Passive purge injectors

Abstract

A method of injecting fuel in a gas turbine engine includes injecting gaseous fuel from a gaseous fuel circuit of an injector in a first mode, wherein flow of gaseous fuel from the gaseous fuel circuit constricts air flow from an air circuit. The method includes injecting liquid fuel from a liquid fuel circuit in a second mode, idling flow in the gaseous fuel circuit and flowing air through the air circuit for passive purge to prevent liquid fuel from migrating into the gaseous fuel circuit. The method includes injecting a gaseous fuel that lies within a range of different Wobbe Index values, wherein regardless of where the gaseous fuel falls in the range, it does not prevent operation in the first and second modes as described above.

Description

BACKGROUND OF THE INVENTION1. Field of the Invention[0001]The present disclosure relates to injectors, and more particularly to multiple circuit injectors with passive purge for inactive circuits.2. Description of Related Art[0002]Dual-fuel gas-turbine fuel injectors often require active purging of the idle fuel circuit with air in order to prevent unwanted fouling and liquid fuel collecting in the idle gas circuit. This active purging requires costly additional subsystems, which can also add a parasitic efficiency loss to the engine. Passive-purge concepts have been used to obviate the need for active purging; however, traditional passive-purge injectors only function for a relatively narrow range of Wobbe Index fuels around the design point. The Wobbe Index is a way of comparing energy density of one fuel to another, and varies proportionally with calorific value and inversely with the square root of specific gravity. For a given energy output requirement, a fuel with a higher Wob...

AI Technical Summary

Benefits of technology

The patent text describes a gaseous fuel circuit for an engine that prevents liquid fuel from migrating into the gaseous fuel circuit and growing carbon on a conical surface of a liquid injector inboard of the gaseous flow circuit. The fuel injecting arrangement includes a gaseous fuel outlet and a liquid fuel outlet positioned radially of each other, and an air outlet positioned radially of the gaseous fuel outlet. When gaseous fuel is flowing out of the gaseous fuel outlet, air flows through a confined air circuit to prevent liquid fuel from settling on the gaseous fuel outlet or back flowing into the gaseous flow circuit. This arrangement ensures that engine performance is not compromised while using both gaseous fuel and liquid fuel.

Problems solved by technology

This active purging requires costly additional subsystems, which can also add a parasitic efficiency loss to the engine.

Passive-purge concepts have been used to obviate the need for active purging; however, traditional passive-purge injectors only function for a relatively narrow range of Wobbe Index fuels around the design point.

If gaseous fuel is used with a Wobbe Index value sufficiently lower than the design point for a given traditional passive purge injector, then the gaseous fuel will tend to backflow into the diffuser cavity and lead to possible engine damage.

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