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1.
旋流泵性能及内部流场试验分析 总被引：5，自引：5，他引：0
为了研究旋流泵性能及内部流场特性,在32WB8-12型样泵型式试验和5孔球形探针无叶腔流场测量基础上,阐明旋流泵抽吸及扬程和汽蚀形成原理,得出流量-汽蚀余量性能曲线为下降抛物线形;基于重组化群k-ε湍流模型对模型泵内部三维流动进行数值计算;通过流场测试与数值模拟对比分析,证明数值计算达到一定程度逼真性和精确度。结果表明,旋流泵内部流动主要由贯通流等组成;叶轮区域呈强制涡特征,存在相对轴向旋涡运动;无叶腔区域类似于组合涡,存在回流、循环流和自由涡运动,呈非轴对称、非定常流动,紊乱程度相当高,这是造成旋流泵效率偏低的主要原因。 相似文献
2.
旋流泵含气混输数值计算及涡室流场探针测量 总被引：2，自引：2，他引：0
为探索旋流泵内部流场及气液两相流混输特性,该文通过32WB8-12型旋流泵外特性试验和泵最优工况流场五孔探针测量,得出泵性能曲线和5个测点静压ps、绝对速度v、圆周速度vu、径向速度vr和轴向速度vz分布情况。针对N-S方程中四项力在气液两相流动中的具体表现特性进行力学分析,说明了泵内部两相流动特点及关联因素之间约束关系。阐明了旋流泵含气混输抽吸和扬程形成的基本原理,及空化和气液两相流混输的不同特点。选择性能试验最优工况,基于改进重组化群k-ε湍流模型(RNG k-ε模型),应用Fluent软件对泵内部流场进行数值模拟,得到了3个轴面静压、速度矢量和含气率分布图。证明泵进口轴向运动为主流,气体主要集中在压力较低的进口区域。气相的引入,其微团与液相尺寸、形状及弹性模量的不同,造成两相流场惯性力、摩擦力和浮力发生变化,由此解释了外特性变化及气液抽吸与内部流动之间定性的因果关系。探讨了旋流泵内部气液两相流动速度场和过流通道发生畸变的基本原理,为建立旋流泵内部气液及空化流动模型提供实例。 相似文献
3.
为了研究固液两相流离心泵输送含有多组分介质的规律,该文以一台离心式固液两相流泵作为研究对象,使用Fluent中的Eulerian多相流模型描述固液两相流动特征。首先选取了3组直径不等的单分散颗粒群作为固相,发现粒径越大,工作面的颗粒浓度越高,固相离析作用越明显。随后选取了5组直径递增的颗粒群作为固相,每组颗粒群包含两组相同的单分散颗粒群,结果表明同一台泵内两组相同的颗粒群的运动特征相同,同时两组相同的颗粒群的浓度之和、速度之和及外特性与单独输送单分散颗粒群的变化规律相似。最后选取了5组粒径不相等的两组颗粒群组合而成作为固相,大颗粒群粒径不变,小颗粒群粒径递增,结果发现不等直径双颗粒群组合与单颗粒群或者等直径双颗粒群有所区别,大小颗粒在内部流动上表现出了独立性和相互影响的现象,小颗粒群的运动特征与单分散颗粒群类似,由于小颗粒的存在使粒径均为0.7 mm的大颗粒体积分数分布发生了变化,小颗粒使大颗粒在泵内分布更加均匀,随着小颗粒群粒径增加,泵的扬程、效率和总压差先急剧上升随后缓慢下降,粒径为0.7和0.15 mm组合时扬程为80.12 m,达到最高值。该研究可为进一步研究多组分介质对泵性能的影响提供参考。 相似文献
4.
基于Mixture多相流模型计算双流道泵全流道内固液两相湍流 总被引：3，自引：11，他引：3
采用Mixture多相流模型、扩展的标准k-ε湍流模型与SIMPLEC算法,应用计算流体力学软件Fluent对双流道泵全流道内的固液两相湍流进行了数值模拟,并将计算结果与清水单相流数值模拟及泵外特性性能试验进行了对比,揭示了不同粒径及颗粒体积浓度条件下双流道泵全流道内的固液两相流动规律.研究结果表明:在叶轮流道内,固相体积浓度分布极不均匀,颗粒主要集中于叶轮出口处的工作面和后盖板上,但是随着颗粒浓度和粒径的减小,会出现颗粒向背面迁移的趋势;在蜗壳流道内,颗粒主要集中于靠近蜗壳出口侧的流道区域,颗粒运动轨迹紊乱,少部分颗粒脱离叶轮后能直接从蜗壳出口流出,大部分颗粒撞击蜗壳壁面,留在蜗壳内转动数圈才能流出;颗粒浓度变化对固相的离析作用影响相对较小;粒径变化对固相的离析作用影响较大,粒径越大,颗粒撞击点愈加集中于叶轮工作面,固相的离析作用越明显;相同体积流量下,泵进出口总压差随颗粒浓度和粒径的增加而减小. 相似文献
5.
不同叶顶间隙对斜流泵性能影响的数值分析 总被引：1，自引：3，他引：1
斜流泵具有高效,启动特性好,运行工况宽等特点。目前斜流泵设计时,无法定量评估叶顶间隙对性能影响的敏感性。为了揭示不同叶顶间隙值对斜流泵内部流场和性能的影响,给定叶顶间隙选取的范围。分别选取无叶顶间隙和叶顶间隙分别为0.5,1.0,1.5 mm共4种设计方案的斜流泵为对象,基于剪切压力传输模型(shear stress transport,SST k-ω)湍流模型,SIMPLEC算法与块结构化网格,对斜流泵内部流场进行数值模拟和试验验证。结果表明,叶顶间隙为0.5 mm时,可以有效抑制斜流泵的扬程-流量正斜率特性,此时斜流泵的效率值最高;无叶顶间隙时,斜流泵扬程-流量正斜率特性较为明显;叶顶间隙为1 mm时,数值模拟与试验结果吻合较好,SST k-ω模型可较好模拟斜流泵叶顶间隙区流动特征,性能预估结果具有一定的可信度。在小流量工况下,叶顶间隙为0.5 mm可有效抑制斜流泵的正斜率不稳定特性。小叶顶间隙0.5mm时,斜流泵水力性能最优;叶顶间隙增大时,叶顶泄漏流动逐渐显著,叶轮出口近壁区轴面流速和涡量分布规律显著变化,表明叶顶间隙直接影响叶轮轴面速度分布规律和叶片负荷分布规律,由于受壁面摩擦阻力和液体黏滞阻力的影响,叶轮轮毂和叶顶间隙侧的叶轮轴面速度较小;叶顶间隙增大时,叶轮轮毂和叶顶间隙侧叶片负荷急剧衰减,影响叶片的做功能力。同时,叶顶泄漏流动区域与叶片主流区域的掺混效应,使叶片轮缘的低速区扩展到叶轮流道内部的主流区域,引起叶轮流道内部主流流动的堵塞效应,产生二次流动、漩涡等流动不稳定现象。上述研究结果,揭示了叶顶间隙对斜流泵内部流场和性能的影响机理,为斜流泵叶顶间隙的选择提供了理论依据。 相似文献
6.
半开式叶轮离心泵气液两相条件下内部流动特性分析 总被引：1，自引：1，他引：0
半开式叶轮离心泵输送气液两相流时,其性能经常随入流含气率（α）的增加而下降,主要由内部的气液两相不稳定流动造成。为解决传统欧拉双流体模型不能考虑气泡直径变化及气泡形变的问题,采用一种群体平衡模型（Musig模型）数值计算了某设计比转速为88.6的半开式叶轮离心泵在不同入流含气率下的内部流场,并进行了试验验证。研究结果表明：模型泵在1 000 r/min可输送液体的最大入流含气率为4.6%;α>3%以后,Musig模型由于能表征气泡形态及破碎与聚合过程等气液两相流演化规律,其外特性计算结果比欧拉-欧拉双流体模型准确,且与可视化试验流型测试结果较为吻合;α=4%时扬程系数和效率与试验结果的最大误差分别为1.6%和5%;随着入流含气率的增加,叶轮和蜗壳流道内逐步出现均匀泡状流、聚合泡状流、气穴流和分离流等流型分布,设计流量下α≤1%时以均匀泡状流为主,α=3%时以聚合泡状流为主,α=4%时以气穴流为主,α≥4.2%时出现分离流并逐渐堵塞流道;叶顶间隙是影响泵内气液两相流型分布的重要原因,叶轮流道中存在大尺度漩涡和出口回流现象,且随着含气率的增大越发明显,进而在高含气率区域引发较大的湍动能分布,加剧了泵内部的不稳定流动,最终导致α≥4.6%后的泵空转。该研究可为综合分析离心泵内部不稳定流动规律提供一定参考。 相似文献
7.
基于数值模拟的微型溴化锂屏蔽泵的性能分析 总被引：2，自引：2，他引：0
针对现有单级溴化锂屏蔽泵存在效率低、能耗高的缺点,研究开发了两级叶轮微型溴化锂屏蔽泵。设计两级微型溴化锂屏蔽泵机泵一体结构以及两级屏蔽泵的水力部件,包括叶轮设计、径向导叶和螺旋形涡室组合设计等。利用CFD软件FLUENT,对两级屏蔽泵进行流场模拟,得到了内部流场的分布情况。由此分别以溴化锂和清水为介质进行了性能预测,与设计值进行比对,结果符合设计要求。经样机试验验证,在相同流量下,两级微型溴化锂屏蔽泵比现有单级微型溴化锂屏蔽泵扬程高约1 m,机组效率高约1.6%。设计的两级屏蔽泵的扬程和机组效率模拟值与试验值比较接近,初步验证了模拟可信,设计方法可行。 相似文献
8.
沙粒粒径与含沙量对离心泵空化特性的影响 总被引：3，自引：1，他引：2
为了研究沙粒粒径与含沙量对离心泵空化特性的影响,对含沙条件下与清水介质下离心泵内部空化流场进行数值计算.所采用沙粒粒径分别为0.005、0.010、0.015 mm,含沙量分别为0.5%、1.0%、1.5%.通过对清水介质外特性与平头圆柱空化流动进行数值计算并与试验结果相对比,验证算法的可靠性.计算结果表明:含沙量为1.0%时,随粒径逐渐增大,沙粒对空化的影响表现为先促进、后抑制;沙粒粒径为0.010 mm时,随含沙量不断增多,沙粒对空化的影响表现为先促进、后抑制.高压条件下,清水介质中无空化泡产生,含沙水流中均有少量空化泡产生.空化充分发展时,与清水介质相比,含沙水中空化泡分布表现为先增大、后接近、再变小.在沙粒磨蚀与空蚀的共同作用下,含沙水流条件下的扬程均低于清水介质下的扬程,且分别随粒径、含沙量的增加,逐渐减小. 相似文献
9.
为了阐明螺旋角对凸轮泵转子腔内部流量特性的影响规律,揭示螺旋角和凸轮泵特性曲线的定量关系,基于FLUENT动网格技术和RNG k-ε湍流模型,对凸轮泵转子腔内部进行三维瞬态流动数值计算,比较了9种螺旋角凸轮泵转子腔内部流量特性,揭示了螺旋角对转子腔内部瞬态流动结构的影响机制,并通过理论计算及试验验证数值预测分对比析,其相对误差在2.5%~5.7%,具有较高的准确性。研究表明:螺旋角对凸轮泵流量特性及泵腔内部流动有显著影响,相比直叶转子,螺旋转子出口的平均流量和流量脉动幅值均明显降低,从而有效抑制转子腔内二次流、旋涡结构与转子间隙区速度突变;螺旋角为45°~60°时,泵出口平均流量达峰值,泵出口流量脉动幅值最低,转子腔内部流动结构较好,结果表明凸轮泵转子腔最优螺旋角取值为45°~60°。该研究可为凸轮泵转子优化设计提供参考。 相似文献
10.
基于CFD的潜水轴流泵性能分析及其特性试验 总被引：1，自引：1，他引：0
为了研究高转速轴流泵性能预测问题,采用圆弧法和流线法完成550比转速QY90-4.4-1.5轴流式潜水泵叶轮和导叶水力设计。采用计算流体动力学(CFD)对泵性能进行预测,运用Pro/E软件完成泵流道三维实体造型和非结构网格划分,基于标准k-ε湍流模型进行泵内部流场数值模拟,得到模型泵性能预测数据和曲线。在样机型式试验及综合分析基础上,发现实测与预测性能参数吻合程度较高,由于对回流及二次流等的模拟还存在欠缺,在偏离额定工况较大时泵流量-扬程、流量-轴功率和流量-效率曲线产生一定的误差。通过分析最优工况叶片表面压力和相对速度分布,揭示叶片头部因液流撞击形成较大压降梯度,背面进口边稍后是较宽的低压汽蚀危险区。叶片表面速度沿半径逐渐增大,基本上没有径向分速度。总体符合速度环量沿半径均匀分布的假设。 相似文献
11.
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
12.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
13.
《中国生态农业学报》2014,(8)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
14.
Aleš Lebeda Ivana Doležalová Eva Křístková Barbora Mieslerová 《Genetic Resources and Crop Evolution》2001,48(2):153-164
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions. 相似文献
15.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献
16.
Thomas Larsen Jesper Luxhøi Jakob Magid Lars Stoumann Jensen Paul Henning Krogh 《Biology and Fertility of Soils》2007,44(1):59-68
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization
and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition
with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the
decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots
with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass,
soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration,
N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially
(<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation
in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils,
indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but
the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation
for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community
performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea. 相似文献
17.
《中国生态农业学报》2014,(7)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
18.
《中国生态农业学报》2014,(6)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
19.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
Abstract A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species. 相似文献
20.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils. 相似文献