Hydrodynamic calculation Needle valve
Values for calculation
Calculation
Velocity in valve
Theoretical pressure in the valve at full opening
Pressure parameter
Effective closing time factor
Under-pressure behind the valve
Stroke from open position |
First stage of cavitation |
Second stage of cavitation |
Fully developed cavitation |
---|---|---|---|
$s$ | $σ_1$ | $σ_2$ | $σ_{min}$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{ }$ |
No data |
$σ_2 \mathrm{[-]}$
$σ_{min} \mathrm{[-]}$
No data |
Stroke from open position |
Flow coefficient for $ σ_1 $ |
Flow coefficient for $ σ_2 $ |
Flow coefficient for $ σ_{min} $ |
---|---|---|---|
$s$ | $K_{Q-σ_1}$ | $K_{Q-σ_2}$ | $K_{Q-σ_{min}}$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{ }$ |
No data |
$K_{Q-σ_2} \mathrm{[-]}$
$K_{Q-σ_{min}} \mathrm{[-]}$
No data |
Stroke from open position |
Coefficient of hydraulic force on a needle in the axis x for $ σ_1 $ |
Coefficient of hydraulic force on a needle in the axis x for $ σ_2 $ |
Coefficient of hydraulic force on a needle in the axis x for $ σ_{min} $ |
---|---|---|---|
$s$ | $K_{x-σ_1}$ | $K_{x-σ_2}$ | $K_{x-σ_{min}}$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{ }$ |
No data |
$K_{x-σ_2} \mathrm{[-]}$
$K_{x-σ_{min}} \mathrm{[-]}$
No data |
Stroke from open position |
Flow coefficient |
Coefficient of hydraulic force on a needle in the axis x |
---|---|---|
$s$ | $K_Q$ | $K_x$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ |
No data |
No data |
No data |
Stroke from open position |
Loss coefficient |
Reduced free flow area in the throttle control system |
Relative flow |
Flow of water in the pipeline |
Water velocity in pipeline |
---|---|---|---|---|---|
$s$ | $ζ$ | $f_r$ | $Q_p$ | $Q$ | $v$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{m^3/s}$ | $\mathrm{m/s}$ |
No data |
No data |
$Q_p \mathrm{[-]}$
No data |
$v \mathrm{[m/s]}$
No data |
Stroke from open position |
Loss of pressure on the valve |
Pressure on the valve |
Cavitation number |
Forces on the needle |
---|---|---|---|---|
$s$ | $H_L$ | $H_v$ | $σ$ | $F_x$ |
$\mathrm{\%}$ | $\mathrm{m}$ | $\mathrm{m}$ | $\mathrm{ }$ | $\mathrm{kN}$ |
No data |
$H_v \mathrm{[m]}$
No data |
No data |
No data |
Stroke from open position |
Aerated coefficient |
Coefficient of under-pressure of aerated hole |
Under-pressure in the aerated pipeline |
Air flow |
---|---|---|---|---|
$s$ | $β$ | $f_{air}$ | $p_{air}$ | $Q_{air}$ |
$\mathrm{\%}$ | $\mathrm{ }$ | $\mathrm{ }$ | $\mathrm{Pa}$ | $\mathrm{m^3/s}$ |
No data |
No data |
No data |
No data |
No data |
Stroke from open position |
Air velocity |
The flow area of the aerated hole |
The flow area of the aerated pipeline |
---|---|---|---|
$s$ | $v_{air}$ | $A_{air}$ | $A_{air-pipe}$ |
$\mathrm{\%}$ | $\mathrm{m/s}$ | $\mathrm{m^2}$ | $\mathrm{m^2}$ |
No data |
No data |
No data |
No data |