共查询到20条相似文献,搜索用时 46 毫秒
1.
仿生非光滑水田犁壁的设计及田间应用试验 总被引:1,自引:0,他引:1
水田犁田间作业时土壤对犁壁的严重粘附,将导致犁耕阻力增加、油耗增大、耕作质量和生产效率降低。经过大量的试验研究,已发现典型土壤动物蜣螂体表的减粘降阻和脱附效应,并据此开发了仿生犁壁。在前期研究基础上,考察仿生非光滑水田犁壁面上几何非光滑结构单元的尺寸和分布对犁耕阻力的影响,进行了设计参数优化,研制出具有减粘降阻性能的仿生非光滑水田犁壁。田间对比测试表明:仿生非光滑水田犁壁与普通光滑水田犁壁相比,降低犁耕阻力15.9%~18.0%,减少油耗11.9%,提高生产率20.5%。该犁壁耕翻的碎垡率高,耕作质量良好,有较好的实际应用前景。 相似文献
2.
3.
减粘降阻仿生犁壁的研究 总被引:23,自引:7,他引:23
在仿生表面改形和表面改性研究基础上,根据机引犁壁工作特性,研制出具有减粘降阻功能的仿生犁壁。实验室试验及田间运行结果表明,该犁壁可比普通犁壁减少油耗5.6%~12.6%,降低犁耕阻力15%~18%,并具有较好的脱土性和耐磨性 相似文献
4.
5.
6.
针对当前铧式犁在棉田土壤犁耕作业过程中易黏附、阻力大、能耗高等问题,立足两种典型棉田土壤,以犁体、棉田土壤和两者之间的相互作用为研究对象,提出犁体曲面模型优化和表面结构仿生相结合的方法。以穿山甲体表的鳞片三角圆弧状结构和蜣螂体表的凸包结构相结合作为仿生原型,研制一种棉田仿生脱附减阻犁体,分别对两种棉田土壤的物理和化学特性进行试验测定并建立离散元模型。进行传统犁体与仿生犁体的耕作过程仿真与试验,在1号土样中仿生犁体相对传统犁体减阻5.4%,土壤减粘性能提升44.15%;在2号土样中仿生犁体相对传统犁体减阻7.8%,土壤减粘性能提升45.49%,研究结果表明仿生犁体对棉田土壤减粘降阻效果明显。 相似文献
7.
针对翻转犁能耗高、易黏附、易遭冲击破坏等问题,研制了高速智能液压翻转犁,优化了整机结构与配置参数。以穿山甲体表的鳞片三角圆弧状结构和蜣螂体表的凸包结构相结合作为仿生原型设计了仿生犁体,并设计了双向犁耕装备的过载保护自动避障机构,平衡状态下对应所需弹簧预紧力9.75 kN,取安全系数1.3,设置初始状态预紧力12.67 kN。建立了犁体耕作过程离散元仿真模型。仿生减黏犁体相对传统犁体土壤减黏性能提升44.15%,减阻7.8%。耕深稳定性变异系数2.86%,土垡破碎率97.1%。研究结果可为高速智能液压翻转犁设计及改进提供参考。 相似文献
8.
针对翻转犁能耗高、易粘附、易遭冲击破坏等问题,研制了一种高速智能液压翻转犁,优化了整机结构与配置参数。以穿山甲体表的鳞片三角圆弧状结构和蜣螂体表的凸包结构相结合作为仿生原型设计了一种仿生犁体,并设计了一种双向犁耕装备的过载保护自动避障机构,得到平衡状态下对应所需的弹簧预紧力为9.75KN,取安全系数为1.3,设置初始状态预紧力为12.67KN。建立了犁体耕作过程离散元仿真模型。仿生减粘犁体相对传统犁体土壤减粘性能提升44.15%,减阻7.8%。耕深稳定性变异系数2.86%,土垡破碎率97.1%。研究结果可为高速智能液压翻转犁设计及改进提供参考。 相似文献
9.
为研究离心泵叶片上仿生非光滑减阻效果与仿生非光滑结构布置位置的关系及离心泵水力效率对仿生结构布置位置的敏感程度,将仿生非光滑结构分别均匀布置于离心泵叶片的6种不同位置上.利用ANSYS软件进行数值模拟,研究了目标流量下6种方案离心泵的性能参数及叶轮内部流动情况,将根据数值计算结果得到的仿生非光滑结构的最佳布置方案与常见布置方案在全流量下进行对比分析,并在应用相同仿生非光滑结构布置方式的前提下,分析了粗糙度的影响.结果表明:该离心泵模型在目标流量下,应用仿生叶片后,其水力效率变化有限,而叶片壁面上平均剪应力相较于光滑壁面情况下降最大约12.7%;布置于任意位置的仿生非光滑单元均能在一定范围内产生减阻效果,相邻仿生单元对于同一壁面位置的减阻效果不具有线性叠加关系;在全流量下,将仿生非光滑结构布置于叶片背面的中部,相比于将其布置于叶片背面的出口部分,增效率与减阻率均更为优秀,且2种方案的增效率与减阻率随流量变化的趋势较为相近;粗糙表面尽管能和仿生结构表面一样在近壁面形成低速层,但无法实现减阻效果.该研究表明,仿生结构对离心泵水力效率的影响与模型本身有关,在使用一定个数的仿生凹坑单元的前提下,应尽量将凹坑布置在剪应力大处. 相似文献
10.
11.
12.
13.
14.
15.
《Journal of Agricultural Engineering Research》1998,69(3):249-254
A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian and European, containing large amount of lycopene and β-carotene, respectively, were tested. The dried powder was stored under an atmosphere with O2and at three different temperatures, 5,20 and 35°C. The surface colour of the powder was monitored during storage by a Hunter colour ratioa/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of concentration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were calculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouration took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour ratioa/bof dried powder at 25°C showed good agreement with the experimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of carrot. The use of the induction period in the manner described may enable the shelf life of dried powder to be predicted. 相似文献
16.
17.
18.
The fractional outflow rate of water from the rumen, measured as the rate of disappearance of the chromium complex of ethylenediamine tetra-acetic acid, was related to a number of dietary factors. A multiple regression equation was derived which expressed fractional outflow rate as a function of the intakes of dry matter, ash, acid-detergent fibre and crude protein.The data analysed consisted of 243 observations for sheep on 59 diets, including forage, concentrate and mixed diets. The ranges covered by the data were: fractional outflow rate 0.7–3.6 day?1; dry matter intake 560–1400g/day; ash 4–30%, acid-detergent fibre 7–41%, crude protein 5–26 % of dry matter; there were no observations for sheep of less than 34 kg liveweight.The equation accounted for 56·3 % of the total variance. Between-sheep variance could not be calculated for the whole of the data but was undoubtedly substantial since, for a sixth of the data, it was known to account for 38 % of the total variance. 相似文献
19.
感官检验棉花的品级,这是农村常见的一种检测手段.它的一个主要特点就是存在不确定性.这是由于检验员的品级检验水平存在一定的差异,其中有很多因素制约着检验的结果.文章对影响感官检验结果的因素进行了系统的分析. 相似文献
20.
从灾害经济学的角度探讨了城镇供水优化调度的必要性和可能性,认为在缺水不可避免的情况下,对供水进行优化调度可以减小缺水带来的损失,产生较好的减灾效益,特别是可以大大减小严重干旱的灾害效应。并根据水资源的特性,提出了缺水损失的计算模式以及优化调度的原则和方法。 相似文献