Centrifugal pump design and analysis

AIM:

To create a centrifugal pump geometry to perform the flow simulation using Solidworks and obtaining the analysis results to view the relationship between the mass flow rate and pressure ratio.

OBJECTIVE

• To Create a 3D Model of Centrifugal Pump and to run a Flow Simulation.
• To Obtain a relation between Pressure ratio and Mass Flow rate.

THEORY:

1. Centrifugal Pump- Centrifugal pumps are used to induce flow or raise pressure of a liquid. Its working is simple. At the heart of the system lies impeller. It has a series of curved vanes fitted inside the shroud plates. The impeller is always immersed in the water. When the impeller is made to rotate, it makes the fluid surrounding it also rotates. This imparts centrifugal force to the water particles, and water moves radially out. In Fig this process is illustrated. Since the rotational mechanical energy is transferred to the fluid, at the discharge side of the impeller, both the pressure and kinetic energy of the water will rise. At the suction side, water is getting displaced, so a negative pressure will be induced at the eye. Such a low pressure helps to suck fresh water stream into the system again, and this process continues.

PROCEDURE:

3D MODEL:

1. To create the centrifugal pump geometry, starting the sketch from the top plane in Solidworks. Two circles that are concentric with the origin are sketched with diameter 0.04m and dia 0.08m respectively.
2. Constructing two arcs between the two circles for the vanes of the impeller that are concentric. Trimming the extra outer circle and circular patterning the vanes as 5 concerning the origin. Now extruding the sketch from midplane to get the profile.
3. From the top plane, drawing another circle from its origin and extruding from the midplane to get the geometry. *Merge results are unselected. Now from the top plane, a new circle is sketched and extruded.
4. With the centreline, a tangent over the circle from the top plane and a line is drawn parallel and equal to the centreline inside the circle at a distance of 0.005m.
5. A reference plane is drawn on the endpoint of the line drawn and a circle is drawn on that plane and sweeper into the circle. From the top face of the profile, the circle is drawn and extruded for the inlet cavity.
6. Using the direct editing tab, combining the profile into a single geometry. Using the shell, the thickness is provided to the geometry.
7. Now from the top plane, the circle is drawn outside the edges of vanes end extruded in the midplane such that it does not interfere with vanes and other parts.

BASELINE SIMULATION:

1. For the watertight body, the lid is created on both the circular profile of the centrifugal pump. In the wizard menu, the following are provided as inputs for the baseline simulation for the centrifugal pump.
   a) Units: SI units
   b) Fluid: Water
   c) Simulation Type: Internal Flow
2. To perform the flow simulation inside the centrifugal pump, the rotation is included with the local region averaged.
   Boundary Conditions:
   a) Environment Pressure = 101325 pa
   b) Outlet Velocity = 10 m/s
3. Rotating Region = Outside the vanes (Boss Extrude 4) with 1000 rad/s
4. In the component control, boss extrude is excluded from selection, and the number of iteration for the solver is set as 1000 in the calculation control option.
5. Insert Surface Goals of Avg Total Pressure = Outlet Profile (LID2) and a mass flow rate is provided for both the lids.
6. Global Mesh is refined at level 3 and advanced channel refinement. Then the simulation is performed and the cut plots are created for the Pressure and Velocity and get the values for the goals.
7. After the completion of the baseline simulation, the parametric study is calculated.

PARAMETRIC STUDY:

1. To perform the parametric study on the compressor pump, the followings are provided:
   Input parameters = Velocity normal to face (outlet velocity)
   The input values are ranged from 10m/s to 30m/s with number of values 6 (i.e.) 10m/s, 14m/s, 18m/s, 22m/s, 26m/s & 30m/s.
   Output Parameters = All goals and all results are inserted.
2. Running the simulation, we get the following results.

Results-Grid Dependency test:

For this test, I have set the input variables as output velocity and the values are 10 m/s, 15 m/s, 20 m/s, 25 m/s, 30 m/s. The Level of mesh is set as 3. The number of Iteration for the solver is set as 500 in the calculation control option. The mesh is refined to advanced channel refinement.

Goal (Value)	Design Point 1	Design Point 2	Design Point 3	Design Point 4	Design Point 5
Velocity normal to face (Outlet Velocity 2) [m/s]	10	15	20	25	30
inlet total pressure [Pa]	111008.1074	109034.8846	101325	101337.5316	101325
outlet total pressure [Pa]	1535736.603	1408315.141	1068537.797	974117.9613	915280.3292
mass flow rate at outlet [kg/s]	-0.484246239	-0.726385492	-0.968848913	-1.210794692	-1.453659743
mass flow rate at inlet [kg/s]	-0.404036465	-0.27386767	0.952775936	1.011519333	1.580670624

Output:

Inlet pressure remains the same for all the cases but the outlet pressure varies. When the flow rate at the outlet is high the pressure reduces at outlet which results in the decrease in the pressure ratio.

i. Design point 1 @ velocity 10m/s

Velocity Plot @ 10m/s

pressure plot @ 10m/s

velocity trajectory @ 10m/s

ii. Design point 2 @ velocity 15m/s

Velocity Plot @ 15m/s

pressure plot @ 15m/s

velocity trajectory @ 15m/s

iii. Design point 3 @ velocity 20m/s:

Velocity Plot @ 20m/s

pressure plot @ 20m/s

velocity trajectory @ 20m/s

iv. Design point 4 @ velocity 25m/s:

Velocity Plot @ 25m/s

pressure plot @ 25m/s

velocity trajectory @ 25m/s

v. Design point 5 @ velocity 30m/s:

Velocity Plot @ 30m/s

pressure plot @ 30m/s

velocity trajectory @ 30m/s

Graphs and comparison

Pressure Ratio

Velocity normal to face (Outlet Velocity 2) [m/s]	inlet total pressure [Pa]	outlet total pressure [Pa]	preasure ratio
10	111008.1074	1535736.603	13.83445
15	109034.8846	1408315.141	12.91618
20	101325	1068537.797	10.54564
25	101337.5316	974117.9613	9.6126
30	101325	915280.3292	9.03311

GOAL PLOTS:

Goal (Value)	Design Point 1	Design Point 2	Design Point 3	Design Point 4	Design Point 5
Velocity normal to face (Outlet Velocity 2) [m/s]	10	15	20	25	30
inlet total pressure [Pa]	111008.1074	109034.8846	101325	101337.5316	101325
outlet total pressure [Pa]	1535736.603	1408315.141	1068537.797	974117.9613	915280.3292
mass flow rate at outlet [kg/s]	-0.484246239	-0.726385492	-0.968848913	-1.210794692	-1.453659743
mass flow rate at inlet [kg/s]	-0.404036465	-0.27386767	0.952775936	1.011519333	1.580670624

total pressure at inlet:

total pressure at outlet:

Mass flow rate at inlet:

Mass flow rate at outlet:

Graph of pressure ratio and mass flow rate:

Observation and Conclusion

1. From the First plot we can see that initially, the velocity is less so the mass ow rate is less when the velocity increases the mass ow rate increases.

2. From the Second plot, we can see that the pressure ratio is high for low velocity and pressure ratio starts to decrease when the velocity increases.

3. From the graphs, I can gure out that due to performance failure of the laptop the pressure ratio curve varied but later on it showed study decrease in pressure ratio.

4. Velocity plots have proper indication of out ow velocity as assigned.Show in the plots above.

5. A pump does not create pressure it only creates ow. Pressure is a measurement of the resistance to flow.

6. It is evident from other similar studies pressure ratio decrease as the velocity at outlet increase but in my case, the pressure ratio varied due to technical failure of my laptop which did not perform accurately as expected.