Development of an Improved Fractal Model for the Simulation of Turbulent Flame Propagation in SI Engines Politecnico di Torino

Format:

Conference/Event

Author/Creator:

Baratta, Baratta, author.

Contributor:

Catania, A. E.

Spessa, E.

Vassallo, A.

Conference Name:

7th International Conference on Engines for Automobile (2005-09-11 : Naples, Italy)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Naples, ITALY Consiglio Nazionale delle Ricerche 2005

Summary:

The necessity for further reductions of in-cylinder pollutantformation and the opportunity to minimize engine development andtesting times highlight the need of engine thermodynamic cyclesimulation tools that are able to accurately predict the effects offuel, design and operating variables on engine performance.In order to set up reliable codes for indicated cycle simulationin SI engines, an accurate prediction of heat release is required,which, in turn, involves the evaluation of in-cylinder turbulencegeneration and flame-turbulence interaction. This is generallypursued by the application of a combustion fractal model coupledwith semi-empirical correlations of available geometrical andthermodynamical mass-averaged quantities. However, the currentlyavailable correlations generally show an unsatisfactory capabilityto predict the effects of flame-turbulence interaction on burningspeed under the overall flame propagation interval.Therefore, in the present paper, a new correlation that improvesthe turbulent burning speed calculation is developed. It featuresan original definition of the outer turbulence cutoff length scale,based on the flame front area, and takes account of the increasedtransfer across the flame front of both radical species and heatfor high in-cylinder densities. The correlation has been applied tocalculate the burning speeds in the cylinder of a naturallyaspirated bi-fuel engine for a wide range of engine speeds (N \me2000-4600 rpm), loads (bmep \me 200-790 kPa), relative air-fuelratios (RAFR \me 0.80-1.30) and spark-advances (SA ranging from 8deg retard to 2 deg advance with respect to MBT), under bothgasoline and CNG operations.The computed burning speeds were then compared to those stemmingfrom the traditional correlation reported in the literature and tothe experimental flame propagation data. These latter wereextracted from the measured in-cylinder pressure traces by means ofa diagnostics technique previously developed by the authors. Theresults indicate that the burning speeds calculated through theauthors' model are in better agreement with the experimentaloutcomes than those derived from the traditional correlation widelyapplied in the literature

Notes:

Vendor supplied data

Publisher Number:

2005-24-082

Access Restriction:

Restricted for use by site license