Abstract: An 8-noded quadratic isoparametric plate bending finite element that incorporates first-order transverse shear deformation and rotary inertia is used to predict the free vibration response of sandwich plate structures. A programme has been developed using MATLAB. The finite element results presented here show good agreement with the available semi-analytical solutions and finite element results. Parametric studies have been conducted by incorporating variation in support conditions, fibre angles of the skins and overall thickness and detail interpretations are provided.
Abstract: The effect of partition on turbulent natural convection has been investigated numerically with different lengths and positions in an air filled square cavity. The top wall of the cavity is assumed to be cold and the other three walls are hot. Two-dimensional governing equations based on Reynolds-averaged Navier-Stokes equations are solved numerically by control volume method in a staggered grid manner. The iterative SIMPLE algorithm is also used to solve the discretized momentum equations to compute the intermediate velocity and pressure fields linked through the momentum equations. The hybrid differencing scheme which is based on a combination of central and upwind schemes is employed to discretize the convective and diffusion terms of the equations respectively. To describe the structure of turbulent flow which is changed due to the increasing importance of viscous effects, wall function was applied to simulate the turbulent flow. The results show that when the partition is placed on the top or bottom wall, the heat transfer rate through the bottom wall increases by increasing the partition length. The number of vortices established in the cavity depends on the partition length. Furthermore, when the partition is mounted on the left or right wall, only a small part of the top wall has a direct interaction with the left wall and the rest of that has an indirect interaction with the bottom wall.
Abstract: Launch and space vehicle structures are required to be extremely weight efficient. The need to achieve the performance required for the engine in the upper stage of a launch vehicle, increase the payload capacity drives rocket engine manufacturers to seek higher thrust level, specific impulse and thrust to weight ratio. The use of high temperature C-C composite materials is an efficient way to reach these objectives by allowing use of high expansion ratio. Nozzle extensions benefiting of the outstanding thermal, mechanical and fatigue resistance of these materials to decrease mass and featuring high temperature margins. A three-directionally reinforced (3D) carbon-carbon (c-c) material nozzle exit cone is selected for the current study. C-C composite exit nozzle must possess excellent stability and strength under extreme conditions for a specified amount of time. Carbon-carbon composites are appropriate materials for applications that require high specific strength at elevated temperatures. The paper describes the thermo structural analysis of a typical c/c nozzle exit cone.
Abstract: The performance of a Plate fin radiator in terms of heat transfer rate and coolant side pressure drop depends significantly on the distribution of coolant through its passages. Uneven flow through the passages i.e. flow maldistribution, can cause local hot spots in the radiator due to high coolant flow in some passages. The flow maldistribution among the passages can be reduced to a large extent by proper optimisation of the header. The present paper investigates the method to optimise the header of a 680 kW radiator to reduce the maldistribution in its passages using Computational Fluid Dynamics (CFD). The analysis was simplified by considering the porous media instead of simulating the exact fin configuration in the radiator. The maximum and absolute values of flow maldistribution factor were considered in this study to determine the effectiveness of the header with respect to flow maldistribution. The flow maldistribution factor was determined based on the individual velocity of coolant in a passage and the average velocity of coolant in all the passages. The methods used for optimisation were rounding the header inlet, tapering the header partially, changing the position of the taper and modifying the end portion of the header. In this paper two parameters, viz., flow maldistribution parameter and absolute maldistribution parameter were considered to measure the maldistribution of a radiator. Due to these optimisations in the header, the maximum and absolute values of maldistribution reduced up to 18% and 45% respectively.
Abstract: Thermo-structural analysis with advanced composite plates and shells has been performed using Finite element method in order to determine temperature response and associated thermal stress. On solving the Fourier’s heat conduction equation, temperature profile is arrived at, with the assumption of linear/uniform temperature distribution through the thickness. Finite element program is developed for steady-state heat transfer problems using Semiloof shell element. Validation for integrated thermo-structural analysis has been done and compared with the available results from literature. The new results thus obtained are presented in terms of temperature, thermal stress, and displacement. The results obtained will be useful particularly in nuclear reactor vessels and Thermal Protection System (TPS) in aeronautical engineering.
Abstract: In this article, nonlinear analysis of the composite plates and shells were carried out using the semiloof shell element. The finite element formulation is based on Green strains and Piola-Kirchhoff stresses. The nonlinear solution procedure was implemented to study the nonlinear behaviour of composite plates and shells. Due to coupling effect in composite plate and shells under in-plane load, pre-buckling displacement is significant and hence the behaviour is nonlinear. A verification study has been carried out to establish the efficiency of the present model. Since the margin of factor of safety is less in aerospace application, the detailed understanding and study of pre-buckling displacement is necessary for the designer.
Abstract: The depleting Fossil fuels reserves are caused to look into new Renewable energy sources to fulfill Diesel fuel demand in developing countries such as India. Increasing urbanization is lead to the search for new alternative sources like biodiesel. In India demand of diesel fuel in Industry and Transportation sector. To resolve all the above problems, researchers, scientists were produced biodiesel from first, second and third generation biodiesel sources. Among all the sources Algae was the most Oil rich sources. The byproducts in algae to biodiesel conversion process are most valuable than other. In the present work author tried to work in a new approach, i.e. the mixed culture algae particles are emulsified in pure Coconut biodiesel fuel by using TritonX-100 as a surfactant to prepare an emulsified fuel. This fuel sample was applied to DI CI engine to improve performance, emission characteristics. The experimental results were shown that there is the improvement in diesel engine performance; emission characteristics especially break thermal efficiency and NOx emission reduction than diesel fuel due to its clean combustion.
Abstract: Rocket motors are used worldwide in both upper and booster stages.Solid rockets can provide high thrust for relatively low cost. Considering the large size of solid motors, these motors are to be designed as segmented motor cases. Segmented motor cases have to be joined by segment joint. Segment joint with tongue and groove configuration provides performance reliability in effective sealing of joints. A tongue-and-groove arrangement employs a pressure-energized metal seal which expands radially when the cylinders are internally pressurized. The radial expansion enhances the sealing effect of the metal seal between the tongue and the groove. Metal end rings welded to the shell motor cases and shear pins for the final assembly provides the sealing. The load sharing among the pins depends on the presence of the slit in a ring, whole & pin dimensional clearances, internal pressure and friction between the metal end rings. Structural analysis of a discontinuous metallic segment ring and shear pins iscarried out in this study. Structural analysis is based on detailed solid model for the segment joint. The load augmentation in the shear pin near the discontinuity is worked out based on a load augmentation factor derived out of FE analysis. The study further extended to a deviation in a nearby hole / pin combination at the vicinity of the discontinuity and is presented in this paper.
Abstract: Large amount of agricultural waste is produced after harvesting of crops like wheat, paddy, soya-bean, maize, mustard, sugarcane, groundnut etc. The conventional way is to burn it in the fields or dump it across the wasteland. The burning of biomass residue in the fields has very adverse effect for the environment and leads to air pollution. A more efficient way is to use biomass residues of agricultural crops for production of electricity through biomass based power plants. In India, grid connected biomass power and co-generation installed capacity has increased from 1,102 MW in 2006 to 8,182 MW in 2017. This paper analyses the twenty years’ performance of a 7.5 MW biomass power plant situated at Rangpur village near Kota city of Rajasthan, India, based on capital cost, present cost of biomass per tonne, data obtained from 2006 to 2015 related to annual power generation, and annual consumption of biomass. Levelized Cost of Electricity is found to be varying from Rs. 4.43/kWh to Rs. 4.64/kWh for interest rates varying from 8% to 16%. Plant Load Factor is found to be varying from 29% to 82% during the period of 2006-07 to 2014-15 for nine years, with an average plant load factor of 73%.
Abstract: The work in this manuscript deals with the numerical simulation of natural convection in a staggered cavity with the help of a recently developed two-dimensional double Multiple-Relaxation-Time (MRT) thermal Lattice Boltzmann method (LBM). In the last decade, there has been a rapid rise in the development of Lattice Boltzmann methods. However, its application in the simulation of natural convection from a staggered cavity has been carried out for the first time in this study. A careful undermining into the existing literature of heat and mass transfer reveal that study of natural convections in cross-sectional cavities is notably absent. Therefore, in this manuscript, we attempt to review the recently developed method and tried to analyze its implementation on natural convection in a staggered cavity with four differentially heated vertical walls. The problem geometry has eight boundaries. It is a staggered cavity with adiabatic horizontal walls and differentially heated vertical walls. The flow inside the thermally driven staggered cavity has been carefully studied for Rayleigh numbers 103, 104 and 105. The velocity and pressure boundary conditions are determined by a non-equilibrium extrapolation rule. As no benchmark results are available in the literature for this relatively new problem, we carry out its simulation with the help of a yet another well established scheme. This scheme is a higher-order compact (HOC) scheme with fourth order spatial accuracy and second order temporal accuracy. Our results show that there is a very good agreement between both these methods which exemplifies the accuracy and credibility of our results.