Prapamonthon, Prasert

Preferred name

Alternative Name

PRAPAMONTHON, Prasert

Prapamonthon, P.

Main Affiliation

International Academy of Aviation Industry

prasert.pr@kmitl.ac.th

Now showing 1 - 10 of 11

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Analysis of aerodynamic noise characteristics of high-speed train pantograph with different installation bases
(2019-06-01)
Yao, Yongfang
;
Sun, Zhenxu
;
Yang, Guowei
;
Liu, Wen
;
Prapamonthon, Prasert
The high-speed-train pantograph is a complex structure that consists of different rod-shaped and rectangular surfaces. Flow phenomena around the pantograph are complicated and can cause a large proportion of aerodynamic noise, which is one of the main aerodynamic noise sources of a high-speed train. Therefore, better understanding of aerodynamic noise characteristics is needed. In this study, the large eddy simulation (LES) coupled with the acoustic finite element method (FEM) is applied to analyze aerodynamic noise characteristics of a high-speed train with a pantograph installed on different configurations of the roof base, i.e. flush and sunken surfaces. Numerical results are presented in terms of acoustic pressure spectra and distributions of aerodynamic noise in near-field and far-field regions under up- and down-pantograph as well as flushed and sunken pantograph base conditions. The results show that the pantograph with the sunken base configuration provides better aerodynamic noise performances when compared to that with the flush base configuration. The noise induced by the down-pantograph is higher than that by the up-pantograph under the same condition under the pantograph shape and opening direction selected in this paper. The results also indicate that, in general, the directivity of the noise induced by the down-pantograph with sunken base configuration is slighter than that with the flush configuration. However, for the up-pantograph, the directivity is close to each other in Y-Z or X-Z plane whether it is under flush or sunken roof base condition. However, the sunken installation is still conducive to the noise environment on both sides of the track.
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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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Adsorption kinetic, equilibrium and thermodynamic study for the removal of Congo Red from aqueous solution
(2017-12-01)
Khan, Muhammad Imran
;
Zafar, Shagufta
;
Khan, Muhammad Ali
;
Buzdar, Abdul Rehman
;
Prapamonthon, Prasert
In this study, the adsorption of Congo red (CR) dye from aqueous solution onto cationic polymeric film (BIII) was investigated at ambient temperature. The effect of operational parameters such as contact time, membrane dosage, initial dye concentration and temperature on the adsorption of CR from aqueous solution was studied. Adsorption kinetics has been studied by employing several kinetic models and attained results showed that the adsorption data fitted-well to the pseudo-second-order kinetic model. Nonlinear forms of two parameters and three parameters isotherms were applied on experimental data and the results indicated that the adsorption data fitted well to the various two and three parameters isotherms. Thermodynamic study showed that the adsorption of CR onto cationic polymeric film (BIII) was an exothermic process.
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Numerical prediction of cooling performance sensitivity of 1st stage nozzle guide vane under aerothermal conditions
(2019-01-01)
Prapamonthon, Prasert
;
Yin, Bo
;
Yang, Guowei
;
Zhang, Mohan
To obtain high power and thermal efficiency, the 1<sup>st</sup> stage nozzle guide vanes of a high-pressure turbine need to operate under serious circumstances from burned gas coming out of combustors. This leads to vane suffering from effects of high thermal load, high pressure and turbulence, including flow-separated transition. Therefore, it is necessary to improve vane cooling performance under complex flow and heat transfer phenomena caused by the integration of these effects. In fact, these effects on a high-pressure turbine vane are controlled by several factors such as turbine inlet temperature, pressure ratio, turbulence intensity and length scale, vane curvature and surface roughness. Furthermore, if the vane is cooled by film cooling, hole configuration and blowing ratio are important factors too. These factors can change the aerothermal conditions of the vane operation. The present work aims to numerically predict sensitivity of cooling performances of the 1<sup>st</sup> stage nozzle guide vane under aerodynamic and thermal variations caused by three parameters i.e. pressure ratio, coolant inlet temperature and height of vane surface roughness using Computational Fluid Dynamics (CFD) with Conjugate Heat Transfer (CHT) approach. Numerical results show that the coolant inlet temperature and the vane surface roughness parameters have significant effects on the vane temperature, thereby affecting the vane cooling performances significantly and sensitively.
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Development and surface modification of anion exchange membrane for enhancement of antifouling potential in electrodialys process
(2018-01-01)
Khan, Muhammad Imran
;
Zafar, Shagufta
;
Khraisheh, Majeda
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Khan, Muhammad Ali
;
Buzdar, Abdul Rehman
The membrane fouling in the course of electrodialysis (ED) is a serious problem during water treatment which results to its shorter lifetime and higher energy consumption. Here, the antifouling property of previously reported BPPO-based anion exchange membranes (AEM) has been improved by surface coating with polydopamine (PDA). The modified and unmodified membranes were characterized in term of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) water contact angle and water uptake. The antifouling potential was investigated in term of transition time, i.e. the time elapsed before the fouling took place.
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CHT/CFD analysis of thermal sensitivity of a transonic film-cooled guide vane
(2019-01-01)
Prapamonthon, Prasert
;
Yooyen, Soemsak
;
Sleesongsom, Suwin
Thermal parameters are important variables that have great influence on life time of turbine vanes. Therefore, accurate prediction of the thermal parameters is essential. In this study, a numerical approach for conjugate heat transfer (CHT) and computational fluid dynamics (CFD) is used to investigate thermal sensitivity of a transonic guide vane which is fully film-cooled by 199 film holes. Thermal barrier coating (TBC), i.e., the typical TBC and a new one as the candidate TBC, and turbulence intensity (Tu), i.e., Tu=3.3%, 10% and 20%, are two variables used for the present study. At first the external surface temperatures of the vane material are compared. Next, the TBC surface temperatures are considered. Results show the major role of the lower thermal conductivity of TBC which results in the lower and more uniform temperature on the external surface of the vane substrate. Finally, the thermal sensitivity is presented in terms of the percentage reduction of the external surface temperatures of the vane material and the structural temperatures of the vane material at midspan, including the variations of average and maximum vane temperatures. Results show that TBC and Tu have significant effects on the external surface and structural temperatures of the vane substrate. The lower thermal conductivity of TBC leads to the higher difference between the thermal conductivity of the vane substrate and TBC, the reduction of heat transfer and the more uniform temperature within the vane structure. The results also show more effective protection for the average vane temperature from the two TBCs at higher Tus. However, Tu does not significantly affect the reduction of the maximum vane temperature even though the new TBC, which has the very low thermal conductivity, is used.
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Investigation of cooling performances of a non-film-cooled turbine vane coated with a thermal barrier coating using conjugate heat transfer
(2018-04-01)
Prapamonthon, Prasert
;
Yooyen, Soemsak
;
Sleesongsom, Suwin
;
Dipasquale, Daniele
;
Xu, Huazhao
The aim of this paper is to numerically investigate cooling performances of a non-film-cooled turbine vane coated with a thermal barrier coating (TBC) at two turbulence intensities (Tu = 8.3% and 16.6%). Computational fluid dynamics (CFD) with conjugate heat transfer (CHT) analysis is used to predict the surface heat transfer coefficient, overall and TBC effectiveness, as well as internal and average temperatures under a condition of a NASA report provided by Hylton et al. [NASA CR-168015]. The following interesting phenomena are observed: (1) At each Tu, the TBC slightly dampens the heat transfer coefficient in general, and results in the quantitative increment of overall cooling effectiveness about 16-20%, but about 8% at the trailing edge (TE). (2) The protective ability of the TBC increases with Tu in many regions, that is, the leading edge (LE) and its neighborhoods on the suction side (SS), as well as the region from the LE to the front of the TE on the pressure side (PS), because the TBC causes the lower enhancement of the heat transfer coefficient in general at the higher Tu. (3) Considering the internal and average temperatures of the vane coated with two different TBCs, although the vane with the lower thermal conductivity protects more effectively, its role in the TE region reduces more significantly. (4) For both TBCs, the increment of Tu has a relatively small effect on the reduction of the average temperature of the vane.
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Extra-low Reynolds number vane separation using immersed boundary method
(2019-01-01)
Prapamonthon, Prasert
;
Yin, Bo
;
Yang, Guowei
Nowadays, mini unmanned aerial vehicles (MUAVs) and micro air vehicles (MAVs) are not only beneficially used as aviation models but also as modern drones for military missions and other civilian applications. Hence, research and development of propulsion sources for MUAVs and MAVs dynamically increase with a future trend of high performance, but low energy consumption. Certainly, using micro and ultra-small-size gas turbine is a good option for the propulsion source. To achieve ideal flight of MUAVs and MAVs powered by micro and ultra-small-size gas turbines under this trend, understanding of flow phenomena at wide ranges of Reynolds number is essential. This research presents a 2D numerical study of characteristics of laminar flow separation and the trailing-edge vortex on a turbine vane at extra-low Reynolds numbers (Res) i.e. Re = 1800 and 3600, and three rotational angles (a) i.e. a = 0º, 15º and 30º using immersed boundary method (IBM). With this method, the problem of incompressible flow is addressed by a sharp interface IBM. Numerical results indicate that IBM can characterize phenomena of laminar separation flow, which usually happens on the turbine airfoil when laminar boundary layer cannot overcome adverse pressure gradients and viscous effects. To our current knowledge, this may be the first research to study flow behavior at such low Res for gas turbine vanes using IBM. Even though it is now not common to operate micro and ultra-small-size gas turbines under these conditions, it is important to know how aerodynamic performance may be if micro and ultra-small-size gas turbines need to run under such conditions in the near future.
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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.
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Understanding of temperature and cooling effectiveness sensitivity of a film-cooled vane under coolant inlet temperature effect: A case study
(2019-09-01)
Prapamonthon, Prasert
;
Yin, Bo
;
Yang, Guowei
;
Zhang, Mohan
This work presents a case study of the relationship between temperature and cooling effectiveness of a film-cooled vane under effect of coolant inlet temperature in two aspects based on the actual and base coolant inlet temperatures. Results are conducted in terms of temperature, cooling effectiveness, and heat transfer coefficient based on surface and volume analyses using CFD/CHT approach. Sensitivity of the vane temperature and cooling effectiveness under this effect is discussed also. The results show that for the surface basis, although the cooling effectiveness obtained from the actual coolant inlet temperature is quite straightforward and follows the definition of the cooling effectiveness directly, the cooling effectiveness obtained from the base coolant inlet temperature is more understandable because it corresponds to the variation of the surface temperature. Based on the volume basis and the base coolant inlet temperature, the 8% increase in the coolant inlet temperature causes the reduction of the average and maximum cooling effectiveness, which corresponds to 18 K and 25 K increments in the average and minimum temperatures, respectively. However, when the actual coolant inlet temperature is used, the variation of the cooling effectiveness is rather insensitive due to the reduction of heat flux on the hot-side wall.

Prapamonthon, Prasert

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