Fuel and oxidizer are introduced on two opposite sides of burners at subsonic velocity. A stationary flame is generated and sustained between fuel and oxidizer sides by balancing momentums. To numerically simulate counter-flow diffusion flame, conservation equations reduced to 1-D with certain assumptions are solved, with known boundary conditions at fuel and oxidizer sides. The solution describes the profiles of various properties along with species concentrations spatially.
Consider reactants (fuel/oxidizer) contained in a piston cylinder arrangement (constant pressure) or a closed container (constant volume). They will react at each and every location within the gas volume at the same rate. This means that there are no temperature or composition gradients within the mixture, there is a single temperature and a set of species concentration suffice to describe the evolution of the system. By applying conservation laws and solving differential equations with the initial conditions defined, we get temporal evolution of temperature and species concentrations. There will be a sudden rise in temperature/pressure/change in some species concentration, after some period of time. This time is called ‘Homogeneous Ignition delay time’.
A Perfectly Stirred Reactor (PSR) is an ideal reactor in which perfect mixing (homogeneity) is achieved inside the control volume. It is assumed to be operating at a steady state. A mean residence time is defined in PSR as density multiplied by volume divided by mass flow rate. Solving conservation equations, we get the mixture fractions and temperature of products for given inlet conditions of mixture factions and temperature at a given system pressure.
Consider a reactor which is in steady state and has steady flow with no friction. Assuming ideal conditions of having no mixing in axial directions and uniform properties in radial direction, this reactor represents a plug flow reactor. A numerical solution to PFR problem describes the reactor flow properties including composition as a function of distance. The temperature and concentration of reactants at the inlet should be given as input along with pressure and inlet velocity.
A flame is a self-sustaining propagation of a localized combustion zone at subsonic velocities. When a flame is initiated in a tube containing a combustible gas mixture, it propagates at certain speed. This speed is known as premixed laminar flame speed and is denoted by ‘SL’. To put in other words, premixed laminar flame speed is the speed at which reactants must be supplied to produce a stagnant flame. To obtain a numerical solution for flame speed, conservation equations for 1-D flame are solved with boundary conditions and initial guess.