Tairan Fu

Study in performance analysis of China Urban Emergency Response System based on Petri net.

Abstract Urban Emergency Response System (UERS) is a modernization symbol of a city. With acceleration of urbanization process and constant expansion of city size in China, China cities must respond to various emergencies timely and effectively to satisfy urban residents’ needs for public security. In recent years, many China cities made trials and efforts in setting up and improving the UERS. At the same time, the China government began to build Emergency Response Systems (ERS) in some cities to deal with various possible emergencies. In this paper, using Petri net (PN), we study the performance of China typical UERS and establish its PN model for performance analysis. Based on the Markov chain (MC) of the model, the performance of China typical UERS is analyzed. Results from our simulation are in conformity with practical operation of China current UERS.

Temperature Measurements of Diesel Fuel Combustion With Multicolor Pyrometry

Optical diagnostics techniques to measure diesel combustion flame temperatures are useful for evaluation and control of combustion processes. In this paper, diesel combustion flame temperatures are measured based on a multicolor pyrometry method respectively adopting an optical fiber spectrometer and a color charge coupled device (CCD). The intensity ratios for various wavelengths/wavebands are utilized as the analytical variables to deduce the temperatures to avoid the need to calibrate each system for the specific geometry conditions. The measured multicolor data can determine the temperature T and the soot factor KL. Extra data collected at many wavelengths is used to reduce the noise and random fluctuations in the measurements. To improve the solving precision, a data-processing method based on the least-squares technique is proposed to fit the data for approximate solutions. Verification experiments using the multicolor pyrometry were conducted in a 54―120 kW test furnace with diesel fuel. Data for 16 wavelengths detected by a fiber optic spectrometer from a diesel flame is analyzed to determine how to choose a suitable combination of three wavelengths for three-color pyrometry. The CCD-based three-color measurements, which would be much more practical in field measurements, are compared with the spectrometer-based results.

Two-color optical charge-coupled-device–based pyrometer using a two-peak filter

A two-color optical charge-coupled-device (CCD)-based pyrometer was developed using a multipeak interference filter with a color CCD sensor to measure multicolor signals with specified wavelengths. The effective and simple method adjusts the fixed spectrum response characteristics of a color CCD to allow improved temperature measurements. This pyrometer system not only has the advantage of traditional two-color (two-wavelength) pyrometry, but also overcomes the restrictions of color CCDs that can only be applied in waveband measurements. The measurement performance of the system using a two-peak filter (λ(1)=643 nm, λ(2)=564 nm) was evaluated by blackbody experiments. The results show that the low temperature detection limit is increased about 200 K with an increase in the sensitivity of the measured signals compared with the original system without two-peak filter [Fu, et al., Opt. Laser Technol. 42, 586 (2010)]. And the effective temperature range is also increased when T > 1233 K. The measured ratio C(R)/C(G) is monotonically relative to the temperature, which simplifies the measurements. The temperature sensitivity of 2.49 is larger and more uniform than the temperature sensitivity of 1.36 in the previous original system. Thus, the measurement performance of the new system is greatly improved. Finally, as an application, the surface temperature distribution of stainless steel sample in hot environments was determined by this new CCD-based pyrometer. The results agree well with the spectrometer-based results and further verify the applicability of the new system.

The set-up of a vision pyrometer

The paper presents a new radiation pyrometer, a vision pyrometric device based on a commercial digital colour camera and SUNPRO software, which converts the calibrated commercial digital colour camera into a scientific instrument for temperature measurement. We introduce the calibration experiments and the principle of this vision pyrometer, and the application of the vision pyrometer is illustrated in the specific examples. The analysis shows that the vision pyrometer established in this paper is convenient and promising and will be able to realize real-time measurements of two-dimensional temperature fields.

Temperature measurements using multicolor pyrometry in thermal radiation heating environments

Temperature measurements are important for thermal-structural experiments in the thermal radiation heating environments such as used for thermal-structural stress analyses. This paper describes the use of multicolor pyrometry for the measurements of diffuse surfaces in thermal radiation environments that eliminates the effects of background radiation reflections and unknown emissivities based on a least-squares algorithm. The near-infrared multicolor pyrometer had a spectral range of 1100-2400 nm, spectrum resolution of 6 nm, maximum sampling frequency of 2 kHz, working distance of 0.6 m to infinity, temperature range of 700-1700 K. The pyrometer wavelength response, nonlinear intensity response, and spectral response were all calibrated. The temperature of a graphite sample irradiated by quartz lamps was then measured during heating and cooling using the least-squares algorithm based on the calibrated irradiation data. The experiments show that higher temperatures and longer wavelengths are more suitable for the thermal measurements in the quartz lamp radiation heating system. This analysis provides a valuable method for temperature measurements of diffuse surfaces in thermal radiation environments.

A steady-state measurement system for total hemispherical emissivity

A steady-state calorimetric technique was developed for measuring the total hemispherical emissivity of a conductive material. The system uses a thin strip of the conductive sample electrically heated by alternating current to high temperatures in a vacuum chamber. The emissivity was measured in a central region of the sample with an approximately uniform temperature distribution. Considering the influences of the gray body assumption, wire heat losses, effects of residual gas and conductive heat loss from the region to the rest of the strip, the emissivity was accurately determined by solving the inverse one-dimension steady-state heat transfer problem. The emissivities of various metal samples (nickel and 45# steel) were measured to verify the system accuracy. And the results were then analyzed to estimate the relative errors of emissivity arising from the gray body assumption, wire heat losses, effects of residual gas, non-uniform temperature distribution and the measurement uncertainty of emissivity. In the temperature range from 700 to 1300 K, the accuracy is acceptable for practical applications within the total measurement uncertainties of 1.1%. To increase the system applicability, some issues related to sample specifications, heating power control and temperature uniformity of sample test section were discussed. Thus, this system can provide accurate measurements of the total hemispherical emissivity of conductive samples at high temperatures.

Fast fiber-optic multi-wavelength pyrometer

A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, Δλ(CCD) = 30 nm and Δλ(InGaAs) = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements.

Improvements to the three-color optical CCD-based pyrometer system

We put forward an improved three-color measurement scheme with a color CCD sensor using the combination of effective wavelengths and blackbody calibrations. The process of effective wavelengths realizes the separation of the emissivity function from the measurement integral equation. This improved method not only effectively avoids errors arising from the traditional process adopting the basic wavelengths, but also simplifies the complex integral calculations. For a blackbody or graybody, the measurement performance of the pyrometer was experimentally investigated from the point of the temperature sensitivity. The results show that narrowing the spectrum bandwidth with different bandpass spectral filters may improve the temperature sensitivities. The spectrum adjustment not only makes the linear emissivity more suitable in the narrower waveband, but also reduces the numerical uncertainty of the effective wavelengths. For nongray objects, the effects of the numerical uncertainty of the effective wavelengths to measurements were quantificationally evaluated at different measurement conditions (different temperatures, emissivities, and spectrums). The results indicate that the reference values of 584, 555, and 511nm or 607, 560, and 506nm of the effective wavelengths are reasonable for the present system with the modified spectral response using Filter 1 or Filter 2. The maximum calculation errors arising from the reference effective wavelengths are less than 1.6%. In this paper, the technical realization steps of the improved method are also described. The measurement experiments of a metal sample in hot environments were carried out to further verify the applicability of this improved CCD-based pyrometer. The results agreed well with the spectrometer-based results.

Theoretical evaluation of measurement uncertainties of two-color pyrometry applied to optical diagnostics

We present a theoretical analysis of two-color pyrometry applied to optical diagnostics. A two-color pyrometer built with a single CCD is advantageous due to the simple system design. We evaluate the possibility and degree of ill-conditionness on the basis of measurement uncertainties for different measurement approaches of this two-color system. We classify measurement approaches. The corresponding ill-conditionness criterion is established. The greater the criterion value is, the worse the ill-conditioned degree of solution is. So, the optimum choice of measurement approach for the two-color system is achieved through intercomparison of the criterion values. Numerical examples are also given to illustrate this point. The theoretical analysis not only provides an effective way of evaluating different measurement approaches, but also may help us to better understand the influences that determine the choices between wavelength/waveband measurements and calibration/noncalibration modes for temperature and soot distribution.

The theoretical prediction analyses of the measurement range for multi-band pyrometry

In the applications of multi-band pyrometry, the coupled correlation of multi-channel measurement information is a distinct characteristic. Considering this point, in order to realize the non-distortion and effective measurement, the theoretical differentiation formula of the measurement range is put forward in this paper. It may estimate not only the temperature range, but also the emissivity parameter range for the specific measured surface. Then, the corresponding simulation results are given. For an exploited multi-band pyrometer, the theoretical estimations are verified through blackbody measurement experiments. Therefore, the analyses in the paper provide the necessary theoretical supports for the design and application of a multi-band pyrometer.