BRAGI'S TECHNOLOGY

Hubless vortex technology turns traditional fan design on it's head. The applications for this type of fan technology are near endless and will positively impact almost every industry market. Just imagine; a safe and silent propulsion solution for electric airplanes and cargo drones. Or hydro propulsion solutions that produce safe and silent outboard boats or trolling motors. Or something that will impact all of us; safe, silent, sustainable and scalable green power generation.

The world is going to be a very different place.

THE GUIDING DESIGN PRINCIPLES OF BRAGI

SAFE

Safety is just one pillar of our design vision from our strong value as viewed from an economically, environmentally, and operational perspective. Our technology is designed upon the premise of no blades or exposed blade tips, all rotating parts are enclosed inside a duct or shroud. Our open core HUBLESS propulsors and power generation technology allows for safe operations and causes less harm and annoyances to the environment.

SILENT

Silent in all spectrums is our goal, whether acoustic, visual, IR, EMI, or Millimeter wave. Our technology by de facto of design allows for very low spectral signatures. Our technologies can be applied for a variety of applications and systems interaction capabilities. We build for total systems integration and elegant solutions to ongoing systemic challenges.

SUSTAINABLE

Sustainability is an integral part of our business – it’s in our DNA. We empower our partners and colleagues to drive sustainable growth and our technologies are designed to elegantly transform their respective industries. We view this as three pillars: economic, environmental, and social and we toil to build sustainable systems.

Our "sustainable development" refers to our specific design and development processes and methods of achieving the unified goal of making innovative solutions that answer the environmental challenge.

SCALABLE

Scalability is one of our unique characteristics, we have built our organization, systems, models, and functions that allows our capability to cope and perform well under an increased and or expanding workload or scope. We have proven that our technology also scales well, and we will be able to increase its level of performance and efficiencies on demand. We build on the hypothesis that as our technology is tested, we will meet the demands of larger and larger operational requirements while not sacrificing our environmental focuses.

CONVENTIONAL HUBBED FANS

How is it done today, and what are the limits of current practice?

Propulsion designs today are generally based on the concept of converting shaft HP into torque (force x moment arm).  The shaft rotates a central hub with airfoils radially attached to it (propeller), to produce thrust. In practice, small shaft diameters result in exceptionally large torques.  Torque levels drive the electric motor chosen, resulting in electric motors that weigh too much and the rapid erosion of the specific power of that motor (HP/lbm or kW/kg).  Trying to counter this degradation of specific power, for any given load (HP or kW), results in an increase in overall system weight, thereby reducing key value metrics such as range, payload, speed and ceiling.

Power generation today also relies on the same torque principle, but in reverse. Air/water flowing onto radial foils converts the stream momentum into pressure, which turns the turbine connected to the motor by a small diameter shaft.  Typical systems must use mechanical gearboxes to step up the rpms from the relatively low speeds of the rotating turbines to very high rpms required by the motor to produce power.

BRAGI HUBLESS FANS

A New approach in quiet aerodynamic design

Moving the motor (from the central shaft) to the rim allows a much longer moment arm, thus for a given power level, much less torque … and it is torque, not specifically power, that drives electric motor efficiencies, overall weight & cost.

Many ‘similar’ rim-driven drives have been constructed to date for use in marine (water) environments. These ‘tunnel thrusters’ have demonstrated improved efficiency, as well as lower costs. While much effort has been spent on hydro-designs, conversion to another fluid (such as air) is merely a matter of proper Reynolds Number scaling. This opens up a plethora of new applications for aircraft that yearn features like safe, silent (24 hour operations), sustainable (green), and supportable (low maintenance & costs).

HOW DOES THIS CHANGE THE GAME?

Potential applications that are enabled are far reaching. Markets include commercial, civil, and military aero & hydro, as well as propulsion & power options. 

To date, aero/hydro solutions are based on technology established long ago, prior to a time where development of rim-drives were prohibitive due to technology, costs, etc. New materials, and massive funds injection into green/electric has mitigated many of the technical risks. This clears a path for a broad new range of applications that were unavailable before. As example: Replace the twin-engines (clean wing, less drag, less energy, less emissions) of a typical airliner, with a single (multi-stage) rotor that mounts externally around a fuselage/empennage such that not only is thrust produced more efficiently (larger mass flow = higher bypass ratio = lower fan pressure ratio = more efficient), but the incoming viscous boundary layer (drag) is ingested then energized (drag à thrust). 

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WHAT ARE THE RISKS?

Rim-drives are still relatively new, and while many exist for hydro (e.g. bow thrustors, pods, etc.) few have delved in how these translate to aerodynamic solutions – as much as Bragi has. Prime risks today fall under technical, budget, schedule, and to some degree – programmatic. Here, we're focusing on the technical aspects.

Electric motor drive. While we have chosen to retain a DC power architecture, AC is not out of the question (especially if there are excessive torque loads which DC would not handle well). Other variables include multi-phase DC up to n-pole arrangements that are controlled by direct voltage, rather than current variations, and may use an advanced form of motor controller based on extremely high speed switching – not available long ago, but there today. Another powerful technology that can offer significant benefit might be to 3D print the entire motor – including wire/coils to insure highly repeatable quality & reproducibility. Another extreme option that fits with 3D printing of entire motor is that of injecting raw magnetic materials such that highly tailored magnetic properties are optimized for best field strengths, with low losses, and for the least weight (to increase a most important electric motor metric of specific power kW/kg).

Electric rim-motor support. Depending on installation, electric motors may require high rpms to produce sufficient power (or torque). In short, rpms can get quite excessive (hundreds of thousands of rpms), and often have to rely on added gearboxes to achieve this. Regular mechanic type bearings (ball, foil, roller) are not capable of these rpms as they simply fail (for many reasons) over short periods of time. This is unacceptable and unsustainable (in terms of maintenance time & costs), as such, we’ve proposed and began explorations of two alternatives to support: (1) air-bearings and; (2) Magnetically levitated bearings. Bragi has already built and spun versions incorporating each of these and will continue to explore optimization, as well as make proper make, buy, build decisions relative to existing industry strengths.

Aero/hydro blade designs for specific applications. Generally, there are a number of valid resources (e.g. computational fluid dynamics, test facilities, literature, etc.) that can be purchased to assess/trade designs. However, many lower fidelity (i.e. fast, simple, inexpensive) tools are simply not capable of analyzing these new & unusual geometric alternatives. Installation variations (and these are many) for this technology have never been explored to either qualify or quantify a wide range of performance metrics (i.e. thrust, drag, torque, noise, etc.).

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DEVELOPMENT BUDGETS

It depends on scale and economies of (production) scale. That said, nothing involved in this quest is ‘unobtanium’, and is fully based on fundamentally understood techniques derived for aero/hydro-dynamics, electric motors, and motor/fan suspension.

DEVELOPMENT SCHEDULE

Of course, this depends on the scope of the project being attempted. Larger and more complex projects will physically take longer. In terms of technology risk reduction, to get to a economically feasible solution, a low fidelity (i.e. tech-demonstrator) could likely be produces on the order of ‘months’ (not decades). Some of the more advanced features (e.g. mag-lev) may take a little longer to perfect, but air-bearings can be made to work soon, or roller/foil bearings used today (on some low performance applications). Additionally, use of off the shelf bearings is also technically possible, but if extremely short life limitations are likely (high rpms heat/fail parts), frequent & mandatory bearing swaps will be necessary until (extremely noisy) bearings can be upgraded to air (quiet), and then to mag-lev (extremely quiet).

SUCCESS MILESTONES

The ability to produce credible aero/hydro designs. This includes: CAD, FEA, Aero/Acoustic footprint, Aero/Hydro-dynamic analysis tools, as well as fine digital renderings (for public).

Choose an application, then design, build, and test it, followed by proof-of-concept validations against low-to-high fidelity analytical/computational models.

Compare fully integrated (into aircraft or watercraft) against ‘conventional’ off-the-shelf offerings and show relative benefits.