سال انتشار: ۱۳۸۶
محل انتشار: پنجمین همایش موتورهای درونسوز
تعداد صفحات: ۲۳
Vahid Hosseini – Mechanical Engineering Department, University of Alberta, Edmonton, Canada
M David Checkel – Mechanical Engineering Department, University of Alberta, Edmonton, Canada
differing ignition properties than the base fuel. Reformer gas (RG) is a mixture of light gases dominated by hydrogen and carbon monoxide that can be produced from base hydrocarbon fuels by several reforming techniques such as partial oxidation, autothermal or steam reforming. In a series of experimental studies, reformer gas was used to control combustion timing using a CFR engine and various base fuels: compressed natural gas (gas, high octane), iso-octane (liquid, high octane) and n-heptane (liquid, low octane). The effects of reformer gas on engine operating parameters and combustion characteristics were shown to differ for different base fuel. Keeping other influential parameters constant, increasing RG mass fraction in a natural gas mixture advanced combustion timing and shifted the operating range of the engine toward leaner mixtures. This enabled the natural gas-fueled HCCI engine to operate at leaner mixtures with decreased knock intensity and smoother combustion behavior. For iso-octane and n-heptane base fuels, combustion timing was retarded significantly as RG blend fraction increased. For the case of isooctane the operating region did not change. However, for the n-heptane base fuel, the operating
range was shifted toward richer mixtures, enabling higher indicated power and thermal efficiency. A chemical kinetic study of n-heptane / RG ignition showed that the influence of hydrogen was to suppress the first stage combustion and decrease the radical concentration after first stage combustion, thus delaying the main stage combustion, (despite faster major reaction rates during the main combustion period).