Engine efficiency

[Ken Fry]

Originally Posted by drmiller100

if the generator is 90 percent efficient, the charge controller loses 5 percent, battery loses 5 percent when charging, motor controller uses 3 percent, motor is 90 percent efficient, batteries cost 15,000 bucks, and you lose 10 percent in the power company's transmission and distribution, your cost per mile eventually starts to add up.

Absolutely. The Argonne Lab GREET tables give a pretty good accounting of the well-to-pump and well-to-plug efficiencies of various energy sources.

[user removed]

If you understand the hydraulic drive with an accumulator then this engine is the best method of creating hydraulic pressure at efficiencies of 55% or more. It also eliminates the encessity of running a pump with a separate engine. I would love to put one of these in my HH prototype.

In fact the whole site deserves attention.

Chiron Free Piston Engine

regards
Mech

[some_other_dave]

Originally Posted by pete c

how do they fall in the efficiency area? is there a reason they are no longer made other than prohibitive production costs?

Radial, or rotary? The Gnome is a rotary, where the crankshaft is solidly bolted to the fuselage and the rest of the motor spins around it. (Different from the Wankel rotaries to be sure!) The main reason it was successful was that the whole engine acted as a flywheel, which meant no extra (heavy!!) flywheel was needed. Engines at the start of WWI in particular needed a pretty massive flywheel to keep them running reasonably, and the rotary provided that with basically zero weight.

The efficiency was horrible, absolutely rotten. The mixture went in through the crankshaft (which was hollow for at least some part of it) and bounced around inside the crankcase. I seem to recall that it went into the cylinder, then back out again, then back in to be burned. Compression ratios were very low, and valve timing was just short of a joke. Not to mention the total-loss oiling system.

But the displacement was pretty large, and it was very light for an engine at the time.

Later aircraft often used other engine configurations. The Fokker D-VII, arguably the best fighter in the war, used an inline-6 water-cooled motor.



Radial engines were used throughout WWII because you could easily make them really big (3350 cubic inches, about 55 liters, in the twin-row Wright Cyclone!!) and relatively compact. They were also very resistant to damage and would fly for a while with large chunks missing, and had no radiator that needed both airflow and protection.

I don't know what the efficiency was on those, but I would be surprised if we found it was very good.

Packaging up a radial in an automobile is a definite challenge. They are very wide, and unless you have a tubular cross-section you wind up with lots of wasted space by the time you fit one in your vehicle.

BTW, the fastest aircraft of WWII generally ran liquid-cooled V12 motors. Except for the very few jets, but that's another story.

-soD

[gone-ot]

...regarding the Wright R3350 radial engine efficiency (from Wiki):

"...By this point, reliability had improved with the mean time between overhauls at 3,500 hours and specific fuel consumption in the order of 0.4 lb/hp/hour (243 g/kWh, giving it a 34% fuel efficiency)." [Wiki]

...color emphasis is mine.

...however, you have to remember that these engines were "turbo-compound" (both supercharged AND turbocharged), not just normal aspiration.

[user removed]

I think one of the most important improvements on the Wright engine was fuel injection.
The early ones had terrible fuel distribution problems which resulted in failures under high loads. FI corrected the distribution issues. Reliability skyrocketed.

regards
Mech

[NeilBlanchard]

Weight is not as critical as drivetrain efficiency or aerodynamic drag. The aero of the Jacobs 125cc motorcycle is about 80 pounds heavier than stock -- that is more than a third heavier.

Taller gearing and good aero = more than twice the FE.

Also, the X-Prize Knockout Round provides data that shows that drivetrain efficiency is the most important factor.

Aero drag is roughly 50-75% of the total load much of the time at normal speeds. And it is a total loss. Weigh means kinetic energy, so you can make use of it by coasting, so you only lose this energy to drag, or if you have to use the brakes.

Back on topic: I think the Prius (3rd gen) Atkinson cycle engine is up to 38% efficient? And some TDI diesels are 42% or maybe 44%?

Critical to raising the average efficiency is warm up time, and idling. Another issue is how to get the required electricity (for gasoline) more efficiently -- maybe by braking with the alternator? (I think Mazda will be doing this?) Reducing parasitic friction within the engine -- electric valvetrain maybe?

What about some of the new rotary designs? The geometry of a crankshaft can be improved, that's for sure.

[user removed]

Neil read my post # 52 above with the link to the Chiron free piston engine. I think they are in the neighborhood of 55% thermal efficiency. I also believe that is measured in the produced hydraulic pressure, which eliminates the engine driving a separate pump and the corresponding losses. I would absolutely love to have one of those in my prototype.

They also make a version that is a linear electric generator or alternator (not sure which). It can also run on many different liquid fuels.

Also read the section in the site about the electric hydraulic hybrid, something that I have tried to present for quite some time, incorporating regenerative efficiencies hydraulically that mirror your beliefs that electric motors are substantially more efficient than IC engines.

It will be interesting to see what happens in the next decade as development of batteries and IC engines will progress, probably at a very high rate. I see all vehicle efficiencies doubling in the next decade. It will be quite a show to watch.

regards
Mech

Neil, did you even bother to read the link I suggested in this post.

You claim 20% efficiency for an IC engine when accelerating.
That's a complete falsehood. IC engines are at their most efficient under accelerating.
You claim good efficiency in regeneration for an electric vehicle, then you claim they need no transmission, as well as basically claim they need no maintenance.
All false.
Make legitimate claims and DO the research you need to be educated in the topic when you make claims that are not substantiated by facts, most here know already. To make false claims about poor IC efficiency when the facts do not support your claim just confirms you do not want to make any unbiased comparison, in other words a biased agenda not supported by facts.

Fact. the linked article you seemed to ignore shows 55% efficiency for the Chiron motor.
Fact, an electric motor is less efficient from a dead stop, in some cases lower than the Chiron.
Fact. Even if you have an electric car you still have maintenance. Would you like me to list all the components that still will need replacement.
Fact.
Tires, axles, brakes, differential, shock absorbers, wiper blades, light bulbs, heater, air conditioner, alignment.
Fact. Consumer Reports tested the Leaf and it cost you 15% in electricity lost to charge the battery, that's meter to discharge of the battery, so you should reduce every claim by that amount, instead of evading the fact that I pay for fuel at the pump, and I get 100% of what I pay for, while your electric car only returns 85% of what you pay for.

I can continue for for the sake of some brevity maybe YOU should name the common parts on every vehicle you think do not exist on an electric vehicle.
Fact. A direct drive engine to wheel electric vehicle still needs a differential and its regenerative capability is 30% or less. Hydraulic Hybrids were 78% 5 years ago.

Fact. There is no way you can recover even 30% of decelerative energy in any direct drive electric vehicle, even with a 400 pound battery.
The reason your electric motor is simply not spinning fast enough to generate that kind of energy, and even if it could, that battery can not accept energy at that rate.

regards
Mech

[drmiller100]

Originally Posted by NeilBlanchard

Weigh means kinetic energy, so you can make use of it by coasting, so you only lose this energy to drag, or if you have to use the brakes.

ummm, no. You have to accelerate the weight from a stop. The weight drags every single second due to friction (primary loss of energy at slower speeds for cars).

What are you calling "drivetrain loss"??

[UFO]

Originally Posted by drmiller100

ummm, no. You have to accelerate the weight from a stop. The weight drags every single second due to friction (primary loss of energy at slower speeds for cars).

What are you calling "drivetrain loss"??

The marginal frictional loss is minor compared to the kinetic energy stored as moving mass that can be used to move with the engine off, balanced with the ability to operate the engine at its peak efficiency up the hills.

Drivetrain loss is heat generated by friction in the gears and hydraulics.

[Diesel_Dave]

Originally Posted by UFO

The marginal frictional loss is minor compared to the kinetic energy stored as moving mass that can be used to move with the engine off, balanced with the ability to operate the engine at its peak efficiency up the hills.

Drivetrain loss is heat generated by friction in the gears and hydraulics.

Weight doesn't help. I'll agree that the friction is fairly minor, however, weight doesn't help you through "kinetic energy" Sure, a heavier vehicle at the same speed does have more kinetic energy, but it takes more energy imput to accelerate the heavier vehicle. In theory, the two things balance perfectly so weight makes no difference, other than friction (assuming there's no brake loss involved). Of course, in the real world there's always going to be some braking and the weight hurts big time there because you have to use fuel to re-accelerate the weight, but don't get to reap the kinetic energy benefit of it before the stop.