Axial Swirler Monotonic Discharge Flow Angle
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Solution Overview
Problem
Conventional axial swirlers in gas turbines face challenges with high energy losses due to unfavorable pressure drops, wakes, and recirculation regions, which affect mixing homogeneity and stability, leading to inefficient combustion and increased NOx emissions.
Innovation Solution
The design of an axial swirler with monotonically increasing discharge flow angles, defined by the function tan(α) = K * R^β + H, where β ranges from 1 to 12, and constants K and H are chosen to achieve a low swirl number of approximately 0.4, allowing for efficient mixing with reduced pressure drops and improved flame stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional axial swirlers are used, then mixing is achieved, but high pressure drop causes unfavorable energy loss
Solution Approach 1:
The patent applies parameter changes by optimizing the discharge flow angle distribution across the swirler radius. Specifically, the discharge flow angle is set to increase monotonically from the inner radius to the outer radius, creating a tailored swirl number distribution that reduces overall pressure drop while maintaining effective mixing. This parameter optimization resolves the contradiction between energy loss and mixing efficiency.
Solution Approach 2:
The patent implements local quality by varying the discharge flow angle locally across different radial positions. The inner region has a smaller discharge flow angle while the outer region has a larger angle, creating localized flow characteristics that optimize mixing at each radius while minimizing total energy loss. This local differentiation allows the system to achieve mixing effectiveness without uniform high pressure drop across the entire swirler.
2Stability of the object's composition
If high swirl number is used for good air-fuel mixing, then mixing homogeneity improves, but wakes and flow-separation regions appear at fuel injection location
Solution Approach 1:
The patent changes the swirl number parameter from a uniform high value to a radially varying distribution. By setting the discharge flow angle to increase monotonically from inner to outer radius, the swirl number becomes lower at the fuel injection location (inner radius) and higher at the outer radius. This parameter transformation maintains overall mixing homogeneity while eliminating flow separation at the critical fuel injection zone.
Solution Approach 2:
The patent applies local quality by differentiating the swirl characteristics at the fuel injection location from the rest of the swirler. The discharge flow angle is specifically optimized at the inner radius where fuel is injected, creating a local flow environment that prevents wake formation and flow separation, while other regions maintain higher swirl for effective mixing.
3Productivity
If dual annular counter-rotating axial swirlers are used, then mixing is achieved, but radially varying velocity distribution is unfavorable for combustion
Solution Approach 1:
The patent inverts the conventional approach of using counter-rotating swirlers by employing a single swirler with a monotonically increasing discharge flow angle. Instead of creating opposing rotational flows that produce complex radially varying velocity distributions, this inverted approach uses unidirectional swirl with varying angle, achieving mixing capability while maintaining more favorable velocity distribution for combustion.
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 achieves high mixing homogeneity with minimal pressure drop, enhancing gas turbine efficiency, fuel capability, and reducing NOx emissions by promoting shearing radial profiles and two-side fuel injection, resulting in improved aerodynamics and compact burner design.
Implementation Method 1
producing an increased mixing homogeneity and stability for a given gas pressure drop over the swirler
Implementation Method 2
The larger is the swirl number, the larger is the pressure drop entailing an unfavorable energy loss
Data Source
Figure 1~2
Figure 3(a)~4(b)
Figure 5~7(b)
AI summary
The present invention relates to an axial swirler (43), in particular for premixing of oxidizer and fuel in gas turbines. The swirler comprises (43) a series of swirl vanes (3) with a streamline cross-section, wherein each swirl vane (3) has a leading edge (38), a trailing edge (39), and a suction side (31) and a pressure side (32) extending each between said leading and trailing edges (38,39). The swirl vanes (3) are arranged around a swirler axis (47), wherein said leading edges (38) extend essentially in radial direction. Flow slots (33) are formed between the suction side (31) of each swirl vane (3) and the pressure side (32) of its nearest neighboring swirl vane (3). Furthermore, at least one swirl vane (3) has a discharge flow angle between a tangent to its camber line at its trailing edge (39) and the swirler axis (47) that is monotonically increasing with increasing radial distance from the swirler axis (47). The invention also relates to a burner with such a swirler and a method of operating said burner.