Bosch says it has solved diesel NOx problem; as low as 13 mg NOx/km even under RDE; refining existing technologies
Bosch says that its engineers have refined existing diesel technolgoies to reduce emissions of nitrogen oxides (NOx) so significantly that they already comply with future limits. Even in RDE (real driving emissions) testing, emissions from vehicles equipped with the newly premiered Bosch diesel technology are not only significantly below current limits but also those scheduled to come into force from 2020 (Euro 6d).
Because the solution leverages existing technology, there is no need for additional components, which would drive up costs.
There’s a future for diesel. Today, we want to put a stop, once and for all, to the debate about the demise of diesel technology. Bosch is pushing the boundaries of what is technically feasible. Equipped with the latest Bosch technology, diesel vehicles will be classed as low-emission vehicles and yet remain affordable.—Bosch CEO Dr. Volkmar Denner
Since 2017, European legislation has required that new passenger car models tested according to an RDE-compliant mix of urban, extra-urban, and freeway cycles emit no more than 168 milligrams of NOx per kilometer. As of 2020, this limit will be cut to 120 mg. But even today, vehicles equipped with Bosch diesel technology can achieve as little as 13 milligrams of NOx in standard legally-compliant RDE cycles. That is approximately one-tenth of the prescribed limit that will apply after 2020.
Even when driving in particularly challenging urban conditions, where test parameters are well in excess of legal requirements, the average emissions of the Bosch test vehicles are as low as 40 milligrams per kilometer.
Bosch engineers have achieved this decisive breakthrough over the past few months. A combination of advanced fuel-injection technology, a newly developed air management system, and intelligent temperature management has made such low readings possible, Bosch says.
|Overview of temperature management measures for the exhaust system. From the Bosch paper presented at the Vienna Motor Symposium this year. Click to enlarge.|
To date, two factors have hindered the reduction of real-world NOx emissions in diesel vehicles, according to Bosch. The first of these is driving style.
The technological solution developed by Bosch is a highly responsive air-flow management system for the engine. A dynamic driving style demands an equally dynamic recirculation of exhaust gases. This can be achieved with the use of a RDE-optimized turbocharger that reacts more quickly than conventional turbochargers.
With a combination of high- and low-pressure exhaust-gas recirculation, the air-flow management system becomes even more flexible. This means drivers can drive off at speed without a spike in emissions.
Equally important is the influence of temperature. To ensure optimum NOx conversion, the exhaust gases must be hotter than 200 degrees Celsius. In urban driving, vehicles frequently fail to reach this temperature. Bosch has therefore opted for a sophisticated thermal management system for the diesel engine.
This actively regulates the exhaust-gas temperature, thereby ensuring that the exhaust system stays hot enough to function within a stable temperature range and that emissions remain at a low level.
NOx emissions can now remain below the legally permitted level in all driving situations, irrespective of whether the vehicle is driven dynamically or slowly, in freezing conditions or in summer temperatures, on the freeway or in congested city traffic.
Bosch’s new diesel system is based on components that are already available in the market. It is available to customers effective immediately and can be incorporated into production projects.
At a press event in Stuttgart Bosch had dozens of journalists, from both Germany and abroad, drive test vehicles equipped with mobile measuring equipment in heavy city traffic, under especially challenging conditions. The results, shown in the chart below, show the performance of the Bosch technology against current and 2020 regulations.
AI can further boost performance. Even with the reported technological advance, the diesel engine has not yet reached its full development potential, Bosch said. Bosch now aims to use artificial intelligence to build on these latest advances.
This will mark another step toward a major landmark: the development of a combustion engine that—with the exception of CO2—has virtually no impact on the ambient air.
We firmly believe that the diesel engine will continue to play an important role in the options for future mobility. Until electromobility breaks through to the mass market, we will still need these highly efficient combustion engines.—Volkmar Denner
Denner’s target for Bosch engineers is the development of a new generation of diesel and gasoline engines that produce no significant particulate or NOx emissions. Even at Stuttgart’s Neckartor, a notorious pollution black spot, he wants future combustion engines to be responsible for no more than one microgram of NOx per cubic meter of ambient air—the equivalent of one-fortieth, or 2.5%, of today’s limit of 40 micrograms per cubic meter.
Bosch calls for renewed focus on CO2 and well-to-wheels evaluations. Denner also called for a renewed focus on CO2 emissions. Denner said that consumption tests should no longer be conducted in the lab but rather under real driving conditions. This would create a system comparable to the one used for measuring emissions.
Moreover, he added, any assessment of CO2 emissions should extend significantly further than the fuel tank or the battery—a full well-to-wheels lifecycle approach.
We need a transparent assessment of the overall CO2 emissions produced by road traffic, including not only the emissions of the vehicles themselves but also the emissions caused by the production of the fuel or electricity used to power them.—Volkmar Denner
He added that a more inclusive CO2 footprint would provide drivers of electric vehicles with a more realistic picture of the impact of this form of mobility on the climate. At the same time, the use of non-fossil fuels could further improve the CO2 footprint of combustion engines.