双尾管脉冲发动机的工作特性

为了系统探究双尾管脉冲发动机的工作特性,自行设计了功率为30 kW的Helmholtz型双尾管脉冲发动机,建立了脉冲发动机燃烧室内气流压力、温度及燃油消耗率的测试系统。分析研究了油门开度对燃烧室内气流压力特性、温度以及发动机工作频率相互之间的影响关系。试验结果表明,随着油门开度加大,燃油消耗率在1~4油门开度下显著增加,燃烧室压力幅值大致呈先减后增趋势,并在3油门开度下达到最小;燃烧室温度以及发动机工作频率均先增大后减小,并在3油门开度下达到最大。燃油消耗率与油门开度之间呈线性增长关系,燃烧室内气流温度与脉动频率均与油门开度之间呈现一致的倒U形关系,与气流压力脉动幅值呈现相反的U形关系。即双尾管脉冲发动机脉动燃烧工作所形成的自激振荡耦合关系,对应着燃烧室与尾管内脉动振荡气流的高脉动频率、低压力脉动幅值及高气流温度的相互耦合关系,反之亦然。本研究设计的600,800和1000 mm不同尾管长度条件下的双尾管脉冲发动机均能轻易启动并在1~3油门开度下稳定工作,表明双尾管脉冲发动机具有较好的声学条件,与一定油门开度相匹配,易形成良好的振荡燃烧耦合关系,实现稳定工作。     

165F 汽油机加速不起的原因

165F 汽油机为单缸四冲程发动机,因使用维修不当会引起加速不起的故障。当加大油门时转速不是升高,而是排气冒黑烟,甚至熄火。归纳有以下几种原因:1.化油器油针调整不当。主油针开度过大,加大油门时燃油进入汽缸太多,混合气过浓而燃烧不好,会排气冒黑烟;如开度过小,加大油门时汽缸进油量过少,空气太多而不能燃烧,会出现熄火。2.油管中有空气或化油器量孔阻塞,使进入化油器或汽缸的油量少。3.空气滤清器堵塞,进气量不足。4.化油器与汽缸体连接面变形,绝     

不同尾管数量的全浸入式脉动燃烧器传热特性试验

土壤消毒是决定设施栽培产量和品质的关键环节。将高燃烧强度、高传热效率的脉动燃烧技术与无污染、消毒效果佳的土壤蒸汽消毒技术相结合,基于30 kW的单个脉动燃烧器进行结构尺寸设计,在保证燃烧室相同且燃烧器拥有相同总流通面积的前提下,确定了包括单管、双管和三管3种尾管数量,设计了一种全浸入式脉动燃烧器传热特性试验装置。试验过程中将脉动燃烧器整体浸没埋入水中,针对主要影响因素包括油门开度、尾管数量以及有无去耦室,分别测量了3种尾管数量下试验装置的油耗、水温、烟气温度、蒸汽量等。试验结果表明：脉动燃烧器油耗随油门开度增加而增大,油耗呈现单管>双管>三管的现象;增大传热面积可明显强化脉动燃烧器的传热特性,三管的烟气侧传热系数为单管的1.10～1.15倍,相同工况下烟气侧脉动流传热系数达到稳态流的5.12～5.66倍,三管蒸汽量为单管的1.32～1.67倍,热效率为单管的1.11～1.13倍,且当油门开度处于中间油门开度450°&450°时脉动燃烧器各项参数达到最优值。尽管去耦室换热性能较弱,但去耦室除降低排烟温度,提高系统热效率,还能有效降低排气噪声和减少油耗量。确定基于土壤蒸...     

中比例甲醇汽油台架试验及仿真研究

为了研究中比例甲醇汽油对电喷发动机的性能影响情况,对中比例甲醇汽油（M30和M40）进行发动机台架试验和仿真研究。发动机燃用甲醇汽油的动力性对比试验结果表明：发动机在未作任何改造的情况下,同93#汽油相比,燃用M30和M40的发动机动力性能均有所下降,其中M40的功率下降最多。中比例甲醇汽油的常规排放物试验表明：中比例甲醇汽油对发动机的HC、CO和NOX的排放改善均比较明显。从非常规排放物的模拟结果来看,M40的甲醛排放最高,93#汽油的甲醛排放最低。     

油锯曲轴箱漏气的快速检修

故障现象:漏气不严重者发动机起动后转速快,爆燃声连续而密,锯链在小油门情况下也运转较快,而且调节化油器供油量也无效,当锯切木材时,加大油门发动机也因无力而停动。漏气严重时,发动机不能起动,或起动后高速转一会发动机便马上熄火故障原因:若曲轴箱漏气不严重,在活塞往上运动时,曲轴箱内压力差减小,进入曲轴箱及气缸内的混合气很稀,缸内富氧,点火后燃烧快,但爆燃后气体对活塞顶部压力小,故一加负载(锯木),发动机因功率不足熄火。若曲轴箱漏气严重,则箱内压力与大气压相     

脉动燃烧技术及其在林业中的应用

脉动燃烧是指在一定声振条件下发生的一种周期性燃烧，其燃烧室内压力强度、气流速度、温度及热释放效率等参数随着时间呈周期性变化，是一种特殊的不稳定燃烧过程，具有燃烧效率高、燃料经济性好、运行环境友好等优点。研制基于脉动燃烧技术的林业作业装备对于提高林业生产效率、促进环保高效燃烧技术的发展具有重要意义。文中概述了脉动燃烧技术的工作原理、特点及发展现状，介绍了脉动燃烧技术在林业病虫害防治、木材干燥和土壤消毒中的应用，并在分析脉动燃烧技术的不足及其在林业作业应用中存在问题的基础上，提出脉动燃烧技术在林业作业应用中的发展方向。     

大气二氧化碳浓度倍增对闽楠光合性状的影响

对在照度为5000lx、大气CO2体积分数为700×10-6环境下生长3个月的闽楠PhoebebourneiHemsl.Yang进行了研究.结果表明:大气CO2体积分数倍增将使闽楠植株叶片叶绿素含量降低28.7%,其中叶绿素a、b分别下降了28.6%、19.8%,类胡萝卜素上升2.8%,叶绿素a/b从1.95下降到1.55.长期高体积分数CO2处理使叶片可溶性糖含量降低2.45%,可溶性蛋白含量降低53.91%,暗呼吸速率下降95.6%,光呼吸速率下降43.7%;短期内CO2加倍处理,光合速率上升21.76%;长期处理,则下降89%.这表明,短时CO2体积分数加倍处理使植物的表观光合速率明显增加;长期处理明显抑制了闽楠的光合作用,出现了严重的光合适应现象.闽楠光合作用和呼吸作用的减弱致使整个代谢水平下降.     

冷却剂参数对铣槽喷管低周疲劳寿命的影响

采用有限体积流固耦合计算方法、非线性有限元热结构耦合分析方法和局部应变法研究大面积比铣槽喷管三维再生冷却槽道在循环工作条件下的热结构变形与低周疲劳寿命,并对比分析了冷却剂质量流量与入口温度对铣槽喷管疲劳使用寿命的影响。计算结果表明,铣槽喷管热结构响应呈现复杂的三维效应,应变较大位置主要分布在与肋连接的内衬区域,喷管中部的残余应变量最大;冷却槽道低周疲劳寿命分布和热结构响应基本一致,最小寿命位于喷管中部与肋相连的内衬区域燃气侧;随冷却剂质量流量增加,铣槽喷管低周疲劳寿命不断提高;随冷却剂入口温度增加喷管尾部低周疲劳寿命值不断降低,而喷管中前部的低周疲劳寿命值却不断提高,当冷却剂入口温度为280K左右时,本文的铣槽喷管总体使用寿命达到最大。      

二甲醚发动机燃料喷射及其对燃烧和排放影响

指出了二甲醚作为柴油机清洁替代燃料,为实现机械供油系统下达到Ⅳ阶段及更高排放标准提供了一条技术路线,二甲醚的物性使得喷射过程与柴油的有较大不同。在一台2102二甲醚发动机上研究了二甲醚燃料的喷射、燃烧和排放特性。试验结果表明:发动机转速对燃油喷射正时具有显著的影响;二甲醚的滞燃期短,供油提前角的变化主要是使整个燃烧过程发生平移;二甲醚发动机的供油提前角对NOx排放有显著影响,而对HC和CO的影响较弱。     

冬运机械的技术使用问答(续)

二、防冻预热小刘:为使发动机保温,除了谈过的断开机油散热器以外,给发动机罩穿上保温被也是一个措施吧! 王师傅:对!给发动机罩和水箱穿上保温被,在保温被内加入8至10毫米厚的棉花层或卫生绒,外面再包一层人造革防潮,起的保温效果还不小呢。还有一些保温措施,如保持档泥板以及发动机罩的完整性;对风冷式发动机(如T-138)可在鼓风机进风口处加装阻风环,以减少冷空气的侵入;驾驶中根据水温表读数适当调节百叶窗及水箱帘的开度;用毛毡或棉织物将蓄电池封严。当然,上面谈的仅是行车过程中的一些保温措施,另外还有在停车     

汽车尾气降解材料测试室测试系统设计

为了测试各种光催化材料对汽车尾气的降解效能，研究设计了汽车尾气降解测试室，该装置用于对NO、CO2、O2、CO、HC浓度的瞬态检测分析，并可对检测数据进行处理，显示、打印和输出检测结果。     

汽油车怠速污染物的测量与调整

汽油车怠速下排放的CO和HC严重污染环境。随着国家标准的要求日趋严格,如何使国产汽油车排放符合国家标准是非常重要的。本文介绍了车辆检测中汽油车怠速下排放的污染物的测量方法,以及如何调整怠速使CO和HC的浓度符合国家标准。     

Fuel consumption and exhaust emissions in the process of mechanized timber extraction and transport

The paper focuses on the determination of fuel consumption (CO₂ emission) and exhaust emissions such as CO, HC, NO_x, and PM in the process of timber extraction and transport. A complex assessment of fuel consumption and exhaust emissions was performed for the entire, fully mechanized supply chain including, tree felling, delimbing, and bucking with a harvester, timber extraction with a forwarder and transport with a truck. The performed investigations determined unit exhaust emissions (referred to 1 m³ of timber) for the entire technological process and its individual stages. The investigations of the exhaust emissions and fuel consumption were performed under actual conditions of typical forest operations and transport. State-of-the-art portable emissions measurement system equipment was used for the measurements. The fuel consumption was determined through the carbon balance method. The investigations were performed for the process of extraction and transport of pulpwood. The measurements were performed on location in the town of B?bnik?t near Poznań, in a pinewood forest, typical of this part of Europe. The analysis includes the transport of timber to the lumberyard on a distance of 31.4 km. The total fuel consumption for the entire mechanized supply chain was 2.10 dm³/m³. The total exhaust emissions, however, amounted to: CO—8.91 g/m³, HC—1.19 g/m³, NO_x—45.32 g/m³, PM—4.04 g/m³.     

CO_2浓度升高对落叶松针叶质膜过氧化物产量的影响

以10 a生落叶松幼树为试验对象,在CO_2浓度升高和对照处理的开顶式气室(OTC-Ⅰ型)内,研究分析高浓度CO_2对其针叶质膜过氧化物产量的影响,结果表明:短时间(60 d)高浓度CO_2处理条件下,MDA含量降低,细胞质膜过氧化程度减轻;但长时间(超过70 d)处于高浓度CO_2条件下则会严重损伤细胞,导致植物体受害。MDA与O2-·产生速率存在正相关关系,但并不显著,在短时间(60 d)CO_2浓度升高条件下,O2-·产生速率与H2O2含量降低;长期高浓度CO_2处理下,O2-·产生速率与H2O2含量略有上升。     

Drought and the diurnal patterns of stem CO2 efflux and xylem CO2 concentration in young oak (Quercus robur)

A young potted oak (Quercus robur L.) tree was subjected to drought by interrupting the water supply for 9 days. The tree was placed in a growth chamber in which daily patterns of temperature and radiation were constant. The effects of drought on the water and carbon status of the stem were examined by measuring stem sap flow rate, stem water potential, stem diameter variations, stem CO(2) efflux rate (F(CO2)) and xylem CO(2) concentration ([CO(2)*]). Before and after the drought treatment, diurnal fluctuations in F(CO2) and [CO(2)*] corresponded well with variations in stem temperature (T(st)). Daytime depressions in F(CO2) did not occur. During the drought treatment, F(CO2) still responded to stepwise changes in temperature, but diurnal fluctuations in F(CO2) were no longer correlated with diurnal fluctuations in T(st). From the moment daily growth rate of the stem became zero, diurnal fluctuations in F(CO2) became closely correlated with diameter variations, exhibiting clear daytime depressions. The depressions in F(CO2) were likely the result of a reduction in metabolic activity caused by the lowered daytime stem water status. Xylem [CO(2)*] showed clear daytime depressions in response to drought. When the tree was re-watered, F(CO2) and [CO(2)*] exhibited sharp increases, coinciding with an increase in stem diameter. After resumption of the water supply, daytime depressions in F(CO2) and [CO(2)*] disappeared and diurnal fluctuations in F(CO2) and [CO(2)*] corresponded again with variations in T(st).     

柴油机电控单体式喷油器（EUI）开启压力测试装置

通过对柴油机电控单体式喷油器（EUI）结构特点与工作原理的研究,设计一套便捷、快速、精确的柴油机电控单体式喷油器（EUI）开启压力测试装置.装置采用气压驱动喷油器挺杆,喷油器加压使其开启喷油,计量装置采用安装压力传感器,通过压力传感器获得加在喷油器挺杆上力的变化信号,利用高性能单片机编程来处理此信号,最后输出喷油器开启喷油的油压变化规律曲线,测出喷油器开启压力数值.     

A study of emissions and marker gases from smouldering combustion in Larix gmelinii plantations of the Daxing'an Mountains

Underground fires are characterized by smoul-dering combustion with a slow rate of spread rate and with-out flames.Although smouldering combustion releases large amounts of gaseous pollutants,it is difficult to dis-cover by today's forest fire monitoring technologies.Carbon monoxide (CO),nitrogen oxides (NOx) and sulfur dioxide(SO2) were identified as high concentration marker gases of smouldering combustion-easily-be monitored.Accord-ing to a two-way ANOVA,combustion time had a signifi-cant impact on CO and NOx emissions;smoldering-depth also had a significant impact on NOx emissions but not on CO emissions.Gas emission equations were established by multiple linear regression,Cco=156.989-16.626 t and CNOx=3.637-0.252 t-0.039 h.     

Toxicity index and the time taken to incapacitate mice under combustion gases of burning wooden materials

The purpose of this study was to investigate the toxicity of combustion gases from burning wooden materials. The toxicant index and mice exposure experiment were used to evaluate the toxicity index. The time taken to incapacitate mice under the impact of burning 19 solid wood species and 7 kinds of plywood were investigated. The results showed that the toxicity index of burning solid wood ranged from 1.5 to 2.5, and its main toxicant was CO₂. The toxicant index of burning plywood was higher, ranging from 3.0 to 6.0, and its main toxicity was NO_x. A good correlation was observed between the time taken to incapacitate mice (Xs) and the weight loss rate of burning solid wood. When the concentration of CO was higher than 1% in the exposure chamber, the mice stopped their activity within 2min. The time taken to incapacitate mice (Xs) and the minimum concentration of O₂ in the exposure chamber could be represented by a positive linear regression formula. The concentrations of O₂ and CO₂ exhibited a positive effect and the concentration of CO had a negative effect on the Xs values of mice.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002