TECHNICAL PAPERS: Internal Combustion Engines

Study of Multimode Combustion System With Gasoline Direct Injection

[+] Author and Article Information
Zhi Wang, Jian-Xin Wang, Shi-Jin Shuai, Yan-Jun Wang, Guo-Hong Tian, Xin-Liang An

State Key Laboratory of Automotive Safety and Energy,  Tsinghua University, Beijing 100084, China

J. Eng. Gas Turbines Power 129(4), 1079-1087 (Oct 02, 2006) (9 pages) doi:10.1115/1.2718221 History: Received April 01, 2006; Revised October 02, 2006

In this paper, a multimode combustion system was developed in a gasoline direct injection engine. A two-stage fuel-injection strategy, including flexible injection timings and flexible fuel quantity, is adopted as a main means to form desired mixture in the cylinder. The combustion system can realize five combustion modes. The homogeneous charge spark ignition (HCSI) mode was used at high load to achieve high-power output density; stratified charge spark ignition (SCSI) was adopted at intermediate load to get optimum fuel economy; stratified charge compression ignition (SCCI) was introduced at transient operation between SI and CI mode. Homogeneous charge compression ignition (HCCI) was utilized at part load to obtain ultralow emissions. Reformed charge compression ignition (RCCI) was imposed at low load to extend the HCCI operation range. In SI mode, the stratified concentration is formed by introducing a second fuel injection in the compression stroke. This kind of stratified mixture has a faster heat release than the homogeneous mixture and is primarily optimized to reduce the fuel consumption. In CI mode, the cam phase configurations are switched from positive valve overlap to negative valve overlap (NVO). The test results reveal that the CI combustion is featured with a high gradient pressure after ignition and has advantages in high thermal efficiency and low NOx emissions over SI combustion at part load.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Combustion modes and corresponding operation regions of gasoline engine

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Figure 2

Injection strategies of GDI engine at different combustion mode: (a) SI mode and (b) CI mode

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Figure 3

Two-stage variable valve timing mechanism: (a) SOHC with CPS, (b) multiple cam profiles with synchro switch, and (c) measured cylinder pressure traces in continuous engine cycles at motoring case

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Figure 4

Transient SI-HCCI switch process

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Figure 5

Effects of gb2∕gb1 on combustion and emission performance at same total fuel mass per cycle

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Figure 6

Effects of gb2∕gb1 on indicated diagram and the corresponding rate of heat release at same total fuel mass per cycle

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Figure 7

Effect of injection timing on combustion and emission characteristics at CI combustion mode: (a) Emissions and (b) indicator diagram and ROHR

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Figure 8

Typical indicator diagrams and the corresponding ROHRs at different combustion modes

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Figure 9

HCCI operation region of three NVO phases

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Figure 10

Optimized injection strategies and corresponding combustion modes

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Figure 11

Fuel consumption (ISFC, g∕kW h) of gasoline DI HCCI engine

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Figure 12

Emissions of gasoline DI HCCI engine: (a) NOx emission (×10−6), (b) THC emission (×10−6), and (c) CO Emission (%)




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