Gas Turbine Combustor Liner Gaps for Controlled Cooling Airflow
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Solution Overview
Problem
Challenging to provide effective cooling air flow to inner and outer liners of a gas turbine engine's combustion section, particularly at attachment locations, due to the use of ceramic matrix composite materials which require precise cooling air distribution.
Innovation Solution
The combustor assembly features a dome and liner design with precise gaps (radial and axial) less than 0.150 inches, allowing controlled airflow through slots defined by the forward and inner surfaces, ensuring efficient cooling airflow to the liners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for inner and outer liners, then temperature resistance is improved, but cooling air flow delivery becomes difficult
Solution Approach 1:
The combustor assembly is divided into distinct functional zones: a primary combustion chamber surrounded by a secondary combustion chamber. The inner liner is segmented into a first liner portion and second liner portion, with the outer liner similarly segmented. This segmentation allows different regions to serve different cooling functions, with cooling air flow paths differentiated between primary and secondary combustion zones, resolving the contradiction by enabling targeted cooling delivery throughout the CMC liner structure.
Solution Approach 2:
A cooling air flow path is introduced as an intermediary channel between the combustion gases and the CMC liners. The cooling air is directed through designated passages to reach the inner and outer liners at their attachment locations to the dome, serving as a mediator that delivers cooling flow to the temperature-resistant CMC materials without direct contact between hot combustion gases and the liners.
2Strength
If liner attachment to dome is made secure, then structural integrity is improved, but cooling air access to attachment areas is reduced
Solution Approach 1:
The design implements local quality differentiation by providing enhanced cooling air flow paths specifically at the attachment areas between liners and dome, while maintaining secure mechanical attachment. The cooling air is directed through localized passages at the attachment locations, ensuring that the structural integrity from secure attachment does not compromise cooling effectiveness, as the attachment regions receive targeted cooling delivery.
3Object-generated harmful factors
If gaps between liner and dome are reduced, then combustion gas leakage is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The gap dimensions between the liner and dome are controlled within specific parameter ranges: radial gaps of 0.010 to 0.030 inches and axial gaps of 0.050 to 0.100 inches. These parameter changes create sufficiently small gaps to prevent combustion gas leakage while remaining manufacturable. The cooling air flow paths are designed to accommodate these controlled gap dimensions, allowing cooling air to reach the liners effectively without requiring ultra-precise manufacturing tolerances.
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 design effectively prevents hot combustion gases from entering the attachment areas, maintaining component integrity and ensuring efficient cooling of the liners, thereby enhancing the operational reliability of the gas turbine engine.
Implementation Method 1
providing the cooling airflow through an axial gap defined between the forward end of the liner and the forward surface of the dome, the axial gap being less than about 0.150 inches. The method also includes providing the cooling airflow through a radial gap defined between the forward end of the liner and the inner surface of the dome
Data Source
AI summary
A combustor assembly for a gas turbine engine includes a dome having a forward surface and an inner surface. The forward surface and the inner surface of the dome at least partially define a slot. The combustor assembly also includes a liner at least partially defining a combustion chamber and extending between an aft end and a forward end. The forward end of the liner is positioned within the slot of the dome. The forward end of the liner includes an axial interface surface and a radial interface surface. The axial interface surface defines a radial gap with the inner surface of the dome and the radial interface surface defines an axial gap with the forward surface of the dome. At least one of the radial gap or the axial gap is less than about 0.150 inches during operating conditions of the combustor assembly to prevent an undesirable airflow.