Exhaust gas recirculation (EGR) is a proven method for emissions reduction in diesel engines; the higher the quantity of exhaust gas in combustion air, the more oxides of nitrogen emissions are reduced.
To increase levels of EGR, IAV has developed a forced induction concept, where a Lysholm twin-screw compressor with a rotary-slide control is placed between the exhaust-gas turbocharger and the engine intake. The compressor draws cooled exhaust gas from downstream of the oxidation catalyst and mixes it in a controlled manner with the fresh charge air to provide the optimum blend for best emissions and performance.
IAV's system uses an engine-driven but electrically-assisted compressor to keep the EGR ratio at an optimum level even at changing engine speeds. The assistance of an electric motor/generator comes through a planetary gear element. About two thirds of the compressor power is produced by the engine and one third by the electric motor/generator. The compressor always runs at least at engine speed, but can be boosted when required (for example, when overtaking) through the planetary by the electric motor. The generator function may be used to charge the battery system when its positive motor-assist is not required.
The EGR ratio is controlled actively by two rotary valves which define the valve timing for the fresh air and the exhaust gas inlet. The mixing pressures are kept in balanced control, even under load changes, which gives a major advantage when compared to a plain exhaust gas feeder pump.
In contrast to other charging devices, the twin screws are insensitive to hydraulic pounding. Also, when the cooled EGR falls below dew point, the compressor may be used to clean the system with condensation. However, care must be taken in the system layout to ensure that condensation will not puddle.
The studies show that the IAV High-EGR concept is successful in reducing the emissions of a diesel engine. The flexibility in the EGR mixing and the cylinder filling, held independent of each other, offer new possibilities in engine calibration for future developments. The next stage in development will be validating the engine dyno concept in an on-road vehicle.
Employing over 4,500 members of staff across the globe, IAV is one of the leading providers of engineering services to the automotive industry. The company has been developing innovative concepts and technologies for future vehicle generations for over 25 years. Core competencies include production-ready solutions in all fields of electronics, powertrain and vehicle development. Clients include all of the world's premier automobile manufacturers and suppliers. In addition to development centers in Berlin, Gifhorn, Chemnitz and Northville, MI, IAV also operates from other locations in Europe, Asia and South America.