The aim of this work is to numerically verify a new model of the rotating detonation engine (RDE) combustor. The new model, which we call the hollow combustor, has no inner wall and is hollow. It is presented to solve the problem of engine heating that arises in RDEs with the co-axial annular combustor. Using the one-step chemistry kinetic model and the Euler equations in cylindrical coordinates, a series of three-dimensional (3D) numerical simulations are performed to find out whether detonation waves can propagate in such combustors. The results show that this new RDE combustor model can realize energy conversion in rotating detonation. The fuel-based specific impulse can reach around 7000 s. By comparing the results of hollow and annular combustors, some important differences are observed though general behaviors in these two RDE combustor models are similar. One is that there is no repeated reflection of shock waves in the hollow model. Another is that in the center of the cylinder part of fresh gas rolls inward into the region r < R-inner and here the RDE experiences some non-detonation burning. Also, through the comparison and analysis, roles of the outer and inner walls are presented. Without the restriction of the inner wall, burnt gas flows a little more divergently. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.