TITLE:
Theoretical Study of Combustion Processes in Aero Gas Turbines for Air Craft Engines
AUTHORS:
Ali S. Al-Shahray
KEYWORDS:
Blow Off, Re-Ignition, Loading Parameters, Volumetric Heat Release Rate
JOURNAL NAME:
Open Journal of Applied Sciences,
Vol.12 No.8,
August
31,
2022
ABSTRACT: Combustion
process involves various physical and chemical processes which govern and
control flames initiation in aero gas turbine engines. During certain flying
conditions, at full load, unexpected critical situation may take place in such
engines called blow off conditions, which leads to flames diminishing in the
combustion chamber of such engines. Gas motion, flow velocity and turbulence
kinetic energy are the most important parameters in ensuring flame stabilities.
These parameters play a tremendous role and effects on this phenomenon. In gas
turbines, the
flame exists within a high velocity, non-uniform and intensely turbulent flow
field, therefore careful temperature control is vital. Another important factor
which must be considered to avoid blow off conditions, is mixture strength.
Nearly, all modern gas turbines, due to emissions restrictions, operate on lean
mixture conditions which are hard to ignite and lower flame temperatures and thus more risk to reach blow
off conditions which leads to a complete flame extinction. These conditions may
exist in an air craft engines due to sharp changes in loading parameters, (θL): pressure (Pu),
temperature (Tu), mass flow rate (ṁ),
and cross sectional area (Au). At present there is no
detailed theory of gas turbine combustion. Therefore, we must resort to simple
models and experimental correlations. This paper
investigates the blow-off
phenomena in aero
gas turbine engines, its causes and estimation of required energy to ensure
recovery (re-ignition) again inside the combustion chamber. Identifying the
conditions at which blow-off takes place and associated loading parameters (θL) which are a function of (A, T, P, ø and ṁ). The paper also, quantify the recovery conditions
(required energy to re-ignition, change in loading parameter (Δq) Power, Required
VHRR: (Volumetric Heat Release Rate) and changes in other loading variables (ρ: density, T: Temperature, P: Pressure, and ṁ:
mass flow rate) tarts
with discussing causes of blow off along with effecting operating conditions.