进气温度对正庚烷HCCI燃烧特性影响研究

在一台燃烧边界条件可控的快速压缩机上对均质压燃燃烧方式(HCCI)下进气温度对燃烧特性的影响进行了研究.以正庚烷燃料为研究对象,在不同的进气温度条件下,通过对燃烧始点、燃烧持续期、燃烧放热率等参数的分析,得出了进气温度对HCCI燃烧特性的影响规律.试验结果表明:随着进气温度的升高,燃烧始点提前,燃烧持续期缩短,最高燃烧温度升高,放热率最大值增加.     

燃油温度对船用柴油机喷雾及燃烧特性影响的仿真研究

以某型船用柴油机为研究对象,通过对不同燃油温度下喷油嘴内部的流动仿真分析,对喷嘴内部的流动和空穴现象进行了研究,得到合理的喷孔出口处油滴的初始状态;通过喷雾和缸内燃烧的耦合计算,分析不同的燃油温度对柴油机燃烧及排放特性的影响规律。研究结果表明:燃油进机温度直接影响燃油喷雾、破碎、蒸发及燃烧过程,对NOx排放影响更为明显;燃油进机温度须作为柴油机燃烧系统开发试验时的试验基准之一。     

纳米铝粉在水蒸气中的燃烧特性

针对粒径对纳米铝粉燃烧性能的影响,研究了不同粒径的纳米铝粉在水蒸气气氛中的燃烧特性,同时与其在空气气氛中的燃烧特性进行比较.结果表明,纳米铝粉粒径对其在水蒸气气氛中的着火温度影响较大,但对其燃烧的最高温度影响较小.纳米铝粉在水蒸气气氛中的着火温度比在空气气氛中的着火温度低,且最高温度也低.从燃烧现象可以发现,纳米铝粉在空气气氛中比在水蒸气气氛中燃烧剧烈,火焰亮度更强.此外,还采用扫描电镜与能谱分析联用技术对纳米铝粉在不同气氛中的燃烧产物进行了分析.     

煤燃烧产生的细微粒子中重金属元素富集性的实验研究

本文详细地研究了燃烧温度，燃烧气氛及煤粉细度对几种有毒重金属的燃烧过程中的行为的影响，发现温度，气氛及煤粉细度对各重金属元素在燃烧中的行为有重要的影响，再从各元素的总量角度研究了燃烧工产史对重金属行为的影响，并比较了不同煤种燃烧时重金属行为的差异。     

液态排渣煤粉燃烧器燃烧温度影响因素分析

针对液态排渣煤粉燃烧器,基于方程求解法建立燃烧温度计算模型,采用控制变量的方法设计计算方案,研究分析了热风温度、过量空气系数、冷却水带走热量比例、热负荷、煤低位发热量各单因素对燃烧温度的影响规律。计算了20种不同影响因素情况下的煤粉燃烧器燃烧温度,在此基础上,利用灰色关联分析探讨了各因素对燃烧温度的影响程度。     

CA6DL1—30柴油机燃烧室改进的模拟与实验研究

为研究燃烧室形状对柴油机燃烧和排放性能的影响,应用大型通用CFD软件STAR—CD程序对3种不同形状的燃烧室内燃烧过程进行了多维数值模拟计算,研究了不同的燃烧室形状对缸内气流运动以及缸内燃烧温度和排放的影响,并通过实验验证了计算模型的正确性。     

均质压燃燃烧着火时刻的循环变动

在一台改装单缸机上,研究了进气温度、进气压力、外部废气再循环率等运行参数对汽油均质压燃(HCCI)燃烧着火时刻循环变动的影响.结果表明:着火时刻对应的曲轴转角对HCCI燃烧循环变动有重大影响.着火时刻提前,HCCI燃烧循环变动较小.不同运行参数对燃烧循环变动的影响不同.进气温度和冷却水温度升高、进气压力增大有助于减小着火时刻循环变动,过量空气系数和EGR率增大会增大着火时刻循环变动.     

分级风比率对降低NOx及锅炉燃烧的影响

分级燃烧是行之有效的降低NOx燃烧技术.文中用fluent软件对分级燃烧的不同分级风工况进行数值模拟研究,分析不同分级风比率对降低NOx效果、炉膛出口温度、飞灰含炭量的影响.     

一种高强度富氧天然气燃烧器火焰特性的数值模拟

根据天然气冲天炉结构特点设计了一种富氧高燃烧强度的燃烧器并建立燃烧器燃烧的物理模型和数学模型,利用CFD软件Fluent模拟研究了不同预热温度以及不同空气预混比例对燃烧温度、火焰长度变化等的影响规律,为以后该类型燃烧器的设计提供了理论依据。     

磁场对油池旋转火焰温度影响的研究

通过磁场对油池旋转火焰燃烧特性影响的理论分析和实验研究，得到不同磁场强度对旋转火焰燃烧温度的影响程度，从而了解实际燃烧过程中旋转火焰在有磁场作用下的燃烧特性。通过理论分析和实验研究可知：在一定的磁场强度下，旋转火焰的温度随磁场强度的增加而增加，但是其增加的幅度是有限的。这对研究实际火灾中火旋风的燃烧特性具有重要意义。     

甲烷/高温烟气稀释空气的Mild燃烧过程的数值研究

中低氧浓度稀释MILD燃烧与传统有焰燃烧方式相比,燃烧室内温度相对均匀,可以有效控制和降低NO_X等污染物排放。燃烧室内的烟气循环导致的混合气稀释程度、预热温度以及流场应变率对Mild燃烧过程有重要影响。通过对不同稀释和预热程度的一维层流对撞扩散火焰进行计算,研究了烟气回流稀释/预热形成的Mild燃烧情况。数值计算结果表明,Mild燃烧能很好的控制燃烧场的最高温度和反应放热速率,得到较为均匀的温度场,并因此降低产物中污染物的浓度。对不同预热温度、不同拉伸率下工况的计算证明了Mild燃烧能够扩展燃料的燃烧极限,Mild燃烧对流场等外部干扰的敏感度较小,燃烧稳定。     

Electrical conductivity of seeded combustion products of water gas-air system

The dependence of the electrical conductivity of seeded combustion products of water gas-air system on preheating and oxygen enrichment of air has been analytically investigated. Optimum oxygen enrichment is estimated to be around 40% while preheating could be carried for temperatures in the range of 1100 to 1400 K. The conductivity of the system is found to increase with the addition of extra CO to the fuel.     

Laminar flow with combustion in inert porous media

This work presents one-dimensional numerical results for combustion of an air/methane mixture in inert porous media using laminar and radiation models. Comparisons with experimental data are reported. The burner is composed by a preheating section followed by a combustion region. Macroscopic equations for mass, momentum and energy are obtained based on the volume average concept. Distinct energy equations are considered for the porous burner and the flowing gas. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to relax the entire equation set. Inlet velocity, excess air, porosity and solid-to-fluid thermal conductivity ratio were varied in order to investigate their effect on temperature profiles. Results indicate that higher inlet velocities result in higher gas temperatures, following a similar trend observed in the experimental data used for comparisons. Burning of mixtures close to the stoichiometric conditions also increased temperatures, as expected. Increasing the thermal conductivity of the preheating section reduced peak temperature in the combustion region. The use of porous material with very high thermal conductivity on the combustion region did not affect significantly temperature levels in the combustion section.     

Effects of preheating and operation conditions on combustion in a porous medium

The effects of preheating conditions (including the critical energy content, the firing rate, and the equivalence ratio) on the initiation and extinction of a super-adiabatic combustion (SAC) in a steady flow of propane/air mixture through a stack of stainless steel screens (an inert porous medium) are investigated. It is found that there are critical conditions for the initiation and extinction of a SAC in the steady flow through the inert porous column. The critical preheating energy required to initiate a SAC is found to decrease with the increase of the preheating equivalence ratio, the preheating firing rate, and the operational equivalence ratio. After the initiation of a SAC, two combustion modes (i.e., stable combustion mode and push-forward combustion mode) have been observed. These combustion modes are determined by the operational conditions.     

Effect of preheating waste cooking oil on biodiesel production and properties

Waste cooking oil from the university cafeteria was used as feedstock to produce biodiesel. The feedstock was then converted to biodiesel using two different methods. The two methods tested were with and without preheating to study the effect of preheating on biodiesel. For each one of the two methods two types of catalysts were used that is alkali and acidic. The effect on biodiesel yield, calorific value, viscosity, and density was observed. It was found that with preheating to higher temperatures, the yield was 87% with alkali catalyst and 70% with acid catalyst. On the other hand, without preheating, it was found that the yield using alkali catalyst was 98% and 75% using acidic catalyst. Further, the highest calorific value was obtained using alkali catalyst without preheating.     

Thermal management and catalytic combustion stability characteristics of premixed methane/air in heat recirculation meso‐combustors

In order to illuminate heat recirculation effect on catalytic combustion stability and further improve energy conversion efficiency in meso‐combustor, the catalytic combustion characteristics of the combustor with/without preheating channels are numerically studied at steady conditions. It is found that methane conversion rate and combustion efficiency increases by 2% to 3% and approximately 9% in the heat recirculation meso‐combustor, indicating that heat recirculation effect facilitates more complete combustion of methane and medium components. Preheating channels show positive effects on improving combustion stability in the heat recirculation meso‐combustor. On one hand, preheating channels facilitate heat recirculation effect, and heat recirculation rate exceeds 10% for all cases and reaches 31.8% with an inlet velocity of 0.5 m/s, leading to significant increment of methane‐specific enthalpy at the preheating channel outlet. On the other hand, Rh(s)/O(s) ratios of catalytic surface and catalytic surface temperature in main reaction zone are enlarged by the preheating channels, facilitating methane adsorption at catalytic surface. Specially, most of fuels are consumed in a shorter distance with higher methane conversion speed, which brings benefits to promote combustion efficiency and may be helpful to inhibit the combustion instability in heat recirculation meso‐combustors.     

多孔介质中预混式燃烧的数值研究

本文考虑向燃烧室中插入高孔隙率的多孔介质的燃烧过程,根据气固两相局部非热平衡假设,建立了混合气体在惰性多孔介质中预混燃烧的一维数学模型,模拟了不同条件下甲烷-空气的预混合气在多孔介质中燃烧时的温度分布及气体流速、当量比和吸收系数对燃烧室气体温度峰值的影响.结果表明,多孔介质的存在明显改善了燃烧室的换热性能,强化了对新鲜混合气的预热,加速了燃烧反应的进行,燃烧室利用率提高.     

3D numerical modelling of turbulent biogas combustion in a newly generated 10 KW burner

This study concentrates on the 3D numerical modelling of combustion of different biogases in a generated burner and combustor. The main goal of this study is to investigate the combustion characteristics (such as temperature and emissions) of biogases through a combustor due to depletion of natural gas. Moreover, the effect of the preheated air on flame temperatures of biogases have been studied in the present study. Finally, the effect of H₂S amount in biogas on SO₂ emissions has been investigated within these predictions. The numerical modelling of turbulent diffusion flames has been performed by using the standard k–ε model of turbulent flow, the PDF/Mixture Fraction combustion model and P-1 radiation model in the combustor. A CFD code has been used for all predictions. Temperature gradients have been determined on axial and radial directions for better understanding combustion characteristics of biogases. Modelling has been studied for thermal power of 10 kW and excess air ratio of λ = 1.2 for each biogas combustion. The first finding is that combustion of biogases is possible via the newly generated burner. Moreover, the results show that the one of biogas is very close to methane in terms of temperature distributions in the combustor due to including high amount of methane compared to other biogases. It is also concluded that the flame temperatures of biogases increase with preheating the combustion air as expected. It is finally revealed that SO₂ emissions increase as amount of H₂S in biogas is increased through the combustor.     

Experimental investigation of NOx emissions during pulverized char combustion in oxygen-enriched air preheated with a circulating fluidized bed

An experimental investigation on NO_x emissions of pulverized char combustion in oxygen-enriched air was carried out in a new test system consisting of a circulating fluidized bed (CFB) and a down-fired combustor (DFC). In this paper, the pulverized char combustion characteristics and NO_x emission characteristics in the air conditions, the local oxygen-enriched air conditions in the CFB and the overall oxygen-enriched air conditions were studied. The results show that when the primary air oxygen concentration increased from 21.0% to 24.6% and to 28.2%, the ratio of fuel-nitrogen converted to nitrogen in the CFB increased from 39.7% to 45.0% and to 50.8%, respectively. This finding indicates that the preheating process in the CFB was one of the important reasons why the preheating combustion technology could significantly reduce NO_x emissions. Compared with the air combustion conditions, the NO emissions decreased to almost half of the original emissions when only the primary air oxygen concentration increased. On this basis, the NO emissions increased slightly when the air oxygen concentration was also increased in the DFC. Under these conditions, the variations in the char combustion efficiency were consistent with the variations in the temperature distribution. The feasibility and superiority of integrating the preheating combustion technology and oxygen-enriched air combustion technology are verified.     

预热室结构对多段式自预热燃烧器内燃烧及NOx排放特性的影响

提出了一种多段式自预热燃烧器及其4种典型的预热室结构,通过计算流体力学（CFD）方法研究了燃烧室内流场、烟气卷吸率、温度场、燃气燃尽率以及NOx体积分数,并与传统燃烧器的情况进行了对比．结果表明：与传统燃烧器相比,多段式自预热燃烧器改变了燃烧室内流场,对低热值燃料适应性强,其预热室结构同时影响烟气卷吸率和预热效果,并最终影响燃尽率与NOx体积分数;此外,燃烧器负荷对燃尽率影响甚微,但对NOx体积分数影响较大．