Purge system for dual-fuel gas turbine engine
A dual-fuel turbine engine is a type of turbine engine that can operate using two different fuel sources, such as liquid fuel (e.g., diesel) and natural gas. For liquid fuels, the turbine engine includes a primary line to facilitate engine startup and a secondary line to modify power output. Generally, the turbine engine only uses one type of fuel for combustion at a time. The fuel lines and passages in the fuel nozzles that carry the unused fuel source should preferably be purged and sealed by a purging system to reduce coking. However, conventional purge systems typically purge and seal only the secondary line for liquid fuels. As a result, the passages in the fuel nozzles connected to the primary line are prone to coking. To address this problem, a purge system is disclosed that purges and seals the primary line and, optionally, the secondary line.
1 . A dual-fuel turbine engine configured to receive liquid fuel and natural gas, wherein, during operation of the dual-fuel turbine engine, only one of the liquid fuel or the natural gas is used for combustion and the dual-fuel turbine engine is further configured to switch between the liquid fuel and the natural gas, the dual-fuel turbine engine comprising:
a fuel manifold having a first passage to carry a first portion of the liquid fuel, a second passage to carry a second portion of the liquid fuel, and a third passage to carry the natural gas;
a natural gas intake system, fluidically coupled to the fuel manifold, to provide the natural gas;
a liquid fuel intake system to provide the liquid fuel;
a primary line network, fluidically coupled to the liquid fuel intake system and the fuel manifold, to carry the first portion of the liquid fuel;
a secondary line network, fluidically coupled to the liquid fuel intake system and the fuel manifold, to carry the second portion of the liquid fuel; and
a purge system, fluidically coupled to the primary line network, the secondary line network, and the third passage, to continuously provide a purging fluid, the purge system comprising a purge dividing fitting fluidically coupled to a primary liquid fuel dividing fitting of the primary line network and to a secondary liquid fuel dividing fitting of the secondary line network,
wherein when the natural gas is used for combustion, the purge system flows the purging fluid through the first passage via the primary line network and the second passage via the secondary line network simultaneously; and
wherein when the liquid fuel is used for combustion, the purge system flows the purging fluid through the third passage.
2 . The dual-fuel turbine engine of claim 1 , wherein:
the primary liquid fuel dividing fitting comprises a first port, a second port, a third port, and a fourth port;
the primary line network further comprises:
a first primary line fluidically coupled to the liquid fuel intake system and the first port of the primary liquid fuel dividing fitting; and
a second primary line fluidically coupled to the second port of the primary liquid fuel dividing fitting and the fuel manifold;
the third port of the primary liquid fuel dividing fitting is fluidically coupled directly to the fuel manifold; and
the purge dividing fitting is fluidically coupled to the fourth port of the primary liquid fuel dividing fitting.
3 . The dual-fuel turbine engine of claim 1 , wherein the purge system comprises:
a valve fluidically coupled to a purge source, the first passage, the second passage, and the third passage; and
a switch, operably coupled to the valve, to actuate the valve in response to a signal from a control system of the dual-fuel turbine engine.
4 . The dual-fuel turbine engine of claim 1 , wherein the purge system is configured to flow the purging fluid at a pressure of about 200 psig to about 250 psig.
5 . The dual-fuel turbine engine of claim 4 , wherein the purge system is configured to flow the purging fluid at a flow rate equal to or greater than 3 standard cubic feet per minute (SCFM).
6 . A method of operating a dual-fuel turbine engine configured to receive liquid fuel and gaseous fuel, the dual-fuel turbine engine comprising:
a fuel manifold having a first passage to carry a first portion of the liquid fuel, a second passage to carry a second portion of the liquid fuel, and a third passage to carry the gaseous fuel,
a primary line network connecting a liquid fuel source to the first passage of the fuel manifold via a first passage,
a secondary line network connecting the liquid fuel source to the second passage of the fuel manifold via a second passage, and
a gaseous fuel intake system connecting to the third passage of the fuel manifold via a third passage, and
a purge system fluidly coupled to the primary line network, the secondary line network, and the third passage and comprising a purge dividing fitting fluidically coupled to a primary liquid fuel dividing fitting of the primary line network and to a secondary liquid fuel dividing fitting of the secondary line network,
the method comprising:
supplying the first portion of the liquid fuel from the liquid fuel source to the first passage of the fuel manifold via the primary line network and the first passage to facilitate startup of the dual-fuel turbine engine;
supplying the second portion of the liquid fuel to the second passage of the fuel manifold via the secondary line network and the second passage to fuel the dual-fuel turbine engine;
switching from the liquid fuel to gaseous fuel for fueling the dual-fuel turbine engine; and
continuously flowing a purging fluid through the first passage via the purge dividing fitting and the primary liquid fuel dividing fitting of the primary line network and through the second passage via the purge dividing fitting and the secondary liquid fuel dividing fitting of the secondary line network while fueling the dual-fuel turbine engine with the gaseous fuel from the gaseous fuel intake system via the third passage that receives the gaseous fuel from the gaseous fuel intake system; and
continuously flowing the purging fluid through the third passage when the liquid fuel is used for combustion.
7 . The method of claim 6 , wherein flowing the purging fluid through the first passage and the second passage occurs simultaneously.
8 . The method of claim 6 , further comprising: flowing the purging fluid through the first passage and the second passage at different flow rates and/or different flow pressures while fueling the dual-fuel turbine engine with the gaseous fuel.
9 . A dual-fuel turbine engine comprising:
a fuel manifold to combust liquid fuel or gaseous fuel;
a liquid fuel intake system, in fluid communication with the fuel manifold, to supply a first portion of the liquid fuel to the fuel manifold via a first liquid fuel dividing fitting and a first passage of the fuel manifold for start-up of the dual-fuel turbine engine and to supply a second portion of the liquid fuel to the fuel manifold via a second liquid fuel dividing fitting and a second passage of the fuel manifold for powering the dual-fuel turbine engine;
a gaseous fuel intake system, in fluid communication with the fuel manifold, to supply the gaseous fuel to the fuel manifold via a third passage of the fuel manifold; and
a purge system, in fluid communication with the fuel manifold, to continuously purge (i) the first passage via a purge dividing fitting fluidically coupled to the first liquid fuel dividing fitting and (ii) the second passage of the fuel manifold with purging fluid via the purge dividing fitting and the second liquid fuel dividing fitting while the gaseous fuel intake system supplies the gaseous fuel to the fuel manifold via the third passage of the fuel manifold and to continuously purge the third passage of the fuel manifold with the purging fluid while the liquid fuel intake system supplies the first portion of the liquid fuel to the fuel manifold via the first passage and the second portion of the liquid fuel to the fuel manifold via the second passage.
10 . The dual-fuel turbine engine of claim 9 , wherein the purge system comprises:
a valve configured to connect to a purge source; and
a switch, operably coupled to the valve, to actuate the valve in response to a signal from a control system of the dual-fuel turbine engine.
11 . The dual-fuel turbine engine of claim 9 , wherein the purge system is configured to flow the purging fluid through the first passage and the second passage at different flow rates and/or different flow pressures while the gaseous fuel intake system supplies the gaseous fuel to the fuel manifold via the third passage of the fuel manifold.
12 . The dual-fuel turbine engine of claim 9 , wherein the first liquid fuel dividing fitting is a four-port fitting.
13 . The dual-fuel turbine engine of claim 9 , wherein the purge system is configured to flow the purging fluid at a pressure of about 200 psig to about 250 psig.
14 . The dual-fuel turbine engine of claim 13 , wherein the purge system flows the purging fluid at a flow rate equal to or greater than 3 standard cubic feet per minute (SCFM).