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Rotor-stator axial clearance plays a pivotal role in ensuring the safety and efficiency of major rotating machinery. This paper introduces an innovative clearance measurement method based on wavelength division multiplexing (WDM) combined with all-fiber microwave photonic mixing. The method is distinguished by large measurement range, high accuracy and low drift. The WDM-based common optical path structure is established. A comprehensive theoretical model of axial clearance drift determined by wavelength and temperature is developed based on the thermo-optic effect of optical fiber material. To efficiently separate measurement and reference light at the probe, the optical design for a compact optical bandpass filter (OBPF) fiber sensor probe is proposed. The performance of the method is substantiated by simulations and experiments. The results demonstrate an accuracy of better than 2.8µm over a 23.5 mm range, surpassing existing methods. The method's capability to mitigate temperature-induced drift is further confirmed through high-temperature drift and comparative experiments.
RESUMEN
A robust five-degree-of-freedom (5-DOF) measurement system is proposed in this paper. The compact optical configuration with high resolution is designed based on lens combination and multiple reflections. Beam drift and dual-beam parallelism are monitored and compensated by autocollimator units and a polarizer unit respectively. In addition, a protection method is proposed to reduce the intensity of air turbulence by reducing the Reynolds number of the beam path. The performance of the system is verified by experiments. The experimental results show that the self-compensation methods and air turbulence protection can effectively improve the accuracy and stability of the system under the long-term interference of external environments. The proposed system has high precision, desirable robustness, and convenient pre-calibration, which can be used for error measurement of precision machines.
RESUMEN
In this paper, a high-accuracy measurement method for rotor-stator axial clearance in narrow spaces is proposed. The optical path structure based on all-fiber microwave photonic mixing is established. To improve the accuracy and expand the measurement range, the total coupling efficiency over the entire measurement range at different working distances of fiber probe was evaluated by Zemax analysis tool and theoretical model. The performance of the system was verified by experiments. The experimental results show that the measurement accuracy of axial clearance is better than 10.5 um within the range of 0.5-20.5 mm. The measurement accuracy has been effectively improved compared to previous methods. Additionally, the probe size is reduced to a mere diameter of 2.78 mm, which is more suitable for axial clearance measurement in narrow spaces inside rotating machines.
RESUMEN
Rotor-stator axial clearance is a crucial design parameter affecting rotating machines' efficiency and safety. To accurately measure the dynamic axial clearance in high-speed machinery, a precise method based on time division multiplexing with frequency domain interferometry has been proposed. This method has proven robust and accurate through simulations and experiments. The inclusion of an optical switch enables the utilization of dispersive interferometry(DPI) and time division multiplexing for multiple channels of the light source. It achieves a static accuracy of 1.5â µm for a 15 mm range and a dynamic accuracy of 9â µm at 3000â rpm.
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In the domain of frequency sweeping interferometry, the accurate extraction of distance information from nonlinear frequency scanning signals holds paramount significance in ensuring meticulous measurements of high precision. This paper presents a novel, to the best of our knowledge, high-speed distance extraction algorithm based on the table lookup method and validates its feasibility through theoretical models, simulations, and practical experiments. The proposed algorithm achieves comparable accuracy to traditional methods involving resampling and Hilbert transform. However, it outperforms them in robustness against noise and variations in sampling points. This method can accurately process signals sampled even below the Nyquist sampling rate. The simplicity and computational efficiency of the proposed approach make it suitable for various nonlinear sampling applications, promising broad applicability in scientific and engineering contexts.
RESUMEN
In recent years, there has been a notable increase in cooling water intake blockage caused by marine organism blooms at coastal nuclear power plants worldwide, resulting in shutdowns of nuclear power plants and large economic losses. A sizable portion of these incidents were caused by blooms from jellyfish, a planktonic invertebrate with a unique growth pattern. Suitable external conditions are conducive to the rapid growth of jellyfish, and blooms can occur within a few days. In order to better predict jellyfish bloom and enable nuclear power plants to prepare for it in advance, this study explores the numerical relationship between jellyfish biomass and environmental parameters. A series of time windows (evaluation intervals) were defined and constructed by a time-series recursive approach, which solved the problem of poor correlation between jellyfish biomass and environmental parameters at non-bloom points. The optimal time window length D = 10 was obtained, and the key environmental parameters affecting jellyfish biomass were screened as sea surface temperature, salinity, voltage value, dissolved oxygen, and chlorophyll. According to the ADF and KPSS tests, the key parameters have no significant time dependence, which ensures the stability and reliability of the subsequent predictions. The jellyfish bloom prediction model was derived by calculating the score F through the recursive Principal Component Analysis of the key environmental parameter in the time interval preceding the prediction point. The sudden change moments of score F correspond well to the jellyfish bloom moments, and the sudden change moments are all advanced for a period of time compared to the bloom time, which can provide valuable time for the nuclear power plant to organize manpower to deal with the blockage. Finally, a maximum score F threshold model was proposed to be coupled with the jellyfish bloom prediction model to provide a more robust basis for early warning of jellyfish at nuclear power plants.
RESUMEN
The time-resolved polarized fluorescence of oriented R-phycoerythrin single crystal from red alga Porphyra yezoensis was studied in picosecond time scale. The fluorescence decay of the crystal exhibited two exponential processes, one of which was related to the energy transfer and excitation equilibrium between chromophores (tau(1)