Simultaneous Reduction of Soot and NO_x Emissions by Means of the HCPC Concept: Complying with the Heavy Duty EURO 6 Limits without After-treatment System

摘要

Due to concerns regarding pollutant and CO_2 emissions, advanced combustion modes that can simultaneously reduce exhaust emissions and improve thermal efficiency have been widely investigated. The main characteristic of the new combustion strategies, such as HCCI and LTC, is that the formation of a homogenous mixture or a controllable stratified mixture is required prior to ignition. The major issue with these approaches is the lack of a direct method for the control of ignition timing and combustion rate, which can be only indirectly controlled using high EGR rates and/or lean mixtures. Homogeneous Charge Progressive Combustion (HCPC) is based on the split-cycle principle. Intake and compression phases are performed in a reciprocating external compressor, which drives the air into the combustor cylinder during the combustion process, through a transfer duct. A transfer valve is positioned between the compressor cylinder and the transfer duct. The compressor runs with a fixed phase delay with respect to the combustor. As a consequence, during the combustion process, air moves from the compressor cylinder to the combustor cylinder. Contemporary with the air transfer, fuel is injected into the transfer duct, evaporates and mixes with the air, bringing about the conditions needed for homogeneous combustion. This paper relates to CFD study of a Heavy Duty HCPC engine that provides ultra-clean combustion and diesel-like indicated thermal efficiency. As a matter of fact the HCPC Heavy Duty engine can comply with EURO 6 regulations without complicated and expensive aftertreatment systems.