Impact of parametric variation on combustion characteristics of hydrogen-fueled strut based scramjet combustor at supersonic speed

Supersonic combustion ramjet engine is more fascinating among all the air-breathing engines. Due to its higher thrust to weight ratio, researchers are more interested to get the superior combustion performance at the optimum boundary conditions. The flow field characteristics and combustion performance have been analysed with the help of Ansys 14.0 software. Generic scramjet combustor of German Aerospace Center (DLR) has been taken into consideration for comparison purpose and off design analysis has been conducted to investigate and analyse the changes. Two dimensional compressible Reynolds Averaged Navier-Stokes (RANS) turbulence model has been opted with the finite-rate/eddy-dissipation reaction model. K-ε two equation turbulence model has been selected to reach up to reasonable accuracy. Validation of the present work has been done with the help of both non-reacting and reacting type data from open literature. To choose the appropriate meshing of the computational model three different types of mesh elements, that is, coarse, medium and fine has been analysed and also grid independence analysis is performed. The present article objective is to get optimum boundary condition by changing the incoming air temperature and pressure at constant Mach number to connect the bridge between incoming air temperature and pressure to the change in velocity throughout the combustion chamber. The detailed understanding and explanation have been done by varying the temperature range of incoming air because of its major impact on combustion performance. Nonetheless, a small variation of air pressure will also discuss to observe the parameters which majorly influence while doing performance analysis. At the end the Optimum boundary condition for the present computation work is observed to be at 833 K temperature with 115 299 Pa pressure.     

Modeling and simulation studies on single/double-effect absorption cycle using water-multicomponent salt (MCS) mixture

This communication presents an investigation on modeling and simulation studies of single/double-effect absorption cooling systems using a water-multicomponent salt mixture vis-à-vis water---LiCl---CaCl₂---Zn(NO₃)₂ solution as a working fluid. The computer modeling/simulation is based on mass, material, and heat balance equations for each component of the system. Effects of different input variables used for the computer modeling and simulation studies are investigated and a detailed parametric study of the double-effect cycle is carried out. A comparative study of the water-multicomponent salt (MCS) mixture and the conventional water---LiBr mixture is also presented for both single-stage and double-effect absorption cycles. It is found that the cooling COP of the double-effect cycle is nearly twice that of the single-stage cycle for both of the working fluids under the same operating conditions. The COP is higher for the water-multicomponent salt (MCS) mixture than for the water---LiBr case. The system feasibility and constraints are also discussed.     

Nonsimilar mixed convection flow of a non-Newtonian fluid past a vertical wedge

Summary The flow and heat transfer characteristics of a second-order fluid over a vertical wedge with buoyancy forces have been analysed. The coupled nonlinear partial differential equations governing the nonsimilar mixed convection flow have been solved numerically using Keller box method. The effects of the buoyancy parameter, viscoelastic parameter, mass transfer parameter, pressure gradient parameter, Prandtl number and viscous dissipation parameter on the skin friction and heat transfer have been examined in detail. Particular cases of the present results match exactly with those available in the literature.     

Structure and ionic conduction in the Ag2O·WO3·TeO2 glass system

Preparation, characterization by X-ray diffraction, differential scanning calorimetry, X-ray photoelectron spectroscopy (XPS), Raman and Fourier transform–infrared (FT–IR) spectroscopy and electrical conductivity studies have been carried out on the yAg2O · (1–y) [xWO3·(1–x) TeO2] glass system. The compositional variation of the glass transition temperature and the calculated oxygen packing density values have been correlated. The conductivity at ambient temperature shows two maxima for the compositions corresponding to y = 0.30 and 0.40 at x = 0.2 and 0.4, respectively. The observed conductivity enhancement is about an order of magnitude and it is correlated to the structural modifications due to the WO3 incorporation into the TeO2 glass network. From the XPS spectra, the binding energies (BEs) of the Ag 3d, Te 3d, W 4f and O 1s core-levels have been determined. The O 1s spectrum is found to consist of two peaks due to the presence of Te–eqOax–Te, W–O–W, W–O, Te = O, Te–O–1 and W–O–1 oxygen species. The tungsten ions appear to exist in 5+ and 6+ oxidation states in these glasses. The proportion of the reduced tungsten ion is found to decrease with an increase in the WO3 concentration, while that of the Te–eqOax–Te species decreases as x increases. The FT–IR and Raman spectra of these samples reveal that the glass network consists of TeO4, TeO3, WO4 and WO6 polyhedra.     

Unsteady free convection flow over a continuous moving vertical surface

Summary The problem of heat transfer in the unsteady free convection flow over a continuous moving vertical sheet in an ambient fluid has been investigated. Both constant surface temperature and constant surface heat flux conditions have been considered. The nonlinear coupled partial differential equations governing the flow have been solved numerically using the Keller box method and the Nakamura method which both give closely similar solutions. The results indicate that the cooling rate of the sheet can be enhanced by increasing the buoancy parameter or the velocity of the sheet. It is found that a better cooling performance could be achieved by using a liquid as a cooling medium rather than a gas. The overshoot in the velocity occurs near the surface when the buoyancy parameter exceeds a certain critical value.     

Electro-Discharge Machining of Inconel 825 Super alloy: Effects of Tool Material and Dielectric Flushing

Aspects of machinability of Inconel 825 super alloy during electro-discharge machining was attempted in this work. The extent of machinability was investigated in purview of process performance (i.e. material removal rate), surface integrity (morphology as well as topography) of the EDMed work surface including surface roughness, surface crack density, white layer thickness, and micro-indentation hardness. Effects of variation of tool material (graphite, tungsten, brass and copper) were analyzed in this work. Metallurgical characteristics of the EDMed work surface were studied in view of phase information (matrix and precipitates), grain refinement (crystallite size, micro-strain and dislocation density) etc. Results were further interpreted in support of EDS, and micro-hardness test data. Additionally, effects of flushing condition (with and without flushing) of the dielectric medium were examined on influencing EDM performance on Inconel 825 work material. Moreover, effects of peak discharge current on EDM responses were discussed.

     

High-temperature deformation behavior of Ti-TiB<Subscript>w</Subscript> in-situ metal-matrix composites

In developing titanium-based materials for high-performance structural applications, the focus has been on discontinuously reinforced titanium-matrix composites that are based on the in-situ creation of TiB whiskers. This article presents the elevated-temperature compressive flow properties of Ti-TiB_w composites as a function of temperature (from 973 K to 1,273 K), strain rate (from 10⁻⁵ to 10⁻³s⁻¹), and the TiB whisker content (commercially pure titanium and composites with 30 to 86 vol.% TiB_w). In both the commercially pure titanium and the TiB-whisker-containing titanium composites, flow stress increases with increasing strain rate and decreasing test temperature. In this study, flow stress increased with increasing volume fraction of TiB at a given temperature and strain rate. The composite containing 86% TiB_w showed significantly higher elevated-temperature strength when compared to the other composites. The composites exhibit systematic trends in the variation of work-hardening behavior (in terms of work-hardening exponent, n, and work-hardening rate, dσ/dɛ) and the strain-rate dependence. For more information, contact N. Eswara Prasad, Defence Metallurgical Research Laboratory, P.O. Kanchanbagh, Hyderabad 500058, India; e-mail nep@dmrl.ernet.in or neswarap@rediffmail.com.     

Epilepsy analysis using open source EDF tools for information science and data analytics

Electroencephalogram (EEG) is the signals that measure the electrical variances of brain using metal electrodes. We observe the EEG signals by using European Data Format (EDF) BROWSER and EEG STUDIO. By using EDF BROWSER, we can get the mean and frequency from the filtered output signal using band‐pass filter. Using EDF BROWSER, we can also perform Root Mean Square (RMS) and signal samples. Using EEG STUDIO, we can analyze the average frequency and standard deviation. Epileptic seizure prediction and detection are done by spike detection, frequency domain analysis, and nonlinear methods. EEG signal contains different artifacts like electrooculography (EOG), EKG, and electrocardiogram (ECG). ECG signals are produced by heart. EOG signals are produced by eyes. EMG signals are produced by muscle coordination.     

Performance Evaluation of Symmetric 8 × 10 Gbps TWDM-PON Incorporating Polarization Division Multiplexed Modulation Techniques Under Fiber-Impairments

Today’s access networks are in high demand to fulfill the high bandwidth requirement because of extensive improvement in high transmission rate applications for cloud computing, big data analytics, and other next-generation 5G smart applications. This exponential growth of high capacity and broadband access technologies comprise an essential trend in the development of a passive optical network (PON) access network. In this paper, 80/80 Gbps time wavelength division multiplexing PON (TWDM-PON) incorporating polarization division multiplexing (PDM) based Mach–Zehnder modulator (MZM) and electroabsorption modulator (EAM) techniques have been proposed. The performance of the system consisting of different polarized multiplexed modulation techniques is investigated in both downstream and upstream data transmission for variable transmission distance and received optical power in terms of bit error rate (BER), eye diagrams, power budget (PB) and receiver sensitivity. The results show that the 4?×?20/20 Gbps PDM-EAM modulated signals over 100 km fiber distance at ??60 dBm RS and 70 dB PB are successfully transmitted under fiber non-linearities. The proposed TWDM-PON system provides a next-generation long-reach access network from urban to rural areas.