Digital image correlation (DIC) is a material displacement and strain measurement technology based on visible light illumination. At high temperatures, the problem of thermal radiation seriously affects the quality of acquired images and restricts the development of high-temperature DIC technology which is increasingly applied in the field of high-temperature measurement due to stringent measurement temperature requirements. A thermal radiation elimination method based on the use of a polarization camera for high-temperature DIC measurements is proposed in this study. This method uses a polarization camera combined with a filter set to achieve clear image acquisition at 1200 °C and effectively eliminates the effects of thermal radiation on image acquisition. The gray average method and an image inverse filtering algorithm are adopted in this study to eliminate high-temperature thermal disturbances. Finally, a high-temperature DIC measurement system is independently designed, and a rigid-body displacement experiment is carried out on an FV566 steel specimen to obtain time–displacement curves. A set of uniaxial tensile tests is also performed on FV566 steel material to explore its strain field at 1200 °C.

Digital image correlation (DIC) technology is an optical measurement method of material strain displacement based on visible light illumination. With the increasing application of DIC technology in the field of high-temperature measurement, however, the effect of thermal disturbance on measurement accuracy becomes more and more serious. To solve this problem, a method to eliminate thermal disturbance in material measurements based on projection speckle is proposed. First, the gray surface information of two different colors is assigned to the surface of the test piece by artificial splashing and projector projection. The pictures are collected using a color camera, and the channels are separated for each frame of the picture. After that, the displacement field recorded by different channels can be obtained by DIC calculation so the thermal disturbance error can be separated from the real displacement and eliminated. Subsequently, an experimental system is built. Finally, the corrected results are compared with the true displacement value of the stage. The results show that the two sets of values are highly consistent, which verifies the feasibility and accuracy of the proposed method.

A pressure pulsation experiment of a dishwasher pump with a passive rotation double-tongue volute was carried out and compared with the pressure pulsation of a single-tongue volute and a static double-tongue volute. The pressure pulsation of the three volute models was compared and analyzed from two aspects of different impeller speeds and different monitoring points. The frequency domain and time–frequency domain of pressure pulsation were obtained by a Fourier transform and short-time Fourier transform, respectively. The results showed that the average pressure of each monitoring point on the rotating double-tongue volute was the smallest and that on the single-tongue volute was the largest. When the impeller rotates at 3000 rpm, there were eight peaks and valleys in the pressure pulsation time domain curve of the single-tongue volute, while the double-tongue volute was twice that of the single-tongue volute. Under different impeller speeds, the changing trends of pressure pulsation time and frequency domain curves of static and rotating double-tongue volutes at monitoring point p1 are basically the same. Therefore, a volute reference scheme with passive rotation speed is proposed in this study, which can effectively improve the flow pattern and reduce pressure inside the dishwasher pump, and also provide a new idea for rotor–rotor interference to guide the innovation of dishwashers.

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Through numerical simulations, this work analyzes the unsteady pressure pulsation characteristics in new type of dishwasher pump with double tongue volute and single tongue volute, under volute static and rotation conditions. Likewise, the performance tests were also carried out to verify the numerical results. Multiple monitoring points were set at the various positions of new type dishwasher pump to collect the pressure pulsation signals, and the relevant frequency signals were obtained via Fast Fourier Transform, to analyze the influence of volute tongue and its passive speed on the pump performance. The results reveal that when the double tongue volute is stationary, the pressure pulsation amplitudes increase from the impeller inlet to the impeller outlet. Under the influence of shedding vortex, the pressure pulsation in the lateral region of tongue becomes disorganized, and the main frequency of pressure pulsation changes from blade frequency to shaft frequency. In addition, compared with the static volute, double tongue volute can effectively guide the water flow out of the tongue during the rotation process, thus ensuring good periodicity for pressure pulsation in the tongue region. Accordingly, a volute reference scheme with passive rotation speed is proposed in this study, which can effectively improve the pressure pulsation at tongue position, and provides a new idea for rotor-stator interference to guide the innovation of dishwasher.