The Unexpected Genius of Contra-Rotating Propellers

Contra rotating propellers are an ingenious design trick that can improve both the power and efficiency of a propulsion system but why don't we see them everywhere and why might they be making a comeback this Contra rotating airplane propeller does it with ease but the mechanisms behind it are pretty complex the front blade turns anticlockwise and the one behind it clockwise on a single co-axial shaft the question is why a section of this video is sponsored by War Thunder the concept of Contra rotating propulsion is a powerful way of improving efficiency until now they've been used mainly in military applications but recently its combination with another new technology is Making Waves solving one of their biggest problems and potentially enabling us to make use of the benefits they offer in the form of power and efficiency I even had to 3D print one for myself to see it in more detail but more on that later a simple single engine aircraft with a propeller mounted at the front has a few unintended effects when producing forward thrust one of these is due to the torque produced from the spinning blades as you try and take off a propeller spinning clockwise as seen from the cockpit will push the left wheel down into the runway and therefore increase the friction from that wheel the plane will then start to turn left in less Cor corrected by Rudder control once the plane takes to the skies the pilot is then faced with slipstream effects this is where the propeller causes rotational air flow and a spiral forms around the fuselage introducing lateral loads that make the plane want to your left especially at low speeds although these effects are pretty easy for an experienced pilot to control for and are largely mitigated by using multiple engines Engineers of the past thought there was a better solution these are the Contra rotating propellers which solve these challenges and so much more they are mounted in line with each other and spin in opposite directions on the single coaxial shaft they use a gearing system such as Spur Gears or planetary gears here is one I 3D printed to look at closer the top propeller has a shaft which connects through to this bottom bevel gear and the second lower propeller connects to the top bevel gear and because these bevel gears have a middle piece here which is spun using this arm it means that the upper and lower bevel gears spin in opposite directions which therefore spin the blades in opposite directions this does have a useful Mount but I've not quite got this connected together properly so if I put it on it it will all fall apart but hopefully we'll be able to see that when I spin this lever each of the blades spins in opposite direction in sync with one another so so they'll match up here and then as I spin it around they'll match up again and again though I've super glued this and some of the parts didn't print quite properly so is a little bit temperamental but that is a really cool demonstration of a contra rotating propeller system this computer model shows another awesome design for enabling Contra rotating propellers by having three gears at the back and two at the front it flips the direction of the blades because these are all different sizes it then enables it to produce a fluid Contra rotating movement with a one: one turning ratio apart from all these interesting mechanisms the aerodynamics of the Contra rotating propellers is also extremely fascinating by having two propellers spinning in opposite directions you cancel out both the torque and spiraling airflow effects I mentioned earlier as I looked into this further I found that that cancellation of the spiraling effect behind the first propeller is really the the big advantage of this system due to this redirection the air behind the Contra rotating propellers is much more linear and doesn't waste energy by sending it into a spiral this is in part what leads to a 6 to 16% increase in efficiency of Contra rotating propellers compared to a single conventional one this can be seen really well in a video from San Deni comparing unidirectional fans to one with a contra rotating fan setup the flow is so much more directed and therefore more efficient Contra rotating propellers especially excel in highspeed flight because the second propeller is able to re-energize the highly disrupted air flow from the first propeller this could save a lot of fuel for conventional planes or increase the range of electric ones it could also be a solution for applications where there needs to be more thrust but you can't increase the diameter of the propeller without hitting the runway in some applications such as Torpedoes and certain aircraft Contra rotating propellers can also enhance manuverability this is because of the Balan thrust and reduced torque effects that make it easier to control the direction and stabilize the vehicle like so many Innovative Technologies the propeller that I want to show you at the end of this video Builds on so many decades of design but adds a new twist FW Lanchester the grand old man of Aon ntic patented a contra rotating Propeller Way Back in 1907 even older was one for ships patented in 1837 in 1988 a Japanese merchant ship was fitted with a contra rotating propeller system and trial showed an impressive 15% energy saving but although the concept is elegant in principle there are many challenges and applications have remained limited with many in military aircraft only one aircraft provided passenger Services the tupv TU14 this plane was an engineering Masterpiece and surprised the world with its rapid speeds of 540 mph or 870 km an hour it was also incredibly noisy some say 110 DB which meant that passengers had to shout to be heard but why was this the case and how could it be solved before looking at that though there is actually another Contra rotating plane that you can fly in the amazingly immersive game War Thunder whose support helps keep these videos available for free War Thunder has over 2,500 incredibly detailed tanks planes helicopters and ships of 10 big Nations ranging from biplanes and armored cars of the 1920s to fighter jets of today my current favorite has to be the seafire mark 47 you can see how its Contra rotating propeller work in this gameplay video there's an incredible level of realistic detail in the graphics and authentic sound effects place you right in the action join over 70 million players for free on PC Playstation or Xbox every vehicle is modled in incredible detail and there are many different game modes for you to try if you like fast-paced gaming with enhanced vehicle performance there's arcade mode realistic mode balances intensity and authenticity or you could could ramp up all the way for the ultimate Challenge in simulator mode there are countless options for customization including those created by the active and passionate Community it's really easy to use and their in-house 3D engine gives a lag-free experience without a high-end machine sign up using my link which is also down below to enjoy 7 Days of Premium access and if you do it today you'll get a massive Bonus Pack including multiple premium vehicles and an exclusive vehicle decorator now back to the real world why was the El fated t114 so noisy it's all down to the increased mixing of the air flow I found this awesome video that shows all of the tip vortices being formed and colliding in a marine application as you may know these tip vortices coming off the end of the propellers and increased cavitation are a nightmare for noise and excessive wear cavitation is the formation of vapor bubbles in low pressure areas of a liquid which collapse to produce a loud and damaging shock wave however you might be thinking what I was thinking isn't there a propeller that's particularly good at solving these problems a while ago I covered the teral propeller which helps distribute tip voltes and reduce noise in air and water this could be a great way to merge Technologies and it looks like a long-term innovator Greg sharo had the same idea these Contra rotating pidal propellers for boats are designed for greater maneuverability and Agility promising enhanced efficiency its unique design connects two sets of blades to the propeller shaft via smooth elegant curves and twisted surfaces this results in better performance and fuel economy as well as the all important reduction in noise the reduction in noise is mainly due to the lack of tip vortices that SW World from the ends of the propellers which is beautifully shown in the MIT video about their thidal drone propeller this also reduces noise and cavitation in Marine applications which can be seen in the video from sharrow it's amazing to see the Contra rotating propellers and pidal propellers merging together into a low- noise Ultra efficient design with pidal propellers still being the best performing video here on the zeroth channel I honestly think it's genius however as with most things there are some tradeoffs which explain why we aren't seeing these everywhere one of these is of course the mechanical complexity of the gears meaning more cost for manufacturing and maintenance even with shero's Sleek design they are expensive and require extreme consideration to match the perfect propeller with the Boat and Motor combination we're also yet to hear any specific figures from sharo regarding noise and efficiency so I'm eagerly awaiting any results given these challenges will the Contra rotating propeller ever fulfill its full potential of superior efficiency and increased power from what I've seen Marine applications seem to be the biggest use case for these propellers but I'm sure they'll find more applications over time Torpedoes continue to use them and I think some wealthy Boat Owners will definitely be reaping the benefits of shar's new system in the coming years however we still don't have a viable energy saving Contra rotating propeller on a commercial aircraft but given the power and efficiency gains to be had I think there'll be a lot of interest into the future I can't help but think how the complex gear designs of the ones we've seen could be greatly simplified using the wonders of electric propulsion and hub-free Motors maybe that could be a project for a future video I hope you've enjoyed the video if you have please consider subscribing it's free and maybe check out some of my other propeller videos which I think you might like and don't forget to go check out War Thunder Down Below and take advantage of the free bonus pack and as always thanks for watching

Channel: Ziroth

Views: 217,269

Keywords: Science, Engineering, STEM, Electric, Zero, Tesla, News, Research, EV, Battery, propeller, toroidal, boat, plane

Id: 0cVBSt67AcU

Length: 11min 39sec (699 seconds)

Published: Sat Jul 06 2024