Abstract
An aerosol shock tube has been developed for measuring the ignition delay times (tig) of aerosol mixtures of low-vapor-pressure fuels and for visualization of the auto-ignition flow-field. The aerosol mixture was formed in a premixing tank through an atomizing nozzle. Condensation and adsorption of suspended droplets were not observed significantly in the premixing tank and test section. A particle size analyzer was used to measure the Sauter mean diameter (SMD) of the aerosol droplets. Three pressure sensors and a photomultiplier were used to detect local pressure and OH emission respectively. Intensified charge-coupled device cameras were used to capture sequential images of the auto-ignition flow-field. The results indicated that stable and uniform aerosol could be obtained by this kind of atomizing method and gas distribution system. The averaged SMD for droplets of toluene ranged from 2 to 5 μ m at pressures of 0.14–0.19 MPa of dilute gases. In the case of a stoichiometric mixture of toluene/O2/N2, ignition delay times ranged from 77 to 1330 μs at pressures of 0.1–0.3 MPa, temperatures of 1432–1716 K and equivalence ratios of 0.5–1.5. The logarithm of ignition delay times was approximately linearly correlated to 1000/T. In contrast to the reference data, ignition delay times of aerosol toluene/O2/N2 were generally larger. Sequential images of auto-ignition flow-field showed the features of flame from generation to propagation.
Highlights
A wide range of pressures and temperatures can be produced by the static airflow behind the reflected shock wave, so that the ignition phenomena of gas, liquid and nano-solid fuels can be studied in shock tubes
Results of Sauter mean diameter (SMD) measurement for toluene droplets at different P0 are shown in Figure 4b, where the cross point the measurement averaged value a singledroplets measurement and the solid square point is4b, thewhere total
The results showed that the SMD of droplets changed when P0
Summary
A wide range of pressures and temperatures can be produced by the static airflow behind the reflected shock wave, so that the ignition phenomena of gas, liquid and nano-solid fuels can be studied in shock tubes. Brezinsky’s group built high-pressure shock tubes [2,3] for the study of high-temperature decomposition, oxidation mechanisms of hydrocarbon fuels. This kind of shock tube uses a single (or double) diaphragm, which is suitable for studying the gas phase reaction at high temperatures (up to 2000 K) and ultra-high pressures (up to 100 MPa), and the test time is usually 0.5–2 ms. The saturated vapor pressures of JP-7 and n-dodecane are less than 133.3 Pa, and the high equivalence ratio requires
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