<p>A pulse combustion device (26) comprises a circular array of combustion conduits (30). Each conduit (30) has an inlet (36) and outlet (38). An inlet valve admits a gas to the inlet (36). An outlet member (60) is provided with a passageway (66) which directs combustion gases from one or more conduits (30) to one or more other conduits (30) to initiate combustion in said conduits as the array and the outlet member (60) rotate relative to each other.</p>
