Numerical simulation of the influences of catalytic wall on methane combustion characteristics in micro combustor

In order to study the effects of different catalytic walls on combustion characteristics, the premixed catalytic combustion characteristics of methane/air in micro combustor are studied. It lays the foundation for the combustion technology of hydrocarbon fuel in micro engine. Numerical simulation of flow and catalytic combustion in micro combustor was done by using laminar finite rate and second order upwind discretization methods. The results show that when wall temperature,CH4/O2 mole ratio and methane mass flow rate change, the influence of lower catalytic wall on the methane catalytic combustion efficiency is biggest, followed by side catalytic wall, the smallest is upper catalytic wall. The methane catalytic combustion efficiency unit area of lower catalytic wall is about three times of that of upper catalytic wall. The utilization of catalyst on lower catalytic wall is maximal . Therefore, when coating catalyst, the quantity of katalyst on lower catalytic wall should be appropriate more, moderate on the side catalytic wall, as little as possible on the upper catalytic wall. The influence disciplinarian and contribution rate of different catalytic wall on methane combustion have been gained. The optimized strategy of catalyst coating was put forward and reduced the cost of catalytic combustion.     

Multi dimensional numerical simulation of the combustion process on methanol fueled engine

The paper concludes the characters of methanol as a fuel in engines. Based on the kiva 3v program, it conducts the multi dimensional numerical simulation of the operation process in cylinder of a methanol fueled engine to obtain the detail information and performance graphic charts, as well as the real time data of pressure, temperature and so on. It is helpful for the research on methanol fueled engines. The results indicate that the methanol is a green alternative fuel and the methanol fueled engines have steady operations and lower emissions by comparing the numerical results with the data of gasoline engine.     

运行参数对微型内燃机微燃烧特性影响机理分析

微型内燃机微燃烧过程对当量比和转速变化非常敏感,采用层流有限速率模型和甲醇氧化反应机理对其预混层流微燃烧过程开展仿真研究,探讨当量比和转速对微燃烧特性的影响规律及临界运行参数。在此基础上,提出采用热着火理论和化学反应动力学理论探索当量比对微燃烧特性的影响机理。结果表明仿真与实验比较吻合。当量比从0.6增加到1.1时,燃烧速率增加,压力和温度增加,压力最高值增加约1.5E+6 Pa,温度最大值增加约1 300 K,此后随当量比增加,燃烧速率减小,压力和温度减小。研究还进一步揭示了当量比影响微燃烧特性的机理: 稀燃区当量比主要通过温度变化来影响微燃烧特性,随当量比增加,燃料浓度增加,燃烧释放的总热量增加,所以温度和压力增加,燃烧速率增加;浓燃区当量比主要通过氧气量变化来影响微燃烧特性,当量比越大,氧气量越不足,基元反应速率越小,所以燃烧速率越小,温度和压力越低。转速越高,燃烧时间越短,燃烧越不充分,所以温度、压力越低。受微燃烧相对热损大、驻留时间短的特征影响,微型发动机实现完全燃烧的运行区域较窄,其实现完全燃烧的稀燃极限约0.9,最高转速约6 000 r/min。这在设计微型内燃机时值得关注。     

Influence of indoor temperature on equivalent thermal resistance of green roof

绿化屋顶在节能设计中以附加当量热阻增大屋顶总热阻值,有效减少由屋顶进入室内的热量,降低室内空气温度。但根据已有的实验研究,绿化屋顶隔热特性与室内气温是耦合关系,随室内气温的变化,绿化屋顶会呈现出不同的隔热特性。用实验测试与数值模拟相结合的方法,分析在不同室内气温下绿化屋顶、参照屋顶与等效保温屋顶内表面温度与热流的变化。结果表明：室内气温会显著改变绿化屋顶的隔热性能,其当量热阻为与室内温度正相关的变量。在被动式建筑中,绿化屋顶更能充分发挥隔热功效,且具有不向室内传热的特性。     

Effect of space velocity on the performance of methane steam reforming in a plate micro channel reactor

A 2 D numerical simulation is conducted on the steam reforming reaction in a plate micro reactor by applying the general finite reaction rate model in the CFD software FLUENT and a detailed surface reaction kinetics mechanism. Catalyst space velocity(CSV) and gas space velocity(GSV) inlet mixture impact on the reaction is discussed. During the calculations, the space reaction effect is ignored and only the reaction of CH4 on catalytic surface is taken into account. Calculation results show that lower CSV or GSV can achieve high efficiency conversion of CH4 and H2 output; besides CSV and GSV, channel height is an important factor for the reforming performance of plate micro reactors.     

山地城市热环境及其聚落特征的关联分析

以重庆主城区为研究对象,利用Landsat 8传感器OLI和TIRS获取的遥感影像为数据源,进行城市聚落特征包括地形特征、土地利用等与地表温度的差异性分析。结果表明：城市的热环境空间分布差异较大,海拔高度对温度的影响强于地形起伏度;（NDVI、NDBI、MNDWI等）和地表温度的相关关系呈分段线性关系;不同土地利用类型的热强度和热变异程度差异明显,建设用地的温度最高且斑块温度间的变异性最强,虽然水体的平均温度最低,但斑块温度间的变异性却较高;从格网分析的结果可以看出,格网内部水体的“冷岛效应”明显、建设用地的“热岛效应”显著,耕地与自然植被面积的增加使得各空间格网温度更趋向于稳定。     

广东地区农村住宅室内热环境优化研究

广东地区新建农宅有向多层发展和天井消失的趋势,室内热环境因此而变化。为了解广东地区新建农宅室内热环境现状,选取有天井现代农宅、无天井现代农宅和传统农宅各一栋进行现场实测,在对比分析的基础上发现现代农宅室内热环境存在优化的空间。针对广东地区现代农宅存在的问题,借助计算机辅助分析的手法提出适宜的优化措施,屋面遮阳、增大天窗高度及天窗开口置于下风向是改善有天井多层农宅夏季室内热环境的有效措施,无天井现代农宅通过局部架空和窗口遮阳改善室内热环境效果显著。     

水淹胁迫对华南地区3种园林树种生理特征的影响

为了了解红荷、红苞木、樟树幼苗的抗涝能力,为筛选优良的抗涝树种提供依据,通过人工模拟水淹胁迫环境,测定这3种幼苗叶片的叶绿素等生理指标,用主成分分析法研究了这3种幼苗的抗涝性。研究结果表明：随着水淹胁迫时间的延长,红荷幼苗叶片叶绿素含量波动,红苞木和樟树小幅上升后下降;3种幼苗叶片的可溶性糖含量呈波动性上升的趋势;红苞木和樟树的蛋白质含量呈现波动性变化,红荷的蛋白质含量为降-升-降;红荷的叶片的超氧化物歧化酶(SOD)活性呈逐渐下降趋势,红苞木和樟树的SOD活性显著上升后下降;红荷、红苞木和樟树幼苗叶片的丙二醛(MDA)含量大幅增加后缓缓下降。3种幼苗在水淹28天期间内均有一定的抗涝性,采用主成分分析法得出幼苗的抗涝性大小为樟树>红荷>红苞木。     

The Effect of Contact Thermal Resistance on Temperature Distribution in the Tube-Mouth Region of High Temperature Heat Exchange Equipment

Heat transfer in the tube-mouth region of high temporature heat exchangeequipment was further analysed. The finite difference method(FDM)was employed for investigat-ing emphatically the effects of contact thermal resistance on heat transfer.Temperature distributionin the tube-mouth region with the different contact thermal resistance was found.The computation-al results were compared with that which were obtained with no contact thermal resistance,and thecorresponding heat transfer mechanism was fully analysed.     

基于多重表型分析的准确评价高粱抗旱性方法的建立

干旱是制约农业生产的重要非生物胁迫之一,因此作物抗旱性研究具有重要理论和应用价值。本研究对73份高粱材料萌发期和苗期的抗旱性进行了初筛,从中选择15份抗旱材料和6份敏感材料,通过室内和田间试验,获得干旱胁迫下幼苗的株高、叶长、叶宽等形态特征以及超氧化物歧化酶、丙二醛、过氧化物酶等生理生化指标的响应数据,并对高粱的抗旱性做进一步的验证,最终确定抗旱型材料1份,中等抗旱型材料1份,干旱敏感型材料2份。本研究建立了一套基于多重表型分析的高粱抗旱性研究新方法,即综合运用多种数据分析方法(包括隶属函数法、主成分分析法、聚类分析法),结合不同生长环境(田间试验和室内试验)和不同生育期(萌发期和苗期)高粱响应干旱胁迫的多种表型数据(形态特征、生理生化指标),通过多重比较高粱抗旱性评价结果的一致性,旨在系统、高效、准确地判定高粱的抗旱性,为高粱抗旱机制的研究和抗旱新品种的选育提供技术支撑。     

Genetics of resistance to 3 isolates of Ascochyta fabae on Faba bean (Vicia faba L.) in controlled conditions

Summary Genetics of resistance to Ascochyta fabae Speg. in Vicia faba L. was studied with a final objective to develop resistant faba bean varieties to Ascochyta blight. The study was conducted separately on 3 single spore isolates (AF10-2 and AF13-2 from Tunisia and AF4-3 from France) and belonging to different groups of virulence (GV1 and GV2). Important general combining ability (GCA) effects were found especially with isolates AF10-2 and AF4-3. Specific combining ability (SCA), although significant for the 3 isolates, was important only with AF13 -2, but less important than GCA. Additive gene effects were predominant to non-additive effects. Lines 29H and A8817 transmitted to their progenies resistance to the 3 isolates, whereas 14–12 and 19TB conferred resistance to their progenies only with isolates AF13-2 and AF4-3, respectively. In the material studied, resistance was generally controlled by dominant genes but also could be attributed to recessive genes although less frequent. Analysis of segregation in the F2 of 2 crosses between the resistant lines (A8817 and 29H) and the susceptible line (14–12) with isolate AF4-3 revealed dominant monogenic control at the level of leaves in the 2 resistant lines and, in addition, a recessive gene controlling resistance of stems. Non-allelic interactions were occasionally manifested and their origin appeared to be due to line 19TB. A recurrent selection scheme was proposed with the objective to develop improved open-pollination populations and synthetic varieties responding to the objective of the national Tunisian research programme on faba bean.     

Reciprocal monosomic analysis of frost resistance on chromosome 5A in wheat

Summary F₂ monosomic analysis and the direct comparisons between aneuploid series from different varieties of wheat suggest the likelihood of allelic variation. It is impossible however, from these studies to prove unequivocally that allelic variation exists. Some effects can be due to chromosome dosage rather than allelic variation. This disadvantage was overcome by using reciprocal monosomic analysis to study the genetic control of frost resistance on chromosome 5A in wheat. Data support the previous results obtained by F₂ monosomic and substitution analysis. The chromosome 5A has been shown to be the one which carries the major allelic differences that distinguish wheat varieties Chinese Spring, Rannyaya 12 and Mironovskaya 808 for frost resistance.     

Influence of development stage and host genotype on three components of partial resistance to leaf rust in spring wheat

Summary Latency period (LP), infection frequency (IF) and urediosorus size (US) of leaf rust were determined on primary leaves and young flag leaves of 18 spring wheat cultivars. A large growth stage effect and a large cultivar effect on all three components were observed. Partial resistance as measured by the three components was generally better expressed in the adult plant stage than in the seedling stage. Associated variation of the components was observed: long LP, low IF and small US tended to go together. The association was not complete, cultivars with clear deviations of this association for one of the components were found suggesting the existence of at least partly different genetic factors controlling the respective components. LP measured on flag leaves gave the most reliable results and, therefore, could best be used as a selection criterion in breeding programs for partial resistance.     

The effects of climatic variation in Europe on the yield response of spring wheat cv. Minaret to elevated CO2 and O3: an analysis of open-top chamber experiments by means of two crop growth simulation models

In the ESPACE-Wheat programme, 25 open-top chamber experiments were carried out in 1994, 1995 and 1996, on nine locations, divided over eight European countries. In most experiments, spring wheat cv. Minaret was subjected to two levels of atmospheric CO₂ and two levels of ozone. Grain yields in the control treatments (ambient levels of CO₂ and O₃) varied strongly between sites. Also, yield response to elevated CO₂ and O₃ showed great variation. The present study was conducted to determine whether climatic differences between sites could account for the observed variation.

Two simulation models were used for the analysis: AFRCWHEAT2-O3 and LINTULCC. AFRCWHEAT2-O3 simulates phenology, canopy development and photosynthesis in greater detail than LINTULCC. Both models account for the effects of radiation and temperature on crop growth. New algorithms were developed to simulate the effects of CO₂ and O₃. Weather data that were measured in the experiments were used as input, and simulated growth responses to CO₂ and O₃ were compared with measurements. No attempt was made to merge the two models. Thus two independent tools for analysis of data related to climate change were developed and applied.

The average measured grain yield in the control treatment, across all 25 experiments, was 5.9 tons per hectare (t ha⁻¹), with a standard deviation (SD) of 1.9 t  ha⁻¹. The models predicted similar average yields (5.5 and 5.8 t ha⁻¹ for AFRCWHEAT2-O3 and LINTULCC, respectively), but smaller variation (SD for both models: 1.2 t ha⁻¹). Average measured yield increase due to CO₂-doubling was 30% (SD 22%). AFRCWHEAT2-O3 expected a slightly lower value (24%, SD 9%), whereas LINTULCC overestimated the response (42%, SD 11%). The average measured yield decrease due to nearly-doubled O₃ levels was 9% (SD 11%). Both models showed similar results, albeit at lower variation (7% yield decrease at SDs of 6 and 4%). Simulations accounted well for the observation that, at elevated CO₂, the percentage yield loss due to O₃ was lower than at ambient CO₂.

The models predicted lower variation among sites and years than was measured. Yield response to CO₂ and O₃ was predicted to depend on the climate, with a predominant effect of temperature on the response to CO₂. In the measurements, these climatic effects were indeed observed, but a greater part of the variation was not related to light intensity, temperature, CO₂, or O₃. This unexplained variability in the measured dataset was probably caused by factors not accounted for in the models, possibly related to soil characteristics.

We therefore conclude that even perfect information on the climate variables examined in ESPACE-Wheat, i.e. light intensity and temperature, by itself would be insufficient for accurate prediction of the response of spring wheat to future elevated levels of CO₂ and O₃.