Structural Dynamic Design of a Rotating Hydrogen Co-Fired Multi-Fuel External Combustor

In the paper the authors will present the design and preliminary rotor-bearing dynamics test results for a hydrogen co-fired multi-fuel capable rotary burner. Hydrogen co-firing involves moving a stream of liquid or gaseous fuel through a zone of combusting hydrogen. The high-temperature of the hydrogen combustion zone initiates a vigorous combustion of the fuel stream moving through. Given the very high combustion temperatures of the rotating hydrogen flame fronts and close proximity of the rotating flame holder to the structural support, an integrated high temperature drive and bearing system was necessary to achieve reliable long term operation. Design space constraints for the rotary hydrogen burner head resulted in a drive and bearing system design that includes 150 mm diameter compliant foil journal bearing supports and an air driven reaction turbine closely integrated with the thrust foil bearings. Drive turbine design, rotor-bearing system dynamic tradeoffs and thermal management in the presence of high axial thermal gradients will be presented along with preliminary testing to design speeds of 7500 rpm (i.e, surface velocity of 100 m/s) under simulated thermal gradients with the rotating assembly face temperature reaching as high as 800°C.