Sub-23 particle control strategies towards Euro VII HD SI natural gas engines

Abstract

Approaching Euro VII regulation limits for natural gas engines represents an arduous but not impossible challenge.The technological improvement and research progress in propulsion systems can offer strong tools in the achievement of next emission target. The efforts in this field are justified by the interests in natural gas powertrains that represent an alternative solution mainly in case of Heavy-Duty engines for off-road and transport applications. One of the aspects involving the OEMs effort is the particle number emissions abatement, that, due to the next future stringent limits involving sub-23 nm particles, represents a challenge also in case of natural gas fueled engines.The present paper describes the potentiality offered by different strategies in the control of particles emitted by Heavy-Duty natural gas engines. Three approaches will be described and analyzed using experimental characterization carried out by the authors with the use of an engine test bench. Assuming that the major source of particles derives from the lube oil combustion, firstly the effect of improved piston ring pack design has been assessed, comparing two versions of the same engine.Secondly the quality of lubricant oils in particle formation has been evaluated, testing oils with improved chemical/physical properties.A last aspect analyzed was the evaluation of the particulate filter technology capability when applied to a natural gas engine, a novelty in the scientific literature.All the investigated approaches proofed powerful tools in the control of sub-23 particle, paving the way for natural gas engines compliant with Euro VII PN limits.