Aero Engine Performance Evaluation During Missile Firing Test

Evaluation of engine performance during armament firing in fighter aircraft is a vital qualification aspect for airframe engine integration. Ingestion of missile’s efflux into air intake results in rapid increase of engine inlet temperatures (temperature ramps) which cause flow disturbance to the compressor. Temperature distortion caused due to armament firing and its effect on compressor stability during flight testing is evaluated. Accordingly mitigation actions are recommended for stall/surge free operations. Distortion descriptors are assessed using simulation model (engine performance program) and results compared with engine distortion limits.

Parametric Evaluation on the Response of Damaged Simple Supported Structure Under Transit Mass

In the present article, the responses of a double cracked simply supported beam have been investigated. The responses of the structure are determined using Duhamel integral method numerically and validated with finite element analysis (FEA) using ANSYS WORKBENCH 2015 along with experimental verifications. The mass is moving on the structure in terms of critical speed of the structure. The normalized deflections of the structure at different damaged configurations are calculated. The influences of speed, mass, crack depth and crack location on the structures response are investigated. It is observed that the results obtained from Duhamel integral converge well with FEA and experimental verifications.

Structural Design and Analysis of Cylindrical Squirrel Cage to Meet Stiffness, Strength and High Cycle Fatigue Life for an Aero Engine

Squeeze film dampers have traditionally been used in aircraft engine to overcome stability and vibration problems that are not adequately handled with conventional style bearings. One of the key design features in a squeeze film damper [1] configuration is the introduction of flexibility in the bearing support. The simplest means to provide the support flexibility in the squeeze film damper is through the use of squirrel cage [2]. This paper deals with structural design analysis of cylindrical squirrel cage of an aircraft engine. Design of the squirrel cage needs a balance between stiffness and strength requirements. To meet the strength, stiffness and fatigue life requirements, squirrel cage web dimensions and fillet radius are modified. The various configurations of the squirrel cage have been evaluated to arrive at the optimum design. Stress analysis of the bearing has been carried out for axial, radial unbalance loads. Stress distribution in the web region has been studied in detail. High cycle fatigue life margins are estimated using Goodman diagram. The squirrel cage web dimensions and fillet radius are modified to improve HCF life requirements. The operating stresses in the squirrel cage are reduced while meeting the stiffness and HCF life requirements of the component.

A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

Multi Objective Optimisation of an Aero Engine Rotor System Using Nondominated Sorting Genetic Algorithm (NSGA)

A comprehensive multi-objective optimisation methodology is presented and applied to a practical aero engine rotor system. A variant of Nondominated Sorting Genetic Algorithm (NSGA) is employed to simultaneously minimise the weight and unbalance response of the rotor system with restriction imposed on critical speed. Rayleigh beam is used in Finite Element Method (FEM) implemented in-house developed MATLAB code for analysis. The results of practical interest are achieved through bearing-pedestal model and eigenvalue based Rayleigh damping model. Pareto optimal solutions generated and best solution selected with the help of response surface approximation of the Pareto optimal front. The outcome of the paper is a minimum weight and minimum unbalance response rotor system which satisfied the critical speed constraints.

Analysis of Infinitely Short and Infinitely Long Hydrodynamic Journal Bearings Under Micro-Polar Fluid by Direct Integration Method

In the present paper Reynolds equation of lubrication under micro-polar fluid for journal bearing is solved by direct-integration method under infinitely long and infinitely short journal bearing assumptions [1]. Infinitely long-bearing and infinitely short bearing solutions are the two available approximate closed form solutions for journal bearings. In the present investigation, solution of Reynolds equation i.e. pressure profile is compared with pressure profile obtained by previously used approximate method like finite difference method (FDM). Mentionable here that any approximation method needs lots of calculation and computer programing to get the result. In the present work it has been found that direct-integration method leads the almost same result as the conventionally used complex finite difference method. CFD analysis is also presented in the present work to justify the profile obtained by direct numerical method. It has seen here that theoretical and simulation results are in good agreement to each other’s.

Numerical Analysis of Direct Type Greenhouse Dryer

For food preservation, drying techniques is most widely used. Earlier drying was done openly in sun. But now with increased awareness, drying of agricultural produce is done with care. Greenhouse dryers are being mostly used. Good greenhouse dryers are considered one which can dry products in short span of time. For obtaining good quantity of dried products, the design of greenhouse dryer should be such that the air circulation is good and high temperature can be achieved near the crops. In present work, Computational Fluid Dynamics (CFD) approach has been used to visualize the air flow pattern and temperature distribution near the crops i.e., inside the direct type greenhouse dryer. Experimentally obtained data has been used as boundary conditions and numerically obtained results are helpful in understanding local parameters which cannot be found out experimentally.

Revisiting V-3 Canon for the Application of Single Stage Gas Gun

Single stage gas guns are typically used for accelerating the projectiles in bird and hail impact tests of aerospace components and engines. In this paper an alternative design for single stage gas gun is studied, which is derived from V3 canon. Three dimensional numerical simulations is carried out for the optimal secondary connection angle with the main barrel. A one dimensional code is developed for the V3 canon based design. Design of experiments conducted to find the response surface for the optimal location of the secondary connection, volume and pressure of the secondary tank.

Aerodynamic Performance of an Elliptical-Bladed Savonius Rotor Under the Influence of Number of Blades and Shaft

In the past, various influencing parameters of the conventional semicircular-bladed Savonius rotor such as overlap ratio, aspect ratio, number of rotor blades have been optimized through numerical and experimental investigations to improve its performance. Furthermore, the rotor performance under the influence of various blade profiles, shaft, endplates, and augmentation techniques has also been studied. Recent rudimentary studies with an elliptical-bladed Savonius rotor have demonstrated its potential to harness the wind energy more efficiently; however, its influencing parameters have not been thoroughly studied and therefore they need to be optimized to arrive at a suitable design configuration. In view of this, the objective of the present investigation is to optimize the number of elliptical blades on the rotor and then to find the influence of shaft with the optimized number of blades on the rotor performance. For this, 2D unsteady simulation is carried out with different combinations of blades, and after having optimized the number of blades, the influence of shaft on the rotor performance is studied. The continuity, unsteady Reynolds-Averaged Navier-Stokes (RANS) equations, and two equation eddy viscosity SST (Shear Stress transport) k-ω model are solved by using the commercial FVM based solver ANSYS Fluent. The torque and power coefficients are calculated as a function of tip speed ratio (TSR) and at rotating conditions. The total pressure, velocity magnitude, turbulence intensity and streamline patterns are obtained and analyzed to arrive at the intended objective. The numerical investigation demonstrates an improved flow characteristics and performance coefficients of the 2-elliptical-bladed profile without shaft.

Flutter Alleviation by Aeroelastic Tailoring of a Transonic Rotor Blade

High asynchronous self-excited blade response was observed in a transonic first stage rotor during the evaluation of flutter stability in high forward speed conditions. This candidate baseline rotor stage is a highly loaded, snubber-less bladed-disc configuration mounted in an axial low pressure compressor with tip speed in the order of 400 m/s. During the tests, the high asynchronous blade response was measured by strain gages, tip timing system and unsteady blade pressure transducers, which were correlated with analytical predictions. To alleviate this problem, it was attempted to tailor the first rotor blade configuration alone by adhering to all the constraints such as geometric, aerodynamic matching, material selection and utilising the same dovetail root configuration in the existing disc configuration. While tailoring the rotor blade, the critical blade parameters such as axial chord, thickness to chord, stagger, camber, leading and trailing edge radius were iterated from hub to tip. In the tailored rotor blade, the first flexure mode frequency, 1F was improved by 45% whereas the separation between second flexure, 2F and torsion mode, 1T were improved by over 30% with 4.9% weight penalty. Using the one way fluid-structure interaction approach, the blade incidence variation for different inlet pressure conditions and aerodynamic damping were evaluated using energy method for both the configuration. Blade sets of the tailored configuration were manufactured and tested in a dedicated compressor test facility, where characteristics were generated from 70% to 100% corrected speeds. The rig tests confirmed the predicted compressor performance as well as the improvement of natural frequency using blade mounted strain gages for the tailored blade. Upon the verification in the test rig, the tailored rotor configuration was further fitted in the engine and tested up to 103.3% of its design speed. The blade experienced two different inlet total pressure conditions in the test rig and engine tests. The unsteady pressure transducers and blade tip timing sensors did not show any asynchronous response in the corrected speed range for the tailored configuration. Compared to the baseline rotor blade, this tailored rotor blade demonstrated the absence of asynchronous response in the fundamental flexure mode and also well correlated with the aerodynamic damping prediction by energy method. Using this correlation, it is further analytically demonstrated that the blade will have sufficient aerodynamic damping at higher forward speeds and also minimal incidence variation in these conditions.