The Danfoss Motor says that engine vibration is an important indicator of the quality of engine work. Excessive vibration accelerates the fatigue damage of the machine and reduces the working life of the engine. Engine vibrations are transmitted to the aircraft, which can make the occupants fatigue and uncomfortable, affecting the accuracy and indication of the instrument, and sometimes causing structural and instrument damage. Therefore, there is a strict regulation on the vibration size of each engine.
The vibration of a gas turbine engine mainly comes from the rotor (ie, the compressor and the turbine rotor), the combustion chamber, and the conveyor. The causes of vibration are:
1 Rotor unbalance: The centrifugal force generated by the rotor imbalance during high-speed rotation will excite lateral vibration perpendicular to the shaft, the frequency of which is equal to the rotor speed. It is the main source of engine vibration.
2 Rotor resonance: When the rotor speed reaches a certain value, the forced vibration frequency caused by the rotor imbalance will be coupled with the natural frequency of the rotor. At this time, strong vibration will occur, and the vibration center shaft has large displacement and bending. The rotor will be scratched and the blade will be damaged. The speed at which strong vibrations occur is called the critical speed.
3 Airflow instability and pulsation: the surge of the compressor and the unstable combustion in the combustion chamber cause low-frequency longitudinal vibration of the whole machine. The entry of unstable outside airflow, or the pillars, blades, etc. in the intake passage, will cause the airflow to pulsate, thereby arousing lateral vibration or local vibration of the engine.
4 The vibration generated by the gear transmission in the transmission 不 is not smooth.
The main measure to reduce the vibration caused by the rotor is to carefully balance the rotor (static balance and dynamic balance) during ... Читать далее