Air Force Phase II SBIR – Tigershark UAV Baker Heavy Fuel Rotary Demonstrator – Flight Test

Solution

As part of a larger Air Force Research Lab (AFRL) SBIR contract to demonstrate the benefit of improved turbo/superchargers for unmanned aircraft, Baker Engineering developed and demonstrated a turbocharged direct injected heavy fuel rotary engine in flight tests. This engine, dubbed the Baker Heavy Fuel Rotary Demonstrator (BHFRD) is a highly advanced heavy-fuel rotary engine with a large number of SBIR developed technologies integrated into the engine; The culmination of years of research in technology to support heavy fuel combustion in rotary engine applications. While the geometry is based on the spark ignited, gasoline UEL AR741 rotary engine, the BHFRD features a bespoke liquid cooled housing with an air cooled rotor. The following Baker Engineering developed enabling technologies were utilized in the design of the propulsion system, all supported by current or prior SBIR development efforts:

• Micro high pressure fuel pump and drive
• Compact passively regulated fuel rail
• Compact solenoid actuated common rail injectors
• Integrated pump drive
• Compact three stage oil pump with integrated regulator and filter
• Light weight turbocharger with performance matched turbine housing and cold side boost control (no wastegate)
• Advanced coatings, seal material, induction system and cooling system design

Baker Engineering completed system integration of the BHFRD propulsion system on a RQ-23A Tigershark UAS, replacing a Herbrandson Dyad 370 engine. The BHFRD was demonstrated in a successful flight test at Yuma Proving Grounds under hot and humid conditions with temperatures on the ground exceeding 110°F. While flight time was limited, the packaging, integration and testing of the BHFRD provided valuable insight into the performance potential of a heavy-fuel rotary engine for flight applications. Baker Engineering continues to pursue development of heavy-fuel rotary engines as a power dense and lightweight power source for defense applications. During this effort, the following milestones and lessons were achieved:

• Successful development, integration and operation of the 34hp turbocharged, dry sump, liquid cooled BHFRD on the Tirgershark UAS platform
• First flight test of a turbocharged, direct injection, heavy-fuel rotary engine
• Improved take-off and climb performance of the turbocharged BHFRD at 4,400 feet Density Altitude over the naturally aspirated Herbrandson 370
• Heat Exchanger Performance – Thermal management system maintained coolant temperatures below limits when idling on the runway at ambient temperatures up to 114°F, a typical problem point with air cooled UAV engines