Gas Turbine Fuel Injector Heat Shield Drip Guard
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Solution Overview
Problem
Fuel injectors in gas turbine engines, particularly those in the lower region oriented upwardly, face issues with carbon deposits due to fuel droplets wetting the heat shield and sliding expansion joints, leading to mechanical failure and increased fuel temperatures, as existing designs are susceptible to fuel penetration through capillary action despite protective measures.
Innovation Solution
A fuel injector design featuring a heat shield with a sliding expansion joint protected by a drip guard, such as a collar, which prevents fuel droplets from reaching the joint, ensuring the sliding interface remains dry and reducing carbon deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a sliding expansion joint is provided in the heat shield to accommodate thermal expansion, then the heat shield can withstand thermal stress, but fuel can penetrate through the joint via capillary action causing carbon deposits and mechanical failure
Solution Approach 1:
A drip guard component is introduced as an intermediary element between the fuel discharge orifice and the sliding expansion joint. This drip guard intercepts fuel droplets that would otherwise reach the joint through capillary action, allowing the joint to maintain its thermal expansion function while preventing fuel penetration and carbon deposit formation.
Solution Approach 2:
The harmful function of the sliding expansion joint (fuel penetration via capillary action) is separated from its useful function (accommodating thermal expansion). The drip guard extracts and removes the fuel droplets before they can enter the joint, allowing the joint to purely perform its thermal expansion accommodation role without the harmful side effect.
2Reliability
If fuel droplets wet the heat shield and sliding joint, then carbon deposits form blocking fuel passages, but adding protective measures increases device complexity
Solution Approach 1:
The heat shield assembly is segmented into distinct functional components: the main heat shield body, the sliding expansion joint, and the drip guard. This segmentation allows each component to perform its specific function independently - the drip guard handles fuel interception while the joint handles thermal expansion - reducing overall system complexity through functional decomposition.
Solution Approach 2:
The drip guard extends the heat shield protection into a new spatial dimension by projecting outward from the main heat shield body. This dimensional extension creates a protective barrier that intercepts fuel droplets in their downward path without interfering with the sliding joint's axial movement, solving the protection problem without complicating the joint's primary function.
3Use of energy by moving object
If the sliding expansion joint is exposed to fuel droplets, then fuel can enter through capillary action increasing fuel temperatures, but protecting the joint requires additional components
Solution Approach 1:
The drip guard serves as a mediator that intercepts fuel droplets before they can reach the sliding expansion joint. By positioning the drip guard in the path of falling fuel droplets, it prevents capillary action from drawing fuel into the joint, thereby maintaining optimal fuel temperatures without requiring complex active temperature control systems.
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
The drip guard effectively prevents fuel from entering the sliding expansion joint, minimizing carbon buildup and maintaining the integrity of the fuel injector components, thereby reducing the risk of mechanical failure and maintaining optimal fuel passage temperatures.
Implementation Method 1
The sliding expansion joint 12 is provided to permit relative movement between the first and second heat shield members in order to accommodate thermal expansion and contraction of the heat shield 11
Implementation Method 2
the fuel droplets falling on the first heat shield member 13 will drain downwardly from the nozzle tip and onto the sliding expansion joint 12
Implementation Method 3
Fuel can then pass through the sliding joint by capillary action and into the cavity 15 defined between the heat shield 11 and the inner fuel supply structure of the nozzle
Implementation Method 4
Fuel is discharged through orifice 8 where an annular film of liquid fuel is formed which is entrained in and atomised by a rapidly moving flow of air exiting the air flow passage 9
Data Source
AI summary
An improved fuel spray nozzle for a gas turbine engine is proposed, in order to address problems associated with the nozzles being wetted with fuel purged from fuel lines upon engine shutdown. The nozzle has a heat shield provided around a fuel discharge orifice, the heat shield incorporating a sliding expansion joint and having a drip collar arranged to cover the expansion joint so as to protect it from being wetted by fuel ejected through the fuel discharge orifice and falling on the heat shield. The fuel spray nozzle is particularly suited to marine or industrial gas turbine engines having a plurality of radially oriented combustion chambers with respective fuel spray nozzles.