Development and experimental study of a kind of fluidic sprinkler

In this paper, a new variety of fluidic sprinkler was introduced and its working principle was presented. An auto-testing system of water distribution was established. The technology using rain-collection as an implement used RS485 assembly line for installation. Angle and frequency of step-by-step are effective driving moment operation of the fluidic sprinkler. The water distribution of fluidic sprinkler types 10 to 50 under relevant operating pressures was pointed out. Experimental results demonstrated that the fluidic sprinklers have complied with the national standards in flow, uniform coefficient, range and so on, which was supposed to be substitute samples for impact sprinkler in the future.


Introduction
The crisis caused by water scarcity will intensify further in the 21st century.Some researchers have shown that water-use efficiency is an important tool in improving agriculture in irrigated areas.Sprinkler irrigation has become the main method of saving water in many countries.It was allowed to irrigate many types of soils, geographies and crops.It can be one of the most efficient and uniform methods if the system is well designed and managed.Sprinkler irrigation not only reduces water source requirements and increases crop yield, but also improves crop quality and decreases the possibility of soil erosion [14].
In 1954, China recommended the use of water saving equipment from Russia.Since then, irrigation equipment has developed slowly.One of the main causes is the instability of the sprinklers.The impact sprinkler PY was developed by the Zhenjiang Agriculture Institute in 1977.In 1980, the self-controlled step-by-step kind of fluidic sprinkler typed PS was first developed.Fuzhou University developed an entirely different type of fluidic sprinkler which was self-controlled by feedback in 1981.Nanjing recommended the use of the Austrian production line and manufactured the ZY-1 ZY-2 sprinkler in 1984.In the decades that followed, irrigation equipment developed slowly [3].The double strike synchronism kind of fluidic sprinkler invented by Hang et al. and sold as a product was not successful in the market for some technical reasons.In 2005 Jiangsu University first invented the PXH, which is the gap-controlled kind of fluidic sprinkler [13].Sprinklers are important devices in the irrigated system [4][5][6][7][8][9].The objective of this article is to develop a new variety of fluidic sprinkler that utilized the Coanda effect, and its hydraulic characteristics are defined by experiments [1]. Figure 1 shows photos of this kind of fluidic sprinkle.The working principle of the fluidic sprinkler is chiefly dependent on the Coanda effect, as shown in the simplified diagram of the wall to which the offset jet is attached [2].Because of the small space on the right side of the jet, it is harder to fill it up than on the left, and the air on the right side is thinner than on the left, so the pressure on the right decreases when the jet is ejected from the nozzle.The jet is compelled to bend towards the boundary and eventually attaches it.After reattaching to the wall, the jet develops in the wall jet region.This is called the "Coanda effect".The fluidic sprinkler used the Coanda effect to form a water flow reaction force to push the sprinkler to rotate.The knowledge about the design of kind of fluidic sprinkler is quite limited.Three static conditions of simple inner flow have happened.First, the primary flow jet is straight and the sprinkler is idle.The air moves with the streamline in areas I and II.So the pressure in the recirculation region is lower than atmospheric.Some air will flow into the left recirculation region from the signal.Some air is filled from gap C into the right recirculation area.Then the pressures in area I and area II are equal, PL=PR.So the primary flow jet is straight and the sprinkler is idle.In the meantime signal flow which is collected in area I will drift to area II to fill up gap C. When the signal jet flow blocks gap C, no air comes into area II.So the pressure on the right is much less than the pressure on the left, PL>PR.The primary flow jet bends towards the boundary and ends up adhering to it as PL-PR become a certain value.Secondly, When the jet is reattached to the plate wall, the signal pipe could not get any flow.As the water is drawn out of the signal pipe, the negative pressure in areas I and II is gone.The area I and area II are connected and PL=PR.The primary flow jet returns to straight and the sprinkler becomes idle again.This phenomenon This phenomenon occurs repeatedly and the fluidic sprinkler is rotated step-by-step.Lastly, when signal 3 is blocked, no air goes into the area I. Area II is filled with air by gap C and PR > PL.The primary flow jet is reattached to the left plain and the sprinkler spin in the opposed reverse.Figure 3 shows the working principle of sprinkler.

Experimental study
Experiments were conducted indoors to ensure the radial distribution of water.It also prevent drift and loss.The measurements were carried out at Jiangsu University's Indoor Sprinkling Laboratory.This is a circular indoor laboratory 44 meters in diameter.The influence of wind and other natural factors were eliminated so that the test results were accurate and reliable.The distribution of water is an significant index to measure the characteristics of sprinkler, and is also the main basis for irrigation arrangement and design [10,12].Experiments were conducted in accordance with the national standards of sprinkler irrigation.The elements of water distribution include point irrigation intensity, flow, and the range of associated pressures [11,15].The point irrigation intensity test is the key point and the hardest point in the entire testing system.If all the points were tested manually, the test would be inefficient and the reliability of data would not have be as reliable.Therefore, the development of an automatic testing system was the important assurance to the development of the new type of sprinkler.Jiangsu University built a new testing system, which has changed from the centralized system to the full line distribution system based on RS485.The technique of using rain-collection was installed in the lab as a tool, and the RS485 assembly line was used was used for the control room computer connection.It greatly reduces the length of the cable and the workload of the connection, making the system more reliable and compact.
The flow sprayed from the sprinkler was set by the auto-selection system of the self-developed software.The diameter of the collector was 20cm and the height was 60cm.The collectors were spaced 1 m apart from one another, with a total of 40 points.The accuracy of measuring the flow rate of irrigated area with the flow-computer is +_ 0.5% in the whole flow rate range.Because of the confined space of the area, we could only check one sprinkler's hydraulic characteristics.Figure 4 shows the condition of sprinkler testing in the laboratory.It should be noted from Table 1 how we designed the experimental schemes.
Figure 5 showed the water distributions of fluidic sprinkler types 10, 15, and 20, Figure 6 showed water distributions from types 30, 40, and 50.As can be seen from the results, the fluidic sprinklers have complied with the national standards in flow, uniform coefficient, range and so on.

Conclusion
In this paper, a new variety of fluidic sprinkler was introduced and its working principle was presented.Extensive and systemic research on the wall-attachment jet was accomplished using theoretical study.The testing system for the sprinkler rainfall distribution was rebuilt.The auto-testing system for water distribution was established.The hydraulic characteristics of the sprinkler were tested thoroughly and precisely.The experimental results demonstrated that the angle and the frequency of the fluidic sprinkler were mainly dependent on pipe length.The longer the pipe, the bigger the angle and the lower the frequency.In a word, the fluidic sprinkler prototype operated properly and reliably.It can change the range and atomization of the fluidic sprinkler by adjusting the length of the pipe, and become a multi-function sprinkler, which is just fit for the trend of multi-function and energy-saving.Although there are still some problems in the process of industrialization, such as the roughness in the flow channel is not up to the requirement, and the research on the fluidic sprinkler is not enough in the experiment, through the use of computer simulation, the process is improved, industrial products are expected to achieve the goal of good and reliable operation.The fluidic sprinkler is expected to replace the impact sprinkler in the future.

Figure 1 .
Figure 1.A new kind of fluidic sprinkler.The working principle of the fluidic sprinkler is chiefly dependent on the Coanda effect, as shown in the simplified diagram of the wall to which the offset jet is attached[2].Because of the small space on the right side of the jet, it is harder to fill it up than on the left, and the air on the right side is thinner than on the left, so the pressure on the right decreases when the jet is ejected from the nozzle.The jet is compelled to bend towards the boundary and eventually attaches it.After reattaching to the wall, the jet develops in the wall jet region.This is called the "Coanda effect".The fluidic sprinkler used the Coanda effect to form a water flow reaction force to push the sprinkler to rotate.

Figure 2 .
Figure 2. The schematic diagram of the wall attaching the offset jet in.The knowledge about the design of kind of fluidic sprinkler is quite limited.Three static conditions of simple inner flow have happened.First, the primary flow jet is straight and the sprinkler is idle.The air moves with the streamline in areas I and II.So the pressure in the recirculation region is lower than

Figure 3 .
Working principle of sprinkler.