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Muduli S.K.,Regional Center for Military Airworthiness | Mishra R.K.,Regional Center for Military Airworthiness | Satpathy R.K.,Regional Center for Military Airworthiness | Chandel S.,DIAT
International Journal of Turbo and Jet Engines | Year: 2015

A highly loaded full-scale annular combustor is studied in the air-flow facility for the effect of operating variables such as compressor discharge velocity and fuel-air ratio on the performance parameters. The combustor is designed to operate at high pressures and high exit temperatures that impose stringent limitations on its performance such as pressure loss, exit temperature profiles and combustion efficiency. The effect of excess air ratio on performance parameters is found to be marginal over the range tested. Increasing the excess air ratio decreases the pressure loss, exit pattern factors and combustion efficiency. The inlet Mach no. is found to influence the pressure loss strongly and exit temperature patterns marginally. Combustion efficiency is found to deteriorate with increase in Mach number. This will in turn affect the integrity and life of hot end components of the aero engine. © 2015 by De Gruyter 2015.


Nirmala S.,Regional Center for Military Airworthiness | Ananda C.M.,National Aerospace Laboratories, Bangalore
Proceedings - 2015 International Conference on Cognitive Computing and Information Processing, CCIP 2015 | Year: 2015

Communication in Micro Air Vehicles (MAV) swarm flying is challenging and critical for functional integrity of the swarm network. MAVs are deployed in groups to realise useful applications from MAV. Such mode of deployment of MAVs in-group demands dedicated and well defined communication method, protocol, simplified control and data paths along with the redundancy management to mitigate the failures. On the fly communication failures or complete system failure is addressed by dynamic reconfiguration of fellow MAVs to restructure the network as per Binary Search Tree network (BSTN). BST based network for swarm flying enables simplified and structured network with ordered, dynamic and unique data paths. Reconfiguration of MAV nodes in the BSTN is critical for continued swarm and hence completion of intended function. The paper presents the BST based network for MAVs, communication protocol, metrics for configuration, failure scenarios and redundancy management. © 2015 IEEE.


Mishra R.K.,Regional Center for Military Airworthiness | Kishore Kumar S.,Gas Turbine Research Establishment | Chandel S.,Indian Defence Institute of Advanced Technology
International Journal of Turbo and Jet Engines | Year: 2015

Lean blow out characteristics in a swirl stabilized aero gas turbine combustor have been studied using computational fluid dynamics. For CFD analysis, a 22.5° sector of an annular combustor is modeled using unstructured tetrahedral meshes comprising 1.2×106 elements. The governing equations are solved using the eddy dissipation combustion model in CFX. The primary combustion zone is analyzed by considering it as a well stirred reactor. The analysis has been carried out for different operating conditions of the reactants entering into the control volume. The results are treated as the base-line or reference values. Combustion lean blow-out limits are further characterized studying the behavior of combustion zone during transient engine operation. The validity of the computational study has been established by experimental study on a full-scale annular combustor in an air flow test facility that is capable of simulating different conditions at combustor inlet. The experimental result is in a good agreement with the analytical predictions. Upon increasing the combustor mass flow, the lean blow out limit increases, i.e., the blow out occurs at higher fuel-air ratios. In addition, when the operating pressure decreases, the lean blow out limit increases, i.e., blow out occurs at higher fuel-air ratios. © 2015 by De Gruyter.


Mishra R.K.,Regional Center for Military Airworthiness | Srinivasan K.,Hindustan Aeronautics Ltd Engine Division | Thomas J.,Hindustan Aeronautics Ltd Engine Division | Vaishakhi N.,Hindustan Aeronautics Ltd | Bhat R.R.,Hindustan Aeronautics Ltd
Journal of Failure Analysis and Prevention | Year: 2014

Failure of low pressure turbine rotor blade in a low bypass turbofan engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade failed. The failure has originated from the leading edge and has propagated towards the trailing edge. Intergranular features and high oxidation on the fractured surface are the cause of failure which is probably due to creep-stress rupture. This failure has caused extensive damages in low pressure turbine module and also in downstream modules as a secondary effect. Remedial measures are also suggested to prevent such failures. © 2014 ASM International.


Kale S.S.,Regional Center for Military Airworthiness Foundry and oForge | Raja V.S.,Indian Institute of Technology Bombay | Bakare A.K.,Regional Center for Military Airworthiness
Corrosion Science | Year: 2013

Studies were conducted to investigate the effect of polymer matrix composite stiffener (patch) on environmentally assisted cracking (EAC) susceptibility of pre-cracked alclad Al-Zn-Mg-Cu-Cr alloy in 3.5wt.% NaCl environment. The EAC threshold stress intensity of the peak and two-step aged alloy was reduced from 26 to 7MPam1/2 and 31to 8MPam1/2 respectively under the influence of patch. The plateau crack velocity was increased from 2.5×10-9 to 5.1×10-9m/s for peak aged and 1.2×10-9 to 2.0×10-9m/s for two-step aged tempers in patched condition. The significant increase in EAC susceptibility was attributed to crevice effect generated by the stiffener. © 2013 Elsevier Ltd.


Kale S.S.,Regional Center for Military Airworthiness Foundry and Forge | Raja V.S.,Indian Institute of Technology Bombay | Bakare A.K.,Regional Center for Military Airworthiness
Corrosion Engineering Science and Technology | Year: 2014

Stiffening of Al alloy aircraft structures with carbon fibre reinforced plastic laminate called 'patches' is considered as a viable option to enhance fatigue life. Interface so created between the reinforcement and Al alloy structure is potential site for crevice corrosion attack. Therefore, studies were conducted to investigate the interface corrosion behaviour of peak and two-step aged Al-Zn-Mg-Cu-Cr alclad alloy with and without the patch and examine the possibility to control the interfacial attack with the addition of cerium chloride inhibitor exposed to 3.5 wt-% NaCl solution for the durations of 2 and 168 h. Electrochemical impedance spectroscopy revealed that the interface attack was significantly reduced by the addition of 1000 ppm cerium chloride. The response of the peak and two-step aged alloy for such an addition was further investigated and found that the alloy under step aged condition behaves better than that of the peak aged condition.©2014 Institute of Materials, Minerals and Mining.


Dileep S.,Hindustan Aeronautics Ltd | Esakki Muthu S.,Hindustan Aeronautics Ltd | Udayanan P.,Hindustan Aeronautics Ltd | Mishra R.K.,Regional Center for Military Airworthiness
Journal of Failure Analysis and Prevention | Year: 2016

The effect of the fatigue damage parameter on the cumulative life of a high-speed turbine rotor has been estimated through finite element approach. Two most commonly used multiaxial fatigue damage models based on critical plane approach-Fatemi Socie (FS) model, and Kandil Brown and Miller model (KBM) have been used to estimate the fatigue life. Structural integrity test was carried out in spin test facility to validate the simulation results. KBM model for fatigue life estimation and LMP model for creep damage predicted a cumulative life within a factor of 1.5 scatter band of the experimental value. The combination of FS model for fatigue life estimation and LMP model could predict cumulative life only within a scatter band of 2. Some of the shortcomings attributed to LDS method can be obviated using a suitable fatigue damage parameter. The study provides invaluable input and confidence for the life prediction of high-speed gas turbine rotors. © 2016, ASM International.


Mishra R.K.,Regional Center for Military Airworthiness | Srinivasan K.,Hindustan Aeronautics Ltd
Journal of Failure Analysis and Prevention | Year: 2016

Failure of low-pressure (LP) turbine rotor blades in low bypass military turbofan engines is a great concern for designers, manufactures, repair and overhaul agencies, operators, and airworthiness authorities. The present paper analyzes the LP turbine blade failure cases to determine its root cause. Forensic and metallurgical investigations are carried out on the failed blades. In most cases, the failure was originated from the leading edge and had propagated toward the trailing edge. Intergranular features and high oxidation on the fractured surface have been found as the cause of fatigue failure. Operation at elevated temperatures for considerable time was found responsible for these fatigue failures. Malfunction of fuel system, failure in control sensors, and nonuniformity in atomizer characteristics were the root cause of high temperature in turbine leading to the failure of blades. The paper also presents various remedial measures to address the blade failures from manufacturing and operational points of view. © 2016, ASM International.


Sahoo B.,Regional Center for Military Airworthiness | Satpathy R.K.,Regional Center for Military Airworthiness | Panigrahi S.K.,Indian Defence Institute of Advanced Technology
International Journal of Turbo and Jet Engines | Year: 2016

This paper deals with failure analysis of a low-pressure turbine blade of a straight flow turbojet engine. The blade is made of a wrought precipitation hardened Nickel base superalloy with oxidation-resistant diffusion aluminizing coating. The failure mode is found to be fatigue with multiple cracks inside the blade having crack origin at metal carbides. In addition to the damage in the coating, carbide banding has been observed in few blades. Carbide banding may be defined as inclusions in the form of highly elongated along deformation direction. The size, shape and banding of carbides and their location critically affect the failure of blades. Carbon content needs to be optimized to reduce interdendritic segregation and thereby provide improved fatigue and stress rupture life. Hence, optimization of size, shape and distribution of carbides in the billet and forging parameters during manufacturing of blade play a vital role to eliminate/reduce extent of banding. Reference micrographs as acceptance criteria are essential for evaluation of raw material and blade. There is a need to define the acceptance criteria for carbide bandings and introduce more sensitive ultrasonic check during billet and on finished blade inspection. © 2016 by De Gruyter.


Mishra R.K.,Regional Center for Military Airworthiness | Ahmed S.I.,ORDAQA Engines | Srinivasan K.,Hindustan Aeronautics Ltd Engine Division
Journal of Failure Analysis and Prevention | Year: 2013

This paper investigates a bird strike incident of a military gas turbine engine. The jet pipe temperature of the engine shoot up and rotor speed reduced suddenly during takeoff roll. Long flame was noticed from the engine and aircraft crashed at runway end. Forensic analysis of remnants collected from flow passages confirmed the bird ingestion. Blockage of flow passages due to the presence of bird has led to engine surge and high gas temperature resulting in extensive damage of low pressure turbine module. The paper also proposes remedial measures to avoid such bird strikes during flight. © 2013 ASM International.

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