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 the nitrogen oxide emissions are reduced.
IAV Automotive Engineering Inc. adds a little something to this common formula with its active High-EGR concept. To increase circulation, 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 beyond the oxidation catalyst and mixes it in a controlled manner with the fresh charged air to provide what it says is the optimum blend for best emissions and performance.
IAV will demonstrate this technology, and others, at the SAE 2011 World Congress slated for April 12-14 in Detroit.
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 with the assistance of the electric motor drive through a planetary gear element. Two-thirds of the compressor power is produced by the engine, one-third by electric motor. The compressor always runs at least at engine speed, but can be boosted when required through the planetary by the electric motor, which can also be used to charge the battery system when its positive assist is not required.
The EGR ratio is controlled actively by two rotary valves that 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, according to the company.
In contrast to other charging devices, twin screws are insensitive to hydraulic pounding. In addition, the cleansing condensation can be used when the cooled EGR falls below dew point. IAV notes, however, that care must be taken in the system layout to ensure that condensation does not puddle.
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 offers new possibilities in engine calibration. The next stage in development will be validating the test-bench concept in an on-road vehicle.
Also at the SAE World Congress, IAV is introducing a computerized tool set for the selection of automatic transmission gearing arrangements. The program systematically searches through all power-flow permutations for a specific application and then selects the architecture with the highest mechanical efficiency and the lowest number of loaded components.
Searches can be performed for both conventional planetary and dual-clutch lay shaft structures.
Future transmission wants include lower weight and cost, hybridization, a small package, and good shift quality. The manual search for transmission architectures cannot support these stringent and complex requirements, according to the company. Currently, transmission arrangements are generated manually and then compared to design targets. Such a trial-and-error approach can be time-consuming, especially for transmissions of more than six speeds. There may be over a trillion possible alternative layouts for some transmissions, IAV says.
The IAV transmission synthesis program involves three main phases: first, the application parameters are established; second, all possible transmission variants are generated for the application; and third, selection and ranking criteria are used to narrow the set of transmission concepts down to candidate structures with favorable properties.
A resultant example of the synthesis approach is a new rear-wheel-drive, 11-speed dual clutch transmission for commercial vehicles. The forward shifts all have the same step sizes. Two reverse gears are also available. The compact design consists of only two clutches, seven spur gear sets, four double synchronizers, and two single synchronizers.