Ignition delay time of diluted iso-octane/Air mixtures were measured in a single pulse reflected shock tube. In this work, the onset of ignition was determined by monitoring both the pressure history and the emitted light corresponding to OH* emission. The photomultiplier tube (PMT) in specially designed housing at CaF2 window were used with 310±5nm filters to measure the ultraviolet OH* emission. Experiments were performed at temperatures between 1295K and 2487K, pressures about 1 atm. and varying equivalence ratios (Φ;=0.25, 0.5, 1.0, 2.0). Long shock tube dwell time (about 15ms) was achieved by tailored contact surface operation under such conditions. To simulate real engine environment, liquid fuel aerosol was generated by the supersonic atomizer, and the size of fuel droplet in aerosol was measured. Both pressure and OH*emission histories were obtained to determine the ignition delay time and the relative strength of the ignition process. The OH* emission time history data showed that there were different behaviors of iso-octane in ignition process under varying temperatures. Several potential chemical kinetics mechanisms were used to simulated iso-octane autoignition under the same conditions. Analysis of the experiments results and simulations supported the validation of those chemical kinetics mechanisms. The experimental data was consistent with the prediction of mechanism in low temperatures and the experiment data showed that the factors of temperature and equivalent ratio have different effect on the ignition delay time
Planar Laser-Induced Fluorescence (PLIF) technique, which is a non-intrusive, fast-response diagnostic method, has been widely used in measurement of various complex flow fields. Both cold flowfield[1-4] and combustion flowfield have made use of PLIF for diagnosis. According to the different flow field and investigation objects, parameters such as fluorescence tracer molecule, laser wavelength, and so forth should be selected seriously in order to obtain the information concerned. This technique was used to investigate complicated flow structure of mixing between transverse jet and supersonic flow, in which acetone and OH radicals were chosen as the fluorescence tracer molecules in the experiments of cold flow and combustion flow respectively. During cold flow measurements, air was used as both the transverse jet and supersonic flow, and liquid acetone was gasfied before adding into the transverse jet, which was excited by laser sheet of 266nm. During combustion flow measurement, ethylene was used as the transverse fuel jet, and combustion between air and ethylene was sustained by plasma discharge. Laser sheet of 283nm was used excite the intermediate product of OH radicals. Fluorescence images were recorded by the intensified CCD camera after filtering interfere light. Both results show that PLIF displays as a credible and valid method for investigating complicated cold flowfield and combustion structure, so long as chosing appropriate fluorescence tracer molecule, laser exciting wavelength, optical filter, et al.