摘要
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, (θ<sub>L</sub>): pressure (P<sub>u</sub>), temperature (T<sub>u</sub>), mass flow rate (), and cross sectional area (A<sub>u</sub>). 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 (θ<sub>L</sub>) which are a function of (A, T, P, and ). 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 : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.
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, (θ<sub>L</sub>): pressure (P<sub>u</sub>), temperature (T<sub>u</sub>), mass flow rate (), and cross sectional area (A<sub>u</sub>). 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 (θ<sub>L</sub>) which are a function of (A, T, P, and ). 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 : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.
作者
Ali S. Al-Shahray
Ali S. Al-Shahray(College of Engineering, Jazan University, Jazan, KSA)
