The relationship between the rotational speed and the acceleration spectrum of each rotational speed corresponding to each measuring point can also be found that the first peak frequency of each spectrogram increases proportionally with the increase of the rotational speed. The frequency value is basically consistent with the working frequency of the engine, the working frequency of the compressor, and the 0.5 times working frequency of the generator. It can be seen that the torque fluctuation of the engine, the axial turbulence of the generator, and the axial turbulence of the compressor with the change of the speed of the Chongqing University Journal are the possible sources of system resonance.
In order to determine the contribution of the three sources, this paper designed a further separation experiment: 1) First remove the compressor belt, so that the compressor does not work, and basically does not affect the structural dynamic characteristics of the system. 2) On the basis of the above, the crankshaft water pump belt is replaced, so that the generator does not work, and the pump works normally, and the dynamic characteristics of the system structure remain basically unchanged without affecting the engine cooling. After the compressor belt is removed, the vibration characteristics of the system are substantially unchanged, demonstrating that the compressor is not the primary source of vibration for the system. The replacement of the crankshaft water pump belt, because of the need for a special belt, which is not realistic in the sample and tooling, so the separation experiment failed. However, for the torque fluctuation of the crankshaft, there are two possible transmission routes. One is directly transmitted to the generator compressor system via the belt through the crankshaft pulley, but the transmission efficiency of the route is very low considering the vibration absorption effect of the rubber belt itself; It is transmitted to the engine body through the support point of the crank-link mechanism, and finally transmitted to the system to excite the vibration of the system. Therefore, the torque fluctuation of the engine itself may be an excitation source for the vibration of the system. For the generator, due to the obvious lateral turbulence, the measured turbulence is generally 0.15 ~ 0.30mm (while the foreign generator's turbulence is less than 0.10mm), and the excitation caused by the turbulence directly acts on the system itself. Therefore, it can be concluded that the excitation caused by the turbulence is the most important source of excitation for the system. In summary, the generator is the main source of vibration for the system. In addition, the torque fluctuation of the engine is another source of vibration for the system.