Deflagration characteristics of freely propagating flames in magnesium hydride dust clouds

The flame propagation processes of MgH_(2)dust clouds with four different particle sizes were recorded by a high-speed camera.The dynamic flame temperature distributions of MgH_(2)dust clouds were reconstructed by the two-color pyrometer technique,and the chemical composition of solid combustion residues were analyzed.The experimental results showed that the average flame propagation velocities of 23μm,40μm,60μm and 103μm MgH_(2)dust clouds in the stable propagation stage were 3.7 m/s,2.8 m/s,2.1 m/s and 0.9 m/s,respectively.The dust clouds with smaller particle sizes had faster flame propagation velocity and stronger oscillation intensity,and their flame temperature distributions were more even and the temperature gradients were smaller.The flame structures of MgH_(2)dust clouds were significantly affected by the particle sinking velocity,and the combustion processes were accompanied by micro-explosion of particles.The falling velocities of 23μm and 40μm MgH_(2)particles were 2.24 cm/s and 6.71 cm/s,respectively.While the falling velocities of 60μm and 103μm MgH_(2)particles were as high as 15.07 cm/s and 44.42 cm/s,respectively,leading to a more rapid downward development and irregular shape of the flame.Furthermore,the dehydrogenation reaction had a significant effect on the combustion performance of MgH_(2)dust.The combustion of H_(2)enhanced the ignition and combustion characteristics of MgH_(2)dust,resulting in a much higher explosion power than the pure Mg dust.The micro-structure characteristics and combustion residues composition analysis of MgH_(2)dust indicated that the combustion control mechanism of MgH_(2)dust flame was mainly the heterogeneous reaction,which was affected by the dehydrogenation reaction.

True-temperature inversion algorithm for a multi-wavelength pyrometer based on fractional-order particle-swarm optimization

Herein,a method of true-temperature inversion for a multi-wavelength pyrometer based on fractional-order particle-swarm optimization is proposed for difficult inversion problems with unknown emissivity.Fractional-order calculus has the inherent advantage of easily jumping out of local extreme values;here,it is introduced into the particle-swarm algorithm to invert the true temperature.An improved adaptive-adjustment mechanism is applied to automatically adjust the current velocity order of the particles and update their velocity and position values,increasing the accuracy of the true temperature values.The results of simulations using the proposed algorithm were compared with three algorithms using typical emissivity models:the internal penalty function algorithm,the optimization function(fmincon)algorithm,and the conventional particle-swarm optimization algorithm.The results show that the proposed algorithm has good accuracy for true-temperature inversion.Actual experimental results from a rocket-motor plume were used to demonstrate that the true-temperature inversion results of this algorithm are in good agreement with the theoretical true-temperature values.

The Theoretical Analysis of Multi-wavelength Pyrometer:Check and Autosearch for Emissivity General Expression

In general, the dependence of the logarithm of the emissivity upon wavelength is usually used in the treatment of data measured by multi-wavelength pyrometer. In this paper, the suitability of this expression for different materials has been examined. Further more, an effective method for automatically searching the mathematical model between emissivity and wavelength has been procsed. The calculated results show that the accuracy is improved by using this data treatment method.

Performance evaluation and optimization design of photoelectric pyrometer detection optical system

The measurement and control of high temperature play very important roles in national defense,military,scientific experiments,industrial and agricultural production.Photoelectric pyrometer is one of the important radiation thermometers for non-contact temperature measurement.It has an important application in the field of high temperature measurement,and its performance directly affects the accuracy of temperature measurement.By improving the design of the detection optical system of the photoelectric pyrometer,the imaging performance of the photoelectric pyrometer can be improved effectively,and the temperature measurement accuracy can be improved.In this paper,the temperature measurement principle of photoelectric pyrometer,the wo rking principle of the detection optical system and the composition of the system are introduced.The optical components that affect the imaging of the optical system of the photoelectric pyrometer are analyzed.The optical pyrometer detection optical system is simulated by ZEMAX software,based on the analysis results,the Modulation Transfer Function(MTF)and the spot Diagram are used as the main evaluation criteria to optimize the design of the objective lens of the photoelectric pyrometer detection optical system.The imaging performance of the photoelectric pyrometer detection optical system and the accuracy of temperature measurement of the photoelectric pyrometer are improved by optimization design of the detection optical system.

Explosion temperature mapping of emulsion explosives containing TiH_(2)powders with the two-color pyrometer technique

In the study,the two-color pyrometer technique was used to measure the transient temperature field of emulsion explosives with different contents of TiH_(2)powders.The experimental results showed that the introduction of TiH_(2)powders could significantly increase the explosion temperature and fireball duration of emulsion explosive.When emulsion explosives were ignited,the average explosion temperature of pure emulsion explosive continuously decreased while emulsion explosives added with TiH_(2)powders increased at first and then decreased.When the content of TiH_(2)powders was 6 mass%,the explosion average temperature reached its maximum value of 3095 K,increasing by 43.7%as compared with that of pure emulsion explosive.In addition,the results of air blast experiment and explosion heat test showed that the variation trends of shock wave parameters,explosion heat and theoretical explosion temperature of emulsion explosives with different contents of TiH_(2)powders were basically consistent with that of explosion temperature measured by the two-color pyrometer technique.In conclusion,the two-color pyrometer technique would be conducive to the formula design of emulsion explosive by understanding the explosion temperature characteristics.

Experimental Study on Light Flash Radiant Intensity Generated by Strong Shock 2A12 Aluminum Plate

In order to study the light flash radiant intensity produced by strong shock on a 2A12 aluminum target at the same projectile incidence angles and different shock velocities,experimental measurements were conducted for light flash phenomena of a 2A12 aluminum projectile impacting a 2A12 aluminum target under the conditions of different impact velocity and the same projectile incidence angles of 45° by using an optical pyrometer measurement system and a two-stage light gas gun loading system.Experimental results show that the peak values of the light flash radiant intensity for the wavelength of 550 nm are largest in the wavelength ranges of 600 nm,650 nm and 700 nm when a 2A12 aluminum projectile impacts a double-layer 2A12 aluminum plate in the present experimental conditions.

Research on the Explosion Temperature Response of Fuel Air Explosive Measured by Colorimetric Pyrometer

An infrared colorimetric radiation thermometrical system was established based on the theory of optical radiation. The dynamic temperature history of fuel air explosive (FAE) was measured to obtain the temperature responses of primary initiation FAE and secondary initiation FAE in real time. And the characteristics of their temperature history curves were compared and analyzed. The results show that the primary initiation FAE has higher explosion temperature and longer duration compared to the secondary initiation FAE.

Study of the Performance of a Streaked Optical Pyrometer System for Temperature Measurement of Shocked Materials

A streaked optical pyrometer （SOP） is developed and calibrated for the measurement of the temperature of shocked materials. In order to achieve a higher relative sensitivity, a onechannel scheme is adopted for the system. The system is calibrated with a shocked step-shaped aluminum sample in the SG-III prototype laser facility. The relation between the count number in the detection system and the sample temperature is thus obtained, which can be adopted to infer the temperature of any shocked materials in future experiments.

New Optical Fiber Pyrometer for Overheating Gas Temperature

An optical fiber pyrometer prototype has been developed for accurate measurement of overheating gas temperature.The optical fiber pyrometer and its technique could have the potential of measuring temperature up to 2 000 ℃. The operation principle of the pyrometer is based on Planck's law and Stephen-Boltzmann's law. The test results are presented.

Optical Fiber Pyrometer Applied in IC Engine

Based on the theory of thermal radiation,a contact type optical fiber pyrometer applied in IC engine is put forward.It is composed of three parts:a blackbody probe,optical system,electrical process system.The key technology of design is discussed.Experiment is given to prove that the pyrometer has much higher responsive speed,distinguishability and much longer running life than other pyrometers.

New Pyrometer with Double Y-type Optical Fibers

Abstract: A new pyrometer, which can solve the affection of emissivity change in temperature measuring, has been developed by double Y - type optical fibers. The mathematical model of the new pyrometer is presented and the errors of the new pyrometer are analyzed.

New Colorimetric Pyrometer with Optical Fiber Link

Based on the concept of thermo-radiation theory,the principle of non-contact temperature measurement with optical fiber is introduced.The new pyrometer operates on the basis of two-way temperature signal division calculation via microcomputer signal processing system.Its design method and smart construction of the electro-optical system possess such advantages as high measurement accuracy,freedom from electric interference and other perturbations as well as flexible applications.The indication scale of the measured temperature and experiment results are given in this paper.

Wireless Infrared Pyrometer with Fiber Optic: Construction and Processing Algorithms

In this paper, developed wireless portable infrared pyrometer with dual channel fiber optic is described. The pyrometer measures surface temperature in wide infrared spectral range of 2 - 25 um. A data processing algorithm based on the methods of synchronous detection providing

4-22 Development and Test of an Ultrafast eight-channel Pyrometer for Temperature Diagnostics of High-energy-density Matter

A study of the fundamental properties of high-energy-density (HED) matter is of considerable important as it has wide application to various branches of the basic and applied science. The study will enable one to probe the validity of existing theories on stellar formation and evolution, compressibility of inertial fusion targets and check the correctness of existing models for strongly coupled high density plasma[1;2].

排气阀Pyromet31V合金混晶组织研究

Pyromet31V合金具有优异的蠕变断裂强度、抗热腐蚀和抗热疲劳等性能,是制备汽车发动机排气阀的关键材料。采用OM和SEM研究排气阀不同区域内的晶粒组织、晶内γ’相和晶界碳化物形貌及合金混晶组织的演化行为。结果表明:排气阀头部中心区域为细晶区,而外部为粗晶区,中间部位为混晶区,各区域内晶粒尺寸呈双峰分布;混晶组织区域内γ’析出相及M_(23)C_(6)碳化物分布与细晶区和粗晶区的相当,没有出现明显的成分偏析。进一步观察对比变形前后的晶粒组织发现,排气阀头部混晶组织形貌与原始棒料中晶粒组织密切相关,表明变形工艺对其晶体组织结构影响较小。

Design, performance and application of a line-imaging velocity interferometer system for any reflector coupled with a streaked optical pyrometer system at the Shenguang-Ⅱ upgrade laser facility

The velocity interferometer system for any reflector(VISAR) coupled with a streaked optical pyrometer(SOP) system is used as a diagnostic tool in inertial confinement fusion(ICF) experiments involving equations of state and shock timing.To validate the process of adiabatically compressing the fuel shell through precise tuning of shocks in experimental campaigns for the double-cone ignition(DCI) scheme of ICF, a compact line-imaging VISAR with an SOP system is designed and implemented at the Shenguang-II upgrade laser facility. The temporal and spatial resolutions of the system are better than 30 ps and 7 μm, respectively. An illumination lens is used to adjust the lighting spot size matching with the target size. A polarization beam splitter and λ/4 waveplate are used to increase the transmission efficiency of our system. The VISAR and SOP work at 660 and 450 nm, respectively, to differentiate the signals from the scattered lights of the drive lasers. The VISAR can measure the shock velocity. At the same time, the SOP system can give the shock timing and relative strength. This system has been used in different DCI campaigns, where the generation and propagation processes of multi-shock are carefully diagnosed.

Measurement of thermal expansion coefficient of nonuniform temperature specimen

A new technique is developed to measure the longitudinal thermal expansion coefficient of C/C composite material at high temperature. The measuring principle and components of the apparatus are described in detail. The calculation method is derived from the temperature dependence of the thermal expansion coefficient. The apparatus mainly consists of a high temperature environmental chamber, a power circuit of heating, two high-speed pyrometers, and a laser scanning system. A long solid specimen is resistively heated to a steady high-temperature state by a steady electrical current. The temperature profile of the specimen surface is not uniform because of the thermal conduction and radiation. The temperature profile and the total expansion are measured with a high-speed scanning pyrometer and a laser slit scanning measuring system, respectively. The thermal expansion coefficient in a wide temperature range （1000 - 3800 K） of the specimen can therefore be obtained. The perfect consistency between the present and previous results justifies the validity of this technique.

Method for changing brightness temperature into true temperature based on twice recognition method

The channel output of a multi-wavelength pyrometer is the brightness temperature rather than the true temperature. Twice recognition method is put forward to change the brightness temperatures of a multiwavelength pyrometer into the true temperatures of targets. Using the data offered by Dr. F. Righini, the experimental results show that the difference between the calculated true temperature based on twice recognition method and the real true temperature is within ±20 K. The method presented in this paper is feasible and effective for the true temperature measurement of targets.

Experimental study on electrical resistivity measurement of a specimen at high temperature

A new technique is developed to measure the electrical resistivity of conductor with a nonuniform tem- perature profile. The calculation method is derived from the temperature dependence of the electrical resistivity. The apparatus consists mainly of a high temperature environmental chamber, a power circuit of heating, a twenty-wavelength pyrometer, and a scanning pyrometer. After getting the resistance from the voltage drop of the specimen, the electrical resistivity in a wide temperature range of the specimen can be obtained by our calculation model. Preliminary results of the electrical resistivity of SRM 8424 over a wide temperature range （1000-3000 K） are presented. The perfect consistency between the measurement results and the nominal values justifies the validity of this technique.

Conjugate calculation of a film-cooled blade for improvement of the leading edge cooling configuration

Great efforts are still put into the design process of advanced film-cooling configurations.In particular,the vanes and blades of turbine front stages have to be cooled extensively for a safe operation.The conjugate calculation technique is used for the three dimensional thermal load prediction of a fim-cooled test blade of a modern gas turbine.Thus,it becomes possible to take into account the interaction of internal flows,external flow,and heat transfer without the prescription of heat transfer ooefficients.The focus of the investigation is laid on the leading edge part of the blade.The numerical model consists of all internal flow passages and cooling hole rows at the leading edge.Furthermore,the radial gap flow is also part of the model.The comparison with thermal pyrometer measurements shows that with respect to regions with high thermal load a qualitatively and quantitatively good agreement of the conjugate results and the measurements can be found.In particular,the region in the vicinity of the mid-span section is exposed to a higher thermal load,which requires further improvement of the cooling arrangement.Altogether the achieved results demonstrate that the conjugate calculation technique is applicable for reasonable prediction of three-dimensional thermal load of complex cooling configurations for blades.