The Ricardo research project is timely when viewed against the backdrop of concern over future diesel emissions and recent events at Volkswagen AG.
Despite continuing and significant reductions
in the legislated light-duty diesel vehicle NOx emissions under the European
Euro 1 through 5 regulations of recent years, it has been demonstrated by many
researchers that real-world NOx emissions appear not to have been reduced as
significantly.
This is one of the primary drivers for the
proposed introduction of RDE in European Euro 6c legislation as early as
2017.
The objective of this proposed regulation is
that future vehicles certified to a given type approval threshold for NOx
output will, subject an incremental Conformity Factor to be defined in the
regulation, not exceed this level in normal on-road driving conditions.
A core aspect of the introduction of RDE
testing is on-road vehicle testing using a Portable Emissions Measurement
System (PEMS) in combination with post-processing of the results to include the
evaluation of real driving NOx and CO2 emissions.
While full and final details of RDE
regulations are yet to be fully defined, it is understood that reduction of NOx
emissions will be required across a wider spectrum of engine operating
conditions than those of the Euro 5 rules.
Ricardo believes it is essential to establish
a development process that is capable of providing cost-effective yet RDE
compliant powertrain and after-treatment solutions.
In planning its RDE research, Ricardo aimed to
couple its practical experience of PEMS testing with its vehicle simulation
capabilities in order to enable assessment of different vehicle and after-treatment
systems over a compliant RDE cycle.
This approach enabled a detailed review of the
NOx control performance of the engine and after-treatment systems of each
different vehicle configuration, and allowed an evaluation of the Conformity
Factor.
This was generated by analysis using the
proposed EMROAD and CLEAR data reduction algorithms to assess the PEMS test
results.
Finally the project aimed to study the key
contributing factors for RDE results in order to further refine the future
development process.
Ricardo says its Shoreham Technical Centre
provides an “ideal location” for the type of mixed driving that is considered
likely to form the basis of RDE regulations, including rural, urban, and fast
highway roads, and a range of gradients.
As such, Ricardo was able to define an RDE route
comprising all of the likely requirements within a 20km radius of the company’s
technical centre.
Each engine-vehicle configuration was
simulated over the NEDC and WLTC cycles in order to provide input to the data
reduction tools, and the working assumption for legislated NOx limit used was
80 mg/km.
Two vehicles were used as the basis of the
study; a typical C-segment hatchback and a mid-sized European SUV. Within
these two classes, a range of after-treatment technologies was assessed for
each vehicle in order to assess its likely Conformity Factor under projected
RDE requirements.
Laboratory based testing of the research
vehicles was carried out in the Ricardo Vehicle Emissions Research Centre
(VERC), opened at the Shoreham Technical Centre in July. This state-of-the-art
facility is amongst the most advanced vehicle emissions testing laboratories
anywhere in the world. Already in high demand for today’s testing requirements,
the facility is also future-proofed against the needs of all projected future
regulatory requirements such as RDE.
Work continues to evaluate a wider range of
real world driving conditions and to select the most cost effective technology
as well as considering further vehicle classes and emissions legislation environments
(e.g. US EPA LEVIII).
As the final regulatory details and deadlines
are finalized in the coming months therefore, Ricardo is thus ready to assist
its clients in developing fully compliant diesel vehicles from the moment that
RDE is introduced.
No doubt other R&D facilities in the UK
will also be showing great interest in RDE against the Volkswagen backdrop,
including no doubt the Millbrook Proving Ground in Bedfordshire which has its
own on-site high-speed, urban and city driving courses as well as off-road
facilities, as well as MIRA in Nuneaton.
1 comment:
In the light of the ongoing VW emissions saga, the measurement accuracy and repeatability of Ricardo's portable kit need to match those of Euro 6 et seq laboratory standard certification test equipment, if the results are going to be credible. That's a tall order, given the variations in ambient conditions at the roadside or even on a local roadworthiness test station rolling road.
In any case the accuracy of NOx sensor readings has always been questionable, though advances have certainly been made since the sensors first became available from NGK in Japan.
Intriguingly, NOx appears to remain the focus of attention on diesel emissions, to the evident exclusion of particulate matter (PM). But it should be recognised that engine management reprogramming to cut NOx by either increasing EGR rates or retarding injection timing will push up PM levels. If legislated PM limits are not to be breached, then upgraded DPF (diesel particulate filter) specifications will be needed, further jeopardising fuel consumption.
Post a Comment