Effect of Cetane Number on Specific Fuel Consumption and Particulate Matter and Unburned Hydrocarbon Emissions from Diesel Engines

Renato Cataluña,Rosangela Da Silva

doi:10.1155/2012/738940

Renato Cataluña, Rosangela Da Silva

Open Access

https://doi.org/10.1155/2012/738940

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Abstract

This paper discusses the effect of ignition delay time in diesel engines on the formation of particulate matter, using fuel formulations with different sulfur concentrations from various sources. Our findings indicate that the cetane number has a significant influence on particulate matter emissions, especially in engines with mechanical fuel injection. The maximum pressure in the combustion chamber increases as the cetane number increases, favoring the increase in the cracking reactions of high molecular weight fractions remaining in the liquid state and thus increasing the production of particulate matter. In certain conditions, this increase in pressure has a beneficial effect on the thermal efficiency of the cycle. Higher temperatures in the combustion chamber augment the speed of oxidation, reducing unburned hydrocarbon emissions. The ignition delay time of fuel has a strong effect on the formation of particulate matter and on the emission of unburned hydrocarbons.

Highlights

Cetane number (CN) is an empirical parameter associated with the ignition delay time of diesel fuels, which is determined by means of standard tests based on the ASTM D613 standard [1]
The effect of lowering the CN reduces the maximum pressure after top dead center (TDC), reducing the torque and the maximum temperature in the chamber, which directly affects the emissions of particulate matter (PM) and unburned HC’s
The increase in ignition delay time observed in fuels with low CN shifts the maximum pressure to angles above 20◦ after the TDC while simultaneously reducing the maximum temperature in the combustion chamber

Summary

Introduction

Cetane number (CN) is an empirical parameter associated with the ignition delay time of diesel fuels, which is determined by means of standard tests based on the ASTM D613 standard [1]. The use of high viscosity fuels hinders vaporization, favoring the formation of large diameter droplets and causing incomplete combustion due to the high penetration of the fuel jet, hindering cold starts and increasing the emission of unburned hydrocarbons (HCs) and particulate matter (PM) [9,10,11]. Fuels with low CN may increase PM emissions, since combustion begins in the final stage of the expansion cycle when the temperature inside the chamber diminishes, reducing the speed of oxidation, which in turn increases the concentration of unburned HC’s that condense on the surface, causing the mass of particulate matter to increase [9, 13,14,15]. As the cetane number increases, the temperature in the combustion chamber increases, favoring the formation of particulate matter due to thermal cracking, which in turn increases the oxidation rates and reduces the emission of unburned HC’s and the specific fuel consumption

Experimental

Results and Discussion

Conclusions