水利類英文文獻(xiàn)譯文(共20頁(yè))

1、精選優(yōu)質(zhì)文檔-傾情為你奉上Hand Move Irrigation SystemsSummary The hand move irrigation system is a very simple pipe set which can be moved by hand. Two main factorspositioning and moving scheme of the equipment both affect the work time. Here we develop a model to complete the irrigation of the whole field by th

2、e shortest time.Firstly, we decide the certain number of sprinklers through the designated parameter. Using enumerative geometry, we compare the irrigation area of the system with different number of sprinklers and work out the optimum number of sprinklers.Secondly, we take the advantage of combinat

3、orial geometry to decide the positioning and moving scheme of the irrigation system, in order that the model can be used to realize the irrigation task by the shortest work time. In the end we also introduce a new sprinkler with square area and compare its working efficiency with the traditional spr

4、inkler if we use it on this field. 1. IntroductionThere are a wide variety of techniques available for irrigating a field. One of the systems is the "hand move" irrigation system which is used on smaller ranches. Lightweight aluminum pipes with sprinkler heads are put across fields, and th

5、ey are moved by hand at periodic intervals to insure that the whole field receives an adequate amount of water. Given that this type of irrigation system is to be used, how can it be configured to minimize the amount of time required to irrigate a field that is 80 meters by 30 meters? For this task

6、we are going to find an algorithm to determine how to irrigate the rectangular field that minimizes the amount of time required by a rancher to maintain the irrigation system. One pipe set is used in the field. We will determine the number of sprinklers and the spacing between sprinklers, and we wil

7、l find a schedule to move the pipes, including where to move them. A pipe set consists of a number of pipes that can be connected together in a straight line. Each pipe has a 10 cm inner diameter with rotating spray nozzles that have a 0.6cm inner diameter. When put together the resulting pipe is 20

8、 meters long. At the water source, the pressure is 420 Kilo-Pascal, and has a flow rate of 150 liters per minute. No part of the field should receive more than 0.75 cm per hour of water, and each part of the field should receive at least 2 centimeters of water every 4 days. The total amount of water

9、 should be applied as uniformly as possible. 2. Analysis of the problemOur object is to decide the number of sprinklers and the spacing between them. And then we have to set a moving scheme to get an optimal method so that the work time is shortest and the whole field can be irrigated uniformly. The

10、 combination of irrigation system is a complicated problem. The irrigation can be affected by many natural factors. If we dont omit these factors, the model may be too difficult to be applied in practice. Whats more, we have to choose one type of rotating spray sprinkler. After simplication, we star

11、t to construct our model. Firstly, we can analyze the data in the literature and set some limitations of flow rate and water pressure at the nozzles, which are related to the number and spacing. There are also limitations to spray intensity in the known condition. Through the above limitations, we c

12、an work out the number of sprinklers.Then the spacing and moving mode can be decided through calculating the work time. Work time include irrigation time and moving time. Irrigation time is related to the spray intensity and the shape of spray area after overlapped. The moving time is related to mov

13、ing mode. If we make the moving time shortest, there must be only one scheme. We can divide the whole field to several parts. Each part can be covered by one moving unit. This unit is the spray area of irrigation system. We try to choose different spacing and moving mode to cover these parts as much

14、 as possible. If the overlapped area is very small, the whole field can be irrigated uniformly. If the area is very large, these areas can supplement to each other. We may also get a high uniformity of irrigation. After deciding the model, we have to use some evaluation method to analysis whether ou

15、r model is reasonable. One of the most important indexes is uniformity coefficient. Of course, this index can show the rationality of the model. But if this coefficient satisfies the demand of real practice, we can draw a conclusion that we can use our model to solve the problem.3. Assumptions1.Take

16、 no consideration to the reduction of the hydraulic pressure. 2.All nozzles have the same flow rate.3.The water pump can be put anywhere around or in the field.4. Each part of the equipment can be carried by one rancher and the weight of each part doesnt impact on the walking pace.5.Neglect the impa

17、ct of the wind to spray irrigation.6.The spray sprinkler rotates along the circle so the spray area is circular.7.The spray intensity at the spray area is consistent.8.The field is level basin.9.The rotate speed of sprinkler is consistent. 4. Symbols SymbolUnitDefinitionRmThe spray rangeQm3/hThe flo

18、w ratescm/hThe spray intensitydmThe diameter of the nozzlesn/The number of the sprinklers/The coefficient of flow ratethThe work timeCU/Uniformity Coefficientd/Atomization index 5. Maths Model 5.1 Single sprinkler Rotating spray nozzle generally has two spraying ways: rotundity and sector. Here we c

19、onsider the most usual wayrotundity, which means the sprinklers spray area is a rotundity. And each sprinkler has only one nozzle. Under this condition, the spray area of each sprinkler is: As to single sprinkler, its flow rate is Qs, so the spray intensity (cm/h), i.e. precipitation depth per hour,

20、 is: 5-1-1The relationship between flow rate and pressure of the sprinkler is: 5-1-2Qs is the flow rate at one sprinkler.H is the water height converted by water pressure. The range of the sprinkler is an important parameter. It should be calculated in process of irrigation system design. So far, th

21、ere are many experience formulas which can be used in different situations. The Cavazza formula is a more universal formula, so it is used here: 5-1-3In general, the angle of elevation range is from 30 °to 32 °and the data is obtained not considering the influence of wind. Usually the rang

22、e is defined as the longest distance that water can be sprayed in a certain direction. 5.2 The number of sprinklers The number of sprinklers can be decided by setting some limitations so that we can choose an integer number finally as the optimal choice. 5-2-1 5-2-2Hs is the water height converted f

23、rom pressure at the sprinkler.H is the water height converted from work pressure.Qs is the flow rate at the sprinkler. Its value has to be in certain interval a, b so that it can work normally at the certain flow rate. In actual hand-move irrigation system, its rare to use single sprinkler. In order

24、 to raise the efficiency of sprinkler irrigation, several sprinklers are often used together. According to flow rate balance theory, the flow rate of each sprinkler can be calculated: 5-2-3Q： The flow rate of water source (m3/h)Qs：The flow rate of each sprinkler (m3/h)It should be pointed out that t

25、he above formula can be only applied when sprinklers are distributed uniformly along the pipe and the pressure loss in the direction of flow is so small that it can be ignored.5.3 Combination form of the sprinklersAs to single pipe, sprinklers can only be distributed along a straight line, which can

26、 be simplified as the combination of several points at a straight line. But in fact, pipes can be moved by ranchers, so the pipe can irrigate different areas and realize dynamic and periodic irrigation.The combination form of sprinklers can also be named as arrangement form, i.e. the arrangement of

27、relative position of sprinklers. When the range of each nozzle is the same, the interval between sprinklers isnt uniform in different arrangement form. But when we choose the number of sprinklers we have to follow the principle that all parts of the filed can be irrigated and sprayed uniform.5.4 Wor

28、k time Work time consists of two parts: spray irrigation time and equipment movement time. u Spray irrigation time t1 Spray irrigation time t1 means the spray time needed in these spray positions in order to realize precipitation quota. It can be calculated as follows: (min) 5-4-1n1i: Spray times of

29、 spray position i.t1i: Settle time of the equipment in position i.Another factor we should consider is that the precipitation of each part of the field cant exceed 0.75cm per hour. Thats to say if the spray strength of single sprinkler is larger than 0.75cm/h, the remaining time at this place is （0.

30、75/s）hours at most. Under this condition, the irrigation quota can be reached only by periodic irrigation. If the spray areas of sprinklers overlapped when the pipe set is fixed, the remaining time will be halved even much shorter, which will lead to the increase of equipment moving frequency. Accor

31、ding to the discussion above, t1i is determined by S4, because in this region the spray intensity is greater than 0.75cm/h. Therefore, the settle time of positions is determined by it: It is assumed that m is the stated precipitation of each period (a period is 4 days), and it should over 2cm of eve

32、ry 4 days (2cm). n1i is determined by the region with low spray intensity and m. u Equipment movement time t2 The time needed for moving the equipment depends on the distance between the former place and the latter one, the velocity of disassemble and fix of the pipe set and the number of the sets.

33、Because the area of the filed is small and equipments are not many and the time of moving is less than irrigation time, in a perfect design, the equipment should be moved as less as possible. In accordance with former factors, we can say that the better irrigation can be reached if the range is long

34、er and the spray intensity is weaker.Given that there are j ways of moving the equipment and the corresponding time is: 5-4-2: the distance the rancher need to walk when moving the equipment in the j way;So the whole time of moving the equipment is: 5-4-3nj: the times of moving the equipment by the

35、means of j in one cycle. The work time is the plus of the irrigation time and the time of moving the equipment: 5-4-4 The target of our model is to make as shorter as better under the condition that every part of the field reach the precipitation. 6. Solution 6.1 The number of sprinklers The number

36、of the sprinklers and the spacing between them are the most important to decide the irrigation system. Because the above parameters, work pressure, spray range and flow rate are interactional and restricted by each other. We get some data from literature about the parameters of the sprinkler. They a

37、re listed in the table below. Table 6-1-1TypeWork Pressure (KPa)Flow rate(m3/h)Spray range(m)PY1203002.3619.0PY2152502.0216.53002.2217.54002.5618.5PY2203502.4018.54502.7219.5 u The restricted condition of flow rate Based on the data above, we can see that all the flow rates are between 2 to 3. If th

38、e flow rate doesnt satisfy this condition, it will bring negative effect on the irrigation. It is direct factor related to the yield of product.The flow rate of water source is Q, Q=9m3/h. Because the flow rate in the water source equals the summation of flow rate at each nozzles. Due to formula 5-2

39、-3, we know that:Accordingly, the number of the nozzles should be 3 to 4.5. As ns is integer, we can only choose n=3 and n=4. u The restricted condition of work pressure The water pressure of the headstream is 420KPa. Because we didnt take the reduction of water pressure along the pipe into account,

40、 so we consider the work pressure equals the water pressure of the headstream. Thus, we can calculate according to formula 5-1-2 and 5-2-1.So now we can decide the number of sprinklers finally. The number is 4. 6.2 Confirmation of equipments position From the above analysis we decide to use 4 sprink

41、lers, and the sprinklers are distributed uniformly along a pipe of 20 meters, which can be simplified as the combination of several points at a straight line.When the pipe set works, the irrigation area of all the sprinklers form a combination area as follow which can be divided into four areas alon

42、g the pipe, we named them as S1, S2, S3 and S4. We can find they are bilateral symmetry. Figure 6-2-1 Irrigation model of 4 sprinklersSpray intensity of each area can be worked out: = 0.2128cm/h = 0.4256cm/h = 0.6384cm/h = 0.8512cm/h (0.75cm/h) As the shape of the field is rectangle, according to co

43、mbination model that 4 single-nozzle sprinklers distribute along a 20 meters long pipe, we can realize that the spray region of this irrigation system can be divided into 4 parts. In these 4 parts the difference of spray intensity between the region S1 and S4 is the largest. In order to increase spr

44、ay efficiency and spray uniformity, we must make the difference of spray intensity among different region as small as possible so that we can reduce the times of equipment movement and of the repetition spray, consequently reduce the total work time. Our model divided the whole field as follows: (Fi

45、gure 6-2-2) Figure 6-2-2In the above figure the bigger rectangle denote the whole field, and it is divided into 4 parts with the same area. Spray equipment can be set up in six positions. Asterisk denotes the position of O dot which is denoted in figure 6-2-1. It can be seen that these six positions

46、 is symmetric. As to the small region of 4 corners, it can only be irrigated via 1 and 6 spray position, therefore the repetition times of these two spray positions is determined by the spray intensity of the 4 corners. As to other 4 kinds regions, we need to consider firstly that parts of these 4 k

47、inds regions has been irrigated when it is irrigating in 1 and 6 spray position. So the repetition times of 2, 3, 4 and 5 spray position is less. The process of analysis is as follows (considering symmetry, we need only to analyze half of the field): Figure 6-2-2 Spray model of position 1As the spra

48、y time of each position is determined by S4 (so in order to simplify calculating process we take it as 52.8 min). So in order to realize precipitation of S3 in 4 days no less than 2cm, in spray position 1 the field needs to spray 4 times, and precipitation quota of the region S2 which is left in the

49、 first rectangle can be realized by the spray of position 2 and 3. Simultaneously, the region S3 and S4 in the second rectangle can also be sprayed. When the equipment is moved to the position 2, the spray condition is similar as position 1.As to spray position 2 and 3, assuming that the repetition

50、times of spray position 2 and 3 is x and y respectively. To realize the precipitation quota, it must meet: 3x+2y8 and 3x+y4.In principle, the spray irrigation in position 2 also has leave-out parts in the second rectangle and overlay parts in the third rectangle. The leave-out parts will determine x

51、 and y. Figure 6-2-4 Spray model of position 3 and 4 Apparently, the middle four spray position can influence each other. Considering symmetry factor, the spray times of position 3 and 4 is the same. And according to that the shaded part should also reach precipitation quota, it can be gotx+5y12. So

52、lving the above inequality we can know the minimal value of x+y. So the value of x and y is: x=y=2 or x=1, y=3Therefore we can get two projects of spray position and spray times according to the above model. Project I: the spray times of position 1 and 6 is 4 times respectively; the spray times of p

53、osition 2 ,3,4 and 5 is 2 times respectively.Project II: the spray times of position 1 and 6 is 4 times respectively; the spray times of position 2 and 5 is 1 times respectively; the spray times of position 3 and 4 is 3 times respectively. 6.3 Determine of movement scheme Through the analysis of 6.2

54、s project, it can be known that although both projects can achieve the spray irrigation task, the spray uniformity degree of project I is higher than that of project II. So in this problem we choose project I. Moreover to achieve that the precipitation of each part can not be over 0.75cm/h, the seri

55、al number difference between two consecutive regions is no less 3. A spray period is 4 days, the precipitation quota is 2cm, if the workload is uniform each day, and the movement style of the equipment is as follows:The first day: 1415 Figure 6-3-1The second day: 5263 Figure 6-3-2The third day: 3614 Figure 6-3-3The fourth day: 6261 Figure 6-3-4 6.4 Calculation of work time Recently the standard length of lightweight aluminum pipe is 2m, 4m, 5m, 6m. To simplify the process, here we use pipes of the same type. Considering the less the number of equipment is, the less the time of