DIESEL CLEANS UP ITS ACT
A CONSORTIUM of UK engineers from academia and industry is about to
conclude a project that could pave the way for a radical new design for diesel
engines, which combines the efficiency of diesel with the cleanliness of petrol
engines. The project, led by heavy-duty plant manufacturer Caterpillar and
co-funded by £1.5m from the Technology Strategy Board, is focused on large
engines but in the long term could also be applied to passenger vehicle engines.
The aim is to develop engines based on homogeneous charge compression
ignition (HCCI). In most diesel engines fuel is injected directly into the cylinder
and compressed, increasing the temperature and density until the mixture
combusts at the fuel-air boundary. This leads to very hot combustion, which
produces nitrous oxides and particulates that must be removed from exhaust
gases. In HCCI, however, the fuel is dispersed evenly throughout the cylinder in
a fine mist to produce a homogeneous mixture of fuel and air. When this is
compressed, it combusts in several places simultaneously, burning efficiently at
a lower temperature and producing minimal nitrous oxide or particulates.
Although HCCI has been demonstrated in static engines that operate at a
constant load, it does not work if the engine has to change its power output,
which happens when a vehicle accelerates or goes up a gradient. ‘In a real-world
situation, you never stay in a stable load state for more than a couple of
seconds, so HCCI is currently completely inappropriate,’ said Derek Wallis of
Cambridge Consultants, one of the project partners.
Caterpillar, Cambridge Consultants and the other partners —
Loughborough, City and Sussex Universities — are attempting to design an
engine that will approach HCCI operation even when it is changing between
stable loads. There are two main challenges, Wallis explained: ensuring the
Technology test-bed
THE AUTOMOTIVE sector has always
embraced electronics, and more advanced
technology is now finding its ways into cars.
Telematics — the integration of electronics,
and particularly telecommunications systems,
into automotive technology — is the latest
stage and, as it enters a new generation, the UK
is at the forefront of development.
A new facility, called innovITS-Advance, is
soon to take shape in Warwickshire, which
will be the proving-ground for systems that
will allow cars to communicate with
infrastructure built into the road network, and
Proving ground: the MIRA centre in Warwickshire
even with other cars. The centre is being built
at the headquarters of MIRA, the automotive
test and development house.
Its centrepiece, set to open next summer, is
a ‘test circuit’ comprising all the features of a
European city road network — traffic islands,
roundabouts, junctions controlled by traffic
lights — over an area of 120,000m 2 . Dotted
around and over these roads will be a series of
telecommunications networks, including 2G,
3G, GPRS, WiFi, roadside beacons and
monitoring systems based on inductive loops.
‘The first generation of telematics was very
vehicle-centric,’ said
innovITS chief executive
Phil Pettitt. ‘But increas-
ingly for the next
generation, people are
talking about interaction
between road and vehicle.’
This could include
sending information on
road, traffic and weather
conditions that could be
relayed to vehicles 20 miles
away, he said. ‘But you can’t
set up that sort of system to
the EnGIneeR 21 APRIL–4 MAY 2008 23
air/fuel mixture in the cylinders is homogenous; and controlling the combustion
so that it is not too fast. This would lead to ‘knocking’, which would destroy
the engine. ‘Keeping the mixture homogeneous is down to careful air intake
and injector mould design, and cylinder design,’ said Wallis. Fuel injector
nozzles, the geometry that induces mixing in the cylinder and the crown of the
piston all influence this.
Combustion control is also tricky. ‘With a diesel engine, you only have
secondary control. You can control things like the air charge temperature, how
much air goes in, how much fuel goes in and when, but you can’t control the
start of combustion,’ he said.
The project is due to finish in December, although Wallis believes full HCCI
is still some way off.
Diesel engine: radical new design in pipeline
test on the public highway.’ The innovITS
set-up will allow systems to be installed and
tested without need of planning inquiries or
road works. It will also allow companies to
UK AUTO SECTOR
gain valuable information in a realistic setting
with two-way traffic but in a controlled
environment, where experiments can be
repeated at different speeds, in different traffic
conditions and so on.
This could be crucial in testing systems
where the telematics help with safety, said
Pettitt. ‘You want to point vehicles at each
other in realistic ways at an intersection and
see whether the systems will intervene and
prevent a collision from occurring. You don’t
want to do that in a public arena, because
you’d have to cordon off roads.’
The project is attracting attention from car
makers and telecommunications companies,
said Pettitt. ‘The view is to attract people to do
research and development in this country. One
major European car manufacturer has told us
that if we weren’t doing this, they’d have to set
up something similar, so there’s definitely
going to be a demand for it. And with the
amount of R&D and development work that
already happens here, we’re very optimistic.’
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