Port Fuel Injection Spark Ignition Research Articles

Particle and nanoparticle characterization at the exhaust of internal combustion engines

The aim of this work is the characterization of the emissions of exhaust particles in terms of number size distribution and chemical—physical properties. Laser-induced incandescence and broadband ultraviolet—visible extinction and scattering spectroscopy were used at the exhaust of a common-rail diesel engine and of a port fuel injection (PFI) spark ignition (SI) engine. The optical results were compared with size distributions obtained with an electrical low-pressure impactor and a scanning mobility particle sizer. Moreover, the fundamental engine parameters and the particulate mass and gas concentrations were measured using conventional instrumentation. With respect to the diesel engine, the effect of the exhaust after-treatment was investigated. The exhaust gas recirculation influenced the particle size distribution in terms of number concentration owing to the formation of accumulation mode particles. The catalysed diesel particulate filter strongly reduced the particle number concentration in the loading phase. Effects on the chemical nature of the particles were observed during the filter regeneration phase. With respect to the PFI SI engine, high number concentrations of nanoparticles ( D<50nm) were measured for all the engine operating conditions. The chemical nature of the nanoparticles was investigated.

Post-Combustion In-Cylinder Vaporization During Cranking and Startup in a Port-Fuel–Injected Spark Ignition Engine

During port-fuel–injected (PFI) spark-ignition (SI) engine startup and warm-up fuel accounting continues to be a challenge. Excess fuel must be injected for a near stoichiometric combustion charge. The “extra” fuel that does not contribute to the combustion process may stay in the intake port or as liquid films on the combustion chamber walls. Some of this combustion chamber wall liquid fuel is transported to the engine’s oil sump and some of this liquid fuel escapes combustion and evolves during the expansion and exhaust strokes. Experiments were performed to investigate and quantify this emerging in-cylinder fuel vapor post-combustion cycle by cycle during engine startup. It is believed that this fuel vapor is evaporating from cylinder surfaces and emerging from cylinder crevices. A fast in-cylinder diagnostic, the fast flame ionization detector, was used to measure this behavior. Substantial post-combustion fuel vapor was measured during engine startup. The amount of post-combustion fuel vapor that develops relative to the in-cylinder precombustion fuel charge is on the order of one for cold starting (0 °C) and decreases to ∼13 for hot starting engine cycles. Fuel accounting suggests that the intake port puddle forms quickly, over the first few engine cranking cycles. Analysis suggests that sufficient charge temperature and crevice oxygen exists to at least partially oxidize the majority of this post-combustion fuel vapor such that engine out hydrocarbons are not excessive.

(3-18) Qualitative Laser-Induced Incandescence Measurements of Soot Emissions During Transient Operation of a Port Fuel-Injected Engine((D-2)Diagnostics 2-LII)

Beginning in 2004, all passenger cars and light-duty trucks sold in the U. S. will be required to meet the same emission regulations regardless of the fuel type (EPA Tier 2). Thus, for the first time gasoline-fueled vehicles will have to meet particulate matter emission standards that in the past have only been required of diesel-fueled vehicles. It is expected that contemporary port fuel-injected (PFI) engines with catalysts will be able to meet the requirements, which are currently based on particulate mass. In contrast, it is uncertain at this time whether the new generation of direct-injection gasoline engines can achieve certification. Furthermore, health risks are more strongly correlated with particle size and number density than with mass concentration. If new regulations are based on these parameters, gasoline engines will come under closer scrutiny. To help meet these new and anticipated regulations, improved particulate measurement techniques are needed. The two capabilities most urgently required are fast response to follow transients, and high-sensitivity to measure small amounts in short times. Laser-induced incandescence (LIT) offers these capabilities. The purpose of this paper is to demonstrate the use of LII for making time-resolved measurements of soot volume fraction during engine transients. The measurements presented were made at the exhaust-port exit of a production, four-valve, PFI spark-ignition engine with only one active cylinder. Optical access to the exhaust flow between the head and exhaust manifold was achieved by an optical flow channel with three windows, which permitted a laser beam to cross the exhaust steam while observed from above. Planar LII imaging was used to investigate the spatial distribution of soot across the exhaust port ; analog LII measurements were made to measure the soot volume fraction during transient engine operation. The planar LII images obtained in the exhaust port show that soot concentration varies widely both spatially and temporally, from cycle-to-cycle. For some cycles the soot distribution was relatively uniform, whereas for others it varied greatly between the two valves. On average, the amount of soot emitted from each valve was different. For open-valve injection, the soot volume fraction increased rapidly over the first 20 cycles of a simulated cold start, and then continued to increase at a slower rate for the duration of the 300 cycle test. In contrast, for closed-valve injection the soot volume fraction rose very quickly to a maximum in less than 10 cycles, and then fell rapidly to a low concentration by about 50 cycles, after which it continued to fall gradually for the remainder of the test. We believe the large differences in the soot behavior for these two cases is related to the dynamics of the in-cylinder wall films, and in particular, to the changing composition of the films as wall temperatures increase. For a snap-throttle transient, where the manifold pressure was suddenly increased from 40 to 98 kPa, the soot volume fraction increased steadily during the throttled period, fell to near zero at the time of the snap-throttle, and then increased steadily to a value approximately ten times greater than for the throttled period. Severe window fouling occurred during the wide-open-throttle portion of this test, resulting in a 30% loss in laser beam transmission after engine shutdown. This fouling problem limited this study to qualitative observations, and represents the main disadvantage of optical techniques for engine exhaust studies. Fortunately, it is a design problem that can be corrected, although at the expense of added complexity.

Pollutant formation and control in spark-ignition engines

An experimental study was conducted in a port-fuel injection (PFI) spark-ignition (SI) engine fueled with acetone-butanol-ethanol (ABE) and gasoline. 30 vol% ABE blends with different component ratios (A:B:E = 3:6:1, 6:3:1, and 5:14:1), referred to as ABE(3:6:1)30, ABE(6:3:1)30, and ABE(5:14:1)30, were used as test fuels. Additionally, 30 vol% ethanol and 30% vol.% butanol blended with 70 vol% gasoline, referred to as E30 and B30, respectively, were also used as test fuels. Both the regulated emissions, which include unburned hydrocarbons (UHC), carbon monoxide (CO), and nitrogen oxide (NOx), and unregulated emissions, including acetaldehyde, 1,3-butadiene, benzene, toluene, ethylbenzene, and xylene (BTEX), were investigated under various conditions. The experiments were conducted at an engine speed of 1200 rpm and at engine loads of 3, 4, 5, and 6 bar brake mean effective pressure (BMEP) under various equivalence ratios (φ = 0.83–1.25). The results indicated that ABE(6:3:1)30 had the lowest UHC and CO emissions, with ABE(3:6:1)30 having slightly higher NOx emissions. As for unregulated emissions, B30 showed the highest acetaldehyde emission and ABE(6:3:1)30 had the lowest among all the fuel blends. ABE(3:6:1)30 and ABE(6:3:1)30 showed a reduction in 1,3-butadiene emission. Regarding the BTEX emissions, an overall reduction was observed for all the fuel blends, with ABE(3:6:1)30 having shown the lowest BTEX emissions among all the test fuels. The results indicate that ABE could be used as a promising alternative fuel in SI engines, owing to the reduction in emissions.