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RISS 인기검색어
- 검색키워드
- 저자 : Zhenping Feng (검색결과 3 건)
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Zhao Yang,Xiangsheng Li,Zhenping Feng,Lian Lu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
To solve the lack of reduced Blast furnace gas (BFG) mechanism under elevated pressure environment in numerical simulation, the present paper analyzes the sensitivity of every elementary reaction to combustion rate by using one dimensional laminar premixed reactor model. The steps with sensitivities larger than 0.1 are selected and the chemical kinetic parameters are revised by the method of weighted least squares fitting. The reduced 18-step mechanism which is specified to 0.1-3 Mpa is validated for laminar flame speeds, ignition delay times with available experiment data and GRI3.0 mechanism. Moreover, both the reduced and DRM-22 mechanisms are introduced into an experimental burner and an industrial gas turbine combustor simulation. The results of temperature and main species distribution illustrate that the 18-step mechanism is able to give a reasonable prediction combustion simulation. The 18-step mechanism lays the foundation of further studying the combustion of the low calorific value fuels at high pressure conditions.
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The role of precessing vortex core in two combustion regimes: Numerical simulation studies
Zhenlin Wang,Xiangsheng Li,Zhenping Feng,Zhao Yang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
Large Eddy simulation (LES) with finite rate chemistry was used to investigate the combustion dynamics in a lab-scale PRECCINSTA combustion chamber. Transient three dimensional numerical simulations were carried out at two different thermal powers (10 kW and 35 kW) with a fixed equivalence ratio of 0.7. The predicted results were compared with the experimental data and good agreements were found between them. In the cold flow field under both conditions, a precessing vortex core (PVC) in the inner shear layer (ISL) existing between the swirling jet and the inner recirculation zone (IRZ). However, two different flow and combustion dynamics were observed when combustion occurred. At thermal power of 10 kW, there was a V-shaped flame and the combustion of the flame was stable. The PVC disappeared and the vortices arrangement was symmetrical in the ISL. However, at 35 kW, there was a M-shaped flame with a PVC in the ISL and combustion instability triggered. In depth analysis of the characteristics of flow, temperature and heat release field, we found that the flame surface was wrinkled periodically by the PVC which enhanced the mixing between the cold fresh gas and hot burned products. Then, the mixture was ignited locally and heat release was rapid in the middle of the combustion chamber. These effects were directly related to the periodic vortices motion which was induced by PVC. It was confirmed that the influence of PVC on flame surface and heat release is an important factor for triggering the combustion instability at thermal power of 35 kW. The zone division based on different roles of flow/flame and thermoacoustic coupling was also discussed to illustrate the combustion instabilities caused by PVC.
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Numerical techniques for computing nonlinear dynamic characteristic of rotor-seal system
Xin Yan,Kun He,Jun Li,Zhenping Feng 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5
A transient CFD procedure to compute the nonlinear dynamic characteristic of the coupled rotor-seal system was presented in thisstudy. In each time step, the displacement diffusion model was implemented to govern the mesh deformation, and the URANS (UnsteadyReynolds averaged Navier-Stokes) equations were solved to obtain the transient fluid force on the rotor surface for the free vibrations. With the obtained fluid force from the CFD solver, the nonlinear equations of motion for a simplified rotor-seal system were numericallysolved on the basis of external user defined routines. During each transient time step, the computed fluid force from the CFD solver andthe rotor motion from the user defined routines were transferred to each other timely. The rotor center trajectories, frequency spectrumand projection of Poincaré section were calculated to investigate the nonlinear dynamic performance of the single disk rotor-seal system. The effects of the rotational speed and pressure ratio on the vibration characteristic of the rotor-seal system were analyzed by the bifurcationtheorem. The results show that the coupled rotor-seal system experiences a period-one motion, resonance, periodic-doubling motion,quasi-periodic motion, and finally possible chaotic motion as the rotor speed increases. The pressure ratio has pronounced effect on thefrequency response of the first-order critical speed; however, it has little influence on the motion state as well as the frequency responseof the rotating speed. Although a constant-clearance annular smooth stator seal was selected as the research object in the current paper,the presented transient CFD method is still available for other complex annular seals, such as labyrinth seal, honeycomb seal, pocketdamper seal, etc.
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