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\ [-] $
$ σ_{min}\ [-] $
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}\ [-] $
$ K_{Q-σ_{min}}\ [-] $
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}\ [-] $
$ K_{x-σ_{min}}\ [-] $
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\ [-] $
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 |