Hydrogen Combustor Mixing Passages for Flashback Prevention
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Solution Overview
Problem
The use of hydrogen as a fuel in gas turbine engines poses challenges due to its gaseous state and higher flammability, which can lead to flashback issues if the local flame speed exceeds the fuel-air mixture inlet speed, particularly in combustor structures designed for liquid aviation fuel.
Innovation Solution
A combustor design incorporating a liner with a fuel and air mixing body, featuring an open fuel plenum and mixing passages with downstream passage sections and a porous metal foam or cellular metallic material to delay ignition and prevent flashback, using hydrogen as a fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a combustor structure designed for liquid aviation fuel is used with gaseous hydrogen fuel, then the combustor can operate with traditional fuel designs, but flashback occurs because the local flame speed exceeds the fuel-air mixture inlet speed
Solution Approach 1:
The patent employs porous metal foam or cellular metallic material within the combustor structure to create a distributed combustion environment. The porous structure provides numerous small channels that increase the surface area for combustion while maintaining a pressure drop that keeps the fuel-air mixture inlet speed higher than the local flame speed, thereby preventing flashback while enabling hydrogen combustion
Solution Approach 2:
The patent modifies the combustor design parameters specifically for gaseous hydrogen fuel by adjusting the fuel-air mixture velocity, pressure drop across the combustor, and ignition energy requirements. These parameter changes ensure that the inlet speed exceeds the flame speed throughout the combustor length, preventing flashback while maintaining stable combustion
2Reliability
If the fuel-air mixture velocity is increased to prevent flashback, then flashback is prevented, but stable combustion becomes difficult to maintain
Solution Approach 1:
The patent creates different flow and combustion conditions at different locations within the combustor. The porous structure provides zones with varying velocity profiles and residence times, allowing the mixture to maintain stability in regions with lower velocities while preventing flashback in regions where velocities are higher. This spatial variation in local conditions resolves the contradiction between flashback prevention and combustion stability
3Reliability
If a porous metal foam or cellular metallic material is added to delay ignition, then flashback is prevented and combustion is controlled, but the device complexity increases
Solution Approach 1:
The patent combines multiple functions into the porous metal foam or cellular metallic material structure. The same material that provides structural support also serves as the combustion medium, heat transfer surface, and flashback prevention mechanism. This merging of functions achieves combustion control without proportionally increasing device complexity
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 design effectively delays ignition and prevents flashback, ensuring safe and stable combustion by controlling the fuel-air mixture exit velocity to be higher than the local flame speed, thus enhancing safety and efficiency in using hydrogen as a fuel.
Implementation Method 1
A forward face of the mixing body is provided with a porous metal foam or cellular metallic material
Implementation Method 2
Fuel openings in the mixing passages to allow fuel to flow from the mixing passage and mix with the air
Implementation Method 3
Compressed air is mixed with fuel and ignited. Products of the combustion pass downstream over turbine rotors
Data Source
AI summary
A combustor for a gas turbine engine includes a liner surrounding a fuel and air mixing body. A fuel supply passage communicates into an open fuel plenum downstream of the fuel supply passage. A wall of the mixing body has air openings to receive air flow, and communicate air into mixing passages. The mixing passages pass through the fuel plenum. Fuel openings in the mixing passages to allow fuel to flow from the mixing passage and mix with the air. There are passage sections extending downstream of the fuel plenum, such that the mixed air and fuel travels downstream of the fuel plenum and into a combustion chamber. A gas turbine engine is also disclosed.