KiloNewton/Pound foot of thrust into Horsepower units

[cjl]

So another point in the discussion. I was going through an article about a gigantic locomotive used as an ore carrier for mining. Apart from its size and design what was very unique about this machine was that it worked with a electric wheeler system where apart from the gear and clutch system that propels the vehicle there is also an auxiliary electric system drawing its power from an electric motor that is part of the engine power plant, and is coupled with the wheels to facilitate functions like braking, skid protection and the most interesting as an extra power above the gear system for the wheels through AC alternators and four AC traction motors (two in each axle).
https://en.wikipedia.org/wiki/BelAZ_75710
So is such a system applicable to aviation engines, especially high-by-pass turbofans? What I mean is, is the fuel-electric powerplant applicable to aviation or are the conventional mechanical systems most ideal and safest? If I am not mistaken, I don't think Fuel-electric systems make the engine any lighter in weight.

It's worth noting that for that vehicle, the electric system isn't auxiliary. Rather, there is no gear and clutch system at all. The 2 diesel engines simply power generators, and all vehicle motion comes from the electric motors attached to the axles. This saves a large amount of space, weight, and complexity since clutch and transmission mechanisms for that much power would be extremely large.

 

[Arjun Singh]

It's worth noting that for that vehicle, the electric system isn't auxiliary. Rather, there is no gear and clutch system at all. The 2 diesel engines simply power generators, and all vehicle motion comes from the electric motors attached to the axles. This saves a large amount of space, weight, and complexity since clutch and transmission mechanisms for that much power would be extremely large.

Perhaps I was a bit creative with my understanding of the spec. Does a hybrid power plant also improve the maintenance requirement of the assembly? I think it does.

 

[Arjun Singh]

Check out this machine. A cool helicopter design, quite radical in its form. Designed like a submersible and may have some key suggestions for ship design.
https://en.wikipedia.org/wiki/Sikorsky_S-97_Raider

 

[wolf1728]

You said
force=weight x acceleration

No.
force = MASS * acceleration

 

[CWatters]

I have heard that there is research being done into hybrid engines for aircraft but not my field. Google finds...

Rolls, Siemens and Airbus to put electric engine on BAE146...
https://www.bbc.co.uk/news/business-42152484

Boeing tie-up...
https://www.reuters.com/article/us-...ter-plane-to-hit-market-in-2022-idUSKBN1CA16A

https://www.experimentalaircraft.info/homebuilt-aircraft/electric-aircraft-engines-2.php

 

[Arjun Singh]

You said
force=weight x acceleration

No.
force = MASS * acceleration

So what would be mass of a body represented in let's say 10 kgs?

 

[A.T.]

So what would be mass of a body represented in let's say 10 kgs?

10kg

 

[russ_watters]

10kg

I was going to give this answer a like, but then I decided it was the easiest question ever asked in the history of PhysicsForums.

 

[Arjun Singh]

I was going to give this answer a like, but then I decided it was the easiest question ever asked in the history of PhysicsForums.

In tribute to this thread may I say that 10 kg is not its mass, that's its weight or an acquired downward force balanced by its center of gravity calculated by a pressure sensitive mechanical device, a resultant effect of Earth's gravitational field, atmospheric pressure and may we also add the effect of unseen matter or cosmic energy that may have variable effects on the interactive potential of a body of mass on different planets based on their precise location in the solar system. But to calculate an applied force on a body of weight 10 kg, weight would play the 'mass' unit. If I may say mass is actually the total volume of matter contained within a defined shape or body not including its planetary signatures. Am I right to some extent?

 

[russ_watters]

In tribute to this thread may I say that 10 kg is not its mass, that's its weight or an acquired downward force balanced by its center of gravity calculated by a pressure sensitive mechanical device, a resultant effect of Earth's gravitational field, atmospheric pressure and may we also add the effect of unseen matter or cosmic energy that may have variable effects on the interactive potential of a body of mass on different planets based on their precise location in the solar system. But to calculate an applied force on a body of weight 10 kg, weight would play the 'mass' unit. If I may say mass is actually the total volume of matter contained within a defined shape or body not including its planetary signatures. Am I right to some extent?

No. The kilogram is a unit of mass, not weight.
https://en.wikipedia.org/wiki/Kilogram

 

[Arjun Singh]

No. The kilogram is a unit of mass, not weight.
https://en.wikipedia.org/wiki/Kilogram

Then what is the unit of weight?

 

[russ_watters]

Then what is the unit of weight?

Newtons.
https://en.wikipedia.org/wiki/Newton_(unit)

 

[David Lewis]

I was trying to understand various engine output comparisons between various aircrafts in an attempt to understand what factors affect the type of an engine selected for a specific aircraft.

I assume you're talking about the power or thrust maximum ratings. Since the engine supplier doesn't know which propeller is going to be used, or other relevant variables, it's simpler in the case of propeller-driven aircraft to specify maximum rated power. The designer multiplies power by estimated propulsive efficiency to arrive at thrust available.

In addition to the max ratings there is also thrust and power output under operating conditions, which varies with throttle setting, airspeed, and other factors. Aircraft engine horsepower is not directly comparable with automobile engines. Cars use a different measurement protocol.

Aircraft engines tend to need high rpm and low torque,

True with jet engines. Piston engines and direct drive electric motors are often designed to provide lots of torque at low speed. A slow-turning propeller can produce thrust more efficiently.

So what would be mass of a body represented in let's say 10 kgs?

Confusingly, engineers often say mass when they mean weight. If a body is said to "weigh" 10 kg, it is understood colloquially to mean the amount of gravitational force the body would experience near the Earth's surface.

 

[Arjun Singh]

I recently came across an article about a car prototype with standard on road 4-wheel car design boasting of an engine to the scale of 50000 HP which sounded unreal. I am not able to find that article now, so perhaps it was a hoax. Still would such a machine have any practicality as the enough torque required to achieve maximum rpm possible for rubber tyre, on-road mobility at top possible speed can be achieved in let's say within 10,000 HP. So if I have to design a fast production worthy supercar, then I perhaps wouldn't use an engine powerplant beyond 8-10 thousand HP. Any comments?

 

[CWatters]

Short answer no. Not in a road legal car.

Just for info.. Googke says Top fuel drag racers are running 11,000HP or just over 8MW. They burn 11 gallons a second so even the fuel pump is wicked.

 

[Arjun Singh]

Short answer no. Not in a road legal car.

Just for info.. Googke says Top fuel drag racers are running 11,000HP or just over 8MW. They burn 11 gallons a second so even the fuel pump is wicked.

So what is the road legal HP?

 

[A.T.]

So what is the road legal HP?

Among road legal sports cars this one has a lot HP:

https://de.wikipedia.org/wiki/Bugatti_Chiron

I don't know about other types of vehicles though.

 

[CWatters]

Most of the top supercars are in the range 750-1400bhp or in new money around 500kw to 1MW. What I meant above is that there isn't really much if any opportunity to reach those power levels on public roads, only on track days.

 

[cjl]

There's no real legal limit, other than that it becomes increasingly difficult to meet any kind of emissions standards and reliability. That having been said, I bet you're thinking of the (claimed) 5000 horsepower Devel Sixteen. I'll be surprised if it ever actually happens though...

 

[Arjun Singh]

Among road legal sports cars this one has a lot HP:

https://de.wikipedia.org/wiki/Bugatti_Chiron

I don't know about other types of vehicles though.

There's no real legal limit, other than that it becomes increasingly difficult to meet any kind of emissions standards and reliability. That having been said, I bet you're thinking of the (claimed) 5000 horsepower Devel Sixteen. I'll be surprised if it ever actually happens though...

That's a cool car. Saying the obvious, a lot to depend on development of road networking suitable for high speed cars, for them to become production staples. Let's see how the progress happens. Currently the present public commute systems likes buse networks, need a serious upgrade in India for super cars to really get proper torquing opportunity :) Will do some research on cool public commute engines and share for comments.

 

[cjl]

With that car, it's not a case of road infrastructure. It's that 5000hp is likely not possible in a way that would be either pleasant to drive or remotely reliable. It's not that hard for a modern engine to make 5000hp for a few seconds on a dyno, but it's a very different thing to make it so you can drive it 10,000 miles without a complete engine rebuild.

 

[Arjun Singh]

I was procrastinating on a fuel cell technology based on non combustion hydrocarbon fuel to run electric cars. Seems futuristic but did find some studies on this topic. Anything on fuel cell tech except hydrogen fuel? No google links, just self articulated stuff.

 

[Arjun Singh]

With that car, it's not a case of road infrastructure. It's that 5000hp is likely not possible in a way that would be either pleasant to drive or remotely reliable. It's not that hard for a modern engine to make 5000hp for a few seconds on a dyno, but it's a very different thing to make it so you can drive it 10,000 miles without a complete engine rebuild.

On road (Not race course) top speeds may accommodate maximum speeding of 150-200 mph in bursts, that too on specially built speedways, if I am not being conservative. So a 5000hp engine would run let's say on 10-15% output power on average using the momentum of the vehicle. No matter how powerful an engine is, there must be some scientific RPM limit for on-road driving right? I wonder what speeds would a 5,000 HP engine would extract in full throttle?

 

[cjl]

It's really only constrained by money and reliability. Also, horsepower isn't just for top speed - it also impacts acceleration. Very few people ever reach the top speed of their vehicle, but many people do use 100% of its power.

 

[Arjun Singh]

https://www.boeing.com/features/2018/08/737max10-landing-gear-08-18.page
Boeing is introducing a new landing gear feature. Have seen another design with similar mechanism where the landing gear with two pairs of wheel extend horizontally with advanced landing and takeoff pattern.

 

[sophiecentaur]

jet engines just move air.

Are there any straight jet engines used these days? I thought they were more like Fan engines these days
- quieter and at least as efficient.

 

[Arjun Singh]

Are there any straight jet engines used these days? I thought they were more like Fan engines these days
- quieter and at least as efficient.

Elaborate.

 

[cjl]

Turbojet engines have 100% of the flow pass through the core of the engine, where it is heated (by burning fuel), just enough power is extracted to power the compressors, then it is passed through a nozzle to accelerate it out the rear of the engine. These are fairly low thrust and very inefficient until you get up to extremely high speeds, and I don't believe they're used at all any more even on things like jet fighters. Turbofans add additional turbines after the combustor to extract more energy from the core flow, and they use this to power a large front fan. This greatly increases thrust and efficiency at low speeds, at the cost of high speed performance. Since we aren't flying around at mach 2 all the time, this is a very worthwhile tradeoff. Even modern fighter jets use turbofans, but they use much smaller front fans with a much higher proportion still flowing through the core in order to keep the high speed performance acceptable.

 

[Arjun Singh]

Turbojet engines have 100% of the flow pass through the core of the engine, where it is heated (by burning fuel), just enough power is extracted to power the compressors, then it is passed through a nozzle to accelerate it out the rear of the engine. These are fairly low thrust and very inefficient until you get up to extremely high speeds, and I don't believe they're used at all any more even on things like jet fighters. Turbofans add additional turbines after the combustor to extract more energy from the core flow, and they use this to power a large front fan. This greatly increases thrust and efficiency at low speeds, at the cost of high speed performance. Since we aren't flying around at mach 2 all the time, this is a very worthwhile tradeoff. Even modern fighter jets use turbofans, but they use much smaller front fans with a much higher proportion still flowing through the core in order to keep the high speed performance acceptable.

You just differentiated high bypass and low bypass jet engines right? If I am not mistaken 4th generation fighters are all working on turbojets. Is turbofan the 5th generation upgrade? Also turbofans are bulkier than turbojets ain't they?

 

[russ_watters]

Are there any straight jet engines used these days? I thought they were more like Fan engines these days
- quieter and at least as efficient.

Probably, but either way I consider that semantics. A turbo fan "just moves air" even if some is bypassed around the jet part. Does that make it similar to a turboprop or turbo shaft on a helicopter? Perhaps. Yes, the line between types of engines and naming conventions can be blurry.