@@pork_cake This is why Wankel-Rotary engines should have been used ; they have 1/10 the # of parts , and break much less often . They also produce over twice the hp. as four-stroke engines , per-pound .
@@Prof.Megamind.thinks.about.it. the breaking part is debatable, however if they were used more we definitely could have solved the issues and had extremely reliable, compact, and powerful rotaries.
@@finlaymcdiarmid5832 That may be true , but the airlines require compact power and extreme reliability . Rotaries fit this bill much better than piston-engines .
You completely overlooked the 1910 Coanda plane, using a 4 cylinder engine to drive a fan, with fuel injected and ignited aft of the fan. While it is not clear whether the plane actually flew, it did lead Henri Coanda to note and explore the tendency of the flame to cling to the sides of the fuselage. Now we are well aware of the Coanda effect.
Fuck off coanda didn't do shit in 1910 but a shrouded propeller. After jet power was established, he tried to leech off some relevance by showing clearly more recently fabricated bullshit plans where he added in airstream combustion which he tried to sell as his original plans.
@@EngineeringFun Technically that is not a jet since there was no fuel injection and no high speed thrust generated by thermal cycle...it was a ducted fan + compressor + a nozzle
@@electricaviationchannelvid7863 , @My Opinion Doesn't Matter - It DID have fuel injected in the compressed air volume. Actually that's how the now famous Coanda effect was developed, despite the deflectors near fuselage, the flames licked the fuselage after a certain speed. The numbers if I remember well were 80kg thrust without fuel injection and 220kg with injection (not sure of the precise numbers). The accident in which his jet crashed and burned was because of the unexpected high thrust after the fuel was turned on. The Romanian man was a professional designer with Bristol and not a pilot. He intended to only taxi the plane and didn't know how to pilot a plane. Read about this guy from less biased sources than Wikipedia. I studied him extensively in college and personally saw his creations with detailed blueprints at the Dimitrie Leonida technical museum in Bucharest when I visited as a student. There are many articles and detailed plans about his planes and there is also a motor jet sled he created. There is plenty of misinformation floating around (including from some YT channels!!) because some people who made similar stuff decades later wanted to be first in history books. Just think about this, only 7 years after the Wright brothers' flight with a stick and canvass contraption, at the time when stick and canvas was still state of the art this guy has a plane without any canvas (all mahogany plywood) and without the bracing wires AND with jet propulsion. Gustave Eiffel, the designer of Eiffel Tower, once said about Henri Coanda: “This boy was born 30, maybe 50 years earlier.” adabarbu.medium.com/henri-coand%C4%83-a-romanian-inventor-a8a301162e80
The all first motorjet engine was built by Henri Coanda in 1910: this engine was installed in a monoplane aircraft and tested from Coanda himself: it works well but Coanda was surprised from the power and the plane did crash during take off.Coanda was not seriously injured but did stop the experiences…Coanda had the help from the Gustave Eiffel and the mathematician Henri Painleve…
Coanda said he was distracted by the jet exhaust flow clinging to and charring the mahogany sides of the aircraft fuselage. In his distraction, he fail to notice the wall of the city, Paris, in the airplane's path. Crashing into the city wall resulted in his temporary arrest as an Anarchist Saboteur and being enjoined from involvements with aircraft. His distraction, however, resulted in his first description of laminar flow (Coandă effect) and the founding of the science of fluidics.
@@RealTechZen When I set up a ventilation fan to cool my apartment, I take care that the air-flow runs parallel to the longest wall. A tiny desk-fan keeps a huge apartment feeling light and airy without any drafts. Thank you, Monsieur Coanda!
Very interesting, thank you. The various compound engines in the 40s are really fascinating. But when you look at so much complexity for 12% gain there are many other options.
I think it's funny how people drone on about complexity. The piston engine has soldiered on faithfully in so many apps and for 100 yrs in aircraft. Its numerical parts complexity is now just a given. They can all be made very well and not have to run at their ragged metallurgical edge to get the thermal efficiency; as does a turbine running almost at critical mass and can produce no meaningful power outside of that narrow parameter. On a more red neck note who would NOT want to fly in a Learjet that sounds like two Mclaren F1's in a dead heat either side of your cabin. Pod racers eat your heart out.
but the power to weight ratio of piston engines is shit...... so yeah, you dont have to run them ragged, but even running them ragged, jets still have a better power to weight. so they'll run long enough to get shot down by the faster planes.
so in other words - some of the jets' plusses and all of the piston engine's negatives. Super expensive super complicated and only marginally better in some scenarios. Deadend.
I've been waiting for a video on the VRDK and motorjets in general. I believe if used a little earlier in the war and with more optimization, the tech would have had a nice 3-5yr period of being the best powerplant.
this time flight uploads before i go to work. another good day in the books. but on another note something makes me think these would be deafening.. im getting thunderscreech vibes *edit* 12.5% increase in efficiency 🔥🔥
Rolls Royce’s patent of 1995 has long since expired. If anyone thought there was any merit in the engine they would have done something about it by now. I won’t hold my breath.
@@lordgarion514 Robert, you completely missed the point. The flying wing and its inherent advantages was a dream for Jack Northrop, who died before he saw it come to fruition as computerized flight controls finally overcame some of the challenges the design faced. People told Jack Northrop that it wasn’t possible, the same way the original poster of this thread breezily dismisses the entire concept of a motorjet from his couch.
Imagine a compound cycle engine where the shaft for the compressor and turbine was also the eccentric shaft for a rotary engine sandwiched in between them
When I saw the liquid piston engine, which is an inverted chamber and rotor of the Wankel rotary, I had the same thought. Why not exploit the weight advantage of the rotary and fuel efficiency of the otto cycle engine and produce a general aviation combined cycle engine with low gal/hr consumption under cruise, but high dash speed for fun.
@@electric_boogaloo496 Wankel engines tend to drive efficiency way down due to their elongated, oddly shaped combustion chamber, it behaves roughly like a engine with a very short stroke but wide bore, good for power, bad for efficiency
Or how about one which has two compressors the first a low pressure axial compressor which is powered by the more efficient piston engine (and also acts as a supercharger diverting a little air for the piston engine); and the second (centrifugal or axial) which is powered by a turbine. Perhaps dumping the exhaust of the piston engine into the inlet of the second compressor (the piston engine possibly running slightly fuel rich). Perhaps the combustor-can-flameholder things could run fuel rich to keep the temperature down but the lean air entering the entire combustion chamber would then meet the burning fuel rich air coming out the combustion cans and maybe ignite a secondary combustion? So the entire combustion chamber is burning, but at lower temperature than normal.
This sounds like an interesting engine option to use in a fictional, dieselpunk-themed story setting while also reserving the early turbojet engines as something being experimented on in the background of the said story setting. Said early turbojet research could also be part of a story plot device alongside WW2 research projects like radar, radios, cryptography and early computers, rocketry, etc.
When I was a kid I read a book on building flying model planes (wires only - decades before RC was common.) One design was a model F-86 with a similar set-up turning an internal ducted fan, but without the fire, of course. Woulda made balsa wood planes - interesting.
There are some new exciting developments being researched in rotary engines like the Wankel, and despite being a little less fuel efficient than pistons in their current state, rotaries are much smaller, much less complex. much lighter, and operate at much higher rpms... sounds like a better match for a Motorjet to me! Thanks for the excellent video Flight Dojo!
@@kieranh2005 Yes, when running at a _constant speed_ at their _sweet spot,_ the Wankel is very efficient indeed. They do not like being revved up and down. Mazda's new MX-30 hybrid in January will have a Wankel range extender. It will be easy to convert to hydrogen running. Japan is turning to a hydrogen economy, with hydrogen produced economically by helium gas cooled nuclear reactors.
@@johnburns4017 >They do not like being revved up and down. So they are good in something like a cheap kamikaze drone that flies at constant speed, attacks with quantity and where lower noise is an additional benefit as it reduces detection.
I was thinking the same thing when I saw the title, but Coanda's experiments were more focused on recapturing the excess energy in the exhaust of a piston engine. No reheat, just fully expanding the exhaust. So while the motorjet uses the piston engine to replace the role of the turbine in a jet engine, Coanda used the piston engine to replace the compressor and combustion stages. TLDR: Coanda did the opposite of this, sorta
This looks like one of those times when you have established tech (piston engines) and new advanced tech (jet turbine engines) and there were a few engineers that understood one well and one not so well, and at that point, it was just natural for them to ask "What if?" and experiment. Each engine type has its pros and cons, and its own use and purpose. I call it scientific due diligence is seeing if it was possible to combine the strong points of each type into a single unit. Today, if you look hard enough on RU-vid, you will find the occasional garage guy that took a turbo charger off a car and made a crude but functional jet engine out of it. I think this was a necessary phase of aviation technology we needed to look at, and a part of what makes aviation history so damn cool.
Love your content as always. Just a note on the Russians late start into Jet/Rocket plane development. They did in fact fly the Bereznyak-Isayev BI-1 rocket powered interceptor in May of 42 with some success.
Thanks for this video, there isn't much out there about motorjets. I found them interesting because even today, with modern materials, temperature at the turbine blades is one of the biggest limiting factors in jet performance. Unfortunately, the tradeoffs don't appear to be worth it, and afterburners end up being a better solution for aircraft that need to go that fast. Maybe something will change, between a new interest in supersonic transportation and better battery technology, it might be possible.
From what I know about German engineers, and their love of insanely, needlessly complex and expensive overengineering of simple machines, I'd bet the German engineers watching this video experienced a markedly higher heart rate, increased respiration, and a far higher degree of interest when they saw this video.
And right now someone at BmW is probably feverishly designing a motorjet to fit in their various cars to continue the tradition of needlessly complex, unreliable cars.
10% increase in fuel efficiency is a lot, but i wonder what practical applications this might have for hybrid/electric drives. Electric motors might need less gearing and with many short distance aircraft there might be a sweetspot in between a larger battery and the wight of an electrically driven motorjet to boost range? Kind of like an afterburner for electric aricraft, which would optimally use regenerative fuels or at least fill the gap towards heavier and mid ranged aircraft with better efficiencies? Great video, my jaw dropped when i saw the inline ice which even had enough thrust on its own to power the plane. It's a logic step to use the excess heat but the idea of basically putting an entire engine inside another is really amazing
I honestly never knew about that version of the Ohka. The various Japanese suicide craft have always been of interest to me to the point where one of my cats is named Kaiten, yet I never heard of that version.
@@soggycracker5934 btw, the other cats are Harley aka WaccaCat (wacca is Latin for cow and she is black & white, wacca became vacca in later spoken Latin, you might know it as the root of the word vaccine), Maxwell aka General Taylor (he came with the name Maxwell, combined with my last name and he shares his name with one of the most famous American generals of the 20th century) and Luna the Lunatic (she came with the name Luna the rest is self explanatory). I got Kaiten & Harley as kittens, I adopted Luna & Maxwell from friends who were moving. Also I chose Kaiten because it sounds a lot like 'kitten' & BakaCat is both a nod to a nickname the Ohka apparently had as well as a nod to one of the names I commonly use, bakaman. (which itself is both meant to be amusing as well as being a nod to Socrates when he said that while people think him smart, he really knows nothing.) Yeah, I like to overthink way too many things.
I have seen a homebuilt motorjet. Not based on the Campini design but the Tsu-11, the motorjet from the model 22 Ohka. It uses a McCulloch TC-6150-J-2 turbocharged flat-6 2 stroke engine to drive a similar compressor with side inlets. It is installed in a small plane similar to the model 22 but altered by shortening the nose and installing a fuel tank, and with a V-tail like a Bonanza. It can cruise on the piston engine only and can go exceptionally fast with the jet started. It occasionally appears at the local airport once in a great while. I have no idea about who built it or why, but I've seen it with the tail removed and the engine exposed.
The most practical combustion engine for the Motorjet might be the Wankel! Why?: small size, high rpm and excess burnt oil simply provide extra power to the jet engine stage! Great video!!
My first visit to the Oshkosh convention was in 1974 and I recall a prototype on display that year or soon after of a one-half size F80 that used an automotive V8 driving an internal fan through a gearbox. I haven't seen or heard of it since then, and it wasn't ready to fly at that time, so I have no idea if it was successful. I suspect that that propulsion design would be less effective on a sport plane than a propeller would be, but the point of it was a jet-powered design without the high cost of a turbine power plant. It interested me a lot because it looked just like the fighter it replicated, only smaller.
The made a H block 2-stroke diesel engine like the Sabre for it at 75 litres, but resorted to a single boxer layout. The Nomad actually flew in an Avro Lincoln. Like all these types, turbo jets took over.
We built a compound cycle engine as an example and as a theoretical possible propulsion system for what is now known as the tomahawk cruise missile it was a V8 of about 250 CC's per cylinder running on compressed air produced over 1,000 horsepower! What made this particular compound cycle engine very interesting was a pair of clutches so you could use the turbine power to draw in more air and create more thrust as a conventional turbo shaft engine operates or with the flip of a switch you could add the turbines output to the crankshaft and make insane torque at the crankshaft. I believe it was an old German design from when they were having trouble creating a combuster section with materials of the day and lacking knowledge of modern engineering to create an air cushion between the flame and the metal so that the combustors did not melt through in a matter of seconds. All this contained in a 20-in diameter about 22 in Long it was actually very light, crazy powerful and produced a lot of thrust it was very efficient Considering it had all the modern engineering and materials made thrown at it. I don't know whatever happened to the test engine but it ran for 24 hours a number of times at Garrett Turbine Signal oil now Honeywell Phoenix Arizona.
Yup, ducted fan with afterburner is exactly the thing that came to mind. That is, if there's no turbine, isn't that like an afterburner, except that ignition in the jet's combustion chamber wasn't from an upstream turbojet. Or, am I totally confused.
I think its so cool that i knew the name Caproni before watching this video but never having known much about airplane history. I watched an animated film by studio Ghibli that features Caproni as a person of admiration for the main protagonist, a Japanese boy growing up and then working as an aerospace engineer in japan, before ww2. He meets Caproni in his dreams and they talk about wanting to build beautiful aircraft. I dont know how historically accurate Caproni or even the whole era is represented, but it does follow the life of the eventual designer of the zero fighter. Its called The Wind Rises, if your interested. Porco Rosso is another film by Ghibli, set in a fantasy world full of custom bi-planes and skypirates. Iv always wondered how flight would develop in a slower or different environment than history has already proven. Maybe we would see interesting designs like this developed more and become more common place as a form of personal transport completely reshaping the world as we know it. Thanks for this tidy video essay. I really enjoyed learning about this engine!
I think that this idea still has some validity. With modern piston engines and compressors you could create something that is both efficient at low speeds, and yet possesses turbojet performance for brief periods. All at a relatively low cost.
for example, for a suicide drone which flies low and slow and then activates sprint mode for the last few minutes? Hell lets not forget that huge reason why motorjets were terrible when they were made, was because nobody bothered making them "right". i.e. for example no correctly made airflow, that helps to keep whole system running.
perhaps the Liquid Piston X3 mini engine could perform better at this task, being far more power dense while having the efficiency bonuses of internal combustion. they had a demonstration aircraft proving hybrid electric operation, with in flight starting and stopping, so perhaps an "Electro-Turbo-Motor-Jet" would be possible ahahaha
The air turbo rocket is the turbine version of this concept: a small turbine powered a large high bypass compressor, with most of the massflow going outside of the turbine. The majority of the air of combusted behind the turbine, resulting in high thrust without much thermal stress on the turbine. Only good for high speed aircraft, really
If the MTU concept adds efficiency at the cost of weight, it should work on a land-based turbine used to drive a generator. Those utility guys are really, really interested in efficiency. Today they use the output of a turbojet to boil water to make steam to drive a steam turbine, but the steam turbine is taking energy out on the low-temperature side of the cycle, which is less efficient. The MTU concept, if I understand properly, is proposing to take some energy out of the fuel on the high-temperature side of the turbojet cycle, by raising the initial temperature. That improves the Carnot efficiency!
"Fraschini" is pronounced "Fraskini". I won't try to explain the subtleties of the double T in "Isotta", but it isn't pronounced the way you do. The "N One" you keep talking of is "number 1. "N" is the abbreviation of number in Italian.
Just wouldn't make much sense. Now, a compressor that can be shifted to electrical power, mounted to a zeppelin or blimp that carries solar cells? That could work. But just hydrogen? Makes more sense to run a normal jet straight off of hydrogen.
The problem with powering a compressor with anything but a turbine on the same shaft is immense power that is needed. For instance a model turboshaft engine gives out about 5-6 kW of shaft power weighing 3-4 kgs. So to power its compressor one would need about 9-12 kW motor. And most likely a gearbox as the compressor wheel should rotate at about 100k rpm speed. It did make sense at the time when there wasn't much experience in combustion chambers designing and turbo jet engines in general so it was easier to control and tune the prototypes separately for the turbine and the compressor sides but once their performances are balanced there is no point to put anything in between.
So two totally different power trains powered by two totally different fuels, one of which is expensive, heavy and inefficient for aircraft use where weight and efficiency are everything? Yeah that sounds like a winner
Yes, it would work, the Caproni Campini could fly on fan only and then turn on the burner for extra thrust. If you used an alkaline fuel cell (which is being developed for the Piaseki Helicopter) the cooling requirements of 250C could be used to preheat the air before the burner. Motor jets could work, the reason Caprioni's didn't was the primitive nature of the piston engine which lacked an effective super charger.
Modern materials science is progressing at breakneck pace, so it's very possible internal combustion engines will become light enough for the combined cycle engine to become practical.
Thank you for the info on the Ohka "motorjet" version. I have seen a Smithsonian photo of their "motorjet" Ohka 22 (the Japanese Navy Air Research Bureau designation - the plain rocket version was Ohka 11) which designates the engine as a "Campani jet" engine. The Smithsonian photo states that their Ohka 22 was "recovered in Japan in 1945 -- I have seen a photo of an Ohka-22 sitting on an assembly trestle in a factory in Japan with piles of Ohka parts and partially assembled Ohka aircraft in the background -- this may (or may not) be the same motorjet Ohka. I'm interested in the Ohka because I have a photo taken of my father and his high school friend standing in front of an Ohka at Yontan airfield on Okinawa. The photo is framed to show his tent in the background. The photo showing my dad includes the Ohka with Identification number I-18. There are also photos around the Internet with good images showing the numbers I-10 and I-13. I was in contact with a correspondent who sent me a copy of two photos, one of his father helping to move Ohka I-10 along a dirt track on a low dolly and another of his father standing next to the rocket engine of I-10 with a date on the photo of 4 April, 1945. This correspondent says that he visited an aviation history museum in Chino, California, to see an Ohka that they have (had??) on display and a curation expert at the museum told him that the invading US troops found five Ohkas, fueled and armed, in a cave on Okinawa and they were removed to an open area at Yontan so that they could safely be disarmed. There are photos of I-18 with its external nose removed while the warhead is being removed. There are also photos showing the solid rocket fuel tubes being removed from an Ohka (this aircraft is not identified but the background surroundings seem to indicate that it is likely also I-18). I do not have any information about any other Ohkas that were captured on Okinawa.
I learned back in the 80's, that a turbine engine in a Bell 206 helicopter put out about 400 hp; however, the engine actually developed 1000 hp of which about 600 went to the compressor stage of the motor, leaving roughly 400 hp usable. I have always thought that turbines compress air inefficiently and have always looked to other ways to compress the air required for combustion of the fuel burnt. This really isn't such a bad idea and maybe it should be revisited.
Interesting. didn't the Junkers Jumo 004 turbojet used in the Me-262 fighter use a 2 cycle piston engine to start their compression cycle before transitioning to a 'pure' turbojet?
Gille St Hillaire designed a positive displacement motor called the Quasi Turbine. It is 1/5 the size and weight of a piston engine. The engine is empty in the centre and could house a transmission or generator. Multiple units can be ganged together like Wankle. Rotating eliminated vibration and this airplanes could be lighter again
Rolls-Royce began working on a sleeve valve two stroke “sprint” engine aka Crecy. It was all about power at the expense of fuel consumption. Once it was running they realised it could be a great compressor stage for a jet engine. Ultimately, the turbojet was easier to develop so the Crecy was cancelled.
I have always wanted to build an aircraft for GA that uses a piston engine to power a ducted fan but it will have many stages to the fan each spinning faster.
@@wingracer1614 Because only a few countries are able to produce turbine blades and they keep the metallurgy secret at an overpriced level...With a motorjet or electric compound motorjet you do not need that part but still able to achieve high speed thrust as well self launch capability vs. a pulse jet engine...
The Napier Nomad of the late 1940's / early 1950's was a brillient implimentaion of a turbocompound engne that at the time offered record breaking fuel efficiency at the expence of horrendouse complexity en.wikipedia.org/wiki/Napier_Nomad. I came accross some drawings when I was an apprentice and the Nomad was much more advanced than the engines we were producing for the HS125 loco's. Unfortunately cheap oil and simple turbojets killed it stone dead. The Nomad was reall a gas turbine using a 2 stroke diesel engine as the combustion chamber with the net result of massive overall compression ratios. Power was taken from both the turbine and the engine via a compley hydraulic friction drive variable gearbox which overcame the matching problems described in the RR patent. Takeoff power could be supplimented with afterburning and water-methonal injection, it was a true beast.
A piston engine, even a V12, for some portion of the engine cycle is just dead weight, but jets, and electric motors produce power continuously, micro-second to micro-second.
He S 50 was a Motorjet developed at Heinkel by Wunibald Kamm, with inherent better features than the Caproni, that actually was an afterburner reinforced version of Stipa duct fuselage. However, at Heinkel failed in obtaining enough cooling for the 2-Stroke engine, and never reached production. Gesund +
It's pretty neat what Italy did with the "thermo jet", they even tried making fighters and bombers using the concept but the armistice came before any could be produced, though the Caproni campini ca.183 bis was supposedly quite fare along in construction.
Seems like a rotory engine would be a better option than a piston engine for this kind of layout. They are much smaller, lighter and simpler than a piston engine and they spin at a much higher rpm which I have to think would be better than the slower speed a piston engine needs to run at. They can also put out a lot of power when designed and built well. And are stackable so if you want a larger stack you just need a few longer tie rods and crankshaft and you can essentially bolt two or more engines together. The only downside is that when not built perfectly they can have reliability issues and the engine technology isn't nearly as far developed as piston engines.
except the better fuel burn rate would allow for longer ranges or more time over target, the first being valuable for all aviation. Your average bush plane gets 800-900 miles range with a turboprop, if the motorjet could reduce fuel burn without the weight gain the same fuel load could add 200 miles to that.
Try a small, compact, 3-rotor Wankel engine, mated directly (no gearbox) behind a 3-5 stage fan setup. Since a rotary engine runs best at about 5k RPM, you can mate it to fan, about 1.1m in diameter, which at 5k RPM would result in tip speeds, just below the speed of sound. Use cooling fins and air inlet in the duct for the engine. Route the fuel and electrical control lines through the struts. Use a jack-screw-mounted bulb in the exhaust nozzle to control exhaust airflow. If you can generate about 1000 lbs of thrust with such a setup, you could power a light GA plane with it.
