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661.
662.
对水稻直播存在的农艺技术难点,基于农机与农艺相结合的理念,提出了同步开沟起垄水稻精量穴直播技术、同步开沟起垄施肥水稻精量穴直播技术和同步开沟起垄喷施水稻精量穴直播技术,研制成功2BD系列水稻精量穴直播机.生产试验结果表明,采用精量穴直播技术的水稻群体结构合理,减少了直播稻的倒伏现象,实现了水稻节水灌溉种植,产量可比人工撒播、人工抛秧和人工插秧分别增加10%、8%和6%以上;采用同步开沟起垄施肥水稻精量穴直播技术可节肥30%以上,产量提高10%以上;采用同步开沟起垄喷施水稻精量穴直播技术在直播时同步喷施液体地膜成苗率可提高18%以上,产量提高5%以上. 相似文献
663.
为改善极端条件下航空煤油的点火和燃烧性能,提高煤油活性,本文在大气压氮气环境下利用纳秒脉冲电源产生的滑动弧等离子体进行煤油裂解实验研究,得到了包含活性更高的气态轻质烃和氢气等小分子物质的裂解气。通过改变电源输出脉冲电压的上升沿时间和下降沿时间,得到了裂解气产量、碳氢比以及裂解气中各组分选择性的变化规律,并总结了相关的部分反应路径。实验结果如下:裂解气产量随着上升沿时间的增加而减小,随着下降沿时间的增加而上升,裂解气碳氢比则呈现相反的变化规律;裂解气主要组分中,乙烷选择性最高,在各实验工况下均超过30%;随着上升沿时间和下降沿时间的增加,裂解气中丙烷和丙烯的选择性均降低,氢气的选择性上升;上升沿时间和下降沿时间的变化对裂解效果产生影响的主要原因是改变了反应的路径。实验结果表明,纳秒脉冲滑动弧放电等离子体可以将煤油中的部分大分子烃类转化为气态轻烃和氢气等高活性组分。同时,增加纳秒脉冲电压下降沿时间能够改善滑动弧等离子体的裂解效果,获得更多活性更高的小分子物质。 相似文献
664.
665.
为了研究基于滑动弧的燃烧室头部强化燃烧效果,探究了燃烧室头部的点火过程以及不同等离子体电源输入功率下的点/熄火边界,利用像增强系统获得了CH*基团的分布云图。实验结果表明:输入功率的增大使得燃烧室的点/熄火边界均得到拓展,与160 W工况相比,输入功率为320 W时,点火边界平均拓宽约17.6%,与未放电相比,输入功率为320 W时,熄火边界平均拓宽约45.3%,滑动弧放电对熄火边界拓宽效果明显;当滑动弧能够点燃来流新鲜混合气时,输入功率的增加使得CH*基团分布向上游移动,当输入功率为320 W时,燃烧火焰驻留在燃烧室头部,当滑动弧激励器仅具有助燃作用时,输入功率的增加使得局部CH*基团辐射强度增强,热释放速率增加。 相似文献
666.
等离子体磁壳制动技术是一种新型的行星探测器制动手段,具有制动阻力可调、可靠性高、结构质量小等优势,具有潜在的应用前景。开展了等离子体磁壳制动产生方式与工作机理的数值仿真研究。首先,以火星探测器的制动为背景,将等离子体磁壳简化为圆柱构型,建立了等离子体磁壳宏观模型,得到了制动阻力、有效捕获面积和探测器速度随轨道高度的变化关系。随后以等离子体磁壳中离子、电子和次中性粒子之间的相互作用为研究对象,建立了等离子体磁壳微观模型,获得了等离子体粒子数密度和温度随时间变化的规律。微观模型与宏观模型计算出的制动阻力一致,验证了两种模型的有效性。 相似文献
667.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(3):1711-1720
The active spacecraft potential control (ASPOC) system developed in the 1990s emits positive ions to neutralise the spacecraft potential, such as used in several missions like Geotail, Equator-S, Cluster, Doublestar and MMS. With the experience gained, the next generation of the active spacecraft potential control (ASPOC-NG) instrument has been developed over the last three years. Thereby, three emission technologies were tested including Liquid Metal Ion Source (LMIS), Liquid Metal Electron Source (LMES) and Solid Metal Electron Source (SMES). The development of the emitter module by FOTEC and the corresponding electronics control unit by IWF is presented. Optimisations were carried out with the focus on the reduction of mass and power consumption to comply with the requirements of future scientific missions. Coupling tests of the modules and the electronics control unit were performed including range, accuracy and lifetime tests. Both ASPOC-NG instruments for positive and negative charge compensation and their performance values show excellent results. 相似文献
668.
《中国航空学报》2023,36(5):223-238
CubeSats have attracted more research interest recently due to their lower cost and shorter production time. A promising technology for CubeSat application is atmosphere-breathing electric propulsion, which can capture the atmospheric particles as propulsion propellant to maintain long-term mission at very low Earth orbit. This paper designs an atmosphere-breathing electric propulsion system for a 3 U CubeSat, which consists of an intake device and an electric thruster based on the inductively coupled plasma. The capture performance of intake device is optimized considering both particles capture efficiency and compression ratio. The plasma source is also analyzed by experiment and simulation. Then, the thrust performance is also estimated when taking into account the intake performance. The results show that it is feasible to use atmosphere-breathing electric propulsion technology for CubeSats to compensate for aerodynamic drag at lower Earth orbit. 相似文献
669.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(4):1962-1983
The low solar atmosphere is composed of mostly neutral particles, but the importance of the magnetic field for understanding observed dynamics means that interactions between charged and neutral particles play a very important role in controlling the macroscopic fluid motions. As the exchange of momentum between fluids, essential for the neutral fluid to effectively feel the Lorentz force, is through collisional interactions, the relative timescale of these interactions to the dynamic timescale determines whether a single-fluid model or, when the dynamic frequency is higher, the more detailed two-fluid model is the more appropriate. However, as many MHD phenomena fundamentally contain multi-time-scale processes, even large-scale, long-timescale motions can have an important physical contribution from two-fluid processes. In this review we will focus on two-fluid models, looking in detail at two areas where the multi-time-scale nature of the solar atmosphere means that two-fluid physics can easily develop: shock-waves and instabilities. We then connect these ideas to observations attempting to diagnose two-fluid behaviour in the solar atmosphere, suggesting some ways forward to bring observations and simulations closer together. 相似文献
670.