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The future car.
This is where I think cars will eventually be.
The obvious:
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Better aero and lower rolling resistance tires. These two design improvements will allow higher speeds while consuming less energy in maintaining those speeds. The original design criteria for the Interstate system was 70 MPH. They were based on the autobahns, and the Pennsylvania turnpike, two roads that were conceived for high speed intercity transportation.
Considering the evolution of auto technology (or you could argue the lack of same), it should be possible to travel today's Interstates at 80 MPH. Understand the best solution to less congestion is to shorten trip lengths by increasing average speeds.
The evolution of power trains:
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My belief is that the secret is really in the power train. To accomplish power transfer to the wheels the obvious solution is to apply power directly to the wheels themselves. Ferry Porsche thought the same thing in 1900 when he designed an electric car with in wheel drives. While it may not have been practical in 1900 with existing technology, it certainly is possible today.
My preferred pathway is hydraulic in wheel drives. To Quote Charles Gray, one of the people involved with the EPA hydraulic hybrid work, "I can hold a 500 horsepower hydraulic motor in my hand". Obviously you don't need 2000 HP at the wheels of a 4 wheeled vehicle, but the point is, you can replace the exiting brake systems with regenerative hydraulic pump-motors and totally eliminate the rube goldberg existing system of power transfer through numerous components that have changed little in at least 75 years.
Pop told me he used to stay in formation in his B17 by adjusting the boost through the waste gate in the 4 turbos. He could control the mixture, and prop pitch, but when the single point electric boost controls were installed pilots found they could leave the mixture controls alone.
Much like the C130 whose turbines spin at a relatively constant speed, the thrust is controlled through blade pitch. Its a form of variable transmission.
Acceleration in a car should be through energy storage and application through a infinite drive system.
Driving a car directly through the engine and a direct mechanical connection to the wheels is the principle reason why we see efficiencies of 18% overall when the potential is twice that amount.
Disconnecting the engine from the wheels allows engine operational cycles that maximise BSFC properties of any engine. Its surprising how close the BSFC maps are from engine to engine when load and RPM are optimized.
The engine:
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Disconnecting the engine also allows engine downsizing without short term performance penalties. The problem arises when you need longer sustained applications of power. On level terrain this is no an issue but in mountains it becomes a huge disadvantage to have a seriously underpowered car.
I see the solution as providing a method of supercharging the engine for short term higher power applications, the best example of which would be climbing a long steep grade, say 8% for 8 miles. That works out to an elevation change of about 420 feet per mile or 3200 feet total. There are more severe examples of sustained grades, but at some point you have to consider the overall cost of any basic design configuration for rare events.
We have discussed electric supercharging in another thread with a wide variety of opinions based on a limited amount of information.
Personally I like the idea of electric supercharging, because it can be a fairly lightweight component that requires no parasitic engine driven components other than the alternator.
That preference is no because I think its more efficient than either a turbo or belt driven supercharger. Frankly I do not know which is the most efficient.
My point is when you start to consider an vehicle where the engine is running only a small percentage of the time, you have to be capable of using the normal accessories without depending on the engine for power to operate the same accessories.
Electric power steering
Electric brakes assist
Electric air conditioning
Electric supercharging
Electric water pumps
Electric control of radiator coolant exit temperatures
can all be operated with a larger battery and alternator. I would prefer the alternator to be non belt driven, which would eliminate all fan belts. It could also be utilized to assist in acceleration if it was configured like the Honda Insight, but it would need to be clutched between the engine and alternator.
I also like the idea of engines without throttle control. It's nothing new, but when you choke off the air to an engine you reduce it's effective compression and efficiency. Throttle control would be unnecessary if you stopped trying to control vehicle speed by choking air off to the engine.
Idle elimination and low manifold vacuum elimination are two of the core reasons to eliminate the throttle in the engine altogether. Supercharging would allow engine downsizing for normal operations.
Argonne labs is experimenting with various methods of improving engine efficiency. Their goal is 60%, higher than the most efficient engines used today unless you use waste heat for energy generation. Two thirds of the energy content of the fuel in your car is currently wasted. I think we will see 60% and possibly 70% in the next 20 years.
Electric drives have seen a lot of funding in the last 30 years, with most of the money spent on battery development. Driven by the space program, with cost as no object, some very efficient battery systems have been developed. Battery energy density is the problem, with cost being the second major obstacle to a practical electric vehicle.
Another negative in battery electric vehicles is poor regenerative energy recovery, which is function of the number of changes in the energy state and the fact that batteries can not absorb energy as quickly as they can apply the same energy. Rapid stops demand huge energy conversions. For that reason I think that portion of the future vehicle may require a combination that includes a hydraulic energy recovery system. it could be flywheel based like the current KERS system that is finding its way into Formula 1 racing, or it could be a hydraulic accumulator. One of the key points to understand if any vehicle is bleeding energy constantly. The necessity to recover and reapply energy, in almost every case requires only a single cycle of regeneration and reapplication. Hydraulics are ideally suited for that operational state.
regards
Mech
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