Session: 06-03 Pressure gain combustion and propulsion cycles I

Submission Number: 179283

Design and Experimental Validation of a 3 kW Small-Scale Axial Turbine for Power
Extraction From a Rotating Detonation Engine 

The complete design, experimentation, and validation approach of a small-scale single-stage axial turbine system is detailed for use in the unsteady and varying exhaust of a Rotation Detonation Engine with a power target of 3kW. Rotating Detonation Engines are a novel implementation of Pressure Gain Combustion (PGC), which features one or more detonation waves traveling circumferentially around an annular chamber. Implementation of a Rotating Detonation Engine coupled with a turbine allows for a considerable power advantage of the Humphrey cycle (constant volume) over the standard Brayton Cycle (constant pressure). With the increased power advantage of the Humphrey cycle comes the additional challenges of increased heat and unsteady flows created from a rotating detonation wave. The stator and rotor are designed specifically to address these challenges with emphasis on promoting boundary layer attachment to all surfaces. The turbine design started with a 0-dimensional (0-D), isentropic model to quantify flow parameters at each station and to find the overall power and torque provided in an ideal system. TurboDesign, a blade generation software, was utilized to create the blade geometries for the stator and rotor. The stator and rotor contain 5.17mm blade heights with a constant diameter annulus across the stage. Stator flow turning angles turn the flow to 29 degrees in the absolute frame of reference. The stage has a design operating speed of 30,000 RPM. To validate our 0-D model, ADS CFD was employed to compare and estimate efficiencies and to visualize flow behavior across the stage. The turbine system will be integrated with an in-house doublet-injected Methane-Gaseous Oxygen test-bed RDE manufactured and validated prior to turbine experimentation. The RDE Annulus’ outer diameter is 37mm, with a propellant flow rate of 90 g/s, a mass-averaged exit temperature and pressure of 2000K and 5 bar, respectively. The turbine unit was designed with static pressure and temperature sensors distributed along the flow path (before and after the stator and rotor) to determine efficiency, and compared to a CFD model using MetaComp’s ICFD++. A torque sensor and starter generator are coupled to the rear of the turbine to experimentally determine torque and power. The efficiency is determined by both the pressure ratio and the temperature - RDEs are uniquely positioned to increase the pressure ratio entering the turbine over conventional combustion methods. 

Presenting Author: Lucas Nicol North Carolina State University at Raleigh

Presenting Author Biography: Lucas Nicol is a graduate researcher in the Department of Mechanical and Aerospace Engineering at North Carolina State University, working within the BEFAST Lab. His research focuses on rotating detonation engines (RDEs) and turbomachinery power extraction, with emphasis on clustered RDE geometries, unsteady turbine design, and experimental design and validation of pressure gain combustion systems.

Authors:

Lucas Nicol North Carolina State University at Raleigh
Nathaniel Michnoff North Carolina State University at Raleigh
Trevor Larsen Purdue University
Eduardo Leite De Moraes North Carolina State University at Raleigh
James Braun North Carolina State University at Raleigh