Ford of Europe's Rudi Kunze has been a driving force behind Ford's move from an also-ran to a diesel powerhouse in Europe.
Ford's strengthened lineup of diesels comes from its diesel engine joint venture with PSA/Peugeot-Citroen.
Kunze, Ford of Europe's chief technical officer, spoke with Automotive News Europe reporter Bradford Wernle about particulate filters and other diesel issues at Ford's European Research Center in Aachen, Germany.
Can diesel engines burn cleanly enough without particulate filters?
When you look into the future, it's really a question of whether you should aftertreat or reduce emissions at the source.
With our PSA/Peugeot-Citroen partners, we're looking at the next-generation injection systems and new, modern combustion methods.
What about NOx filters?
Whenever you put something on the exhaust such as a NOx filter, you're throttling the exhaust. That means the engine consumes more fuel.
We, and a lot of our competitors, are trying to reduce emissions and improve fuel economy at the source. We're looking into new ways of burning the fuel. We call them homogeneous combustion systems.
How does homogeneous combustion work?
By increasing injection pressure and spraying the fuel through multiple holes into a wider area of the combustion chamber, you can have a smoother injection process. You need to have the spray as homogeneous as possible. That will take a few years to work out.
But if it does work, you'll have more applications of diesel engines that will be cleaner burning, use less fuel and emit fewer particulates and less NOx.
That's only possible if you address it at the source.
Are there any problems with homogeneous combustion?
With smaller injector hole sizes, the risk of coking increases. One of the biggest challenges in the future is getting better combustion, which requires finer sprays and better controllability of the spray events. The finer you get the spray and the higher pressures you use, the more material challenges you get, especially with the injectors. The most critical point is the spray holes. Suppliers will share their part of the challenge.
How long before we see homogeneous combustion engines?
Within the decade definitely. There are significant problems with controlling this kind of combustion. You can't use this combustion throughout driving range. It's a significant challenge to engine management systems. As you get to much, much smaller holes and higher tolerances and pressures, reliability really becomes an issue.
What are the disadvantages of aftertreatment with filters?
If you do aftertreatment, it's always associated with a fuel economy penalty. That's why we have these intense discussions with European and national governments. We're believe that equipping those systems with filters and lowering CO2 at the same time is incompatible.
What impact will Euro 5 have?
We don't know what aftertreatment costs will be at that point in time. We can imagine a scenario where you take particulate filter and NOx aftertreatment and combine it into one can.
That would be a significant cost-reduction opportunity, if you could have one can with one control system instead of two. At the moment you look at particulate and NOx separately. That gives you cost benefits, installation benefits and reduced complexity.
You're also working on diesels that might be used someday in North America. What are the different issues there?
In the US, the emission levels that will be required are very demanding, especially for NOx. Even if you optimize combustion, it's a real challenge to get away without NOx aftertreatment. You can use a de-NOx trap, an additional device on the exhaust. Or you can use SCR [selective catalytic reduction], which uses urea in a catalyst that very effectively reduces NOx. It's a technology known from truck applications.
What role do oil companies play in emission reduction?
Oil companies are researching fuel specifications that help lower particulate and NOx generation. You don't have unified low-sulphur fuel in the US, which is a challenge. That's where ideas come up such as designer fuel. If you could design a diesel fuel, you could have the optimum combination of carbon and hydrogen and you could optimize for clean burning.
What are the advantages of diesels?
The sales point on diesels is not just fuel economy. They've really becoming something that's fun to drive. They have high refinement and low-end torque. The V-6 diesel we designed for Jaguar here in Aachen is smooth like silk and powerful like a rocket.
How much of your research and development work at Aachen is devoted to diesel?
About 50 percent of my resources goes to diesel. Of the diesel work, maybe 80 percent of our diesel efforts are related to fuel economy and emissions.