9.docx - The present work uses a two zone combustion model to study some gasoline engine combustion peculiarities cylinder pressure data at a

# 9.docx - The present work uses a two zone combustion model...

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The present work uses a two zone combustion model to study some gasoline engine combustion peculiarities, cylinder pressure data at a compression ratio of 8.5, running at 1800 rpm, and using fuel air equivalence ratios of 0.82, 0.84, 0.88, 0.92, 0.97 and 1.01 were used to analyze the power cycle. Cyclic pressure dispersion was noticed although air and fuel flows control were taken, showing pV diagrams with poor working condition when engine operates lean. Mass burned

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fraction, combustion duration, burned speed, flame radius growth, and other mixture richness indices were calculated using series of 30 cycles of pressure data. A computer program based on First Law of Thermodynamics, continuity and ideal gas equations was used to determine the mass and burned speed profiles as a function of mixture richness, it manages routines to find the working fluid composition and properties, it uses the Annand heat transfer model, and utilizes other
mathematical relations among richness, density, pressure, temperature and residual gas fraction physical parameters. The results show long combustion duration during expansion with engine lean operation, making that engine power cycles have poor efficiency, too much instability, low flame burned speed, and important power lost. Key words: spark ignition engine, two zone combustion model, mass burned profile, cyclic pressure dispersion, equivalence ratio, gasoline engine

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56 Martín et al. Science and Engineering Magazine. Vol. 29, No. 1, December-March, 2008 1 Nomenclature Padm: intake pressure. Tadm: admission temperature. Tamb: room temperature. AAE: spark advance angle, apms. m: mass after leaks. m i : initial mass. C: leakage coefficient. AND : variation of internal energy per unit of time. W : power. Q
: heat flow transferred to the walls. s m : mass flow out. s h : enthalpy of exit. u: internal energy. X: mass fraction. R: gas mixture constant. a, b, c: empirical coefficients for the Annand model. A T : heat transfer area. k: thermal conductivity. A, B: auxiliary variables. D p : piston diameter on. Re: Reynolds number.

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T p : average temperature of the cylinder walls. S T : turbulent burning rate. A f : flame front area. S L : laminar combustion rate. S L, o : initial laminar combustion rate.
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