(Extremely basic) centrifugal pump design

In summary, the conversation discusses the design of a basic centrifugal pump and the resources available for learning about its design. The main considerations for designing a pump include the operating conditions, such as head and flow rate, and the impeller design. The volute also plays a role in the design, but it is primarily to contain the fluid. The book Centrifugal Pumps and Blowers by A.H. Church is recommended as a resource for learning about pump design.
  • #1
ecfed
2
0
Alright everyone, I know this is a huge question, but I've done enough homework to at least have informed ignorance on the subject. I posted a similar topic here, but that question was more conceptual and this definitely is much more of an applied use question.

(Edit: I realize that the above post was made on a newer account; issue of using multiple emails throughout the years. I may jump onto that account for replies for continuity purposes)

I'm interested in designing an extremely basic, "proof-of-concept" centrifugal pump; it need not be energetically-efficient nor anything good enough to make it to a professional-level design; it simply needs to be able to supply fluid at the given flow rate and head that I need for the application, regardless of power input and efficiency (once I have a simple design, then I'll evaluate the feasibility). To make this somewhat easier, I'm willing to accept a wide measure of "tolerance" in the end specifications; it doesn't have to meet up. What I'm looking to gain out of this is the design practice, something I haven't been able to learn elsewhere.

The reason why I decided to ask this here is that I've looked up many centrifugal pump resources, and I can't for the life of me seem to find a resource approaching them from a component-level design perspective. Most resources out there seem to be geared towards educating engineers or teams in the basics well enough to prepare them to be able to select the proper pump for an application, but no documents I consulted really broke down the design elements. I've found documents about impeller design (velocity triangles, etc.), but these don't account for the volute, of which I haven't been able to find any documents on. Even then, the impeller design docs I found don't tie the impeller specs into the pump specs (head, flow rate, etc.) very well so even if I could make a simple impeller, I don't feel like I could make a very good pump. All of this feels like a very "black art" to me at this point.

So, how would one go about designing a pump? Obviously, the operating conditions must first be quantified, so head and flow-rate, but how do these then get turned into impeller design considerations? I know the volute plays a role, but what is the math behind it? I suppose, if nothing else, I'm looking for some spirited discussion so that way I can know where to look better.
 
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  • #2
Centrifugal pumps are integral designs because all the parts must work together.

Given an RPM, and knowing the maximum pressure required with no flow you can select an impeller diameter. Knowing the maximum flow at low pressure you can select an outlet diameter. Knowing the inlet pressure you can select an input port diameter.

The pressure difference times the flow volume will give the power requirement and so determine the drive shaft diameter needed at the design RPM.
 
  • #3
ecfed said:
Alright everyone, I know this is a huge question, but I've done enough homework to at least have informed ignorance on the subject. I posted a similar topic here, but that question was more conceptual and this definitely is much more of an applied use question.

(Edit: I realize that the above post was made on a newer account; issue of using multiple emails throughout the years. I may jump onto that account for replies for continuity purposes)

I'm interested in designing an extremely basic, "proof-of-concept" centrifugal pump; it need not be energetically-efficient nor anything good enough to make it to a professional-level design; it simply needs to be able to supply fluid at the given flow rate and head that I need for the application, regardless of power input and efficiency (once I have a simple design, then I'll evaluate the feasibility). To make this somewhat easier, I'm willing to accept a wide measure of "tolerance" in the end specifications; it doesn't have to meet up. What I'm looking to gain out of this is the design practice, something I haven't been able to learn elsewhere.

The reason why I decided to ask this here is that I've looked up many centrifugal pump resources, and I can't for the life of me seem to find a resource approaching them from a component-level design perspective. Most resources out there seem to be geared towards educating engineers or teams in the basics well enough to prepare them to be able to select the proper pump for an application, but no documents I consulted really broke down the design elements. I've found documents about impeller design (velocity triangles, etc.), but these don't account for the volute, of which I haven't been able to find any documents on. Even then, the impeller design docs I found don't tie the impeller specs into the pump specs (head, flow rate, etc.) very well so even if I could make a simple impeller, I don't feel like I could make a very good pump. All of this feels like a very "black art" to me at this point.

So, how would one go about designing a pump? Obviously, the operating conditions must first be quantified, so head and flow-rate, but how do these then get turned into impeller design considerations? I know the volute plays a role, but what is the math behind it? I suppose, if nothing else, I'm looking for some spirited discussion so that way I can know where to look better.
The book Centrifugal Pumps and Blowers by A.H. Church (1944) is one of the classic texts on the subject. Second hand copies of this book are available thru distributors like Amazon.com or second-hand sellers like Abe Books. You can also use the book search feature at Amazon to find more modern titles on this subject if Church is too old.

As far as I remember about my pump design class, no one cares about the volute, 'cuz it's there just to keep the water from spraying out of the impeller. The design of the impeller and the speed and power of the motor determine the flow rate and head you can obtain from the pump. Unless there are some unusual circumstances, I don't believe there are many people who do a complete, "clean sheet" design of a centrifugal pump. I think most pump manufacturers have designed enough impellers to suit just about any head-flow combination normally encountered in industry. There's probably not much new in pumps except for converting from paper drawings to digital CAD in the last 30 years or so. Maybe someone has studied CFD and pumps, but I'm not sure if the subject is advanced enough or the benefits of applying CFD to pump design are worth the effort.
 
  • #5
The exit volute is there to allow some of the kinetic energy in water stream to recover into static pressure .

Essentially the same as on CF compressor on gas turbine but technically less demanding .
 
  • #6
There are three basic shapes for blading on the impeller - straight , back curved and forward curved .

Each shape has merit for particular performance requirements .

Since water is nominally incompressible the channels between the vanes need to be approximately constant cross section area with increasing radius so as to minimise cavitation problems .

Ideally there would be inlet guide vanes and a curved lead in on impeller blades but many pumps omit these refinements .

Ask more specific questions if you want to .
 

1. How does a centrifugal pump work?

A centrifugal pump works by converting mechanical energy from a rotating impeller into fluid flow. The impeller spins at high speeds, creating a centrifugal force that pushes the fluid towards the pump outlet. This creates a low-pressure area at the center of the impeller, causing fluid to be drawn into the pump. As the impeller continues to rotate, the fluid is pushed out through the outlet.

2. What are the main components of a centrifugal pump?

The main components of a centrifugal pump include the impeller, casing, and shaft. The impeller is responsible for creating the centrifugal force and is connected to the shaft, which rotates to power the pump. The casing is the outer covering that houses the impeller and helps to direct the fluid flow.

3. How is the performance of a centrifugal pump measured?

The performance of a centrifugal pump is typically measured by its flow rate, head, and efficiency. Flow rate refers to the volume of fluid that the pump can move in a given amount of time. Head is a measure of the pump's ability to lift the fluid to a certain height. Efficiency is a measure of how well the pump converts mechanical energy into fluid flow.

4. What are some common applications of centrifugal pumps?

Centrifugal pumps are used in a wide range of industries and applications, including water supply, wastewater treatment, irrigation, chemical processing, and oil and gas production. They are also commonly used in heating and cooling systems, as well as for circulating water in household appliances.

5. How can I improve the efficiency of a centrifugal pump?

To improve the efficiency of a centrifugal pump, it is important to select the right pump for the application, properly size the pump and its components, and maintain the pump regularly. Other factors that can affect efficiency include the design of the impeller and the system in which the pump is operating. Making sure the pump is operating at its best efficiency point (BEP) can also help improve efficiency.

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