Search Results

A urea SCR deNOx system for heavy-duty diesel engines was developed comprising a SCR catalytic converter combined with a low sulfate formation oxidation catalyst. Urea is injected upstream the SCR catalyst system by means of an open-loop controlled injection system. Test bed investigations with the urea deNOx system applied to a 315 kW EURO 2 baseline heavy-duty diesel engine demonstrated a NOx emission reduction potential down to a level of less than 3 g/kWh. Heavy-duty diesel engines equipped with such a deNOx converter are able to comply with the expected EURO 4 NOx emission limits, independent from the ultimately effective test cycle. The particulate emission level of the EURO 2 engine was found not to be influenced by the SCR catalyst. The combination of SCR and oxidation catalyst results in a particulate increase of up to 25%, depending on the utilized test cycle.

Tests are carried out to assess the potential of using SCR DeNOx catalysis, for achieving ultra-low NOx emission levels with heavy-duty diesel engines. A prototype DeNOx catalyst system has been developed which consists of a moderately sized SCR catalyst, upstream of which urea is injected through a heat-shielded nozzle. Downstream of the SCR catalyst a low sulphate oxidation catalyst is used to ensure any ammonia slippage from the SCR stage is oxidized. The system was tested on a standard 2-valve EURO 2 engine over several steady-state and transient test cycles currently under discussion for European use. Over these test cycles NOx emission values of about 2 to 2.5 g/kWh are accomplished, which are sufficient to fulfill future European heavy-duty NOx emissions legislation to be expected around the year 2005.

In anticipation of ever tighter noise emission limits for motor vehicles it is necessary to reduce the noise emitted by diesel engines. Within the program “Road Noise Abatement” a new heavy-duty air-cooled DEUTZ diesel engine was developed. This is a 6-cylinder, in-line, turbocharged and intercooled engine, with a power output in excess of 200 kW. The development program, conducted by Kloeckner-Humboldt-Deutz AG (KHD), was partly funded by the Ministry of Research and Technology of the Federal Republic of Germany. Objective of the program was to demonstrate compliance with the 1990 EC drive-by acceleration noise limits without the need for special noise abatement measures on the vehicle. While meeting these noise requirements, the diesel engine had also to comply with the future European emission standards (50% below ECE R 49) and deliver the excellent performance and fuel economy characteristics typical of this type of engines.

Kloeckner-Humboldt-Deutz AG (KHD) has developed a glow plug assisted heavy-duty methanol engine based on the standard production diesel engine F8L 413F. This type of engine is an air-cooled, 8-cylinder, V-type engine with a high swirl direct injection combustion system. The paper presents the development of a glow plug-based hot surface ignition system and the combustion system optimization work done to obtain high engine efficiency and low emission levels. Furthermore, it deals with the development of methanol specific engine components for the purpose of achieving a high reliability and long life. In the whole operational range the methanol engine exhibits an energy consumption nearly equal to its diesel counterpart, together with an excellent emission quality, capable of meeting the 1994 EPA emission standards for heavy-duty engines.

Investigations on the suitability of various alcohol fuels as alternatives to conventional diesel fuel were carried out on a passenger car swirl-chamber diesel engine. The test results with a methanol and an ethanol diesel fuel blend show that without alteration of the engine adjustment a good performance behaviour is obtained. In addition to a reduced soot emission and a considerably lower particulate emission the thermal efficiency mainly in the upper load range is higher than with pure diesel operation. The increased HC and CO emissions occuring at low loads can be avoided and a further improvement in energy consumption can be realized by adapting the injection timing for alcohol blend operation. A complete substitution of the diesel fuel with a methanol-ignition improver mixture necessitates an adapted and alcoho-resistent fuel injection system.