Showing papers on "Spark-ignition engine published in 2013"

Airflow control systems and methods using model predictive control

Abstract: A torque requesting module generates a first torque request for a spark ignition engine based on driver input. A torque conversion module converts the first torque request into a second torque request. A setpoint control module generates setpoints for the spark ignition engine based on the second torque request. A vacuum requesting module requests an amount of vacuum within an intake manifold of the engine. The setpoint module selectively adjusts at least one of the setpoints based on the amount of vacuum requested. A model predictive control (MPC) module: identifies sets of possible target values based on the setpoints; generates predicted parameters based on a model of the spark ignition engine and the sets of possible target values, respectively; selects one of the sets of possible target values based on the predicted parameters; and sets target values based on the possible target values of the selected one of the sets.

The influence of fuel properties on particulate number emissions from a direct injection spark ignition engine

Abstract: The use of direct injection spark ignition (DISI) engines for passenger cars has increased; providing greater specific performance and lower CO 2 emissions. DISI engines, however, produce more particulate matter (PM) emissions than Port Fuel Injected (PFI) engines. Forthcoming European exhaust emissions legislation is addressing concerns over health effects of PM emissions. Accordingly, research into PM emission formation has increased. A model developed by Aikawa et al. (2010) for PFI engines correlated PM number emissions with the vapour pressure and the double bond equivalent (DBE) of the components of the fuel. However there was no independent control of these parameters. This study investigates a particulate emissions index for DISI engines. A single-cylinder optical access Spray Guided DISI engine was used to develop a Particulate Matter Number emissions Index (PN index) - modified from the PM index using industry standard measurements - through the use of model and commercially available fuels. Model fuels were designed using Raoult's law and UNIFAC such that the DBE and vapour pressure of the fuel mix could be varied. Engine tests were conducted, independently varying the DBE and the vapour pressure of the fuel. PM number emissions were measured using a Cambustion DMS500, the results were analysed alongside observations of the fuel spray to investigate the PN index. The PN index has also been used to evaluate emissions from two commercially available EN228 fuels. The results demonstrate that the trend of the PN index is followed both with model fuels and commercial gasolines.

Experimental characteristics of turbulent premixed flame in a boosted Spark-Ignition engine

Abstract: As combustion takes place in smaller combustion chambers at higher pressure, the development of boosted Spark-Ignition (SI) engines can induce non classical flame development. Moreover to limit abnormal combustion and thermal NOx production, a high dilution rate by exhaust gases is used. To improve the combustion processes occurring in SI engines and to validate new concepts, turbulent premixed combustion propagation is now estimated by using 3D CFD calculations, usually based on flamelet theory. However, this theory may be limited when the boosted engine is running in high diluted conditions. Therefore, in this paper, the flame characteristics of a stoichiometric iso-octane/air mixture were determined from in-cylinder measurements for a relatively high intake pressure and different dilution rates. By using an evaluation of both laminar and turbulent characteristics at real engine conditions, the trajectories of combustion processes occurring inside the cylinder were plotted in a Peters-Borghi diagram. Dilution induces a shift from the middle of the corrugated flamelet zone to the beginning of the thin reaction zones. Moreover, thanks to high speed PIV-flame tomography measurements, it was shown that dilution enhances flame-turbulence interactions and that the corrugation generated through dilution occurs at smaller scales than the integral length scales.

Exhaust emissions of methanol and ethanol unleaded gasoline blends in a spark ignition engine

Abstract: In this study, the effect of unleaded gasoline and unleaded gasoline blended with 5% and 10% of ethanol or methanol on the performance and exhaust emissions of a spark-ignition engine were experimentally investigated. The engine tests were performed by varying the engine speed between 1000 and 4000 rpm with 500 rpm period at threefourth throttle opening position. The results showed that brakespecific fuel consumption increased while brake thermal efficiency, emissions of carbon monoxide (CO) and hydrocarbon (HCs) decreased with methanol-unleaded gasoline and ethanol-unleaded gasoline blends. It was found that a 10% blend of ethanol or methanol with unleaded gasoline works well in the existing design of engine and parameters at which engines are operating.