The Effect of a Three-Way Catalytic Converter on Particulate Matter from a Gasoline Direct-Injection Engine During Cold-Start

Abstract

The effect of a three-way catalytic converter on particulate matter from a gasoline direct-injection engine during cold-start. AbstractThis work investigates the effect of a three-way catalytic converter and sampling dilution ratio on nano-scale exhaust particulate matter emissions from a gasoline direct-injection engine during cold-start and warm-up transients. Experimental results are presented from a four cylinder in-line, four stroke, wall-guided direct-injection, turbo-charged and inter-cooled 1.6 l gasoline engine. A fast-response particulate spectrometer for exhaust nano-particle measurement up to 1000 nm was utilised. It was observed that the three-way catalytic converter had a significant effect on particle number density, reducing the total particle number by up to 65 % over the duration of the cold-start test. The greatest change in particle number density occurred for particles less than 23 nm diameter, with reductions of up to 95 % being observed, whilst the number density for particles above 50 nm diameter exhibited a significant increase. The exhaust temperature plays a significant role on the influence of the catalytic converter on the nano-scale particulate matter. It is evident that the dilution ratio of the exhaust sample has a distinct effect on the particulate matter number and size distribution, influencing the engine-out PM more significantly than the tailpipe-out PM during cold-start engine operation. The catalytic converter also has a considerable effect on the estimated total particle mass.

Nanoparticle Filtration Characteristics of Advanced Metal Foam Media for a Spark Ignition Direct Injection Engine in Steady Engine Operating Conditions and Vehicle Test Modes

“…The particle reduction characteristics of the spark ignition direct injection (SIDI) engine with a three-way catalytic converter (TWC) have been well investigated in previous studies [33][34][35]. Substantial reduction of the sub-23 nm particles was observed in the downstream position of the TWC.…”

“…The system has two primary components: (1) a particle sampler system consisting of a sampling and a particle pre-classifier (cyclone with d50% = 2.5 μm); and (2) a particle conditioning and measurement system consisting of a volatile particle remover (VPR) and a particle number counter (PNC) unit. The VPR provides heated dilution, thermal conditioning of the sample aerosol, and secondary dilution for cooling and freezing of the sample before it enters into the PNC [34,35]. The PNC unit is a condensation particle counter (CPC 3010D, TSI, Shoreview, MN, USA) with the lower cut-off modified to 23 nm.…”

“…The DMS500 equipped with heated sample line and two stage dilution systems allowed direct sampling from the exhaust gas. The detectable particle size ranges of this equipment were 5-1000 nm and the time response was 200 milliseconds [18,[33][34][35]. The specifications of the tested fuel are presented in Table 2.…”

“…Substantial reduction of the sub-23 nm particles was observed in the downstream position of the TWC. The reduction mechanism of particles through the catalytic converter was categorized as partly due to oxidation and partly to coagulation [35]. Engine-out particles consist of combustion-generated solid carbon particles and some organic compounds [7][8][9]18,21].…”

“…Particle size distributions are generally classified into three modes: nucleation mode (5 nm < dp < 30 nm), accumulation mode (30 nm < dp < 1000 nm) and coarse mode (1000 nm < dp). Exhaust particles containing volatile organic compounds that are less than 23 nm in size formed during combustion in locally rich regions are substantially oxidized in the TWC, while almost all of the accumulation mode particles are passed through the catalyst without purification [25,27,[33][34][35]. Therefore, a cost-effective gasoline particulate filter (GPF) can be adopted for GDI vehicles to reduce the nano-PM emissions to satisfy future PN emission regulations [10,27,[29][30][31][36][37][38][39].…”