EFFECT OF STACKING SEQUENCE ON THE PERFORMANCE OF GAS TURBINE CASING USING MODAL ANALYSIS

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 3, March 2018, pp , Article ID: IJMET_09_03_081 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EFFECT OF STACKING SEQUENCE ON THE PERFORMANCE OF GAS TURBINE CASING USING MODAL ANALYSIS Dr. S. Solomon Raj Assistant Professor, Department of Mechanical Engineering, Chaitanya Bharathi Institute of Technology, Hyderabad, India ABSTRACT: Gas turbine is a critical component used in many applications such as automotive, air-craft and spacecraft. Performance of a gas turbine depends on the weight of the casing and its vibration characteristics. Composites are promising materials now days which are finding applications in every field of engineering. In this work, an effort has been made to design gas turbine casing with composite materials so as to explore the advantages of them. Modal analysis is carried out for gas turbine casing made with conventional materials and composite materials with different stacking sequences. The results have shown that the casing made with composite material out performs the conventional casing when proper stacking sequence is selected. Keywords: gas turbine casing, stacking sequence, modal analysis Cite this Article: Dr. S. Solomon Raj, Effect of Stacking Sequence on the Performance of Gas Turbine Casing Using Modal Analysis, International Journal of Mechanical Engineering and Technology, 9(3), 2018, pp INTRODUCTION: Vibrations can be defined as mechanical oscillations of a system which is displaced from its position of equilibrium. Every object has a different response to excitations depending on material properties, geometry, and boundary conditions. For any material, it is convenient to describe the vibration response by considering three main parameters: amplitude, vibration mode shape and frequency. This work reports on the static mechanical and modal analysis by free vibration response of hybrid natural Fiber reinforced polymer composites. Modal analysis may predict the failure of structures prone to dynamic loading conditions. Solomon raj et.al [1, 2, 3, 4] explained the importance of the fiber orientation. He had studied on the effect of stacking sequence to improve the performance of a marine propeller. The study has shown that properly designed composite material can outperform the conventional materials. Composite materials have high-strength-to-weight and stiffness-to-weight ratios, which can lead to substantial weight savings editor@iaeme.com

2 Effect of Stacking Sequence on the Performance of Gas Turbine Casing Using Modal Analysis The orientation of the tailor fiber arrangement explained as +/- 45 degree plies give buckling stability and carry shear, 0 degree plies give column stability and carry tension or compression and 90 degree plies carry transverse loads and reduce Poisson s effects. Stephen W. Tsai has written a book Structural Behavior of Composite Materials, analyzed the structural behavior of the FRP composites. The experimental results show that the relations derived are more accurate than existing theories. This study is concerned with the analysis of the structural behavior of composite materials. It is shown that composite materials can be designed to produce a wide range of mechanical properties. Thus, a structural designer now has at his disposal an added dimension in optimum design - the materials optimization. Modal analysis is the study of the natural characteristics of structures, being often used to help designing parts for automotive, aircraft, spacecraft and even sports sector. Understanding both natural frequency and mode shape is important for noise and vibration applications and these characteristics can be estimated from measured frequency response functions using shaker or impulse hammer tests [4]. 2. RESULTS AND DISCUSSION 2.1. Steel The gas turbine casing is modeled with steel, having properties, E=200Gpa, ν=0.25, ρ=8gm/cc and Syt=448 Mpa. The first nine mode shapes obtained are shown in Fig 1. Mode:1 Mode:2 Mode: 3 Mode: 4 Mode: 5 Mode: 6 Mode: 7 Mode: 8 Mode: 9 Figure 1 First 9 mode shapes of steel gas turbine casing 2.2. Aluminum Similar to the above, the gas turbine casing with E=70Gpa, ν=0.3, ρ=2.7gm/cc and Syt=400 Mpa, is analyzed and the mode shapes obtained are presented in Fig editor@iaeme.com

3 Dr. S. Solomon Raj Mode:1 Mode:2 Mode:3 Mode:4 Mode:5 Mode:6 Mode:7 Mode:8 Mode:9 Figure 2 First 9 mode shapes of aluminum gas turbine casing The comparison of frequencies and maximum deflection associated with steel and aluminum are presented in Table 1. Table 1 Comparison between steel and Aluminum casing. Mode. No. Steel Aluminum Displacement (mm) Frequency (Hz) Displacement (mm) Frequency (Hz) COMPOSITE GAS TURBINE CASING To utilize the inherent advantages of composite materials glass/epoxy and carbon/epoxy are chosen for analysis. The lay-up sequences in the present study are taken as shown in Table 2. Glass/epoxy with stacking sequence1, is named as E1, sequence2 with E2 and sequence3 with E3. Same is done for carbon/epoxy material as C1, C2 and C editor@iaeme.com

4 Effect of Stacking Sequence on the Performance of Gas Turbine Casing Using Modal Analysis Table 2 Stacking sequences adopted S.No: Sequence 1 (90 0 /45 0 /0 0 /-45 0 /-90 0 )s 2 (60 0 /45 0 /0 0 /-45 0 /-60 0 )s 3 (45 0 /30 0 /0 0 /-30 0 /-45 0 )s Table 3 Properties of Composite Materials Glass/Epoxy Carbon/Epoxy Fiber Volume Fraction, Density ( ) (Mpa) 18,300 78,715, (Mpa) ,930 (Mpa) 3,895 2, (Mpa) (Mpa) (Mpa) (Mpa) (Mpa) The mode shapes for E1 are presented in Fig 3 and for composite casing made with C1 are presented in Fig 4. Mode:1 Mode:2 Mode:3 Mode:4 Mode:5 Mode:6 Mode:7 Mode:8 Mode:9 Figure 3 First 9 mode shapes of E1 gas turbine casing editor@iaeme.com

5 Dr. S. Solomon Raj Mode:1 Mode:2 Mode:3 Mode:4 Mode:4 Mode:6 Mode:7 Mode:8 Mode:9 Figure 4 First 9 mode shapes of C1 gas turbine casing Similarly, all the stacking sequences are analyzed and the results of which are as plotted below in Table 4 Natural frequency Maximum deflection Weight Material (Hz) (mm) (ton) Steel Aluminum E E E C C C editor@iaeme.com

6 weight (ton), max.deflection(mm)&natural frequency(hz) Effect of Stacking Sequence on the Performance of Gas Turbine Casing Using Modal Analysis St Al E1 E2 E3 C1 C2 C3 Material Natural frequency (Hz) Maximum deflection (mm) Weight (ton) Figure 5 Comparison of Natural frequency, Maximum deflection and weight of gas turbine casing with different materials 4. CONCLUSIONS: The modal analysis of a gas turbine casing is successfully carried out. The natural frequency as predicted numerically is higher for the casing made with carbon/epoxy sequence1. When compared to steel 81% of reduction in weight is achieved, which is a considerable amount. Higher natural frequency will even reduce the chances of resonance with the rotational speed of the rotor. For this application, though carbon/epoxy gives advantage with regard to weight, its natural frequency is found to be lesser than steel and aluminum. REFERENCES: [1] S.Solomon Raj, and P.Ravinder reddy, Effect of stacking sequence on the performance of a marine propeller, International Journal of applied engineering research, Vol.6, No.20, [2] S.Solomon Raj, P.Ravinder Reddy, Bend-twist coupling and its effect on cavitation inception of composite marine propeller, International Journal of mechanical engineering and technology, Vol.5, Issue 9, pp , [3] S.Solomon Raj, and P.Ravinder reddy. Performance evaluation of composite marine propeller using L8 orthogonal array, International Journal of engineering science and technology, Vol.3, No.11, November [4] S.Solomon Raj, and P.Ravinder reddy Utilization of Bend Twist Coupling to improve the Performance of Hybrid Marine Composite Propeller, International Journal of mechanical engineering and technology, Vol.9, Issue 3 march 2018, pp , [5] C Bennet, N Rajini, JT Winowlin Jappes, I Siva, V S Sreenivasan and SC Amico, Effect of the stacking sequence on vibrational behavior of Sansevieria cylindrica/coconut sheath polyester hybrid composites, Journal of Reinforced Plastics and Composites 2015, Vol. 34(4) [6] P.Kezia, B.L.N.Krishna Sai Analysis of Gas Turbine Blade Assembly to Evaluate the Performance of Various Nickel Based Alloys, International Journal of Mechanical Engineering and Technology, 8(5), 2017, pp [7] P.S. Jeyalaxmi and Dr.G.Kalivarathan, CFD Analysis of Turbulence in a Gas Turbine Combustor With Reference to the Context of Exit Phenomenon, International Journal of Advanced Research in Engineering and Technology (IJARET), Volume 4, Issue 2 March - April 2013, pp editor@iaeme.com