内混式二相流喷嘴流量特性

结合相关理论,以水、润滑油和十二烷基硫酸钠(SDS)溶液作为液体介质,详细研究了操作参数(气液比)和液体物性(粘度、表面张力)对一种典型的内混式二相流喷嘴流量特性的影响,通过对实验数据的分析得出了一些重要结论。随着液体介质粘度的增加,气液压力要随之增加,而表面张力的增加,气液压力基本上保持不变。根据大量的实验数据,回归出了内混式雾化喷嘴的液体流量系数的经验关联式。     

水煤浆气力式静电雾化喷嘴设计及雾化流场形貌

借鉴已有的常规水煤浆气力式雾化喷嘴的研究与应用成果,设计了新型的气力式静电雾化喷嘴。在此基础上搭建了以环电极感应充电方式的水煤浆静电雾化实验台,利用激光粒子成像速度仪(PIV)上的CCD相机对其静电雾化流场的形貌进行实验观察,获取其荷电射流雾化角度随外加电场增加的变化情况;并利用激光粒子动态分析仪(PDA)系统分别获得流场轴线上以及轴线150 mm处横截面的透浆率随环电极电压的变化情况。实验结果表明:在感应电场的作用下,荷电喷雾流场随外加电场的增加而扩展,射流雾化角在42°—65°变化,且随充电电压的上升略呈一定的指数规律增加;水煤浆雾滴在射流轴线附近聚集的现象得以改善,浆滴在雾炬空间的弥散愈加均匀,可在一定程度上解决水煤浆雾炬核心区贫氧燃烧的难题。     

双流体管道喷雾系统的计算和评述

分析了新型干法预分解窑广泛采用的增湿塔雾化系统所存在的水压大、喷嘴磨损大、水滴蒸发时间长等缺陷;介绍了双流体管道喷雾系统具有结构简单、水滴直径小,需蒸发时间短,占地空间小等优势;并进行了双流体管道喷雾系统的管道直径和水滴蒸发时间的设计计算;最后列举了双管道喷雾系统用于窑头烟气降温调质处理的实际应用效果。     

我国高速雾化机的进展及与国外雾化机性能的比较

叙述了我国高速旋转式雾化机的发展过程，介绍了我国生产的9种规格雾化机的特性，从设计制造及使用等方面与国外同类型产品作了比较，指出了我国产品与国外产品的不同点、差距及其改进方向。     

以蜂窝陶瓷为载体的燃烧催化剂研究

采用蜂窝状载体,在蜂窝陶瓷基质上涂以助剂,制备了Pt-Pd为活性组分催化剂,考察了催化剂对CO、HC的净化效果及蜂窝催化剂的耐热性能。结果表明,添加助剂对催化剂的活性有很大的影响,可使HC的催化燃烧活性得到显著的提高;相对于无助剂催化剂,其丙烯的最低全转化温度降低了70℃。表明蜂窝Pt-Pd,助剂/A l2O3是一个很有应用潜力的低温烃类燃烧贵金属催化剂。     

引射雾化喷嘴性能研究

对新型引射雾化喷嘴的流量系数、雾化角、雾粒分布均匀性进行了研究,提出了喷嘴流量系数、雾化角、雾粒大小计算方法。研究表明,这些方法的计算结果与实际很接近,对新型引射雾化喷嘴的设计计算十分有益,具有重要的工程意义。     

螺旋雾化器加装引射式喷射器的实验对比研究

对螺旋雾化器加装引射式喷射器前后的雾化效果进行了对比实验研究,并利用高速摄影仪拍得了加装前后雾化效果的照片。从实验现象中可以看出,加装引射式喷射器后螺旋雾化器雾化效果有了显著的提高。对比所拍摄的照片并给出了初步的理论分析,从理论上解释了气水两相流中气泡内能在水流的雾化中起到的重要作用。     

Effervescent atomization under sub-sonic and choked conditions—a theoretical approach

Spray formation of a bi-component mixture under sub- and choked-flow conditions has been studied. Special attention has been drawn to the processes inside the atomizer, i.e., the expansion chamber and two orifices. The relevant processes, which include the pressure drop at the inlet orifice, nuclei formation, bubble growth inside the expansion chamber, pressure drop at the discharge orifice, the velocity slip between the bubbles and the liquid bulk, and the flow regime (sub- and choked-flow) at the discharge orifice, have been analyzed by using a one-dimensional model approach.Three different operating regions have been identified. In the 1st, when the inlet to discharge orifices' diameter ratio is small, subsonic flow is anticipated, and no noticeable slip between the bubbles and the bulk liquid is expected. As the orifices' diameter ratio increases, the slip becomes more and more significant (2nd region). When the pressure at the expansion chamber exceeds the critical pressure, the flow chokes, and the slip maximizes. Further increase results in maximum slip (3rd region).The two main roles of the expansion chamber were described: (a) to provide the required time for the bubbles to grow till one bubble touches the other, and (b) to provide the discharge orifice with a well-mixed mixture to allow dominant flashing enhanced by shear stress disintegration. Optimized operation conditions for best atomization, optimized expansion chamber volume, and optimized orifices' diameter ratio are proposed in terms of the thermodynamic properties of the mixture.     

Experimental investigation and model improvement on the atomization performance of single-hole Y-jet nozzle with high liquid flow rate

Y-jet nozzle, as an efficient multi-hole internal-mixing twin-fluid atomizer, has been widely used for liquid fuel spray in many industrial processes. However, single-hole Y-jet nozzle with high liquid flow rate is indispensable in some confined situations due to a small spray cone angle. In this paper, the atomization performance of single-hole Y-jet nozzles with high liquid mass flow rates ranging from 400 to 1500 kg/h for practical semidry flue gas desulfurization processes was investigated by the laser particle size analyzer, and the effects of spray water pressure, atomizing air pressure and air to liquid mass flow ratio on the liquid mass flow rate and the droplet size distribution were analyzed. Moreover, the secondary atomization model was modified on the basis of previous random atomization model of Y-jet nozzle. The predicted results agreed well with the experimental ones, and the improved atomization model of Y-jet nozzle was well validated to design the nozzle geometry and to predict the droplet size distributions for single-hole Y-jet nozzle with high liquid mass flow rate.     

一种双金属盐催化剂的制备及其对螺压推进剂燃烧性能的影响

某型号发射装置要求推进剂装药燃速29.0～30.0mm/s(20 ℃,10 MPa)、压强指数≤0.4(20 ℃,4～16 MPa)、装药燃速在贮存期内变化不超过1％(20 ℃,10 MPa).为使装药同时满足燃烧性能指标及燃速变化率的要求,合成了一种双金属盐催化剂,通过合成工艺研究、性能表征及结合装药应用研究,表明加...     

氯化液喷雾脱挥工艺研究

以过氯乙烯氯化液为原料,研究了氯化液喷雾脱挥工艺,取得了良好的效果。试验条件下,氯化液中的氯苯脱除率达到98.7%以上,热水中氯苯质量浓度小于25 mg/L,是现有工艺的6%~15%;喷雾脱挥形成的树脂颗粒的Sauter平均粒径(SMD)为70~150μm,粒径的累积体积分布符合Rosin-Rammler分布。对得到的过氯乙烯树脂进行质量检测,结果表明,树脂质量都达到了产品要求的质量标准。     

Diagnostics of acoustic properties of the combustion zone by means of periodic changes in the nozzle throat area

A mathematical model is proposed, which allows calculating the amplitude of forced pressure oscillations in the combustor of a liquid-propellant rocket engine, caused by periodic changes in the nozzle throat area, with allowance for acoustic properties of the combustion zone. Results calculated for some particular cases are given. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 12–17, November–December, 2008.     

Influence of atomizer exit area ratio on the breakup morphology of coaxial air and round water jets

The goal of this article is to study the effect of atomizer exit area ratio on atomizer performance. The experiments are performed on the round liquid jet breakup of seven coaxial air‐blast atomizers with water–air systems. The breakup morphology of liquid jet is observed first. The membrane‐type breakup can be divided into two subregimes called bag‐type breakup and membrane‐fiber breakup, and a correlation of characteristic length on bag‐type breakup regime is obtained. Then, we analyze the influence of atomizer exit area ratio on the breakup morphology of water‐air jets. To obtain reasonable atomization morphology criterions, the atomizer exit area ratio is used to modify the Weber number and momentum flux ratio per unit volume. This method is found to be able to explain different experimental results in the literature, which is also close to the results of round liquid jet in cross air flow and secondary atomization. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2335–2345, 2014     

A parametric study on natural gas fueled HCCI combustion engine using a multi-zone combustion model

Homogenous Charge Combustion Ignition (HCCI) is a good method for higher efficiency and to reduce NOx and particulate matter simultaneously in comparison to conventional internal combustion engines. In HCCI engines, there is no direct control method for auto ignition time. A common way to indirectly control the ignition timing in HCCI combustion engines is varying engine’s parameters which can affect the combustion. In this work, a parametric study on natural gas HCCI combustion is conducted in order to identify the effect of inlet temperature and pressure, compression ratio, equivalence ratio and engine speed on combustion and engine performance parameters. In this paper, two kinds of parameters will be discussed. First, in-cylinder pressure diagrams and variation of start of combustion which are combustion parameters will be presented and then the second category, indicated mean effective pressure and thermal efficiency which are performance parameters will be studied. A six zone model coupled with detailed chemical kinetics code is used to simulate HCCI combustion. Both heat and mass transfer was considered in the modeling procedure. Results revealed that among the considered parameters, the equivalence ratio and inlet pressure are the most valuable parameters which can improve the combustion and performance characteristics of the HCCI engine.     

聚合物的水声吸收数学模型与实验研究

以声波在高分子介质中的传播理论为依据，应用阻抗匹配法，推导出了材料的水下吸声的数学模型，为对该模型进行实验验证，设计合成了一系列声速和声衰减系数不同的聚合物。测试了它们的水下吸声系数、声速和声衰减系数，并用理论计算结果与测试结果对比．发现理论计算得到的水声材料的吸声系数与实测值非常接近，表明该数学模型可以较准确地预测材料的水声吸声性能，指导水声吸声材料的设计。     

Devolatilization and combustion of large coal particles in a fluidized bed

Devolatilization and combustion of large particles of Eastern Canadian coals (Evans and Minto), 5-50 mm dia., were studied in a bench-scale atmospheric fluidized bed reactor at 1023-1173 K with 0.5 mm sand particles as the bed material. The devolatilization time, mass loss history, changes in proximate volatiles content and C/H mass ratio, and temperature history at the centre of the particle during devolatilization were determined. The mass loss during devolatilization is correlated with the proximate volatiles content of the parent coal. The devolatilization time is correlated with the initial particle diameter by a power-law relation with an exponent of 1.54-1.64. The results show insignificant effect of superficial velocity on devolatilization.     

富氧燃烧中气体辐射模型对燃烧与换热数值模拟的影响

富氧燃烧过程中,由于使用再循环烟气代替空气中N₂作为稀释剂,烟气中存在大量CO₂和H₂O。CO₂和H₂O作为非极性三原子分子,具有N₂没有的辐射能力,导致富氧燃烧中气体辐射特性发生变化。在数值模拟过程中,气体辐射模型是一个重要的子模型。前人提出多种修改后适用于富氧燃烧的气体辐射模型,但不同气体辐射模型在不同富氧燃烧工况数值模拟中的影响尚未有统一研究。为了研究不同炉型下,气体燃烧和煤粉燃烧中气体辐射模型对燃烧换热模拟结果的影响,通过编程,将一种考虑CO影响的气体辐射模型以及文献中的6种典型气体辐射模型耦合入数值模拟计算。结果表明,在气体富氧燃烧中,气体辐射模型影响了火焰结构。同时,燃烧温度分布有所变化,不同模型结果之间差别最高可到500 K。气体与壁面之间的辐射换热受到影响。气体辐射模型对炉膛中心火焰区域影响较大,而对非火焰区域影响较小。在煤粉富氧燃烧过程中,当有效辐射层厚度在0.3 m左右时,如在100 kW下行炉中,气体辐射模型对煤粉燃烧数值模拟结果几乎没有影响。这可能是由于颗粒辐射在辐射换热计算中占主导地位。而当有效辐射层厚度在16 m左右时,如1000 MW塔式炉中,气体辐射模型对炉内切圆燃烧火焰温度以及组分浓度影响较大,温度差别可到100 K左右。而气体辐射模型对炉膛中心模拟结果没有影响。     

Effects of operational parameters on emission performance and combustion efficiency in small-scale CFBCs

A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emissions. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (two-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO_x and SO₂ emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure at the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO₂ and NO_x emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO_x emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal.     

超声波雾化碳分法制备纳米氢氧化铝

以铝酸钠溶液和二氧化碳气体为原料,在特制的反应装置中,通过超声波使铝酸钠溶液雾化后与二氧化碳气体反应,并在丁醇中进行表面改性,制备了纳米Al(OH)3粉体。考察了NaAlO2浓度、CO2与载气流量比、表面改性等因素对Al(OH)3粒径的影响。利用XRD、TEM和红外光谱分析等测试方法对制备的Al(OH)3进行了分析表征。实验结果表明,通过条件优化后所制备的Al(OH)3粒子呈单斜晶系,具有疏水性,粒度分布均匀,平均粒径50 nm。     

Stability and performance of catalytic microreactors: Simulations of propane catalytic combustion on Pt

A pseudo-two-dimensional (2D) model is developed to analyze the operation of platinum-catalyzed microburners for lean propane-air combustion. Comparison with computational fluid dynamics (CFD) simulations reveals that the transverse heat and mass transfer is reasonably captured using constant values of Nusselt and Sherwood numbers in the pseudo-2D model. The model also reasonably captures the axial variations in temperatures observed experimentally in a microburner with a gap size. It is found that the transverse heat and mass transport strongly depend on the inlet flow rate and the thermal conductivity of the burner solid structure. The microburner is surface reaction limited at very low velocities and mass transfer limited at high velocities. At intermediate range of velocities (preferred range of reactor operation), mass transfer affects the microburner performance strongly at low wall conductivities, whereas transverse heat transfer affects stability under most conditions and has a greater influence at high wall conductivities. At sufficiently low flow rates, complete fuel conversion occurs and reactor size has a slight effect on operation (conversion and temperature). For fast flows, propane conversion strongly depends on residence time; for a reactor with gap size of , a residence time higher than 6 ms is required to prevent propane breakthrough. The effect of reactor size on stability depends on whether the residence time or flow rate is kept constant as the size varies. Comparisons to homogeneous burners are also presented.