Another engine theory Q - Blowers?

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akwrencher

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"Under normal circumstances, you will encounter gaseous oxygen. That's because oxygen cannot be liquified above a temperature of -119 degrees Celsius (-182 degrees Fahrenheit), no matter how much you compress it. At its critical temperature, it takes a pressure of 49.2 atmospheres to liquify."

I suspect it may not be practical?
 

BRAAP

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BRAAP- The Nissan L series engines go back to the '60s and I've built plenty of turbo and NA ones for street and road racing, won a couple championships with them. Never saw the problems you describe in ones built with Webers or EFI, all using stock crank, rods and fasteners. The heads were really bad flow wise for sure on my flow bench....
Familiar with them, our business was centered around Datsuns, Z cars primarly also the Dime, building and machining engines, a bit of custom EFI, in particular building and machining custom cylinder heads for customers around the world, low volume shop, all work done in-house, always struck me odd that half our business were customers in Europe.
Problem I found was mostly with L-6, (N42, N47, P79, and P90 heads), never experienced those issues with any of the L4 engines we built.
getting an L-series to breathe even somewhat respectable is an art for sure. We found found Valve unshrouding is where our biggest gains came from, a bit bowl in the exhaust was pleasantly surprised when one of our European customers had our head sent to Rebello to be put on one of there 3.1L’s Dave remarked no head has come through that performed that well. We’ve used many of his custom cams as well.
2E421326-9EB1-4282-B519-229F0D7FFB8C.jpeg

... Comparing this engine to even something remotely modern, say from the '90s at least and you're in a different world. Few people would pick such old engine designs to power aircraft these days in turbocharged form outside of maybe VWs and Corvairs, just because they are light.
The mentioning of the L-series was merely to illustrate the sensitivities and possible issues that could be experienced when increasing specific output and trying to maintain that for long durations, would not recommend the old clunky L-series as an option, even today I prefer not to build the L-series unless it’s a restoration, typically swap in modern power plants, (BMW S-52, and of course LSx).
 

rv6ejguy

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Brings back good memories seeing these pix. Had a lot fun with L16, L18, L20B, L24, L26, L28 engines.

race2.jpg

Not a good photo but the turbo 510 in 3rd on the grid passed the Porsche and the Sports racer into turn 1 at the start. They were rather upset. It was a giant killer on the straight and very reliable. We soon dominated most classes with small turbo engines, mostly Toyota 2TC based. This changed the minds of many people on how reliable/ powerful small turbos could be.
 

trimtab

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There has been a great deal of work done with water injection in SI, CI and turbine going back into the '30s (or beyond?). Amazing how easily we forget the lessons of the past, but this uses the energy of change-of-state from liquid to gas phase to drop cylinder temps while raising pressures. Easily takes NOx to near zero. The aftermarket extreme turbocharging crowd knows this one quite well.
The thermo calcs for these schemes have many caveats.

For a given maximum attainable charge temp, adding water nets zero to the cycle. The addition of water is made to extract work from a charge temperature that would otherwise exceed the capabilities of the engine. Higher compression ratios are attainable, but no increase in thermal efficiency from those higher compressions are realized when the max temp is blunted by the water. More horsepower can be extracted under the right circumstances, just at lower efficiency. More work per stroke is attainable.

But the "aqueous fuel" calcs never work out beyond what is described. A 'homogenous' cycle (where the generated steam and fuel/air charge are coincident in the cylinder and mixed) simply lowers the Carnot efficiencies, and there is no net mechanical work from the enthalpy calculations. "Partitioned", or dual cycles, are possible, whereby the heat energy of the combustion exhaust is used to drive a second thermo cycle (with water, but could be any working fluid).

My play time with injection used an older Bosch injection system pushing diesel (to save the pump) into an accumulator cylinder to pressurize a steel tube coil with H2O heated to supercritical conditions at nearly 300C. The pump wobbled the pressure to 7k psi to release the poppet style injectors. Supercritical steam is hard to contain, but it worked reasonably well to evaluate the effects. The net effect was minimal when injecting the H2O late in the cycle until I converted the cam to allow overexpansion (Atkinson cycle), shaved the head down, and then there was significant improvement in power output and efficiency. Adding in the power required to run the Bosch pump for a minute that each run took (the accumulator was only about 200 ml before the diesel would reach the injector feed tube intake) meant the performance improvement was in the weeds for this homogenous system. Converting a identical second engine into a steam expander with the water coils heated directly by the first engine running as an Atkinson (making a "partitioned" cycle) extracted enough power to theoretically run the pump ( I still ran it with a BLDC) and also added net power. Overall, the efficiency of the partitioned system increased from about 11% to about 15%, which is actually quite a bit. The weight of the system would never be useful for aeropropulsion. It turned out to be impractical beyond simply having a lot of fun with some cheap engines, my machine shop, a set of used injectors and diesel pump, some electronics, and some imagination to settle thoughts I had had since high school too many decades ago. The results were satisfying and in line with expectations, and cost less to get than a cheap annual on my plane.

Water injection is used to lower max temps and partially harness the excess enthalpy from excessive cycle temps to increase power output in a cycle at the (large) expense of efficiency.
 

BRAAP

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Brings back good memories seeing these pix. Had a lot fun with L16, L18, L20B, L24, L26, L28 engines.

View attachment 115085

......
Great photo. Love reminiscing about these days.
Sweet Turbo dime. ❤ 510’s always would earn the respect being a giant killer. Also a BLAST to drive.
Thank you for sharing. 😉
Apologies to OP for off topic
 

Kiwi303

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It would be interesting to see a turbo L series on an aeroplane, but cast iron blocks are just too heavy if there is ANYTHING else available, I've an L16 block on the ground just outside the farm shed I've never actually gotten around to attaching a chain/rope/float and making a boat mooring from. it feels as much to lift as a Rover V8 3.5 aluminium block... If you had to do a "Flight of the Phoenix" type thing and it was ll you had, I guess a L series could be MADE to work, but otherwise nope.

Haven't been to HybridZ for a while BRAAP, hows things over there?


Back to the original Blower topic, I'm partial to supercharging over turbocharging for street use due to the instant power available from idle, cramming more air in with more fuel simply makes the engine masquerade as a larger displacement motor, without lag. But for an aircraft, spooling up on the ground before the takeoff run will pass through the lag zone and it's a nonissue in the air, so long as weight is comparable I don't see any benefit for one over the other in an aircraft installation.
 

mcrae0104

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...so long as weight is comparable I don't see any benefit for one over the other in an aircraft installation.
One method harvests energy from the power otherwise devoted to thrust, while the other harvests energy from waste heat. If a supercharger and a turbo(super)charger weigh the same for the same pressure ratio, the turbo has the advantage. This efficiency is indeed a benefit, particularly when lag is not a concern. That is why superchargers largely dropped off the scene after metallurgy made turbine wheels/blades practical.
 

rv6ejguy

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Much as I have fond memories of '70s era cast iron block Nissan and Toyota engines, they make no sense in aircraft. There are multiple lighter/ better modern engine choices out there but the turbo is a great way to turn the engine slower for longevity and still have a good power to weight ratio.

IMG_2369.JPG

This was the EJ25 turbo powered RV-7 I had a hand in a few years back. Would exceed Vne in level flight quite easily at about 40 inches at medium altitudes (10-12,000) feet.
 
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Aviacs

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OP here, been an interesting discussion which seems to have answered my Q:

"In terms of engine complication and durability, boost is a viable alternative to a PSRU for the purposes i consider."

However, contrary to mechanical positive displacement pumps (or mechanically linked centrifugal types), turbo-charging has come a very long way (is nearly a mature niche industry) since i last visited the subject in the late 1970's. Hence, turbo-charger can provide both the TO torque (& power) that interests me, yet be somewhat invisible during cruise flight if desired, and overall provide better efficiencies and flight regime flexibility.

For someone who posted about sucking through a carburetor before the blower- My assumption is that once a person chooses to "complicate" a VW engine, that (close, individual port) EFI should be the foundational first step. Build out (or not) from that. Even un-boosted it should be a nice insurance system that allow use of max available HP with fewer concerns about engine management & potentially better longevity.

Regardless the boost type/system, i believe it was Frank Lockhart in 1926 - 27 with the Weisel brothers, who first demonstrated what a great difference intercooliing made in the effectiveness of supercharging, as well as mitigating so much of heat induces risks to the engine. The 3 continued to develop and refine intercooling until Lockhart was killed due to tire failure at Daytona beach in 1928. That's pretty old news.

Thanks, and carry on the discussion and diversions - there much of general interest. :)

smt
 

wsimpso1

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Hydrogen peroxide might work. Not sure what mix with water would be ideal?
Hydrogen peroxide works great when there is continuous flow and you want the peroxide to flash at a particular spot. Hydrogen peroxide rockets put the silver catalyst screen in the vicinty of the outlet from plumbing to combustion chamber. Getting peroxide to flash at the right time in a piston engine cycle might be tricky. I suppose with a direct injection nozzle, you could put it in only a little advanced on where your want ignition, like with diesels.

The big thing working against all of these "added oxygen" systems is that the amount of oxygen needed per minute of flight is huge. Most engines need a lot more weight in oxygen than fuel. Saturn V first stage engines used 2.65 pounds of oxygen per pound of kerosene. With added oxygen systems, well, you start driving towards batteries for energy density... It really is a way lighter system to boost the manifold pressure with energy harvested from the waste stream.
 

TFF

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For a Sonerai, I would build the biggest regular engine. Nothing real exotic. Turbo could be fun, but I would probably be in the not club. If I did, it normalized club instead of boosting. Not because I’m against boost, but to just keep it reliable. Pure speed I would be willing to blow it up. EFI. Nice but I think most would be flying with a carb first. Make it an upgrade. Get the plane in the air, then tweak and upgrade. If you chase every good idea, you will run out of time.
 

Aviacs

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If you chase every good idea, you will run out of time.
This is certainly a factor.
But also the essential reason i want to think through all the options before attacking.
Far from likely to "chase" them all, more a sorting process.
I might not have time to improve or upgrade later.

There are other planes to fly during the evolution, and as i have posted in past, some of the build will be determined by how much work it takes to get an E-AB. You are aware from other posts that "easy" options include wing upgrade. Minimum essential right now are taller canopy to fit me, = taller vertical stab + larger rudder to compensate. Also carb choice and possibly induction system change. Which is about 1/3 of the way to an EFI system.

Re: carburetors, the immediate previous owner kept it in his hangar but never flew it in 2 years. He claimed to have done "high speed taxi tests" & was quite concerned about the carburetor; gaskets of which he gave me extras, and the mating surfaces. Since my French is poor and mostly reading based, neither one of us completely understood the other. (Wife says my spoken English comprehension is not much better :) )

A couple weeks ago browsing prior owners to the one i bought it from on google, this came up:

Atterrissage d'urgence à Saint-Nicolas

[Carburetor problem stopped engine of amateur built Sonerai 2L, owner Gaston Dorval made an emergency landing on the shoulder of route 20 (the major rte between Montreal & Quebec). 2 people on board, no one hurt. No damage to the airplane, no inconvenience to traffic. August 8, 2009.] Nice flying!

I did meet with the local FSDO rep in our hangar on Sept 1 for a WINGS program as previously posted, but as host was circumspect about keeping him overly long when others were in line to bend his ear. We agreed to talk after the holiday. Our chapter has a long term association, and the 4 FAA people who came are a great bunch of guys.

smt
 

BBerson

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The big thing working against all of these "added oxygen" systems is that the amount of oxygen needed per minute of flight is huge. Most engines need a lot more weight in oxygen than fuel. Saturn V first stage engines used 2.65 pounds of oxygen per pound of kerosene. With added oxygen systems, well, you start driving towards batteries for energy density... It really is a way lighter system to boost the manifold pressure with energy harvested from the waste stream.
Depends on the mission (which might not be stated in post one). Could be 30 seconds of boost needed to clear the trees or continuous cruise at high altitude. Those are different missions.
 

BRAAP

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....
Haven't been to HybridZ for a while BRAAP, hows things over there?
Kiwi.... good to hear from here, been a long time. HBZ has slowed down, can only speculate most of the original enthusiasts have moved on, not as many available, etc.

Will have to catch up on aviation things soon.
 

TFF

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There are ideas and there are ideas. In high school I got my hands on probably the roughest Teenie Too ever to take to the sky. No engine. It had flown with a direct drive 440 on it and it went down from there. Maybe even literally. It didn’t fly very long from what I could tell and that the left wing had been de riveted to fix either the gear collapsing or wing hitting something. Chicken or egg damage. At that age, I had a boy this thing is crude moment and knew it wasn’t going to fly again. And crude is what T2s are about. It comes back to your carb dilemma.

Bad execution of a good idea makes it a bad idea. Every installation has problems of any object. Carb issues is generally not minding Ps&Qs. EFI has same and usually much more. It’s not a good or bad. Most people are not equipped to deal with EFI because of unlimited options. You might be given a baseline, but the rest is up to you. A buddy of mine had a H3 Hummer with with a LS-3 crate engine, and he constantly drove around with a laptop. Getting it to run was never an issue; getting it sweet was.

VWs are a known quantity on Sonerai s, even bolted to ones that aren’t fully. You will not be cheaper with a VW prop drive with EFI over a conventional engine. Definitely not more reliable even if reliability isn’t a concern. If it’s your dream combo, probably worth it; that means you are interested in wrenching as much as flying. The guy with the A-65 powered Sonerai that use to be on the forum though it was a great combo. I think his issue was it wasn’t a buy and fly as he first thought and that the engine although a runner was pretty worn. My friend had two RV3s both had 320s. I would be picking a 235 as the in between. I’m actually not held up on an airplane engine as the only way, but the ones who do use them just do and will forge through the problems and solve them themselves. They might ping ideas, but it’s going to be their solution. Thinking any combo of EFI or prop drive is off the shelf is going to make for a miserable experience. We will give the VW a 50% pass on off the shelf. It’s a wrencher’s game.
 

rv6ejguy

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I dunno, we have the largest order backlog in our 27 year history right now on aviation EFI kits. We do no advertising outside of a small ad on VAF so that I can post about SDS there. The rest is word of mouth, our website and YT page which costs almost nothing. The vast majority of systems are for Lycoming fours and sixes, tons going on RV-10s. Most folks are very happy with our EFI and would never go back to carbs or mags. We ship systems with maps for the particular engine so user tuning should be minimal. Every system is built to order for each customer.

We literally can't build systems fast enough to keep up with the demand...
 

dwalker

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OP here, been an interesting discussion which seems to have answered my Q:

"In terms of engine complication and durability, boost is a viable alternative to a PSRU for the purposes i consider."

However, contrary to mechanical positive displacement pumps (or mechanically linked centrifugal types), turbo-charging has come a very long way (is nearly a mature niche industry) since i last visited the subject in the late 1970's. Hence, turbo-charger can provide both the TO torque (& power) that interests me, yet be somewhat invisible during cruise flight if desired, and overall provide better efficiencies and flight regime flexibility.

For someone who posted about sucking through a carburetor before the blower- My assumption is that once a person chooses to "complicate" a VW engine, that (close, individual port) EFI should be the foundational first step. Build out (or not) from that. Even un-boosted it should be a nice insurance system that allow use of max available HP with fewer concerns about engine management & potentially better longevity.

Regardless the boost type/system, i believe it was Frank Lockhart in 1926 - 27 with the Weisel brothers, who first demonstrated what a great difference intercooliing made in the effectiveness of supercharging, as well as mitigating so much of heat induces risks to the engine. The 3 continued to develop and refine intercooling until Lockhart was killed due to tire failure at Daytona beach in 1928. That's pretty old news.

Thanks, and carry on the discussion and diversions - there much of general interest. :)

smt
I like where your head is at. Let me help you a bit. The following information is what I would do, but note that I in no way am telling a grown man capable of making his own decisions what to do, or how to do it.

I am starting with all brand new parts- case, crank, rods, pistons etc., no used parts at all. Forged pistons and high strength rod bolts are a must, and the heads should be the twin-plug units from MOFOCO. Assemble the engine using best practices- Yamabond or Tri-Bond to seal the case halves, oil mods as needed, and use a dry sump oil pump. Block off the fuel pump drive and plan for a remote oil cooler. If I use the VW I will use a dry sump system with an external oil tank and cooler arrangement. A force one Prop hub and Diehl accessory case as is fairly normal.
I plan on using a modified set of dual port manifolds with the throttle body in the center and to the rear of the engine. I know there are very nice EFI manifolds out there, but I have concerns about them fitting under the cowl without modification to the cowl. The EFI setup will consists of-
AEM Infinity 506 or AEM EMS-4
4 550cc injectors, EV14 Bosch
Extruded aluminum fuel rail machined to fit the injector spacing and for O-ringed port ANF fittings
Hall effect cam sensor that replaces the distributor
Mag crank sensor with trigger wheel
Walbro 255LPH fuel pump
Aeromotive adjustable fuel pressure regulator
Aluminum hard lines to fuel rails and pressure regulator with AN fittings, flexible teflon with Kevlar braid line- XRP XM series or similar- from engine to fuselage hard lines.
Coil per plug using Denso coils
Turbo manifold welded up from 321SS and using a T3 SS flange
Turbo- plain bearing 61mm compressor wheel, S cover, .82 hotside and a P-trim turbine wheel to start. On 2350CC at 3000rpm the P-trim wheel should be very happy. This is however a calculated risk of using a lower cost turbo knowing going in that we are sacrificing transient response for lower stress and less generated heat. My second choice would be a GT3076R with a cast stainless steel turbine housing using V-Band inlet and outlet. Twice as expensive, but very very durable. Without water cooling the oil temperature must be watched pretty carefully.
For the wastegate there are a couple of choices- modify a Tial/Precision/etc. poppet valve gate to be controlled via a cable system and manually control the boost. Use the same wastegates run as normal using the ECU to control the boost with a manual adjustment input, or use an internally gated turbine housing and again rig it for manual control.
From the turbo I on using a simple and lightweight tube/fin intercooler. Not as efficient as the usual plate coolers I tend to run, but well suited to the task, and lightest option.
In addition I will use a water/alcohol injection system controlled by the ECU which will not only help with with heat, but also clean the combustion chamber and pistons and help to lessen the risk of carbon knock.


And that is pretty much the big bits. Making 100hp or slightly more when needed from the 2350cc motor with boost is very easy to do, and can be done safely with some caveats-
To get the same service life as the standard VW flight motor you will have to pay even more attention to oil cooling and intercooling. Water/alcohol injection will likely go a long way towards keeping the cylinder heads happy.
Turbo sizing will be key and conversations with experienced people before purchasing anything will pay off.
EFI is easy. Setting it up successfully can be easy with careful thought given to components, wire and hose/tube routing, etc. or it can be a nightmare if you just dive in without that consideration.
This setup will weigh more, obviously, than a standard VW installation, but having a real, legitimate, 100-110hp may or may not make the weight penalty worth it.
 
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