Gas Turbine Combustor Bleed Duct for Diffuser Boundary Layer Control
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Solution Overview
Problem
Conventional gas turbine diffusers are limited by their short length due to packaging constraints, leading to inefficiencies and increased nitrogen oxide emissions, as they often bleed air downstream, which reduces engine performance and increases pollution.
Innovation Solution
A gas turbine system that includes a diffuser, a fuel nozzle, and at least one bleed duct to direct bleed air from downstream of the combustor to the fuel nozzle, enhancing diffuser efficiency and reducing emissions by using the bleed air for premixing with fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diffuser length is reduced to meet packaging constraints, then engine size and weight are reduced, but diffuser performance deteriorates and combustion efficiency decreases
Solution Approach 1:
A bleed air injection system is introduced as an intermediary mechanism to enhance diffuser performance. Bleed air is injected at the diffuser throat to energize the boundary layer, preventing flow separation and maintaining effective diffusion in a compact diffuser, thus resolving the contradiction between short diffuser length and adequate diffusion performance
Solution Approach 2:
The system changes the flow parameters by injecting high-energy bleed air into the diffuser throat region. This parameter change energizes the boundary layer and prevents separation, allowing the diffuser to maintain effective performance despite its reduced length, thereby resolving the contradiction between compact size and diffusion efficiency
2Productivity
If bleed air is extracted downstream of the combustor, then diffuser performance can be enhanced, but engine performance decreases and nitrogen oxide emissions increase
Solution Approach 1:
Bleed air is extracted and injected into the diffuser throat upstream of the combustor, performing the boundary layer energization action before combustion occurs. This preliminary action prevents flow separation in the diffuser while avoiding the introduction of additional oxygen into the combustion zone, thus improving diffuser performance without increasing nitrogen oxide 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 configuration improves engine efficiency, decreases nitrogen oxide emissions, and optimizes diffuser performance by utilizing bleed air for fuel premixing, while minimizing packaging space and avoiding downstream air injection.
Implementation Method 1
a diffuser that decelerates the air emitted from the compressor prior to the air entering the combustor
Implementation Method 2
bleeding air from the air stream near the diffuser throat to energize the air flow near the diffuser wall and prevent separation of the flow from the wall
Implementation Method 3
utilizing bleed air for fuel premixing
Data Source
AI summary
A gas turbine system includes a compressor operative to output an airstream and a diffuser having an inlet to receive the airstream and an outlet to output the airstream. The outlet has an area larger than the inlet to diffuse the airstream. The gas turbine system also includes a fuel nozzle operative to receive fuel and emit the fuel in a combustor and at least one bleed duct having an inlet between the compressor and the outlet of the diffuser. The at least one bleed duct is operative to direct bleed air from downstream of the compressor to the fuel nozzle.