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Computational Study of performance Characteristics for Truncated Conical Aerospike Nozzles

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Journal of Thermal Science 2017年第6期26卷 483-489页

作者： prasanth p nair Abhilash Suryan Heuy Dong Kim Department of Mechanical Engineering College of Engineering Trivandrum Department of Mechanical Engineering Andong National University

Aerospike nozzles are advanced rocket nozzles that can maintain its aerodynamic efficiency over a wide range of altitudes. It belongs to class of altitude compensating nozzles. A vehicle with an aerospike nozzle uses less fuel at low altitudes due to its altitude adaptability, where most missions have the greatest need for thrust. Aerospike nozzles are better suited to Single Stage to Orbit （SSTO） missions compared to conventional nozzles. In the cur- rent study, the flow through 20% and 40% aerospike nozzle is analyzed in detail using computational fluid dy- namics technique. Steady state analysis with implicit formulation is carried out. Reynolds averaged Navier-Stokes equations are solved with the Spalart-AUmaras turbulence model. The results are compared with experimental results from previous work. The transition from open wake to closed wake happens in lower Nozzle pressure Ratio for 20% as compared to 40% aerospike nozzle.

关键词： aerospike nozzle plug nozzle advanced rocket nozzles thrust coefficient base pressure.

Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application

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Defence Technology（防务技术） 2023年第12期30卷 83-100页

作者： Bipin Sankar Karthik V Shankar Vamu Sunil Hemanth Kashyap S Nikhil nair Adarsh A.nair Abhinav p M Department of Mechanical Engineering Amrita Vishwa VidyapeethamAmritapuriIndia

Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and *** paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)*** analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values *** analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze *** hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal ***,the grain size was approximately 30%finer for spinodal bronze when compared with regular *** the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal *** was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze *** results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.

关键词： Quenching Water Brine SAE 40 oil Grain size Hardness Wear rate Spinodal decomposition CuSn Spinodal alloy CuNiSn

A Study on Catalysis by Ferrospinels for preventing Atmospheric pollution from Carbon Monoxide

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Open Journal of physical Chemistry 2011年第3期1卷 124-130页

作者： Chennampilly Ummer Aniz Thengumthanam Damodaran radhakrishnan nair School of Chemical Sciences Payyanur Campus Kannur University Kerala India

Ferrospinel catalyst samples containing Nickel, Cobalt and Copper have been synthesized by room temperature co-precipitation route and have been found to be effective for the oxidative removal of carbon monoxide from automobile exhaust gases even at relatively lower temperatures (cold-start). These catalyst materials have been characterized by modern physico-chemical techniques such as XRD, TG, BET-BJH and SEM etc. Nitrogen adsorption studies shows the samples are mesoporous in nature with pore diameter of 5 - 10 nm. The catalytic efficiencies of these materials of having various compositions have been tested in a series of temperature programmed oxidation reactions involving carbon monoxide and the results discussed.

关键词： Catalysis Ferrospinels Mesoporous Atmospheric pollution Carbon Monoxide Oxidation

Influence of Unbalance on Classification Accuracy of Tyre pressure Monitoring System Using Vibration Signals

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Structural Durability & Health Monitoring 2021年第3期15卷 261-279页

作者： p.S.Anoop pranav nair V.Sugumaran School of Mechanical Engineering Vellore Institute of TechnologyChennai CampusChennai600127India School of Electrical Engineering Vellore Institute of TechnologyChennai CampusChennai600127India

Tyre pressure Monitoring Systems(TpMS)are installed in automobiles to monitor the pressure of the *** pressure is an important parameter for the comfort of the travelers and the safety of the *** methods have been researched and reported for *** them,vibration-based indirect TpMS using machine learning techniques are the recent *** literature reported the results for a perfectly balanced ***,if there is a small unbalance,which is very common in automobile wheels,‘What will be the effect on the classification accuracy?’is the question on *** paper attempts to study the effect of unbalance of the wheel on the classification accuracy of an indirect TpMS *** tyres filled with air are considered with different pressure values to represent puncture,normal,under pressure and overpressure *** vibration signals of each condition were acquired and processed using machine learning *** procedure is carried out with perfectly balanced wheels and known unbalanced *** results are compared and presented.

关键词： Tyre pressure monitoring system wheel unbalance random committee classifier machine learning

Collapse of charge ordering in Bi_(0.5)Sr_(0.5)MnO_3 by cation disorder: a magnetic and structural investigation

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Journal of Rare Earths 2008年第2期26卷 237-240页

作者： S. Savitha pillai Rajasekhar Madugundo Santhosh. p. Nagappan nair Low Temperature physics Laboratory Department of Physics Indian Institute of Technology Madras Chennai -600036 Defence Metallurgical Research Labora- tory

The structure, transport, and magnetic properties of ***0.5MnO3 （LBSMO）（x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structural analysis showed that the LBSMO crystallized in an orthorhombic perovskite structure with pbnm space group for x=-0.1 and Imma space group for x=0.4 and the highly polarizable 6s^2 lone pair of Bi^3＋ was the ttming factor for the structural variations. Magnetic studies revealed that the replacement of Bi ions by La ions resulted in the collapse high temperature charge ordering state of BSMO and it order Ferro Magnetically （FM） with Tc around 355 and 330 K for x=0.1 and 0.4, respectively. Both ESR, temperature and field dependant magnetization suggested that there was a coexistence of FM and the paramagnetic phases well below Tc and the FM and CO-AFM phases below 250 K of LBSMO.

关键词： charge ordering (CO) colossal magneto resistance (CMR) rare earths

Computational study on flow through truncated conical plug nozzle with base bleed

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propulsion and power Research 2019年第2期8卷 108-120页

作者： prasanth p.nair Abhilash Suryan Heuy Dong Kim Department of Mechanical Engineering College of Engineering TrivandrumTrivandrum 695016India Department of Mechanical Engineering Andong National UniversityAndong 760749Republic of Korea

Conical plug nozzle and truncated conical plug nozzle are advanced rocket nozzles suitable for use as altitude compensating *** this study flow through the conical plug and truncated conical plug nozzles are numerically simulated to first validate with experimental data and then to compare the performance when a base bleed is *** numerical analysis has considered two-dimensional axisymmetric ***-averaged NavierStokes equations are solved with two equation shear stress transport k-ω turbulence *** the validation of the plug nozzle,flow features and wall pressure along the length of the nozzle is taken for different nozzle pressure *** the validation of truncated plug nozzle,flow features and base pressures at various nozzle pressure ratios are *** base bleed is taken as 2%of the inlet mass flow *** comparison of results shows that the introduction of base bleed helps to compensate for the loss of thrust due to conical plug nozzle truncation.

关键词： plug nozzle Aerospike nozzle Advanced rocket nozzle Reynolds-averaged Navier-Stokes(RANS) Base pressure Coefficient of thrust Base bleed Secondary flow

Robust Adaptive Gain Higher Order Sliding Mode Observer Based Control-constrained Nonlinear Model predictive Control for Spacecraft Formation Flying

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IEEE/CAA Journal of Automatica Sinica 2018年第1期5卷 367-381页

作者： Ranjith Ravindranathan nair Laxmidhar Behera Department of Electrical Engineering Indian Institute of TechnologyKanpur Kanpur-208 016India IEEE

This work deals with the development of a decentralized optimal control algorithm, along with a robust observer,for the relative motion control of spacecraft in leader-follower based formation. An adaptive gain higher order sliding mode observer has been proposed to estimate the velocity as well as unmeasured disturbances from the noisy position measurements.A differentiator structure containing the Lipschitz constant and Lebesgue measurable control input, is utilized for obtaining the estimates. Adaptive tuning algorithms are derived based on Lyapunov stability theory, for updating the observer gains,which will give enough flexibility in the choice of initial ***, it may help to cope with unexpected state jerks. The trajectory tracking problem is formulated as a finite horizon optimal control problem, which is solved online. The control constraints are incorporated by using a nonquadratic performance functional. An adaptive update law has been derived for tuning the step size in the optimization algorithm, which may help to improve the convergence speed. Moreover, it is an attractive alternative to the heuristic choice of step size for diverse operating conditions. The disturbance as well as state estimates from the higher order sliding mode observer are utilized by the plant output prediction model, which will improve the overall performance of the controller. The nonlinear dynamics defined in leader fixed Euler-Hill frame has been considered for the present work and the reference trajectories are generated using Hill-Clohessy-Wiltshire equations of unperturbed motion. The simulation results based on rigorous perturbation analysis are presented to confirm the robustness of the proposed approach.

关键词： Adaptive gain higher order sliding mode observer leader-follower formation nonlinear model predictive control spacecraft formation flying tracking control

Computational Study on the Influence of Number of Threads on the perfor-mance of Single Screw pump at High Angular Velocities

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Journal of Thermal Science 2017年第1期26卷 54-59页

作者： Jaison philip Abhilash Suryan T.V Sanand p Unnikrishnan nair S. Sivakumar Department of Mechanical Engineering College of Engineering Trivandrum Kerala India 695016 Turbo pump Division LPSC Valiamala Trivandrum Kerala. Department of Mechanical Engineering Rajadhani Institute Engineering & Technology Trivandrum Kerala India

Fluid flow in a screw pump which rotates at very high angular velocity is numerically analyzed. In the present study, fluid flow in screw pumps under high Reynolds number, of the order of 105, is considered. Screw pump has two major elements, a plain shroud which is a stationary element and a rotating hub with helical grooves contained within the shroud. In this paper, three variants of hubs with different number of thread starts numbering six, eight and twelve in combination with a plain shroud is studied. Each of the three possible combinations are analyzed on the basis of pressure rise developed, efficiency and shaft power. It was seen that pressure rise, efficiency and shaft power increases as the number of threads increases in the range of mass flow rates studied.

关键词： Screw pump, Turbulent flow, Angular velocity

Surface-Engineered Li4Ti5O12 Nanostructures for High-power Li-Ion Batteries

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Nano-Micro Letters 2020年第2期12卷 235-245页

作者： Binitha Gangaja Shantikumar nair Dhamodaran Santhanagopalan Centre for Nanosciences and Molecular Medicine Amrita Vishwa Vidyapeetham

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion *** this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate ***,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline *** Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,***,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 *** full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,***-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

关键词： Ultrafast charging Li-ion battery Lithium titanate Off-stoichiometric synthesis Surface chemistry