Gas turbine combustor
A gas turbine engine has a combustor module including an annular combustor having a liner assembly that defines an annular combustion chamber having a length, L. The liner assembly includes a radially inner liner, a radially outer liner that circumscribes the inner liner, and a bulkhead, having a height, H 1 , which extends between the respective forward ends of the inner liner and the outer liner. The combustor has an exit height, H 3 , at the respective aft ends of the inner liner and the outer liner interior. The annular combustor has a ratio H 1 /H 3 having a value less than or equal to 1.7. The annular combustor may also have a ration L/H 3 having a value less than or equal to 6.0.
1. An annular combustor for a gas turbine engine, comprising:
a first circumferentially extending liner having a longitudinal axis;
a second circumferentially extending liner spaced radially outboard of and coaxially circumscribing the first liner; and
a bulkhead extending between a forward end of the first liner and a forward end of the second liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air, the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L;
said annular combustor characterized in that the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6.
2. An annular combustor for a gas turbine engine as recited in claim 1 further characterized in that the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.
3. A method of designing an annular combustor for a gas turbine engine, the combustor having an inner circumferentially extending liner having an axis, an outer circumferentially extending liner spaced radially outboard of and coaxially circumscribing the inner liner, and a bulkhead extending between a forward end of the inner liner and a forward end of the outer liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air, the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L; the method comprising the step of sizing the annular combustor such that the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6.
4. A method of designing an annular combustor for a gas turbine engine as recited in claim 3 further comprising the step of sizing the annular combustor such that the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.
5. A method of controlling NOx formation in a gas turbine engine having an annular combustor having an inner circumferentially extending liner having an axis, an outer circumferentially extending liner spaced radially outboard of and coaxially circumscribing the inner liner, and a bulkhead extending between a forward end of the inner liner and a forward end of the outer liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air; the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L; the method comprising the steps of:
sizing the annular combustor such that the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6;
operating the annular combustor in a rich-quench-lean combustion mode whereby a fuel rich burn zone is provided in a forward region of the combustion chamber, and a dilution zone is provided downstream of the fuel rich burn zone;
admitting fuel to be combusted to the fuel rich burn zone only; and
admitting air to the combustion chamber, with about 10% to about 30% of the admitted air being admitted directly into the fuel rich burn zone, with about 40% to about 80% of the admitted air being admitted directly into the dilution zone, and with about 5% to about 35% of the admitted air being admitted as air for cooling the inner and outer liners.
6. A method of controlling NOx formation in a gas turbine engine as recited in claim 5 further comprising the step of sizing the annular combustor such that the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.
7. A method of controlling NOx formation in a gas turbine engine as recited in claim 5 wherein admitting air to the combustion chamber comprises admitting 12% to 18% of the admitted air directly into the fuel rich burn zone, admitting 50% to 70% of the admitted air directly into the dilution zone, and admitting 12% to 18% of the admitted air as air for cooling the inner and outer liners.
8. A method of controlling NOx formation in a gas turbine engine having an annular combustor having an inner circumferentially extending liner having an axis, an outer circumferentially extending liner spaced radially outboard of and coaxially circumscribing the inner liner, and a bulkhead extending between a forward end of the inner liner and a forward end of the outer liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air; the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L; the method comprising the steps of:
sizing the annular combustor such that the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6;
operating the annular combustor in a lean direct injection combustion mode whereby a fuel lean burn zone is provided in a forward region of the combustion chamber, and a mixing or dilution zone is provided downstream of the fuel lean burn zone;
admitting fuel to be combusted to the fuel rich burn zone only; and
admitting air to the combustion chamber, with about 50% to about 90% of the admitted air being admitted directly into the fuel lean burn zone, with about 0% to about 20% of the admitted air being admitted directly into the mixing or dilution zone, and with about 0% to about 25% of the admitted air being admitted as air for cooling the inner and outer liners.
9. A method of controlling NOx formation in a gas turbine engine as recited in claim 8 further comprising the step of sizing the annular combustor such that the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.
10. A method of controlling NOx formation in a gas turbine engine as recited in claim 8 wherein admitting air to the combustion chamber comprises admitting 60% to 80% of the admitted air directly into the fuel lean burn zone, admitting 0% to 10% of the admitted air directly into the dilution zone, and admitting 5% to 15% of the admitted air as air for cooling the inner and outer liners.
11. A gas turbine engine having a combustor, a compressor, and a turbine coaxially disposed about a central longitudinal axis, characterized by an annular combustor comprising:
a first circumferentially extending liner having an axis disposed coaxially with the longitudinal axis of the engine;
a second circumferentially extending liner spaced radially outboard of and circumscribing the first liner; and
a bulkhead extending between a forward end of the first liner and a forward end of the second liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air, the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L;
said annular combustor characterized in that the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6.
12. A gas turbine engine as recited in claim 11 further characterized in that the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.
13. A gas turbine engine having a combustor, a compressor, and a turbine coaxially disposed about a central longitudinal axis, characterized by an annular combustor comprising:
a first circumferentially extending liner having an axis disposed coaxially with the longitudinal axis of the engine;
a second circumferentially extending liner spaced radially outboard of and circumscribing the first liner; and
a bulkhead extending between a forward end of the first liner and a forward end of the second liner and cooperating therewith to define a single annular combustion chamber for combusting fuel in air, the bulkhead having a height, H 1 , and the combustion chamber having an exit height, H 3 , and a length, L;
said annular combustor characterized in that:
the ratio of the bulkhead height to the combustor exit height, H 1 /H 3 , has a value in the range from 1.2 to 1.6; and
the ratio of combustor length to the combustor exit height, L/H 3 , has a value less than or equal to 6.0.