Gas Turbine Exhaust Diffuser Inclined Surface Angle Optimization
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Solution Overview
Problem
In gas turbines, an excessively large angle of inclination of the inner peripheral surface of the outer cylinder in the diffuser can lead to stream separation and vortex generation, impairing the aerodynamic performance and affecting the turbine's performance.
Innovation Solution
The design includes a turbine with a diffuser that has an inner cylinder, an outer cylinder with a first inclined surface forming an angle between 16° and 24°, and struts connecting the cylinders. The last stage rotor vane row has a larger throat width at the end portions compared to the intermediate portion, reducing the likelihood of stream separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the angle of inclination of the inner peripheral surface of the outer cylinder is made large to reduce flow velocity and suppress pressure loss, then pressure loss at the strut is reduced, but stream separation and vortex generation occur which impair aerodynamic performance
Solution Approach 1:
The patent optimizes the angle of inclination of the inner peripheral surface of the outer cylinder to a specific range (16° to 24°) to balance two opposing requirements: reducing flow velocity to suppress pressure loss at the strut, while preventing stream separation and vortex generation that would impair aerodynamic performance. This parameter optimization resolves the contradiction by finding the optimal value that satisfies both conditions.
2Speed
If the angle of inclination is increased to reduce exhaust gas flow velocity upstream of the strut, then pressure loss is suppressed, but the stream cannot follow the surface and separation occurs
Solution Approach 1:
The patent determines the optimal angle of inclination (16° to 24°) as a critical parameter that controls both the exhaust gas flow velocity reduction and stream stability. By setting the angle within this specific range, the patent achieves sufficient velocity reduction to suppress pressure loss while maintaining stream stability to prevent separation and vortex formation.
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 reduces pressure loss in the diffuser, enhances the aerodynamic performance, and improves the overall performance of the turbine and gas turbine by minimizing vortex generation and stream separation.
Implementation Method 1
the velocity of an exhaust gas stream from the turbine is reduced while the exhaust gas stream is passing through the diffuser so that the static pressure is recovered
Implementation Method 2
the stream may not be able to follow the inner peripheral surface, and separation of the stream may cause a vortex to be generated
Data Source
AI summary
A gas turbine includes a turbine rotor, a turbine, and a diffuser defining an exhaust gas flow path. The diffuser has an inner cylinder, an outer cylinder defining the exhaust gas flow path between the outer cylinder and the inner cylinder, and a strut which connects the inner cylinder and the outer cylinder in a radial direction. The outer cylinder has an inclined surface extending outward in the radial direction from an inlet of the exhaust gas flow path toward an outlet of the exhaust gas flow path in an axial direction. The inclined surface defines an angle of 16° to 24° with an axis of the turbine rotor.