The spatially nonuniform distribution of the Seebeck coefficient along a thermocouple wire is an important source of temperature measurement uncertainty. Existing double-gradient scanning methods are constrained by the size of the heat source and disturbances at the end boundaries, resulting in a broad scanning thermal kernel that makes millimeter-scale local inhomogeneities difficult to resolve. To address this limitation, a high-resolution double-gradient scanning method based on laser heating was proposed. First, the coupling among thermocouple inhomogeneity, the temperature gradient, and the output EMF was analyzed. A measurement system incorporating a fiber laser and a quasi-steady-state isothermal box was then constructed, and key parameters, including the laser spot size, laser power, and scanning speed, were determined. The effective width of the laser-induced temperature-gradient kernel was evaluated using a differential double-Beta probability density function (PDF) model. Finally, the repeatability, local-region detectability, and applicability of the method to thermocouples of different wire diameters were experimentally evaluated. At a laser power of 0.5 W and a scanning speed of 60 mm/min, the mean standard deviation of the positive and negative thermal-kernel lobes was 2.1 mm, and a 1-mm-long locally aged region produced a repeatable, detectable response. The maximum standard deviations of the peak/valley positions and EMFs across five repeated scans were 0.55 mm and 5.83 μV, respectively. The proposed method produces a millimeter-scale thermal kernel for thermocouple inhomogeneity detection and has potential applications in thermoelectric-material characterization, process optimization, and thermocouple metrological calibration.

It is generally considered that spark resistance can be determined by circuit resistance subtracted from the total resistance of the discharge circuit and circuit resistance is equal to the total resistance when the spark gap is shorted out. However, practical methods for shorting out the spark gap have not been clearly defined in existing researches. Two methods for shorting out the spark gap were elaborated, and a method for measuring circuit resistance through linear fit was developed in this paper. Experiments were conducted to compare and analyze different circuit resistance measurement methods. The method of shorting out the spark gap by wire is more recommended, compared to that by setting the electrode gap to zero. The linear fitting method avoids the problem of internal discharge in the discharge relay, but it needs to maintain consistency in the discharge environment to minimize the impact of electrostatic discharge randomness. This study offers valuable guidance for accurately measuring spark resistance, which is crucial in minimum ignition energy testing of dust clouds highly sensitive to electrostatic discharge.

Sodium percarbonate (SPC), as a highly efficient oxidizing agent, is widely used in the fields of cleaning and environmental protection. However, its thermal decomposition process is accompanied by significant exothermic heat release, posing risks of thermal runaway and fire hazards. In this study, the thermal decomposition data of SPC were obtained by differential scanning calorimetry (DSC). The overlapping reaction peaks were deconvoluted using the Fraser-Suzuki (FS) function, revealing two distinct reaction steps that occur consecutively. The kinetic parameters for each step were then determined separately. Kinetic analysis revealed that the activation energy for the first step is in the range of 137.22 to 151.80 kJ/mol, with the pre-exponential factor ranging from 9.62 × 1014 s-1 to 8.66 × 1016 s-1. For the second step, the activation energy ranges from 90.21 to 106.41 kJ/mol, and the pre-exponential factor ranges from 1.38 × 109 s-1 to 3.86 × 1011 s-1. The first subreaction was modeled by the Avrami-Erofe'ev (A4) model, while the second subreaction was modeled by the truncated Šesták-Berggren (SB) model. Based on the obtained kinetic parameters, the decomposition behavior at heating rates of 2°C/min and 20°C/min was predicted, which validated the accuracy of the kinetic parameters. Furthermore, the temperatures at which the time to the maximum reaction rate are 8 h (TD 8) and 24 h (T D24), and the self-accelerating decomposition temperatures (SADT) were determined to be 86.6°C, 78.8°C, and 71°C, respectively. The kinetic parameters and thermal hazard evaluation results obtained in this study provide data support for determining the safe storage temperature and optimizing transportation schemes for SPC.

Kinetic predictions are widely used in thermal runaway research. At present, the model-fitting method based on single experimental data is mainly adopted in the kinetic prediction of accelerating rate calorimetry (ARC), which has the problems related to difficult analysis of reaction mechanism and large uncertainty of kinetic parameters. The Kinetic Committee of the International Confederation for Thermal Analysis and Calorimetry has clearly proposed to avoid using this method. The development of prediction methods that use multiple temperature programs is essential in the field of ARC. To address these issues, the kinetic predictions based on isoconversional methods were studied. The data of the n-order reaction and autocatalytic reaction under adiabatic conditions were obtained by numerical simulations, and the kinetic parameters were estimated by the Vyazovkin and the Friedman methods. Then, the kinetic parameters are substituted into the equations for adiabatic and isothermal prediction. To solve the problem of large prediction error, a simple correction method of kinetic parameter was proposed. Finally, the kinetic prediction approaches were verified by experiments. The results show that the ARC can carry out model-free kinetic predictions based on the isoconversional methods. The Vyazovkin method has higher prediction accuracy than the Friedman method, and the simple correction method can effectively improve prediction accuracy. The kinetic prediction approaches based on the isoconversional methods are beneficial supplements and alternatives for traditional kinetic analysis method of the ARC.

There is usually a significant voltage drop on the electrode during the brief delay before spark discharge occurs when the storage capacitance is small (around or below 100 pF). This leads to a decrease in capacitor energy, which may result in an overestimation of the minimum ignition energy (MIE) of dust cloud. A method that utilizes a current probe to obtain the inception discharge voltage was therefore developed. Firstly, the voltage attenuation on the electrode without spark discharge is measured, enabling an accurate calculation of parasitic capacitance. Subsequently, the inception discharge voltage in a spark discharge is calculated based on the measured spark current, thereby enabling the determination of capacitor energy before spark discharge. The results show that the fitted current curves based on the calculated inception discharge voltage exhibited consistency with the actual spark current curves, indicating that the calculated value of inception discharge voltage was consistent with the actual situation. The method effectively addresses challenges associated with measuring the inception discharge voltage in cases of small storage capacitance, which helps to calculate the capacitor energy before spark discharge for MIE testing of dust clouds that are highly sensitive to electrostatic discharge.

最小点火能(minimum ignition energy,MIE)是表征可燃粉尘爆炸危险性的核心参数,其测试准确性对粉尘爆炸控制至关重要.然而最小点火能测试方法多样,测试结果有诸多影响因素,不利于粉尘爆炸控制工作开展.为此,梳理了最小点火能测试过程中粉尘分散、静电火花发生、火花能量计算及最小点火能判定等阶段不同方法的原理和特点,分析了粉尘理化性质、粉尘分散状态、火花发生参数以及测试环境等因素对最小点火能测试结果的影响,归纳了近五年来该领域的研究热点,并对未来研究方向提出建议.

In this work, a vibrating capacitive sensor utilizing dual cantilever tuning fork resonance for electrostatic potential modulation was designed and fabricated. Initially, an electrostatic induction model was established, and the principle of non-contact electrostatic potential measurement was analyzed to identify the key factors influencing the sensor's performance. Subsequently, the vibration mode of the tuning fork was simulated to determine the mechanical dimensions of the tuning fork and the driving frequency of the piezoelectric crystal. Additionally, the concept of enhancing the uniformity of the electric field near the sensor by employing a shield plate was proposed. Simultaneously, the optimal mechanical parameters of the shielding plate were determined through multi-physical field simulation to improve the sensor's linearity. Finally, a compact calibration device was designed to measure the key performance parameters of the non-contact electrostatic potential sensor. The results demonstrate that the sensor has a measurement range of -10 to 10 kV, a measurement accuracy better than ±3%, and a linearity of 0.46%. This work offers an alternative solution for non-contact potential measurement.

The effects of the electrical parameters, including storage capacitance, additional inductance, charging voltage, and electrode gap, on the shock wave induced by spark discharge in gas were experimentally investigated. The results showed that the shock waves induced by spark discharge conform to the attenuation law for weak spherical shock waves outside the spark core. The shock wave amplitude is approximately proportional to the electrode gap and storage energy and decreases with increasing inductance. The effect of the charging voltage on the shock wave amplitude can be almost ignored if the storage energy is the same. The average power in the first quarter cycle of spark discharge was found to be closely related to the shock wave amplitude. An empirical equation was given between the shock wave amplitude and the average discharge power, which provides convenient access to set appropriate electrical parameters to generate shock waves of specified amplitude induced by spark discharge.

针对传统最小点火能测试方法不适用于液体化学品气液共存工况的问题,提出了一种微量液体的蒸气最小点火能测试方法.首先设计了小容积实验装置及对应测试流程,通过样品实验确定了敏感电极间隙,并研究了样品量与搅拌对最小点火能测试的影响;测试了样品在不同温度条件下的最小点火能,结合电火花点火机理分析了样品温度与蒸气最小点火能的内在联系,为最小点火能最低值测定提供了指导;最后验证了微量方法的准确性及重复性.实验结果表明:微量测试方法能够有效测试气液共存工况下液体蒸气的最小点火能,且最小点火能测试值略高于高温蒸气工况,样品最小点火能的相对标准差小于 6.0%,重复性良好,为液体化学品的静电燃爆危险性评估提供了技术支撑.

绝热加速量热主要采用基于单一实验数据的模型拟合方法进行动力学预测,难以应用于未知机理反应和复杂反应.为此,通过数值模拟方法在绝热条件下产生n级反应与Kamal自催化反应数据,采用Vyazovkin和Friedman等转化率方法进行动力学求解;然后在不同起始温度和等温条件下,采用无模型动力学参数进行绝热和等温动力学预测,并与模拟数据对比.结果表明,绝热加速量热采用Vyazovkin方法预测最大相对误差为39.9％,Friedman方法预测最大误差超100％,前者更适合进行预测;建议在预测温度±40℃范围内进行实验测量.这为未知化学物质和复杂反应热失控风险评估及化工事故模拟等提供了有效手段.

At present, the kinetic approaches of accelerating rate calorimetry (ARC) are restricted to model-fitting methods, and the n-order reaction model is mainly used to estimate the kinetic parameters. However, the model-fitting method has the problems related to model selection and falling into a local optimum. To address these issues, kinetic analysis methods are introduced into ARC data treatment, and the kinetic parameters of complex reactions are solved by a model-free and model-fitting fusion method. First, the Friedman method is used to calculate the activation energy E-alpha. Then, A(alpha) and the overall mathematical function f(alpha) are obtained through the compensation effect. It provides references for the selection of the reaction model and initial values of model fitting, and the kinetic parameters are estimated through two-step model fitting. The fitting in steps realizes the decoupling of E and A and reduces the data dimensions. These help to reduce the chance of falling into a local optimum and lower the experience requirements. Finally, numeric simulations and the experimental results showed the effectiveness of the method.

Isoconversional method has been preliminarily applied in accelerating rate calorimetry (ARC) and achieved good results. However, it is a new subject and needs to be explored in depth. In this study, the Friedman and the Vyazovkin methods were applied to investigate the influences of thermal inertia on the activation energy estimation of the single-step reaction and autocatalytic reaction. The accuracy and adaptability of the two kinetic methods are compared, and the confidence intervals for activation energy estimated by the Friedman and the Vyazovkin methods are evaluated based on the corrected Student's distribution and F distribution. Finally, the validity of the simulation result is verified by the experiments. The results show that the sets of thermal inertia have different effects on the estimation of activation energy in single-step reaction and multi-step reaction, and the activation energies in multi-step reaction change obviously under different sets of thermal inertia. The thermal inertia increment of 0.03-0.5 and the Vyazovkin method are recommended. This study is helpful to promote the development of isoconversional methods applied for ARC data.

目的:针对太空科学载荷安装面缓慢与微小的温度变化测试要求,设计一种基于热电制冷器的真空高精度温度控制系统.方法:系统使用真空箱与低温恒温槽模拟真空低温测试环境,采用热电制冷器作为温度发生器件,设计环境导冷与加热棒制热的组合方式对热端进行散热,并结合抗饱和积分PID算法进行温度控制.结果:该温度控制系统恒温控制误差范围在 ±0.008℃以内,匀速温升控制可达到最低0.025℃/1000 s,速率控制误差范围在±0.002℃/1000 s以内.结论:所设计温度控制系统满足科学载荷的匀速温升测试需求.

To accurately measure electrostatic discharge energy, a resistive-capacitive voltage discharge approach was used to measure the parasitic capacitance in a circuit. As a result, an output-stage parasitic capacitance in the circuit during the discharge process and a non-negligible storage-stage parasitic capacitance during the charging process were identified. By comparing the data obtained from the resistive-capacitive discharge voltage model and spark current RCL circuit model, the maximum relative deviation from the total circuit capacitance was 5.4% for both approaches. A model based on graded-stage parasitic capacitance was established to analyze the effect of this capacitance on discharge energy. The energy stored in the charging process increased because of the storage-stage parasitic capacitance, and the discharge energy decreased because of the output-stage parasitic capacitance. The energy calculated by the graded parasitic capacitance model was larger than that calculated by the single-stage parasitic capacitance model, with a maximum relative deviation of 36.7% under the test conditions. The smaller the charging capacitor, the more evident the effect of the parasitic capacitance on the discharge energy.

目的:实现火花能量的精确计算.方法:建立一种包含可变火花电阻与火花电感的等效放电模型,搭建一种宽放电能量范围的静电火花发生装置,对比不同放电能量下拟合曲线与实际放电曲线差异.结果:在欠阻尼情况下,通过模型计算的放电能量与UI积分法计算的放电能量偏差在0.6％～3.2％范围内;在过阻尼情况下,形成稳定火花通道时间段内放电能量占全部放电能量比例约95％,在该时间段内,通过模型计算的放电能量与UI积分法计算的放电能量偏差在0.2％～4.3％范围内.结论:通过可变火花电阻与火花电感的等效放电模型可实现火花能量更精确的计算.

A series of electrostatic sparks at different energies are triggered by different methods in testing the minimum ignition energy (MIE) of dust clouds. It is necessary to investigate the difference between actual spark energies and MIEs under different triggering methods. A multi-energy spark generating circuit combined with high voltage relay (HVR) triggering and electrode movement (EM) triggering was set up to study the effects of triggering types and inductance loads. The first current peak was proposed together with damping ratio and angular frequency of spark current to evaluate the reliability of the experimental results. Results showed that the deviation of spark energy release efficiency between the two triggering types is about 5%-25% when the storage energy was 34 mJ, 110 mJ, 340 mJ and 1100 mJ, which was not enough to cause the difference in the magnitude of MIE. The MIEs of clouds of lemon powder and sea buckthorn powder are consistent using the two triggering types. But the MIE of clouds of lycopodium triggered by EM without inductance is higher than that triggered by HVR. It indicates different triggering types may lead to different MIE results when testing fine dust even if the actual released energy is almost the same. The spark energy release efficiency without inductance is greater than or equal to that with inductance. However, the MIE of lycopodium clouds dropped from 75-90 mJ with no inductance, to 8-10 mJ with a 1 mH inductance. The MIEs of clouds of lemon powder and sea buckthorn powder showed similar trends.

Electrostatic sparks are considered to be mainly resistive. However, experimental results show that the oscillation frequencies and amplitude attenuation of fitted waveform based on underdamped oscillation have discrepancies comparing with measured voltage waveform if spark gap is replaced by a pure resistance. To study the phenomenon, a simple device was built for strong electrostatic spark discharges of short discharge times. An equivalent discharge model including variable spark resistance and spark inductance was made to simulate the spark discharge. By comparative experiments under different ambient humidity, electrode gaps and charging capacitances, an exponential relationship between spark resistance and spark inductance with discharge time was verified.

针对敞口体系燃爆辨识人工观测存在安全风险、单一传感器容易误判问题,提出一种基于光强和温度的多传感器联合燃爆辨识方法.采用光敏传感器阵列增大有效检测面积,避免单一传感器检测的偶然性;使用自适应加权算法处理光强冗余数据,消除背景光强变化带来的干扰;将光强和温度的特征数据提取后进行初步决策和构造概率分配函数,经由D-S证据理论进行决策层融合选择最可信的初步决策作为辨识结果.在嵌入式平台上对辨识方法进行实现,实验表明多传感器联合燃爆辨识方法的辨识准确率高达99.4％,实现了燃爆自动化检测.

为了清晰认知和评估化学反应过程,明确反应优化的方向,建立了基于反应量热仪和在线红外联用的方法,用于原位检测釜式反应系统.该方法利用反应量热仪对釜内样品温度等变量进行测量及精准控制,并结合在线红外光谱仪对物质官能团变化进行的连续实时检测,可同时获取化学反应过程实时放热热流、热转化率等热力学信息以及样品中反应物、产物比例随时间变化的趋势.通过测定比较不同工艺条件下的反应结果,考察工艺条件对反应进程、最终产物的影响.将该联用方法应用于噻吩酯合成工艺的结果表明,调整工艺温度可改善最终产物质量,同时反应热危险性可控.这种基于在线红外与量热技术联用的原位反应过程研究方法,可应用于化学反应过程的研究并有效实现对反应过程的认知.

针对ADC型测温电桥因电路结构复杂、集成度高、非线性误差来源多样,导致现有误差修正方法效果不佳的问题,提出了一种基于误差来源分析的修正方法.根据ADC型测温电桥原理定量分析了电路中运算放大器共模抑制比、正反向电流不匹配度对非线性误差的贡献,运用RBC开展了这两个误差源的最大似然估计及修正,并对剩余残差进行了多项式拟合,实现了非线性误差修正;基于自制ADC型测温电桥及RBC对上述修正方法进行了验证,实验结果表明:所提方法修正后的最大非线性误差为－1.77×10 －5,相对于传统非线性修正方法的最大非线性误差－3.57×10 －5有了显著提升.