New Hcci/Cai Combustion Process Development: Methodology for Determination

N. Jeuland,P. Duret,X. Montagne

doi:10.2516/ogst:2004041

Abstract

To pass the simultaneous emission requirements for near zero pollutant and low CO2 levels, which are the challenges for future powertrains, many research studies are currently carried out over the world on new engine combustion processes, such as controlled auto-ignition (CAITM) for gasoline engines and homogeneous charge compression ignition (HCCI) for Diesel engines. These new processes have the potential to reduce, by a factor of 10 to 100, NOx (Nitric Oxide emissions) and particulate (PM) emissions in comparison with a typical gasoline or diesel engine. The main issue in the development of such combustion modes remains the limited range of engine speed and load that enable correct engine running, with acceptable levels of NOx and noise emissions. One of the promising ways to increase the CAI combustion range lies in the research of more adapted fuels, optimized to enhance combustion initiation by modifying and controlling their auto-ignition characteristics and/or their physical and chemical properties. A new procedure is set-up to select fuels, which allows a better characterization of the fuel impact on engine running in CAI, for various conditions of speed and load. The use of this methodology with a wide range of fuels, formulated according to their auto-ignition characteristics, volatility and chemical composition, underlines the complexity of the action of fuel and points out the most influent fuel characteristics for a wide range of running conditions.

Highlights

Fuels and engines used in road transportation have to face two main challenges in a highly competitive economy: – To reduce pollutant emission levels to values such that air quality in the cities complies with world health organization standards. – To reduce the emissions of carbon dioxide (CO2), regarded as the major greenhouse gas (GHG) contributing to global warming and climate changes
Fuel volatility is positively correlated with initial boiling point and the CAI range for zones 1 and 4, which means that the optimal fuel at low load condition appears to be a heavy fuel
The IFP-developed CAITM combustion system has been applied to a conventional gasoline automotive 4-stroke engine

Summary

Introduction

Fuels and engines used in road transportation have to face two main challenges in a highly competitive economy: – To reduce pollutant emission levels to values such that air quality in the cities complies with world health organization standards. – To reduce the emissions of carbon dioxide (CO2), regarded as the major greenhouse gas (GHG) contributing to global warming and climate changes. – Direct fuel injection (DI) technology could be adopted, with stratified charge and lean burn combustion systems over a limited operating range This lowers fuel consumption through reduced pumping and reduced heat transfer losses, but a major challenge is to reach ultra-low pollutant emission levels because of the need for a sophisticated and fuel sensitive DeNOx after-treatment device. – Another approach would be to keep the conventional stochiometric 3-way catalyst engine for its low emission levels and to reduce fuel consumption by using new technologies such as variable valve actuation, down-sizing with supercharging, etc Beside these two approaches, there is a strong industrial need for an alternative highly efficient lean burn combustion system, which could provide CO2 advantages similar to stratified Diesel engines while solving the NOx emission problem of lean burn combustion, without depending on fuel sensitive and expensive after-treatment systems

Methods

Discussion

Conclusion