高温低氧燃烧火焰辐射特性的实验研究

对高温低氧燃烧火焰的辐射特性进行了实验测试，同时利用CFD通用软件对火焰热辐射行性进行了数值计算，得到了在不同预热空气温度、不同预热空气含氧量条件下，火焰形状及火焰热辐射特性的变化规律。结果表明：高温低氧燃烧火焰的体积与长度随着预热空气中含氧量的降低而扩大，而预热空气温度对燃烧火焰体积的影响不大。高温低氧燃烧火焰对炉膛壁面的热辐射能力随着预热空气温度的降低而下降，同时也随着预热空气含氧量的降低而下降。图4参9     

空气预热温度对生物柴油火焰特性影响研究

利用高速摄影法及数字图像处理技术得到生物柴油燃烧火焰图像,并通过Matlab软件求取火焰长度和面积,研究了空气预热温度对火焰形态、长度、面积的影响。实验中共设定了9个空气温度：20℃、80℃、140℃、220℃、290℃、350℃、400℃、450℃和500℃。结果表明：空气预热温度较低时,生物柴油火焰结构分散、主要燃烧区（火焰亮度较高区域）面积较小且连续性差;空气预热温度升高后,火焰结构更紧凑、主要燃烧区面积增大、亮度明显增加、连续性变好。各个工况下火焰长度和面积不是一个定值,而是在一定范围内剧烈地震荡,随着空气预热温度的升高,火焰平均长度和平均面积有相近的变化趋势：先明显减小,再逐渐上升。     

生物质气化低热值燃气窑炉燃烧温度特性

通过生物质气化低热值燃气在工业窑炉上燃烧的中试试验研究,得到不同燃烧条件下生物质燃气的窑炉燃烧温度特性。试验结果表明:常温空气助燃情况下,经低温净化的冷燃气的窑炉燃烧温度约1100℃,经高温净化的热燃气的窑炉燃烧温度约1200℃;如果回收燃烧烟气的余热,将助燃空气预热至400℃时,燃气窑炉燃烧温度可提高100~150℃。生物质气化低热值燃气基本能达到工业窑炉生产对温度的要求。     

固定床玉米秸燃烧特性的实验研究

影响生物质燃烧特性的因素主要包括燃料长度、空气预热温度、送风量和燃料含水量。研究了上述因素对玉米秸的燃烧特性，包括指燃料失重率、炉内温度以及炉内的气体成分的影响，并对影响的机理进行了相应的分析。     

棉秆热解及燃烧特性试验研究

利用热重分析仪研究棉秆在N2及空气气氛下的热解及燃烧特性,通过动力学分析得到了棉秆热解及燃烧的动力学参数,相关系数在0.99以上.研究结果表明:随着升温速率提高,棉秆热解过程中的活化能增加.试验棉秆的着火温度为246℃.     

稻壳燃烧特性与动力学模型的研究

采用热重分析仪,在空气气氛下对稻壳的燃烧热失重状况进行了研究,并分析了四种升温速率（5,10,20,50℃／min）对燃烧特性指数的影响。利用Coats-Redfern模型,Freeman—Caroll模型和Flynn—Wall-Ozawa模型分别计算了稻壳燃烧的活化能及频率因子。实验表明：随着升温速率的升高,燃烧性能得到良好改善,但反应起始温度和终止温度由于受热滞后性影响,向高温区偏移使着火温度升高。模型计算结果表明：稻壳燃烧的表观活化能较低,升温速率对活化能的影响并不明显,Coats—Redfern模型、Freeman-Caroll模型可用于估算,Flynn—Wall—Ozawa模型可作为重要数据参考。     

预热空气与高炉煤气的扩散燃烧混合特性研究

针对某钢铁企业高炉煤气回收水冷系统的特点,分析研究了低热值高炉煤气与不同预热温度空气的同轴扩散气流在绝热炉膛内混合和燃烧的特点,据此建立k-ε双方程燃烧数学模型,并对其燃烧混合特性进行模拟研究.研究结果表明:回流中心区的位置位于轴向0.1～0.22 m,但随着空气预热温度的升高,缩小到0.12～0.2 m,回流负压也有...     

污泥与秸秆掺烧的燃烧特性研究及应用

利用热重分析法对某城市污泥和秸秆及其混合样的燃烧特性进行了分析研究,结果表明,在加热速率20℃/min,温度为20¹ 000℃,空气气氛下,污泥和秸秆及其混合样燃烧的失重特性和燃烧性能存在差异。单一污泥试样的着火温度为334.2℃,试样着火后,燃烧速率并不高,不能快速形成较高的燃烧温度,且燃烧过程不均匀。污泥中掺入秸秆后,秸秆中的挥发分在低温区大量析出和燃烧,增加了反应的剧烈程度,提高了混合样的燃烧稳定性和燃尽水平。随着秸秆掺混比例的增加,混合试样的着火点温度明显降低、最大燃烧速率出现的温度提前、可燃性指数逐渐增加。当秸秆的掺混比为20%,混合样品的低位发热量达到13 911 kJ/kg。     

煤绝热燃烧过程损的计算与分析

本文对无烟煤、烟煤、褐煤与泥煤绝热燃烧过程的(火用)损进行了计算与分析,结果表明:提高空气预热温度,降低空气消耗系数,采用富氧燃烧可以降低燃烧过程(火用)损失,而以提高助燃空气的预热温度效果最为显著。因此,在煤的燃烧过程中,应尽可能地把助燃空气预热到较高温度;在空气不预热时,应尽可能在低空气消耗系数下完全燃烧。     

稻秆燃烧动力学特性研究

通过热重分析方法研究了稻秆的燃烧过程及其动力学特性.非等温热重法的升温速率分别为20 ℃/min、30 ℃/min、40 ℃/min,加热终温800 ℃;采用空气为载气.得到稻秆燃烧的TG、DTG曲线,研究了加热速率、温度对燃烧过程的影响,建立了稻秆燃烧的反应动力学方程,由Freeman-Carroll法得到该类稻秆燃烧动力学参数,并提出了相应的燃烧机理.为燃烧稻秆锅炉的设计开发提供了理论支持.     

Assessment of wind characteristics and wind turbine characteristics in Taiwan

Wind characteristics and wind turbine characteristics in Taiwan have been thoughtfully analyzed based on a long-term measured data source (1961–1999) of hourly mean wind speed at 25 meteorological stations across Taiwan. A two-stage procedure for estimating wind resource is proposed. The yearly wind speed distribution and wind power density for the entire Taiwan is firstly evaluated to provide annually spatial mean information of wind energy potential. A mathematical formulation using a two-parameter Weibull wind speed distribution is further established to estimate the wind energy generated by an ideal turbine and the monthly actual wind energy generated by a wind turbine operated at cubic relation of power between cut-in and rated wind speed and constant power between rated and cut-out wind speed. Three types of wind turbine characteristics (the availability factor, the capacity factor and the wind turbine efficiency) are emphasized. The monthly wind characteristics and monthly wind turbine characteristics for four meteorological stations with high winds are investigated and compared with each other as well. The results show the general availability of wind energy potential across Taiwan.     

Combustion characteristics of hydrogen

Acquisition of reliable combustion data for hydrogen-air mixtures is an important prerequisite to the emergence of hydrogen as a source of fuel gas. In an attempt to alleviate the confusion associated with conflicting burning velocity values, an improved measurement technique based on laser-Doppler anemometry has been developed. The method combines accuracy with speed of operation and has been applied to hydrogen-air flames.     

An assessment on seasonal analysis of wind energy characteristics and wind turbine characteristics

This paper presents seasonal variations of the wind characteristics and wind turbine characteristics in the regions around Elazig, namely Maden, Agin and Keban. Mean wind speed data in measured hourly time series format is statistically analyzed for the six year period 1998–2003. The probability density distributions are derived from the time series data and their distributional parameters are identified. Two probability density functions are fitted to the measured probability distributions on a seasonal basis. The wind energy characteristics of all the regions is studied based on the Weibull and Rayleigh distributions. Energy calculations and capacity factors for the wind turbine characteristics were determined for wind machines of different sizes between 300 and 2300 kW. It was found that Maden is the best region, among the regions analyzed, for wind characteristics and wind turbine characteristics.     

Pool boiling characteristics of nano-fluids

Common fluids with particles of the order of nanometers in size are termed as ‘nano-fluids’ which have created considerable interest in recent times for their improved heat transfer capabilities. With very small volume fraction of such particles the thermal conductivity and convective heat transfer capability of these suspensions are significantly enhanced without the problems encountered in common slurries such as clogging, erosion, sedimentation and increase in pressure drop. This naturally brings out the question whether such fluids can be used for two phase applications or in other words phase change in such suspensions will be assistant or detrimental to the process of heat transfer. The present paper investigates into this question through experimental study of pool boiling in water-Al₂O₃ nano-fluids. The results indicate that the nano-particles have pronounced and significant influence on the boiling process deteriorating the boiling characteristics of the fluid. It has been observed that with increasing particle concentration, the degradation in boiling performance takes place which increases the heating surface temperature. This indicates that the role of transient conduction in pool boiling is overshadowed by some other effect. Since the particles under consideration are one to two orders of magnitude smaller than the surface roughness it was concluded that the change of surface characteristics during boiling due to trapped particles on the surface is the cause for the shift of the boiling characteristics in the negative direction. The results serve as a guidance for the design of cooling systems with nano-fluids where an overheating may occur if saturation temperature is attained. It also indicates the possibility of such engineered fluids to be used in material processing or heat treatment applications where a higher pre-assigned surface temperature is required to be maintained without changing the fluid temperature.     

Radiation characteristics of solar hothouse

The optimal geometric parameters and radiation regime of a solar hothouse are determined under the conditions of the city of Karshi using the data of the solstice in December–January.     

Ignition characteristics of gasless reactions

Initiation energy requirements for condensed phase systems were determined experimentally and analytically and found to obey a diffusion-limited reaction model. A model is described for the evaluation of the threshold input energy either by computer calculations or by approximate formulas. The use of dimensionless variables greatly reduces the necessary number of computer runs and simplifies the derivation of explicit expressions. The results are useful both for parametric study and theoretical prediction. It was found that initiation is promoted by low thermal conductance, low heat capacity, small particle sizes, and high heat of reaction. This method of analysis can also assess the effects of varying the energy deposition time. The predicted data are in reasonable agreement with experimental results which were obtained using pulsed and continuous wave lasers. The theoretical model is expected to be useful in the study of reaction phenomena associated with thermite and intermetallic pyrotechnics as well as in the study of certain metallurgical processes.     

Combustion characteristics of boron nanoparticles

An experimental investigation of the combustion characteristics of boron nanoparticles in the post flame region of a flat flame burner has been conducted. Boron is attractive as a fuel or a fuel supplement in propellants and explosives due to its high heats of combustion on both a gravimetric and volumetric basis. A relatively large database exists for combustion characteristics of large (greater than 1 μm) boron particles, but very little exists for nano-sized boron. Ignition and combustion characteristics have been studied in the post flame region of a fuel lean CH₄/Air/O₂ flame, with burner temperatures ranging from about 1600 K to 1900 K, and oxygen mole fractions ranging between 0.1 and 0.3. As in earlier investigations on boron combustion, a two-stage combustion phenomenon was observed. Ensemble-averaged burning times of boron nanoparticles were obtained, while the ignition time measurements for boron nanoparticles were extended into a lower temperature range previously unavailable in the literature. The measured burning times were between 1.5 ms and 3.0 ms depending on both the temperature and oxygen mole fraction. The ignition times were relatively insensitive to oxygen concentration in the range studied, and were affected only by temperature. The measured ignition times were inversely related to the temperature, ranging from 1.5 ms at 1810 K to 6.0 ms at 1580 K. The burning time results were compared to both diffusion and kinetic limited theories of particle combustion. It was found that the size dependence on particle burning times did not follow either theory.     

Exergy characteristics of woody biomass

The exergy characteristics of 60 woody biomass are investigated in this study. These include the moisture-related exergy, S-related exergy, ash-related exergy, and LHV (lower heating value)-related exergy. The results obtained from this study show that the moisture-related exergy, S-related exergy, ash-related exergy, and LHV-related exergy are in the ranges of 0–1,757.52, 0–30.28, 1.46–314.93, and 6,204.83–25,759.04 kJ/kg, respectively. The exergy values of woody biomass are in the range of 7,966.35–25,901.79 kJ/kg, and they are most contributed by LHV (77.89–99.97%), followed by moisture content (0–22.06%), ash content (0.01–1.94%), and S content (0–0.18%).     

Investigation of boiling hydrogen flow characteristics under low-pressure conditions - Flow regime transition characteristics

Understanding the thermal-fluid characteristics of boiling hydrogen is of great significance for applications of liquid hydrogen, such as alternative clean energy and space vehicles. The boiling temperature of liquid hydrogen under atmospheric pressure is 20.3 K; thus, it is easy to boil to form a gas–liquid two-phase flow. Fuel transfer under the boiling state has been avoided in the space industry because of its unstable flow characteristics; precise control of the fuel, including the boiling flow, is necessary to improve the space-vehicle performance. This study aims to understand the flow-regime transition characteristics of boiling hydrogen through experimental investigation. The experimental conditions were as follows: the flow direction was horizontal, the inner diameter of the heating pipe was 15 mm, the mass flux ranged from 50 to 110 kg/m²s, and the pressure ranged from 250 to 300 kPa A. The flow-regime transition characteristics were obtained by a high-speed camera. Fully liquid phase (LP), dispersed bubbly flow (DB), intermittent flow (IN), and annular flow (AN) were observed during the experiment. Each flow-regime boundary model is constructed using two dominant forces from the experimental result based on a Taitel–Dukler model. For the DB/IN boundary, a large-bubble sustainable condition is derived by the balance between the shear and buoyancy forces acting upon the bubble; for the IN/AN boundary, a droplet-sustainable condition is derived in terms of the force balance between the drag and gravity acting on the droplet. The semi-theoretical model predicts the experimental data with 96.7% accuracy.