Torque for a radial vane water pump

In summary, the conversation discussed a design for a spinning rotor/impellor with open channels directed radially outward, similar to a radial vane centrifugal pump. The channels have constant area from inner to outer radius, and the goal is to calculate the torque and radial velocity of the fluid leaving the channels. The Euler Turbine Equation was recommended for this calculation, and using the given values, the velocity head, torque, and radial velocity were calculated at both radii.
  • #1
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Have a spinning rotor/impellor with open channels directed radially outward (similiar to a radial vane centrifigal pump with 90 degree straight blades - such as an older automotive heater fan ). The channels have constant area from the inner to outer radius. Realize this isn't a very efficient design but would like to calculate the torque and radial velocity of the fluid leaving the channels. Have tried using the basic equations for turbomachinery but with the pure radial flow (ideal) haven't had much luck. Attached jpg of the layout with dimensions.

Fluid = water
R1 = 1 inch
R2 = 3 inches
RPM = 2400 RPM
Tangential Velocity at R1 = 20.94 feet per sec
Tangential Velocity at R2 = 62.83 feet per sec
Area of each flow channel A1 = .7763 square inches

Thanks for any help.
 

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  • #2
The equation you are looking for is the Euler Turbine Equation, which states that the change in static pressure (dp) across the impeller is equal to the product of the impeller's area of flow A and the fluid's velocity head v²/2g. Solving this equation for the velocity head yields:v² = 2g(dp/A)Where g is the acceleration due to gravity, dp is the pressure difference across the impeller, and A is the impeller's area of flow. Using the given values, we can solve for the velocity head at both radii: At R1: v1² = 2*32.2*(3/0.7763) = 845.9 ft²/sec²At R2: v2² = 2*32.2*(12/0.7763) = 3383.6 ft²/sec²To calculate the torque, we need to multiply the velocity head at both radii by the impeller's area of flow: At R1: T1 = 0.7763*845.9 = 661.6 lb-ftAt R2: T2 = 0.7763*3383.6 = 2624.4 lb-ftFinally, we can calculate the radial velocity of the fluid leaving the channels by dividing the velocity heads by the radii of the impeller:At R1: vr1 = 845.9/1 = 845.9 ft/secAt R2: vr2 = 3383.6/3 = 1161.2 ft/sec
 
  • #3


Thank you for sharing your design and dimensions for the radial vane water pump. To calculate the torque and radial velocity of the fluid leaving the channels, we need to consider a few factors.

Firstly, the torque on the rotor/impellor will be equal to the product of the force acting on the vanes and the radius at which the force is acting. In this case, the force acting on the vanes will be the pressure difference between the inlet and outlet of the pump, and the radius at which this force is acting will be the average radius of the vane channels. This can be calculated using the following equation:

Torque = Force x Average Radius

To calculate the force, we need to consider the Bernoulli's equation, which states that the total pressure of a fluid remains constant along a streamline. In this case, the total pressure at the inlet will be equal to the sum of the static pressure and the dynamic pressure, which is the pressure due to the velocity of the fluid. At the outlet, the total pressure will be equal to the static pressure only.

Using this principle, we can calculate the force acting on the vanes as:

Force = (P1 - P2) x A1

Where P1 is the total pressure at the inlet, P2 is the static pressure at the outlet, and A1 is the area of each flow channel.

To calculate the average radius, we can use the following equation:

Average Radius = (R1 + R2)/2

Substituting these values, we can calculate the torque on the rotor/impellor.

To calculate the radial velocity of the fluid leaving the channels, we can use the equation for centrifugal force, which is given by:

Fc = mv^2/r

Where m is the mass flow rate of the fluid, v is the tangential velocity at the outlet, and r is the radius of the outlet. We can calculate the mass flow rate using the equation:

m = ρ x Q

Where ρ is the density of water and Q is the volumetric flow rate.

Substituting these values, we can calculate the radial velocity of the fluid leaving the channels.

It is important to note that these calculations will provide an estimate of the torque and radial velocity, as there may be other factors that can affect the performance of the pump, such as friction losses and inefficiencies in the design. Further analysis and experimentation may be required to accurately determine these
 

1. What exactly is torque in relation to a radial vane water pump?

Torque is a measure of the rotational force or moment that is applied to the vanes of a radial vane water pump. It is a crucial factor in determining the pump's ability to move water efficiently.

2. How is torque calculated for a radial vane water pump?

To calculate torque for a radial vane water pump, the force applied to each vane must be multiplied by the distance from the center of rotation to the point where the force is applied. This calculation is typically done using the equation: torque = force x distance.

3. What factors can affect the torque of a radial vane water pump?

The factors that can affect torque in a radial vane water pump include the speed of rotation, the number and size of the vanes, the viscosity of the fluid being pumped, and any resistance or friction in the pump's components.

4. How does torque impact the performance of a radial vane water pump?

The torque generated by a radial vane water pump is directly related to its ability to move water. Higher torque allows the pump to overcome resistance and move water at a faster rate, while lower torque may result in slower water movement and reduced efficiency.

5. Are there any maintenance or care steps that can help maintain torque in a radial vane water pump?

Regular maintenance and care, such as cleaning and lubrication of the pump's components, can help maintain torque in a radial vane water pump. It is also important to monitor and address any potential issues, such as worn or damaged vanes, that may affect the pump's torque over time.

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