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Achieving Very Low PN Emissions with an Advanced Multi-Hole Injector Functionality and Adapted Spray Targeting Under High Fuel Pressure Conditions
Abstract:
In the near future, emissions legislation will become more and more restrictive for direct injection SI engines by adopting a stringent limitation of particulate number emissions in late 2017. In order to cope with the combustion system related challenges coming along with the introduction of this new standard, Hitachi Automotive Systems Ltd., Hitachi Europe GmbH and IAV GmbH work collaboratively on demonstrating technology that allows to satisfy EU6c emissions limitations by application of Hitachi components dedicated to high pressure injection (1).
This paper sets out to describe both the capabilities of a new high pressure fuel system improving droplet atomization and consequently mixture homogeneity as well as the process of utilizing the technology during the development of a demonstrator vehicle called DemoCar. The Hitachi system consists of a fuel pump and injectors operating under a fuel pressure of 30 MPa.
Revised spray patterns have been developed following an IAV process using optical spray vessel investigations as well as CFD simulation for a specific engine (boosted engine with 1.4L engine displacement and direct injection). For the system evaluation on the engine test-bench and inside the vehicle on the chassis roller dyno, Hitachi Automotive Systems, Ltd. manufactured the new spray patterns accordingly.
The chosen test engine has been equipped with the Hitachi components and has been optimized on the engine test-bench in steady state conditions. Subsequently, the high pressure injection system has been installed onto a DemoCar in order to also improve the calibration in transient operation on the chassis roller dyno. Since injector properties are different from the reference injectors, the injection strategy has been modified and re-calibrated at catalyst heating, warm-up operation and hot condition operation.
The final calibration with 30 MPa maximal injection pressure enabled a reduction by 60% of particulate number over NEDC compared to the reference without a strong penalty on fuel consumption.