Rotary Wind-driven Triboelectric Nanogenerator for Self-Powered Airflow Temperature Monitoring of Industrial Equipment.

Heat dissipation performance is crucial for the operational reliability of industrial equipment, which can be monitored by detecting the wind or airflow temperature of the radiator. The emergence of triboelectric nanogenerators (TENGs) provides new routes for wind energy harvesting and self-powered sensing. Herein, a rotary wind-driven triboelectric nanogenerator (RW-TENG) with soft-contact working mode is newly designed to achieve tunable contact areas by utilizing the reliable thermal response of NiTi shape memory alloy (SMA) to air/wind temperature. The RW-TENG can generate different triboelectric outputs under air stimulation with different speeds or temperatures, which is demonstrated as a power source for online monitoring sensors, self-powered wind speed sensing, and airflow temperature monitoring. Specifically, a self-powered sensor of wind speed is demonstrated with a sensitivity of 0.526 µA m-1 s between 2.2 and 19.6 m s-1, and a self-powered monitoring device of high airflow temperature, which show relatively short response time (109 s), strong anti-interference ability and outstanding long-term durability. This study introduces an innovative route for real-time detection of airflow temperature in wind-cooled industrial equipment, showing broad application prospects for information perception and intelligent sensing of the industrial IoTs.

Real-Time Measurement of SO2, H2S, and CS2 Mixed Gases Using Ultraviolet Spectroscopy and a Least Squares Algorithm.

Sulfur dioxide, carbon disulfide, and hydrogen sulfide are important decomposition products of insulating gas sulfur hexafluoride, and their types and contents are of great significance for the fault diagnosis of SF6 insulated equipment. In this paper, a method of combining ultraviolet absorption spectroscopy and least squares fitting is proposed for the quantitative calculation of sulfur dioxide, carbon disulfide, and hydrogen sulfide mixed gases. All three gases have absorption peaks in the ultraviolet band and they overlap with each other which makes it hard to determinate the concentrations of the three gases directly. During the experiment, we found that high concentrations of sulfur dioxide and carbon disulfide interfered with the hydrogen sulfide calculation and the magnitude of this interference was positively correlated with these two gas concentrations. Therefore, we found a modified equation for the correction of hydrogen sulfide. Combined with this equation, accurate quantitative detection of three gases can be achieved. The detection ranges are 0.5-10 parts per million for sulfur dioxide and hydrogen sulfide, and 10-300 parts per billion for carbon disulfide. This paper provides a simple and efficient detection method, which is convenient for integration into detection equipment and it provides a support method for the diagnosis of sulfur hexafluoride decomposition gases.

Interaction Mechanism between the C4F7N-CO2 Gas Mixture and the EPDM Seal Ring.

C4F7N (fluorinated nitrile) has been introduced as a remarkable substitute gas for the greenhouse gas SF6 (sulfur hexafluoride) which is used in gas-insulated equipment (GIE). Intensive investigations about the compatibility between C4F7N and materials used in GIE are required to decide their long-term behavior. In this paper, the interaction mechanism between EPDM, used as a sealing ring in GIE, and C4F7N-CO2 was explored. The composition and morphology properties of EPDM were first revealed based on scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that EPDM rubber is incompatible with the C4F7N-CO2 gas mixture at temperatures higher than 70 °C. There exist chemical reactions between EPDM and C4F7N, resulting in the generation of gaseous byproducts including C3F6, CF3H, and C2F5H and corrosion of EPDM. DFT calculation also shows that the interaction between C4F7N and EPDM could cause the dissociation of C4F7N. Relevant results provide important guidance for the engineering application of the C4F7N gas mixture.

Quantitative analysis of SO2, H2S and CS2 mixed gases based on ultraviolet differential absorption spectrometry.

SO2, H2S and CS2 are the decomposition components of insulating gas SF6. The detection of these gases is significant for the online monitoring and fault diagnosis of SF6 electrical equipment. In this study, an ultraviolet differential optical absorption spectrometry (UV-DOAS) platform for detecting the concentration of SO2, H2S and CS2 mixed gases was established and a quantitatively detecting method was proposed. Firstly, the concentration of SO2 was calculated by the spectrum data at 300 nm band. Then the gas mixture spectra of H2S and CS2 at 200 nm band were obtained after linear deduction of SO2 spectrum. By wavelet extraction and fourier transform, the spectral information of H2S and CS2 was separated and the concentrations of the two gases were calculated. The method can detect the concentrations of SO2 (1-20 ppm), H2S (1-20 ppm) and CS2 (0.01-2 ppm) ternary gas mixture and the detection limits of SO2, H2S and CS2 are 0.44 ppm, 0.49 ppm and 3.23 ppb. This method has good detection sensitivity and high detection precision, which is suitable for the on-line monitoring of SF6 gas insulated equipment.

Ultraviolet Spectral Analysis and Quantitative Detection of Heptafluoroisobutyronitrile (C4F7N) in a C4F7N-Carbon Dioxide (CO2) Gas Mixture.

As an alternative to sulfur hexafluoride (SF6) with great potential for application, heptafluoroisobutyronitrile-carbon dioxide (C4F7N-CO2) gas mixture has been applied in various gas-insulated equipment. The insulation performance of the gas mixture is closely related to the mixing ratio. Therefore, accurate quantification of C4F7N in the C4F7N-CO2 gas mixture has very important engineering significance. At present, there are few reports on the rapid quantitative detection of the concentration of C4F7N in the gas mixture. In this paper, a rapid analytical method for C4F7N concentration based on ultraviolet (UV) absorption spectroscopy is constructed. The UV spectral characteristics of C4F7N molecules are calculated by density functional theory. The appropriate bands that can be detected are determined by analyzing the calculated results. A concentration detection system of C4F7N based on UV absorption spectroscopy is built. Through analysis of the calculated results and experimental results, a quantitative detection method of C4F7N in the C4F7N/CO2 gas mixture is determined. The method can achieve accurate detection of the concentration of the gas mixture in the conventional application range (including 4-10% C4F7N). The coefficient of the determination R2 of the concentration inversion curve reaches 0.999 and the inversion error ratio does not exceed 5%. The related research results provide an important reference for the engineering application of the gas mixture.

SF6 abatement in a packed bed plasma reactor: study towards the effect of O2 concentration.

SF6 is a greenhouse gas with extremely high global warming potential value (GWP). In this paper, oxygen and a packed bed plasma reactor (PBR) were applied to remove it. The synergistic effect between oxygen and PBRs was evaluated by the destruction and removal efficiency (DRE) and energy yield (EY) at different oxygen concentrations. The results show that excessive oxygen weakened the micro-discharge in a PBR to suppress SF6 degradation while the addition of a proper amount of oxygen (1-4%) can improve the DRE and EY. 2% O2 in the system had the best promoting effect on the destruction of 6-10% SF6, which made the maximum energy yield (EY) increase by 50.99% to 37.99 g kW-1 h-1 (SF6 concentration was 10%, flow rate was 150 mL min-1). Moreover, in the flow rate range of 100 mL min-1 to 250 mL min-1, the DRE decreased and the EY increased with the flow rate. In addition, the selectivity of different products were affected by the oxygen concentration. For 6% SF6, SO2F2 selectivity was always the highest while SO2 was always the lowest; when the oxygen concentration did not exceed 2%, SOF2 selectivity was higher than SOF4, otherwise, SOF4 selectivity was higher than SOF2. This paper provided experimental support for better understanding of the effect of additional gas concentration on SF6 decomposition in a PBR.

Pristine and Cu decorated hexagonal InN monolayer, a promising candidate to detect and scavenge SF6 decompositions based on first-principle study.

We carried out the first-principle study of four types of SF6 decompositions adsorbed on pristine and Cu atom decorated hexagonal InN monolayer. The adsorption structures, adsorption energy, electron transfer, band structure, density of states and desorption properties were discussed to evaluate the possible application of InN monolayer in field of adsorbent and gas sensor. The results revealed that the pristine InN monolayer has the largest adsorption energy to SO2 with evident chemical interactions. The introduction of Cu adatom on InN monolayer significantly enhanced the chemical interactions between the InN monolayer and the SO2, SOF2, SO2F2 gas molecule but declined the adsorption energy of HF. We also investigated the electronic properties of all adsorption configurations and estimated the desorption time of every gas molecule from pristine and Cu decorated InN monolayer to evaluate the potential application in noxious gas detecting and scavenging in gas insulated switch-gear (GIS).

Abatement of SF6 in the presence of NH3 by dielectric barrier discharge plasma.

In this paper, the degradation rate, energy yield and the degradation by-products of SF6 was studied when different concentrations of NH3 were added. When NH3 concentration increased from 0 to 2%, the degradation rate efficiency(DRE) of SF6 increased from 60% to 97.23% under the flow rate of 50ml/min and 94W input power. The energy yield(EY) reached 4.16g/kWh. In addition, we found that increasing the flow rate to 250ml/min, the DRE decreased to 58.71%, but the EY increased to 12.55g/kWh. The main gas by-products are SOF2, SO2F2, SO2, OF2, HF and NF3. When the concentration of initial NH3 increased, the SO2 concentration increased while the concentrations of SOF2, SO2F2, SOF4 decreased. In addition, we found that a pale yellow film formed on the surface of the reactor wall. XPS analysis showed that the solid products were mainly S, NH3HF and NH4HF2. The emission spectra show that NH3 addition can effectively promote the formation of active particles and increase plasma density.The addition of NH3 can convert some of the sulfur and fluorine into solid products and reduce the production of toxic gases.

Detection of Ozone and Nitric Oxide in Decomposition Products of Air-Insulated Switchgear Using Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS).

Air-insulated switchgear cabinets play a role in the protection and control of the modern power grid, and partial discharge (PD) switchgear is a long-term process in the non-normal operation of one of the situations; thus, condition monitoring of the switchgear is important. The air-insulated switchgear during PD enables the decomposition of air components, namely, O3 and NO. A set of experimental platforms was designed on the basis of the principle of ultraviolet differential optical absorption spectroscopy (UV-DOAS) to detect O3 and NO concentrations in air-insulated switchgear. Differential absorption algorithm and wavelet transform were used to extract effective absorption spectra; a linear relationship between O3 and NO concentrations and absorption spectrum data were established. O3 detection linearity was up to 0.9992 and the detection limit was at 3.76 ppm. NO detection linearity was up to 0.9990 and the detection limit was at 0.64 ppm. Results indicate that detection platform is suitable for detecting trace O3 and NO gases produced by PD of the air-insulated switchgear.

Adsorption of SF6 Decomposed Products over ZnO(101Ì 0): Effects of O and Zn Vacancies.

We carried out a density functional theory study to investigate the adsorption behavior of four kinds of SF6 decomposed products over the ZnO(101̅0) surface. The effects of O and Zn vacancies on the surface were also considered. For perfect ZnO(101̅0) surface, the adsorption of SO2 and H2S exhibits stronger chemical interactions compared to the adsorption of SOF2 and SO2F2. For SO2 and H2S adsorption, there may exist new chemical bond formation between the molecule and the surface and the H2S molecule experiences one H-S broken bond. The introduction of O vacancy cannot obviously enhance the chemical interactions between these four molecules and the surface. However, the Zn vacancy on the surface can significantly elevate the chemical interactions between SO2/H2S and the surface. The two-coordinated O atom (O2c) on the surface plays an important role. For SO2 and H2S adsorption, the S atom in SO2 or H2S tends to bond to the O2c atom, bringing much larger adsorption energy compared to the adsorption over the perfect ZnO(101̅0) surface. This work can provide a basis for surface modification of ZnO in applications to detecting SF6 decomposed products by theoretical evaluation.