Pictures of the Future Spring 2005
Elements of Life – Minimizing Dangerous Substances
Fighting Soot
New diesel engine technologies save fuel and deliver good performance while reducing nitrogen oxides. They also filter out those soot particulates that are most dangerous to health.
The PM Filter Catalyst removes precisely those particulates from diesel exhaust that are most dangerous. Specially shaped micro-channels guide the tiny soot particles to a metallic fleece, where they are burned off
Four out of ten new cars in Germany have diesel engines—and the number is increasing. The reason for this popularity is that thanks to their higher efficiency, diesel motors use less fuel than gasoline-powered engines. But diesel engines also have a few shortcomings. For instance, their exhaust contains particulate matter suspected of causing cancer and relatively high nitrogen oxide (NOx) emissions. That’s why strict emissions limits went into effect in the European Union as of 2005. The new Euro 4 (EU4) emissions standard requires that diesel vehicles emit 50 % fewer particulates and NOx than allowed under the current EU3 standard. Heavy commercial vehicles must cut their NOx emissions by 30 % and their particulate emissions by 80 %. And in 2010, with EU5, the limits will be tightened even further. That presents manufacturers with a dilemma. Ideally, diesel engines operate at a high combustion temperature to achieve high performance and save on fuel at the same time. But high temperatures increase nitrogen oxide levels. If the temperature is lowered, however, fuel consumption and particulate emissions increase.
Cutting the Smallest Particles. Emitec, a joint venture of Siemens and British auto equipment supplier GKN, has developed a very efficient technology that simultaneously combats both types of pollutants and is suitable for trucks and passenger cars alike. Its PM (particulate matter) Filter Catalyst consists of a platinum oxidation catalyst and a particle filter. In a first stage, the catalyst converts unburned hydrocarbons and carbon monoxide into carbon dioxide. At the same time, it oxidizes nitrogen oxide (NO) into nitrogen dioxide (NO2), which is playing a decisive role in removing soot particles in the second stage. The soot particles are removed from the exhaust gas by means of specially shaped micro-channels and directed to a metallic fleece, where the particles collect in the fleece’s tiny pores. Here, beginning at about 200 °C, they are continuously burned off with the oxygen from the NO2, which is converted back to NO.
Light without Mercury
Many everyday products contain pollutants. Fluorescent lamps are a case in point. They contain small quantities of poisonous mercury that generates UV radiation, which is in turn absorbed by luminescent substances on the inside of the bulb and converted to light. When the lamp burns out, it has to be disposed of as hazardous waste. But there are alternatives. Researchers at Siemens subsidiary Osram have developed a fluorescent lamp (Planon) that is as flat as a tile and contains xenon, a non-toxic and thus environmentally friendly inert gas. The lamp generates illumination by means of a "pulsed dielectrically inhibited discharge." The xenon then emits energetic UV radiation and thereby excites the phosphor, which in turn gives off visible light.
Nine hundred Planon tiles act as a colossal, 3000-m² display on the facade of this building
Because Planon contains no mercury that must first vaporize, which takes several seconds, it develops its full luminosity immediately and without flickering. Light is evenly distributed across its entire surface. When it comes to service life, Planon is unbeatable. It shines for up to 100,000 hours. "It works well as backlighting for LCD industrial displays and large-screen LCD TVs," says Dr. Norbert Haas, head of Planon Marketing and Sales at the Osram plant in Herbrechtingen, Germany. In the pilot production system there, technologies are being developed for mass production, and the first prototypes of the second Planon generation are already being produced. The members of Planon’s "extended family" also include Linex, which operates on the same principle. This rod-shaped lamp runs on high-frequency, pulsed DC voltage. And as a result, it switches on and off with exceptional speed. It supplies bright, flicker-free light within a few milliseconds. That makes it ideal for use in scanners and copiers, for example. In addition, its spectrum can be shifted into the UV-A range with special phosphors, thus enabling it to neutralize bacteria and other germs to improve the air quality inside a car, for instance. Osram researchers have already developed an initial prototype for this application, and its market launch is planned for the middle of next year. "Now we’re working on further optimizing the luminous efficiency of both lamps so that they’ll also be suitable for general lighting uses," explains Haas.
"The PM Filter Catalyst removes about 80 % of particles 20 to 100 nm in size—in short, those that are dangerous to the human respiratory system. Overall particle mass is reduced by 60 %," says Emitec Managing Director Wolfgang Maus. And there’s another benefit. The PM Filter Catalyst is maintenance-free and hardly affects fuel consumption. Among its first users is truck manufacturer MAN; its latest generation of engines has been equipped with the filter since 2004. And the filter will be adopted in more production vehicles by the end of 2005, Emitec predicts. In fact, Emitec experts are convinced this technology will also be used for retrofits on a large scale. "But a package of measures still must be implemented to meet the EU5 standard in the longer term," says Maus. These measures include more precise and effective engine electronics, sensor systems and fuel injection—and exhaust gas recirculation, in which some exhaust is routed back, cooled and added to the intake air, decreasing the combustion temperature and thus NOx emissions.
Combination Engines. The future, Maus believes, belongs to a new concept. "Homogeneous Charged Combustion Ignition" (HCCI) combines the properties of internal combustion and diesel engines. In contrast to direct-injecting diesel and internal combustion engines, which distribute and burn fuel unevenly, the HCCI combustion process is designed to be uniform throughout the entire cylinder. The air-fuel mixture is so lean—little fuel, lots of cooling air—that a spark plug is needed to ignite the mixture after it’s been compressed. This way, combustion occurs in a homogeneous manner. The advantage of this process is that hardly any particulates or nitrogen oxides are produced. The drawback is an increase in hydrocarbon and carbon monoxide emissions. However, these can be reduced by using an oxidation catalyst. Obviously, Emitec engineers have their work cut out for them before an HCCI engine can reach the market.
Evdoxia Tsakiridou