As the core component of hydraulic control system, servo valve is widely used in aerospace, industrial automation, robotics and other fields. Its performance directly affects the response speed, control accuracy and energy efficiency of the system. In the practical application of servo valve, pressure loss is an important parameter that can’t be ignored, which not only affects the efficiency of the system, but also may lead to problems such as fever and decreased control accuracy. Therefore, it is of great significance to accurately calculate the pressure loss of servo valve for system design and optimization.
I. Working principle and pressure loss type of servo valve
The servo valve controls the pressure and flow of hydraulic oil by receiving the electric signal instruction, so as to drive the actuator to complete the precise action. In this process, hydraulic oil will produce pressure loss when it passes through the servo valve due to factors such as throttle, flow friction and local disturbance.
Pressure loss in servo valve mainly includes the following three categories:
1. Pressure loss along the way: the energy loss caused by viscous friction when the oil flows in the channel in the valve is usually related to the viscosity, flow rate, pipeline length and diameter of the oil.
2. Local pressure loss: It occurs at the position of valve opening change, sudden expansion or contraction of flow passage, bend, etc., which causes eddy current and disturbance due to the change of flow direction and speed, resulting in energy loss.
3. Throttle pressure loss: The main control mode of the servo valve is to adjust the flow or pressure through throttling. When the valve port is partially open, there will be a significant pressure difference before and after the valve port, which is the throttle pressure loss.
Second, the calculation method of servo valve pressure loss
# 1. Basic formula method
Throttle pressure loss is usually estimated by throttle formula:
$$
Delta p = frac{Q^2}{K^2 cdot A_e^2}
$$
Among them:
-$Delta p$: pressure loss (Pa)
-$Q$: the flow through the valve port (m/s)
-$A_e$: effective throttling area (m)
-$K$: Flow coefficient, which is related to oil density and valve port structure, is usually determined by experiments.
# 2. Empirical formula or manufacturer data
In practical engineering, many servo valve manufacturers will provide the pressure-flow characteristic curve of the valve or give the pressure drop data at a specific flow rate. Designers can estimate the pressure loss directly from these data, avoiding complicated theoretical calculation.
# 3. CFD simulation analysis
With the development of computer technology, using Computational Fluid Dynamics, CFD) to simulate and analyze the internal flow field of servo valve can more accurately predict the pressure loss distribution of each part. This method is suitable for complex structures or occasions with high precision requirements, but the calculation cost is high.
Third, the factors affecting the pressure loss
1. Opening of valve port: The smaller the valve port, the stronger the throttling effect and the greater the pressure loss.
2. Working flow: The greater the flow, the higher the flow speed and the greater the pressure loss.
3. Oil viscosity: The higher the viscosity, the greater the resistance along the way and the higher the pressure loss.
4. Structure design of valve body: Reasonable flow passage design can reduce local pressure loss and improve valve efficiency.
Fourth, design and optimization suggestions to reduce pressure loss
-Optimizing the valve port structure: adopting multi-stage throttling or conical valve core structure can reduce the throttling effect.
-Improve the manufacturing accuracy: reduce the roughness of the inner surface of the valve body and reduce the friction loss.
-Select suitable oil: Using low viscosity and high performance hydraulic oil will help reduce the loss along the way.
-Reasonable selection: select the servo valve with appropriate diameter and flow matching according to the actual working conditions to avoid excessive pressure loss caused by “small horse-drawn cart”.
V. Conclusion
The calculation of pressure loss of servo valve is a key link in the design of hydraulic system. Through the combination of theoretical analysis, experimental verification and simulation, engineers can evaluate the system performance more accurately, and provide a basis for system energy saving, heat dissipation control and stability improvement. With the continuous development of hydraulic technology, the pressure loss control of servo valve will develop in a more efficient and intelligent direction.