12
In 2011 I gave a talk on turbo compound at the
World Motor Sports Symposium.
http://www.rotaryeng.net/turbo-compound.html
The Formula One governing body mandated it in 2014.
Race engine Technology magazine had a an article in the aug 2017
issue.
Here is most of it. The MGU-K is the motor/generator on the rear axle
and the MGU-H is the motor/generator on the turbo charger. It is
basically a complicated hybrid system extracting energy from braking
as well as from the the waste energy in the exhaust. A F1 car is either
on the gas or on the brakes. There is no cruising.
They are now claiming an engine efficiency of 50% which is up from 30%
for 99.9999%
of the engines in the world.
These engine have exhaust valves which dissipate 20% of the recoverable
energy in the exhaust. Of course the rotary has no exhaust valves and that
is why they are so loud.
"kinetic energy under braking and deploys it under power) the task is
relatively straightforward. Its output is capped at 120 kw, so the main
goals in improving this component of the powertrain .are reducing its
weight, increasing efficiency and ensuring reliability. The latter point
is not a given though: even in 2017, after four years Qf development,
manufacturers are not immune from MGU-K failures.
As of 2017, the subject of mass reduction is also something of a moot
point, as the FIA has included limits on the weight of certain hybrid
components in the technical regulations, including the MGU-K at 7 kg and
the MGU-H at 4 kg. However, these regulations were based around the
lightest units in the field (assumed to be those from Mercedes) so it
would be reasonable to expect that other manufacturers are striving to
reach those levels.
The efficiency of the units remains an area of considerable interest, as
greater efficiency not only ensures that energy is used more
effectively, it can also improve performance in other areas. Notably,
higher efficiency means less heat rejection and thus a lower demand for
cooling, which in turn can reduce overall vehicle drag.
Greater motor efficiency can be found in various ways, for example by
using better magnetic materials (for the permanent magnets) and
improvements in aspects such as the motor windings (both their form and
materials) to reduce electrical losses.
Maximizing the use of the MGU-H, which recovers energy from the waste
exhaust gases, is the task that has most vexed engineers in Formula One.
Briefly, the MGU-H is an electric machine that is directly linked to the
engine's turbocharger system. In operation, it uses excess energy in the
exhaust gases (once the required boost level, is reached) to generate
electricity. I Its role can also be reversed, and the motor used to spin
the turbine I at a set rate, effectively removing turbo lag. It is this
use, coupled with
the prescnce of direct injection, that makes the current generation of .
recovery and deployment strategies can have a substantial effect on
overall lap time.
Manufacturers have taken
different routes to integrating the MGU-H system with the turbocharger
elements and the overall powertrain architecture. The one most talked
about is Mercedes' split system, whereby the MGU-H sits in the vee of
the engine with the compressor located at the front of the block and the
turbine
at the rear. That is in contrast to the Renault and Ferrari approach,
where the MGU is sited in the vee of the engine with the turbine and
compressor to the rear.
Honda meanwhile has run
two set-ups. Initially it placed the
engines the most responsive ever to the drivers' throttle inputs.
It is also significant that the MGU-H can feed power directly to the
MGU-K, bypassing the battery. That is important because there is a limit
of 4 MJ on battery energy output over a lap, and 2 MJ input, so the
MGU-H allows for the MGU-K's 120 kW to be deployed for a far greater
proportion of a lap than if battery energy alone were in play.
The goal is therefore to ensure that the MGU-H can supply enough energy
for the MGU-K to be used at any point in a lap where the car is not
traction-limited, without undue detriment to the IC engine's
performance. With that in mind, it is easy to see why the mapping of the
MGU-H and IC engine are so intertwined and how varying energy
turbine at the rear of the engine and sited the MGU and compressor
within the vee. The result was a very compact package, but it was
fraught with reliability issues, with power also stifled by the small
size of compressor that could be fitted in the vee. For 2017, it has
followed Mercedes' lead and placed the compressor on the front of the
block.
That makes for a slightly longer engine overall, but according to the
manufacturer it allows a larger compressor unit to be used and helps to
lower the center of gravity of the engine considerably.
The consensus across the manufacturers is that the MGU-H is one of the
hardest elements of the hybrid systems to get right. First, it is an
electric machine that must be able to spin at up to 125,000 rpm "
Paul Lamar
------------------------------------------------------------------
Please add your questions or comments at the end of the thread.
Not the beginning.
I am going to enforce that rule. If people don't do that it will not be
forwarded.
My ISP changed the rules.
The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove you. ACRE NL web
site.
http://www.rotaryeng.net You Tube
http://tinyurl.com/beqqxas
Copyright 1998-2017 All world wide rights reserved.
