scholarly journals Influence of furnace tube shapeon thermal strain of fire-tube boilers

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 39-47 ◽  
Author(s):  
Branka Gacesa ◽  
Tasko Maneski ◽  
Vesna Milosevic-Mitic ◽  
Miodrag Nestorovic ◽  
Ana Petrovic
Keyword(s):  
Numerical Analysis ◽  
Lower Order ◽  
Thermal Stresses ◽  
Thermal Strain ◽  
Strength Analysis ◽  
Maximal Stress ◽  
Furnace Tube ◽  
Tube Shape ◽  
Different Shapes ◽  
Real Operating Condition

The aim of this paper is to use numerical analysis and fine element method-FEM to investigate the influence of furnace tube shape on the thermal strain of fire-tube boilers. Thermal stresses in corrugated furnace tubes of different shape, i.e. with different corrugation pitch and depth, were analysed first. It was demonstrated that the thermal stresses in corrugated furnace tube are significantly reduced with the increase of corrugation depth. Than deformations and stresses in the structure of a fire-tube boiler were analysed in a real operating condition, for the cases of installed plain furnace tube and corrugated furnace tubes with different shapes. It was concluded that in this fire-tube boiler, which is of larger steam capacity, the corrugated furnace tube must be installed, as well as that the maximal stress in the construction is reduced by the installation of the furnace tube with greater corrugation depth. The analysis of stresses due to pressure and thermal loads pointed out that thermal stresses are not lower-order stresses in comparison to stresses due to pressure loads, so they must be taken into consideration for boiler strength analysis.

Numerical Analysis of Non-Radial Blading in a Low Speed and Low Pressure Turbine for Electric Turbocompounding Applications

2021 ◽  
Author(s):  
Eva Alvarez-Regueiro ◽  
Esperanza Barrera-Medrano ◽  
Ricardo Martinez-Botas ◽  
Srithar Rajoo
Keyword(s):  
Numerical Analysis ◽  
Numerical Simulations ◽  
Thermal Stresses ◽  
Waste Heat ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Blade Angle ◽  
Low Speed

Abstract This paper presents a CFD-based numerical analysis on the potential benefits of non-radial blading turbine for low speed-low pressure applications. Electric turbocompounding is a waste heat recovery technology consisting of a turbine coupled to a generator that transforms the energy left over in the engine exhaust gases, which is typically found at low pressure, into electricity. Turbines designed to operate at low specific speed are ideal for these applications since the peak efficiency occurs at lower pressure ratios than conventional high speed turbines. The baseline design consisted of a vaneless radial fibre turbine, operating at 1.2 pressure ratio and 28,000rpm. Experimental low temperature tests were carried out with the baseline radial blading turbine at nominal, lower and higher pressure ratio operating conditions to validate numerical simulations. The baseline turbine incidence angle effect was studied and positive inlet blade angle impact was assessed in the current paper. Four different turbine rotor designs of 20, 30, 40 and 50° of positive inlet blade angle are presented, with the aim to reduce the losses associated to positive incidence, specially at midspan. The volute domain was included in all CFD calculations to take into account the volute-rotor interactions. The results obtained from numerical simulations of the modified designs were compared with those from the baseline turbine rotor at design and off-design conditions. Total-to-static efficiency improved in all the non-radial blading designs at all operating points considered, by maximum of 1.5% at design conditions and 5% at off-design conditions, particularly at low pressure ratio. As non-radial fibre blading may be susceptible to high centrifugal and thermal stresses, a structural analysis was performed to assess the feasibility of each design. Most of non-radial blading designs showed acceptable levels of stress and deformation.

Thermal Stress in Teeth

1978 ◽  
Vol 57 (4) ◽  
pp. 571-582 ◽  
Author(s):  
B.A. Lloyd ◽  
M.B. McGinley ◽  
W.S. Brown
Keyword(s):  
Thermal Stress ◽  
Numerical Analysis ◽  
Material Properties ◽  
Thermal Stresses ◽  
In Vivo Studies ◽  
Tooth Structure ◽  
Analysis Techniques ◽  
Tooth Type

Observations of crack damage in the tooth structure from in vivo studies and in vitro experimental thermal cycling studies were combined with numerical analysis techniques to identify and isolate the influence of thermal stresses an the creation and propagation of cracks in teeth. The factors considered in this study included: (a) variations in tooth type or geometry (molar, bicuspid, etc.), (b) tooth age, (c) material properties of the tooth, (d) the magnitude of the change in the temperature of the environment surrounding the tooth, and (e) the thermal resistance between the tooth and the medium surrounding the tooth.

scholarly journals Damage Identification of Plate Structure Based on the Method of Modal Flexibility Curvature Difference

2019 ◽  
Vol 256 ◽  
pp. 02015
Author(s):  
Jiangang Zhao ◽  
Yuxiang Zhang ◽  
Jiazhao Chen
Keyword(s):  
Numerical Analysis ◽  
Lower Order ◽  
Damage Identification ◽  
Higher Order ◽  
Plate Structure ◽  
First Order ◽  
Flexibility Matrix ◽  
Damage Degree ◽  
Higher Order Modes ◽  
Modal Flexibility

According to the higher order modes of the structure are difficult to extract and the lower order are easy to obtain in practice, it is put forward that only uses the parameters of lower or first-order modal to constitute the modal flexibility curvature difference (MFCD) as the index of damage identification, which based on the flexibility matrix of structure being sensitive to the structure modal characteristics. Numerical analysis is made on different damage conditions of a plate structure, and the result shows that the MFCD can not only accurately identify the single-damage and multi-damage position of plate structure, but also reflect the size of damage degree. It has a great significance to apply the index into the range of damage identification of actual structures.

Dimensional Study for Brazilian FPSO

2005 ◽  
Author(s):  
Daniel Cueva ◽  
Marcos Donato ◽  
Fernando Torres ◽  
Felipe Campos ◽  
Jose A. Ferrari ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Environmental Conditions ◽  
Weather Conditions ◽  
Roll Motion ◽  
Scaled Model ◽  
Campos Basin ◽  
Real Behavior ◽  
Wind Characteristics ◽  
Different Shapes ◽  
Cooperative Project

After the boom of converted floating, production, storage and offloading systems, based on the old VLCC design, many engineering institutes started thinking about optimum dimension for new units. However, these new FPSOs designs carried out worldwide concerns about good seakeeping behavior when considering general weather conditions, in order to apply their project to different locations around the globe. Analyzing the Brazilian specific conditions, it was verified that, considering waves, current and wind characteristics, the dimension proportions found in the projected units were not the best options, mostly because of the swell waves influence. Thus, in a cooperative project between University of Sao Paulo and PETROBRAS, the best dimensions for a specific case were studied, based on real premises from Campos Basin. During the study, the roll motion, which usually creates operational limits during hard environmental conditions, was focused. It was possible not only to evaluate the best breath and draught relations, but also the inclusion of a structured skirt in the ship bilge. The influence of different shapes in the ship’s bow and stern were also evaluated, showing interesting results regarding the forces applied on the vessel. All the analyses were conducted considering numerical analysis, and the final dimensions were applied to a scaled model, which allowed to verify the real behavior of the projected unit in a test basin. As a conclusion, it was possible to define an optimized hull for the PETROBRAS premises, giving them a real design to be used in future explorations.

INTEGRITY ASSESSMENT OF THICK WALLED INDUSTRIAL FURNACE TUBES

1993 ◽  
Vol 17 (2) ◽  
pp. 127-143
Author(s):  
R.K. Kizhatil ◽  
R. Seshadri
Keyword(s):  
Thermal Stresses ◽  
Furnace Operation ◽  
Remaining Life ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Firing Rates ◽  
Linear Finite Element ◽  
Core Method ◽  
Furnace Tube ◽  
Integrity Assessments

This paper examines various simplified methods proposed to analyze stresses and predict damage and remaining life in furnace tubes subjected to sustained primary pressure stresses and cyclic secondary thermal stresses resulting from a typical furnace operation. Operational effects such as tube fouling, firing rates, startup-shutdown cycles are considered. Component integrity assessments are carried out using some recently developed techniques. A numerical example of a furnace tube made of HK-40 material is presented, and results obtained using a non-linear finite element analysis are compared with predictions obtained using the elastic-core method.

Thermal Strain-Tolerant Abradable Thermal Barrier Coatings

1992 ◽  
Vol 114 (2) ◽  
pp. 264-267 ◽  
Author(s):  
T. E. Strangman
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Stresses ◽  
Spray Deposition ◽  
Thermal Strain ◽  
Engine Performance ◽  
Thermal Barrier ◽  
Free Expansion ◽  
Barrier Coatings ◽  
Turbine Component ◽  
Cooling Air

Thermal barrier coatings (TBCs) are applied to hot gas path surfaces to reduce metal temperatures and thermal stresses for improved turbine component durability. Improvements in engine performance are achieved when TBCs enable reductions in cooling air usage and turbine blade tip-shroud clearances. This paper describes the development of thick TBCs with superior strain tolerance. A pattern of grooves or slant steps incorporated into the surface to be coated enables the development of shadow gaps in the ceramic layer during plasma spray deposition. These gaps segment the TBC, permitting ceramic-metal thermal expansion mismatch and thermal strains to be accommodated by free expansion.

scholarly journals Finite Element Fatigue Analysis of Unsupported Crane

2021 ◽  
Vol 28 (1) ◽  
pp. 127-135
Author(s):  
Ryszard Buczkowski ◽  
Bartłomiej Żyliński
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Fatigue Analysis ◽  
Strength Analysis ◽  
Marine Structures ◽  
Element Analysis ◽  
Static Loads ◽  
The Finite Element Analysis ◽  
Sufficient Degree ◽  
Number Of Cycles

Abstract The presented strength and fatigue calculations refer to an unsupported deck crane and its three distinct parts: housing, jib and column. Static loads applied to the structure were due to the crane’s own weight and a maximum working load, corresponding to a maximum lifting capacity at a maximum outreach of the crane. The numerical analysis was aimed at determining the thickness of the skin plating of the column and the number, shape and distribution of stiffeners in the column, housing and jib, ensuring that the crane yields correct strength and fatigue parameters. During the process of designing marine structures, the standard numerical analysis is, in many cases, limited to calculations in the basic strength range. Even when using numerical methods of analysis, complex strength and fatigue calculations are often not performed. The modern numerical analysis chain for marine structures should concentrate not only on strength analysis, but should take a further step, which encompasses fatigue analysis. The article presents a new outlook on design methods, which should be the entry point to the design of marine structures. Based on the acquired number of cycles of fatigue life, it is possible to estimate, with a sufficient degree of accuracy, the practical service life of a structure. To solve the problem, the authors used the finite element analysis software ABAQUS supported by the fe-safe system.

Thermal and Electromigration Strain Distributions in 10 μm-Wide Aluminum Conductor Lines Measured by X-Ray Microdiffraction

1997 ◽  
Vol 473 ◽  
Author(s):  
P.-C. Wang ◽  
G. S. Cargill ◽  
I. C. Noyan ◽  
E. G. Liniger ◽  
C.-K. Hu ◽  
...  
Keyword(s):  
Thermal Stresses ◽  
Stress Gradient ◽  
Thermal Strain ◽  
Sample Surface ◽  
X Rays ◽  
Strain Measurements ◽  
X Ray ◽  
Glass Capillaries ◽  
Reflection Geometry ◽  
Made In

ABSTRACTX-ray microdiffraction was applied to study the thermal and electromigration strains in 10 μm-wide Al conductor lines with 10 μm spatial resolution. X-rays were collimated either by pinholes or by tapered glass capillaries to form x-ray microbeams. Measurements were made in a symmetric-reflection geometry so that the strains normal to the sample surface could be examined at different positions along the conductor lines. Results of thermal strain measurements show that the SiO2 passivation plays an important role in limiting relaxation of in-plane compressive thermal stresses in the Al lines, but that the passivation is not effective in confining the overall thermal expansion of the Al line along the film normal. Electromigration strain measurements show that a linear stress gradient developed within the first hour of electromigration. The magnitude of the stress gradient changed little until fast stress relaxations occurred near the anode end of the line. Possible mechanisms are discussed in light of these observations.

scholarly journals Finite element modelling of the dynamics of groovy ball bearings

2018 ◽  
Vol 148 ◽  
pp. 16004
Author(s):  
Olamide Ajala ◽  
Ekaterina Pavlovskaia ◽  
Marian Weircigroch
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Thermal Stresses ◽  
Frictional Heating ◽  
Element Model ◽  
Contact Theory ◽  
Ball Bearings ◽  
Relative Slip ◽  
Thrust Bearings ◽  
Plastic Strength

Geometry modified thrust bearings exposed to rolling and sliding contact are subjected to wear and localized frictional heating caused by relative slip between the two sliding surfaces. This leads to a rise in temperature, thermal stresses and changes in the elastic and plastic strength and physical properties of the material. The changes in the properties in turn alter the stress state, the displacement field, life and reliability of the bearing. Hence, a finite-element model is created to study the dynamics of groovy thrust bearing. In this paper, Hertz contact theory and numerical method are used to simulate the dynamics and kinematics of groovy ball bearings. The optimal loading parameters are identified in this study based on the analysis of the system responses and properties. The results of the numerical analysis and validation are presented. The numerical analysis proves the concept of transforming rotational motion into axial oscillation and demonstrates the capabilities of the numerical simulation to accurately model the dynamics of the groovy ball bearing.

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