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12The Gasoline Direct Injection engines are an important source of ultra-fine particulate matter. 13Significant research effort is still required as improved understanding of soot formation is critical in 14considering further development or adoption of new technologies. Experimental measurements of 15 engine-out soot emissions have been taken from a modern Euro IV GDI engine at part-load 16operating conditions. The engine speed and torque were varied in the range 1600 to 3700 rev/min, 17and 30 to 120 Nm, respectively. The engine was invariably operated in stoichiometric and 18 homogeneous combustion mode, with fuel injection early in the intake stroke. The results indicate 19 that for engine load in excess of 3 bar Brake Mean Effective Pressure, due to incomplete gas-20 phase mixture preparation, a consistent linear correlation establishes between combustion duration 21 and soot particle number. On average, a six-fold increase in number concentration between 1.0 22 and 6.0x10 6 particle per cc, arises from shortening the rapid duration of 4 crank angle degrees. For 23 engine speed in excess of 3000 rev/min and load in excess of 7 bar BMEP, this correlation 24 appears to be superseded by the effects of spray-to-piston impingement and consequent pool-fire. 25Three main areas of concern have been identified within the part-load running envelope: 1. the 26 higher load-lower speed range and 2. the mid load-mid speed range, where high nucleation rates 27induce copious increases of engine-out soot mass; 3. the upper part-load range where, most likely 28as a result of spray impingement, high levels of soot concentration (up to 10 million particles per 29 cc) are emitted with very small size (23-40 nm). 30 31 321. Introduction 33 34Compared to more conventional Port-Fuel Injection (PFI) engines, Gasoline Direct Injection (GDI) 35 engines show a significant 5 to 15% improvement in fuel economy [1], especially because of higher 36 volumetric efficiency and higher knock resistance, which allow the use of generally higher 37 compression ratios with sizeable benefits in thermal efficiency and specific power output. In spite of 38 this, GDI engines are an important source of environmental pollution because of their fine and 39 ultrafine Particulate Matter (PM) emissions. Sizeable research effort has been devoted in the last 40 two decades to investigate the causes of soot emission from this comparatively young technology. 41 Recent medical research work, showing that aerosol particles in the ultrafine size range (diameters 42 of less than 100 nm) cause adverse health effects [2-6], continue to give relevance and impetus to 43 GDI research. Pulmonary inflammation, asthma and cardiovascular conditions are some of 44 problems associated with the deposition of soot in the respiratory tracts. Health risks generally 45 increase with decreasing particle size and increasing concentration. A recent, large, European 46 study associate an 18% increased risk of lung cancer to a 5x10 -6 μg/cc increase of PM 2.5 in 47 atmospheric air [7]. C...

The charge burn characteristics of a port-injected spark ignition engine with a pentroof combustion chamber and variable valve timing have been investigated experimentally. The engine was run under stoichiometric mixture operating conditions over ranges of intake and exhaust valve timings, engine speed, and engine load. Empirical functions have been developed for the 0-90 per cent mass fraction burned angle and the form factor, which define Wiebe function fits to the mass fraction burned variation in the crank angle domain. The burn angle and form factor have been related to the level of charge dilution by burned gas, engine speed, ignition timing, and charge density at spark timing. The dilution level has the strongest influence on the burn rate and profile. The dilution level varied with intake and exhaust valve timings, external exhaust gas recirculation, and engine load. The results indicate that intake and exhaust valve timings influence combustion primarily by modifying the charge dilution with burned gas and charge density.

CFD modeling of transpired solar collectors and characterisation of multi-scale airflow and heat transfer mechanisms.