Classification of Diploma Thesis – opponent
Author of classification: Ing. Zbyněk Paška
Supervisor: doc. Ing. Jiří Podešva, Ph.D.
Opponents: Ing. Zbyněk Paška
Title: The Analysis of the Turbine Blade Fixture Crack
Thesis version: 1
Student: Dhanishkumar Loganadaneejil
1. Problematics of thesis
The thesis deals with the FEM analysis of the blade and its connection to the turbine rotor. The aim is to determine the location of a possible crack in the blade holder and to discuss the reasons for its occurrence. Furthermore, the loading effects acting on the turbine blade during operation are to be discussed.
2. Achieved results
At the beginning of the paper the reader is briefly introduced to the basic questions about rotating turbine machines. Their basic types are listed here. At the following chapters, the student briefly describes the basic components of the turbine. The student also introduces the basic types of turbine blade stresses and their causes (tensile stress, bending stress, blade vibration and thermal load). There are also basic methods of fixing the blades in the rotor body by means of grooves of various types, which are specified in more detail in the thesis. By weighing the blades, the position of their centre of gravity is determined and then the centrifugal force acting on the blade is calculated. The student creates a CAD model of the blade and its attachment, which is then used in the FEM simulation. The FEM method is briefly described in a separate chapter. This is followed by the FEM calculation with the specified boundary conditions and load conditions. The results are displacements in the
longitudinal axis of the blade and values of the HMH stress.
3. Originality of thesis
The student quotes the literature used in his work. A large part of the work can be considered
completely original. Chapters dealing with the theoretical basis and analysis of the subject of rotating machines are inspired by literature or online resources that the student cites.
4. Formal essentials of thesis
At the beginning of the work all necessary affidavits are listed. Here the task of the diploma thesis is specified. There is also a list and description of the pictures used. The content of the thesis is a matter of course. The thesis has some formal errors (e.g. 20rev / mm on page 9; unfinished sentence on page 17; unfinished caption on page 32).
5. Questions to student
1) When calculating the centrifugal force, assume that the entire mass of the blade is concentrated at the centre of gravity and rotates at a certain radius. This simplification is not discussed in this paper.
How would you briefly explain / justify this simplification?
2) What is the purpose of Figure 37 in the paper? I have not found any further comments in the text.
Can you comment it in more detail?
3) What kind of FEM elements are used in the analysis?
4) In this work you present different types and designs of blade attachment in the turbine rotor. Why was then only the type of T-shaped attachment analyzed?
6. General revaluation of thesis
The work is written in English. The student shows the ability to analyse complex technical problem.
At the beginning of the work the student describes the specific structural elements of the turbine. The student uses a large number of online resources, for which I miss to list a specific website with the date of citation. I miss the introduction of the basic material parameters in the chapter on FEM analysis. The graphical quality of some images could be better (e.g. fig. 7.20). There are several typing errors in the work, which unnecessarily reduce the quality of the work. I recommend the thesis for defense.
good Overall classification:
Ostrava, 07.08.2020 Ing. Zbyněk Paška
