present study investigates how sudden changes in fuel moisture affected the combustion characteristics of the fuel bed in a 4-MW reciprocating-grate furnace. The moisture content of the fuel fed to the furnace was monitored online using a near-infrared spectroscopy device, and the water vapor concentration in the flue gas was measured continuously. To obtain experimental data on fuel-bed conditions, the temperature and gas composition in the bed were measured using a probe. A simplified drying model was developed using the measured gas composition values as inputs. The model was then used to estimate the drying rate and to simulate the extent of the drying zone along the grate. Measurements indicated that a change in the moisture content of the fuel fed to the furnace was detected as a change in water vapor concentration in the flue gas with a delay of about 2 h. The model predicted that a portion of wet fuel would need about 2 h to become dry, in line with the measured time delay of the water vapor concentration change in the flue gas. Overall, there was good alignment between the measured and simulated results, supporting the validity of the model and the assumed mechanisms.     

An efficient meshless method based on a new shape function

Although, the finite element method numerically is efficient it exhibits difficulties whenever the remeshing of the analysis domain must be performed. For such problems, utilizing meshless computation methods is very promising. But, their large computational cost, which arises from following a time‐consuming process to find shape functions, is one of the most important factors limiting the use of these methods. In this paper, we introduce a direct approach, based on properties required for any shape function, to prepare the shape function and propose a new meshless method. The proposed method does not need any predetermined basis or weighting functions and can be performed faster and more efficiently. Another advantage of the introduced method is its capability to apply desirable changes to the shape function. Application of the proposed approach for electrostatic field computation and verification of the obtained results using theoretically known solution is also presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Singular Value Decomposition Combined With Analytical Method for Tokamak Plasma Tomography

Several arrays of soft X-ray detectors are used with the Fourier expansion for angular direction and Zernicke polynomial on radial direction during an analytical method tomography. A truncation of two expansions is necessary. We used singular value decomposition in order to solve the set of equations. This technique reconstructs better images of tomography.     

Comparison Study of Fourier and SVD Method for Plasma Mode Analysis in Tokamaks

Fourier analysis and Singular Value Decomposition (SVD) are two familiar methods for mode detection in tokamaks. In this article this two methods, fourier and SVD, have compared. The results show fourier analysis in m ≥ 3 and when the energy is balanced between modes could not recognize the correct mode number. The SVD analysis is cited method for all modes.     

Interim fatigue design recommendations for fillet welded joints under complex loading

Current fatigue design methods for assessing welded steel structures under complex combined or multiaxial loading are known to be potentially unsafe. This has led to a number of research projects over the past 10 years. Some progress has been made in developing better methods, but they are not yet suitable for general design. This paper presents an interim solution based on a review and analysis of relevant published data; all referring to fatigue failure from a fillet weld toe. These indicate that Eurocode 3/IIW S – N curve FAT80/3 (negative inverse slope of 3) is suitable for combined normal and shear stresses acting in phase, and possibly for out-of-phase (i.e. non-proportional loading) bending and shear if the shear stress is not due to torsion. However, a shallower curve FAT80/5 is necessary for out-of-phase torsion and bending or tension. Both curves are used in conjunction with the nominal maximum principal stress range occurring during the loading cycle.     

Effect of combined velocity and pressure on life time of carbonbrushes

The value of contact resistance between copper sliprings and carbon brushes, in wound-rotor induction motors, has a profound effect on the performance of these machines. The increase of this resistance due to bad contact may be detrimental. In this paper, an important factor affecting the resistance is introduced. This is the PV factor (product of contact pressure and peripheral speed). It represents the frictional power density at the interface; and it is also an indication of the volumetric or linear wear rate. A relation between the operational life time of brushes and the PV factor is experimentally deduced     

A Comparison Between ECAP and Conventional Extrusion for Consolidation of Aluminum Metal Matrix Composite

In this study, two powder consolidation techniques, equal channel angular pressing (ECAP) and extrusion, were utilized to consolidate attritioned aluminum powder and Al-5?vol.% nano-Al₂O₃ composite powder. The effect of ECAP and extrusion on consolidation behavior of composite powder and mechanical properties of subsequent compacts are presented. It is found that three passes of ECAP in tube at 200?°C is capable of consolidating the composite to 99.29% of its theoretical density whereas after hot extrusion of the composite the density reached to 98.5% of its theoretical density. Moreover, extrusion needs higher temperature and pressing load in comparison to the ECAP method. Hardness measurements show 1.7 and 1.2 times higher microhardness for the consolidated composite and pure aluminum after ECAP comparing with the extruded ones, respectively. Microstructural investigations and compression tests demonstrate stronger bonds between the particles after three passes of ECAP than the extrusion. Furthermore, the samples after three passes of ECAP show better wear resistance than the extruded ones.     

Electron Temperature Measurement in IR-T1 Tokamak by ECE Diagnostic

A suitable instrument for electron temperature measurement in Tokamak is electron cyclotron emission diagnostic. We used a heterodyne radiometer in Iran-Tokamak-1 (IR-T1) to measure this parameter. This 5 channel system works in K _α-band and has a very fast response time and good resolution frequency for IR-T1 tokamak. This receiver was used outside the Tokamak, perpendicular to B _t, and with second harmonic of X-mode, variation of electron temperature was measured.