http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Foad Vashahi(포아드 바샤이) (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
-
Mohamed Yahya(모하메드 야히야),Jonggeun Bae(배종근),Foad Vashahi(포아드 바샤이),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8
Nowadays, most of the gas turbine combustors are performed under a lean premixed condition. Therefore, there is an instability case would rise due to the unstable combustion. One from these instabilities is the coherent structures due to the pressure fluctuation, which is generated by the mixing process between air and methane (CH4). Most of the scientific research tries to suppress these fluctuations experimentally and numerically. Therefore, our study focuses on the impact of these fluctuations on the flow structure beside the mixture fraction between air and CH4 inside a gas turbine combustor model numerically. Three-dimensional Unsteady Reynolds Averaged Navier-Stokes (URANS) model is performed to investigate the response of the flow structure by imposing periodical oscillations of the CH4 injection frequency at the entrance of the combustor. Theses frequencies are 0, 50, 100, 250 and 500 Hz, respectively. Air flows through an axial swirl by 11.9 g/s. The equivalence ratio between the air and CH4 is 0.5. Results of the flow field and the oscillating frequency show that there is a complete similarity in the flow fields towards formation a sufficiently long central recirculation zone length due to the separation of shear layers, which grow with the downstream distance. On the other hand, the dynamic response of the injector flow is investigated in the second part of this study. When ff = 0 Hz, two harmonic oscillation exits are controlling by the Precession Vortex Core around the central recirculation zone. The highest amplitude is at with fh = 8 Hz where is a strong pressure oscillation as the turbulent intensity is high. When ff = 50 Hz, the spectra show that there are three peaks the first one corresponding to the ff and the other two are to fh. A dramatically increased in the spectra plot when ff = 100 Hz. When ff increases to 250 Hz, only two amplitudes are shown in the spectral plot at ff =fh and it is strong and the other one is weak when fh~ 2ff. Similarly, when ff = 500 Hz, the only first subharmonic response fh= 500 Hz and this leads to the frequency-locking phenomena.
-
Mohamed Yahya(모하메드 야히야),Jonggeun Bae(배종근),Foad Vashahi(포아드 바샤이),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8
In this current work, a gas turbine combustor model is investigated numerically. Here, the volume of fluid (VOF) technique is applied because of its significant impact on the uniformity index description and an accurate prediction for the phase distribution. In this regard, a comprehensive analysis for the uniformity index inside in a gas turbine combustor model is numerically studied under the effect of the swirling flow. The uniformity index describes the distribution of a certain quantity on a surface. The numerical approach used in this work is Unsteady Reynolds Averaged Navier-Stokes (URANS). Air enters through an axial swirl by 11.9 g/s. This study is a non-reacting model and the equivalence ratio between the air and CH4 is 0.5. This study highlights the need for ensuring a uniform fuel flow distribution inside gas turbine combustors. The uniformity index is achieved for the following four aspects: (a) mixing ratio, mean mixing ratio, Turbulent Kinetic Energy and axial velocity in the cylindrical coordinates at different locations. Results show that the flow before the swirl is uniform more than the other side from the swirl. This is due to the nature of swirling flow by adding adverse pressure gradients to the flown field. The effect of uniformity changes with the distances between the extraction sections. In addition, there is a great influence on gas mixture homogeneity. After the swirl, the uniformity index of mixing ratio has a steady rate by 0.55, until the beginning of the injector raises to 0.6. Interestingly, the swirling flow and multi-hole gas orifices emphasis on the mean mixing ratio uniformity index. Thus, the proportion of it progressively increases to 0.80 at the injector exit. After the swirl, Turbulent Kinetic Energy decreases to the injector exit. Dramatically increase is inside the combustor which has positive effects on mixture distribution and combustion intensity.
-
Effect of Fuel Temperature on the Drop Size Distribution Function
Reza Alidoost Dafsari(레자알리두스트다프사리),Shahnaz Rezaee(샤나즈 레자이),Foad Vashahi(포아드 바샤이),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8
The spray structure and drop size distribution issuing from industrial nozzles are important for their application. In gas turbine combustion the uniformity and spatial distribution of the swirl spray initiates the combustion efficiency and product control. This study investigates the effect of injection pressure and physical properties of a commercial jet fuel (JET-A1) in a wide range with controlling the fuel temperature on the spatial structure of the spray. Furthermore, multiple droplet distribution functions suggested in the literature were examined to find the best applicable fit. Spray structure and droplet size measurement were carried out by applying laser diagnostic methods namely phase Doppler anemometry and Mie-scattering imaging method. The results showed with increasing both injection pressure and the fuel temperature and accordingly the decreasing the fuel viscosity, surface tension and density, enhances spray cone angle and atomization quality. Both studied parameters decreased the breakup length and consequently spray mean droplet size while widened the spray cone angle. Moreover, an in-depth attempt was made to find the accordance of q value of Rosin-Rammler distribution function to fuel temperature.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
