Clean and green hydraulic component solutions open the door to tomorrow’s open rotor aircraft engines
Under the Clean Sky initiative, Europe seeks to advance the maturity of the open rotor engine as a possible successor to the turbofan engine used in today’s civil airliners. Key to its safety and viability is precise control of the pitch on each of its multiple blades. The EU-funded ORPASV project sought to advance the state of the art in blade pitch control using electrohydraulic actuation. The ORPASV team developed electrohydraulic servovalves needed for the pitch actuation system architecture as part of the Sustainable and Green Engine (SAGE) demonstration project. SAGE aims at designing, manufacturing and testing a counter-rotating open rotor (CROR) demonstrator. The CROR engine architecture is a challenge for the pitch actuation system, and especially the performance requirements associated with high flow levels to actuate each blade’s pitch. Specifically, project partners developed electrohydraulic servovalve demonstrator engine prototypes to equip the CROR demonstrator for engine testing. They successfully addressed several technical challenges. These mainly include high flow levels, fluid used with high viscosity and high viscosity variation with temperature, and long-duration vibration testing beyond current aerospace standards. Scientists also developed and demonstrated an electrohydraulic servovalve engine prototype with optimised technologies based on the requirements of an open rotor target engine specification to minimise servovalve envelope and weight. They demonstrated the improved performance of target engine servovalves concerning weight savings, low internal leakage and dynamic operation. There is still a long road ahead for next-generation airliners, and absolute confidence will be needed before any change is made in existing architectures. However, ORPASV paved the way for newly designed servovalves to reach a high technology readiness level so they can be selected for further development.
Keywords
Open rotor engine, blade pitch control, ORPASV, electrohydraulic servovalves, pitch actuation
