Near zero NOx emissions and high fuel efficiency diesel engine: The NADITM concept using dual mode combustion

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 NADI™ (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, NADI™ 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, NADI™ 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.