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A test program to characterize the benefits and challenges of applying a European series production catalyzed gasoline particulate filter (GPF) to a U.S. Tier 2 turbocharged light duty truck (3.5L Ecoboost Ford F150) in the underfloor location was initiated at the U.S. Environmental Protection Agency. The turbos and underfloor location keep the GPF relatively cool and minimize passive regeneration relative to other configurations. This study characterizes the relatively cool GPF in a lightly loaded state, approximately 0.1 to 0.4 g/L of soot loading, using four test cycles: 60 mph steady state, 4-phase FTP, HWFET, and US06. The lightly loaded underfloor GPF achieves 85-99% reduction in PM mass, 98.5-100.0% reduction in EC, and 65-91% reduction in filter-collected OC, depending on test cycle. The smallest reductions in PM and EC occur in the US06 cycle due to mild GPF regeneration caused by GPF inlet temperature exceeding 500°C. EC dominates filter-collected OC without a GPF, while OC dominates EC with a GPF. Composite cycle CO, THC, and NOx emissions are reduced by the washcoat on the GPF but the low temperature location of the GPF does not make best use of the catalyzed washcoat. Cycle average pressure drop across the GPF ranged from 1.25 kPa in the 4-phase FTP to 4.64 kPa in the US06 but did not affect BTE or CO2 emissions in a measurable way in any test cycle.

SHRNUTÍV článku je prezentován výsledek experimentálního průzkumu spalování zředěné směsi zemního plynu se vzduchem při nízkém zatížení zážehového motoru. Zředění směsi vzduchem a recirkulujícími spalinami bylo porovnáno s provozem na stechiometrickou směs. Byla provedená detailní termodynamická analýza záznamu průběhu tlaku ve válci a byl vyhodnocen a analyzován průběh hoření. Výsledky naznačují potenciál ke zlepšení účinnosti motoru a současně možnost významného snížení emise NO X v surových spalinách v porovnání se spalováním homogenní stechiometrické směsi. KLÍČOVÁ SLOVA: CHUDÁ KONCEPCE, RECIRKULACE SPALIN, VÝVIN TEPLA, EMISE NO X ABSTRACTAn experimental investigation of homogeneous mixture combustion in a natural gas fuelled spark ignition engine at low load operation is presented in the paper. The low energy density of the mixture is a well-known limiting factor for the peak cycle temperature during combustion of the homogeneous mixture in spark ignition (SI) engines. The most exact approach for description of fully optimized implementation of mixture dilution with a conventional combustion system is presented. This is a starting point for comparison with an advanced combustion system being prepared as the next step in ongoing research activity. The two methods of mixture dilution: 1) air dilution, and 2) cooled exhaust gas recirculation (EGR) are compared with the stoichiometric operation. Real-world data are presented, taking into account constraints observed on a particular engine. Detailed thermodynamic analysis of the cylinder pressure traces is performed and the combustion rates are evaluated and analyzed. The results show an increase in engine thermal efficiency (up to 7%) together with a significant reduction of nitrogen oxides (NO X ) emissions (up to 70%) in raw exhaust gas compared to the homogeneous stoichiometric spark ignition operation, which is a conventional combustion strategy. Advanced combustion systems can further extend the improvement in both efficiency and NO X emissions.