Characteristics of partially premixed turbulent flames are investigated using a burner design that allows for a variation in the level of premixing between fuel and air. In this study, initially nonpremixed flames with a coaxial injection of air at variable positions are considered. Velocity and mixing characteristics of coannular streams have been measured, which show a region of enhanced turbulence and mixing in the shear region, and also indicate an increased partial premixing with increasing inner tube recess (Delta x/D-i). The ratio of the inner and outer jet velocities (flow rates) affects the flame characteristics, as the overall fuel-air ratio increases with an increase in the inner jet velocity. Inner jet air also assists in entrainment of surrounding air. These effects lead to a decrease in the flame height as the ratio of the inner and outer jet velocities increases. Through enhanced fuel-air mixing via inner tube traverse, flame radiation decreases with increasing Delta x/D-i; however, a similar change in Delta x/D-i has a miner effect on the dame height. The lift-off height has a linear dependence on the velocity ratio (U-i/U-0), while the slope becomes smaller with increasing Delta x/D-i. Flame stability characteristics have also been obtained, which indicates that the region of stable flame operation is extended when Delta x/D-i is increased beyond a certain limiting value. These observations suggest a method of controlling both the flame length and flame stability via variations-of U-i/U-0 and Delta x/D-i, respectively.