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Problem areas of general applicability in the field of detection of knock in commercial engines are discussed. These include (a) the expedients adopted to reduce the effect of noise on the sensibility of the measuring instrument, (b) the characteristics of the pass-band electronic filter employed in this type of instrumentation and possible distortion effects, (c) the type and mounting of the transducer employed, with emphasis on devices outside the combustion chamber, and (d) the interpretation of the phenomena as detected with the devices used and its relation to the energy released from knock and the danger of mechanical damage.

Aim of this work is to present and discuss the possibility and the limits of two zone models for spark-ignition engines using a detailed kinetic scheme for the characterization of the evolution of the air-fuel mixture, while an equilibrium approach is used for the burnt zone. Simple experimental measurements of knocking tendency of different fuels in ideal reactors, such as rapid compression machines and shock tube reactors, cannot be directly used for the analysis of octane numbers and sensitivity of hydrocarbon mixtures. Thus a careful investigation is very useful, not only of the combustion chamber behavior, including the modelling of the turbulent flame front propagation, but also of the fluid dynamic behavior of the intake and exhaust system, accounting for the volumetric efficiency of the engine.

This work presents a general model for the prediction of octane numbers and knock propensity of different fuels in SI engines. A detailed kinetic scheme of hydrocarbon oxidation is coupled with a two zone, 1-D thermo-fluid dynamic simulation code (GASDYN) [1]. The validation of the kinetic scheme is discussed on the basis of recent experimental measurements. CFR engine simulations for RON and MON evaluation are presented first to demonstrate the capabilities of the coupled model. The model is then used to compare the knock propensity of a gasoline “surrogate” (a pure hydrocarbon mixture) and PRFs in a current commercial engine, resulting in a simulation of “real world” octane number determination, such as Bench Octane Number (BON). The simulation results agree qualitatively with typical experimental trends.

The total particulate emissions, particle mass and number/size distributions of two modern diesel vehicles, were measured during the ECE15+EUDC test cycle and constant speed tests at idle, 32, 50 and 120 km/h. One car was equipped with a standard direct injection rotary pump while the other was equipped with the common-rail technology. The emissions were tested with the cars running on a “standard” and on a “clean” sulphur-free, low aromatics and low density diesel fuel. It was seen that the common rail engine was emitting significantly less particle mass than the standard direct injection engine. The use of the clean fuel improved all emission but the CO2 and NOx. Finally, the use of Low-Pressure Impactors and of a Scanning Mobility Particle Sizer resulted in valuable information on the size distribution of particles emitted by the vehicles.

Carbonaceous material associated with potent carcinogens such as 3-4 benz(a)pyrene (BaP) and other polynuclear aromatic (PNA) hydrocarbons constitutes by far the greatest part of the particulate found in the exhaust gases of an internal combustion engine. The probable precursors of carbon particles are radicals formed in the incomplete combustion zone while their nucleation is made possible by ions originating in the flame. Ion current instantaneous values were measured by means of a modified Langmuir's probe, thus calculating thickness and speed of the flame in an engine cylinder. Relations between ion current and collected soot weight were examined. Fuel quality and additive influences over carbon and PNA formation were obtained.