Abnormal Temperature Rise Research Articles

Application of the Finite Element Method for Analyzing the Vibration Characteristics of a Spindle System and Fault Diagnosis

The performance of a spindle will gradually decline, the vibration intensity will increase, and the temperature rise will become abnormal with the accumulation of service time. Consequently, the accuracy of the machining product will not meet its production requirements. Studies on the variation characteristics of the spindle unit have clarified the reasons for its abnormal vibration and temperature rise, in principle, to help enterprises conduct preventive maintenance before any serious failure occurs and improve production efficiency. Based on the Timoshenko beam model and rotor dynamics theory, this study uses the finite element method (FEM) to analyze the vibration characteristics of the spindle rotor system. Moreover, it thoroughly analyzes the influence of the spindle bearing heat on the stiffness of the spindle system and identifies the resonance conditions of the spindle rotor within the power frequency range. This research has identified that when the vibration frequency of the spindle operates at a speed of 12,000 r/min, if its vibration frequency is lower than 200 Hz, it will be affected by abnormal vibrations during startup, which will weaken the health status of the spindle and reduce its service life. Similarly, when the working speed of the spindle is 30,000 r/min, if its vibration frequency is lower than 50 Hz, abnormal vibration will occur during startup and operation, thereby reducing its service life.

Experimental study on the thermal response of rocks to stress change and its significance

SUMMARY Bedrock temperature contains effective information about changes in the crustal stress. A new method of detecting crustal stress change by bedrock temperature (DSCT) has been proposed. Understanding the stress-induced temperature response characteristics of loaded rocks is fundamental for applying DSCT. In this study, temperature observation experiments of different rocks and water-saturated sandstones subjected to tiered cyclic loading were conducted to investigate the temperature–stress relationship throughout the whole rock deformation and failure process. Through experiments, some valuable results are obtained: (i) temperature changes synchronously with stress and has a very strong linear correlation with it; (ii) the magnitude of temperature response to stress (TRS) is approximately 1 mK MPa−1, ranging from strong to weak are sandstone, marble, diorite and basalt, respectively. The differences in TRS of various rocks are determined by their major rock-forming minerals, textures and structures; (iii) the evolution of TRS experiences three stages: the TRS rises rapidly in the compression stage, slowly in the acoustic emission quiet period and a significant increase in TRS before rock failure is observed on marble, sandstone and basalt, consistent with the abnormal bedrock temperature rise preceding earthquakes; (iv) the TRS of water-saturated sandstones is higher compared to the dry ones, and the abnormal sharp increase in TRS before rock failure is also more significant in the former. These findings mentioned above promote the understanding of thermal anomalies preceding earthquakes.

Heatstroke: a multicenter study in Southwestern China.

An increase in Heatstroke cases occurred in southwest China in 2022 due to factors like global warming, abnormal temperature rise, insufficient power supply, and other contributing factors. This resulted in a notable rise in Heatstroke patients experiencing varying degrees of organ dysfunction. This descriptive study aims to analyze the epidemiology and clinical outcomes of Heatstroke patients in the ICU, providing support for standardized diagnosis and treatment, ultimately enhancing the prognosis of Heatstroke. A retrospective, multicenter, descriptive analysis was conducted on Heatstroke patients admitted to ICUs across 83 hospitals in southwest China. Electronic medical records were utilized for data collection, encompassing various aspects such as epidemiological factors, onset symptoms, complications, laboratory data, concurrent infections, treatments, and patient outcomes. The dataset primarily comprised classic heatstroke, with 477 males (55% of total). The patient population had a median age of 72 years (range: 63-80 years). The most common initial symptoms were fever, mental or behavioral abnormalities, and fainting. ICU treatment involved respiratory support, antibiotics, sedatives, and other interventions. Among the 700 ICU admissions, 213 patients had no infection, while 487 were diagnosed with infection, predominantly lower respiratory tract infection. Patients presenting with neurological symptoms initially (n = 715) exhibited higher ICU mortality risk compared to those without neurological symptoms (n = 104), with an odds ratio of 2.382 (95% CI 1.665, 4.870) (p = 0.017). In 2022, the majority of Heatstroke patients in southwest China experienced classical Heatstroke, with many acquiring infections upon admission to the ICU. Moreover, Heatstroke can result in diverse complications.

Research on the change in lubrication state and temperature control strategy of high-speed train axle box bearings using non-destructive testing

ABSTRACT The heat generation problem of axle box bearing during churning phase leads to abnormal temperature rise and temperature alarm, which affects the normal operation of high-speed train. Aiming at this problem, the temperature characteristics of bearing initial lubrication phase is studied, and the multi-speed grade cycle running schemes are used in tests to run multiple bearings for multiple times. The temperature data and friction data in tests are collected by using non-destructive testing method, and characteristic extraction is carried out. Under the premise of not destroying the internal structure and lubrication state of the bearing, the lubrication state inside the bearing is reflected by the change of the characteristic values. A 118 min scheme is proposed, and the bearing using this scheme to run on the test rig is used in the actual operation. The results show that the temperature of the bearing with running-in test is lower than that of the bearing without running-in test, which indicates the effectiveness of the proposed temperature control strategy.

Responses of financial stress and monetary policy to global warming: Evidence from China

We explore the marginal dynamic effect of abnormal temperature rise on China's financial stress and monetary policy using monthly data from January 2002 to December 2019. Our empirical results demonstrate that: (a) China's financial stress has a positive response to an increase in abnormal temperature change shock significantly, especially in the 4–7 months after the shock; (b) the introduction of monetary policy regulation into the economic system can effectively alleviate the financial instability caused by the rise in temperature; (c) from the perspective of the effectiveness of monetary policy transmission, price-based monetary policy is generally better than quantity-based monetary policy; (d) the adjustment of monetary policy can effectively expand the financing scale of the whole society with credit scale mattering most; (e) when financial stress is higher, the impact of a temperature shock on the financial market is stronger, as the stabilizing effect of expansionary monetary policy is more obvious. Our results are robust to wider checks and have important policy implications.

Study on the Mechanism Effect of Bending Loads on the Decay-like Degradation of Composite Insulator GFRP Core Rod

This paper investigates the deterioration of, and the abnormal temperature rise in, the GFRP core rod material of compact V-string composite insulators subjected to prolonged alternating flexural loading under wind-induced stresses. The axial stress on the GFRP (Glass Fiber Reinforced Plastic) core rod, resulting from transverse wind loads, is a focal point of examination. By establishing a stress model and damage model, the paper simulates and computes the evolution of damage in the outer arc material of composite insulator core rods subjected to alternating flexural loads. Additionally, a multi-factor coupled aging platform is set up, integrating humidity, heat, and mechanical stress, to simulate the crazing deterioration process of composite insulators under alternating flexural loads. Experimental results reveal that during 400,000 alternating load cycles, the core rod underwent stages of surface damage, damage increasing, fatigue embrittlement, matrix hydrolysis, and fiber fracture. Simultaneously, the silicone rubber sheath on the outer side of the composite insulator’s bending arc develops cracks over aging time, creating pathways for moisture ingress into the interface and core rod. The dielectric constant and dielectric loss factor of the aging region of the core rod increase to varying degrees compared to the non-aging part. Moreover, the degree of abnormal heating of the samples intensifies with the duration of aging experiments. These findings underscore the significance of understanding the aging and decay-like fracture process of compact line V-string composite insulators. They provide crucial insights for future research aimed at enhancing the material properties of composite insulator core rods.

Investigation on skidding behavior of a lubricated rolling bearing with fluid–solid-heat coupling effect

Skidding phenomenon is a critical cause of abnormal vibration, noise, and temperature rise of lubricated rolling bearings. It is affected by various factors such as the structure size, lubrication medium, thermal properties, and service conditions. Owing to the limited influence factors, the skidding mechanism of the lubricated rolling bearing under the fluid–solid-heat coupling effect is not well understood. Therefore, a fluid–solid-heat coupled dynamics model of the lubricated rolling bearing based on the dynamic and thermodynamic equations is developed in this study using the lumped parameter method and thermal network method. The time-varying geometrical parameter of the components, time-varying kinematic viscosity and density of the lubricant, and temperature raise and distribution of the bearing during the operation process are involved in this model, which can significantly affect the system parameters such as the equivalent nonlinear contact stiffness, friction coefficient, viscous drag, radial and circumferential clearances, and so on. To verify the accuracy of the proposed model, the cage slipping velocity and outer ring temperature rise are compared between simulation results and test data, respectively. The influence of the rotating speed of the inner ring and radial load on the temperature raise and skidding phenomenon is analyzed in detail. The results indicate that skidding behaviors and internal dynamic interactions are intensified under the thermal effect. Therefore, improving the heat dissipation efficiency of the bearing can alleviate skidding, especially under light load and high-speed conditions. It should be noted that the rotating speed of the ring and radial load are the primary factors affecting bearing temperature rise and skidding phenomenon.

Optimization of the Monitoring of Coal Spontaneous Combustion Degree Using a Distributed Fiber Optic Temperature Measurement System: Field Application and Evaluation

Coal spontaneous combustion (CSC) in gob not only leads to wasted resources and casualties, but also produces a lot of waste gas that pollutes the underground environment. Mastering the degree of CSC helps ensure that timely and effective control measures are taken. The real-time and accurate monitoring of temperature, as the primary indicator of the extent of CSC, is difficult due to the harsh and hidden environment of gob, resulting in a reduced ability to anticipate and prevent CSC. In this work, a complete distributed optical fiber temperature sensing system (DTSS) set with strong anti-damage ability was developed. The optical cable is protected by internal parallel steel cables and external protective pipes, which greatly improve the system’s reliability and integrity when used in gob. During its application in the Wangyun Coal Mine, an abnormal temperature rise in gob was discovered in time, and the effect of inhibitor spraying was monitored and evaluated. The degree of CSC in the gob was accurately identified, which shows that the work of coal mining can be targeted. This work is expected to improve early warning capability to prevent the risk of CSC in gob, and has promising applications.

Study on helium gas bubble levitation in high field superconducting magnet

The abnormal temperature rise and early quench often happened to the high field superconducting magnet, especially when the magnetic field is higher than 20 T. This phenomenon is attributed to helium gas bubbles levitation in the special high magnetic field environment. So, it is very important to accurately identify the formation and distribution of helium gas bubbles levitation for the development of high field superconducting magnet. In this paper, a new analytical method based on pressure is proposed to analysis the formation conditions and the spatial distribution of helium gas bubbles levitation. And a no-insulation REBCO insert coil was also developed to study the phenomenon of helium gas bubbles levitation. The REBCO insert coil was tested in high magnetic field produced by a water-cooled magnet. The new analytical method was used to simulate the formation conditions of helium gas bubbles levitation and the temperature distribution of the REBCO insert.

Locating the Oil Leakage on Power Equipment via Ultraviolet-Induced Hyperspectral Imaging Technology

Oil leakage will cause abnormal temperature rise and discharge of oil-filled power equipment, which seriously threatens insulation reliability. In this paper, based on the synchronous fluorescence spectra (SFS) and excitation emission matrix (EEM) of mineral and vegetable oils, the ultraviolet-induced hyperspectral imaging (UV-induced HSI) measurement system is developed. Then, the fluorescence-reflectance spectra of oil traces and non-oil areas are determined via the proposed measurement system. Next, the influence factors of fluorescence-reflectance intensity, including UV source light power, detection angle degree and detection distance are discussed. By analyzing the fluorescence-reflectance intensity differences in fluorescence bands, principal component analysis (PCA) is applied for date dimension reduction and anomaly detection to realize oil leakage trace visualization. Finally, the validation test results prove that this method exhibits a general applicability for tracing mineral and vegetable oil leakage traces on different surface materials in indoor and outdoor conditions. This approach will improve the detection rate of oil leakage defects, and promote the intelligent level of operation and maintenance of power equipment.

Causes and troubleshooting of high bearing bush temperature of a nuclear power steam turbine

As an important part of the steam turbine unit, once the temperature of the bearing bush rises abnormally, it will not only reduce the application performance of the bearing itself, but also affect the normal operation of the whole unit, resulting in shutdown accidents. Aiming at the problem of abnormal temperature rise of bearing bush of nuclear power steam turbine, combined with the operation and maintenance of the unit, the real cause of high bearing bush temperature is clarified, and then targeted treatment measures are taken to solve the problem, which is beneficial to ensure the safety of the unit.

Research on defect type diagnosis of composite insulator based on infrared detection technology

Composite insulator is widely used in Hainan area of China because of its lightweight, small volume, good anti pollution flashover performance and many other advantages. Aiming at the problem of how to correctly judge the aging state of composite insulators under live conditions in Hainan’s high humidity environment, this paper analyzes the main causes of composite insulator heating and the heating position and temperature rise of composite insulator under different defect types by building equivalent circuit, and puts forward several criteria for distinguishing the defect types of composite insulator by infrared detection technology; taking the abnormal temperature rise of 220kV returned composite insulator in Hainan as an example, the defect type of the composite insulator is analyzed by infrared detection technology, and the correctness of the infrared results is verified by the appearance inspection and anatomical analysis of the test object. The results show that the defect that the temperature rise is between 1-5°C and only appears among the fittings and the first umbrella is caused by the aging, moisture absorption or surface pollution of the umbrella cover; the defect that the temperature rise is above 5°C and the range extends from the high-voltage end sheath to several umbrella skirts is caused by the internal deterioration of the insulator. In conclusion, the conclusion provides a guarantee for the safe operation of power grid and has important reference value for the study of on-line monitoring of composite insulators.

Influence of water and defects on abnormal temperature rise of composite insulator

Water and defects of composite insulator may cause its abnormal temperature rise, which seriously affects the safety of power grid. In this paper, the temperature rise tests of a 110 kV composite insulator before, after water immersion, and after water immersion and drying are firstly carried out. Then a phased array ultrasonic detector is used to detect the internal defects of the insulator. And the phased array ultrasonic recognition model for internal defects is proposed. Finally, the transverse anatomical test is carried out to verify the defects of composite insulator obtained by the temperature rise test and the phased array ultrasonic testing test. The results show that the temperature rise of composite insulator after water immersion is higher than that before water immersion. The maximum temperature rise of the insulator after water immersion is 1.2℃. And there is no temperature rise after drying. The defect between the sheath and the core rod at the temperature rise position after immersion is detected by the phased array ultrasonic testing. Cracks and discharge defects are observed anatomically. The accuracy of identification model is proved. And it provides an effective method for nondestructive detection of internal defects of composite insulator in the laboratory. According to the results of temperature rise test, ultrasonic detection and anatomical test, the high water content of the composite insulator sheath is one of the reasons for the slight temperature rise of the insulator. And water and defects are the direct reasons for the obvious temperature rise of composite insulator.

Study on influencing factors and laws of infrared temperature measurement of silicone rubber composite insulator

Silicon rubber composite insulator is favoured by power system because of its excellent anti-pollution flashover performance. Among them, the core rod is an important structural component to bear the mechanical load of composite insulator. In recent years, there have been many brittle fracture faults of composite insulators in China, which directly affect the reliability of transmission lines. The composite insulator is usually accompanied by abnormal heating during the aging process. As an effective live detection method, infrared temperature measurement can find the defects of composite insulator in time and reduce the occurrence of string breaking accidents. In this paper, by artificially simulating the abnormal temperature rise of composite insulator, infrared temperature measurement was carried out under the conditions of different observation distance, different observation angle, different sheath thickness and different heat source temperature, so as to explore the influencing factors and laws of infrared temperature measurement of composite insulator. The results show that due to the difference of heat loss, sheath barrier and radiation ratio in thermal radiation propagation, the measured temperature decreases and the absolute temperature difference increases with the increase of observation distance, sheath thickness and observation angle. The built-in heat source temperature increases the total internal heat, which can partially weaken the influence of sheath thickness on the measured temperature and significantly expand the difference caused by observation angle.

Beam-target configurations and robustness performance of the tungsten granular flow spallation target for an Accelerator-Driven Sub-critical system

The dense granular flow spallation target is a new target concept proposed for an Accelerator-Driven Sub-critical (ADS) system. In this paper, the beam-target configurations of a tungsten granular flow target for the ADS with a thermal power of 1 GW is explored. The beam profile options using different scanning methods are discussed. The critical geometry parameters are adjusted to investigate the performance of the granular target from the aspects of neutron efficiency, stability and temperature distribution in target medium. To figure out how the target under accident conditions would behave, different clogging conditions are induced in the simulation. The dynamic processes are analyzed and some important parameters such as abnormal temperature rise and beam cutoff time window are obtained. The response of the sub-critical reactor to a clogging accident is also investigated. It is indicated that the monitoring of the granular flow by the neutron detectors in the sub-critical core will be effective.

Temperature field monitoring of lithium battery pack based on double-clad fiber Bragg grating sensor

Lithium-ion battery is one of the most versatile energy storage technologies today, and the reliability and safety of lithium battery have always been the target pursued by the industry all the time, so it is particularly important to accurately monitor the safety status of the battery. Actually, the ultimate cause of all lithium battery safety problems lies in the thermal runaway inside the lithium battery. In order to overcome the current problems of temperature measurement systems, such as low accuracy and insufficient stability for long-time operation at relatively high temperature, a temperature monitoring system of quasi-distributed lithium battery based on double clad Fiber Bragg Grating (FBG) is proposed in this work. After the monitoring of the temperature field and bulge deformation of 18650 lithium battery pack by building 4 channels and 16 double clad FBG points to monitor the temperature field and bulge deformation of 18650 lithium battery pack, the results show that the points with abnormal temperature rise caused by short circuit and other problems can be accurately determined under the temperature of 0–450 ℃, with the corresponding temperature sensitivity of 10 pm/℃, and the resolution of 0.1 ℃. The double clad FBG attached to the surface of the lithium battery shell can also monitor the bulge deformation on the surface of the battery shell, and its longitudinal pressure modification sensitivity is up to 142 pm/N. The temperature field monitoring system of quasi-distributed lithium battery pack based on double clad FBG in this paper can not only ensure high-precision temperature and deformation measurement, but also have good stability and anti-interference ability, which shows that the research work in this paper is expected to provide a reliable theoretical and experimental basis for the safety monitoring and use of lithium battery pack.

Influences of kieselguhr on temperature rise of composite insulator in high‐humidity environment

Composite insulators are widely used in the power transmission system. Operating in the outdoor environment, the composite insulator will be inevitably polluted by natural contamination with the increase of service life, and contamination on the surface is one of the main reasons for the abnormal temperature rise of the insulator. In this study, the rated voltage was applied to the kieselguhr sample under a high-humidity environment, and its temperature rise characteristics and leakage current were tested. The research results show that the temperature rise in contamination falling-off region is significant and the leakage current is greater than the clean sample. By analysing the phenomenon with the help of the circuit model, it is concluded that the high resistance and voltage in contamination falling-off region leads to high heating power of the polarisation loss.

On Electric Field Distribution and Temperature Rise Effect of High Power VLF Antenna

When a high-power very low frequency (VLF) communication system is in operation, the end of the antenna is in an alternating strong electric field environment. Due to dielectric loss, abnormal temperature rise may occur at the end of the antenna. To solve the problem, analysis on the electric field distribution and temperature rising effect at the end of the antenna is first carried out in this paper. The factors that affect the electric field distribution and temperature rising, including the amplitude and frequency of the excitation voltage, the diameter of the antenna conductor and the material properties of the outer sheath of the antenna, are studied in detail. A novel approach to improve the electric field distribution and to suppress temperature rising is proposed by designing a dielectric loss eliminator, and the effectiveness of the designed device is verified by simulation.

ФИЗИОЛОГИЧЕСКИЕ АСПЕКТЫ ЗАСУХОУСТОЙЧИВОСТИ СОРТОВ ВИШНИ

There is an abnormal increase in average summer temperature in the southern region (Krasnodar Territory). This, more than ever, actualizes the problem of identifying drought-resistant varieties of fruit crops, including cherry. The purpose of this research was to study the physiological indicators of water regime: loss of water, water-holding capacity, leaf water content, abscisic acid content in leaves of different varieties of Cerasus vulgaris Mill., which determine resistance to temperature stress, as well as to identify the most drought-tolerant varieties to optimize the range of varieties for the south of our country. The studies were carried out in 2018–2019 in the Prikuban fruit-growing zone of the Krasnodar Territory. Sixteen varieties of Cerasus vulgaris Mill. were the objects of the research. Varieties ʻKrasnodarskaya sladkayaʼ and ʻKazachkaʼ served as a control. Planting schemes – 6 × 4 m and 5 × 3 m. Soil – chernozems leached. pHwater – 6.8–7.22. Humus content – 3.47 %. In summer, meteorological conditions were characterized by an abnormal temperature rise (up to 39.3 ℃) and extended periods of drought. Studying of water regime was carried out according to the modified methodology of M. D. Kushnerenko using the gravimetric method. In laboratory experiments, we used the capillary electrophoresis “Kapel 104 P” (power supply with a positive polarity; equipped with a photometric detector; set wavelength – 254 nm). In the course of the research, we revealed that the water content in cherry leaves during the period of the adverse draught (in July) was 57.9 %; in the context of studied cherry varieties, it varied insignificantly (Cv = 4.4 %). For two hours, the loss of water by the leaf apparatus was not high – from 6.5 % to 11.9 % with a low coefficient of variation by varieties (Cv = 1.9 %). The water-holding capacity of leaf tissues was 19.6 %, the range of variability of which was insignificant by varieties (Cv = 18.0–24.2 %). The average content of abscisic acid in cherry leaves was 4.3 mg/kg and varied depending on the studied cherry varieties within the range of 1.5–14.2 mg/kg. According to the complex of physiological indicators of the water regime (low water loss (6.5–7.9 %), high water-holding capacity (19.4–24.2 %) and leaf water content (58.1–61.9 %), as well as increased abscisic acids content (11.0–14.2 mg/kg)), such cherry varieties/cultivars as ʻDuke Ivanovnaʼ, ʻDuke Khodosaʼ, ʻFeyaʼ, ʻMolodezhnayaʼ and ʻErdi Botermoʼ were classified as highly drought-resistant. They are recommended for expanding the range of adaptive cherry varieties/cultivars in the southern part of Russia.

Structural Parameters Optimization of Corona Ring of Tethered Balloon-Type VLF Antenna

The antenna end of the tethered balloon-type high-power VLF communication system will be exposed to an extremely strong alternating electric field environment when it is in operation. Due to dielectric loss, an abnormal temperature rise may occur at the antenna end, which may lead to an antenna fracture in serious cases. It is an effective measure to install a corona ring at the end of the antenna to prevent such accidents. In this paper, the structural parameters of the corona ring, including ring radius, tube radius, and ring depth, are optimized based on intelligent optimization algorithm to significantly improve the electric field distribution and restrain the temperature rise to the maximum extent. The effectiveness of the optimization results is verified by simulation.