- Email: [email protected]
Numerical and Experimental Study of Gas Turbine Rotor
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ScienceDirect Materials Today: Proceedings 4 (2017) 7942–7947
www.materialstoday.com/proceedings
ICAAMM-2016
NUMERICAL AND EXPERIMENTAL STUDY OF GAS TURBINE ROTOR Kalapala Prasad1, B.Anjaneya Prasad2, M.Anandarao3 1
Asst. Prof, Department of mechanical Engg , UCEK,JNTU KAKINADA, A.P, INDIA, 2 Prof., Department of mechanical Engg., JNTU HYDERABAD, A.P, INDIA 3 Professor, MLRIT, HYDERABAD, A.P, INDIA
Abstract This paper presents the results of experimental study of gas turbine rotor of Air craft, Marine, wind turbine rotor etc. The natural frequency of gas turbine rotor using Holzer’s method same are compared with the results that are obtained through a well known software based approach of FFT Analyzer. Rotors employed for transmitting motion are manufacturing using mild steel as it offers better stiffness and economical conditions under damping conditions. Mild steel as it resists tortional loads and bending loads more efficiency are more effectively. In this paper natural frequency of the gas turbine rotor predicted according to numerical results will be compared with experiential results. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility ofthe Committee Members of International Conference on Advancements in Aeromechanical Materials for Manufacturing (ICAAMM-2016). Keywords: Torsional stiffness, natural frequency, holzers method, mild steel rotor, FFT analyzer, damping ratio, logarithmic decrement.
Nomenclature = Natural frequency = Damping factor = Logarithmic decrement FFT = Fast fourier transform Xa = Minimum amplitude Xb = Maximum amplitude Kt = Tensional stiffens J = Mass moment of Inertia G = Shear modulus Ip = Polar moment of inertia L = Length M = Mass r = Radisu d = Diameter * Corresponding author. Tel.: +91 8970201660. E-mail address: [email protected]
2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility ofthe Committee Members of International Conference on Advancements in Aeromechanical Materials for Manufacturing (ICAAMM-2016).
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7943
1.
Introduction:
A rotor is a rotating machine element, which is used to transmit power from one component to other component. The power is delivered to the rotor by some tangential force and the resultant torque setup within the rotor permits the power to be transmitted to various machines linked up to the rotor. Mid steel is chosen as a material to lubricate rotor. It is a soft, ductile, malleable, tough, machinable, weldable material. Thye contain about 0.15-0.30% carbon. They are used for panels, fan, blades, gears, valves, camshafts, crankshafts, fish plates, ship plates, cross heads, tubes for bicycles and automobiles. The posses yield strength of 26 kg/mm2, ultimate stress of 56 kg/mm2 and an elongation of 23%. They are subjected to both bending and testing moments. Our design parameters include: mass of 1.4 kg, dia of 0.035m and a length of 0.6m. Natural frequencies of this rotor is determined by Holzers method using the calculated values of mass moment of inertia, torsional stiffness, polor moment of inertia by considering a three rotor system. Ogbonnaya EA, ugwa Hu, poku R, Adigo EM published in American journal of mechanical engineering 2013 vol 1 No 4 on active condition monitoring of a marine gas turbine through rotor shaft vibration analysis. They used high level java computer programming language. Shiyuzhou and Jianjanshi, university of Michigan, industrial and operating engineering Dept done vibration suppression of rotating machinery. In this paper, active vibration control for rotating machinery as well as research work on dynamic modeling and analytical techniques of rotor system is presented. 2.
Literature Survey:
1. “Investigation of shaft rotor using vibration, monitoring Technique for fault detection, Diagnosis and Analysis” Jaswinder Singh. Assistant professor in Mechanical Engineering, Punjab University.SSG Regional centre, Hoshiarpur, Punjab, India. This paper deals with a vibration signature measured at the external surface of rotating machinery or at any other suitable place contains a good amount of information to reveal the running condition of the machine. This paper involves design and fabrication of a rotor rig and investigations of vibrations at the bearings of the rig due to the effect of simulated faults. The line diagram of rotor test rig is also included in this paper. 2. A New Method of Calculating Natural Modes of Uncoupled Bending Vibration of Airplane Wings and Other Types of Beams N. 0. MYKLESTAD* California Institute of Technology. This paper deals with a particular advantage of the proposed method is that by plotting such curves. no frequencies will be overlooked. This is particularly important for the case of flexibly mounted engines, since many frequencies are then bunched together in a small region and for this case the proposed method is perhaps the only feasible one. 3. “Shaft crack detection in a steam turbine: experimental evidences and model-based simulations” P. Pennacchi, A. Vania Politecnico di Milano, Department of Mechanical Engineering Via La Masa, 1, I-20156, Milano, Italy email: [email protected]. This paper deals with the Fault symptom analysis techniques can be used to obtain an early detection of shaft cracks on the basis of the analysis of rotating machine vibrations. In this paper, the main results of the analysis of monitoring data collected. whose steam turbine was affected by a shaft crack propagation, are shown. Owing to the annular shape of this transverse crack, whose angular extension was 360°, the amplitude of the twice per revolution vibrations of the shaft. Finally, this paper shows the successful results obtained. 4. “State-of-the-art dynamic analysis for non-linear gas turbine structures” E P Petrov* and D J Ewins Centre of Vibration Engineering, Mechanical Engineering Department, Imperial College of Science, Technology and Medicine, London, UK. This paper deals with, an accurate and robust method has been developed for the general multi harmonic analysis of forced periodic vibrations of bladed discs subjected to abrupt changes of elastic and damping properties at contact nodes located on the interfaces of the components. The approach is based on an analytical formulation of friction contact interface elements which provides exact expressions for multi harmonic forces and stiffness matrices of the elements. 5.” Torsional vibration analysis of gear branched systems by finite element Method” deals the simple approach for eliminating the “dependent” torsional angles existing in the reduction gears of a gear-branched system so that this system may be modelled as an equivalent straight-geared system. The equations of motion of the whole vibrating
7944
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
system are defined. Solution of the equations of motion gives the dynamic responses and solution of the associated eigen value equation provides the natural frequencies and the modes shapes of the system. 6. Sato, Studies the cooling methods of gas turbine rotor. Air and liquid cooling are preferable. 7. Erratum, performed analysis of turbine rotor blade and calculated the natural frequencies and torsional stiffness values. 8. Tl-mastri, the film cooling effectiveness on low speed stationary cascade and rotating blade has been measured by using heat mass transfer analogy. The cooling effectiveness on sucta surface of blade fits well with that on stationary blade. 1.2 Theoritical analysis using holzers method: Given hub has following dimensions length, l = 0.6 m Rigidity modulus, G = 78Gpa = 78 x 109 N/M2 Polar moment of inertia, 4 ..........................(1) d 32
Ip
I p 1.47 10 7 m 4
Mass moment of inertia,
J
1 Mr 2 2
..........................(2)
J 2.14 10 4 Kg M 2 Torsional stiffness, Kt
G, I p
...................(3)
L
K t 19.11 10 2 N m
Considering Holzer’s method of finding Natural frequencies of rotor, take three rotor bars Torsional stiffness for each point will be half of the total value i.e., kt1, kt2 Mass moment of inertia is same for each rotor i.e., J1, J2, J3. Two definite frequencies in the three rotor system can be obtained from equation.
1 Kt Kt Kt 2 Kt 2 , 1 1 2 J 1 J2 J 3 2 1
2 2
2 Kt1 Kt1 Kt 2 Kt 2 4 Kt1 Kt 2 J 1 J 2 J 3 J2 J 3 J1 J 2 J 3 J1
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7945
Kt1 = Kt2 = 9.555 x103 J1 = J2 = J3 = 7.14 x 10-5 Now
(9.555 10 ) 1 (9.555 10 ) 12 , 22 5 2 (7.14 10 5 ) (7.14 10 ) 3 4
12 , 22
3 4
2 4(9555) 2 3 (7.14 10 5 ) (7.14 10 5 ) 3
1 (535.29 10 6 ) (2.86 1017 ) (2.15 1017 ) 2
1 2
12 (535.29 10 6 (7.110 6 ) )
12 134.42 106 1 11593.74rad / sec 1 11593.74 (0.159) HZ
1 1843.4 HZ Graph : 1-a Natural Frequency of a Rotor using FFT analyser:
Am plitu de (Mts )
Natural Frequency (HZ) The graph1-a represents the frequency response curve of gas turbine rotor using FFT analyser. The accelerometer readings are considered on Y-axis as it is a dependent variable, while on the other hand as the natural frequency values are being independent variables they are taken on X-axis. The first or peak amplitude is registered at 1885Hz as 60.60m/s2 .The graph remains constant between 720Hz – 1100Hz , while it undergoes decrement after reaching the first amplitude almost reaching a dead position. The second amplitude is followed successively after the first, with a range of about 60.599m/s2 at a frequency of around 690Hz.As the natural frequencies goes on increasing ,the
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Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
amplitude values reduces after certain critical conditions leading to dead position, indicating zero natural frequency in the gas turbine rotor. Boundary conditions for rotor are considered to be simply supported beam. Time vs accelerometer force:
A m pli tu de (
Time Period (Sec) Graph : 1-b Boundary Conditions for rotor are considered to be simply supported
The graph1-b is obtained from the FFT analyzer where the hammer force is on the x-axis and the acceleration is on the y-axis, the highest peak gives a reading of 60.66 m/s2. From the above graphical notation we can calculate the damping factor of the composite ( ζ ) by using the logarithmic decrement formula. The δ is nothing but the log of the amplitudes of two successive peaks here the two peaks are taken from graphs. From above graph Xa = 60.599 m/s2 Xb = 60.66 m/s2
log
60.66 60.59
4.369 *10 4 Dampingfactor
2 1
.......(4) 2
0.0695% Table: 1: Experimental Analysis Of Various Parameters Factors Affecting ωn ( natural frequency )
ζ ( DAMPING FACTOR ) δ ( logarithmic decrement value)
Theoretical Value
Experimental Value
Range
% Error
1843.4
1885
41.6
2.26
0.000116
0.000114
0.000002
7.38 x 10-6
9.7.17 x 10-6
0.19 x 10-6
1.724
2.024
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7947
3.
Results and discussions:
An illustration of Theoretical as well as Experimental analysis of various parameters such as natural frequency, damping ratio and logarithmic decrements is represented in the above table.1. Theoretical frequency calculated using Holzer’s method is obtained as1843.4Hz ,while the frequency obtained through FFT analyser is noted as 1885Hz.So both of these theoretical and experimental values differ by a range of 41.6Hz ,which results in an error percent of 2.26. Similarly Damping factors for Theoretical and Experimental approaches are registered as 0.000116 and 0.000114 leading to an error percent of 1.724.The final values of logarithmic decrement are obtained to be 7.38×10-6 and 7.17×10-6 for theoretical and experimental analysis respectively, resulting in an error percent of 2.024 with a range of 0.19×10-6 . The software DEWE we have used in FFT analyser proves more reliable compared to others. A clear as well as reduced values of natural frequencies indicate the effectiveness of mild steel over other materials like Aluminium, Titanium etc., which have less ductility, high economical cost than our material. Holzers method adopted by us is an accurate ,fast and efficient approach to obtain the natural frequencies over others as like Differential transform method so on. As we can infer that the obtained value does not match the design value the effect of resonance can be neglected. 4.
Conclusion:
In this paper deals with obtaining the gas turbine rotor parameters like natural frequency, torsional stiffness, damping ratio and logarithmic decrement values by adopting a Holzer’s method and values were determined accurately by comparing the theoretical values with obtained practical values through the experimental analysis of fast fourier transform spectrum (FFT) analyzer. The geometrical analysis results are compared with investigational results were experiential with an error percentage of 2.26. it results in reduced torisonal vibrations. Mild steel shaft exhibits good strength, ductility, low cost. Efficiency of the gas turbine improves as it reduced vibrations due to rotation of shaft. The obtained results guides us for implementing good optimization techniques. Additional research work has to be conduct to measure the natural frequency of modified materials with different rotor materials like high carbon steel, super alloy. References [1].Jaswinder Singh, “Investigation of shaft rotor system using vibration monitoring technique for fault detection diagnosis and analysis”, Mechnaica confab, Vo.2, 2013. [2].Myklestad, “A new method of calculating natural modes of uncoupled bending vibration of airplane wings”, Research Gate, Vol.3, 2014 PP 20-30. [3].Pennachi, “Shaft crack detection in a steam turbine experimental evidence and simulation”, Isma proceedings, 2010, pp 30-46. [4].DJEWINS & EP PETROR, “State of art dynamic analysis for non linear gas turbine structure” Proceeding institute of Mech Engineers, Vol. 218, 2004. [5].C.H.CHEN, “Torsional vibration analysis of Gear branched system by finite element method”, science direct journal of sound and vibration, 2001, Vol. 240, pp 159-182. [6].T Sato, “Film cooling on a gas turbine rotor blade”, ASME, Vol 2, 2008. [7].Erratum, “Vibration analysis of gas turbine rotor blade”, ASMF, Vol 3, 2006. [8].El Masrin, “Rotor blade manufacturing techniques” ASME, 2008, PP 880-889.
ScienceDirect Materials Today: Proceedings 4 (2017) 7942–7947
www.materialstoday.com/proceedings
ICAAMM-2016
NUMERICAL AND EXPERIMENTAL STUDY OF GAS TURBINE ROTOR Kalapala Prasad1, B.Anjaneya Prasad2, M.Anandarao3 1
Asst. Prof, Department of mechanical Engg , UCEK,JNTU KAKINADA, A.P, INDIA, 2 Prof., Department of mechanical Engg., JNTU HYDERABAD, A.P, INDIA 3 Professor, MLRIT, HYDERABAD, A.P, INDIA
Abstract This paper presents the results of experimental study of gas turbine rotor of Air craft, Marine, wind turbine rotor etc. The natural frequency of gas turbine rotor using Holzer’s method same are compared with the results that are obtained through a well known software based approach of FFT Analyzer. Rotors employed for transmitting motion are manufacturing using mild steel as it offers better stiffness and economical conditions under damping conditions. Mild steel as it resists tortional loads and bending loads more efficiency are more effectively. In this paper natural frequency of the gas turbine rotor predicted according to numerical results will be compared with experiential results. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility ofthe Committee Members of International Conference on Advancements in Aeromechanical Materials for Manufacturing (ICAAMM-2016). Keywords: Torsional stiffness, natural frequency, holzers method, mild steel rotor, FFT analyzer, damping ratio, logarithmic decrement.
Nomenclature = Natural frequency = Damping factor = Logarithmic decrement FFT = Fast fourier transform Xa = Minimum amplitude Xb = Maximum amplitude Kt = Tensional stiffens J = Mass moment of Inertia G = Shear modulus Ip = Polar moment of inertia L = Length M = Mass r = Radisu d = Diameter * Corresponding author. Tel.: +91 8970201660. E-mail address: [email protected]
2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility ofthe Committee Members of International Conference on Advancements in Aeromechanical Materials for Manufacturing (ICAAMM-2016).
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7943
1.
Introduction:
A rotor is a rotating machine element, which is used to transmit power from one component to other component. The power is delivered to the rotor by some tangential force and the resultant torque setup within the rotor permits the power to be transmitted to various machines linked up to the rotor. Mid steel is chosen as a material to lubricate rotor. It is a soft, ductile, malleable, tough, machinable, weldable material. Thye contain about 0.15-0.30% carbon. They are used for panels, fan, blades, gears, valves, camshafts, crankshafts, fish plates, ship plates, cross heads, tubes for bicycles and automobiles. The posses yield strength of 26 kg/mm2, ultimate stress of 56 kg/mm2 and an elongation of 23%. They are subjected to both bending and testing moments. Our design parameters include: mass of 1.4 kg, dia of 0.035m and a length of 0.6m. Natural frequencies of this rotor is determined by Holzers method using the calculated values of mass moment of inertia, torsional stiffness, polor moment of inertia by considering a three rotor system. Ogbonnaya EA, ugwa Hu, poku R, Adigo EM published in American journal of mechanical engineering 2013 vol 1 No 4 on active condition monitoring of a marine gas turbine through rotor shaft vibration analysis. They used high level java computer programming language. Shiyuzhou and Jianjanshi, university of Michigan, industrial and operating engineering Dept done vibration suppression of rotating machinery. In this paper, active vibration control for rotating machinery as well as research work on dynamic modeling and analytical techniques of rotor system is presented. 2.
Literature Survey:
1. “Investigation of shaft rotor using vibration, monitoring Technique for fault detection, Diagnosis and Analysis” Jaswinder Singh. Assistant professor in Mechanical Engineering, Punjab University.SSG Regional centre, Hoshiarpur, Punjab, India. This paper deals with a vibration signature measured at the external surface of rotating machinery or at any other suitable place contains a good amount of information to reveal the running condition of the machine. This paper involves design and fabrication of a rotor rig and investigations of vibrations at the bearings of the rig due to the effect of simulated faults. The line diagram of rotor test rig is also included in this paper. 2. A New Method of Calculating Natural Modes of Uncoupled Bending Vibration of Airplane Wings and Other Types of Beams N. 0. MYKLESTAD* California Institute of Technology. This paper deals with a particular advantage of the proposed method is that by plotting such curves. no frequencies will be overlooked. This is particularly important for the case of flexibly mounted engines, since many frequencies are then bunched together in a small region and for this case the proposed method is perhaps the only feasible one. 3. “Shaft crack detection in a steam turbine: experimental evidences and model-based simulations” P. Pennacchi, A. Vania Politecnico di Milano, Department of Mechanical Engineering Via La Masa, 1, I-20156, Milano, Italy email: [email protected]. This paper deals with the Fault symptom analysis techniques can be used to obtain an early detection of shaft cracks on the basis of the analysis of rotating machine vibrations. In this paper, the main results of the analysis of monitoring data collected. whose steam turbine was affected by a shaft crack propagation, are shown. Owing to the annular shape of this transverse crack, whose angular extension was 360°, the amplitude of the twice per revolution vibrations of the shaft. Finally, this paper shows the successful results obtained. 4. “State-of-the-art dynamic analysis for non-linear gas turbine structures” E P Petrov* and D J Ewins Centre of Vibration Engineering, Mechanical Engineering Department, Imperial College of Science, Technology and Medicine, London, UK. This paper deals with, an accurate and robust method has been developed for the general multi harmonic analysis of forced periodic vibrations of bladed discs subjected to abrupt changes of elastic and damping properties at contact nodes located on the interfaces of the components. The approach is based on an analytical formulation of friction contact interface elements which provides exact expressions for multi harmonic forces and stiffness matrices of the elements. 5.” Torsional vibration analysis of gear branched systems by finite element Method” deals the simple approach for eliminating the “dependent” torsional angles existing in the reduction gears of a gear-branched system so that this system may be modelled as an equivalent straight-geared system. The equations of motion of the whole vibrating
7944
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
system are defined. Solution of the equations of motion gives the dynamic responses and solution of the associated eigen value equation provides the natural frequencies and the modes shapes of the system. 6. Sato, Studies the cooling methods of gas turbine rotor. Air and liquid cooling are preferable. 7. Erratum, performed analysis of turbine rotor blade and calculated the natural frequencies and torsional stiffness values. 8. Tl-mastri, the film cooling effectiveness on low speed stationary cascade and rotating blade has been measured by using heat mass transfer analogy. The cooling effectiveness on sucta surface of blade fits well with that on stationary blade. 1.2 Theoritical analysis using holzers method: Given hub has following dimensions length, l = 0.6 m Rigidity modulus, G = 78Gpa = 78 x 109 N/M2 Polar moment of inertia, 4 ..........................(1) d 32
Ip
I p 1.47 10 7 m 4
Mass moment of inertia,
J
1 Mr 2 2
..........................(2)
J 2.14 10 4 Kg M 2 Torsional stiffness, Kt
G, I p
...................(3)
L
K t 19.11 10 2 N m
Considering Holzer’s method of finding Natural frequencies of rotor, take three rotor bars Torsional stiffness for each point will be half of the total value i.e., kt1, kt2 Mass moment of inertia is same for each rotor i.e., J1, J2, J3. Two definite frequencies in the three rotor system can be obtained from equation.
1 Kt Kt Kt 2 Kt 2 , 1 1 2 J 1 J2 J 3 2 1
2 2
2 Kt1 Kt1 Kt 2 Kt 2 4 Kt1 Kt 2 J 1 J 2 J 3 J2 J 3 J1 J 2 J 3 J1
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7945
Kt1 = Kt2 = 9.555 x103 J1 = J2 = J3 = 7.14 x 10-5 Now
(9.555 10 ) 1 (9.555 10 ) 12 , 22 5 2 (7.14 10 5 ) (7.14 10 ) 3 4
12 , 22
3 4
2 4(9555) 2 3 (7.14 10 5 ) (7.14 10 5 ) 3
1 (535.29 10 6 ) (2.86 1017 ) (2.15 1017 ) 2
1 2
12 (535.29 10 6 (7.110 6 ) )
12 134.42 106 1 11593.74rad / sec 1 11593.74 (0.159) HZ
1 1843.4 HZ Graph : 1-a Natural Frequency of a Rotor using FFT analyser:
Am plitu de (Mts )
Natural Frequency (HZ) The graph1-a represents the frequency response curve of gas turbine rotor using FFT analyser. The accelerometer readings are considered on Y-axis as it is a dependent variable, while on the other hand as the natural frequency values are being independent variables they are taken on X-axis. The first or peak amplitude is registered at 1885Hz as 60.60m/s2 .The graph remains constant between 720Hz – 1100Hz , while it undergoes decrement after reaching the first amplitude almost reaching a dead position. The second amplitude is followed successively after the first, with a range of about 60.599m/s2 at a frequency of around 690Hz.As the natural frequencies goes on increasing ,the
7946
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
amplitude values reduces after certain critical conditions leading to dead position, indicating zero natural frequency in the gas turbine rotor. Boundary conditions for rotor are considered to be simply supported beam. Time vs accelerometer force:
A m pli tu de (
Time Period (Sec) Graph : 1-b Boundary Conditions for rotor are considered to be simply supported
The graph1-b is obtained from the FFT analyzer where the hammer force is on the x-axis and the acceleration is on the y-axis, the highest peak gives a reading of 60.66 m/s2. From the above graphical notation we can calculate the damping factor of the composite ( ζ ) by using the logarithmic decrement formula. The δ is nothing but the log of the amplitudes of two successive peaks here the two peaks are taken from graphs. From above graph Xa = 60.599 m/s2 Xb = 60.66 m/s2
log
60.66 60.59
4.369 *10 4 Dampingfactor
2 1
.......(4) 2
0.0695% Table: 1: Experimental Analysis Of Various Parameters Factors Affecting ωn ( natural frequency )
ζ ( DAMPING FACTOR ) δ ( logarithmic decrement value)
Theoretical Value
Experimental Value
Range
% Error
1843.4
1885
41.6
2.26
0.000116
0.000114
0.000002
7.38 x 10-6
9.7.17 x 10-6
0.19 x 10-6
1.724
2.024
Kalapala Prasad / Materials Today: Proceedings 4 (2017) 7942–7947
7947
3.
Results and discussions:
An illustration of Theoretical as well as Experimental analysis of various parameters such as natural frequency, damping ratio and logarithmic decrements is represented in the above table.1. Theoretical frequency calculated using Holzer’s method is obtained as1843.4Hz ,while the frequency obtained through FFT analyser is noted as 1885Hz.So both of these theoretical and experimental values differ by a range of 41.6Hz ,which results in an error percent of 2.26. Similarly Damping factors for Theoretical and Experimental approaches are registered as 0.000116 and 0.000114 leading to an error percent of 1.724.The final values of logarithmic decrement are obtained to be 7.38×10-6 and 7.17×10-6 for theoretical and experimental analysis respectively, resulting in an error percent of 2.024 with a range of 0.19×10-6 . The software DEWE we have used in FFT analyser proves more reliable compared to others. A clear as well as reduced values of natural frequencies indicate the effectiveness of mild steel over other materials like Aluminium, Titanium etc., which have less ductility, high economical cost than our material. Holzers method adopted by us is an accurate ,fast and efficient approach to obtain the natural frequencies over others as like Differential transform method so on. As we can infer that the obtained value does not match the design value the effect of resonance can be neglected. 4.
Conclusion:
In this paper deals with obtaining the gas turbine rotor parameters like natural frequency, torsional stiffness, damping ratio and logarithmic decrement values by adopting a Holzer’s method and values were determined accurately by comparing the theoretical values with obtained practical values through the experimental analysis of fast fourier transform spectrum (FFT) analyzer. The geometrical analysis results are compared with investigational results were experiential with an error percentage of 2.26. it results in reduced torisonal vibrations. Mild steel shaft exhibits good strength, ductility, low cost. Efficiency of the gas turbine improves as it reduced vibrations due to rotation of shaft. The obtained results guides us for implementing good optimization techniques. Additional research work has to be conduct to measure the natural frequency of modified materials with different rotor materials like high carbon steel, super alloy. References [1].Jaswinder Singh, “Investigation of shaft rotor system using vibration monitoring technique for fault detection diagnosis and analysis”, Mechnaica confab, Vo.2, 2013. [2].Myklestad, “A new method of calculating natural modes of uncoupled bending vibration of airplane wings”, Research Gate, Vol.3, 2014 PP 20-30. [3].Pennachi, “Shaft crack detection in a steam turbine experimental evidence and simulation”, Isma proceedings, 2010, pp 30-46. [4].DJEWINS & EP PETROR, “State of art dynamic analysis for non linear gas turbine structure” Proceeding institute of Mech Engineers, Vol. 218, 2004. [5].C.H.CHEN, “Torsional vibration analysis of Gear branched system by finite element method”, science direct journal of sound and vibration, 2001, Vol. 240, pp 159-182. [6].T Sato, “Film cooling on a gas turbine rotor blade”, ASME, Vol 2, 2008. [7].Erratum, “Vibration analysis of gas turbine rotor blade”, ASMF, Vol 3, 2006. [8].El Masrin, “Rotor blade manufacturing techniques” ASME, 2008, PP 880-889.