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Thermal Characteristic of Diesel with Oxygen-enhanced Combustion in Furnace

Author: DengZhenLu
Tutor: ChengJinShu
School: Wuhan University of Technology
Course: Materials Science
Keywords: Diesel Oxygen-enhanced combustion Flame characteristic thermal Characteristic
CLC: TK16
Type: Master's thesis
Year: 2011
Downloads: 85
Quote: 0
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Abstract

Oxygen-enhanced combustion technology is one of the new technologies which could not only save energy but also reduce emissions. Its advantages of speeding up the burning rate, improving combustion efficiency, decreasing energy volume, reducing exhaust emission and decreasing heat loss etc are attracting more and more attention from scholars. But studies on flame characteristic and thermal characteristic of oxygen-enhanced combustion are rare at home and abroad. So this study mainly focus on the flame characteristics of diesel with oxygen-enhanced combustion and its thermal characteristics of kiln on the simulated burning test-bed, aiming to explore the excess air coefficient and combustion air temperature of diesel combustion, looking for the influence of oxygen concentration on the reduction of energy consumption and exhaust emissions, providing technical parameters and theoretical basis for designing appropriate oxygen-enriched combustion furnace structure and high efficiency energy saving burner through theoretical calculation.In this paper, by testing the velocity and pressure of flame-thrower though anemometer, the influence of varying the excess air ratio, combustion air temperature and oxygen concentration on the velocity and pressure of flame was investigated. K and S type thermocouple and IR imager were used to analyze flame temperature alteration of combustion air temperature test and oxygen-enhanced combustion test. Flue gas analyzer was employed to measure the amount of flue gas, the concentration of NO, NO2, NOx, CO, SO2, CO2 at the end of flame, the observe window and smoke-exhaust pipe, etc, to support data of whether it was a completely combustion. And the effect of different oxygen concentration on theoretical flame temperature, flame emissivity, energy efficiency was theoretically studied.The results showed that the regularity of flame temperature was increased at the beginning and then decreased as the excess air ratio was increasing from 1.00 to 1.20. When excess air ratio was 1.00, diesel was obviously incompletely burned and when excess air ratio was 1.10, the volume concentration of CO was 81ppm. The increasing of combustion air temperature leads to the increasing of combustion efficiency, flame temperature and the decreasing of diesel and theory combustion air volume. The formation of NOX was not obvious mainly because the combustion air temperature was not preheated high enough.In diesel oxygen-enhanced combustion, in order to keep the temperature field stable, with oxygen concentration increasing from 21% to 30%, the temperature of hot gas along axis of flame was decreased rapidly when the distance to the kiln wall was increasing. The velocity and pressure of flame-thrower were both decreased and this lead to the shorter of flame length, the rapider of flame flow rate and the shorter of flame coverage. The consumption volume of diesel was obviously decreased at the beginning of increasing oxygen concentration, almost 33.3% diesel volume was decreased when oxygen concentration was increased from 21% to 24%, but this ratio slowed down when oxygen concentration was further increased. The volume of supporting air and theory flue gas and the concentration of CO2 was decreased with the increasing of oxygen concentration, but the concentration of NOX was increased rapidly, and also the variety of CO and SO2 was not clear.In theoretical calculation of diesel with oxygen-enhanced combustion, higher oxygen concentration led to higher theoretical temperature, and when oxygen concentration was increased to 30%, the theoretical temperature was higher than 2500℃. Additionally, stronger flame blackness was achieved because of the high concentration of CO2 and H2O, when oxygen concentration was 30%, the sum concentration of CO2 and H2O was higher than 33%, which led to the stronger emissivity of flame. What’s more, thermal efficiency was increased with the increas-ing of oxygen concentration, and when oxygen concentration was 30%, it was 51.4%.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Fuel and combustion
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