By similarity criteria an isothermal physical model of oil-firing float glass funace was set up to investigate the aerodynamics in the combustion chamber. The flow velocities in the model were measured by using three types of fire port with different burner positions and number of burners. The results show that the flow patterns and areas of recirculation are better when the burners are mounted under the port. Meanwhile the problems of model nozzle design and model making are discussed.