Loading...

Numerical Study of Diffusion Flame in Micropropulsion Systems

Mokhtabad Amrei, Mana | 2009

638 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41580 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Darbandi, Masoud
  7. Abstract:
  8. Modern technology is accompanied by miniaturized devices. With increasing the use of micro satellites and micro airial vehicles (MAVs), finding new power-generating resources is inevitable. Batteries were always an option however high efficiency, long life-span and environmental consideration have encouraged the researches to focus on micro combustion. On the other hand, hydrocarbon fuel contains about 100 times more energy per unit mass than lithium-ion batteries. Micro combustion is defined as a combustion which is occurred bellow quenching distance and old literatures were uncertain about occurrence of such combustion. In this paper we present the fundamental concepts of micro combustion and numerically solve a micro diffusion flame around a micro jet. The jet was modeled as a rigid chamber with no heat transfer. For numerical simulation, we used the finite volume element method. Assuming a simple rectangular solution domain, we apply the structured quadrilateral grid to discrete the domain. In a finite element approach, nodes are located at four corners of each element. The nodes are the locations of unknown variables and any of them belongs to four neighboring elements. Each element is broken into four sub-control volumes (SCVs) using the vertical and horizontal symmetry axes of each square. The proper assemblage of the discrete sub-control volumes from different neighboring elements creates a closed area around each node, which can be subsequently used to employ the conservation laws. These SCVs creates four cell faces in each element. The fluxes on each of these four faces are estimated at their midpoints, which are called “integral points”. Normal direction to each cell face is needed for integrating purposes. The normal vectors are assumed positive when they are counter-clock-wise. The governing equations of mass, momentum, energy and chemical species are written for a steady reacting flow. The upwind physical influence model is used to approximate the convection fluxes. With regard to the physics of flow, this consideration provides the necessary coupling between velocity and pressure. We solved mass and momentums equations in a coupled form. Using the flow solution, we then solved the species and energy equations in a semi-coupled manner. A simple chemical reacting system was used to model the reacting flow. Flame shape and concentration of species were examined for Methane/Air micro-diffusion flame. Mole fraction contours resulting from the numerical solution confirmed the idea that the effect of buoyancy force would be negligible in micro diffusion flames. In addition comparing the results with macro diffusion flames showed that the influences of diffusive forces would be dominant and as it was expected the convection forces do not play a crucial role
  9. Keywords:
  10. Finite Volume Method ; Finite Element Method ; Combustible Flow ; Laminar Diffusion Flame ; Microcombustion ; Micropropulsion

 Digital Object List

  • محتواي پايان نامه
  •   view

 Bookmark

No TOC