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Author: search.filters.author.Prapamonthon, P.Has files: No

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    Numerical Study on Flow Physics of Damaged Vane Trailing Edge
    (2024-01-01)
    Thammachote, B.
    ;
    Premyothin, J.
    ;
    Khumhaeng, S.
    ;
    Tanpradit, D.
    ;
    Dipasquale, D.
    According to practical applications in gas turbines, the turbine's nozzle guide vane (NGV) is the first downstream component of the combustor that experiences high thermal loads from burned gases. This situation can severely damage the vane material, particularly the trailing edge (TE). This is because of the limitation of TE thickness and the difficulty of effective cooling in that region. Moreover, the deterioration of the TE surface leads to vane fatalities and has a negative impact on turbine performance because the flow field is unfavorably changed during the operation. This paper aims to numerically study the flow physics of a damaged vane TE using a 3D steady-flow CFD simulation with the SST k-turbulence model. Under the assumptions of ideal gas and compressible flow, air is used as the burned gas. To simplify the vane damage shape, the broken pattern at the TE is given in a long cutback geometry in the simulation. Numerical results in terms of turbulent kinetic energy (TKE), vorticity magnitude, turbulent viscosity, and streamlines are compared and discussed. The interesting findings show that with the inclusion of the damaged TE, the TKE and turbulent viscosity in the broken region increase dramatically on both the midspan and vertical planes. Furthermore, an increment in the vortex size is observed on the midspan plane. However, the vortex centers along the broken region disappear and are replaced by smooth streamlines.
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    Numerical Investigation on Aerodynamic Drag and Noise of Pantographs with Modified Structures
    (2022-01-01)
    Yao, Y.
    ;
    Sun, Z.
    ;
    Li, G.
    ;
    Prapamonthon, P.
    ;
    Cheng, G.
    It is well known that the pantograph, which works as a complex component of high-speed trains, is an important source of aerodynamic drag and aerodynamic noise of a high-speed train (HST) that can affect HST performance, comfort for passengers, and quietness of nearby communities. Thus, comprehensive studies on aerodynamic characteristics including aerodynamic drag and aerodynamic noise obtained by the pantograph need to be conducted. This work presents the aerodynamic characteristics including aerodynamic resistance and aerodynamic noise generated by the prototype pantograph of a high-speed train running at a speed of 300 km/h using numerical techniques of improved delayed detached-eddy simulation (IDDES) and acoustic finite element method (FEM). Then, the structure of the original pantograph is modified by wrapping the insulators, and the base frame, so that aerodynamic resistance and aerodynamic noise may be reduced as expected. Numerical results obtained from the pantograph without modification, with two modifications to the original design i.e. the base frame, and the insulators, are discussed. Compared to the original pantograph, the two modifications of the pantograph at the base frame and the support insulators are conducive to reducing the aerodynamic drag of the pantograph. However, the results also show that the modified insulator may not achieve considerable success in noise reduction. Only the modified base frame shows that noise is reduced significantly. Therefore, this suggests that the pantograph with base frame modification is a better choice for resistance and noise reduction.
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    Reliability-based Design Optimization of Classical Wing Aeroelasticity
    (2020-07-27)
    Sleesongsom, S.
    ;
    Yooyen, S.
    ;
    Prapamonthon, P.
    ;
    Bureerat, S.
    Flutter speed of aircraft is very important and needs to be firstly specified before a certification applied for a new aircraft by airworthiness regulator to make sure that the aircraft is free from flutter in its flight envelope. By assuming geometrical and physical parameters known, the speed is usually estimated from deterministic analyses in a design stage. In practice, some parameters are finitely measured by observing, especially for the geometrical parameters, material properties and so on due to the random in nature, which causes uncertainty of information often called uncertainties. The purpose of this paper is to combine reliability analysis and optimum design of aeroelastic aircraft wing. The classical two-dimensional wing with a typical airfoil section is used as an example in this study. To quantify uncertainty in the design of flutter speed, the discrete-time aero-elastic model and worst-case scenario are applied. Furthermore, the comparison between optimum design with/without reliability is provided in this study. The results show the proposed technique leads to the flutter speed being more conservative and realizable compared with the traditional technique.
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    Numerically thermal analysis of a turbine vane at high temperature
    (2019-11-26)
    Prapamonthon, P.
    ;
    Yooyen, S.
    ;
    Sleesongsom, S.
    Using conjugate heat transfer, thermal analysis of a turbine vane coated with thermal barrier coating (TBC) at a high temperature is presented. Numerical results are carried out at two turbine inlet temperatures (T <inf>∞</inf>) i.e. 783 K (low) and 1566 K (high) under two turbulence intensities (Tus) i.e. 8.3% and 16.6%. The main findings of this research are that for both Tus, the metal surface temperature reduction at the high temperature is higher than that at the low temperature because of the lower heat-flux ratio at the higher temperature. Based on the metal temperature reduction, the increasing inlet temperature has a greater influence than the increasing turbulence intensity. The results also indicate that at T <inf>∞</inf> = 783 K, on the pressure side (PS) the metal surface temperature reduction at Tu = 8.3% is lower than that at Tu = 16.6%, while on the suction side (SS) no significant difference happens when Tu increases. Interestingly, an inverse phenomenon happens for both PS and SS, that is the metal surface temperature reduction at Tu = 8.3% increases above that at Tu = 16.6% when T <inf>∞</inf> increases. This discrepancy may suggest the instability of the surface heat-flux ratio due to complex heat convection at the different inlet temperatures.
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    Finite obstacle effect on the aerodynamic performance of a hovering wing
    (2019-10-01)
    Yin, B.
    ;
    Yang, G.
    ;
    Prapamonthon, P.
    The finite obstacle effect on the aerodynamic performance of a normal hovering wing is studied using the immersed boundary method. Phenomena of a two-dimensional wing hovering above, under, or on the side of a circular obstacle are presented. Parameters including obstacle size, distance, location, and flapping angle are investigated to study how the aerodynamic force and flow field are affected. The diameter of the obstacle ranges from 0.5c to 12c and the distance between the centroid of the wing and obstacle surface from 0.5c to 6c (c is the wing chord length). Previous observations of ground effects including force enhancement, reduction, and recovery occur similarly when the wing hovers above the obstacle of diameter greater than 2c. However, finite obstacles affect the aerodynamic performance differently when the size shrinks to a critical value. Force drops when the wing moves close and rises when moving away, opposite to the ground effect. As flapping angle amplitude increases, the force change tends to be consistent for different-sized obstacles. The top or side effect shows a different influence on the force change. Force monotonically increases as the distance decreases when the wing hovers under the obstacle. The side effect places a less important factor on the aerodynamic performance. All force changes under such circumstance are less than 13% referring to nonobstacle result. The gap between the leading or trailing edge of the wing and obstacle surface plays a significant role in the leading and trailing edge vortices generating, shedding, and pairing, which greatly affects the force change.