Research On The Acquisition & Processing Technique For The Tip-timing Vibrating Signal Of Rotating Blades

The online vibration monitoring of rotating blades is important to the safe operation ofaero-engine, electric generator and compressor. It is difficult to monitor each blade at the sametime with traditional method, accordingly in recent decades non-contact tip-timing measurementtechnique has been researched to meet the requirements of high precision and integral monitoring.The objective of our research is to develop a practical tip-timing vibration measurement prototypefor rotating blades based on the research of tip-timing measurement method. The key techniquesof the monitoring system include the following three parts: tip-timing fiber optic sensor;high-speed tip-timing vibration signal acquisition and processing system; synchronous andasynchronous vibration data processing software. The high-speed tip-timing vibration signalacquisition and processing technique plays an important role in the system. On the one hand, it isthe significant factor that determines the measurement accuracy; on the other hand, the lack ofrelevant information adds the difficulty in the research. The acquisition and processing techniquefor the tip-timing vibrating signal of rotating blades is proposed and the hardware circuit system isdesigned. In addition, the tip-clearance measurement technique is researched and the practicalsystem is devised. The vibration measurement prototype has successfully passed the field test. Theresearch work in the paper mainly includes the following six parts:1. Three types of tip-timing measurement method are proposed and the fixed frequency pulsefitting method is adopted ultimately.2. Based on the deliberate analysis of the output signal of fiber optic sensor, we designed a set oftip-timing signal optoelectronic receiving system. In order to realize the detecting of large bandfaint optical signal, the receiving and pre-processing circuit is designed based on chip SA5211 andSA5217, which are usually used in optical communication system.3. Four schemes on tip-timing pulse signal acquisition and processing circuit are designed andexperimented. The 100MHz clock oscillator is employed in the circuit to guarantee the 10nstip-timing accuracy. The first scheme is based on the 74 series integrated circuit; while other twoschemes based on FPGA have been examined in the field or laboratory test. In each scheme theEPP or ISA computer interface circuit is designed.4. The real-time vibration measurement system based on the combination of FPGA and DSP isdesigned. The schematic diagram and simulation experiment are completed.5. A set of tip-clearance measurement system is proposed. The 20MHz high-speed tip-clearancedata acquisition circuit, as well as the tip-clearance preamplification and processing circuit aredesigned and debugged.6. The synchronous vibration data analyzing method using 3~5 tip-timing sensors is introduced.