Recently, an annular-stepwise-diverging-tube (ASDT) was developed to investigate the length-scale effects on the flame propagation velocity (FPV), and the overall FPV of a specific fuel was described as a continuous surface in the physical domain of the concentration-length-velocity. In this study, the ASDT burner was improved in three aspects. First, all flame images taken during the experiment were analyzed to improve the experimental resolution and reliability. Second, an appropriate condition for the flow rate reduction was determined. Third, the thickness of the step-unit was reduced from 10 mm to 3 mm. Precise FPV values depending on the length-scale could be obtained using a compact ASDT burner. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.