多次喷油策略下喷油间隔对双对置发动机性能和排放的数值分析

为研究多次喷油策略下喷油间隔对对置活塞对置气缸二冲程(OPOC)柴油机性能的影响,针对预喷量不变耦合不同喷油间隔条件下OPOC二冲程柴油机燃烧过程进行数值仿真研究.研究喷油间隔对OPOC二冲程柴油机燃烧过程的影响以及OPOC二冲程柴油机性能的影响.结果表明:小喷油间隔可以促进OPOC缸内油气混合;随着喷油间隔的增加,OPOC二冲程柴油机缸内平均压力增大,平均温度升高,soot排放呈现先减小后增加的趋势,而NOx排放呈现先增大后减小的趋势.     

柴油机喷油系统的排放控制技术的探究

柴油机净化的关键是如何有效地消除NOx和微粒碳烟的生成量。文章从喷油系统出发，提出了改进排放的五种切实可行的方法，具有明显的现实意义。     

HALLO进气系统对柴油机燃烧的影响分析

利用燃烧分析方法，对TBD620V12柴油机的缸内压力曲线进行了放热规律分析．根据分析结果，研究了HALLO进气系统对燃烧过程的影响，确定了TBD620V12柴油机燃烧过程的特征参数．结果表明，采用HALLO进气系统，既保证了低负荷下形成良好的可燃混合气，使柴油机可在低负荷下良好地工作，又保证了高负荷下进气量，使高负荷下燃油充分燃烧。     

基于声波测温和LSSVM_GA的电厂NO_x排放建模与优化

因传统燃烧优化实验控制电厂NOx排放的方法很难满足复杂多变的燃烧工况,为更智能地对NOx排放进行监测和更方便地对其进行优化,对某电厂2#炉300 MW工况下NOx排放优化实验时的DCS内运行数据和声波测温系统内的温度分布数据进行采集。利用最小二乘支持向量机,以炉膛温度信息和其他影响NOx排放的主要因素为输入,以NOx排放浓度为输出建立NOx排放预测模型,在预测模型的基础上利用遗传算法对顶部4层分离燃尽风开度进行直接寻优,达到降低NOx排放的目的。结果表明:加入炉膛温度信息后的NOx排放模型准确度更高,遗传算法优化之后的NOx排放浓度显著降低,优化后参数更符合工程实际。     

480t/h锅炉空气分级燃烧优化数值模拟

为降低NOx排放,对某电厂480t/h锅炉空气分级燃烧改造数值模拟与优化,研究了分离燃尽风、切圆变化、煤粉细度变化对锅炉炉内温度场、NOx浓度分布和煤粉燃尽率的影响。模拟结果表明:空气分级改造后NOx排放浓度约为250mg/m3,较改造前降低约48%;切圆减小后,煤粉气流偏墙现象明显改善,水冷壁的结渣及高温腐蚀趋势降低;煤粉细度减小以后,煤粉燃尽率提高至97.56%,NOx排放浓度为248mg/m3,略有降低。     

柴油机掺烧生物柴油的燃烧模拟仿真

应用三维CFD软件AVLFIRE210,对CA6DF2D-21柴油机在同一工况下分别燃用B0、B10、B20和B50混合燃料的燃烧过程进行了模拟仿真,得出不同掺烧比下柴油机的扭矩、燃油消耗率、NOx排放量和Soot排放量,建立了评价柴油机综合燃烧性能的综合加权评分法,通过量化计算,得到标定工况下,使柴油机的动力性、经济性和排放性等综合性能达到最优的生物柴油掺烧比为B10。本文的研究为生物柴油在柴油机上的广泛应用提供了有力的理论依据。     

废气再循环率及可变压缩比对PCCI柴油机燃烧和排放的影响

预混压燃(PCCI)柴油机的预混压燃功能是通过调整进气门关闭时刻和提前喷油角度实现的,其能有效的控制可溶性有机物的排放,在PCCI柴油机中,加入废气再循环系统(EGR)能有效的控制一氧化氮的排放,降低压缩比能够显著推迟缸内着火时刻,强化油气混合,同时降低氮氧化合物和干碳烟的排放,但油耗会提高,本文阐述了废气再循环率及可变压缩比如何对PCCI柴油机燃烧和排放产生影响。     

公路隧道通风中CO和NOx浓度设计限值的分析

本文从影响人体健康的角度对隧道内排放的污染物CO和NOx进行了研究,利用CFK(Coburn-Forster-Kane)微分方程计算分析了人员停留时间对CO浓度设计限值取值的影响,并考虑了点效应对NOx浓度设计限值取值的影响,得到了各自的合理的浓度设计限值,其结果可供相关公路隧道在通风设计中参考使用.     

公路隧道通风中CO和NOx浓度设计限值的分析

本文从影响人体健康的角度对隧道内排放的污染物CO和NOx进行了研究,利用CFK(Coburn-Forster-Kane)微分方程计算分析了人员停留时间对CO浓度设计限值取值的影响,并考虑了点效应对NOx浓度设计限值取值的影响,得到了各自的合理的浓度设计限值,其结果可供相关公路隧道在通风设计中参考使用.     

直喷式和非直喷式柴油机的噪声、排放及其性能之间的比较

本文介绍了在同一种V-10型柴油机上对直接喷射式和非直接喷射式燃烧系统的噪声、排放以及燃油消耗率等性能进行研究的情况.文中阐述了两种燃烧系统的噪声与发动机转速、载荷和喷油定时的关系.同时也阐述了靠选用最佳喷油定时以降低噪声与排烟、废气污染和燃油消耗率的关系.     

Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines

In diesel engines, NOx formation is a highly temperature-dependent phenomenon and takes place when the temperature in the combustion chamber exceeds 2000 K. Therefore, in order to reduce NOx emissions in the exhaust, it is necessary to keep peak combustion temperatures under control. One simple way of reducing the NOx emission of a diesel engine is by late injection of fuel into the combustion chamber. This technique is effective but increases fuel consumption by 10–15%, which necessitates the use of more effective NOx reduction techniques like exhaust gas recirculation (EGR). Re-circulating part of the exhaust gas helps in reducing NOx, but appreciable paniculate emissions are observed at high loads, hence there is a trade-off between NOx and smoke emission. To get maximum benefit from this trade-off, a paniculate trap may be used to reduce the amount of unburnt particulates in EGR, which in turn reduce the paniculate emission also. An experimental investigation was conducted to observe the effect of exhaust gas re-circulation on the exhaust gas temperatures and exhaust opacity. The experimental setup for the proposed experiments was developed on a two-cylinder, direct injection, air-cooled, compression ignition engine. A matrix of experiments was conducted for observing the effect of different quantities of EGR on exhaust gas temperatures and opacity     

CFD modeling of hydrodynamics,combustion and NOx emission in a tangentially fired pulverized-coal boiler at low load operating conditions

With deep peak-load regulations, utility boilers are frequently operated under variable/low load conditions. However, their hydrodynamics, combustion and NOx emission characteristics are uncertain and relevant theoretical guidance are lacking. For this purpose, a comprehensive CFD model including flow, coal combustion and NOx formation is established for a 630 MW tangentially fired pulverized-coal boiler, aiming at solving the problem of decreasing combustion stability and increasing NOx emission in low-load operation. Based on the grid independence and model validation, the flow field, temperature profile, species concentration profile and NOx emission are predicted, and the influences of angle/arrangement of burners are further evaluated. Simulation results indicate that under low-load conditions, residual airflow rotation still persists at the top of boiler regardless of how to adjust the angle/arrangement of burners. With tilting the burner angle upward, flame is more concentrated, combustion becomes more stable, and heat flux rises in the upper zone; the burner arrangement of ABDE gives more uniform temperature distribution in the combustion zone. CO species shows higher content in the combustion zone; the 0° tilt angle gives maximum CO content, followed by the 15° angle, and finally the ?15° angle; compared to the ACDE and ABCE arrangement, the ABDE arrangement mode gives much lower CO contents. Burner tilt angle of ?15° benefits for lower NOx emission (183 mg/m³) but goes against stable combustion; the burner arrangement mode of ABDE is optimal for the present boiler, which ensures both stable combustion and lower NOx emission (209 mg/m³).     

高温燃气组份及NOx排放控制的基础研究

报道了关于燃煤磁流体－蒸汽联合循环发电中高温燃气组份计算、分析及ＮＯｘ排放控制的基础研究结果。     

Emission characteristics of coal combustion in different O2/N2, O2/CO2 and O2/RFG atmosphere

This study investigates the emission characteristics of CO(2), SO(2) and NOx in the flue gas of coal combustion by varying the compositions and concentrations of feed gas (O(2)/CO(2)/N(2)) and the ratios of recycled flue gas. The differences between O(2)/recycled flue gas (O(2)/RFG) combustion and general air combustion are also discussed. Experimental results indicate that the maximum concentration of CO(2) in O(2)/CO(2) combustion system is 95% as the feed gas is 30% O(2)/70% CO(2). The average concentration of CO(2) in the flue gas of O(2)/CO(2) coal combustion system is higher than 90% and much higher than that of O(2)/N(2) coal combustion system. This high concentration of CO(2) is beneficial for the separation of CO(2) from the flue gas by adsorption or absorption technologies. The maximum concentration of CO(2) in O(2)/N(2) combustion system is only 34% at the feed gas 50% O(2)/50% N(2), the concentration of CO(2) is increased with the concentration of O(2) in feed gas. By O(2)/CO(2) combustion technology, higher concentration of SO(2) is produced as the feed gas is 30% O(2)/70% CO(2) or 40% O(2)/60% CO(2), while higher concentration of NOx is produced as the feed gas is 20% O(2)/80% CO(2) or 50% O(2)/50% CO(2). The mass flow rates of CO(2), SO(2) and NOx in the flue gas are all increased with the ratio of recycled flue gas except for the feed gas 20% O(2)/80% CO(2). The enhanced mass flow rates of air pollutants in such O(2)/RFG combustion system are also beneficial for improving the control efficiencies of air pollution control devices. By O(2)/N(2) combustion technology, higher concentrations of SO(2) and NOx are produced as the feed gas is 21% O(2)/79% N(2). The results also indicate that the formation of NOx in general air combustion system is higher than that in O(2)/RFG or O(2)/CO(2) combustion system.     

Test run evaluation of a blend of fuel-grade ethanol and regular commercial gasoline: its effect on engine efficiency and exhaust gas composition

The purpose of this study is to evaluate the performance of a nationally manufactured vehicle on a test run with a blend of fuel-grade ethanol and commercial regular gasoline. The results showed that, when 10% ethanol was added to the gasoline, general engine performance was 5–10% higher, which was due to the increase in octane number of the mixture. Nevertheless, according to the lower heat value of the mixture, fuel consumption was approximately 5% higher than the regular gasoline. Carbon monoxide (CO) and hydrocarbon (HC) emissions were dramatically lower because, when ethanol (an oxygenate) was added to the fuel, it had an influence on combustion reaction improvement. On the other hand, nitrogen oxides (NOx) emissions increased due to the higher temperature in the combustion chamber.     

Nonintrusive optical measurements of aircraft engine exhaust emissions and comparison with standard intrusive techniques

Nonintrusive systems for the measurement on test rigs of aeroengine exhaust emissions required for engine certification (CO, NO(x), total unburned hydrocarbon, and smoke), together with CO(2) and temperature have been developed. These results have been compared with current certified intrusive measurements on an engine test. A spectroscopic database and data-analysis software has been developed to enable Fourier-transform Infrared measurement of concentrations of molecular species. CO(2), CO, and NO data showed agreement with intrusive techniques of approximately ?30%. A narrow-band spectroscopic device was used to measure CO(2) (with deviations of less than ?10% from the intrusive measurement), whereas laser-induced incandescence was used to measure particles. Future improvements to allow for the commercial use of the nonintrusive systems have been identified and the methods are applicable to any measurement of combustion emissions.     

Determination of Lean Burn Combustion Temperature Using Ultraviolet Emission

Measurements of the ultraviolet emission spectrum emitted from a lean burn premixed natural gas flame were taken over a range of flame temperatures using a fiber-optic/CCD spectrometer. Combustion temperatures were determined by two methods: by measuring the unburned oxygen in the exhaust and by calculating the temperature using the fuel and airflows. These temperatures were correlated to ratios composed of the integrated intensity of the long wavelength region of the OH band between 310 to 340 nm (ratio's numerator) and that between 305 and 310 nm (ratio's denominator). Average local combustor flame temperatures at the end of the combustion zone may then be determined by tracking these ratios during combustor operation. The sensitivity of these ratios yields a 0.8% change in the ratios every 20 degF with a precision of plusmn30 degF or plusmn1% at 3000 degF with 95 % confidence bounds demonstrating the feasibility of this technique for use as a potential control parameter for gas turbine combustors burning natural gas and air mixtures. This method is well suited for the low equivalence ratios (< 1) required to reduce NOx and CO emissions. Other methods using peak ratios of different emission bands exhibit nonlinearity, lower sensitivity and greater uncertainty.     

Influence of ethanol-diesel blended fuels on diesel exhaust emissions and mutagenic and genotoxic activities of particulate extracts

This study was aimed at evaluating the influence of ethanol addition on diesel exhaust emissions and the toxicity of particulate extracts. The experiments were conducted on a heavy-duty diesel engine and five fuels were used, namely: E0 (base diesel fuel), E5 (5%), E10 (10%), E15 (15%) and E20 (20%), respectively. The regulated emissions (THC, CO, NOx, PM) and polycyclic aromatic hydrocarbon (PAH) emissions were measured, and Ames test and Comet assay, respectively, were used to investigate the mutagenicity and genotoxicity of particulate extracts. From the point of exhaust emissions, the introduction of ethanol to diesel fuel could result in higher brake specific THC (BSTHC) and CO (BSCO) emissions and lower smoke emissions, while the effects on the brake specific NOx (BSNOx) and particulate matters (BSPM) were not obvious. The PAH emissions showed an increasing trend with a growth of ethanol content in the ethanol-diesel blends. As to the biotoxicity, E20 always had the highest brake specific revertants (BSR) in both TA98 and TA100 with or without metabolizing enzymes (S9), while the lowest BSR were found in E5 except that of TA98-S9. DNA damage data showed a lower genotoxic potency of E10 and E15 as a whole.     

300MW锅炉运行诊断及燃烧优化试验研究

针对某300MW锅炉排烟温度高、出力不足、煤耗高、NOx排放量高等诸多问题,进行诊断试验,结合锅炉实际提出整体优化方案,并在改造后对锅炉进行燃烧调整试验,使得锅炉效率提高0.8％,煤耗降低2.2g／kWh,NOx排放量降低381mg／m3,机组的整体经济性和环保性明显提高。     

Combustion of agro-waste with coal in a fluidized bed

In this study, a review of the studies done on the co-combustion of some agro-waste in a bubbling fluidized bed combustor (BFBC) having an inside diameter of 102 mm and a height of 900 mm is given. The agro-waste used to investigate the co-combustion characteristics were peach and apricot stones produced as a waste from the fruit juice industry, and olive cake produced as a waste from the olive oil industry. These are typical wastes for a Mediterranean country. A lignite coal was used for co-combustion. On-line concentrations of O₂, CO, CO₂, SO₂, NO _x and total hydrocarbons (C _m H _n ) were measured in the flue gas during combustion experiments. Variations of emissions of various pollutants were studied by changing the operating parameters (excess air ratio, fluidization velocity and fuel feed rate). Temperature distribution along the bed was measured with thermocouples. Emissions were also monitored from the exhaust. Various combinations of coal and biomass mixtures were tested. During the combustion tests, it was observed that the volatile matter from the biomass quickly volatilizes and mostly burns in the freeboard. The temperature profiles along the bed and the freeboard also confirmed this phenomenon. It was found that as the volatile matter of the biomass increases, combustion takes place more in the freeboard region. Better combustion conditions occur at higher excess air ratios. The results showed that co-combustion with these three proposed biomasses lowers the SO₂ and NO _x emissions considerably. CO and hydrocarbon emissions are lower at the higher excess air ratios.