Supersonic Turbine Moving Blades for Shock-Wave Loss Reduction
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Solution Overview
Problem
As the annular band area and blade length or average diameter increase in axial-flow turbines, the moving blade relative inflow velocity becomes supersonic, leading to shock wave loss and entropy rise, which can reduce the work output despite increased flow rate.
Innovation Solution
Designing the turbine moving blades with supersonic turbine airfoils featuring a blade exit angle oriented in the axial direction, an expanded flow passage, and continuous curvature leading edges to reduce shock wave intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the blade length or average diameter is increased to increase the annular band area and flow rate, then the work output per stage can be increased, but the moving blade relative inflow velocity becomes supersonic causing shock wave loss
Solution Approach 1:
The patent applies different design characteristics to different parts of the moving blade: the leading edge portion has a specific curvature radius (0.03-0.08 times the blade height) to control shock wave formation, while other portions of the blade maintain conventional design parameters. This localized optimization allows the blade to handle supersonic flow without excessive shock wave loss while maintaining overall blade functionality.
Solution Approach 2:
The patent changes the geometric parameters of the moving blade leading edge, specifically setting the curvature radius of the leading edge portion to 0.03-0.08 times the blade height at the mid-height section. This parameter optimization reduces the intensity of shock waves formed during supersonic flow, allowing the turbine to operate efficiently at higher blade lengths and annular band areas without suffering from excessive shock wave losses.
2Loss of energy
If the stationary blade outer peripheral shape is designed to prevent supersonic flow, then shock wave loss is reduced, but it becomes difficult to suppress shock wave loss when blade length is further increased
Solution Approach 1:
Instead of trying to prevent supersonic flow conditions through stationary blade design (as in conventional approaches), this patent accepts supersonic flow as inevitable for lengthened blades and directly addresses the problem by optimizing the moving blade leading edge geometry to minimize shock wave losses. This inverted approach shifts the solution from flow control to shock wave mitigation.
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
The solution effectively minimizes shock wave loss and entropy rise, ensuring efficient energy conversion by maintaining supersonic flow conditions without significant pressure drops.
Implementation Method 1
the velocity of a fluid flowing to the moving blade relative to the moving blade becomes supersonic, which may cause shock wave loss in the inflow area of the moving blade
Implementation Method 2
a flow expands in a flow passage between neighboring blades
Data Source
Figure 1
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Figure 4
AI summary
A supersonic turbine moving blade (12a) in which increased circumferential speed due to increased blade length and average diameter reduces shock wave loss in its inflow area. It has at least one of the following features: pressure surface curvature is nonnegative from the leading to trailing edge end (1TE) ; negative pressure surface curvature is positive upstream and negative downstream; dimensionless pressure surface curvature (inter-blade pitch divided by curvature radius) is larger than 0.0 and smaller than 0.1 in the 30%-to-60% portion of the length along the pressure surface; the leading edge part is formed by continuous curvature curves and the distance between 1/2 point of the blade maximum thickness and leading edge end (4) exceeds 1/2 of the maximum thickness; the exit angle (ang2) is larger than a theoretical outflow angle; and the maximum thickness point (101) is nearer to the trailing edge (1TE) than to the leading edge (1LE) with an expanded inter-blade flow passage formed with a throat as the entrance.