Bluff Body Fuel Injector Combustor Acoustic Oscillations
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Solution Overview
Problem
Conventional combustor and fuel injector configurations in gas turbine engines allow the central recirculation zone of gases to re-enter the swirler, causing unsteady heat release and acoustic oscillations, which are not effectively addressed.
Innovation Solution
The design of a fuel injector with a bluff body portion and a tip surface extending parallel to the swirler exit plane, along with a secondary fuel passage and cooling air passage, prevents the central recirculation zone from entering the swirler, reducing acoustic oscillations and thermal stress by creating an anchored flame and thermally insulating the fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional fuel injector configuration is used, then fuel injection function is achieved, but central recirculation zone re-enters the swirler causing acoustic oscillations
Solution Approach 1:
A bluff body is introduced as an intermediary element between the fuel injector and the swirler. This bluff body acts as a mediator that blocks the central recirculation zone from re-entering the swirler, thereby eliminating acoustic oscillations while maintaining fuel injection functionality. The bluff body creates a physical barrier that redirects the recirculating gases away from the harmful interaction zone.
Solution Approach 2:
The fuel injector assembly is segmented into distinct functional zones: the fuel injection component, the bluff body section, and the swirler. This segmentation allows each component to perform its specific function independently, with the bluff body specifically tasked with blocking recirculation zone re-entry, thus solving the acoustic oscillation problem without compromising fuel injection.
2Productivity
If swirler is placed close to fuel injector, then mixing is improved, but unsteady heat release occurs due to recirculation zone fluctuation
Solution Approach 1:
The bluff body serves as an intermediary structure positioned between the fuel injector and the swirler. It maintains adequate spacing to prevent recirculation zone fluctuation from causing unsteady heat release, while still allowing effective mixing to occur in the region downstream of the bluff body where the recirculation zone is stabilized.
3Productivity
If recirculation zone is allowed to re-enter swirler, then combustion mixing is enhanced, but coking occurs on fuel injector
Solution Approach 1:
The bluff body acts as a protective intermediary that blocks the central recirculation zone from直接接触 the fuel injector and swirler components. This prevents coking by eliminating the recirculation of hot gases over these surfaces, while combustion mixing is maintained through controlled turbulence in the region downstream of the bluff body.
4Device complexity
If conventional combustor configuration is used, then结构简单 is maintained, but thermal stress on fuel injector increases
Solution Approach 1:
The bluff body serves as a thermal protective intermediary positioned between the high-temperature combustion zone and the fuel injector. By blocking the recirculation zone from contacting the fuel injector, it significantly reduces thermal stress and coking, thereby extending component life without requiring complex cooling systems or structural modifications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively attenuates acoustic oscillations and reduces thermal stress on the fuel injector, improving combustion stability and efficiency by preventing central recirculation zone re-entry and coking.
Implementation Method 1
A cooling air passage may be provided within the fuel injector and directed to the fuel to thermally insulate the fuel
Implementation Method 2
The tip surface of the bluff body portion extends substantially parallel to a swirler exit plane downstream of a bulkhead in order to prevent a central recirculation zone from entering the swirler
Data Source
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AI summary
A combustor (50) for a gas turbine engine includes a combustion chamber (56) defined between an inner shell and an outer shell. A hood chamber (70) is separated from the combustion chamber (56) by a bulkhead (60) extending between the inner shell and the outer shell. The bulkhead (60) includes at least one opening extending between the hood chamber (70) and the combustion chamber (56). A fuel injector (74) extends through the at least one opening. The fuel injector (74) includes a primary fuel passage (96) including a primary fuel outlet (98) located within the combustion chamber (56). The fuel injector (74) further includes a secondary fuel passage (100) including a plurality of secondary fuel outlets (104) located within the hood chamber (70).