| An article by Karl Ludvigsen in
the December 2003 issue of Automotive Engineer has re-opened old arguments
concerning the swept volume of the Wankel engine, especially so within
Lotus Engineering where one of the authors of this piece has previously
worked on Wankel engines at Norton Motors.
Although Lotus itself has not worked on Wankel engines as they are currently
perceived, and is largely known for work on state-of-the-art 4-stroke
reciprocating performance engines, it did pursue a Brayton cycle engine
utilising what would be widely recognised as Wankel geometry.
It also has a long history of automotive 2-stroke development (conventional
and Free Piston) and of unusual pressure charged engines, including the
development of one of the most ambitious charging systems ever conceived
for an F1 engine: compound charging with both an axial compressor and
variable geometry turbochargers. The incorporation of a direct injection
gasoline fuel system controlled by piezoelectronics made this an extremely
advanced engine of any genre in the mid-1980s.
On the vehicle engineering side, Lotus has successfully raced cars powered
by gas turbines, has engineered road cars with fuel cell engines and has
recently enjoyed victory with a racecar with no engine at all.
Regardless of Lotus’ image, there is no particular affinity to any
specific type of powertrain, and it has a certain vantage point which
some of its competitors tied through branding to certain engine layouts,
for example, may not have.
The Lotus philosophy is one of performance and efficiency through light
weight and the intelligent application of technology. This heritage has
led to the current situation in the racing world where virtually all single-seat
racing cars are built to a Lotus template (the monocoque chassis, adjustable
suspension, ground-effect aerodynamics, structural engine, even sponsorship
– all of these, and more, were Lotus innovations).
How to progress efficiency as a key goal
The lively debate sparked by Karl Ludvigsen’s Wankel engine article
served to bring into focus the conclusion that he himself reached: that
there are many better and more relevant ways to compare powertrains (and
by extension, the vehicles to which they are fitted) than the swept volume
of a heat engine. Indeed, this may well become moot if the fuel-cell engine
becomes a viable proposition for passenger cars.
So, what is the point of any argument related to swept volume in the modern
world? At one time swept volume had a certain relevance in taxation terms,
but recently the CO2 production of a vehicle has been introduced as a
more environmentally relevant basis for taxing road vehicles. This not
only takes into account the efficiency of the engine but also that of
the vehicle to which it is mated – obviously aerodynamic drag, rolling
resistance and mass all play a significant role in determining the amount
of fuel a vehicle consumes – and hence its CO2 output.
In terms of global warming, this new comparison of vehicles based on their
CO2 output is very important indeed, and should be the ultimate decider
of efficiency, as it is to the person paying the fuel bills, if they choose
to take any notice.
In the European Union, ACEA (the car makers’ association) has voluntarily
adopted a target of 140g per km for the new fleet-average vehicle CO2
emission level by 2008, a reduction of over 15% from the level of 2000.
Progress was being made towards this goal, but very recently an interesting
trend has emerged – the average figure based upon units sold is
rising. The reason for this is very simple: for the majority of people,
fuel economy is not very high on their list of priorities when purchasing
a car, and is somewhat below the vehicle’s performance, styling
and image.
How to rationalise these issues? How to make fuel efficiency attractive
to both consumers and manufacturers as a true marketable quantity? One
possible answer is through motorsport.
A greener formula for powertrain advancement
Consider what is championed as the pinnacle of four-wheeled motorsport,
Formula One. We are in the middle of one of the longest periods of stability
in the rules ever known. To achieve that stability, however, the price
has been high.
Incremental gains come at the expense of millions of dollars of development
funding which manufacturers understandably loathe to see wasted if a competitor
has a good idea making what has gone before obsolete. Hence, as time goes
on, internal pressure groups are having the effect of making the rules
more and more restrictive, which in turn has the effect of making incremental
gains harder to achieve, meaning proportionately more money has to be
spent to move forward.
It is a vicious circle that is having the effect of removing the spectacle
and making the series less and less relevant in engineering terms. In
the arena of powertrain, for example, the only real avenue of development
is ever-higher rates of engine revolution which has little equity in terms
of technology transfer to road cars. Formula One engine designers seek,
primarily, to maximise the air pumping rate of the engine whilst maintaining
fuel preparation and combustion efficiency, and minimising friction levels
at these elevated speeds.
There is an argument that more open rules make the engineering and, therefore,
to many people, the sport itself, more interesting. Would it not be a
noble thing for the FIA to make the regulations force competitor manufacturers
to consider fuel consumption, and hence CO2 generation, as a key driver
on the type of vehicle they field? After all, is it not axiomatic that
racing vehicle designers should strive for maximum vehicle efficiency?
But how to change the regulations to this end? Some motorsport formulae
depend on air restrictors to achieve a notional parity of power output,
but if fuel efficiency of the whole vehicle is our aim (and hence a ready
transfer of CO2-reducing technology to the road car arena) then air restrictors
should be avoided at all costs. This is because with an air restrictor
the most powerful engine will be the one that consumes air with a slightly
rich fuel-air ratio.
Conversely, the most fuel-efficient forms of powerplant are those which
run lean – the diesel, gas turbine and (in theory) the fuel-cell
engine, whose specific air consumption is worse. We should look at ways
of controlling how much fuel energy is consumed in the race, not how much
air.
Unfortunately, fuel flowrate restrictors also have the effect of seriously
compromising one of the key fuel efficiency technologies: hybridisation.
Some forms of hybrid engine (the gas turbine-electric for instance) might
be more fuel-efficient when running the prime mover at full load for the
minimum amount of time. To limit the rate at which they can consume their
fuel might therefore be to impose an artificial restriction on efficiency,
and this is our prime aim, remember.
Given that limiting the rate of consumption of either air or fuel is a
restrictor on overall vehicle thermal efficiency one could alternatively
look at limiting the fuel chemical energy a racing car can use during
a race. This would then have the effect of seeking to maximise the efficiency
of energy conversion and usage for the whole vehicle over a journey (the
race), and this is exactly what we are seeking to achieve.
So, considering all of the above, one proposal could be as follows:
Throw the rules wide open by allowing teams a fixed quantity of fuel
energy for a race.
Allow any of several relevant fuels for the real world – gasoline,
diesel, CNG, hydrogen – since this approach will allow stochiometric
spark-ignition engines to compete with diesels or gas turbines – and even fuel cells.
Address the hybridisation issue by explicitly allowing it – the
aim is to promote the efficiency of the whole vehicle, in the same way
low CO2 vehicles are championed. Allow refuelling, by any means –
perhaps by cassette tanks for hydrogen-consuming vehicles. As Lotus’
founder Colin Chapman once suggested, limit the car’s dimensions
solely by stating that it must fit inside a box of a mandated size. Remove
weight limits – upper and lower.
State that the driver must still control the car’s speed and direction,
not a computer.
Hybridisation and how to limit the energy stored in the ‘buffer’
will take some thought, but the broad aim would be to have the energy
stored in the buffer at the end of a race the same or greater than that
with which it started. This is analogous to what is mandated in certification
tests. In the spirit of openness the energy storage media could be electrical,
mechanical, pneumatic or hydraulic – it is common to see the word
“hybrid” and automatically think of electricity.
However it is policed, hybridisation should be encouraged, and so the
total quantity of fuel energy allowed for a race should be somewhat less
than an F1 car currently uses during a race – say 25% less. If a
regenerative braking system and powertrain control system are doing their
job properly, the peak power produced by the car should be very similar
to what is presently the norm.
The entire powertrain configuration should be free. One can imagine four-wheel
drive being a very advantageous thing when one is attempting to capture
regeneratively as much energy as possible during a braking manoeuvre;
this must be especially so in a car with a very low centre of gravity
whose braking is evenly divided between the axles. In the interest of
pursuing vehicle efficiency it, and infinitely variable gearboxes, should
therefore be allowed. It also opens the door to manufacturers unwilling
to compete under the current constrained layout, configuration and drivetrain
rules.
With regulations similar to those proposed above, the millions poured
into Formula One would be more relevant than chasing down such blind alleys
as engine speeds fast approaching 20,000 rpm.
The involvement of fuel companies in Formula One might be seen to be threatened
by any or all of these changes. Perhaps this would have to be accepted
as a necessary price to pay in pursuit of a greater good. Using pump (or
supplied) racing fuels would not be a bad thing: road cars are not developed
solely to use a specific fuel, and indeed it is illegal for a manufacturer
to specify only one make of lubricant, let alone fuel. Again, adopting
this “high street fuel types only” approach is entirely relevant
to the way road car customers buy their fuel, and so could be argued as
nothing but a good thing. In this case, the fuel companies could actively
contribute to and learn from the formula as they release higher energy
content fuels into the marketplace.
A final point is that Formula One is the top technical formula. Unfortunately,
it is not the Constructors’ Championship but the Drivers’ Championship that is lauded as the most important. For the manufacturers
themselves, a rebalancing of the importance of the two championships would
probably be quite attractive since they, and the sponsors, pour in the
money and expertise.
It is very important that any fuel energy-based formula be relevant to
motorsport as well. Hence, arguing that the above should be applied to
sports cars only should be very carefully considered (though it could
and should be applied to sports cars as well, as a forcing house from
F1 into road cars, perhaps with requirements for homologation).
In 2007, the current regulations in F1 are due for revision. The possibility
discussed here is one option available to the FIA, the motorsport governing
body, and the Formula One Constructors Association, and moves towards
a more “green” formula have also been suggested by the Motorsports
Industry Association (see boxed section).
Of course, another option is to change nothing, or merely tinker with
the status quo, in the interests of placating the internal pressure groups.
This would be somewhat irresponsible as mankind starts to get to grips
with the effect he is having on the climate of the planet.
To argue that a grid full of F1 cars has little effect on global CO2 is
a fair point in detail, but the effect relevant technology development
through F1 could have on road cars makes such an argument fatuous and
arrogant in the extreme. The maxim “racing improves the breed” used to be true, but to claim that it still does now would be foolhardy.
It is time that the rule makers force the old maxim to be valid, and in
so doing recapture some of the pioneering spirit which used to be associated
with motor racing.
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