Centrifugal pump design and analysis

AIM -

Design of centrifugal pump and its flow analysis .

OBJECTIVE -

Construct a performance diagram

Obtain the relationship between Pressure ratio and mass flow rate

INTRODUCTION -

Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic axisymmetric work-absorbing tubromachinery. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from which it exits.

Common uses include water, sewage, agriculture, petroleum and petrochemical pumping. Centrifugal pumps are often chosen for their high flow rate capabilities, abrasive solution compatibility, mixing potential, as well as their relatively simple engineering. A centrifugal fan is commonly used to implement a vaccum cleaner. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.

Working of centrifugal pump - Like most pumps, a centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure.

Application of centrifugal pump -

• Oil & Energy - pumping crude oil, slurry, mud; used by refineries, power generation plants
• Industrial & Fire Protection Industry - Heating and ventilation, boiler feed applications, air conditioning, pressure boosting, fire protection sprinkler systems.
• Waste Management, Agriculture & Manufacturing - Wastewater processing plants, municipal industry, drainage, gas processing, irrigation, and flood protection
• Pharmaceutical, Chemical & Food Industries - paints, hydrocarbons, petrochemical, cellulose, sugar refining, food and beverage production
• Various industries (Manufacturing, Industrial, Chemicals, Pharmaceutical, Food Production, Aerospace etc.) - for the purposes of cryogenics and refrigerants.

DESIGN SETUP -

The centrifugal pump was designed in solidwork feature workbench using the sketch tool , extrude tool , sweep tool , pattern command . Below is the 3D model of the centrifugal pump.

In above figure we can see the impeller inside the casing . Here we have one inlet that at middle of the casing and one outlet which is inserted right into the casingfrom above. We have generated the Lids at the inlet and outlet of the pipe.

SIMULATION SETUP - Once the model is completed and lids are generated we move for the flow simulation.

Parameters for flow simulation -

Analysis type - Internal flow

Type of fluid - Water

Type of flow - Laminar and turbulent

Rotation type - Local region averaging

Rotation speed - 1000 rpm

Boundary condition - Inlet - Environmetal pressure

Outlet - Velocity 10(m/s)

After setting the pre-processing of the simulation we run it at 300 iteration. Then a new parametric study was generated to find the velocity , pressure , mass flow rate. In this parametric study we had three different input velocities that are 10 m/s , 15 m/s , 20 m/s to calculate mass flow rate , velocity plot and pressure plot.

CASE 1 - Velocity plot , Pressure plot and Flow trajectory at 10 m/s

Velocity plot -

Pressure plot -

Flow trajectory -

CASE 2 - Velocity plot , Pressure plot and Flow trajectory at 15 m/s

Velocity plot -

Pressure plot -

Flow trajectory -

CASE 3 - Velocity plot , Pressure plot and Flow trajectory at 20 m/s

Velocity plot -

Pressure plot -

Flow trajectory -

Plot of mass flow rate and pressure ratio using python programme.

The required data for plot was taken for excel file generated during parametric stiudy.

Pressure ratio = Outlet pressure ratio/Inlet pressure ratio

The above data gives us information about Pressure and mass flow rate at inlet and outlet. From this data the python code was made to plot relation between pressure ratio and mass flow rate.

The three values obtained are of pressure ratio of each inlet and outlet pressure and from these data we generate the plot.

Above is the plot of mass flow rate and pressure ratio.

CONCLUSION -

From above study we can conclude that with increase in mass flow rate the pressure ratio decrease. The pressure at the inlet always remains constant while it increase at the end of the plot.