| 1. |
- Cai, Xiao, et al.
(författare)
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高Ka 数下分子扩散效应对氨气/氢气/空气预混火焰结构的影响
- 2022
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 43:8, s. 2025-2032
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous planar laser induced fluorescence (PLIF) and Rayleigh scattering thermometry (RST) were applied to measure the key species and temperature fields of premixed ammonia/ hydrogen/air jet flames to investigate the effects of differential diffusion on flame structure. NH-PLIF technique was developed to properly characterize the reaction zone of ammonia flames. Three flames with similar laminar combustion characteristics but different Lewis numbers (Le) were investigated. Results show that the reaction zone are locally thickened for all flames at high Karlovitz number (Ka). Furthermore, the reaction layer thickness increases with the Le, indicating that the differential diffusion still plays a role in the turbulent combustion even in the distributed reaction zone regime.
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| 2. |
- Han, Lei, et al.
(författare)
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基于飞秒激光的一维速度场测量方法
- 2022
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 43:1, s. 267-271
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Tidskriftsartikel (refereegranskat)abstract
- Femtosecond laser-induced cyano chemiluminescence uses femtosecond filaments to tag molecules in a flow field, and velocity information of the flow field can be obtained by observing the displacement of the tagged molecules within a known time. The one-dimensional (1D) emitting line contains 1D velocity field information, but only the velocity at the central point can be given because it is unable to precisely correlate the position information before and after the line moves. For this problem, we propose a 1D velocity field inversion algorithm, which can invert the velocity of the whole emitting line according to the displacement of the emitting line and its shape, and finally obtain the 1D-2C velocity field information on the line. By using the moving trajectory of multiple emitting lines we can also obtain the 2D velocity field information.
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| 3. |
- Li, Huixiong, et al.
(författare)
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蒸汽-冷流体接触冷凝流动的数值模拟
- 2005
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Ingår i: Gongcheng Rewuli Xuebao. - Beijing, China. - 0253-231X. ; 26, s. 963-966
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Tidskriftsartikel (refereegranskat)abstract
- 介绍了关于蒸汽-冷流体直接接触冷凝流动与传热的数值计算模型与部分研究结果。用Level Set方法确定蒸汽-冷流体接触界面的位置和形状,建立了对蒸汽和冷流体普遍适用的动量、能量和质量守恒方程,在能量和质量寺恒方程中增加了部分项用于计算蒸汽冷凝所产生的影响。用有限差分法在交错网格上离散控制方程,用Runge-Kutta法-五阶WENO组合格式求解Level Set输运方程,用压力修正的迭代Projection方法求解动量方程,而用SIMPLE方法求解温度控制方程。对算例的计算结果表明,本文所建立的数值计算模型能反映物理现象的宏观特性。根据计算结果,分析了本文模型的优缺点,并指出了今后改进的方向。
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| 4. |
- Li, Liangxing, et al.
(författare)
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冷中子源冷包截面含汽率数理模型探讨
- 2007
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Ingår i: Gongcheng Rewuli Xuebao. - Beijing, China. - 0253-231X. ; 28, s. 64-67
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Tidskriftsartikel (refereegranskat)abstract
- 文章推导出一种计算冷包截面含汽率的数学模型;将模型计算结果与已知文献相关实验结果进行对比,验证了模型的正确性.利用该模型探讨了冷包截面含汽率的影响因素如气泡直径,工质液体的密度、粘性,加热功率等.模型计算表明:气泡直径越大,在同一截面高度处的截面含汽率越低;工质粘性越大,在同一截面高度处的截面含汽率越高.本文模型的计算结果能对冷包设计提供理论支持.
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| 5. |
- Li, X., et al.
(författare)
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Flow Pattern Identification of Porous Media Based on Signal Feature Extraction and SVM
- 2022
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - : Science Press. - 0253-231X. ; 43:11, s. 2957-2965
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the visualization experiment of gas-liquid two-phase flow in porous media is carried out. The typical flow patterns of bubbly flow, slug flow and annular flow are photographed by high-speed camera, and the corresponding differential pressure fluctuation signals are measured and recorded, Using probability density function (PDF) and power spectral density (PSD) curves, the time-domain and frequency-domain characteristics of differential pressure signals corresponding to each flow pattern are analyzed, and the quantitative characteristic parameters are introduced to construct the characteristic vector reflecting the time-frequency characteristics of differential pressure signals. A two-phase flow pattern identification method in porous media based on support vector machine (SVM) is proposed. The results show that the overall recognition rate of the three flow patterns measured by the method is 98.18%, which can provide a new technical support for the on-line recognition of gas-liquid two-phase flow patterns in porous media.
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| 6. |
- Li, Xiaofeng, et al.
(författare)
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双色光束增强飞秒激光氮气标记示踪测速技术的研究
- 2022
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 43:10, s. 2826-2830
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the fluorescence of FLEET (femtosecond laser electron excited tagging) was enhanced by two color femtosecond laser. the intensity of FLEET was increased about 20% with two laser pulses that were 400 μJ/pulse at 266 nm and 3 mJ/pulse at 800 nm, and the results indicated that there was nearly no influence on lifetime and wavelength of fluorescence from FLEET. This result provides many information for the following studies.
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| 7. |
- Wang, Yuli, et al.
(författare)
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Dynamics of ultra-high speed liquid jets in still gas
- 2013
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 34:9, s. 1654-1658
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Tidskriftsartikel (refereegranskat)abstract
- Instability of free liquid jets is an important fundamental problem rising from multiple engineering fields such as material processing, energy production, etc. Ultra-high speed condition brings new difficulties to stability research. This work demonstrates flow patterns of ultra-high speed liquid jet (UHSLJ) and points out the potential challenges in relevant investigation, from a turbulence point of view. A PDA measurement of flow velocity and droplet size on a cross-section of UHSLJ is present. Flow physics involved in the jet is discussed together with the limitation of this measurement. It is found that the velocity profile on the measured section obeys 1/7 power law. Concentration of droplets has an inverse gradient (from outer region of a jet pointing to the inner region) in the breakup section. Flow properties hold an axisymmetric distribution in the atomization section while this section itself has an evident two-layer (core-outer) structure. The length scales (size of drop) that be resolved by the present experiment is estimated to be only 0.1% of the entire scales.
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| 8. |
- Yu, Sen Bin, et al.
(författare)
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非预混旋流火焰中部熄火及重新稳燃机理研究
- 2021
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 42:12, s. 3312-3319
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Tidskriftsartikel (refereegranskat)abstract
- The effects of quarl on the non-premixed swirling flames were studied by performing simultaneous OH-PLIF/PIV measurements experimentally and coupling LES with PDF combustion model numerically. The results showed that LES-PDF method can successfully capture the swirl flow fields and flame structures even including local extinction and re-stabilization. Compared to the no quarl case, the quarl plays a significant role on the expansion of the recirculation zone thus influencing the attached flame and the following extinction, though it affects the re-stabilization height rarely. With the high scalar dissipation rate, local extinction occurs due to the strong heat loss caused by the central fuel jet. In addition, fuel and air are partially premixed accompanied with some partial oxidation reactions producing CH2O, which provides preferential conditions for the stabilization of the non-premixed swirling flame. Moreover, the reaction rate term of OH is at least 10 times larger than its diffusion term, indicating that the reaction front dominates the re-ignition process for the flame re-stabilization downstream. It is thus concluded that the partially premixed flame propagation plays a dominant role in controlling the re-stabilization of this flame.
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| 9. |
- Zhang, Jian, 1978, et al.
(författare)
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Examinations on closure models of conditionally filtered LES
- 2011
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 32:2, s. 357-359
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Tidskriftsartikel (refereegranskat)abstract
- The DNS and the conditionally filtered LES (CFLES) were combined to examine the validity of the linear-diffusion approximation and the first-order closure in CFLES equation. The linear-diffusion approximation was applied to closing transport term in mixture-fraction space in CFLES equation, and the first-order closure was used in closing conditionally filtered reaction source term. The first two order moments of filtered mass-fraction of the reactant were obtained by using CFLES and were closed to results of the DNS, which well examined the validity of the approximations mentioned above.
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| 10. |
- Zhu, M. -M, et al.
(författare)
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The vorticity field of acoustic modulated free jets
- 2012
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 33:10, s. 1811-1814
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Tidskriftsartikel (refereegranskat)abstract
- The motivation of this paper is to investigate the effects of acoustic modulation on the structures of free jet. Large eddy simulation is performed on three dimensional free jet of Re number 2200 with multigrid method. Comparisons of the vorticity fields are made between the unmodulated jet and perturbed jets with different modulation frequencies. When the modulation frequency is near the preferred mode of the natural jet, the flow field changes significantly. The azimuthal vorticity rolls up into large vortex rings, and the jet spreads more widely. When the modulation frequency is about the twice of the preferred mode, vortex pairing happens and the subharmonic wave becomes dominant. The flow fields are almost the same as the natural jet when the modula-tion frequency is much higher than the preferred mode. The distribution of streamwise vorticity is examined for the modulated jet near the preferred mode, and agrees qualitatively with the experiments.
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