Modelling of High-Pressure Combustion Rig with After-Burner and Supersonic Nozzle using Plug Flow Reactor Network Model

摘要

Plug flow reactor (PFR) is an ideal reactor used to model steady state reacting fluid flow through a fixed area conduit in which the fluid may have different compositions at different locations. No radial or circumferential variations, frictionless flow, no axial mixing, ideal gas behavior are the main assumptions made in modelling a PFR. Coupled differential equations, essentially describing the change in density, temperature and mass fractions of the species along the flow direction are used to model an ideal PFR. The present study develops a generic MATLAB sub-routine with the capability to solve the above said equations for any given realistic PFR inlet conditions with constant area or converging/diverging cross-sectional areas, which changes as a function of axial location. The computational results provided by this sub-routine was first validated against a 3-D periodic model simulation of a faceted nozzle by providing the same boundary conditions at the inlet as that for the PFR module.This sub-routine is then used to model a High-pressure Combustion Rig (HPCR) with After-Burner (AFB) followed by a supersonic nozzle by creating a network of serially connected PFRs wherein the output of the previous PFR is fed as the input to the subsequent PFR. The objective of creating such a network model is to better predict the temperature and mass fraction of species at any given location along the flow direction, and to aid in the design of a facility to investigate supersonic jet noise at afterburner conditions. Major components of HPCR are primary combustor, heat exchanger (before AFB), followed by an AFB, heat exchanger (after AFB) and a supersonic nozzle. A section of the primary combustor is modelled as Perfectly/Well Stirred Reactor (PSR/WSR) to initiate ignition of the air-fuel mixture. Once ignited, the rest of the primary combustor and all other components including AFB are modelled as PFR.