CLIAMS:1. A method of designing a rotary machine blade, the method comprising:
a) providing an aerodynamically approved blade design;
b) selecting a first Hollow To Full Ratio (HFR) from a plurality of HFRs;
c) defining a design space region inside the blade for the selected HFR;
d) making a Finite Element model of the blade;
e) dividing the design space region into a pre-specified number of parts;
f) removing a first part from the design space;
g) performing a Finite Element analysis of the model;
h) checking if the model passes a predefined critical stress failure criterion;
- storing the blade design into a first set of blade designs, if the model passes the failure criterion;
- removing a next part adjacent to the first part and going to the step g, if the model passes the failure check and at least one part is remaining from the pre-specified number of parts;
- checking if a next HFR is available from the plurality of HFRs, if the model does not pass the failure check;
- selecting the next HFR and going to the step c, if the new HFR is available;
- going to step i, if the next HFR is not available;
i) performing a modal analysis for each of the blade design from the first set of blade designs;
j) storing the blade designs which pass the modal analysis into a second set of blade designs; and
k) selecting the blade design which is lightest in the second set of blade designs.

2. The method according to claim 1, wherein the HFR is size ratio between the design space dimension and the external blade dimensions at any cross section.

3. The method according to claim 1, wherein the design space region is scaled down version of the blade shape inside the blade.

4. The method according to claim 1, wherein a cross section of the design space region is scaled down replica of outer boundaries of the blade.

5. The method according to claim 1, wherein the design space region excludes small portions of solid sections of the blade near a root and a tip of the blade.

6. The method according to claim 5, wherein the small portion is five per cent of a length of the blade.

7. The method according to claim 1, wherein the removing of a first part starts from a region near a tip of the blade in the design space region and one by one the parts are removed in a direction towards a root of the blade.

8. The method according to claim 1, wherein during the modal analysis, first few natural frequencies are assessed with respect to an operating speed of the rotary machine and a first few harmonics.

9. The method according to claim 1, wherein the blade designs of the first set which do not show resonance pass the modal analysis.

10. The method according to claim 1, wherein the aerodynamically approved blade design remains same at outer surface throughout the method.
,TagSPECI:FIELD OF THE INVENTION

[001] The present invention relates in general todesign of rotating blades of steam and gas turbines and, more particularly to a method of designing blades with hollow sections for achieving lightweight blade configuration.

BACKGROUND OF THE INVENTION

[002] An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Normal aircraft engines are mostly gas turbines.Gas turbines are made up of multiple subassemblies, namely a fan, multi-stage compressors, a combustion chamber, and multi-stage turbines. Industrial and aircraft turbines consist of alternate stages of stationary and rotating stages of blades, often refereed as ‘guide blades’ and ‘rotary or running blades’.

[003] Turbine blades are the primary elements of gas turbines for converting heat energy into rotary energy. The blades have the cross-sectional profile of an airfoil such that, during operation, hot gas flows over the blade producing a pressure difference between the sides. Consequently, a force, which is directed from a pressure side towards a suction side, acts on the blade. The force generates torque on the main rotor shaft, which thereby rotates the rotor.

[004] For improving the efficiency and the working range of such gas turbines it is necessary to optimize all subsystems or components of the gas turbine. In the rotating stages of the blades, the thermal energy of the working fluid (gas or steam) gets converted into kinetic energy thereby rotating the blades. The surface geometries of the blades are crucial for getting optimal utilization of the available energy.

[005] A fully-coupled aerodynamic-structural iterative analysis can be useful for adaptive blade designs. Several iterations of the aerodynamic analysis followed by structural analyses are performed until a blade design is finalized.

[006] In one aspect of blade design, the surface geometries of the blades are arrived at for all the stages by using involved Computational Fluid Dynamics (CFD) computations. A second equally important aspect is that the blades have to meet strength and vibration criteria. The rotating blades are subjected to centrifugal forces resulting from angular velocity and pressure exerted by the working fluid. The maximum stress should not exceed the allowable value of the material.

[007] The computational fluid dynamic analysis mainly aims to increase aerodynamic efficiency through lift and drag forces. The structural analysis includes a prediction of deflection, state of stress, buckling load and fatigue life.

[008] The blades are also susceptible to high cycle fatigue failure. From a fatigue failure point of view it is necessary to avoid resonance of the fundamental modes with the operating speed and the first few harmonics (engine orders). There is a trade-off between aerodynamic efficiency (thin blades) and structural efficiency (thick blades), both of which have a strong effect on the cost of power generated. The design process therefore requires the optimum thickness distribution to be found, by finding the effect of varying thickness on both the power output and the structural weight.

[009] Normally the turbine blades are made of solid cross section. The rotating blades are not fully stressed to the limit throughout their volumes. Due to the action of centrifugal force, the stresses decrease from maximum at the root to near zero at the tip of the blade. Similar stress pattern is observed under the action of pressure load. In addition, under pressure loading, the bending stresses are highest on the extreme fibres (pressure and suction surfaces) and zero on neutral planes.

[0010] There have been instances of use of hollow cross section blades in the prior art. One of the motivations for resorting to hollow section blades is for providing cooling air passage. They are normally referred to air-cooled blades and find applications in first few power stages of gas turbines. Another reason for deviating from solid geometry is for reducing the mass. Lighter blades mean lesser centrifugal forces and consequently the blade supports get stressed to a lesser extent. Such blades, referred to as “hollow blades”, find applications in low pressure stages of steam and gas turbines where the blades are bigger and heavier.

[0011] The ability to vary the strength of the blade without changing the outside shape and making it hollow from inside gives the designers some freedom to optimise the design for minimum mass. Optimum geometry is arrived at iteratively by considering turbine design, loads, structural design, weight and manufacturing costs.

[0012] The designing of the turbine blade is an iterative process which involves aerodynamic design, strength analysis and free vibration modal analysis. The traditional blade designing process starts with first aerodynamically designing the blade by using Computational Fluid Dynamics (CFD), next the aerodynamic design blade is subjected to stress analysis. If the blade fails in stress analysis the aerodynamic design is again modified by using CFD. This goes on iteratively till the aerodynamic design which passes through the stress analysis is obtained. The stress safe aerodynamic design is then subjected to free vibration modal analysis, if the design fails then it is again sent for modification at the aerodynamic level. For the new aerodynamic design again the same process starts of stress analysis followed by the modal analysis starts until a design which passes through the stress and modal analysis is obtained. The iterative procedure to change at the aerodynamic design level after fail at stress or modal analysis test is a time consuming and costly step.

[0013] In view of the above mentioned limitations inherent in the present method of designing of hollow rotating blades, there exists a need for an improved method of designing rotating blades in an efficient, fast, flexible, cost effective, and environment friendly manner. The present invention addresses the issue of iterative approach of designing the rotating blades, using the concept of hollow section. The present invention fulfils this need and provides further advantages as described in the following summary.

SUMMARY OF THE INVENTION

[0014] In view of the foregoing disadvantages inherent in the prior arts, the general purpose of the present invention is to provide an improved combination of convenience and utility, to include the advantages of the prior art, and to overcome the drawbacks inherent therein.

[0015] Accordingly, it is an object of the present invention to provide a method of designing a hollow rotary machine blade.

[0016] In one aspect, the present invention provides a method of designing a rotary machine blade. The method comprises providing an aerodynamically approved blade design, selecting a first Hollow To Full Ratio (HFR) from a plurality of HFRs, defining a design space region inside the blade for the selected HFR, making a Finite Element model of the blade, dividing the design space region into a pre-specified number of parts, removing a first part, performing a Finite Element analysis of the model, checking if the model passes a predefined critical stress failure criterion, storing the blade design which pass the failure check into a first set of blade designs, removing a next part and repeating the above steps, if the model passes the failure check and at least one part is remaining from the pre-specified number of parts, repeating the above steps for a new Hollow To Full ratio, performing a modal analysis for each of the blade design from the first set of blade designs, storing the blade designs which pass the modal analysis into a second set of blade designs and selecting the blade design which is lightest in the second set of blade designs.

[0017] In another aspect of the present invention, the the hollow-to-full-ratio abbreviated as HFR is size ratio between the design space dimension and the external blade dimensions at any cross section.

[0018] In yet another aspect of the present invention, the design space region is scaled down version of the blade shape inside the blade.

[0019] In another aspect of the present invention, the design space region excludes small portions of solid sections of the blade near a root and a tip of the blade.

[0020] In a further aspect of the present invention, the removing of a first part starts from a region near a tip of the blade in the design space region and one by one the parts are removed in a direction towards a root of the blade.

[0021] In yet another aspect of the present invention, during the modal analysis, first few natural frequencies are assessed with respect to the operating speed of the rotary machine and its first few harmonics.

[0022] These together with other aspects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The advantages and features of the present invention will become better understood with reference to the following more detailed description taken in conjunction with the accompanying drawings in which:

[0024] FIG. 1 illustrates a typical rotary machine blade;

[0025] FIG. 2 illustrates a flowchart of the method of designing a rotary machine blade, according to one embodiment of the present invention;

[0026] FIG. 3 illustrates a sectional view of the blade showing the design space in the blade, according to one embodiment of the present invention;

[0027] FIG. 4 illustrates a sectional view of the blade showing the design space and non design space in the blade, according to one embodiment of the present invention;

[0028] FIG. 5 illustrates three different vertical cross sectional views of the blade during design iterations, according to one embodiment of the present invention;

[0029] FIG. 6 shows the results of stress analysis for different HFR values, according to one embodiment of the present invention;

[0030] FIG. 7 shows the variation in mass ratio of the blade as the layers are removed, according to one embodiment of the present invention;

[0031] FIG. 8 shows the variation in reaction force ratio of the blade as the layers are removed, according to one embodiment of the present invention;

[0032] FIG. 9 shows the results of modal analysis for HFR value 0.6, according to one embodiment of the present invention;

[0033] FIG. 10 shows the results of modal analysis for HFR value 0.7, according to one embodiment of the present invention; and

[0034] FIG. 11 shows the results of modal analysis for HFR value 0.8, according to one embodiment of the present invention.

[0035] Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

[0037] As used herein, the term ‘plurality’ refers to the presence of more than one of the referenced item and the terms ‘a’, ‘an’, and ‘at least’ do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0038] In an exemplary embodiment, the present invention provides a method of designing a rotary machine blade. The method of the present invention may be implemented in an easy, cost effective, environment friendly and productive way.

[0039] The terms ‘layers’ or ‘parts’ or ‘slices’ may be used herein interchangeably and refer to convey the same meaning. Similarly the terms ‘blade’ or ‘rotary machine blade’ or ‘turbo machinery blade’ may be used herein interchangeably and refer to convey the same meaning.

[0040] It is to be understood that the improvements of the present invention are applicable to any of a number of methods of designing a rotary machine blade, other than those which are specifically described below. Such methodswill be readily understood by the person of ordinary skill in the art, and are achievable by causing various changes that are themselves known in state of the art.

[0041] The trademarks, company names, etc used in the present description are property of the respective owner companies and used herein for illustrative purposes only. The applicant does not claim any rights on such terms.

[0042] Reference herein to “one embodiment” or “another embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

[0043] Referring to FIG. 1, that illustrates a typical rotary machine blade 10.The part of the blade connected to the rotor is called root or hub 12 of the blade and the other end of the blade is called tip 14 of the blade. The blade 10 includes a leading edge 16 and a trailing edge 18, along with the root 12, and the tip 14. The blade 10 has two surfaces called the suction surface 20 and a pressure surface 22 which are joined at the leading edge16 and the trailing edge 18.

[0044] Referring to FIG. 2 that illustrates a flowchart of the method 100 of designing a rotary machine blade, according to one embodiment of the present invention. The method 100 starts with step 110 of providing an aerodynamically approved blade design. The design is one of the final designs selected which has passed through various fluid tests such as computational fluid dynamics and finalized as per the aerodynamic criterion suited as per the requirements. One of the designs is taken as the starting design for the method 100 of the present invention. In one preferred embodiment of the present invention, the aerodynamic design is kept as it is and never disturbed during any step throughout the method 100 of the present invention. No changes are done on the outer surface of the blade design.

[0045] Now in step 115 a first Hollow To Full Ratio (HFR) from a plurality of HFRs is selected. In one embodiment the hollow-to-full-ratio abbreviated as HFR is size ratio between the design space dimension and the blade dimensions at any cross section. A list of HFRs is provided to be used in the method of the present invention, and one by one each of the HFR is used for designing the blade.

[0046] In next step 120 a design space region is defined inside the blade for the selected Hollow To Full Ratio. The design space dimensions are dependent on the HFR. In one embodiment the design space region is scaled down version of the blade shape inside the blade. The cross section of the design space region may be scaled down replica of outer boundaries of the blade.

[0047] FIG. 3 illustrates a sectional view of the blade showing the design space in the blade, according to one embodiment of the present invention. The inner volume is the design space and the outer volume is non design space that means the outer volume is never disturbed during the further steps of the method 100.

[0048] In one embodiment the design space region excludes small portions of solid sections of the blade near a root and a tip of the blade. In one preferred embodiment the small portion is five per cent of a length of the blade. The portions near the root 12 and tip 14 of the blade 10 are not included in design space as these have to meet functional needs. The bending moment is greatest at the root 12 of the blade than at any other point along the blade and at the tip the bending moment drops to zero. So it is intuitive that the blade must be thickest and strongest, at the root and can taper in thickness towards the tip where the bending moment is less. So during the whole design process these portions remain undisturbed i.e. no material is removed from these portions.

[0049] A Finite Element model of the blade is made in step 130. Standard Finite Element Analysis software such as ABAQUS, ANSYS, NASTRAN may be used for making the FE model of the blade.

[0050] Now in step 140 the design space region is divided into a pre-specified number of parts as shown in FIG.4. The parts may be referred as slices or layers. The design space may be divided into say ten layers. This number is also a design parameter.

[0051] A first part is removed from the design space in step 150. During design iterations the material of the part is removed. In one embodiment of the present invention, the removal of part starts from a region near the tip of the blade in the design space and one by one the parts are removed in a direction towards a root of the blade.

[0052] In step 160 a Finite Element analysis of the model is performed. The Finite Element analysis is carried out after removing the part, defining material properties, applying load and boundary conditions, including pressure, temperature, load, support etc. After the analysis the results are stored and visualized.

[0053] At step 170 the FE results are observed and it is checked if the model passes a predefined critical stress failure criterion. The failure criterion may be defined as the maximum stress at any point in the blade. If the maximum stress at any point crosses the allowable stress limit, and the blade design is considered as failed and dropped for further consideration. The allowable stress limit may depend on the material of the blade and the environment (for example temperature) to which it will be exposed during use.

[0054] The blade design which passes the failure check is stored into a first set of blade designs in step 180. The blade designs which pass the failure criterion for all combinations of available HFR and parts removed one by one are stored in the first set of blade design.

[0055] Now in step 190 a next part adjacent to the first part is removed and the control goes to step 160, if the model passes the failure check and at least one part is remaining from the pre-specified number of parts. The step 190 is repeated till all the parts are removed or till the maximum stress crosses the allowable limit and the design fails.

[0056] In step 195, it is checked if a next HFR is available from the plurality of HFRs, if the model does not pass the failure check. When the model fails in the critical stress failure criterion check in step 170, the availability of a next HFR from the list of HFRs is checked at step 195.

[0057] If any HFR is available in the list of HRfs, then that HFR is selected at step 200 and the control goes to step 120 of defining the design space again. The blade design process follows from step 120 for the new HFR.

[0058] If at step 195 next HFR is not available and when all the HFRs from the list of HFRs are used in the design process, the control goes to step 210.

[0059] Now in step 210 a modal analysis for each of the designs from the first set of blade designs is performed. In one embodiment of the present invention, during the modal analysis, first few natural frequencies are assessed with respect to an operating speed of the rotary machine and a first few harmonics. The modal analysis results are reviewed separately for each HFR value. Free vibration (modal) analysis is carried out for all the configurations satisfying the strength criterion. The first few natural frequencies are assessed with respect to the operating speed of the rotary machine where the blade would be used and the first few (consistent with the design practice) harmonics. The frequencies also need to be checked for any possible resonance with other drivers such as vane passing frequency.

[0060] In step 220 the designs which pass the modal analysis are stored into a second set of blade designs. In one embodiment of the present invention, the designs which do not show resonance pass the nodal analysis. All configurations which do not show dangerous resonances are acceptable designs. The second set of blade design includes designs which have passed through the stress failure criterion and also the nodal analysis criterions successfully.

[0061] In step 230 the design which is lightest in the second set of blade designs is selected as the final design. So finally the design obtained is aerodynamically approved, passed the stress failure criterion and the modal analysis and is the lightest.

[0062] In the hollow blade design thus obtained using the method 100, has hollow portion in the design space and is not visible from outside. It’s like a blind cavity in the blade.

[0063] An exemplary implementation of one embodiment of the method 100 of the present invention is carried out for the selection of the best blade design. As shown in FIG. 4 the blade 10 includes a design space and a non design space. An HFR is selected and as per the HFR the design space is defined. The inner volume called design space is shown split into a number of parts. Here the design space has ten layers. This number is also a design parameter. During design iterations the layers are removed successively one at a time starting from top. For a given HFR value the iterations proceed till all the layers are removed or till the maximum stress crosses the allowable limit. For the present case three HFR values are used here 0.6, 0,7 and 0.8. Starting with

[0064] Referring to FIG. 5 that illustrates three different vertical cross sectional views of the blade during design iterations. The left extreme 5(a) corresponds to the starting point with solid blade and full inner volume with no parts removed. The middle figure 5(b) corresponds to an intermediate design iteration stage, in which half of the layers are removed. The right extreme figure 5(c) corresponds to last iteration for a given value of HFR. As can be seen the inner volume is empty and all the layers are removed.

[0065] As one by one the layers are removed FE analysis of the blade is done for each layer removal and maximum stresses on the blade are obtained for each iteration.

[0066] Referring to FIG. 6 that shows the results of stress analysis for different HFR values. Ordinates refer to the maximum stress in the blade and the abscissa indicates the number of layers removed from the design space. Results are plotted for three values of HFR (0.6, 0.7 and 0.8). For the HFR=0.6 and 0.7, it can be seen that the stress values are below the allowable stress limit even if all ten layers are removed. This means that the blade can withstand full removal of the design space if the allowable stress is more than about 400 MPa. For HFR = 0.8 and for an assumed allowable value of 550 MPa, the stress values cross the allowable limit after seventh layer removal and the blade can meet strength requirements up to seven layer removal only. This means that the blade designs for HFR=0.6 and 0.7 all the designs from one layer removed to tenth layer removal are safe designs and are stored in the first set of blade designs. Similarly for blade with HFR = 0.8 the safe blade designs are the one where one to seven layer are removed. These also are stored in the first set of blade designs. The blade designs with HFR = 0.8 with more than seven layer removed failed the critical stress criterion and are unsafe designs.

[0067] In practice the FE analysis is stopped after the blade fails when a layer is removed and then a next blade design with another HFR is selected. One by one the layers are removed and at each layer removal stress analysis is done, if the blade design passes the failure criterion then next layer is removed, but if the blade fails then another HFR is selected and the process of removing layer one after another is repeated.

[0068] As the layers are removed the mass of the blade also decreases and this is also an important factor in the selection of the blade design. The Reaction force is also dependent on the mass of the blade and varies with the mass. FIG. 7 shows the variation in mass ratio of the blade as the layers are removed. The mass ratio of the blade is defined as the ratio of mass of the blade after layer removal divided by the original mass of solid blade. The mass ratio of the safe designs as per stress analysis criterion as stored in first set of blade designs are only plotted against number of layer removed for HFR values 0.6, 0.7 and 0.8.

[0069] In a similar graph FIG. 8 shows the variation in reaction force ratio of the blade as the layers are removed. The reaction force ratio of the blade is defined as the ratio of reaction force of blade after layer removal divided by the original reaction force of solid blade. The reaction force ratio of the safe designs as per stress analysis criterion as stored in first set of blade designs are only plotted against number of layer removed for HFR values 0.6, 0.7 and 0.8. Mass ratio and reaction force (radial force) are other two important parameters for the selection of bladed design. The ordinates in both the cases are non-dimensionalized with respect to the corresponding values of the full solid blade. These two graphs facilitate final selection subsequent to review of modal analysis results.

[0070] As it can be observed from the FIGs. 7 and 8 that as the layers are removed the mass ratio and the reaction force ratio decreases. Also as the HFR value increases the mass ratio and reaction force ratio of the blade for a particular number of layer removed decreases.

[0071] In order to optimise the design of rotary machine blades, many research studies have addressed the problems associated with the vibration behaviour of these components. The engine manufacturer’s main concern is to control the resonant response levels of the blades, and therefore the peak resonant stresses in the engine blades. This is one of the major problems in the design of blades since the vibration response of gas turbine blades that occur in practice is very sensitive to mistuning. When the inherent dissipation mechanisms are not sufficient (i.e. when the damping present is low), blade vibration amplitudes can reach higher than the acceptable levels.

[0072] Keeping the blades safe against vibration failure a free vibration or modal analyses is carried out for each ‘safe blade design’ from the first set of blade designs. Unlike stress analysis case, the modal analysis results are reviewed separately for each HFR value. The results for HFR=0.6 are presented in FIG. 9.

[0073] In FIG. 9 natural frequencies up to 1100 hertz are plotted against the number of layers removed from the blade with HFR = 0.6. The abscissa is same as for stress analysis results and the ordinates are drawn at 100 hertz intervals. For 6000 RPM (100 hertz) operation each horizontal line represents an engine order. The implication of the upper limit of 1100 hertz is that twelfth and higher engine orders are not important from a practical point of view. The lines identified as M1, M2 and M3 are the natural frequencies corresponding to Mode 1, Mode 2 and Mode 3 respectively. The intersection points between horizontal lines and frequency curves indicate resonance conditions which are to be avoided.

[0074] As can be observed from the figure, the second mode frequency with zero layers removed i.e. solid blade resonates with the 8th engine order (800 Hz), so this has to be avoided. Similarly the first mode M1 for two and three layers removed resonate with the 3rd engine order at 300 Hz. All such resonances are denoted by circles in the figure, and they have to be avoided. Only the designs with five, six and eight layers removed have no resonance, so these blade designs having HFR 0.6 are stored in second set of blade designs.

[0075] FIGs. 10 and 11 show similar graphs for HFR values of 0.7 and 0.8 respectively. As it can be observed from the FIG. 10 that only the designs with one, five and seven layers removed have no resonance, so these blade designs having HFR 0.7 are safe and stored in second set of blade designs.

[0076] Referring to FIG. 11 natural frequencies up to 1100 hertz are plotted against the number of layers removed from the blade with HFR = 0.8. Here unlike FIGs. 9 and 10, the maximum layers removed is up to seven only, since these were the safe designs as per stress failure criterion for HFR = 0.8. It can be observed that only the designs with four and six layers removed have no resonance, so these blade designs having HFR 0.8 are safe and stored in second set of blade designs.

[0077] Now from the second set of blade designs which have passed the stress and nodal analysis failure criterion, for each of the HFR values the accepted design with highest number of layers removed has to be picked. The reason is that the designs with higher number of layers removed are lighter for a given HFR.

[0078] For the sake of clarity let us designate the acceptable blade design with the number of layers removed for a given HFR by the number of layers removed. For example, for blade with HFR 0.6, the accepted designs are the designs with five, six and eight layers removed so let’s call the designs as D5, D6 and D8 respectively.

[0079] Similarly for HFR 0.7 the acceptable designs were D1, D5 and D7. For HFR 0.8 the acceptable designs were D4 and D6.

[0080] The highest numbered designs for HFR of 0.6, 0.7 and 0.8 are D8, D7 and D6 respectively. The corresponding mass ratios are 0.71, 0.74 and 0.77 and the reaction force ratios are 0.59, 0.59 and 0.61. Thus from mass and reaction force points of view the first of these three designs is the best. So with an HFR of 0.6 and eight layers removed design D8 is the best blade design and the blade will be lighter by 29 per cent. The reaction force is less by 41 per cent. This reduction in reaction force will facilitate lighter root design and thereby the blade as a whole can be made even lighter.

[0081] The method 100 of the present invention has the major advantage that the aerodynamic design of blade is never disturbed and the changes are done in the inner volume of the blade. This saves a lot of time and money in iterative design steps which were required in traditional design methods, in which after any failure in stress or modal analysis the aerodynamic design is again changed. The present method eliminates such iterations and prevents time and effort for designing the blade.

[0082] The blade design obtained from the method 100 of the present invention, has a blind cavity inside, so the additive manufacturing process may be more suitable and preferred. Additive manufacturing is the process of making a three-dimensional object from a 3D model or other electronic data source primarily through additive processes in which successive layers of material are laid down under computer control.

[0083] The method of the present invention may be implemented for the design of any blade of rotary machine such as gas turbine, engine etc. The method may be implemented as a software application either as a module to existing FEA software or as a standalone software for blade design. The method may also be implemented as a mobile application as or as a cloud based application.

[0084] In other instances, well-known components, methods, procedures, and steps have not been described herein, so as not to obscure the particular embodiments of the present invention. Further, various aspects of embodiments of the present invention may be made using various systems and methods.

[0085] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized to those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement of the components and stepsin the invention, variances in terms of steps may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as may fall within the spirit and scope of the present invention.

[0086] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions, substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but is intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.