ABSTRACT
In recent years, the importance of energy conservation has been in the limelight
of the whole society, and subsequently the situation of energy consumption in
pneumatic system has inevitably aroused more and more concern. As an indispensable
part of pneumatic system, solenoid valves would take a significant role in the study of
energy conservation in pneumatic system. Through theoretical analysis and test, the
relationship between flow rate characteristic——critical pressure ratio b and energy
loss of compressed air going through the solenoid valve was studied. Besides, the
method of numerical simulation was adopted to observe the flow field in the valve
and optimize the channel configuration for a larger b and lower energy loss.
Before theoretical analysis, the thermodynamic concept of exergy was
introduced as the evaluating criterion of compressed-air energy loss. Through
theoretical deduction, the calculation formula of compressed-air exergy was
constructed, of which the influential factors were also discussed. In the test, two
solenoid valves were chosen as the test objects with their flow rate characteristics C
equal and b different and the parameters to be tested were the inlet and outlet
pressures of the valves. The results of test corresponded with the theoretical analysis,
and based on which it can be arrived at that: Given the mass flow rate and inlet
pressure unchanged, for two solenoid valves with different b, the exergy loss of
compressed air going through the valve was greater with a larger b; With the mass
flow rate increasing, the energy-saving effect of the valve with a larger b would be
more and more remarkable. On the basis of conclusions stated above, a further
analysis was carried out and another conclusion can be drawn that: Given the mass
flow rate and inlet pressure unchanged, the exergy loss of compressed air will decline
almost in a linear way when b was raised.
The three-dimensional model of the flow channel was built based on the valve in
the test. After being meshed in Gambit, the model was imported into Fluent to
simulate the flow field in the valve. Firstly, the reliability of the model was examined
by comparison between test and simulation results. Then, the distribution of pressure
contours and velocity vectors were displayed in order to analyze the influence of flow
channel configuration on flow field and find the typical zone with maximum pressure
drop and large eddy currents. Afterwards, a local configuration modification was
made on the original model to achieve a larger b and lower energy loss of compressed
air. At last, the optimization effect was examined by comparison between the original
and modified models.
From all the theoretical deduction, test results and simulation analysis, it can be
concluded that the critical pressure ratio b, one of the flow rate characteristics, can be
an index for energy loss in solenoid valves, and according to it the solenoid valves
selection can be guided in pneumatic system, furthermore, to obtain a larger b the
flow channel configuration should be optimized.
Key Words: solenoid valve, critical pressure ratio, exergy, energy