| 摘要 |
The invention relates to an air purge system for preventing coke buildup in gas turbine engine fuel injectors, and in particular in the relatively small orifice pressure atomizers of a primary fuel injector. The inventors have recognized that after engine shutdown, residual engine heat is sufficient to cause fuel on wetted surfaces of the injectors to decompose and deposit coke. Especially critical are small orifices in injectors positioned towards the upper side of an engine, since rising hot gases accumulate and heat the upper engine area significantly for a long period after engine shutdown. Coke buildup leads to narrowing of the fuel injector orifices, and without adequate maintenance leads to uneven burning and eventually can incapacitate the engine. Fuel injectors are often located in relatively inaccessible interior portions of the engine. Extending the service life of an injector can result in significant maintenance cost savings and engine downtime. The air purge system is activated on engine shutdown to continuously exhaust cooling air through the injector orifices for an extended purge period after shutdown, for example 1-1.5 hours. A battery operated air blower connected to the fuel line forces cooling air through the injector until a thermocouple switch deactivates the blower on sensing an injector temperature below 150 DEG F. At this low temperature, coke formation does not occur and during engine operation efficient combustion minimizes coke formation. The invention provides the following benefits: (1) fuel is completely purged over an extended period from the injector; (2) backflow of combustion gases into the injector is impeded by continuous positive pressure and air flow out of the injector; (3) the fuel wetted surfaces of the injectors are more completely dried after long term exposure to purging air flow; and (4) the injectors are air cooled after engine shutdown to maintain injector temperature below the temperature at which coke formation will occur.
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