Massive Yet Tiny (MYT) engine

[xxChrisxx]

I was wanting to talk about the efficiency of converting oil to forward motion of a vehicle.

Yes the conventional ICE is rather convenient, but it is embarrassing that 65% of that energy you put into the car is wasted. Inventors are motivated to keep trying new ways to convert that energy because the current ICE conversion losses are terrible.

Even a steam engine can do up to 50% http://en.wikipedia.org/wiki/Engine_efficiency#Steam

It's the nature of the beast of a heat engine. It's not embarassing, it's just physics.

[JohnsonsEvilTwin]

Talking of the losses incurred through heat, Im sure there are some creative ways of capturing this loss with a generator of some sort?

Thereby increasing the efficiency of the ICE from its current 35% to a higher figure. Also, does this 35% figure factor in the recuperative tech like stop/start systems and KERS-like regeneration under braking?

[Richard]

The 35% is for an engine sitting on a test bench - I should point out it is a very broad brush round number considering the range of ICE types, sizes, and fuels!

Whatever method is used (rotary or pistons or snake oil) you quickly realise that exploding oil in a closed container isn't a very efficient way to convert the energy. Bolting on heat recovery and other means of scavenging wasted energy makes the engine impractically large and complex for a car.

I think a gas turbine might be better, but that's not going to fit in a nippy city car.

[andylaurence]

I think a gas turbine might be better, but that's not going to fit in a nippy city car.

I think it might.

[tok-tokkie]

But is that not why F1 is going to force the teams to use Heat & Kinetic energy recovery? To make the devices small and implementable on production cars thereby doing something about the 60% odd lost. I favour a fuel limit for the race & any engine & recovery system the teams choose. MYT is not addressing the fundamental problem of using the energy presently wasted.

[JohnsonsEvilTwin]

But is that not why F1 is going to force the teams to use Heat & Kinetic energy recovery? To make the devices small and implementable on production cars thereby doing something about the 60% odd lost.

Exactly. Energy recovery is where "its at". All car makers are refining existing systems to be even more efficient, and we will even have a 55mpg S-Class Merc in a few months utilising the latest such tech.
Who would have thought a 2 plus ton luxo barge can achieve that in real world driving conditions and still hit 62 in under 8 seconds?
ICE is not dead, it still has yet to reach its zenith when you look at the recovery system tech being developed.

As MEP said, the thermodynamic principles are unchanged and so therefore is efficiency. So MYT may sound great on paper but delving deeper there are basic laws that make this concept unsound.

I favour a fuel limit for the race & any engine & recovery system the teams choose.

This will be fantastic to see. All out tech warfare with a very positive benefit to the manufacturers, sport and environment. Definite thumbs up from me on this.

[xxChrisxx]

But is that not why F1 is going to force the teams to use Heat & Kinetic energy recovery? To make the devices small and implementable on production cars thereby doing something about the 60% odd lost. I favour a fuel limit for the race & any engine & recovery system the teams choose. MYT is not addressing the fundamental problem of using the energy presently wasted.

This is the problem with using the word efficiency for different things. People see a 35%-40% efficiency and think CHRIST! we are wasting over half of the energy available. This is true from an input - output perspective.

HOWEVER!

Due to the 2nd law of Thermodynamics. A certain percentage of the heat potential from the engine simply isn't available to do work. It cannot be used or recovered. This is a stone cold fact and can't be got round as it's a fundamental principle of physics.

A better way of looking at this is % utilisation of energy that is thermodynamically available to do work. This can be found by the ideal otto cycle for SI engines and the Diesel cycle for CI engines.


EXAMPLE:
Calculate the thermal efficiency of an SI engine with compression ratio 10:1. Using the ideal Otto cycle we can calculate the maximum possible thermal efficiency. This calculation applies to any configuration of engine that uses the Otto cycle.
Method of reaching the efficiency calculation:
http://web.mit.edu/16.unified/www/SPRIN ... ode25.html

nmax = maximum possible thermal efficiency.
nmax = 1-(1/CR^(gamma-1))
nmax = 1-(1/10^(1.3-1))
nmax = 1-(1/10^(0.3))
nmax = 0.498812766

So for any SI engine using the Otto cycle (4 strokes) with a CR of 10:1. The maximum efficiency is 50%.

So out figure of 40% total efficiency is acutally 40/50 = 80% of maximum.
Leaving 20% available for recovery.

Still quite a lot, but only a third of what is commonly thought to be available for recovery.

PLEASE NOTE THAT MANY TEXTBOOKS WILL USE A GAMMA VALUE OF 1.4. WHICH INDICATES A CYCLE OF AIR ONLY. Leading to a maximum theoretical efficiency of 60%.

[tok-tokkie]

I am interested in that 2nd law of thermo reply. I can understand that a steam engine can't extract all the available energy because it can't reject energy to -273°C so the available energy is very much less than the total energy.

But in an internal combustion energy about 33 % goes out via the crankshaft, 33% down the exhaust & 33% out via the cooling system. It is a long time since I was at varsity so I would have to study your answer but I wonder how it covers the second two 33% that I listed & which Todt is wanting to reap as best as possible.

[nikkiwade]

very informative

[Edis]

While I agree with the naysayer posts above, it is frustrating that we can only extract 35% of the energy we put into our cars.
So it is natural to think that the reciprocating piston engines have taken us down a cul-de-sac. Why do we insist on carrying around all these silly inefficient power stations in our vehicles?

The more efficient method is to consolidate energy capture into a central place running at maybe 75 or 80% efficiency and add in some “free” energy from the sun & tides to give you say 90%. Then distribute the captured energy to automobiles with hydrogen or electricity, say 50% transmission losses. That’ll mean oil to car efficiency of say 45%.

OK that’s a bunch of guessed numbers, but the technology exists and I can demonstrate it without the need for compressed air.

The average efficiency of an electric powerplant is just above 30%, incl. transmission losses. So if we assume that the efficiency of an electric car is 60% the total efficiency is just about 19%, just a few points higher than the efficiency of a car with an internal combustion engine (for a regular gasoline car we can assume an engine efficiency of 20%, and an efficiency of 80% to extract the oil and make the gasoline which gives a total efficiency of 16%).

The only powerplants that can reach the efficiencies you're claiming are hydroelectric powerplants. All powerplants that convert heat to power have an efficiency of 60% (state of the art combined cycle gas turbines) or less. A state of the art steam turbine plant (Rankine cycle) offers an efficiency of just below 50% with a steam temperature of about 600 degC. Large diesel engines offers similar efficiencies, smaller diesels are in the 40-45% efficiency range. Commercial solar cells offers an efficiency of 15-20%.

So even if you combined electric cars with combined cycle gas turbines the total efficiency, from oil to wheels will just be 36% (0.6*0.6 = 0.36). If hydrogen were used as an energy carrier the losses would be even greater. At the same time, costs would be higher. It should however be noted that oil is generally not used for regular electricity production.

There is also no "free" energy. Energy always comes at a cost.

[flynfrog]

sorry nothing to add at this time but its threads like these that are missing form F1T. Its stuff like this that brought me here in the first place. =D>

[MuseF1]

sorry nothing to add at this time but its threads like these that are missing form F1T. Its stuff like this that brought me here in the first place. =D>

+1

[Richard]

All powerplants that convert heat to power have an efficiency of 60% (state of the art combined cycle gas turbines) or less.

I'm thinking of CHP plants where waste heat is recovered for domestic of industrial uses. Don't they get higher efficiencies?

[xxChrisxx]

All powerplants that convert heat to power have an efficiency of 60% (state of the art combined cycle gas turbines) or less.

I'm thinking of CHP plants where waste heat is recovered for domestic of industrial uses. Don't they get higher efficiencies?

Utilisation and efficiency can't be directly compared, althought they superficially appear to be the same thing. Electircal generation efficiencies will be about the same. In CHP plants the waste heat is then used.

So it's not really efficiency, but is an increase in utilisation.

[Richard]

Indeed - I am muddling up efficiency with overall utilisation.

What would be a realistic best practice utilisation?