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TheTacticalCat

How does the engine of a plane work?

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The spitfire has a fuel capacity of 386L. The merlin engine has a displacement of 27L. So in 14 cycles, it runs out if there is 100% fuel. At 80% mixture, that means 71 cycles. Which is not very long. I'm missing something, I don;'t know what though.

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The percentage are not to be understood litteraly. The fuel is very finely dispersed in air. For example a modern car engine uses 14.7 gram of air against 1 gram of fuel. (14.7:1).
The mixture percentage refers to a lever position in the cockpit which adjusts the fuel amount in the engine to get it back to a good mixture as the air gets thinner higher up.

Edited by DerSheriff
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2 minutes ago, DerSheriff said:

The percentage are not to be understood litteraly. The fuel is very finely dispersed in air. a modern car engine uses 14.7 parts of air against 1 part of fuel. (14.7:1).
The mixture percentage refers to a lever position in the cockpit which adjusts the fuel amount in the engine to get it back to a good mixture as the air gets thinner higher up.

 

So a 100% mixture would be what? 14.7:1?

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I think your under the impression it burns 27L of gas in a cycle, which isn't the case 

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There isn't a 100% mixture. That percentage thing, whether it be throttle, mix, trim, etc, are something that the old Il-2 saddled some people with that is a measure of simply the control that is not truly applicable at all to best operations. Best operations are watching the instruments and adjusting based on that as there is no golden percentage throughout the altitudes and flight envelope.

 

Mix is rich or lean, auto, or variations of lean or rich.

 

The Il-2 percentage stuff needs to be dumped, it does no one any good due to how variable the settings are.

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15 minutes ago, TheTacticalCat said:

 

So a 100% mixture would be what? 14.7:1?


Dont know. If we just assume its the same then yes. I doubt its the same. And further more it will be different from aircraft to aicraft.

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17 minutes ago, GridiroN said:

I think your under the impression it burns 27L of gas in a cycle, which isn't the case 

Lol 

 

When an engine says it is that many litres 27 in this case that is the amount of volume inside the engine. You would not fill all that volume with fuel just a tinny fraction, the rest being air.

Edited by AeroAce

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Also, the ~14,7:1 still refers to the mass ratio of fuel to air, it's not like there is 27/15,7 liters of liquid fuel burned in each cycle. :)

Furthermore, there are 2 crankshaft revolutions for 1 'combustion' in a four stroke engine.

Edited by rolikiraly

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What you're missing is very simple: The optimal ratio of air to fuel around 15:1 is measured in mass not in volume. This means that a stoich mixture of air and fuel will have around 15 grams of air to one gram of fuel. Obviously fuel is much heavier than air, so by volume, there will be a lot less than 1 in 15 parts fuel in the mixture that goes into the cylinders.

 

If the air that goes into the cylinders is at normal atmospheric pressure (which isn't really the case, but just to get an idea) those 27 liters of air will weigh just 3 grams, which means that at an ideal 15:1 mixture, the engine will burn just 0.2 grams of fuel per cycle - which is still a heck of a lot, at 3000 rpm (2 revs per cycle) that will burn up 300grams of fuel per minute in our hypothetical example.

 

EDIT: Edited a bit of my shoddy math and took into account the 2 revolutions per cycle

 

EDIT2: Just to be clear: The Spitfire engine obviously burns more than 300 grams of fuel per minute at 3000rpm. I used normal atmospheric pressure to make things a bit simpler.

Edited by Finkeren
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The ops post reminds me of being an first year engineering student. Hmm something doesn't seem quite right here?

Edited by AeroAce

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Well, I had a sunken Float on my 650 BMW Bike. Fortunately it didn't light off on the Good Cylinder. But that is the closest thing to coming close to using your Displacement being Equal to your Fuel Consumption per Revolution. Also made for a somewhat unexpected and unwanted Oil Change. 

 

In any Case, I can only assume you to be very, very, very young so I can forgive your Ignorance. Study up on your Engines, they are an absolutely Fascinating Subject. Get an old 2 Stroke Moped or a Lawnmower and take it apart and put it back together. Learn about Carbs and Spark Timing, Camshafts and Rotary Inlet Valves, Intake Membranes and so forth. 

 

Especially Old 50cc Vespa PKs and the Ape 50 are a Load of Fun to Work with and improve upon. Or if you want something a bit more Robust and Reliable the Simson 50cc Mopeds are fast, fun and as simple as an AK-47 but with a ton of Potential Power. 

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The percentages as indication of lever position works just fine IMHO.

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Just now, Sambot88 said:

 

The percentage system is great if you understand how it works. 100% is 100% of the lever pressed forward. That seems pretty reasonable.

100% Forward is normally Lamda 0.7 to 0.8 on the Klimovs, and Auto Rich (Lamda 0.8 to 0.9) for all others. And 0% is either Cut Off or around Lamda 1.5 to 1.8 for the Klimovs, but pretty much 1.0 at about 8k. 

The Pe-2-35 has a practical little Lamda Gauge on the Panel. 

 

 

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Also: The Engines of an Aircraft work the same as those in Sports Cars, Motorbikes, Speedboats and Mopeds. 

 

Whenever Longevity, Fuel Economy, Ruggedness and Reliability are needed the only Sensible Choice is a Diesel though. That's why Trucks, Tanks, Ships, Locomotives and Generators are pretty much exclusively Diesels. 

Petrol Engines really are silly Sports and High Performance Nonsense. 

Edited by 6./ZG26_Klaus_Mann

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1 minute ago, Sambot88 said:

 

Now this is a post that has piqued my interest. Are there examples of planes (modern or not) that used Diesel? 

 

 

 

Ju 86.

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Well, historically there were only a few. The most Notable are the JuMo 205 and 207 powered Ju-52 and Ju-86 as well as the Pe-8 and Yer-2 as well as a couple of German Flying Boats. 

 

Modern Examples are Diamond Aircraft's DA-42 as well as EVERY SINGLE JET AIRCRAFT out there. Jet Fuel and Diesel are very close to one another, with Jet Fuel and Kerosene having a slightly higher Flashpoint and Lowered Lubricity. 

So you can run your Diesel on Jet-A, Heating Oil and Kerosene, but mix in at least 5% 2 Stroke Oil for the Fuel Pump. 

 

The Main Issue is weight. The Internal Combustion Diesel is better in every other conceivable way, except for Weight so for most light Aircraft the Petrol Engine is the better Choice for Performance, especially on Take-Off. 

In the Air the DA-42 and DA-62 is the most Fuel Efficient Choice out there, with incredible Range at Low Prices. 

The DA-40 Diesel is a very Popular Trainer here because it almost halves the Fuel Cost per hour. 

 

So there are examples out there, but since most Private Pilots are on the Richer Side of things, Money is less of an Issue, and so Petrols remain Widespread. 

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Getting well off-topic here, but on the subject of jet engine fuels, when Chrysler were experimenting with gas turbine cars in the 1960's, they did a fair bit of testing:

Quote

The A-831 could operate on diesel fuel, unleaded gasoline, kerosene, and JP-4 jet fuel; leaded gasoline damaged it. According to Chrysler, it could burn a variety of unusual fuels ranging from furnace oil and perfume to peanut and soybean oils. Mexican president Adolfo López Mateos ran one of the cars on tequila after Chrysler engineers confirmed that it would do so.

https://en.wikipedia.org/wiki/Chrysler_Turbine_Car

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Well, Jet and Diesel Engines can run on pretty much anything without Problem as long as the ECU is set for it, you have a lot of Spare Fuel Filters and an independently Lubricated Fuel Pump. 

A Club Colleague of mine runs his 2002 VW Caddy 1.9 TDi on every kind of Oil he can lay his hands on. He has a Centrifuge in the Back, 3 Spare Fuel Pumps and 3 Quick Change Fuel Filters in a Row. He built his own ECU, and the Car Sounds funky as Hell, but it has a ton of Power, at least 160 if not more. I have trouble keeping up with him on a 60hp BMW Bike. It's quite incredible. 

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the reason to change to jets its not performance you can always build a  more powerfull propeller as adding one to a count

 

the reason are sparks are electric and prone to near certan failure after a nuke electromagnetic pulse while jets need no electrical part to work on their air comrpressors turbines to burn fuel inside

 

first nuke deployed in 44 jets built in 44

 

ahem 

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I always read that the Spitfire with its Merlin engine burnt about 1 gallon per minute under

the right engine management settings.

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22 hours ago, Finkeren said:

What you're missing is very simple: The optimal ratio of air to fuel around 15:1 is measured in mass not in volume. This means that a stoich mixture of air and fuel will have around 15 grams of air to one gram of fuel. Obviously fuel is much heavier than air, so by volume, there will be a lot less than 1 in 15 parts fuel in the mixture that goes into the cylinders.

 

If the air that goes into the cylinders is at normal atmospheric pressure (which isn't really the case, but just to get an idea) those 27 liters of air will weigh just 3 grams, which means that at an ideal 15:1 mixture, the engine will burn just 0.2 grams of fuel per cycle - which is still a heck of a lot, at 3000 rpm (2 revs per cycle) that will burn up 300grams of fuel per minute in our hypothetical example.

 

EDIT: Edited a bit of my shoddy math and took into account the 2 revolutions per cycle

 

EDIT2: Just to be clear: The Spitfire engine obviously burns more than 300 grams of fuel per minute at 3000rpm. I used normal atmospheric pressure to make things a bit simpler.

I think this answer wins for me. Also, I knew that it doesn't burn 27L of fuel, cos then there's no oxygen. I was just acting thick cos I'm lazy.

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21 hours ago, 6./ZG26_Klaus_Mann said:

 

Whenever Longevity, Fuel Economy, Ruggedness and Reliability are needed the only Sensible Choice is a Diesel though. That's why Trucks, Tanks, Ships, Locomotives and Generators are pretty much exclusively Diesels. 

Petrol Engines really are silly Sports and High Performance Nonsense. 

 

Well, petrol engines are also less toxic than diesel, that's a thing to consider I guess :salute:

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1 hour ago, raaaid said:

the reason to change to jets its not performance you can always build a  more powerfull propeller as adding one to a count

 

the reason are sparks are electric and prone to near certan failure after a nuke electromagnetic pulse while jets need no electrical part to work on their air comrpressors turbines to burn fuel inside

 

first nuke deployed in 44 jets built in 44

 

ahem 

 

aehm, thats not how it works. A jet engine produces a lot more thrust at higher speed because as airspeed increases inlet air is compressed which creates even more thrust. Props have really low acceleration at high speed and a top speed of around 800 kph, a jet engine can handily go faster.

 

Also regarding spark plugs, an original diesel engine does not need spark plugs. Modern diesel engine are not without fault though, I know of a case where a diesel twinengine plane crashed into a small river after takeoff because it was commonrail design and the onboard battery was somewhat low on charge, when the pilot switched the gear lever the current used by the gear made the battery voltage drop below a critical point and both engines just stopped in an instant.

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4 hours ago, Eicio said:

 

Well, petrol engines are also less toxic than diesel, that's a thing to consider I guess :salute:

You are quite wrong. Diesel's produce virtually no CO, my Generation (Euro 4 and older) Produce virtually no NOx as well, and the Pre Euro 2 Diesels didn't even produce Fine Particulate. 

 

A modern Petrol Car however has worse Fine Particulate Emissions than a Diesel with DPF, produces more CO under Real Conditions than did the older Generations, the produce highly toxic and cancerous Benzopyrens and Benzoapyrens, yet nobody cares. 

And still the Petrol Cars lag behind in Efficiency by about 30 Years. 

 

A Diesel with AdBlue Injection will literally be unable to Kill you with it's exhaust Gasses. You can take a Modenr Diesel into your Garage, close all Doors, get in it and run it for 24 Hours and come out Perfectly alive. 

A Modern Petrol Car would kill you in Minutes. 

 

And the Petrol Cars are Cheating all the Same. To get the insane Power Outputs from these undersized Engines while maintaining Low Fuel Consumption they have to. On Low Throttle they go too lean for the Catalysts, and the Richen up too high for the Catalysts as soon as more than 50% Throttle is applied. 

In Summer Temps the Engine will always run too lean, while in Winter they richen up. 

So pretty much the only time the Petrol Car is somewhat cleaner than the Diesel is inbetween 10°C and 20°C at about 1/3rd Throttle Position. And that's only for about the First 50 000km.

 

But Fortunately we now no longer Control the Actual Exhaust Gas, but the OBD. And that doesn't show a fault even if no Exhaust is attached at all. 

 

 

To Conclude: The Diesel is still the Future. Twice as Efficient, Half as bad for the Climate and simply unlucky in Public Opinion. And Banning it from anywhere won't make a bit of a Difference. 

And if you have a Gas Cooker, your Kitchen gets to roughly 4000 to 6000 times the allowed Maximum in the inner Cities, just so you have a comparison. 

And any of the Numbers telling us of thousands of NOx Deaths a Year are simply Pulled out of someones Arse. The Inner Citiy Air in Germany is at it's cleanest since the Industrial Revolution. 

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If you want a clean Petrol Car you have to take one from the 80s and 90s. Their primitive EFIs knew only to do one thing "Must Maintain Lamda 1.0" and that is what they did, under all circumstances. And that means their Catalysts werre working 100% of the time. 

That of course means higher Fuel Consumption Low Down, and Less Peak Power because you run into Knock quite early on with only 1.0 Lambda. That's why a 1.6 back then had 75hp and a 2.0 barely made over 100. 

If 

Nowadays the Cars are much heavier, yet People want Smaller Engines, more Power and better Economy. It's obvious that something, somewhere had to compromise. If you seriously believe you 180hp 1.4 Liter doesn't Cheat on it's Emissions you deserve to be called an Idiot. 

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8 hours ago, raaaid said:

the reason to change to jets its not performance you can always build a  more powerfull propeller as adding one to a count

 

the reason are sparks are electric and prone to near certan failure after a nuke electromagnetic pulse while jets need no electrical part to work on their air comrpressors turbines to burn fuel inside

 

first nuke deployed in 44 jets built in 44

 

ahem 

 

First nukes were deployed in '45 actually.

 

I am certainly no expert but is it possible to achieve supersonic flight with propellers? I mean, aside from maybe diving?

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Pay no attention to raaaid. 

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To add two cents to the aforementioned air-to-fuel mixture ratio, If I recall correctly, stiochiometric 15 to 1 by mass corresponds to roughly about 9000 (yes, thousand) to 1 by volume.

Edited by Art-J

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On 8. 3. 2018 at 1:03 AM, Sambot88 said:

Are there examples of planes (modern or not) that used Diesel?

 

Pe-8, Er-2 (using either Charomsky ACh-30 either M-40 diesels), Ju-86 and BV 138 (with their Jumo 205 diesels) used operationally in ww2 come to mind. There's probably a lot more.

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3 hours ago, Sambot88 said:

 

First nukes were deployed in '45 actually.

 

I am certainly no expert but is it possible to achieve supersonic flight with propellers? I mean, aside from maybe diving?

 

A turbofan engine can go supersonic - maybe could be considered as one, as its fan resembles a propeller in duct?

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1 hour ago, Art-J said:

To add two cents to the aforementioned air-to-fuel mixture ratio, If I recall correctly, stiochiometric 15 to 1 by mass corresponds to roughly about 9000 (yes, thousand) to 1 by volume.

More like 8149 : 1 for volume ratios in standard athmosphere, using 14.7 as a rich mixture.

 

A Merlin engine pumps at 0 boost in one cycle (cranking the prop twice per cycle) 27 L of air and 3.3 cm3 (2.37 g) of fuel. This is about 4 L of fuel per minute at 2400 rpm.

 

Fuel tank has 386 l volume (86 imp. Gallons), giving about 100 min of run time.

 

At higher ratings, rpm as well as boost, fuel consumption in (this) theory increases linearly. It does so when I up rpm to 3000. I am drawing now 5 L per minute, viving total endurance of about 77 minutes.

 

Going up with boost also decreases lambda in your mixture regulator. So the mixture for going at full bore may be around 10:1. Max power in theory is obtained around 12.6 : 1, but if you're really asking for it, you need more fuel to cool your burn. At 10:1 ratio, you get about 5550 : 1 as volume ratio, increasing your fuel flow almost 50%! (like 47%). your mileage is impacted accordingly.

 

Using 3000 rpm, 0 boost, (5 L per minute fuel consumption) and change to this "rich rich" lamda setting, you're now up to 7.5 L per minute fuel flow!

 

Then increasing boost to 12 will add another 81% fuel flow, resulting in 13.6 L per minute, giving 28 minutes of endurance at full bore.

 

This assumes perfect burn. in reality, numbers I would expect (like in the manual) slightly below that for your usable mileage.

 

 

 

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5 hours ago, Sambot88 said:

I am certainly no expert but is it possible to achieve supersonic flight with propellers? I mean, aside from maybe diving?

They tried. It is a disaster.

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maybe im wrong about explosion engines speed capabilities bu whats certain is jets resistance to nuke electromagnetic pulse while piston engines fail

 

and tell me both jets and nukes in trillions years history are developed both in 24 months span :) 

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4 hours ago, raaaid said:

maybe im wrong about explosion engines speed capabilities bu whats certain is jets resistance to nuke electromagnetic pulse while piston engines fail

 

and tell me both jets and nukes in trillions years history are developed both in 24 months span :) 

 

giphy.gif

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16 hours ago, raaaid said:

maybe im wrong about explosion engines speed capabilities bu whats certain is jets resistance to nuke electromagnetic pulse while piston engines fail

 

and tell me both jets and nukes in trillions years history are developed both in 24 months span :) 

 

Weren't the bombs dropped on Japan in 1945 dropped by propeller-driven bombers?

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If not hardened against EMP, the computer controls and electric fuel pumps will fail, thus ending a jet's day real quick, and if it was on the ground it could not be started because the EMP will kill the ignition system, at least.

Edited by BlitzPig_EL

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On 3/8/2018 at 7:55 PM, Sambot88 said:

I am certainly no expert but is it possible to achieve supersonic flight with propellers? I mean, aside from maybe diving?

 

As a fun aside:

 

Robert Bradley in his book Convair Advanced Designs: Projects from San Diego, 1923-1962 says while he was diving a Hellcat from 28000 ft at a 60° angle at full throttle he expected to hit 485 mph at 10000 ft (terminal velocity) and initiate a 2.5G pullout.  What happened is just before 10000 ft the plane wound up pitching forward and continued building speed and it happened so fast he didn't get the throttle backed off until at 6000 ft. and he finally managed a 7G pullout leveling off at 2500 ft.  His max speed was Mach 0.77.  Squadron Leader Anthony Martindale dove a Spitfire XI in a dive test and lost the propeller and managed to reach 620 mph (0.92) making it the fastest dive of a plane that took off and started a dive with a propeller as its sole source of power (I believe).  That same plane had previously made a dive at 606 (0.89) and landed with all its parts.

 

So, it would appear propellers aren't a reliable way to supersonic speed.  lol

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