Exhaust Gas Recirculation Ejector for Turbine Cooling Efficiency
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Solution Overview
Problem
Gas turbine components are subjected to high temperature flows, leading to undue strain and reduced service life, while using compressor bleed air for cooling reduces system efficiency and output.
Innovation Solution
Implementing an exhaust gas recirculation system with an ejector that compresses cooled exhaust gas using compressor extraction flow to cool the turbine, reducing the need for pressurized air from the compressor and enhancing plant output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If compressor bleed air is used for cooling turbine components, then component service life is extended, but system efficiency and power output are reduced
Solution Approach 1:
An ejector is introduced as an intermediary device between the exhaust gas stream and the compressor bleed air. The ejector mixes exhaust gas with compressor bleed air and delivers the mixture to the turbine, serving as a mediator that enables cooling without directly using compressed air, thus resolving the contradiction between extending component life and maintaining system efficiency
Solution Approach 2:
The system changes the parameters of the cooling air by mixing it with exhaust gas in the ejector. This alters the temperature, pressure, and composition of the air delivered to the turbine, allowing effective cooling while reducing the dependency on pure compressor bleed air, thereby maintaining higher system efficiency
2Power
If higher operating temperatures are used to increase performance and power output, then efficiency and power output are improved, but component strain increases and service life is reduced
Solution Approach 1:
The ejector continuously mixes exhaust gas with compressor bleed air and delivers the mixture to the turbine throughout operation. This continuous action provides sustained cooling that enables the system to operate at higher temperatures for extended periods without compromising component life, thus maintaining both high power output and long service life
3Temperature
If compressor bleed air is used for cooling, then component cooling is achieved, but the amount of pressurized air from the compressor increases
Solution Approach 1:
The system uses the exhaust gas stream itself to provide cooling air through the ejector. The exhaust gas, which would otherwise be wasted, is recirculated and mixed with a portion of the compressor bleed air, allowing the system to cool components using its own exhaust products rather than requiring large quantities of additional pressurized air from the compressor
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
Improves gas turbine performance and extends component life by optimizing cooling and reducing the amount of pressurized air needed from the compressor, while increasing oxygen concentration and decreasing carbon dioxide concentration in the combustion process.
Implementation Method 1
The ejector receives the compressor extraction flow from the compressor, receives the first portion of the cooled exhaust gas stream, compresses the first portion of the cooled exhaust gas stream using the compressor extraction flow
Implementation Method 2
A heat recovery steam generator receives the first exhaust gas stream therein, extracts heat from the first exhaust gas stream
Implementation Method 3
A cooler cools the second exhaust gas stream, thereby defining a cooled exhaust gas stream
Data Source
AI summary
A combined cycle power plant includes a gas turbine engine, which includes a compressor and a turbine. The turbine discharges a first exhaust gas stream therefrom. A heat recovery steam generator receives the first exhaust gas stream, extracts heat from the first exhaust gas stream, and discharges a second exhaust gas stream therefrom. A cooler cools the second exhaust gas stream, thereby defining a cooled exhaust gas stream, and discharges the cooled exhaust gas stream. An exhaust gas recirculation line channels a first portion of the cooled exhaust gas stream towards an ejector. The ejector receives the compressor extraction flow and the first portion of the cooled exhaust gas stream, compresses the first portion of the cooled exhaust gas stream using the compressor extraction flow, and discharges a recovered gas flow to the turbine.