Fluidic Switching Element for Annular Swirl Impingement Cooling
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Solution Overview
Problem
Existing impingement cooling configurations in turbomachines face challenges in generating pulsating cooling air with high amplitudes and frequencies required for effective Strouhal numbers, making it difficult to achieve high convective heat transfer, especially in thermally stressed turbine components.
Innovation Solution
A fluidic switching element with external control means alternately directs cooling gas into output branches, generating pulsating impingement jets with a defined Strouhal number range of 0.2 to 2.0, forming ring vortices without interrupting the main cooling mass flow, using a control mass flow to achieve high amplitude and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If active actuators or siren-like components are used to generate pulsating cooling air in laboratory experiments, then high amplitude and frequency pulsations are achieved, but device size, weight, and complexity increase making them unsuitable for turbomachinery
Solution Approach 1:
The cooling air supply system itself generates the required pulsations through its own flow dynamics and interaction with the turbine component geometry, eliminating the need for separate active actuators. The system uses the kinetic energy and flow characteristics of the cooling air to create ring vortices and pulsations automatically, making the cooling medium serve dual purposes: cooling and pulse generation.
Solution Approach 2:
The invention uses pneumatic principles by utilizing the pressurized cooling air flow to generate pulsations through fluid dynamic interactions. The cooling air itself, when directed through specific geometries and interacting with the turbine component surfaces, creates self-sustaining pulsating flows and ring vortices without mechanical actuators, leveraging gas dynamics to achieve the desired effect.
2Device complexity
If passive methods such as Karman vortex nozzles are used to generate pulsations, then device complexity is reduced, but sufficient amplitude in the desired Strouhal number range cannot be achieved
Solution Approach 1:
The invention changes the flow parameters of the cooling air, specifically utilizing high velocity and appropriate pressure conditions to generate sufficient pulsation amplitude. By optimizing the cooling air supply parameters (velocity, pressure, flow rate) and the interaction geometry with turbine components, the system achieves the required Strouhal number range and convective heat transfer enhancement without complex passive devices.
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 solution enables efficient impingement cooling by creating ring vortices with high amplitude and frequency, enhancing convective heat transfer without the need for active interruption mechanisms, suitable for use in turbomachines.
Implementation Method 1
External control means are provided that control the cooling gas flowing in the inlet branch at a junction such that the cooling gas is directed into only one of the outlet branches at any given time
Implementation Method 2
a pulsating supply of cooling air generates ring vortices, depending on the pulsation frequency and amplitude, which enclose cooling fluid in their core and transport it from the nozzle outlet to the impact plate to be cooled
Implementation Method 3
The periodic occurrence of the ring vortices leads to a periodic renewal of the fluid and temperature boundary layer. Depending on the vortex frequency and amplitude, respectively, The resulting vortex strength from these values can lead to reductions or increases in convective heat transfer
Implementation Method 4
This switching element has an inlet branch and at least two outlet branches located downstream of the inlet branch. External control means are provided that control the cooling gas flowing in the inlet branch at a junction such that the cooling gas is directed into only one of the outlet branches at any given time
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a device and a method for generating an impact jet (P) forming a ring vortex (7). The device comprises at least one fluidic switching element (1, 1') which has: an inlet branch (2) with an inlet opening (21) through which cooling gas (G) can be supplied to the fluidic switching element (1); at least two outlet branches (31, 32) which are formed downstream of the inlet branch (2) and which each terminate in an outlet opening (8); a junction (4) at which the inlet branch (2) divides into the at least two outlet branches (31, 32); and control means (31, 32, S) for controlling the cooling gas (G) flowing in the input branch (2) such that the cooling gas (G) is alternately directed into one or the other of the output branches (31, 32), whereby a pulsating impact jet (P) with a frequency (f) is generated in each output branch (31, 32).The fluidic switching element (1) is designed and configured to discharge cooling gas at the outlet openings (8) with a mean outflow velocity (u) and a frequency (f) such that the impact jet (P) exiting the outlet openings (8) forms annular vortices (7). The invention further relates to a turbomachine with such a device.