Apparatus and method for improving combustion stability
View Patent ↗A fuel nozzle for use in a gas turbine combustor is provided having the capability of injecting multiple fuel types as well as steam for NOx reduction. Combustion dynamics within a combustor due to the mal-distribution of steam are controlled by the placement of a meterplate at the steam inlet, such that the meterplate reduces steam velocity and increases steam pressure drop. A higher pressure drop reduces the sensitivity of the combustion process to upstream steam supply variations. A method for providing uniform steam flow to a plurality of fuel nozzle assemblies about a gas turbine engine is also disclosed.
1. The method of providing uniform steam flow to a plurality of fuel nozzle assemblies about a gas turbine engine, said method comprising the steps:
a. providing a gas turbine engine having a plurality of combustors and a manifold containing steam;
b. providing a plurality of fuel nozzle assemblies, each of said fuel nozzle assemblies having:
a first fuel inlet in fluid communication with a first fuel passage and first fuel injection means for supplying a first fuel to a combustor;
a steam inlet in fluid communication with a steam passage and steam injection means for supplying steam to a combustor;
an air passage and air injection means for supplying air to a combustor;
c. providing a means to flow steam from said manifold to each of said fuel nozzle assemblies;
d. determining a first flow rate of steam through each of said fuel nozzle assemblies;
e. inserting a meterplate into each of said fuel nozzle assemblies at said steam inlets, each meterplate having a metering hole with an effective flow area that depends on said first flow rate, wherein said metering hole restricts the flow of steam thereby creating a pressure drop and resulting in equivalent steam flow to all nozzle assemblies;
f. determining a second flow rate of steam through each of said fuel nozzle assemblies to verify equivalent steam flow to all nozzle assemblies.
2. The method of claim 1 wherein said metering hole in said meterplate increases said pressure drop across said fuel nozzle by a factor of approximately two.
3. A combustion system for a gas turbine engine comprising:
a plurality of combustors;
a manifold containing steam;
a plurality of fuel nozzle assemblies in each of said combustors, each of said fuel nozzle assemblies having:
a first fuel inlet in fluid communication with a first fuel passage and first fuel injection means for supplying a first fuel to a combustor;
a steam inlet in fluid communication with a steam passage and steam injection means for supplying steam to a combustor;
an air passage and air injection means for supplying air to a combustor;
means to flow steam from said manifold to each of said fuel nozzle assemblies;
a meterplate in each of said fuel nozzle assemblies at said steam inlets, each meterplate having a metering hole with an effective flow area that restricts the flow of steam therethrough; each meterplate being sized for equivalent steam flow to all nozzle assemblies;
wherein the effective flow area of at least one of said metering holes is greater than at least one of the other metering holes.