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喷射参数对柴油HCCI复合燃烧过程燃烧效率及散热损失影响的研究 总被引:1,自引:0,他引:1
在复合燃烧模式下研究了喷射参数对燃烧效率、散热损失和热效率的影响。试验结果表明,改变多脉冲喷射定时可控制预混燃烧放热幅度,影响NOx与HC和CO排放的折中关系。多脉冲喷射定时提前,NOx排放减少,但HC和CO增加,导致燃烧效率降低。在平均指示压力0 78MPa下,当采用复合燃烧模式,随主喷射后推,主喷射定时为3°CAATDC时,可获得最高燃烧效率,同时NOx排放仅为280×10-6,烟度为0 4BSU,相对此主喷定时,提前或拖后喷射都会使HC和CO排放增加,从而造成燃烧效率降低。 相似文献
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针对重载柴油机实现高效清洁燃烧进行了燃烧控制策略的研究.实验在一台拥有高压共轨系统、废气再循环系统、可变增压系统以及推迟进气门关闭定时系统的单缸实验发动机上进行.实验结果表明,当平均指示压力低于1.1 MPa时可以采用高EGR率的低温燃烧策略.其中,基于不同负荷工况高效清洁燃烧,需要配合进气增压、推迟进气门关闭定时技术以及不同的喷油模式.在低负荷工况下,单次早喷模式及高EGR率可以实现高的热效率以及低的NOx与碳烟排放.在中负荷工况下,采用多脉冲喷射模式及高EGR率协同作用,在降低化学反应速率的同时增强了混合,避免了因为局部不均匀而导致的碳烟排放过高.高的增压度提高了缸内充量密度,有效降低了NOx、碳烟、CO及HC排放,提高了热效率.研究结果还显示,在推迟进气门关闭定时系统的帮助下,采用多脉冲喷射以及高的增压压力,可以在保持高的热效率的同时进一步降低NOx以及碳烟排放. 相似文献
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《柴油机设计与制造》2006,14(1):55-56
均质充量压缩点火(HCCI)和高预混合燃烧(HPC)可以大大降低NOx和颗粒物的排放,但是这两种燃烧方式在全负荷工况时的HC和CO排放量太高。为了能满足2008~2010年生效的柴油机欧Ⅴ排放标准,IFP公司和Valeo公司共同合作开发出了“窄油束锥角直接喷射NADI”(“Narrow Allgle Direct Injection”)的燃烧方式,此燃烧方式采用了油束锥角非常小的直接喷射和创新的进气系统模块,显著降低了NOx排放,而且并没有因此使燃油耗增加。 相似文献
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基于调制多脉冲喷油模式的柴油预混合燃烧和排放特性的研究 总被引:1,自引:1,他引:1
在MULINBUMP-HCCI燃烧系统基础上,通过柔性调制多脉冲喷射的脉冲脉宽和间隔,形成了不同的喷油模式,以研究调制的多脉冲喷油模式对早喷HCCI燃烧和排放的影响。试验结果表明,改变多脉冲喷油模式,可以提高HCCI热效率,获得更高的输出功率,同时保持低的NOx和碳烟排放。5次和6次多脉冲喷射,递增式喷油方式具有很大的优势;对比不同次数的多脉冲喷射发现,增加多脉冲喷射次数可以扩大HCCI的负荷范围、提高指示热效率和降低CO排放。在110°CABTDC喷油定时,6次多脉冲喷射递增喷油方式6PIM相对于5次多脉冲喷射5PIM喷油方式的pIMEP和指示热效率分别提高了27.6%和13%,而CO排放减少了230%。 相似文献
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基于电控高压共轨燃油系统的多脉冲复合控制燃烧系统 总被引:6,自引:3,他引:6
为了实现柴油机NOx和碳烟超低排放的目标,提出了基于电控高压共轨燃油系统的多脉冲复合控制均质压燃(简称HCCI)燃烧系统.该系统应用电控共轨燃油系统对燃油喷射规律实现多脉冲灵活控制,通过提前角大于上止点前90°的多次脉冲喷射,成功控制了预混合气的形成、着火和燃烧过程.从小负荷直到平均有效压力高达0.79 MPa的大负荷,均成功实现了以预混压燃燃烧为主要特征的燃烧过程,使柴油机的烟度始终能够控制在0.5 BSU以下,HC排放小于40×10-6,而NOx大幅度降低至240×10-6. 相似文献
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MULINBUMP HCCI燃烧控制特性的试验和数值模拟 总被引:2,自引:1,他引:2
通过试验和数值模拟方法研究了MULINBUMP-HCCI燃烧控制特性.发动机试验表明,通过控制多脉冲喷射参数可以控制预混合气的形成,从而控制燃烧放热速率,获得很低的排放水平.在不采用废气再循环的条件下,NOx排放在低负荷时只有11×10-6,高负荷时也不超过250×10-6,烟度则始终小于0.5 BSU.对多脉冲喷射预混合气形成历程的CFD数值模拟表明,不同的多脉冲喷射定时在混合气形成过程中形成不同的浓度和温度分层,从而引起燃烧特性的变化.通过控制多脉冲喷射参数来控制HCCI燃烧相位和燃烧速率是一种实用、有效的策略. 相似文献
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Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden. 相似文献
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《热能动力工程》2014,(5)
正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%. 相似文献
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The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°, −5°, +5°, +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods. 相似文献
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A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified. 相似文献
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As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied. 相似文献
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The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σred = σ1 β + (1 − β)σi, where: σ1-maximal principal stress, σi-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures. 相似文献
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Jaime Massanet-Nicolau Alan Guwy Richard Dinsdale Giuliano Premier Sandra Esteves 《International Journal of Hydrogen Energy》2010
Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H2 kg−1 VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min−1 successfully prevented a decline in hydrogen production and resulted in a yield of 27.0 L H2 kg−1 VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production. 相似文献