The type and concentration of dissolved gases in transformer insulating oil are used to assess transformer conditions. In this paper, an online detection setup for measuring the concentration of multicomponent gases dissolved in transformer insulating oil is developed, which consists of an oil-gas separation system and an optical system for acquiring the transformer status in real time. The oil-gas separation system uses low pressure, constant temperature, and low-frequency stirring as working conditions for degassing large-volume oil samples based on modified headspace degassing. The optical system uses tunable diode laser absorption spectroscopy (TDLAS) to determine the gas concentration. Six target gases (methane, ethylene, ethane, acetylene, carbon monoxide, and carbon dioxide) were detected by three near-infrared lasers (1569, 1684, and 1532 nm). The stability of the optical system was improved by the common optical path formed by time-division multiplexing (TDM) technology. The calibration experiments show that the second harmonics and the concentrations of the six gases are linear. A comparison experiment with gas chromatography (GC) demonstrates that the error of acetylene reaches the $\mathrm{nL}/\mathrm{L}$ level, while the other gases reach the $\mathsf{\mu }\mathrm{L}/\mathrm{L}$ level. The data conforms to the power industry testing standards, and the state of the transformer is analyzed by the detected six characteristic gases. The setup provides an effective basis for the online detection of dissolved gas in transformer insulating oil.

The temperature measurement of explosion flames is a key challenge in the field of weapons research. Many pyrometers have been developed to determine the accurate temperature of the explosion flame. However, these pyrometers can only measure the true temperature curve and the brightness temperature field of explosion flames, not their true temperature field. A multispectral pyrometer that measures the true temperature field of the explosion flame is developed in this paper. The multispectral pyrometer acquires brightness temperature field images at four different wavelengths of the explosion flame at the same moment using synchronous spectral-splitting technology. The pixels of the obtained four brightness temperature field images are then aligned using an edge feature-based image matching algorithm. The true temperature value is finally calculated for each pixel using multispectral radiation thermometry to construct the true temperature field of the explosion flame. Based on the experimental results, the true temperature field of the explosion flame can be measured with the proposed multispectral pyrometer.

This paper develops a two-dimensional array pyrometer, which can measure the true temperature field of the two-dimensional array. The pyrometer consists of an optical part, a circuit part and a software part. In the optical part, the radiation energy of the two-dimensional array target is obtained by scanning with the rotating mirror. Then, the radiation signal is converted and amplified by the circuit part. The software component realizes the functions of the pyrometer calibration, signal acquisition and data processing. The data processing adopts the secondary measurement method to calculate the true temperature and uses the multi-threaded method to improve the operational efficiency. Experiments show that the uncertainty of the two-dimensional pyrometer array can reach 1.43%. Compared with the single-threaded method, the true temperature operation time of the two-dimensional pyrometer array is improved by 77%, which verifies that the software operational efficiency is greatly improved.

This paper investigates the melting process of phase change material in a rectangular cavity at different inclination angles. Paraffin is used as a phase change material in this study. One side of the cavity is heated while the other sides are considered to be adiabatic. The investigated angles of inclination include 0° (bottom horizontal heating), 30°, 60°, 90° (vertical heating), 120°, 150° and 180° (top horizontal heating). Shapes of the solid liquid interface and temperature variations during the melting process were discussed for all the inclination angles. The results reveal that the inclination angles have a significant impact on the melting behavior of paraffin. As the angle increases from 0° to 180°, the complete melting time increases non-linearly.