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Mixed-Mode Diesel Hcci/Di With External Mixture Preparation
Technical Paper
2004-05-0446
Sector:
Language:
English
Abstract
Diesel HCCI (Homogenous Charge Compression Ignition) is a
combustion technology showing great promise for the reduction of
oxides of nitrogen and particulate matter from diesel engines. Our
proposed implementation of HCCI is a mixed-mode concept, which
relies on a direct-injection system that is optimized exclusively
for direct injection. To accomplish HCCI, an external fuel atomizer
is used. By decoupling the direct injection from the HCCI mixture
formation, the injector and combustion chamber can be optimized
much more aggressively for DI (Direct-Injection) operation. This
system allows efficient high-load operation in DI mode without
compromising performance, low- to mid-load operation in HCCI mode,
and a region in between where both systems operate together.
External mixture formation for diesel fuel has largely been
abandoned in favor of internal mixture formation using the DI
system. This is partially due to previous attempts at diesel HCCI
requiring intake air heating in the range to 100°C to 200°C and
low compression ratio engines. Using a highly effective atomization
device, diesel HCCI operation with external mixture formation has
been demonstrated at a compression ratio of 18:1, intake
temperatures in the range of 15°C to 60°C, and up to a maximum
load of 4.7 bar IMEP. With this technique, the traditional problems
of external diesel mixture formation, such as high intake heating,
low compression ratio, wall wetting, and soot formation, are
largely avoided.
This HCCI mode operation has been demonstrated on a
single-cylinder engine (1/4 of a recent production 2.2L engine) in
collaboration between Ohio State University and the FKFS (Research
Institute of Automotive Engineering and Vehicle Engines Stuttgart).
The concept has demonstrated extremely low levels of nitrogen
oxides (< 4 ppm) and smoke (< 0.03 FSN) over a large range of
operating conditions. The combustion technique has shown good
insensitivity over a wide range of operating conditions such as
engine speed, load, boost pressure, intake temperature, and EGR
rate. Experimental results for these parameter sweeps as well as
for mixed-mixed mode combustion are presented and discussed.
Authors
- Simon Haas - Research Institute of Automotive Engineering and Vehicle Eng
- Michael Bargende - Research Institute of Automotive Engineering and Vehicle Eng
- Hans-Jürgen Berner - Research Institute of Automotive Engineering and Vehicle Eng
- Shawn Midlam-Mohler - The Ohio State University Center for Automotive Research
- Yann Guezennec - The Ohio State University Center for Automotive Research
- Giorgio Rizzoni - The Ohio State University Center for Automotive Research