【Application of water pressure lifting system in fountain landscape】
Author：小編Update Time：2025-01-20
1、 Introduction
In water landscape engineering, fountain landscape is indispensable. Whether big or small, I always hope to have fountain elements as embellishments or main scenery. The nozzles of the fountain are almost all exposed above the water surface, which is very detrimental to the scenery. People hope that when the fountain is not spraying, the nozzle will not protrude from the water surface.
The current common solution is to use a dual-purpose water and drought tank. Install the fountain equipment in a dry spray form inside, leaving holes for nozzles, lights, etc. Design a shallow water tank on top of the dry pond roof, with a depth of about 200-300 millimeters. When using a fountain, water is pumped into another dedicated pool, which can be called a regulating pool. Expose the nozzle above the water surface, and the fountain can be used. After the fountain performance, use a pump to refill the water from the reservoir into the fountain pool. If the scale of the fountain is large, the capacity of the reservoir needs to be large. Taking the fountain in the North Square of Xi'an Big Wild Goose Pagoda as an example, the volume of the regulating pool should be as large as 3000 cubic meters. The power of pumps used for rapid discharge and reinjection also needs to be very high, which is a minor drawback.
For fountains in rivers and lakes, if you want to see them, you cannot solve the problem with fast drainage and fast irrigation. It can only be solved by using the nozzle or system lifting method. Of course, in reality, dual-purpose water and drought nozzles can also be lifted and lowered to solve the problem of not being exposed. This can save the need for a water storage tank.
There are various methods to achieve lifting, such as hoisting mechanisms, floating mechanisms, hydraulic mechanisms, etc.
In terms of hydraulic mechanisms, people also prefer hydraulic pressure in reality. Hydraulic technology has become very mature and its application is also very common. However, the application of hydraulic systems in water has its limitations. The oil supply system should be equipped with a dedicated pump room. Hydraulic cylinders are either isolated from water or made of stainless steel material. It is not easy to isolate the oil cylinder from the water in a large fountain system. The oil cylinder is placed in water, and once it leaks oil, it pollutes the landscape water. If the oil pump of the hydraulic system is replaced with clean water, such as tap water. Can't that solve it! Yes, it can be completely solved. Our plan is to use landscape water instead of clean water.
2、 Design of water pressure lifting system
(1) Design and allocate lifting units
(2) Rigid design requirements
(3) Lift calculation
(4) Selection of water pump and hydraulic cylinder
(5) Precautions for guiding institutions
(6) Waterway design of lifting system
1. Design and allocate lifting units
Definition: One or more water forms combined into a whole for lifting and lowering are called a lifting unit.
There are various forms of fountains, some are compact, some are scattered, some main pipelines may overlap with each other, some different water shapes may share the same water pump, some water shapes need to be realized by mechanical motion mechanisms, and some nozzles are realized by one or more pumps, which requires the combination of lifting units according to specific situations.
If 128 two-dimensional CNC nozzles are arranged in a row, they can all be combined together to form a whole system that can lift and lower simultaneously, which is a lifting unit. It can also be done in groups of 64, forming a complete system for simultaneous lifting and lowering, which is two lifting units.
Pay attention to the following four points when determining the lifting unit:
① Prioritize combining the same specifications and shapes of water together
② Prioritize combining water shapes that rise to the same height together
③ Priority is given to combining water shapes that are closer together
④ The weight distribution should be balanced, and the center of gravity of the relative unit should be symmetrical
2. Key points of rigid design
Based on the combination form of the units, preliminarily design their connection methods. The rigidity of each system is a relative concept. The rigidity size is related to the configuration position and spacing of the support points. The same material, the same structural form, the same lifting unit, multiple support points, and close spacing between support points make this unit more rigid than another unit. Different unit structures have different forms, and the rigidity of a unit's structure may not necessarily be less than that of another seemingly robust system. The factors that affect the rigidity are complex. The structural forms of each unit are not exactly the same, and the rigidity verification is not the same pattern. But if necessary, the system should be rigidly checked.
The main factors that affect the rigidity of the system are:
① Structural form. It is advisable to use a truss structure for multiple CNC nozzles arranged in a straight line.
② The physical properties of materials. Such as tensile strength, flexural strength, yield strength, etc.
③ Main pipe diameter size of pipeline system
④ The shape of the piping system, such as circular, linear, etc.
⑤ Weight of system equipment
⑥ The distance between the pivot points. The fulcrum here is the hydraulic cylinder.
According to the specific plan, conduct a detailed analysis. Reasonable combination of lifting units, reasonable configuration of hydraulic cylinders, comprehensive consideration. Reasonably design its connection method and consider how to strengthen the rigidity of the system to make it the simplest and most cost-effective.
For example, a circular fountain can be used as a lifting unit. Several hydraulic cylinders are evenly distributed for support, but the system rigidity is insufficient. At this point, we can continue to consider adding more hydraulic cylinders. You can also consider increasing the diameter of the main pipe. Obviously, increasing the pipe diameter is better than adding more hydraulic cylinders when the costs are comparable. Because bending the pipeline once solves the problem.
It is best to use pipe as the material for the truss, because after the pipe mouth is sealed, the buoyancy generated by its own drainage can balance a part of its own weight. This way, the required lift can be reduced when calculating.
3. Lift calculation
The required lift of the lift system is determined by the following factors:
① The total weight of the system, including all equipment and components that rise and fall with the system. Submersible pumps, nozzles, valves, pipelines, lighting fixtures, cables, etc. should all be included.
② Utilize the lift of the lifting system to drive the force required for certain ancillary facilities. If the lifting system is used to drive the opening force of the movable cover plate.
③ The resistance of water when the system rises
④ Internal resistance within the system. The force weakened by hydraulic cylinders, guiding structures, and installation deviations.
⑤ The force of water fluctuations on system disturbances.
⑥ The recoil force generated by the system when the nozzle sprays water.
① The total weight of the system can be obtained through weighing or calculation.
③ ④ ⑤ are difficult to calculate. Why not increase the total weight of the system by a factor to calculate.
⑥ According to the momentum theorem, it is known that. The impulse of the external force acting on an object is equal to the change in its total momentum. The impulse of an object is equal to the total momentum increment of the object. A simplified formula for calculating recoil force can be derived based on the definitions of momentum and impulse.
Momentum: The product of the mass and velocity of a moving object is called momentum
\
p： Momentum unit: kg · m/s kg · m/s
m: The unit of mass for moving objects is kilograms (kg)
V=velocity unit of moving object: meters/second m/s
Impulse: The product of force and the duration of force action is called the impulse of force.
\
I: Impulse unit: N · S
F: Unit of action: Newton N
t: Time unit of force action: seconds S
According to the momentum theorem
\Namely, (1)
After the fountain scheme is determined, the nozzle diameter D (unit: m) and nozzle water output Q (unit: m 3/s m 3/s) are known, which allows for the calculation of the water spray velocity v and the mass of water output m within a certain period of time.
\Initial speed:\= 0
\Density of Water Unit: 1000 kg/m 3 1000kg/m 3
Enter Formula (1)
Then\
Its conclusion:
The force exerted on the system when the nozzle sprays vertically is the ratio of the square of the nozzle's water flow rate multiplied by the product of water density and the nozzle area.
Unit: Newton kg · m/s 2
The calculation method for recoil provided here is for reference only and differs from the calculation methods provided in some publications, resulting in different conclusions.
4. Selection of water pump and hydraulic cylinder
According to Pascal's theorem, "the pressure applied to a closed liquid can be transmitted from the inside of the liquid in all directions without changing in magnitude.
The power source of lift is to apply pressure to the water inside the hydraulic cylinder by a pump. The force generated by the compression of the piston in the hydraulic cylinder is proportional to the pressure and the compression area of the piston. Therefore, the key to the problem is to choose the head of the pump and the diameter of the hydraulic cylinder reasonably.
After the system is determined, the number of pivot positions can be preliminarily determined. You can calculate the force borne by each cylinder. The head and cylinder diameter of the pump can be selected first. If a pump with a certain head is selected first, the diameter of the hydraulic cylinder can be calculated.
The length of a hydraulic cylinder is mainly determined by the required lifting height. The lifting height of each unit may not be the same. But the lifting height of hydraulic cylinders in the same unit should be the same. Given the diameter and height of the cylinder block, the volume of the cylinder block can be calculated. The total volume can be calculated based on the number of hydraulic cylinders. Once a rise time is determined, the flow rate of the selected pump can be calculated.
Determine the power and quantity of the lift pumps based on the size of the plan and the number of systems.
5. Precautions for guiding mechanisms
A unit generally requires multiple hydraulic cylinders for lifting and lowering. The speed at which the hydraulic cylinder rises is related to the speed of the water allocated to each hydraulic cylinder, as well as the precision of its own processing and installation. It is difficult to ensure the vertical lifting and lowering of a system, to exaggerate, it is a crooked lifting and lowering. If the lifting height of the system is not very high and there are large holes in the nozzle, light, etc., then the crooked lifting or lowering does not affect use, because when it reaches the top, it becomes vertical. If the holes in the nozzle, lamp, etc. are small, the crooked lifting will cause problems, either damaging the equipment or getting stuck on the top plate of the dry spray and unable to lift out. To avoid such problems, it is necessary to set up a guiding mechanism for guidance. As long as the installation accuracy of the guiding mechanism is guaranteed, this type of problem can be solved.
The form of the guiding mechanism varies, and choosing a wheel rail mechanism is better because it is less likely to get stuck.
There are three main factors that affect the guiding mechanism: first, the clearance between the guiding mechanism and the mating pair. The second is the verticality and parallelism of the installation of the guide rail. The third is the rigidity of the guiding mechanism itself. Especially the verticality and parallelism of guide rail installation have a significant impact.
Refer to Figure 1 and Figure 2
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Figure 1 Figure 2
Figure 1 shows the sliding sleeve guide. If a certain guide rail tilts at an angle and the height of the system exceeds the allowable range of the clearance between the guide sleeve and the guide rail, it will get stuck.
Figure 2 shows the combination of guide wheels and rails. Although this situation will not get stuck, the system will tilt as it rises. So the verticality of the guiding mechanism is the key to ensuring the vertical lifting of the system.
6. Water circuit design for lifting system
The waterway design of the lifting system is a key factor affecting the synchronous lifting of hydraulic cylinders.
The key to the design of the waterway system mainly lies in how to ensure that the water supply speed to the hydraulic cylinders of each lifting unit is consistent, so as to ensure that the hydraulic cylinders rise synchronously and the water flow speed from the hydraulic cylinders is consistent during the return descent. Thus, the hydraulic cylinder can descend synchronously to ensure that the system's holy sword does not tilt.
The measures include: 1. Each hydraulic cylinder should be equipped with a water inlet regulating valve to adjust its water inlet speed. 2. The flow velocity inside the pipelines supplying each hydraulic cylinder should not be too high, and it is recommended to be less than 0.1m/s to maintain the same inlet pressure for each cylinder as much as possible. 3. Long arranged systems should supply water to the main pipeline at both ends, preferably using a closed loop for water supply. When the system descends, the pump stops running and descends by gravity of the system. Each cylinder in the return water pipeline system should also be equipped with regulating valves to maintain the same return flow rate as much as possible.
All regulating valves should be easy for manual operation by humans.
The electric valves that open the return pipe during the descent of the feedwater pump should have backups.
The diagram of the lifting pipeline system is as follows:
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The size of the vertical deviation in the installation of hydraulic cylinders is also one of the factors that affect the smoothness of vertical lifting. Excessive deviation not only affects lift but also easily damages equipment.
When installing the system, there should be a manually adjustable balance mechanism, which is also convenient for maintenance. After the system sinks, it can be supported by these pivot points.
3、 Water quality
Now let's answer why landscape water can be boldly used as the power transmission medium for hydraulic cylinders. From the structure of the hydraulic cylinder and the direction of water flow, the water entering the cylinder also includes flocs and suspended solids, which are discharged from the drainage system when the hydraulic cylinder descends. Adding another filtering device in the hydraulic cylinder, which filters when the inlet water rises and backwashs when the outlet water falls, can solve the problem of dirty water quality. In practical applications, there is basically no need to add filters.
This is precisely because of the superiority of using water for hydraulic power transmission. Because even if some suspended particles enter the cylinder, they may scratch the fit between the piston and the cylinder, causing poor sealing of the piston and water leakage, which does not affect the use of the hydraulic cylinder at all. There is no need to consider polluting the environment or replenishing water like oil leakage, because there is water around. The material of the hydraulic cylinder is preferably stainless steel.
Comparison with other methods of lifting and lowering
The most commonly used method is floating lifting. The advantage of floating lifting is that it can change with the water level, but there are also positioning and guidance issues. The disadvantage is that it consumes a large amount of steel, and lifting a system weighing 100kg requires at least 100kg of steel and occupies a large space. The installation project involves a large amount of work and transportation is difficult.
And hydraulic lifting is still superior to floating systems even when the lifting height is not very high.