Combustor device having a twin-shell tubular casing including: an inner tubular member which extends roughly coaxial a longitudinal axis of the combustor device, delimits the combustion chamber and surrounds the burner; and an outer tubular housing which extends roughly coaxial outside of the inner tubular member. An intermediate supporting structure includes an outer annular supporting member, an inner annular supporting member, and a series of three or more oblong connecting beams angularly staggered about the longitudinal axis of combustor device in cantilever manner to stably connect the inner and outer annular supporting members.