Near Zero NOx Emissions and High Fuel Efficiency Diesel Engine: the Naditm Concept Using Dual Mode Combustion

B Walter,B Gatellier

doi:10.2516/ogst:2003007

Abstract

The part of Diesel engines on the transport market should increase within the years to come thanks to their high thermal efficiency coupled with low carbon dioxide (CO2) emissions, provided their nitrogen oxides (NOx) and particulate emissions are reduced. At present, adequate after-treatments, NOx and particulates matter (PM) traps are developed or industrialized with still concerns about fuel economy, robustness, sensitivity to fuel sulfur and cost because of their complex and sophisticated control strategy. New combustion process such as homogeneous charge compression ignition are investigated for their potential to achieve near zero particulate and NOx emissions. Their main drawbacks are too high unburned hydrocarbons (HC) and carbon monoxide (CO) emissions, combustion control at high load and then limited operating range and power output. As an answer for challenges the Diesel engine is facing, IFP has developed a combustion system able to reach near zero particulate and NOx emissions while maintaining performance standards of the DI Diesel engines. This dual mode engine application called NADITM (Narrow Angle Direct Injection) applies homogeneous charge compression ignition at part load and switches to conventional Diesel combustion to reach full load requirements. At part load (including Motor Vehicle Emissions Group-MVEG-and Federal Test Procedure-FTP-cycles), HCCI combustion mode allows near zero particulate and NOx emissions and maintains very good fuel efficiency close to an Euro III Diesel engine. At 1500 and 2500 rpm, NADITM reaches 0. 6 and 0. 9 MPa (6 and 9 bar) of indicated mean effective pressure (IMEP) with emissions of NOx and particulate under 0. 05 g/kWh. That means respectively 100 and 10 times lower than a conventional Diesel engine. At full load, NADITM system is consistent with future Diesel engine power density standard. At 4000 rpm, 50 to 55 kW/l has been reached with conventional limiting factors and engine parameters settings. Advanced engine technology such as further generation of common rail fuel injection system, Variable Valve Actuation (VVA), Variable Compression Ratio (VCR) engine or electric assisted turbocharger will be useful for the well identified next development steps of the concept.

Highlights

HCCI combustion engines constitute alternative or complementary answers to the sophisticated and complex aftertreatments strategy, which seems to be compulsory for classical Diesel engine
The results obtained in HCCI mode with the NADITM concept geometry are compared to results with conventional combustion mode with standard geometry using a compression ratio of 18:1, and parameters settings consistent with Euro III emissions standards
For the 1500 rpm tests, only a light boost pressure has been used above 0.5 MPa of indicated mean effective pressure (IMEP) with the lowest compression ratio

Summary

Introduction

HCCI combustion engines constitute alternative or complementary answers to the sophisticated and complex aftertreatments strategy, which seems to be compulsory for classical Diesel engine. Their principle consists in preparing a highly diluted by burned gases air/fuel mixture, in achieving its simultaneous ignition in the whole space of the combustion chamber and in precisely controlling such combustion for the best performance in terms of efficiency and pollutant emissions. There are two types of engine using port-injection, one working with liquid fuel and other working with gaseous fuel They generally use an electronically driven gasoline injector in the intake pipe, and in some cases, two injectors with two different fuels in 2 intake pipes (LIT). The Tokyo Gas Corporation uses a mixing chamber before the intake pipe, to promote gas and air mixing

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Conclusion