Dissertation > Excellent graduate degree dissertation topics show

Study on Flammability Limits of Methane-Air Laminar Premixed Flames at Elevated Pressure

Author: FanRong
Tutor: ZhangHai
School: Tsinghua University
Course: Power Engineering and Engineering Thermophysics
Keywords: flammability limits counterflow flames laminar premixed flames microgravity pressure effect CHEMKIN
CLC: TK16
Type: Master's thesis
Year: 2008
Downloads: 246
Quote: 3
Read: Download Dissertation

Abstract


Understanding the lean-flammability limits and the controlling mechanisms of high-pressure mixture gases is significant in design and modeling the combustor such as gas turbine operating at high pressures. Existing researches on this subject are very limited and mainly only focus on the numerical simulation, and experiment data are nearly unavailable. In this paper, a theoretical and experimental study on the flammability of lean CH4/Air has been carried out with the recently built dropping tower located National Microgravity Laboratory of China (NMLC) operated by Chinese Academy of Sciences Institute of Mechanics. The flammability limit of CH4/Air at various pressure conditions were measured.Numerical simulation of 1-D freely propagating and opposed-jet counterflowing laminar,premixed CH4/Air flames at elevated pressures was conducted with the improved PREMIX model and OPPDIF model in CHEMKIN. The results showed that pressure possesses a significant effect on the flame’s burning rate, flame structure, flame thickness, and flame speed, while has minor effect on flame temperature and radiation heat loss. Furthermore, the variation of the flammability limit with pressure is non-monotonic. When pressure increases from ambient pressure, the flammability limits increases and then decreases when it reaches a peak value. To the 1-D freely propagating flames, the peak values appear at around P=5atm, while to the opposed-jet counterflowing flames, they appear at around P=4atm. To assess this phenomenon, sensitivity analysis of the near-limit flames was conducted and the results showed that the reaction mechanisms for the strongly burning flames and the near-limit weak flames are different and for the near-limit flames at different pressure are also different. The three-body chain termination reaction was suppressed when pressure is high than a critical value.The extinction limits of opposed-jet counteflowing methane/air flames of various strain rates were measured at normal gravity and microgravity at different elevated pressures. The results shows that the microgravity data are noticeably different from the normal gravity ones, indicating that buoyancy effective is not negligible. A fairly excellent agreement was found between the microgravity experimental data and numerical simulation in the variation of flammability limits with pressure at a fixed strain rate for the counterflowing flames.

Related Dissertations

  1. Study of the Non-invasive Arterial Blood Signal Detection Base on Near-infrared Dynamic Spectrum,TP274
  2. Lattice Boltzmann Simulation of Marangoni Convection with Soret Effects in an 2D Rectangular Cavity,O351
  3. Kapok fiber assembly compressive properties of,TS102.2
  4. Three-dimensional Numerical Simulation of Thermocapillary Convection in Detached Solidification Under Axial Magnetic Field,TK124
  5. Research on the Ground Passive Suspension Systems for the Large-Scale Space End Effector,TP241.3
  6. Research on Rotary-Arm Micro-Gravity Simulation Device of Space Manipulator,TP241
  7. Simulation and Analysis of HCNG Laminar Burning Velocity,TK401
  8. Research on the Failure Mechanism of Fractured Rock Mass Using Discontinuous Deformation Analysis,TU452
  9. The Heat Transfer and Kinetic Simulation of Ozone Generation Via Dielectric Barrier Discharge,TQ123.2
  10. Simulated Microgravity Induces Human Umbilical Vein Endothelial Cells Autophagy,R85
  11. Effects of Heavy Ion Radiation on Rat Frontal Cortex and Microgravity on Rat Immune Tissues Studied by NMR-Based Metabonomics Data Analysis,Q691
  12. Research on the Transfer Alignment Method of Space Maneuver Vehicle on SINS,V249.322
  13. Effects of simulated microgravity on osteoblast structure of spindle,R85
  14. The Development of Microgravity Landing Buffer Test Device for Asteroids and Comets,V416.8
  15. The Effects and Mechanisms of Microgravity on Expression of TF in Monocytes,R85
  16. Disruption of Microfilament System Induced by Simulated Microgravity Affects the NO/NOS System and the Markers Including Alkaline Phosphatase (ALP) and Osteocalcin (OCN) in Osteoblasts,R85
  17. Impacts of Simulated Microgravity on Proliferration of K562 Cells,R85
  18. Research of the High Precision Control System for Semi-active Microgravity Ground Simulation Platform,TP273
  19. Effect of Ambient Pressure and Thermal Environment on Single Droplet Evaporation and Combustion,TK16
  20. (Nd_ (0.8) Pr_ (0.2)) _ (13.0) Fe_ (80) Nb_1B_6 nano- rare earth permanent magnet material behavior of the coercivity,TM273
  21. Mechanism Simulation of Absorption Reduction Catalyst for Reducing NOx-PM Exhaust Emissions and Pilot Study on Lean Burn Catalyst,TK421.5

CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Fuel and combustion
© 2012 www.DissertationTopic.Net  Mobile