Turboprop Propeller Control for In-Flight Restart Overspeed
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Solution Overview
Problem
Turboprop engines face overspeed events during in-flight restart, which can trigger protective measures leading to undesirable thrust variations.
Innovation Solution
A method for operating a turboprop engine involves controlling the propeller based on a modified reference propeller rotational speed and/or a modified minimum propeller blade angle to maintain the actual blade angle above the aerodynamic disking angle during in-flight restart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overspeed protection systems are activated during in-flight restart, then engine safety is improved, but thrust variations and operational stability deteriorate
Solution Approach 1:
The control system applies preliminary anti-action by detecting the in-flight restart condition and proactively adjusting propeller control parameters before overspeed can occur. The system modifies the minimum propeller blade angle schedule and reference propeller rotational speed to prevent the propeller from entering the overspeed regime, thereby avoiding the need to activate overspeed protection systems that would cause thrust variations.
Solution Approach 2:
The system implements dynamics by making the propeller control parameters adaptive to the flight restart condition. The minimum propeller blade angle and reference rotational speed are dynamically adjusted based on the detected restart state, allowing the system to maintain optimal performance while preventing overspeed events during the transient restart phase.
2Adaptability or versatility
If propeller blade angle is reduced during restart, then engine restart capability is improved, but propeller overspeed risk increases
Solution Approach 1:
The control system employs feedback by continuously monitoring propeller rotational speed and blade angle during the restart process. Based on this feedback, the system adjusts the minimum propeller blade angle schedule to ensure that blade angle reductions necessary for restart do not cause the propeller to exceed safe rotational speeds. The feedback loop maintains the propeller within safe operating parameters while enabling successful restart.
Solution Approach 2:
The system applies parameter changes by modifying the control parameters (minimum propeller blade angle and reference rotational speed) specifically for the in-flight restart condition. These parameter adjustments create a modified control schedule that allows the propeller blade angle to be reduced sufficiently for restart while preventing the propeller rotational speed from exceeding design limits.
Data Source
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AI summary
A method (400) for operating an aircraft turboprop engine (100) comprises controlling (402) a propeller (120) of the turboprop engine (100) based on a selected one of a reference propeller rotational speed and a minimum propeller blade angle while the turboprop engine (100) is running; detecting an inflight restart of the turboprop engine (100); and controlling (404) the propeller (120) during the inflight restart in accordance with at least one of a modified reference propeller rotational speed and a modified minimum propeller blade angle to maintain an actual propeller blade angle above an aerodynamic disking angle (302) during the inflight restart.