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在喷灌系统的规划中,确定喷灌强度是一项至关紧要的工作。喷灌强度过大,地面将积水或产生径流,土壤结构亦被破坏,喷灌保土保肥的作用洽成相反;喷灌强度太小,喷水效率就要降低。管道也要加密,投资和运行成本相应都增高,经济上不合算。因此在设计中切不可草率从事。通常,喷灌强度都是用土壤入渗速度来控制。对于土壤入渗速度,一般沿用以筒测法所得之“稳定值”,由于此时水向土中入渗是在水层的压力作用下进行的,也不存在水滴的打击破坏效用,和喷灌条件下的土壤入渗速度相比有明显的差别,因此国内外均对此进行研究,目前有不少研究已具备了实用价值,可供规划设计时参考。另一方面是喷灌强度问题。根据近两年来的了解,国内有不少喷灌系统在计算喷灌强度时是用单喷头公式,或者是用国外现仍沿用的计算公式。计算值常常不符实际,实测喷灌强度不是过大就是甚小。过大的产生了地表径流,甚小的降低了效率,多用了管道,与此同时也限制了喷头的使用范围。因此,本文拟为喷灌强度的计算,提供一个较为符合实际的方法。由于定喷式喷灌系统中,管道式数量最大,且具有代表性,所以叙述就先局限在此范围之内。为了便于阐述和分清概念,把根据设计参数(如布置间距、工作压力、喷头型号、喷咀直径等)计算所得的喷灌强度称为设计喷灌强度,由于喷灌水不可能全部落于地面,多少要有一些损失,实测的平均喷灌强度理应小于(至多接近)设计喷灌强度。所以设计喷灌强度可理解为系统在设计条件下正常运行时所可能产生的最大的平均喷灌强度。
In the sprinkler system planning, to determine the intensity of irrigation is a crucial task. Sprinkler irrigation intensity is too large, the ground will be stagnant water or runoff, soil structure is also destroyed, sprinkler soil conservation and fertilizer to contact the opposite effect; sprinkling intensity is too small, water efficiency will be reduced. Pipeline also be encrypted, investment and operating costs have increased accordingly, economically uneconomical. Therefore, in the design must not be hasty. Generally, sprinkler irrigation intensity is controlled by soil infiltration rate. For soil infiltration rate, the “stable value” obtained by barrel test is generally used. Since infiltration of water into the soil is carried out under the pressure of the water layer at this time, there is no blow damage and destructive effect of water droplet, and sprinkling irrigation Under the conditions of soil infiltration rate compared to a significant difference, so both at home and abroad to study this, there are many studies already have practical value, for planning and design reference. On the other hand is the issue of sprinkling strength. According to the understanding of the past two years, there are many domestic sprinkler irrigation systems in the calculation of sprinkler strength is a single nozzle formula, or is still used abroad is still the formula. Calculated values are often inconsistent with the actual measured sprinkling intensity is not too large is very small. Too large surface runoff, very small to reduce the efficiency, the use of pipes, at the same time also limits the scope of the nozzle. Therefore, this article intends to provide a more realistic method for the calculation of irrigation intensity. As the fixed-jet irrigation system, the largest number of pipe-type, and representative, so the narrative first confined to this range. In order to expatiate and clarify the concept, the sprinkling strength calculated according to the design parameters (such as layout spacing, working pressure, nozzle type, nozzle diameter, etc.) is called the design sprinkling strength. Since the sprinkling water can not all fall on the ground, With some losses, the measured average sprinkling strength should be less than (at least close to) the design sprinkling strength. Therefore, the design sprinkler strength can be understood as the maximum average sprinkling strength that the system may produce when it is operating normally under design conditions.