An IFA300 constant temperature anemometer system is adopted to perform cold air experiments on a scale model of a dual circle tangential firing single furnace ultra supercritical boiler to investigate the causes and influencing factors of jet deviation in the furnace, which is the main cause of the elliptical aerodynamic field. The elliptic aerodynamic field could cause heat imbalance in the burner zone, in which case high temperature corrosion and slagging might happen on the high-temperature furnace wall. Theoretical derivations and analysis have been carried out before any experimental studies, and an equation determining the influencing factors of the jet deviation has been established. The experimental results agree well with the equation. The jet deviation becomes more problematic when the velocity ratio of the impacting jet and the impacted jet increases from 0.85 to 1.30. A reduction in the distance from the impacting position to the root of the impacted jet also increases the jet deviation as well as the angle between the impacting jet and impacted jet. The results of the theoretical analysis and experiments provide some transformations within the boiler that could be adopted to avoid the formation of the oblique ellipse flow field. (C) 2012 Elsevier Ltd. All rights reserved.