It is significant that the flow field has been visualized accurately for understanding and controlling it within a round nozzle

and the accurate visualization can validate the results of numerical calculation. Therefore

firstly

reduction of effective view field from image distortion because of the thickness of round nozzle was revised. Cylindrical lens were added outside round nozzle for calibrating distortion. Design of the cylindrical lens was introduced to calculate the foci of thickness lens and optimize it by ZEMAX software. Static state experiments indicate that the effective view field is increased from less than 30% to more than 80%. Secondly

it was supposed the refractive index as 1 and the spreading ray as parallel ray within round nozzle during calibrating design. Analysis indicates the effect of these supposes is small for some flow fields of high-temperature and high-pressure. Thirdly

the feasible methods for flow field visualization were analyzed

and the dynamic results were given. At last

feasibility of the calibration method and the limitation to quantitative interferometry were pointed out. The research is of reference signification to flow field of combustion in round nozzle.