Combustion device
A combustion device, such as an afterburner 4 for a gas turbine engine, comprises primary and secondary fuel delivery means 12, 20 . Pressure fluctuations in the afterburner 4 are damped by reducing the supply of fuel through the primary fuel delivery means 12 during pressure peaks. This is achieved by means of a spill valve 18 , controlled by a controller 22 in response to pressure in the afterburner 4 as sensed by a transducer 24 . The spill valve 18 diverts a proportion of the fuel to the secondary fuel delivery means 20 . The secondary fuel delivery means 20 is positioned upstream of the primary fuel delivery means 12 by a distance X, such that the secondary fuel delivery means serves to supply additional fuel to the combustion zone 26 during pressure troughs.
1. A combustion device for an engine comprising:
a duct for conveying a gas flow established in operation;
primary fuel delivery means for delivering fuel to the duct;
secondary fuel delivery means for delivering fuel to the duct;
a combustion region disposed downstream of the primary fuel delivery means and the secondary fuel delivery means; and
control means comprising:
a pressure transducer responsive to fluctuating pressure in the duct, and
a valve arranged to divert fuel from the primary fuel delivery means in response to the fluctuating pressure in the duct, wherein
the control means controls the valve for reducing the flow of fuel to the primary fuel delivery means in synchronism with peaks in the fluctuating pressure in the duct by diverting the fuel from the primary fuel delivery means to the secondary fuel delivery means, wherein
the secondary fuel delivery means discharges the fuel into the duct and is disposed at an axial distance upstream of the primary fuel delivery means with respect to a direction of the gas flow, the axial distance selected such that the fuel discharged from the secondary fuel delivery means is capable of reaching the combustion region at troughs in the fluctuating pressure in the duct.
2. The combustion device of claim 1 , wherein the axial distance between the primary fuel delivery means and the secondary fuel delivery means is not less than 0.5 m and not more than 1 m.
3. The combustion device of claim 2 , wherein the axial distance is not less 0.6 m and not more than 0.8 m.
4. The combustion device of claim 1 , further comprising an afterburner for a gas turbine engine.
5. The combustion device of claim 4 , wherein the secondary fuel delivery means is disposed to deliver fuel to a bypass duct of the gas turbine engine.
6. The combustion device of claim 1 , wherein the axial distance is calculated based on characteristics of the engine including at least one of a gas flow rate through the engine, a gas flow rate through the duct, and a frequency of the fluctuating pressure in the duct.
7. The combustion device of claim 1 , wherein the duct encloses a core engine and the secondary fuel delivery means is disposed adjacent to the core engine.
8. The combustion device of claim 1 , wherein the duct encloses a core engine and the secondary fuel delivery means is disposed downstream of the core engine.