Predicting the emissive power of hydrocarbon pool fires

The emissive power (E) of a flame depends on the size of the fire and the type of fuel. In fact, it changes significantly over the flame surface: the zones of luminous flame have high emittance, while those covered by smoke have low E values. The emissive power of each zone (that is, the luminous or clear flame and the non-luminous or smoky flame) and the portion of total flame area they occupy must be assessed when a two-zone model is used. In this study, data obtained from an experimental set-up were used to estimate the emissive power of fires and its behaviour as a function of pool size. The experiments were performed using gasoline and diesel oil as fuel. Five concentric circular pools (1.5, 3, 4, 5 and 6m in diameter) were used. Appropriate instruments were employed to determine the main features of the fires. By superimposing IR and VHS images it was possible to accurately identify the luminous and non-luminous zones of the fire. Mathematical expressions were obtained that give a more accurate prediction of E(lum), E(soot) and the average emissive power of a fire as a function of its luminous and smoky zones. These expressions can be used in a two-zone model to obtain a better prediction of the thermal radiation. The value of the radiative fraction was determined from the thermal flux measured with radiometers. An expression is also proposed for estimating the radiative fraction.     

Reproduction of emissive power (self-calibration) using an emissive diode

A new method of self-calibration of the emissive power of an emissive diode is presented. The method involves determining the overall volume of the thermal and emissive power released in a semiconductor-type radiating structure in the non-steady-state mode. According to a preliminary analysis, the method possesses high metrological characteristics. Translated from Izmeritel’naya Tekhnika, No. 8, pp. 22–23, August, 1996.     

Generating data with prescribed power spectral density

Data generation is straightforward if the parameters of a time series model define the prescribed spectral density or covariance function. Otherwise, a time series model has to be determined. An arbitrary prescribed spectral density will be approximated by a finite number of equidistant samples in the frequency domain. This approximation becomes accurate by taking more and more samples. Those samples can be inversely Fourier transformed into a covariance function of finite length. The covariance in turn is used to compute a long autoregressive (AR) model with the Yule-Walker relations. Data can be generated with this long AR model. The long AR model can also be used to estimate time series models of different types to search for a parsimonious model that attains the required accuracy with less parameters. It is possible to derive objective rules to choose a preferred type with a minimal order for the generating time series model. That order will generally depend on the number of observations to be generated. The quality criterion for the generating time series model is that the spectrum estimated from the generated number of observations cannot be distinguished from the prescribed spectrum.     

Calculation of the power spectral density from surface profile data

The power spectral density (PSD), in its two-dimensional form, has been designated as the preferred quantity for specifying surface roughness on a draft international drawing standard for surface texture. The correct calculation of the one-dimensional PSD from discrete surface profile data is given, and problems in using fast Fourier-transform routines that are given in some of the standard reference books are flagged. The method given here contains the correct normalizing factors. Two ways to reduce the variance of the PSD estimate are suggested. Examples are shown of the variance reduction possible in the PSD's.     

Coupling dynamic blow down and pool evaporation model for LNG

Treating the dynamic effects of accidental discharges of liquefied natural gas (LNG) is important for realistic predictions of pool radius. Two phenomena have important influence on pool spread dynamics, time-varying discharge (blow down) and pool ignition. Time-varying discharge occurs because a punctured LNG tanker or storage tank drains with a decreasing liquid head and decreasing head-space pressure. Pool ignition increases the evaporation rate of a pool and consequently decreases the ultimate pool area. This paper describes an approach to treat these phenomena in a dynamic pool evaporation model.

The pool evaporation model developed here has two separate regimes. Early in the spill, momentum forces dominate and the pool spreads independently of pool evaporation rate and the corresponding heat transfer rate. After the average pool depth drops below a minimum value, momentum forces are largely dissipated and the thin edges of the pool completely evaporate, so pool area is established by the heat transfer rate. The maximum extent of a burning pool is predicted to be significantly less than that of an unignited pool because the duration of the first regime is reduced by higher heat transfer rates. The maximum extent of an LNG pool is predicted to be larger upon accounting for blow down compared with using a constant average discharge rate. However, the maximum pool extent occurs only momentarily before retreating.     

液氮洗联产LNG流程模拟计算

部分以煤为原料合成氨的粗原料气中含有一定量的甲烷,常规的做法是将其在液氮洗工序粗分离出来作为燃料气或者返回变换工序。随着天然气价格的上涨以及市场预期的升温,许多新建以及改造项目有意于将其中的甲烷回收处理生产合格的液化天然气(LNG)。简介液氮洗联产LNG的工艺流程,对比了常规液氮洗流程与液氮洗联产LNG流程的不同,通过ASPEN软件针对某厂原料气,对液氮洗联产液化天然气的工艺流程进行模拟,并得出了模拟数据。同时,对氮洗塔塔釜液体的不同处理方式以及系统冷剂的选择进行了对比分析。     

Precision wide-aperture calorimetric transducer of mean laser emissive power and associated measurements systems

The problem of increasing the speed and level of the measurable mean laser emissive power by means of gradient calorimeters while preserving high precision is considered. The characteristics of the devices and of measurement systems based on these types of devices are presented. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 35–39, March, 2000.     

脉象采集方法及功率谱分析研究

在对压力脉搏波的分析及中医理论研究基础上,提出了一种多点三维动态压力脉搏波的采集方案,以获得有效的脉象数据用于模拟传统中医诊脉.根据信号功率谱的特点,在数据采集过程中结合了功率谱分析手段动态提取脉象的位置及力度特征,同时通过实验得出脉象变化与压力脉搏波功率谱变化的内在相关性,从而得到一种简单有效的脉象特征分析和提取的实验和研究方法.     

Incident analysis of Bucheon LPG filling station pool fire and BLEVE

An LPG filling station incident in Korea has been studied. The direct cause of the incident was concluded to be faulty joining of the couplings of the hoses during the butane unloading process from a tank lorry into an underground storage tank. The faulty connection of a hose to the tank lorry resulted in a massive leak of gas followed by catastrophic explosions. The leaking source was verified by calculating the amount of released LPG and by analyzing captured photos recorded by the television news service. Two BLEVEs were also studied.     

Initial fuel temperature effects on burning rate of pool fire

The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs.     

液化天然气汽车双动力循环系统

在分析液化天然气(LNG)冷能构成的基础上,提出一种由LNG开式朗肯循环和天然气内燃机循环组成的LNG汽车双动力循环系统,并对系统相关参数进行了计算分析.结果表明,该系统不仅可以回收LNG冷量,而且可以利用LNG冷量(火用)的做功能力输出动力,系统可用能较普通LNG汽车增加9.82%,充分利用了LNG宝贵的冷能资源,具有较好的节能环保效果.     

液化天然气冷能利用发电技术浅析

阐述了国内外LNG利用的形势,论述了LNG作为燃料的优势.通过分析LNG冷量利用原理及对LNG进行的分析,得出回收LNG冷量发电不仅有效利用能源,而且减少机械制冷造成的大量电能消耗,具有可观的经济效益和社会效益.对国内外利用LNG冷量发电方式进行总结分类,具体给出一些典型流程图和成功的应用范例.     

Optimization of power generating thermoelectric modules utilizing LNG cold energy

A theoretical investigation to optimize thermoelectric modules, which convert LNG cold energy into electrical power, is performed using a novel one-dimensional analytic model. In the model the optimum thermoelement length and external load resistance, which maximize the energy conversion ratio, are determined by the heat supplied to the cold heat reservoir, the hot and cold side temperatures, the thermal and electrical contact resistances and the properties of thermoelectric materials. The effects of the thermal and electrical contact resistances and the heat supplied to the cold heat reservoir on the maximum energy conversion ratio, the optimum thermoelement length and the optimum external load resistance are shown.     

Design of Rankine Cycles for power generation from evaporating LNG

Of the different ways of using the cold available from the large scale evaporation of LNG the generation of electric power, using the Rankine Cycle, appears the most practical. Fourteen such plants have so far been installed in Japan. The present study was undertaken for a plant at Zeebrugge. Six different cycles using nine different refrigerants and mixtures were examined. The results (Tables 2 and 3) show the importance of using a heat source with the highest possible temperature. No one refrigerant is ideal for all configurations Environmental and safety considerations also affect the choice of refrigerant.     

A summary of some experimental data on LNG safety

In a recent paper, Luketa-Hanlin reviewed the information in the public domain related to LNG safety. The purpose of this paper is to supplement that work by providing a summary of the experimental information that Advantica has collected on LNG behaviour over the course of the last 30 years. This summary includes previously unpublished information obtained as a result of a number of collaborative projects. Subjective comments are also made on the status of modelling for each of the topic areas and, in a discussion, views are provided on those areas where there are currently gaps that may have a major impact on evaluating the individual or societal risks associated with LNG operations.     

Time-domain calculation of spectral centroid from backscattered ultrasound signals

Spectral centroid estimation from backscattered ultrasound RF signals is the preliminary step for quantitative ultrasound analysis in many medical applications. The traditional approach of estimating the spectral centroid in the frequency domain takes a long time because discrete Fourier transform (DFT) processing for each RF segment is required. To avoid this, we propose time-domain methods to estimate the spectral centroid in this paper. First, we derive the continuous-time-domain equations for the spectral centroid estimation using Parseval's theorem and Hilbert transform theory. Then, we extend the method to the discrete-time domain to ease the implementation while maintaining the same accuracy as the calculation in the frequency domain. From the result, we observe that it is not practical to apply the discrete-time equations directly, because a high sampling rate is needed to approximate the time derivative in the discrete-time domain. Therefore, we also derive the feasible version of the discrete-time equations using a circular autocorrelation function, which has no constraints on the sampling rate for real RF signals acquired from pulse-echo ultrasound systems. Simulation results using numerical phantoms show that the time-domain calculation is approximately 4.4 times faster on average than the frequency-domain method when the software's built-in functions were used. The average estimation error compared with that of the frequency-domain method using DFT is less than 0.2% for the entire propagation depths. The proposed time-domain approach to estimate the spectral centroid can be easily implemented in real-time ultrasound systems.     

大功率消磁线圈受力分析与计算

大功率消磁线圈在运行中会受到较强电磁力的作用，客观地分析和计算电磁力的大小及分布情况，是设计和建造大型消磁站的一项基础性的工作。文中从电磁场基本原理出发，应用张量理论分析、计算了大功率消磁线圈的受力情况，对于设计和建造大型消磁站具有参考作用。     

泄放阀着火时LNG储罐外容器热-结构耦合分析

针对LNG储罐在泄放阀着火的工况,对受到外界高温火焰辐射的LNG外容器的传热和结构进行了耦合分析研究.建立了16万方LNG大型储罐的实体有限元模型,根据规范和相关文献中的推荐方法,获得了泄放阀火焰高温辐射时罐顶外表面的等效辐射温度,根据正常工作时的稳态传热工况进行储罐外容器内表面等效对流传热系数的计算,得到了正常工作时...