Abstract
Planer laser induced fluorescence (PLIF) of toluene and acetone is performed for visualization of spatial distribution of oxygen in gas and oxygen mixing region in the nozzle flow field. The principle of the calibration methods of oxygen concentration distribution are expounded in this paper. As the two tracers had different situations on oxygen quenching effect, the ratio of the fluorescence images of the two tracers could be used to measure the oxygen concentration in the mixed area. In this way, the ratio of fluorescence signal intensity of toluene to acetone was found to be linearly related to oxygen concentration. By using this calibration relationship, we can measure the oxygen concentration distribution of the nozzle flow field with an accuracy of 12.6%. It indicates that this measurement method can be applied in turbulent flow field. The variation trend of oxygen concentration distribution in nozzle flow field can be analyzed by capturing multiple PLIF images in time sequence, which has the important reference value to the development process of nozzle burner flame.
Highlights
The nozzles have many advantages such as simple structure, easy processing, low investment cost, simple operation, and easy maintenance
As nitrogen has a negligible effect on toluene and acetone fluorescence signal, it is very suitable as a diluent gas of tracer vapor
Our results show that oxygen quenching has a vastly different effect on the fluorescence signal from two kinds of tracer, and experiments substantiate the feasibility of this research method
Summary
The nozzles have many advantages such as simple structure, easy processing, low investment cost, simple operation, and easy maintenance. The other adopts a method to monitor the ratio of fluorescence intensity of the toluene and 3-pentanone to measure the oxygen concentration, resulting from the difference of fluorescence intensity of two tracers being quenched by oxygen [17] This method is more suitable for the test of the nozzle flow field in the long term and avoids the temperature variation in the flow field effectively. Toluene and acetone are diluted into high-purity nitrogen to form the experimental gas, which is injected directly into the air environment to form the nozzle flow field and measure the oxygen concentration distribution in this process. Compared with other PLIF flow field diagnostic tracer, the greatest advantage of the acetone and toluene for PLIF imaging is that they can be excited at a single wavelength and the peak areas of their fluorescence spectrum are distinguishable, making it easy to use specific filters for simultaneous signal acquisition
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