Department of Mechanical Engineering

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IIT Jodhpur

Rice-Wheat Consortium has been promoting resource conserving technologies in the Indo-Gangetic Plains(IGP) for past several years for timely planting of crops using simple vertical shocker type Zero-till Ferti-seed drills. Many farmers have purchased these zero-till drills in the south west region of the Indo-Gangetic Plains. Zero-till planting was introduced to advance the planting of crops to improve productivity, particularly in the winter season. Timely planting of wheat is known to improve crop productivity in the range of 40-50Kg/day/ha, besides significant saving in labor, fuel and water. RWC recently introduced a new second generation multi-crop planter zero till prototype to replace the traditional zero- till design. In order to further enhance the benefits of resource conserving technologies (RCTs), a 'head' specific micro-turbo pump was indigenously developed to save on untapped free surface flow power and economize on fuel green house emissions and energy. In field evaluation trials, the micro-turbo pump was found useful for the Canal- irrigated areas. The major feature of the 'head' specific micro-turbo pump is its robust and reliable design. The turbo-pump prototype can be easily manufactured locally to cater to pumping and for use in several other farm product processing operations. Water pumping from the tail race of the pump location was adapted keeping in mind, also the water table development at the larger radius from the location of surface flow replenishing water tables stressed by bore well and other water suction devices located at a higher head compared to flowing surface water. The whole system comprising the RCT and the turbo- pump installation were experimented and critically analyzed for the time span from 2003-2009. It is concluded that the head' specific micro-turbo pump is synergetic to RCTs and the newly designed pump can be used elsewhere in canal irrigated areas.

World University root node

American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009

Experimentation of new resource conserving technology in synergy with micro-turbo-based canal irrigation system

Euler angles are generally used for representing rigid body rotation in three dimensions. In this paper we introduce a concept of Euler-angle-joints (EAJs) which are nothing but three revolute joints so connected by imaginary links with zero length to represent particular Euler angle set. These EAJs can be represented using the well-known Denavit-Hartenberg (DH) parameters. The proposed EAJs are useful in representing a spherical joint present in any multibody system. One can then derive a corresponding decoupled natural orthogonal complement (DeNOC) matrices used in dynamic formulation to obtain the analytical expressions of the generalized inertia matrix elements in scalar form. These expressions are used to develop an O(n) - n being the number of degree-of- freedom of a serial chain - recursive forward dynamics algorithm. The methodology suggested is illustrated with a numerical example. © 2009 by ASME.

Proceedings of the ASME Design Engineering Technical Conference

Denavit-Hartenberg parameters of Euler-angle-joints for order (N) recursive forward dynamics

In this present work, the nonlinear response of a single-link flexible Cartesian manipulator with payload subjected to a pulsating axial load is determined. The nonlinear temporal equation of motion is derived using D'Alembert's principle and generalised Galerkin's method. Due to large transverse deflection of the manipulator, the equation of motion contains cubic geometric and inertial types of nonlinearities along with linear and nonlinear parametric and forced excitation terms. Method of normal forms is used to determine the approximate solution and to study the dynamic stability and bifurcations of the system. These results are found to be in good agreement with those obtained by numerically solving the temporal equation of motion. Influences of amplitude of the base excitation, mass ratio, and amplitude of static and dynamic axial load on the steady state responses of the system are investigated for three different resonance conditions. For some specific conditions, the results obtained in this work are found to be in good agreement with the previously published experimental work. The results obtained in this work will find applications in the design of flexible Cartesian manipulators with payload. © 2008 Springer Science+Business Media B.V.

Nonlinear Dynamics

Nonlinear response of a flexible Cartesian manipulator with payload and pulsating axial force

Prediction of cutting forces and machined surface error in peripheral milling of curved geometries is non-trivial due to varying workpiece curvature along tool path. The complexity in this case, arises due to continuously changing process geometry as workpiece curvature varies along tool path. In the presence of cutter runout, the situation is further complicated owing to changing radii of cutting points. The present work attempts to model process geometry in machining of curved geometries and in the presence of cutter runout. A mathematical model computing process geometry parameters which include cutter/workpiece engagements and instantaneous uncut chip thickness in the presence of cutter runout is presented. The developed model is more realistic as it accounts for interaction of cutting tooth trajectory with that of preceding teeth trajectories in computing process geometry. Computer simulation studies carried for this purpose has shown that it is essential to account for teeth trajectory interactions for accurate prediction of process geometry parameters. This aspect is further confirmed with machining experiments, which were conducted to validate this aspect. From the outcomes of present work, it is clearly seen that the computation of process geometry during machining of curved geometries and in presence of cutter runout is not straightforward and requires a systematic approach as presented in this paper. © 2009 Elsevier Ltd. All rights reserved.

International Journal of Machine Tools and Manufacture

Process geometry modeling with cutter runout for milling of curved surfaces

Flight test data of helicopters indicate that vibratory levels in the fuselage exhibit a wide spectrum of frequencies including the dominant blade passage frequency and its integer multiples. The present work attempts to understand the reason for the existence of several frequencies in the response of the fuselage and possible cause for this observed phenomenon by formulating a computational aeroelastic model. In this study, dynamic stall and dynamic wake effects are incorporated in a coupled aeroelastic analysis to investigate blade sectional loads, hub loads and trim condition of the helicopter. The differential equations of motion are solved in time domain in a sequential manner to obtain the response of all the blades in the rotor system, the inflow variables, and the sectional loads at every time step. The influence of aerodynamic modeling on the trim condition and aeroelastic response of the rotor blade in forward flight has been brought out. It is found that the aerodynamic model incorporating dynamic wake and dynamic stall effects predict the trim parameters whose variation with forward speed resemble qualitatively similar to those obtained in flight test. A comparison of variation of blade sectional lift for various aerodynamic models indicates that in the advancing side of the rotor, dynamic stall effects introduce a shift in the azimuth angle at which the minimum lift occurs. It is also shown that the structural coupling due to blade pretwist significantly influences the rotor blade response and loads compared to an untwisted rotor blade. Copyright 2008 by the American Helicopter Society International, Inc. All rights reserved.

American Helicopter Society International - AHS Specialists' Conference on Aeromechanics 2008

Influence of dynamic stall and dynamic wake effects on helicopter trim and rotor loads

Bimetallic welds (BMWs) play a critical and indispensable role in the primary heat transport piping system of nuclear reactors. The primary heat transport system itself is the critical part of a nuclear reactor. Any failure of this system can lead to very grave consequences, not only speaking of huge monetary losses resulting from non-utilization of the reactor setup, but also immensely valuable and irreparable loss of human life. This paper describes the experimental efforts towards estimation of Gurson material parameters of base metal and weld metal regions of a BMW so as to use the micromechanical modelling approach for addressing the structural integrity issues in BMWs. © IMechE 2008.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

Estimation of Gurson material parameters in bimetallic weldments for the nuclear reactor heat transport piping system

The development of propulsion system technology over the last few decades has encountered and overcome several technological barriers. A large number of problems were resolved resulting in considerably higher component efficiencies and reduced fuel consumption. These advances led to lighter overall designs and higher power densities compared to earlier designs. The accomplishment of lighter designs for the turbomachinery components also led to some drawbacks due to the reduced margins on the design factor-of-safety. Consequently, aeroelastic stability has become a major concern, and is oñen the limiting design constraint. So a careful and systematic study of coupled bending-torsion flutter of a cascade in incompressible flow was carried out which requires estimation of unsteady aerodynamic loads, and a structural model of the cascade. Unsteady aerodynamic loads were evaluated using Whitehead's solution for incompressible flow through a cascade of arbitrary geometry and interblade phase angle. The lift and moment coefficients calculated were found to match within the four decimal place accuracy with the results given by Whitehead and other literature. The blades were modeled as an equivalent 2-D section at 75% of span, and structural and inertia! couplings were lumped into an effective CG-EA offset. Structural damping was included in the equations of motion. The resulting complex eigenvalue problem was solved recognizing the fact that there are two parameters in the eigenvalue problem, namely the reduced frequency k and the interblade phase angle ß. The critical flutter speed was determined by minimizing it with respect to ß, keeping the constraint on ß as suggested by Lane. The solution provided the critical flutter speed with respect to both the torsion and the bending modes as a function of the interblade phase angle as well as dominant vibration frequencies at flutter. Various structural and aerodynamic parameters of the cascade were varied and the effect of the variations on the coupled bending torsion flutter was studied. A jump was observed in the flutter boundary near frequency ratio of I, which was explained by the change iri the mode shape of the vibration, which is represented by interblade phase angle. The developed technique can be used as a preliminary design tool for the aeroelastic flutter analysis of turbo-machinery blades. ©Freund Publishing House Ltd.

Fulltext

International Journal of Turbo and Jet Engines

Effects of geometric and structural parameters on coupled bending torsion flutter in turbo machinery blades

Flight test data of helicopters indicate that vibratory levels in the fuselage exhibit a wide spectrum of frequencies including the dominant blade passage frequency and its integer multiples. The present work attempts to understand the reason for the existence of several frequencies in the response of the fuselage and possible cause for this observed phenomenon by formulating a computational aeroelastic model. In this study, the effect of pretwist on the trim condition and aeroelastic response of a rotor system with dynamic stall and dynamic wake has been analysed. The differential equations of motion are solved in time domain in a sequential manner to obtain the response of all the blades in the rotor system, the inflow variables, and the sectional loads at every time step. The influence of aerodynamic modeling on the trim condition of the rotor blade in forward flight has been brought out. It is found that the aerodynamic model incorporating dynamic wake and dynamic stall effects predict the trim parameters whose variation with forward speed resemble qualitatively similar to those obtained in flight test. It is shown that the structural coupling due to blade pretwist significantly influences the rotor blade response and loads compared to an untwisted rotor blade.

34th European Rotorcraft Forum 2008, ERF34

Effect of pretwist on aeroelastic response of a rotor system with dynamic stall and dynamic wake

The development of propulsion system technology over the last few decades has encountered and overcome several technological barriers. A large number of problems were resolved resulting in considerably higher component efficiencies and reduced fuel consumption. These advances led to lighter overall designs and higher power densities compared to earlier designs. The accomplishment of lighter designs for the turbomachinery components also led to some drawbacks due to the reduced margins on the design factor-of-safety. Consequently, aeroelastic stability has become a major concern, and is often the limiting design constraint. So a careful and systematic study of coupled bending-torsion flutter of a cascade in incompressible flow was carried out which requires estimation of unsteady aerodynamic loads, and a structural model of the cascade. Unsteady aerodynamic loads were evaluated using Whitehead's solution for incompressible flow through a cascade of arbitrary geometry and interblade phase angle. The lift and moment coefficients calculated were found to match within the four decimal place accuracy with the results given by Whitehead and other literature. The blades were modeled as an equivalent 2-D section at 75% of span, and structural and inertial couplings were lumped into an effective CG-EA offset. Structural damping was included in the equations of motion. The resulting complex eigenvalue problem was solved recognizing the fact that there are two parameters in the eigenvalue problem, namely the reduced frequency k and the interblade phase angle β. The critical flutter speed was determined by minimizing it with respect to β, keeping the constraint on β as suggested by Lane. The solution provided the critical flutter speed with respect to both the torsion and the bending modes as a function of the interblade phase angle as well as dominant vibration frequencies at flutter. Various structural and aerodynamic parameters of the cascade were varied and the effect of the variations on the coupled bending torsion flutter was studied. A jump was observed in the flutter boundary near frequency ratio of 1, which was explained by the change in the mode shape of the vibration, which is represented by interblade phase angle. The developed technique can be used as a preliminary design tool for the aeroelastic flutter analysis of turbo-machinery blades. © Freund Publishing House Ltd.