Measurement of heat loss due to thermal radiation of liquid spray flames using shock tube technique

Abstract

A single-compression, “tailored” interface shock tube was used to measure thermal energy radiating from diesel combustion. The fuel (light oil) was injected through a throttle nozzle (pintle diameter: 1 mm) into air behind a reflected shock wave, 37, 78, and 120 mg of fuel were injected at pressures of 15 and 20 MPa. Monochromatic emission at wavelengths of 0.6328, 0.9, 1.1, 1.45, 2.5, 3.56, 3.92, and 4.2 μm was followed with IR-detectors at different distances from the injection nozzle. These signals were obtained simultaneously, together with pressure and nozzle lift sensor signals. In another experiment, time histories of the flame radius at diffrent distances from the injection nozzle were determined by observing light signals of near-IR detectors set radially with relation to the shock tube. Heat loss due to thermal radiation was calculated using the time histories of both monochromatic emission and the flame radius. Soot concentration profiles were also obtained using this data. Results were as follows: (1) Heat loss per injection is approximately proportional to the injection pressure. (2) Heat loss is also proportional to the amount of fuel. (3) The ratio of thermal radiation to the lower calorific value of light oil is about 5 to 10%. (4) The volume concentration of soot increases gradually near the ejection nozzle and decays rapidly. At points far from the injection nozzle, soot increases rapidly and decays gradually. The maximum volume concentration of soot is about 10 −4 cm 3 soot/cm 3 gas.