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Dielectric barrier discharges offer the advantage to excite molecules to reaction processes on a low temperature level in an O2 containing exhaust gas of gasoline or diesel engines. With the aim of a flexible coaxial reactor and a compact and efficient generator the influence of geometric and electric parameters on the reduction of exhaust gas components was determined. Geometric parameters studied were gap width, length, contour of the reactor. Electric parameters were: voltage curve, voltage height, frequency and electric power. Using the advantage of low temperature reactions it was possible to reduce the HC emission of a gasoline engine by about 35% within an electric power of 1000 W.

In view of limited crude oil resources, alternative fuels for internal combustion engines are currently being intensively researched. Synthetic fuels from natural gas offer a promising interim option before the development of CO2-neutral fuels. Up to a certain degree, these fuels can be tailored to the demands of modern engines, thus allowing a concurrent optimization of both the engine and the fuel. This paper summarizes investigations of a Gas-To-Liquid (GTL) diesel fuel in a modern, post-EURO 4 compliant diesel engine. The focus of the investigations was on power output, emissions performance and fuel economy, as well as acoustic performance, in comparison to a commercial EU diesel fuel. The engine investigations were accompanied by injection laboratory studies in order to assist in the performance analyses.

Fuel additives can contribute to maintaining the performance of diesel engines in a variety of ways. This holds true for current and future engine technology. Fouling of indirect injection engines (IDI) has been studied at length. Fouling of direct injection engines (Dl) is less known and less well understood. Problems associated with Dl fouling and a proposed mechanism for it are discussed. Additive effectiveness in preventing injector fouling is confirmed. Injector hole corrosion/erosion, as experienced in the Cummins N14 engine, can be avoided by the appropriate additive chemistry. Particulate traps can also benefit from ashless additive technology aimed at increasing the time between regeneration steps, hence improving effective trap life.

Passenger cars with diesel engines have better fuel economy than cars with gasoline engines. Also diesel engines typically have lower HC and CO emissions than all but the very best, state-of-the-art gasoline engines. On the other hand, diesel NOx and particulate emissions are higher, but recent developments have significantly reduced diesel particulate emissions. While the regulated emissions from both engines are well known, there are relatively few data on the non-regulated emissions for modern diesel engines.

A comparison of two different types of NOx reducing catalysts will be worked out. The potential of two De-NOx catalysts using engine out hydrocarbon emissions for NOx conversion will be shown by variation of different engine parameters. An analysis of the hydrocarbon species upstream and downstream catalyst will demonstrate, which components are responsible for the NOx reduction in the exhaust gas of a lean burn engine. By variation of different parameters during adsorbtion and regeneration phases of the adsorber catalyst the efficiency in NOx reduction will be optimized. An assessment of the suitability for lean burn engines will consider the emission reduction efficiency as well as the influence on engine fuel consumption.

An improved plasma reactor has been designed, built and evaluated. It is characterized by a reduced power per area ratio, relative to previous designs, and includes several improvements to run the whole system safely in a car. The new reactor design includes a concentric inner high voltage electrode, a grounded outer electrode, a shielded high-voltage and high temperature resistant electrical connection. A generator controller has been developed for better control of operating conditions as required during the engine cold start phase. The new generator/reactor system was installed in the exhaust pipe of a gasoline direct injection engine. HC emissions could be reduced up to 30 % in the first 40 seconds of a cold start test. In addition to HC treatment the dielectric barrier discharge has also been investigated as a method for regenerating a diesel particulate trap.

Dielectric barrier discharge (DBD) offers the advantage to excite and dissociate molecules in the exhaust gas stream. Those dissociated and excited species are oxidizing or reducing harmful exhaust gas components. The advantage of a plasma chemical system in comparison to a catalytic measure for exhaust gas treatment is the instantaneous activity at ambient temperature from the starting of the engine. The investigations reviewed in this paper are dealing with the plasma chemical oxidation of hydrocarbons in the exhaust gas stream during cold start conditions. The article concerns the design and development of a plasma-system in order to decrease the hydrocarbon emissions from engine start till catalyst light off. Vehicle results in the New European Driving Cycle show a hydrocarbon conversion of more than 42% in the first 11 seconds from engine start. In this period nearly all types of hydrocarbon were reduced.