Engine torque Flashcards
Why is it necessary to measure engine torque in turboshaft engines?
It is necessary because turbine gas temperature and engine RPM alone do not accurately estimate the power being produced. Torque meters are used to measure the torque delivered to the rotor or propeller.
What is the function of the torque meter assembly in an electrical torque meter system?
The torque meter assembly measures the twist in the inner shaft, which is proportional to the torque being delivered to the gearbox.
What are the two types of torque meters used in turboshaft installations?
The two types of torque meters are electrical torque meters and hydraulic torque meters.
What are the main components of a typical electrical torque meter system?
A typical electrical torque meter system consists of a torque meter assembly, a phase detector, and an indicator.
Describe the construction of the torque meter assembly.
The torque meter assembly consists of two concentric shafts: the inner shaft connects the drive from the engine to the gearbox, and the outer datum shaft is connected only to the engine output. Both shafts have toothed gear wheels with pick-up assemblies above them.
How is the Electromotive Force (EMF) generated in an electrical torque meter system?
EMF is generated as the gear teeth on the exciter wheels cut the magnetic lines of flux around the magnet, inducing EMF in the windings of the pick-up coil.
What happens in the torque meter system under no-load conditions?
Under no-load conditions, the toothed wheels on both shafts turn with no relative movement between them, resulting in no difference in the output signals from the pick-ups.
How does the electrical torque meter detect torque?
As torque is applied, the inner drive shaft twists, creating an angular displacement relative to the outer datum shaft. This displacement is detected by the pick-up assembly as a phase difference in the output signal.
How does a hydraulic torque meter operate?
A hydraulic torque meter operates using engine oil pressure metered through a valve controlled by a helical ring gear, which moves in response to the applied torque.
What role does the phase comparator play in the electrical torque meter system?
The phase comparator generates a signal based on the phase difference, which drives the pilot’s indicator to display the torque measurement.
What is the purpose of the helical ring gear in a hydraulic torque meter?
The helical ring gear moves against a piston, controlling the opening of a valve that regulates oil pressure flow, making the oil pressure proportional to the torque applied at the propeller shaft.
How is the oil pressure in a hydraulic torque meter converted into a readable signal?
The oil pressure is transferred into an electrical signal by a transducer, which is then read by the flight deck instrument.
In what units is torque typically displayed in the flight deck?
Torque is typically displayed in lb/ft of torque or as a percentage of horsepower.
Why is calibration of the torque meter important?
Calibration is important to ensure the accuracy of the torque meter, as it is used to set power settings critical to engine performance.
