Combustor Liner Cooling with Accelerating Channels
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Solution Overview
Problem
Prior gas turbine engine combustor designs face challenges in reducing NOx emissions while maintaining effective cooling, as aggressive tapering in convergent sections can lead to entrainment of cooling flow, increasing flame temperatures and NOx formation.
Innovation Solution
The design adjusts the pressure drop between impingement and effusion holes to a 50:50 ratio, incorporates chevron trip strips for turbulence, accelerating channels, pedestals for enhanced heat transfer, and frusto-conical effusion holes to optimize cooling airflow and reduce interaction with the fuel-rich zone, thereby balancing cooling capability and NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If aggressive tapering of the convergent combustion chamber section is used to increase combustion flow velocity and reduce residence time, then NOx formation is reduced, but cooling flow is entrained into the fuel-rich zone causing flame temperatures to increase and NOx formation to increase
Solution Approach 1:
The patent applies different geometric profiles to different zones of the combustion chamber. The divergent section uses a specific taper angle while the convergent section uses a different profile, optimizing each zone's function. This local differentiation allows the convergent section to accelerate flow without excessive entrainment, and the divergent section to properly expand gases, resolving the contradiction between flow velocity enhancement and cooling flow protection
Solution Approach 2:
The patent optimizes specific geometric parameters including the divergent section angle (5-15 degrees), convergent section angle (10-20 degrees), and the position of the throat section. By carefully controlling these parameters, the design achieves sufficient flow acceleration for NOx reduction while maintaining proper flow separation to prevent cooling air entrainment, thus balancing temperature control with emission reduction
2Reliability
If more cooling air is provided to enhance serviceable life of the engine, then cooling capability is improved, but more cooling air may be entrained into the combustion chamber increasing flame temperatures and NOx production
Solution Approach 1:
The patent incorporates trip strips at the entrance to the convergent section that preliminarily condition the cooling flow before it reaches the critical zone. These trip strips create controlled turbulence and boundary layer separation that prevents the cooling air from being drawn into the fuel-rich zone, allowing adequate cooling to be provided without the harmful entrainment effect
Solution Approach 2:
The patent uses the trip strips as an intermediary element between the cooling air supply and the combustion chamber. These strips mediate the interaction by creating a controlled flow pattern that allows cooling air to be provided for reliability while preventing it from directly entering the fuel-rich zone, thus resolving the contradiction between cooling capability and NOx emissions
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 approach effectively decreases cooling flow into the combustion chamber, reducing NOx production and maintaining adequate cooling of the combustor liner, leading to lower combustion temperatures and improved exhaust dilution.
Implementation Method 1
an accelerating channel bounded by a ceiling and a floor. The ceiling and the floor are tapered to thereby define a cross-sectional area that decreases in the direction of cooling airflow from the impingement holes to the effusion holes
Implementation Method 2
at least one trip strip disposed on the cold surface
Implementation Method 3
Cooling air is forced through these flow cavities and into the combustion chamber, creating a cooling film on hot surfaces of the liners
Implementation Method 4
The inner and outer liners are separated by and define a combustion chamber. Flow cavities are typically provided between each pair of shells and liners
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A combustor liner which reduces cooling flow to a combustion chamber and augments pressure drop split between impingement holes and effusion holes is disclosed. The combustor liner may further include accelerating channels, trip strips, pedestals, and cone-shaped effusion holes to provide further cooling of the liner. The combustor liner may reduce NOx production and the temperature of the combustion chamber of a gas turbine engine or the like.