Hello Paul,

 My name is David, I am from Spain and I'm doing a master's degree about
 motorsports in Epsilon Euskadi's facilities (METCA, that is managed by
 Sergio
 Rinland).

 I have been reading your website and i find very interesting the Turbo
 Compounding in order to improve the engine performance and efficiency,
 that's why i would like to do the master's project about it.

 Sergio Rinland suggested me to get in contact with you in order to find an
 automotive company which is developing it, so i could help them in that
 developing work.

 I have seen that the Turbo Compounding could be applied as it is in the
 examples you show in your website, to transmit the turbines torque to the
 crankshaft of the engine, but also, i think it could be interesting to use
 it as a "battery charger" for a hybrid car.

 I hope you can help me, because i think this is a very interesting project
 that could help the automotive industry in the nearest future.

 I look forward to hearing from you,

 Kind Regards
 David Garcia


 Yes I know Sergio Rinland. I met him at the World Motorsport Symposium in
 Oxford.

 It can be used as a battery charger but perhaps that is not the best way to
 use it. Each time one converts energy from one form to another there are some
 losses.  These losses rapidly multiply. If a generator is 90% efficient and
 a motor is 90% the over all efficiency becomes only 81%.

 Ultimately a car requires mechanical energy to move. The first thing one
 must do with a turbo compound is to convert the momentum and heat energy in the
 exhaust to mechanical energy. It is best to use that mechanical energy
 directly to move the car for the reasons stated above.

 Turbo compound truck engines are rapidly
 becoming the norm. Turbo compound ship engines frequently utilize the waste
 energy in the exhaust to generate electricity for use on the ship. Large
 gas turbine power plants use the exhaust energy to generate steam for steam
 turbines which increases the overall plant efficiency to over 50%. These
 are called "combined cycle" or "bottoming cycle" power plants.

 A typical car engine is less than 35% so herein lies  the opportunity to
 drastically reduce the world wide consumption of hydro carbon fuels. The
 piston car engine loses 20% of the energy in the exhaust to aerodynamic and
 heating losses on the exhaust valve. Of course over 50% of the energy in the
 fuel burned in the IC is lost to the exhaust.

 The Wankel rotary by comparison is "piston ported" so to speak so these
 exhaust valve loses are drastically reduced. It has no exhaust valves. It is
 true the current Wankel rotary design is 5 to 10% less efficient than the
 current piston engine but it still remains the best choice for high power to
 weight ratio turbo compound engine used to power both airplanes and cars.
 The turbo compound Wankel rotary would become the most efficient internal
 combustion engine suitable for vehicles. Engine weight is a key factor in
 the overall empty weight of both airplanes and cars. A lighter vehicle is a
 more efficient vehicle.

 The aircraft and recreational boat application of the turbo compound is
 trivial while the real challenge is the wide dynamic range of the passenger
 vehicle engine.

 Paul Lamar


Hello Paul;

So, as I was wondering, having in account the losses of converting the
mechanical energy to electrical energy it's a better idea to use the
mechanical energy of the turbine directly.

You think it is a good idea to apply this technology to passenger vehicle
engines. Do you know if any automotive company  developing it so I could
get in contact with them and try to collaborate in that developing process?

In case I could not get in contact with any company I would like to develop
it on my own, but I don't know if you could help me with my doubts during
the developing process. I don't have too much experience on this yet.

Thank you very much,

Kind regards
David Garcia

Using the mechanical energy directly means one does not have to carry
the extra weight of a battery, generator and electric motor. Also there
is a world wide limited supply of lithium for advanced batteries.

The best approach to the problem is use two engines. One small one
for cruise on the autobahn and a larger one for acceleration and
hill climbing. As you can see from this chart the optimized BSFC
island of a large engine is too far, in terms of throttle opening
(manifold pressure) and RPM, from constant speed flat road
load requirements. This has been mitigated somewhat in modern cars
by using a lower reduction ratio (lower cruise RPM) in top gear.
Most of the improvement in MPG has come from this practice despite
large weight increases due to government crash requirements.

This dual engine idea can and has been implemented by partially shutting
down a few cylinders in multi cyclinder piston engines. One good  way of doing this is allow the exhaust or intake valve to remain open or closed while that
cylinder is not needed. Since the piston is still going up and down there
are still pumping and friction losses from the shut down cylinders.

The Wankel on the other hand is unique in the fact the straight eccentric
shaft can be made concentric with a smaller interior shaft. That would
allow the larger engine to be completely shut down.

The Wankel also has the turbo compound advantage of no exhaust valve to reduce
the energy in the exhaust stream so it is ideal for the turbo compound configuration. NASA studied the Wankel turbo compound engine in this
technical paper:

http://www.rotaryeng.net/NASA-Paper-turbo-compound-rotary.pdf

NASA concluded it was possible to recover 80 free HP from a
Mazda sized rotary engine with no increase in fuel burn.
Unfortunately NASA ran out of money before this could
be tested in hardware.

Here is a design that implements this dual Wankel engine approach. Small
and large Wankel engines are available off the shelf to build a prototype
for testing. The small engine would be turbo compounded to lower the
fuel burn for the 95% of the time the car is in cruise mode.

http://www.rotaryeng.net/RX8.html
http://www.rotaryeng.net/RX8-TC-eng3.html

So far to my knowledge no car company is working on this turbo compound
idea. Mazda is ideally positioned to do this so you might try
contacting Mazda.

I will be glad to help including a trip or two to Spain
if necessary at my expense.

Paul Lamar