Anupam Purwar

Thermo-Structural Design of Strut Based Flame Holder for Scramjet Combustor

Flame holders are critical for efficient combustion in scramjet engines. There are various flame holder concepts, among them strut is one of the most prominent ones. Strut based flame holders decelerate the supersonic flow, providing more time for fuel air mixing and combustion. Although, this exposes the strut to very high as well as spatially varying pressure and heat flux giving rise to high temperature and stress across its structure. Thus, its structural design becomes highly challenging and its thermo-structural behaviour needs to be investigated for a robust design. In this work, spatially varying pressure and heat flux have been estimated using computational fluid dynamics analysis, which are used as boundary conditions for subsequent thermo-structural analysis. Based on thermo-structural behavior of strut, a multi-layer material system consisting of ZrB2-SiC and phenolic cork has been proposed to mitigate high temperature and stress. This novel multi-layer material system, effectively reduces the temperature and stress experienced by the strut’s metallic interior to 910 K and 102 MPa respectively.

Design of Thermal Barrier Coating System for Scramjet using Coupled Thermo-Structural Analysis

ABSTRACT Thermal barrier coating (TBC) is essential for scramjet structure to protect the metallic structure from melting or developing high stress. In this perspective, a novel TBC system with multiple layers of ceramics: top layer, intermediate layer, bond coat over a suitable metal substrate has been proposed. First, material selection for TBC system has been carried out based on their thermal conductivity and maximum operational temperature. Then, an elaborate design methodology has been evolved to constrain the temperature of each layer within their operational limit and minimization of thermal mismatch. Different design parameters have been identified and iterative finite element based thermo-structural analyses have been carried out to optimize them and hence, limit metal substrate temperature within 1250 K and the maximum interfacial shear stress within 80 MPa, when exposed to heat flux as high as 1.5 MW/m2 and pressure greater than 1.3 bars. GRAPHICAL ABSTRACT

Human detection based on explicit skin colour space thresholding and minor motion detection

In this paper, a novel approach for human presence detection from digital image is presented. This approach is based on combined clue from skin colour and minor motion detection. For skin colour detection, explicit thresholding of CbCr colour channels is used and for minor motion detection morphological differences of multiple consecutive images has been used. MATLAB® is used for processing. Relatively small part of exposed human body in the frame of an image is sufficient for detection. The approach is computationally efficient, potentially real time and robust. The combined technique gives improved performance compared to each individual technique. Location of the object (human) within the frame is also simultaneously identified.

A Methodology for Coupled Thermal-Structural Analysis and Structural Design of Scramjet Combustor

Scramjets are essential for thrust generation in hypersonic air breathing cruise vehicles. One of the critical challenges in developing scramjet is their complex structural design due to intense thermal-structural loads experienced during hypersonic flight. Finite element based coupled thermal-structural analysis has been carried out to calculate temperature and strain field for designing a semi-monocoque scramjet structure. Multiple iterations of thermal-structural analysis have been carried out to estimate design parameters namely wall thickness, coating thickness, spacing and cross section of stiffeners to contain temperature, deformation and stress as well as minimize weight. It has been found that skin thickness of 1mm, coating thickness of 500µm, stiffener spacing of 3mm is most optimum for a scramjet flying at speed of Mach 7 at 30 km altitude with isolator air entry speed of Mach 2.2.

Thermal Analysis of Scramjet Combustor Panel with Active Cooling Using Cellular Materials

Long endurance hypersonic air-breathing vehicles experience very high temperatures owing to the generation of shock waves and viscous dissipation. Extreme heat flux is experienced by the scramjet combustor due to exothermic combustion and requires mechanisms for passive and/or active heat dissipation in order to sustain the flight duration. Regenerative active cooling of the scramjet combustor using endothermic hydrocarbon fuel is being widely pursued around the globe as a key approach to this end. Moreover, with the emerging multifunctional cellular materials, it is possible to design the structure which acts as a load bearing member as well as aid in cooling the airframe, with the additional advantage of reduced mass. With this perspective, a one-dimensional analytical heat transfer model has been developed to study the cooling performance of an actively cooled representative scramjet combustor panel using cellular materials. Hot-gas wall temperature of ~1465K is estimated for a flight condition of Mach 7 with active cooling for a coolant mass flow rate of 0.0195 kg/s. Additionally, parametric studies involving mass flow rate, channel dimensions and flight Mach number have also been studied.

GPS signal jamming and anti-jamming strategy — A theoretical analysis

The weak strength of GPS signal makes it very vulnerable to jamming. This calls for appropriate modeling and implementation of GPS signal source and jammers that are used to jam GPS signal. The present work describes a simple and efficient way to simulate GPS signal using MATLAB® with focus on investigation of GPS signal jamming and devising an anti-jamming technique to counter different jamming scenarios besides Additive white Gaussian noise (AWGN). The jamming types influencing GPS Signal have been identified and suitable jamming scenarios have been modeled using MATLAB®. The effect of each jamming signal type on GPS signal has been quantified by estimation of Bit error rate (BER) for different jamming to signal (J/S) ratio. A background study of different anti-jamming techniques for GPS signal has been carried out and Turbo coding has been implemented as a suitable measure to counter the effect of GPS signal jamming.

Smart control of electric lamp using artificial intelligence based controller

There is need and scope of controlling the power consumed by conventional electric lamps in presence of some natural light. An artificial intelligence based control system has been developed to control a lamp dimmer circuit with bidirectional triode thyristor. The light present in the room is sensed and voltage supplied to the lamp is controlled by varying the time constant of the circuit through change of resistance of a multi-turn potentiometer with a stepper motor. The resistance set in the lamp dimmer circuit is in accordance with signals from an adaptive Neural Network running in MATLAB®. The artificial neural network (ANN) runs in real time in MATLAB® environment to control the time constant of the lamp dimmer circuit for controlling of power consumption. Under test conditions, energy savings up to 35% is achieved.