Hydrocarbon Emissions from Spark Ignition Engines
01 Jan 2010-pp 147-166
TL;DR: In this article, the absorption and desorption of fuel by cylinder lubricating oil films has been modelled using principles of mass transfer in a Diesel and a spark ignition engine.
Abstract: To contrast the phenomenon of HC formation in a Diesel and a spark ignition engine, a chapter is included on the latter. The absorption and desorption of fuel by cylinder lubricating oil films has been modelled using principles of mass transfer in this Chapter. Henry’s Law for a dilute solution of fuel in oil is used to relate gas to liquid phase fuel concentrations. Mass transfer conductances in gas and liquid phases are considered, the former via use of Reynolds’s Analogy to engine heat transfer data, the latter through assuming molecular diffusion through an effective penetration depth of the oil film. Oxidation of desorbed fuel is assumed complete if the mean of burned gas and lubricating oil film temperatures is greater than 100 K. Below this value, the desorbed fuel is considered to contribute to hydrocarbon emissions. Comparison with engine test data corroborates the absorption/desorption hypothesis. The model indicates the equal importance of gas and liquid phase conductance.
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TL;DR: In this paper, a semi-empirical modeling approach based on an extensive parametric study using a spark-ignition port-injection engine is presented to derive engine-out emission models for each regulated pollutant.
Abstract: This study presents a semi-empirical modeling approach based on an extensive parametric study using a spark-ignition port-injection engine. The experimental results are used to derive engine-out emission models for each regulated pollutant (CO, HC, NOx) as a function of engine operating parameters. Such parameters include engine speed, intake manifold pressure, equivalence ratio, and spark advance. The proposed models provide accurate predictions over a large range of engine operating conditions. The adequate accuracy and low computational burden of the models are promising in the context of optimal control theory. Dynamic programming is applied in order to find the best operating parameters that define trade-off between fuel consumption and emissions over driving cycles.
8 citations
Cites background from "Hydrocarbon Emissions from Spark Ig..."
...Simultaneously, a decrease in the wall temperature is observed [22]....
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...Furthermore, increasing φ results in the raise of fuel vapor concentration in the bulk gas which will increase the absorption and hence the desorption from the oil layer [22]....
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References
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Book•
01 Jan 1955
TL;DR: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part, denoted as turbulence as discussed by the authors, and the actual flow is very different from that of the Poiseuille flow.
Abstract: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part. These actual flows show a special characteristic, denoted as turbulence. The character of a turbulent flow is most easily understood the case of the pipe flow. Consider the flow through a straight pipe of circular cross section and with a smooth wall. For laminar flow each fluid particle moves with uniform velocity along a rectilinear path. Because of viscosity, the velocity of the particles near the wall is smaller than that of the particles at the center. i% order to maintain the motion, a pressure decrease is required which, for laminar flow, is proportional to the first power of the mean flow velocity. Actually, however, one ob~erves that, for larger Reynolds numbers, the pressure drop increases almost with the square of the velocity and is very much larger then that given by the Hagen Poiseuille law. One may conclude that the actual flow is very different from that of the Poiseuille flow.
17,321 citations
Book•
01 Jan 1962TL;DR: In this paper, Kreith, Manglik, and Bohn present relevant and stimulating content in this fresh and comprehensive approach to heat transfer, acknowledging that in today's world classical mathematical solutions to Heat Transfer problems are often less influential than computational analysis.
Abstract: PRINCIPLES OF HEAT TRANSFER was first published in 1959, and since then it has grown to be considered a classic within the field, setting the standards for coverage and organization within all other Heat Transfer texts. The book is designed for a one-semester course in heat transfer at the junior or senior level, however, flexibility in pedagogy has been provided. Following several recommendations of the ASME Committee on Heat Transfer Education, Kreith, Manglik, and Bohn present relevant and stimulating content in this fresh and comprehensive approach to heat transfer, acknowledging that in today's world classical mathematical solutions to heat transfer problems are often less influential than computational analysis. This acknowledgement is met with the emphasize that students must still learn to appreciate both the physics and the elegance of simple mathematics in addressing complex phenomena, aiming at presenting the principles of heat transfer both within the framework of classical mathematics and empirical correlations.
2,194 citations
2,050 citations
01 Feb 1978
TL;DR: In this article, the authors developed correlations for the ignition delay and combustion energy release intervals in a homogeneous charge, spark-ignited engine with four fundamental quantities: turbulent integral scale, turbulent micro-scale, turbulent intensity, and laminar flame speed.
Abstract: Correlations for the ignition delay and combustion energy release intervals in a homogeneous charge, spark-ignited engine are developed. After incorporation within a simplified engine cycle simulation, predicted values of these two combustion parameters are compared to experimental engine data. The correlations are based on four fundamental quantities--the turbulent integral scale, the turbulent micro-scale, the turbulent intensity, and the laminar flame speed. The major assumptions include: (1) the turbulent integral scale is proportional to the instantaneous chamber height prior to flame initiation; (2) angular momentum is conserved in the individual turbulent eddies ahead of the flame front (i.e., a ''rapid distortion'' turbulence model); and (3) the turbulent intensity scales with the mean piston speed. Two empirical constants scale the correlations to a given engine. Predicted values for the ignition delay and burn intervals show good agreement with experimental results for wide variations in engine operating and design conditions (e.g., engine speed and load, spark timing, EGR, air-fuel ratio, and compression ratio). In addition, the shapes of the predicted mass fraction burned curves agree well with published data.
221 citations