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The local equivalence ratio, Φ, was measured in fuel jets using laser-induced spontaneous Raman scattering in an optical heavy duty diesel engine. The measurements were performed at 1200 rpm and quarter load (6 bar IMEP). The objective was to study factors influencing soot formation, such as gas entrainment and lift-off position, and to find correlations with engine-out particulate matter (PM) levels. The effects of nozzle hole size, injection pressure, inlet oxygen concentration, and ambient density at TDC were studied. The position of the lift–off region was determined from OH chemiluminescence images of the flame. The liquid penetration length was measured with Mie scattering to ensure that the Raman measurement was performed in the gaseous part of the spray. The local Φ value was successfully measured inside a fuel jet. A surprisingly low correlation coefficient between engine-out PM and the local Φ in the reaction zone were observed.

The Homogeneous Charge Compression Ignition (HCCI) combustion concept is currently under widespread investigation due to its potential to increase thermal efficiency while greatly decreasing harmful exhaust pollutants. Simulation tools have been developed to explore the implications of initial mixture thermodynamic state on engine performance and emissions. In most cases these modeling efforts have coupled a detailed fuel chemistry mechanism with empirical descriptions of the in-cylinder heat transfer processes. The primary objective of this paper is to present a fundamentally based boundary layer heat transfer model. The two-zone combustion model couples an adiabatic core zone with a boundary layer heat transfer model. The model predicts film coefficient, with approximately the same universal shape and magnitudes as an existing global model.

When automobile hydrocarbons are exhausted into the atmosphere in the presence of NOx and sunlight, ground-level ozone is formed. While researchers have used Maximum Incremental Reactivity (MIR) factors to estimate ozone production, this procedure often overestimates Local Ozone Production (LOP) because it does not consider local atmospheric conditions. In this paper, an enhanced MIR methodology for estimating actual LOP attributable to a vehicle in a particular ozone problem area is presented. In addition to using tabulated MIR factors, the procedure also uses local hydrocarbon reaction terms and a relative mechanistic reactivity term that account for local atmospheric conditions. Through this approach, the effects of hydrocarbon reaction rates, hydrocarbon residence times, and prevailing HC/NOx ratio are accounted for. The procedure is intended to enable automotive engineers to more realistically estimate actual local ozone production resulting from hydrocarbon emissions.

Exhaust and evaporative emissions from seven late model cars were measured for six oxygenated test fuels and one non-oxygenated reference fuel. The test fuels contained 2.7 wt% oxygen from either MTBE, DIPE, TAME or a mixture of two or more of these oxygenates. The fuels were designed to meet 1995 RFG requirements, with nominal targets of 25% aromatics, 1% benzene and a vapor pressure of 7.5 psi. The remaining fuel properties were held constant. Vehicle emissions were speciated to determine levels of regulated air toxics, and ozone forming potentials were calculated. No differences in total VOC, air toxics or ozone forming potential were observed among the test fuels. These results indicate that MTBE, DIPE and TAME can be used concurrently and interchangeably at levels of 2.7 wt% oxygen.

A global, systems-level model which characterizes the thermal behavior of internal combustion engines is described in this paper. Based on resistor-capacitor thermal networks, either steady-state or transient thermal simulations can be performed. A two-zone, quasi-dimensional spark-ignition engine simulation is used to determine in-cylinder gas temperature and convection coefficients. Engine heat fluxes and component temperatures can subsequently be predicted from specification of general engine dimensions, materials, and operating conditions. Emphasis has been placed on minimizing the number of model inputs and keeping them as simple as possible to make the model practical and useful as an early design tool. The success of the global model depends on properly scaling the general engine inputs to accurately model engine heat flow paths across families of engine designs. The development and validation of suitable, scalable submodels is described in detail in this paper.

Simultaneous measurements of early flame speed and local measurements of the major parameters controlling the process are presented. The early flame growth rate was captured with heat release analysis of the cylinder pressure. The local concentration of fuel or residual gas were measured with laser induced fluorescence (LIF) on isooctane/3-pentanone or water. Local velocity measurements were performed with laser doppler velocimetry (LDV). The results show a significant cycle to cycle correlation between early flame growth rate and several parameters. The experiments were arranged to suppress all but one important factor at a time. When the engine was run without fuel or residual gas fluctuations, the cycle to cycle variations of turbulence were able to explain 50 % of the flame growth rate fluctuations. With a significantly increased fluctuation of F/A, obtained with port fuelling, 65% of the growth rate fluctuation could be explained with local F/A measurements.

Predicting the effects of transient heat conduction in low-heat-rejection engine components have been analyzed by applying instantaneous boundary conditions throughout a diesel engine thermodynamic cycle. This paper describes the advantages and disadvantages of one-dimensional finite difference and two-dimensional finite element methods by analyzing simple and complicated geometries like diesel bowl-in pistons. Also the performance characteristics of plasma sprayed zirconia, partially stabilized zirconia, and a monolithic reaction bonded silicon nitride ceramic materials are discussed and compared. Finite element studies have indicated that the steep temperature gradients associated with cyclic temperature swings in excess of 400 K may contribute to the failure of ceramic coatings near the corner joining the surface of the piston and the surface of the bowl for bowl-in pistons.