Patent Application
20240278263
The present invention relates to the field of fluidic oscillators, and more particularly to a double-sided fluidic oscillator jet.
Background description includes information that will be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Fluidic oscillators are devices that create a pulsating or sweeping motion of a fluid solely based on their internal dynamics without the use of any moving parts. The sweeping pattern produced by a fluidic oscillator is based on the principle of Coanda effect (the action in fluid mechanics whereby a flow along a solid surface tends to follow the curvature of the surface rather than separating) thus making fluidic oscillators to be self-sustained. Fluidic oscillators are preferable for applications including drag reduction, noise control and heat transfer enhancement, due to the unstable character.
Over the last two decades, fluidic oscillators have gain renewed interest through their use as active flow control devices, and this has sparked a broader interest to develop novel devices and explore innovative applications. Fluidic oscillators also have applications in areas such as drag reduction devices, considering the resulting separation bubbles which produce a substantial total pressure loss.
The range of potential applications for fluidic oscillators is rounded off by the topic of air bubble generation. Creating air bubbles with defined diameters is of high interest not only for scientific observations but also for several practical applications such as wastewater treatment or oxygen supply at fish farms. Fluidic oscillators as a self-oscillating impinging jet have demonstrated higher heat transfer rates as it results in even distribution of a pressurized coolant over the target surface. Oscillating or pulsatile fluid flow in many applications have been proven to improve integral quantities such as mass diffusion, skin friction, heat transfer and overall sound pressure level due to interruption of velocity and thermal boundary layer and facilitation of the transition to the turbulent regime. Efficiency of apparatuses utilizing this type of fluid flow has been verified in many industries including controllers, chemicals and processes, medicals, instrumentations, HVAC and recently heat transfer.
Conventional or traditional fluidic oscillators have two feedback loops and an outlet to provide an uniaxially sweeping jet outlet. Fluidic oscillators with zero feedback channels, or so-called feedback-free oscillators are based on two jets colliding within a mixing chamber, which creates an oscillatory outflow direction at the exit of the chamber. Traditionally, a fluidic oscillator configuration using a single exit, was numerically evaluated in 3D at Reynolds 30000 using the SST turbulent model. Two geometry parameters, the mixing chamber inlet and outlet widths were modified, and a significant effect of the flow structure and the feedback channel flow rate was observed when modifying the inlet width, and negligible effects were observed when modifying the outlet width. The output frequency and amplitude effects whenever the (FC) and the mixing chamber (MC) lengths were modified, and it was observed that an increase of the feedback channel length generated no modifications on the output frequency. On the other hand, the increase of the mixing chamber length, generated a clear reduction on the actuator output frequency.
Based on the above, and considering the shortcomings of currently employed fluidic oscillators, there exists a need to develop a new approach to overcome these drawbacks/shortcomings of fluidic oscillators and to display better results.
Aspects of the disclosed embodiments seek to provide a double-sided fluidic oscillator jet, which overcomes the shortcomings of traditionally employed fluidic oscillators.
In accordance with an embodiment of the present invention, a fluidic oscillator is disclosed, comprising a primary feedback loop unit, a secondary feedback loop unit, with two outlets and one inlet; a common mixing chamber; and atleast two perpendicular oscillator jets operating at different oscillation frequencies, producing perpendicular and bi-stable pulsating flow oscillations, simultaneously.
In accordance with another embodiment of the present invention, the fluidic oscillator is a double-sided fluidic oscillator.
In another embodiment of the present invention, the atleast two perpendicular oscillator jets also provide biaxial sweeping jet patterns with vertical (top-bottom) and horizontal (left-right) sweeping range of oscillations, thereby increasing a cooling area coverage.
In another embodiment of the present invention, the primary feedback loop unit comprises atleast two feedback loops.
In another embodiment of the present invention, the secondary feedback loop unit comprises atleast two feedback loops.
In another embodiment of the present invention, the fluidic oscillator further comprises a chevron-shaped design nozzle at the outlet, which assists in achieving a turbulent outlet sweeping pattern, thereby augmenting heat transfer over a target surface.
In another embodiment of the present invention, if the fluidic oscillator comprises two inlets an observation is made that the resulting two incoming fluids from the two different inlets entering the common mixing chamber negates the Coanda effect and thereby creates a steady fluid flow.
As another aspect of the present invention, a method of achieving a wide sweeping pattern and augmenting heat transfer over a target surface using a double-sided fluidic oscillator is disclosed.
The method comprises the steps of switching of fluid between primary and secondary feedback loop units for achieving a biaxial sweeping jet pattern along the target surface, allowing a fraction of the mass fluid flow rate to enter the secondary feedback loop, wherein the primary feedback loop unit produces a horizontal sweeping pattern, and the secondary feedback loop unit produces a vertical sweeping pattern, thereby providing the biaxial sweeping jet patterns via the primary and secondary feedback loop units operating at different frequencies.
Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
The manner in which the above-recited features of the present invention is understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The foregoing and other objects, features and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of preferred embodiments, when read together with the accompanying drawings.
The present invention relates to the field of fluidic oscillators, and more particularly to designing a double-sided fluidic oscillator jet.
The principles of the present invention and their advantages are best understood by referring to
The present invention deals with a modified angled fluidic oscillator producing a double-oscillating jet. A primary feature of the double sided perpendicular fluidic oscillator is to provide biaxial sweeping jet patterns—a horizontally sweeping jet along the target curved surface via a primary oscillating jet, and a vertically sweeping along the target surface axis, via a secondary oscillating jet. In accordance with an embodiment of the present invention, the proposed fluidic oscillator comprises four feedback loops, two outlets, a common mixing chamber, and an inlet.
The present invention focuses on jet flow cooling, and particularly towards the sweeping jet technique using a modified angled fluidic oscillator (double fluidic oscillator jet). The proposed double fluidic oscillator jet provides simultaneously, two perpendicular sweeping jets vertically (up-down motion) and horizontally oscillating (left-right motion) at different frequencies. The invention involves the addition of secondary feedback loops along with primary feedback loops. The working principle involves that a fraction of the mass fluid flow rate enters into the secondary feedback loops which leads to producing a vertical sweeping pattern providing more cooling area at exits with a common mixing chamber. The primary feature of the proposed double oscillating jet—is to provide biaxial sweeping jet patterns including a horizontally sweeping jet along the target curved surface (primary oscillating jet), and a secondary oscillating jet vertically sweeping along the target surface axis. The primary jet sweeping horizontally, meanwhile, the secondary jet sweeping vertically.
Accordingly, to overcome the drawbacks faced by fluidic oscillators in the past, the present invention proposes the addition of atleast one primary feedback loop and atleast one secondary feedback loop for the fluidic oscillator.
In accordance with an embodiment of the present invention, the operating frequencies on the primary jet (high frequency oscillation) and secondary jet (low frequency oscillation), are determined based on the mass fluid flow fraction in each jet. For the same mass flow rate, the single jet oscillates in one direction covering smaller region and a less turbulent flow field compared to the double oscillating jets. In contrast, the proposed double-sided oscillating jet is capable of achieving biaxial sweeping jet outlet via the addition of two feedback loop units and one outlet (normal to the existing feedback loops and outlet). These additional feedback loops with an extra outlet support the movement of the sweeping jet biaxially, thereby covering a broader surface area, creating a more efficient mixing area. The proposed double-fluidic oscillator jet provides two perpendicular sweeping jets vertically (oscillating up-down) and horizontally oscillating (left-right) simultaneously—at different frequencies. The oscillating frequencies depend on the geometry and flow rates. The resulting output jet is a more turbulent outlet due to the resulting sweeping pattern and based on the mass flow fraction of each jet, the primary and the secondary oscillating jet frequencies are determined.
The biaxially sweeping jet coverage covers a wider area of jet impingements compared to the steady and conventional oscillating jet and as a result provides more enhanced heat transfer, mass transfer and mixing performance.
A computational fluid dynamic analysis is performed to support the feature of the double sweeping pattern, wherein both the primary and secondary oscillations were clearly observed which provided a higher cooling area coverage with vertical (top-bottom) and horizontal (left-right) sweeping range of oscillations covering a wider area of jet impingement comparing to single oscillating and steady jets. A number of computational fluid dynamics (CFD) simulations are performed to test the operation of the proposed double side fluid oscillator.
Efficiency of the proposed double-oscillating jet may be enhanced, by introducing a separate inlet which directly feeds into the feedback loops of the secondary jet. The proposed oscillator jet may be used in industrial applications such as in enhancing heat transfer and mass transfer, as well as for the electronic cooling of mass transfer industries.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. The disclosures and the description herein are intended to be illustrative and are not in any sense limiting the invention, defined in scope by the following claims. Many changes, modifications, variations and other uses and applications of the subject invention will become apparent to those skilled in the art after considering this specification and the accompanying drawings, which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications, which do not depart from the spirit and scope of the invention, are deemed to be covered by the invention, which is to be limited only by the claims which follow.
