JetEngineVibratinAnalysis：喷气发动机的振动分析.doc

Shing Chi Chan December 2009 - February 2010Laboratory Work Jet Engine Vibration Analysis For the vibrations project，there are two possible engines which could be used to extract data. The mini-turbine produces significant vibration, but this is mainly due to the turbo machinery - the compressor and the turbine，not the combustion or pressure fluctuations produced by the gas exhaust flow. The combustion chamber has no such turbo machinery, but has much less vibration. These two options will be weighed to decide the future of the vibration project. Figure 1: Combustion Chamber Figure 2: Mini-turbine Jet Engine The current progress of vibration studies include but not limit to perform proper measurements on the mini-turbine engine with a single axial accelerometer. The accelerometer is mounted perpendicular to the radial surface of the engine chamber. Due to its high rotating machinery, a significant amount of vibration data is obtained from the mini-turbine. While measurements are performed by SignalExpress，there are factors affecting the results and often times delay the process. The limitation of the default data acquisition device or DAQ with its USB form factor doesn’t permit a sampling rate of more than 48kHz. To recall from the Nyquist theory, the sampling rate has to be twice or higher than the signal rate，i.e. a signal rate of less than 24kHz is anticipated in our case. Due to high amount of vibration generated by the Miniturbine engine, the sampling rate is optimally maintained at 100kHz in order to have a 50kHz SPAN of the frequency spectrum. Not to mention that the DAQ can’t hold higher sampling rate than 48kHz，with such high sampling rate a significant amount of data is transferred from the DAQ to the PC computer. Apparently the USB connection fails to provide a steady data transmission upon a high amount of high frequency data. Often time in the measurements，the problem of buffer overflow occurs and halts the measurement. Such limitations cannot be tole