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Determining selected diesel engine combustion descriptors based on the analysis of the coefficient of variation of in-chamber pressure

Bąkowski A., Radziszewski L.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2015

Vol. 63, nr 2

457--464

This paper presents a method that uses the coefficient of variation (COV) of pressure in a diesel engine combustion chamber to determine the crank angle degree (CAD) for which the heat release rate (HRR) reaches the maximum value. The COV was proposed for determining the point corresponding to the angle of start of combustion (SoC). Regression models were fit with these descriptors for the engine powered by diesel, biodiesel or a combination of both, operating under full- or part- load conditions. The uncertainty parameter in these models was determined. Good agreement between the experimental results and the literature data shows the validity of the analysis.

The effect of exhaust gas recirculation on the process of combustion in the self-ignition engine

Ambrozik T., Kosno M.

Journal of KONES

2014

Vol. 21, No. 2

7--14

The paper compares the basic parameters of the process of combustion in the Fiat MultUet 1.3 SDE 90 KM with and without an exhaust gas recirculation system, running according to load characteristics with the following engine crankshaft rotational speeds: n=l200 ipm, 1750 rpm and 3000 rpm. During testing, the engine was supplied with commercial diesel oil. The tested engine was provided with external exhaust gas recirculation consisting in supplying a specific amount of exhaust gas back to the cylinder via an EGR electric solenoid valve. The exhaust gas delivered to the cylinder was cooled. Exhaust gas is composed of inert gases that do not take part in the combustion process. This causes, above all, a lower rate of pressure increase in the cylinder and a lower heat release rate. Thanks to exhaust gas recirculation, lower maximal temperatures prevail in the cylinder, and the engine's operation is "softer." During experimental testing, the variation of cylinder pressure and chamber pressure, the injector operation control current magnitude, effective power, torque and the hourly fuel consumption, as well as the exhaust gas recirculation rate. Actual indicator diagrams plotted were used for determining the heat release characteristics, based on which the percentage fractions of the burned out fuel charge injected during one engine running cycle namely 5, 10, 50 and 90% fractions were determined. In addition, the indicator indices were determined. The paper has demonstrated the effect of exhaust gas recirculation on the processes occurring inside the cylinder in the self ignition internal combustion engine.