bluuebunny/crossref_metadata_2025 huggingface dataset:
Causes and Remedies of High Jet Pipe Temperature in Turbo Shaft Engines : Case Studies
Authors: Mishra R.K. , Mishra A.K. , Gouda G.
Published: December 2023

Jet Pipe Temperature (JPT) is a representation of Turbine Entry Temperature (TET) and is one of the most critical parameters in a gas turbine engine. Excessive turbine temperatures result in decreased life or catastrophic failure of the engine. This paper presents some case studies analyzing the causes of such high JPT in a turbo shaft engine in association with helicopter operation, effect of high JPT on engine performance and life and highlights the precautions and preventions to be adopted from engine point of view.
Role of Engineering in Development of Economy, Society and People
Authors: Rajan Y.S.
Published: December 2023

No abstract
Challenges in Aero-Engine Joint Venture Design Development Certification and Technology Transfer Process in India
Authors: A.K. Mishra  , Scientist ‘C’  , Wg Cdr (Retd) Simon K John  , Sc ‘E’  , G. Gouda  , Scientist ‘F’
Published: December 2023

The development in the field of gas turbine engine from first generation to fifth generation is evident from the history. The ever changing requirement has driven continuous development in the area and has led the designers to struggle for best propelling machine to fly. In the global scenario it is evident that for keeping up with the pace of advancements in the gas turbine engine field, expertise is required for each subsystem/module. Major design houses of the world are now adopting an approach of developing expertise in a specialized area of aero engine development. Having developed the expertise in a specialized area, the complex aero engine can be developed through the joint venture route. In a country like India this new development philosophy through joint venture has been adopted in the recent past for many of the aero engine components. The critical issue for such a product to enter into the armed forces is certification and its associated manufacturing quality standards. This paper highlights the basic issues and challenges associated in a typical Indian Joint Venture for design development and Certification of aero engines and system. The paper also highlights the possible approach which can be adopted based on the real experience of certification process for a turbo shaft engine joint venture program recently undertaken in India between HAL and an OEM abroad.
Development of Rolling Element Bearing Test Bench Facility And Application of Wavelet Transform for Fault Diagnosis
Authors: Angello Innocent  , Animesh Chatterjee
Published: December 2023

The aim of this experimental study is to develop an efficient rolling element bearing fault detection technique which could be effectively utilized for easy interpretation of bearing signal data. This paper deals with a new scheme for the diagnosis of localized defects in rolling element bearing based on Wavelet Transform. Vibration signal for healthy bearing, bearing with outer race fault, inner race fault and ball fault were acquired from a bearing test bench fabricated at Naval Institute of Aeronautical Technology, Kochi. The vibration signal was acquired using an accelerometer, control card and Data acquisition card. The acquired signal was further processed using a time frequency analysis technique known as Wavelet Transform. The experiments were carried out using different mother wavelets. However, defect features were best obtained using Complex Gaussian Wavelet of order 8, thereby rendering easier interpretation of the analysed data.
Cases of Fall of Blue Aircraft Ice From Sky in India
Authors: Bimal K Srivastava
Published: December 2023

no abstract
Fretting Failure of Turbine Blades in a Turbojet Engine: A Case Study
Authors: R.K. Mishra  , K.S. Jayasimha  , A. Iftekar  , J.K.K. George
Published: December 2023

Gasturbines operate at extreme conditions, often at the design limits of turbine blades which are more likely to experience failures than other less stressed parts. Cases of blade failures are studied for a turbo jet engine in service. Small-amplitude relative oscillatory sliding displacements between the contacting surfaces of blade and disc are known as fretting and it arises as a result of cyclic loading of one of the contacting members. The paper presents case studies of fretting failure in turbine blades and suggests remedial measures to prevent such failures.
Flutter Qualification of a Composite Light Trainer Aircraft (Csir-Nal Hansa - 3 (Vt-Hoa))
Authors: N. G. Vijaya Vittala  , A.C. Pankaj  , C.N. Sathyanarayana  , M.V. Shivaprasad
Published: December 2023

This paper presents the aeroelastic analysis and flight flutter tests aimed at ascertaining the freedom from flutter instability in the design flight envelope of a composite light trainer aircraft. The critical flutter, divergence and control reversal velocities of the complete aircraft were computed using MSC/NASTRAN and the typical section method. The results thus obtained from the analyses have been correlated with the ground vibration and flight flutter test results. The dispersion in the damping and frequency results obtained from computations and the flight flutter tests were within acceptable limits showing a good correlation. The flutter margins and the total damping of the aircraft satisfy the JAR-VLA/ FAR 23 requirements, thus enabling the aircraft to be type certified for the required flight safety standards.
Asiml-1553: A Markup Language for Mil-Std-1553B Avionics Bus Scheduler and Interface Control
Authors: Neeta Trivedi
Published: December 2023

Modern avionics is highly software intensive with various software components residing on different subsystems interfaced through avionics bus. Avionics system designer is responsible for defining the bus frame timings, message transmission schedules and details of interfaces. These are translated into design and finally into source code by the designers of individual subsystems. Growing complexity of avionics software coupled with frequent changes has necessitated use of highly layered architecture with tight partitions and open standards in order to obtain better maintainability, testability, portability and ease of upgrade. Textual configuration files offer benefit over embedding the configuration details into the code in terms of development, testing and certification efforts. XML is emerging as the worldwide standard for defining configuration files. This paper proposes ASIML-1553, a markup language for defining configuration files for avionics bus scheduler and interface control for MIL-STD1553B bus. Data from a typical combat aircraft are taken as case study to discuss the advantages ASIML-1553 offers in terms of turn-around time, quality and reliability. ASIML1553 can easily be adapted for interfaces other than MIL-STD-1553B such as ARINC-429 or Ethernet.
3D Woven Composite Applications for the Next Generation of Aircraft Engines
Authors: A. Naik Rajiv
Published: December 2023

The use 3D woven composites is on the rise, especially in aircraft engine components. OEMs are recognizing the many performance and economic advantages offered by the 3D weaving process, especially in aircraft engine applications that require high damage tolerance. Near net shape preforms with high fiber volume can be produced using the 3D weaving process. 3D weaving also offers the designer with the choice of virtually unlimited fiber architectures and design possibilities. However, a good, reliable and computationally efficient design tool for 3D woven composites is a basic necessity in order to enable the designer to fully exploit the advantages offered by the 3D weaving process. A simple analytical tool like TEXCAD can provide reliable and quick estimates and parametric studies of the 3D stiffnesses and strengths over the full range of fiber architectures that are possible with 3D weaving. Challenges in the use 3D woven composites relate to the lack of structural progressive damage modeling capability, the lack of standards and methods for the quality control, inspection and process control of 3D weaving processes and a lack of a good understanding of the effects of defects and fiber architecture variability on mechanical properties.
Nanofiber Interleaved Composites for Aerospace Applications
Authors: N Shivakumar Kunigal , Chen Huanchun , Ali Mohamed
Published: December 2023

This paper extended the authors previous work of demonstrating the concept of polymer nanofiber interleaving to enhance the toughness of fiber reinforced carbon/epoxy composite laminates. In this study, in-plane tension, compression, interlaminar shear, and Mode I fracture and fatigue onset life properties were studied. Results demonstrated that by adding 1% weight of nanofibers in the form of interlayer in-plane tension and compression properties (strength, modulus, and Poisson’s ratio) of interleaved composites remained the same as base composites. Whereas polymer nanofiber interleaving increased interlaminar shear strength by 4%, fracture toughness by 150% and fatigue threshold energy release rate by 67%
Optimal Aircraft Conflict Resolution in Free Flight Using Simulated Annealing and Genetic Alogorithms
Authors: Chaugule Vishal , S Pant Rajkumar , Gomez Susana
Published: December 2023

Limitations of the existing Air Traffic Control (ATC) systems lead to problems like congestion in airspace, delays and improper detection of conflicts between the aircraft, and their resolution. The current trend is to shift from this centralized system to an autonomous one in which the assurance of separation depends on the aircraft themselves. This concept is termed as Free Flight. In the present study we deal with the optimal resolution of conflicts between three aircraft in level flight on intersecting routes. A geometric approach has been employed to resolve the conflicts using only speed changes of the aircraft. Three objective functions are proposed to obtain the best conflict free trajectories, which penalize the aircraft for the number of speed changes and/or the extent of the speed changes. Using stochastic methods for optimization viz. Simulated Annealing (SA) and Genetic Algorithms (GA), optimal conflict avoidance speed changes have been obtained. The resulting speed change sequences for the aircraft generated using SA and GA exhibit comparable trends and values. The solutions obtained are optimal not only in the context of the magnitude of speed change but also in the number of deviations from the original speed values.
Calibration of a Test Method to Measure Mode I, Mode II and Mode III Fracture Toughness of Engineering Materials
Authors: Kirthan L.J. , Lakshminarayana H.V. , Shivashankar R.S.
Published: December 2023

A refined finite element model and a new post processing sub program to determine mixed mode stress intensity factors and their variation along a surface crack front in components and structures is presented. The proposed finite element model employs a fine mesh of singular isoparametric pentahedral solid element with user specified number and size from one crack face to another and a number of such segments along a surface crack front. A compatible mesh of regular elements namely hexahedral solid element and pentahedral solid element is used to discretize the rest of the domain under consideration. Consistent with the use of the singular element, formulae to compute the Mode I, Mode II and Mode III stress intensity factors using displacements only of flagged nodes on flagged singular elements are implemented in a special purpose post processing sub program named SIF 1-2-3. In the present work the finite element models developed using ANSYS, a commercial FEA program, and the stress intensity factors determined using SIF 1-2-3 are validated using benchmarks. This finite element model is then used to calibrate a proposed test method to measure Mode I, Mode II and Mode III fracture toughness of engineering materials.
Flow Measurements in the Passages of Different Types of Diffusers of a Centrifugal Compressor at Off Design Conditions
Authors: Sitaram N. , Issac J.M. , Govardhan M.
Published: December 2023

Flow measurements in the passages of different types of diffusers of a centrifugal compressor at off design flow coefficients are presented and compared with those at design flow coefficient in this paper. The measurements are carried out using a precalibrated three hole pressure probe. The measurements are carried out in the passages of the following diffusers: vaneless, vane, low solidity vane and partial vane diffusers. The results are presented as contours, axially averaged and mass averaged flow parameters. The partial vane diffuser shows slightly improved flow field. At the above design flow coefficient, both vane and low solidity vane diffusers suffer large losses due to high incidences causing large drop in static pressure.
Real Time Estimate and Computational Model of Fighter Aircraft Fuel Gauge System
Authors: Usha G. , Prabhulla V.K. , Chandran  , Srinivasa Rao R. , Deshmukh Vijay
Published: December 2023

An onboard program for the fighter aircraft fuel gauge system is developed using a computational model resulting in to an optimal estimate of fuel gauge system. A fighter aircraft has several fuel tanks and the fuel quantity of the fuel tanks is required to be gauged reliably taking into account the various dynamic effects of flight maneuvers like aircraft pitch angle, roll angle and acceleration parameters for aircraft CG management. Real time estimation and computational modeling of fuel gauging system is realised by using the least square estimation numerical method with Microcontroller based Electronic unit. It was seen that the fluctuations in the fuel quantity estimation under the dynamic flight conditions are reduced and fuel gauging accuracy is improved.
Impact of Helium Permeability on Endurance and Altitutde Control of Geostationary Stratospheric Airship - A Mathematical Model
Authors: Kumar Garg Anuj , Kumar Burnwal Santosh , Pallapothu Asish , Singh Alawa Rohit , Ghosh A.K.
Published: December 2023

A geostationary stratospheric airship is lighter than air platform to be used for several civil and military purposes. In this study, the impact of Helium permeation through the hull and ballonet skin is considered. Mathematical modeling of the system is being done to estimate the amount of Helium and air transmission through the hull and the ballonet skin for a general airship system. Impact of permeation mainly affecting its ability to maintain constant altitude and a minimum level of differential pressure is shown in this study. A method is also devised so as to develop an open loop control system to maintain the altitude of the airship by maintaining the net vertical force due to buoyancy and weight on the airship as zero. Both the cases with and without the altitude control are simulated by numerically solving the model using RK4 algorithm. The results obtained are discussed and appropriate conclusions are drawn from the analysis.
Integrated Flight and Propulsion Control - A Review
Authors: Vinayagam A.K. , Sinha N.K.
Published: December 2023

Integrated Flight and Propulsion Control (IFPC) systems are gaining importance in modern fighter aircraft to enhance performance, safety and life. The performance enhancement of the aircraft can be achieved by making optimal use of the interactions between the propulsion system and the aircraft flight dynamics. The safety of the aircraft can be enhanced by the use of propulsion system forces and moments for reconfiguring flight control in the event of damage/failure of aerodynamic control surfaces. The life of the propulsion system can be traded for the performance and vice-versa by varying operating margins throughout the flight envelope. The integration of inlet control, nozzle control, thrust vector control and varying the stability margins of the engine according to the flight conditions offer unlimited possibilities in enhancing the performance and safety. This paper is aimed at summarizing all aspects of IFPC and provide an overview of research being carried-out in each of these fields
Effects of Inlet Pressure Distortion on the Performance and Flow Field of a Centrifugal Compressor at Design Condition
Authors: Sitaram N. , Govardhan M. , Murali K.V.
Published: December 2023

The present paper presents experimental results on the effects of inlet total pressure distortion on the performance and flow field of a centrifugal compressor. The total pressure at inlet is artificially distorted by means of a perforated sheet, which is supported by a support mesh. A total of eleven configurations, including clean inlet configuration, are tested. Performance measurements and impeller inlet and exit flow studies are carried out. The distorted inlet flow causes loss of energy, reduction in the maximum flow coefficient and perceptible decrease in the stable operating range of the compressor when compared with undistorted inlet flow. The reduction in stable operating range is the highest for 150° Distortion and the least for 4x22.5° Distortion. In radial distortion group, tip distortion has more detrimental effect on the operating range, energy coefficient and efficiency. The mass averaged total pressure at the impeller exit is the highest for clean inlet and the lowest for Hub+90° Distortion. The circumferential distortion has more adverse effect than the radial distortion on the flow parameters. The combined radial and circumferential distortion (Hub+90°) has the worst effect on the mass averaged flow parameters. As the Distortion Index (DI) increases, the mass averaged total pressure at exit stations decreases. Distortion sector angle of 60° having the lowest total pressure is found to be the critical sector for circumferential distortion configurations. As the Distortion Correlation parameter, DC(60) increases, the mass averaged total pressure for circumferential distortion configuration decreases.
Unification of Large Amplitude Vibration and PostBuckling Behavior of Structural Members
Authors: Venkateswara Rao G. , Konda Reddy G. , Subba Rao V.V.
Published: December 2023

In the deign of the modern aerospace structural members, due the stringent requirement of light weight and low margins of safety, it is essential to establish the design adequacy by evaluating the stiffness related behavior, like the large lateral amplitude/deflection vibration and postbuckling, through a rigorous geometric nonlinear analysis. Though many complex formulations, either by using the continuum or numerical methods are available in the literature, the heuristic formulae developed recently, for these entirely different nonlinear problems, are similar. Hence, it is possible to unify, these simple formulae, not recognized till now. The unification of these formulae facilitates to obtain the solution for the large amplitude vibration problem from the known solution of the postbuckling of the structural members and vice versa, for a specified lateral amplitude/deflection. This novel concept of the unification is successfully demonstrated through the isotropic uniform beams/columns and thin square plates.
Influence of Fuel Atomization on Combustor Lean Blowout: An Empirical Approach
Authors: Mishra R.K. , Kishore Kumar S. , Chandel Sunil
Published: December 2023

Empirical approach has been adopted to study the effect of operating conditions on atomizing parameters and influence of such parameters on lean blowout limit in a gas turbine combustor. Poor atomization represented by higher spray drop size is found to affect adversely the lean blowout limit. Low air pressure and low fuel temperature results in a higher fuel drop size and require more energy for evaporation and combustion initiation which has to come from more fuel or higher FAR thus raising the blowout limit. Empirical relations can predict reasonably when validated and updated with more and more experimental data.
Composites for Reinforcement of Damaged Metallic Aircraft Wings
Authors: Karuppannan D. , Rawat R.S. , Ramachandra H.V. , Saji D. , Varughese Byji
Published: December 2023

Advanced composites, because of their inherent directional properties and ability to take complex contours are ideally suitable for repairs even in aged metallic aircraft structures. The composite materials can be suitably tailored to suit the strength and stiffness requirement at location of the damage on the parent structure. The laminate patch can be bonded to the structure. This avoids the use of large number of fasteners that are required for repair with metallic repair patch. A composite patch repair has been carried out on a military aircraft wing. The skin and the spar flange near the landing gear part were cut in order to gain access to a loosened bolt. With a request from HAL (Nasik), National Aerospace Laboratories (NAL) has taken the responsibility of designing and realizing composite repair at the damaged locations. The geometry and lay-up of the patches have been arrived at based on the strength requirements. The patches were fabricated at NAL and the repair was implemented on the aircraft. The quality of the patch bonding was checked using non-destructive testing (NDT). The aircraft has completed about 130 hrs flying with the repair. The repair was certified by the regulating authority and has been recommended to be implemented on other twenty aircraft also. This task has been completed successfully and all the aircraft are flying. This is an important achievement both for NAL and HAL (Nasik). This paper discusses the repair design, patch fabrication and implementation of the repair.
Analysis of CFC Wing-Spar with Local Cutouts
Authors: Panbarasu K. , Ranganath V.R. , Subba Reddy T.C. , Vijayaraju K. , Shanmugham R.
Published: December 2023

In multi-cell aircraft wing construction, cutouts and vent-holes are commonly provided in the wing spars and ribs to facilitate fuel transfer across cells. While the web of the spar is expected to transfer shear loads under an overall bending load, presence of such discontinuities are of great concern. In particular, wing spars made of fiber reinforced composites, such discontinuities may result in fiber terminations and are well known locations of stress concentration. Present work attempts to analyze a carbon fiber composite (CFC) wing spar, with cutouts and vent-holes, under fixed beam conditions with the load applied through the shear centre of the spar to induce a pure bending stress at the cutout, through FE analysis and with a limited number of experiments. The study includes C-spars with and without skin-strips made of carbon fiber composites, and the cutout loaded in, both, tension and compression. The strain data measured extensively during the tests was employed to identify stress concentrations, critical failure locations and failure modes. The study establishes the need for modeling the whole loading assembly to achieve results close to experimental results.
Numerical and Experimental Analysis to Predict the Compressive Strength of Pristine Composite Laminates
Authors: Singh K.L. , Ranganath V.R. , Manjunatha C.M.
Published: December 2023

In this work, the numerical and experimental work has been carried out to verify the compressive strength of pristine composite laminates. Theoretical computations have been carried out using MATLAB to compute the strength and buckling load. Finite Element Analysis has been carried out for the composite laminate using two and three dimensional elements. PATRAN as the Pre and Post processing package and NASTRAN as the solver have been used in this work. The various failure theories considered in this article are Tsai-Wu, Hill, Hoffman, Maximum Stress and Quadratic failure theory (YSFT). All the first four failure theories are available as a standard criterion in the PATRAN package. The fifth quadratic failure criterion has been implemented using PATRAN Command Language. Static analysis along with failure theories has been carried out to compute the strength of the laminate. Static and buckling analysis has been presented for both in two-and three-dimensional models. Experiments have been carried out on number of pristine laminates and the strain values obtained from FEA have been compared with the experimental values. The theoretical computation provides a load value which is about the elastic limit of the specimen. It is generally observed that quadratic failure theory (YSFT) provides least failure indices and may be employed for conservative design.
Materials Characterisation and Structural Health Monitoring of Composite Structures Using Ultrasonic Guided Wave
Authors: Janardhan Padiyar M. , Balasubramaniam Krishnan
Published: December 2023

The ultrasonic guided waves are employed to develop a sensor system that can be permanently attached to the aerospace composite components for the purpose of continuous or intermittent monitoring of the health of the structure. The system is capable of detecting impact and dis-bond damages that occur during the service of the aircraft. The sensor patch design, sensor reliability, low footprint sensor electronics, data processing and evaluation automation, wireless communication, energy requirements, etc. will be discussed in this paper.
Localization of Low Flying Aircraft Using Acoustic Vector Sensor
Authors: Saravanakumar A. , Senthilkumar K. , Sadasivan S.
Published: December 2023

This paper addresses a method for estimating the linear flying trajectory of a fixed-wing aircraft based on narrow-band passive acoustical technique, which measures the instantaneous frequency of the acoustic signal emitted by the target and received by Acoustic Vector Sensor (AVS) placed on the ground. AVS consist of one microphone and three vector sensors orthogonal to each other. The received instantaneous frequency varies due to the acoustical Doppler Effect under the condition that the target flies at a constant velocity and the trajectory is a straight line. A four parameter model was developed to describe the aircraft trajectory. The four parameters are the targets travel speed, the source acoustical frequency, the time at which the target gets to the closest point of approach (CPA) to the sensor, and the CPA slant range to the sensor. Nonlinear least square (NLS) theory was used to estimate these parameters. The three dimensional AVS consists of three orthogonally placed particle velocity sensors and one sound pressure microphone. The four parameters mentioned above are measured using microphone. The particle velocity sensors are used for finding the direction of acoustic source.
Effect of Silicon Carbide Reinforcement on Wear Properties of A Glass Epoxy Composite for Aircraft Application
Authors: Madan H. M. , Prabhakar Karthik , Mishra R. K.
Published: December 2023

In the present investigation, the tensile and sliding wear properties of silicon carbide filled with glass epoxy polymeric composites were studied. The composites were prepared by dispersing different weight percentage of micro silicon carbide fillers in epoxy matrix and the mixture is then laid up on glass woven fabric by hand layup technique. Specimens were prepared out of the cured laminates and tests were conducted to study their tensile and wear properties. The test matrix for wear tests is defined using Taguchi approach. Sliding wear resistance increased with increase in SiC filler percentage though there has been a marginal decrease in tensile properties.
Use of Poke-Yoke for Right Manufacturing and Installation
Authors: Malagaudanavar Appasaheb , Singh Yogendra , Singh Narender
Published: December 2023

Hindustan Aeronautics Limited, Transport Aircraft Division, Kanpur manufactures HAL DO-228 a Light Transport Aircraft. Manufacturing of HAL DO-228 commenced as licensed production with Technology transfer from M/s Dornier GmbH, Germany. All the design data for manufacturing of parts, the manufacturing tooling and the processes were given under the agreement for Transfer of Technology. Number of aircraft have been built over a period spreading to more than two decades starting from the year 1984. In the recent years, we faced two distinct problems. One, defect occurred during manufacturing of two wing spar components. Another, operator faced problem due to wrong fitment of a part. We present these two interesting cases which were resolved by adopting poka-yoke methods.
Indigenous Development of a High Force Rating Electrodynamic Shaker System
Authors: Vasudevan Unni M.
Published: December 2023

In launch vehicles, all systems are subjected to vibration environment during flight. Vibration tests are performed to find out structural integrity and performance of the system for the intended use in a launch vehicle, under vibration environment. The vibration tests are carried out by employing suitable shaker as stand alone unit or with combination of slip table, depending upon the type of vibration levels and axis of vibration. Out of different types of shakers, electrodynamic shakers have wide frequency range so that the sine, shock and random tests are possible.

The force requirement of a shaker is dictated by the mass of the systems to be tested and the test levels. ISRO’ future vehicle sub assemblies, demand nearly 250 kN force capacity for the shaker. Indigenous development of such a high capacity system was initiated first time in the country, for self reliance in designing and realizing such high capacity test systems and to meet the schedule critical launch vehicle sub assembly test activities. This paper describes the challenges in the development of such a high capacity system in Vikram Sarabhai Space Centre (VSSC), Trivandrum.
Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims In an Axial Flow Turbine With and Without Wall Motion
Authors: Bansode Narendra
Published: December 2023

The objective of present investigation is to study aerodynamics of tip leakage flows near partial squealer rims in an axial flow turbine cascade with and without end wall in motion. The reaction turbine blade used in the present investigations has a blade length of 400 mm and a geometric deflection of 82°. The blade chord is 102 mm with an aspect ratio of 3.9. The tip gap is maintained at 2% (2.04 mm) and the squealer rims were of 1.02 mm height. A total of seven cases were investigated with different squealer geometries including case without squealer rim. The coefficient of secondary loss coefficient (CSKE) is used as objective function. Minimum CSKE indicates minimum losses. From the investigations it is concluded that full suction side squealer rim is the optimum squealer geometry among all cases studied as CSKE was found to be minimum for this geometry. The optimum case was selected for wall motion studies. Three wall motions, namely; 75%,100% and 125% of the inlet meridional velocity were maintained and investigated. The CSKE is reduced with all three end wall motions except very close to the end wall. The exit flow angle is reduced near the end wall as compared to no wall motion.
Theoretical and Numerical Studies Of Magneto-Rheological Damper
Authors: Mangal S. K. , Kumar Ashwani
Published: December 2023

This paper presents a theoretical and numerical studies based on Finite Element Method (FEM) of a Magneto-Rheological (MR) damper. In this article, the design considerations and magnetic flux density at the clearance space of the piston and the cylinder of the MR damper are studied. A theoretical model for the magnetic circuit design of the MR damper is developed which is subsequently used to calculate the damping force at various level of current. A FEM modeling of the same problem is then developed using ANSYS software to validate the theoretical modeling. The FEM modeling gives the magnetic flux density in the clearance space of the damper which in turn is used to determine the damping force. The damping force of the above two modeling is compared with each other and found to be in good agreement. The studies indicate that the both the modeling are effectively portraying the behavior of a MR damper and adequate enough for control and design of the damper. The results obtained in this paper will help the designers to predict the damping force of the damper.
Enhanced Model for Terminal Airspace Capacity Estimation
Authors: Bagg Debashish , Pant Rajkumar S. , Sharma Keshava , Chaugule Vishal
Published: December 2023

Terminal Airspace comprises the area around an airport in which various aircraft in its vicinity are in ascending or descending phases. This paper describes an enhanced model for estimation of Ultimate Capacity of Terminal Airspace, given its geometric layout, traffic data, and the separation minima maintained. This model can be used to determine the number of aircraft in the Terminal airspace of an airport that can be safely handled by the Air Traffic Controllers. An existing probabilistic model for Terminal Capacity assessment was enhanced to include operations on intersecting and parallel runways. An important out-come of this methodology is the minimum time gap between successive operation at the runway, which is utilized to draw a time space diagram of runway operation, and thus obtain an estimate of Delay under various operational scenarios. The model was first utilized to estimate the Terminal airspace capacity of the two most busy airports in India, viz., Mumbai and Delhi, and later for other main Airports viz., Kolkata, Chennai, Ahmadabad, Guwahati, Hyderabad, Kochi and Thiruvananthapuram. A critical analysis of the results lead to suggestions like slot distribution, rescheduling of aircraft, restructuring of spacio-geometrical conditions of airspace and airfield etc. that may be considered to increase capacity and reduce delays at Indian Airports.
Conceptual Design, Sizing and Thermal Analysis of An Alerting System for Manned Airships
Authors: Bhardwaj Utsav , Pant Rajkumar S.
Published: December 2023

This paper describes an automatic and self-contained electromechanical safety system for manned airships, which alerts the flight crew when the temperature at some point over the envelope exceeds a pre-determined safe limit. The system consists of a thin electrical wire that is looped over the airship envelope along its length, which melts at the location(s) at which the safe temperature is exceeded, and sounds an alarm in the crew cabin. A detailed technical description of the alerting system and all its elements is provided, and a methodology for carrying out sizing of the system, and to carry out thermal analysis is outlined. The methodology is used to size the system for an airship of 30 m envelope length cruising at a speed of 20 m/s at an altitude of 10,000 ft. Results indicate that the mass of the system is a small fraction of the force of buoyancy generated by the airship envelope. Thermal analysis indicates that the alerting system is thermally stable, and despite the fact that current is consistently and continuously flowing in the alarming circuit, the wires are not overheated. The system can be of great help in increasing operational safety levels of a manned airship.
Methodology for Simultaneous Simulation of Convective And Radiative Heating
Authors: Chiranjeevi Phanindra B. , Jeyarajan S. , Manoj R. , Vanitha K. , Geo John G. , Deependran B. , Chacko M. J.
Published: December 2023

During the ascent flight of a Launch Vehicle (LV), certain regions are exposed to radiative and convective heating simultaneously. A typical example is the flexible multilayer thermal barrier for launch vehicle base region which experiences both radiative heating from the plume and hot nozzle divergent as well as convective heating due to reverse flow. To design and evaluate the effectiveness of the thermal barrier, simultaneous simulation of both radiative and convective heating is essential. This was made possible by the utilization of controlled radiant heaters and a Convective Heating System (CHS), both acting simultaneously in a pre-designated sequence. Such a simulation is very challenging since, the simultaneous simulation of radiative heating and convective heating mutually interferes with their respective independent control systems. Besides, the influence of the boundary conditions in the heat transfer process is different for radiative and convective heating. Hence, a novel technique was adopted to isolate the respective control systems. Detailed tests were undertaken to map the flow field at various distances from the exit to determine the position of the test article. After extensive mapping, the facility was utilized for simulations of both radiative and convective heating simultaneously on a thermal protection element in the launch vehicle base region, which experiences simultaneous simulation of convective and radiative heating. The studies were able to bring out the effect of hot gas permeability and thermal response and ascertain that the back wall temperatures are within allowable temperature constraint. This mode of simulation is a new technique where both simultaneous simulation of convection and radiation was undertaken to simulate the actual environments of flight on a specific system
Nanocomposites for Space Applications
Authors: Prabhakaran R.
Published: December 2023

The drive to lower the cost of space launches has resulted in the use of polymer matrix composites with micro reinforcements such as carbon fibers. Further attempts to decrease the weight of spacecraft and to improve the performance have led to the addition of nano reinforcements to these composites. In this paper, the application of nanocomposites in spacecraft structures is reviewed. First, several nano reinforcements, such as graphene, fullerene, nanotubes, nanofibers, nanoclays and Polyhedral Oligomeric Silsesquioxane (POSS), are briefly reviewed. Then the stringent requirements of the space environment, in relation to material properties, are reviewed. The space environment poses several challenges such as ultraviolet radiation, temperature extremes, thermal cycling, charged particle radiation, impacts from micrometeoroids and orbital debris, and low earth orbital atomic oxygen. Next, the testing of candidate materials in actual space environment and at ground based testing facilities is reviewed. This is followed by specific applications of nanocomposites in space structures.
Experimental Evaluation of Isolated Intake for Hypersonic Air- Breathing Vehicle
Authors: Thiagarajan V. , Sharma R.K.
Published: December 2023

Isolated intake of an air-breathing conceptual hypersonic demonstrator vehicle has been experimentally characterized simulating the entry Mach number and the entry flow direction. A 1:8 scale intake model having provision to vary the entry area of the internal compression portion by means of actuating the intake cowl has been tested in the supersonic freestream Mach numbers 3, 3.44 and 3.9. Tests were carried out in the 0.3 m x 0.3 m trisonic wind tunnel at National Aerospace Laboratories, Bangalore. The result pertaining to M¥ = 3.44 is discussed in this paper. The effect of cowl position on the intake starting characteristics and performance are analyzed using wall pressure measurements, schlieren and oil flow visualization. Intake unstart occurred before the cowl reaching to its fully open position with the original hinge location. Essentially the strength of cowl leading edge shock increases as the cowl opening angle increases. The strong shock-boundary layer interaction in the convergent portion of intake aids the growth of the separation bubble in the flow path and that cause the intake to unstart. Improvement of intake starting by means of shifting the cowl hinge location downstream was attempted. Shifting the cowl hinge location downstream has improved the intake starting characteristics. On the improved configuration, the effect of combustion induced back pressure and the effect of cowl opening speed on intake unstart have been analyzed and quantified.
Lateral Adaptive Control of Parafoil-Payload System
Authors: Prateek Sazawal  , Ghosh A.K.
Published: December 2023

The motion of a parafoil is characterized by nonlinear dependence of aerodynamic loads on angle of attack. Nonlinear dynamics and non-rigidity of parafoil-payload system causes difficulty in estimating aerodynamic coefficients of the parafoil with respect to angular rates. The present paper addresses the problem of lateral control of a generic 9 degree of freedom parafoil-payload system under small perturbations. A Lyapunov based dynamic adaptive controller is proposed in order to control such a system with known static coefficients and unknown dynamic coefficients. It is demonstrated numerically that the proposed controller is capable of controlling the system without estimating dynamic coefficients (theoretically or experimentally).
Aviation Fuel Consumption Studies - HAL Bangalore Airport Scenario
Authors: Lathasree P. , A. Pashilkar Abhay
Published: December 2023

Air traffic density in India and the world at large is growing fast. The challenging problems encountered are flight delay and increased aviation fuel consumption. The method used for quantifying is by simulation for the selected aerodrome and air space. This paper presents the modeling, simulation and analysis of HAL Bangalore International Airport which has been carried out as part of the feasibility studies towards optimal aviation fuel consumption. Aviation Fuel consumption studies use concepts of minor rescheduling of flight times for ground operations and allowing aircraft to cruise at fuel optimal altitudes for air operations. Results presented in this paper are encouraging as it leads to fuel conservation during ground and air operations.
Buckling Analysis of Orthotropic Graphene Sheets Supported on Pasternak Elastic Medium Using Nonlocal Elasticity Theory and Differential Quadrature Method
Authors: Pradhan S. C.
Published: December 2023

In this paper, the small scale effect on the buckling analysis of bi-axially compressed orthotropic Single-Layered Graphene Sheets (SLGS) supported on elastic medium is studied. Elastic theory of the graphene sheets is reformulated using the nonlocal differential constitutive relations of Eringen. Both Winkler-type and Pasternak-type foundation models are employed to simulate the interaction between the graphene sheet and supporting elastic medium. Using the principle of virtual work the governing differential equations are derived for rectangular orthotropic graphene sheets supported on elastic medium. Solutions for buckling loads for various boundary conditions are computed using Differential Quadrature Method (DQM). Parametric study has been performed to investigate the dependence of small scale effect on various graphene sheet parameters. It is observed that the nonlocal effect is significant in graphene sheets supported on elastic medium and has a decreasing effect on the buckling loads.
Ballistic Performance of Thermally Exposed CFRP Composites
Authors: Velmurugan R. , Barchha Sushil
Published: December 2023

In this investigation, high velocity impact test was carried out to study the after effect of thermal loading on ballistic limits of composite laminates. Plain woven carbon/epoxy laminates with nominal thickness of 2.3 mm were fabricated by compression moulding technique. To study the effect of thermal loading, laminates were exposed to different temperatures of 60°C, 80°C, 100°C, 120°C, 140°C and 160°C for 24 h in hot air oven and brought back to room temperature. Impact test was carried out using single stage gas gun for velocity up to 115 m/s. The bullet used was Æ 9.6 mm and mass 14.20 gm. The results show that ballistic limit reduces from 83 m/s to 62 m/s with increase in loading temperature from 30°C to 160°C. For impact velocity above ballistic limit, energy absorbed by the laminates reduces with increase in loading temperature. Shear plug formation was observed during experiment as reported in literatures [4, 5 and 6]. An energy base mathematical model is employed to predict the ballistic limit. The model considered the energy loss due to various failure mechanisms that occurred during impact test. The predicted ballistic velocity and energy absorbed by laminates show good agreement with the experimental results.
All Electric Cooling System for Unmanned Aircrafts
Authors: Amaranatha Raju M. , Ranganayakulu C. , Ashok Babu T.P.
Published: December 2023

This study brings out two All Electric Environmental Control System (AE-ECS) configurations for Unmanned Aircraft air-conditioning and performance evaluation of these two configurations interms of power consumption and fuel mass penalty. In conventional (or traditional) Bleed Air System, hot air is extracted from the engine compressor whereas in Bleed less Air Cycle system/Bleed less Vapour Cycle Systems (also called AE-ECS) bleed air extraction from engine is eliminated. Eliminating the extraction of bleed air from the engine in both the systems of Bleed less Air Cycle and Vapour Cycle System, saves the engine energy and thus increases the engine efficiency/thrust. In the present study performance of the Bleed less Air Cycle and Vapour Cycle systems are studied for typical flight envelop and heat loads of 5 kW. Bleed less Vapour Cycle System consumed less electric power compared to Bleed less Air Cycle System when compared for 5 kW cooling system requirements for an Unmanned Aircraft system. Fuel mass penalties are also calculated and compared for these two system configurations.
Micromechanics Based Fibre Breaking Damage Mesomodel for Unidirectional Fibrous Laminated Composites
Authors: Mohite P.M. , Jain A. , Upadhyay C.S.
Published: December 2023

In the present study a micromechanics based damage mesomodel for the initiation and propagation of fibre breaking has been developed for unidirectional continuous fibrous composites under quasi-static loading. For the micromechanical analysis, an RVE which contains a right circular cylindrical fibre in a cubical matrix along with a thin interphase/interface between fibre and matrix is considered. The state of micro stress and / or micro strain in fibre, matrix and interphase is found from two micromechanical approaches: Hill’s Concentration Factors and Homogenization. A brittle type fracture criterion is used for fibre breaking. The fibre breaking damage initiation and evolution at lamina level is presented using the concepts of progressive damage mesomodel. The model is tested for (carbon) / BSL914C epoxy and Silenka E-Glass 1200tex/MY750/HY917/DT063 epoxy materials used in World Wide Failure Exercise (WWFE). The model is validated for fibre breaking mechanism by loading a unidirectional lamina in both axial tension and compression. The preliminary results obtained for fibre breaking damage initiation and propagation for lamina under longitudinal tension are in good agreement with the experimental results reported in WWFE.
Effects of Shear Deformation on Flexural Response of Laminated Composite I-Beam
Authors: Singh S. B. , Chawla Himanshu , Munjal Pankaj
Published: December 2023

In this paper, a computational approach based on a kinematic model for laminated composite I-section beam is presented. The flexural behavior of laminated composite I-beams is analyzed by using Classical Lamination Plate Theory (CLPT) and the First Order Shear Deformation Theory (FSDT). Based on these theories, a computer programme for analysis of laminated I-beam has been developed in MATLAB. The comparison of results obtained using both theories has been made. It is shown that the shear deformation has significant effect on the deflection of the beam. Furthermore, the laminated I-beam is also modeled using ABAQUS software package for numerical results using different value of load applied at mid-span of the beam. Results obtained using ABAQUS are compared with results obtained with self developed computer program in MATLAB. It is observed that there is good correlation between results obtained from ABAQUS and the computer program before local failure such as buckling of flanges and web occur. Finally, the effect of various parameters such as width-tothickness ratio of flanges, depth-to-thickness of web, and span length-to-depth ratio of I-beam has been investigated. It is concluded that the effect of web depth-to-thickness ratio has little effect on the overall flexural response of I-beam while the width-to-thickness ratio of flanges has significant effect on the flexural response of composite I-beams.