Lean and ultra-lean CNG engines require innovative strategies to allow stable combustion while maintaining performance standards and emission reduction. One of these strategies is the employment of active pre-chamber configurations which represent a viable solution for Heavy-Duty engines, with their larger cylinders and space availability compared to smaller engines. Active pre-chambers are auxiliary combustion chambers that can initiate the stable combustion of lean mixtures (with air-to-fuel ratios, ? greater than 1.5) without compromising efficiency and stability requirements. In this work three pre-chamber nozzles differing for the orifice diameter were tested in a stationary heavy-duty 6-cylinder engine (originally a compression ignition engine) converted to work with a single cylinder and spark ignition operated. An extensive test matrix was carried out to perform spark timing, global lambda and load target sweeps in order to assess the behaviour of the three nozzles with respect to the changing operating conditions. Analysis of in-cylinder pressure traces and heat release rate allowed to unveil the characteristics of the combustion phasing starting from the pre-chamber to the development in the main chamber, relating these to the performance of the engine in terms of emissions, efficiency and stability. The key role of pre-chamber combustion development on the overall in-cylinder combustion phenomena was assessed, determining the more effective values of the varied parameters in terms of efficient operation and emissions.
COMBUSTION DEVELOPMENT ANALYSIS IN LEAN HEAVY-DUTY CNG ENGINES WITH ACTIVE PRE-CHAMBER
CBeatrice
2021
Abstract
Lean and ultra-lean CNG engines require innovative strategies to allow stable combustion while maintaining performance standards and emission reduction. One of these strategies is the employment of active pre-chamber configurations which represent a viable solution for Heavy-Duty engines, with their larger cylinders and space availability compared to smaller engines. Active pre-chambers are auxiliary combustion chambers that can initiate the stable combustion of lean mixtures (with air-to-fuel ratios, ? greater than 1.5) without compromising efficiency and stability requirements. In this work three pre-chamber nozzles differing for the orifice diameter were tested in a stationary heavy-duty 6-cylinder engine (originally a compression ignition engine) converted to work with a single cylinder and spark ignition operated. An extensive test matrix was carried out to perform spark timing, global lambda and load target sweeps in order to assess the behaviour of the three nozzles with respect to the changing operating conditions. Analysis of in-cylinder pressure traces and heat release rate allowed to unveil the characteristics of the combustion phasing starting from the pre-chamber to the development in the main chamber, relating these to the performance of the engine in terms of emissions, efficiency and stability. The key role of pre-chamber combustion development on the overall in-cylinder combustion phenomena was assessed, determining the more effective values of the varied parameters in terms of efficient operation and emissions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
