# Some fundamental questions on turbomachinery

• mech-eng
In summary: Reynolds number is important because it tells you how similar two flows are. If two flows have similar Reynolds numbers, then their flow fields are similar. This can be useful in understanding how a particular engine might behave.

#### mech-eng

I try to understand topic of turbomachinery. Would someone like to make some guidance?

In that page I cannot understand some parts.

1) What does it mean by "above two conditions" in "Viscous effects must unfortunately be neglected, as it
is generally impossible to satisfy the above two conditions and have equal Reynolds numbers in the
model and prototype. I cannot see any so-called "two conditions" there.

The illustration is very hard to read .

Nidum said:
The illustration is very hard to read .

I am searching for a link, containing it. Maybe when you download it it would seem better.

Source is Fluid Mechanics by Streeter/Wylie/Bedford and page 506, 11.1 Homologuos Units: Specified Speeds

Thank you.

Can you photograph the page instead of scanning it ?

It was already a photograph but I have a different idea I can upload the page in Spanish and then write the words and some simple equations. Equations can be seen in Spanish version as well? May do it?

Thank you.

It is written literally in the first sentence on that page. It tells you two conditions that must be satisfied in order to use a scale model of an engine. It then says that you usually can't meet both of those requirements and match Reynolds numbers, so generally you can't consider viscous effects in such tests.

#1: geometric similitude

#2: geometrically similar velocity vector diagrams at the entrance to, or exit from, the impellers.

Nidum said:
Can you photograph the page instead of scanning it ?

It is written literally in the first sentence on that page. It tells you two conditions that must be satisfied in order to use a scale model of an engine. It then says that you usually can't meet both of those requirements and match Reynolds numbers, so generally you can't consider viscous effects in such tests.

1) What does geometric similitudes refer to in that context? Similitudes between what and what? Reality and model?

2) Why is it important to match Reynolds numbers?

Thank you.

I'd suggest you might be a little ahead of yourself in reading about turbomachinery if you aren't familiar with Reynolds number yet.

And it says it all right there: geometric similitude and geometrically similar velocity fields. I'm not really sure what you are missing here. Are you aware of the topic of the discussion on that page?

What does geometric similitudes refer to in that context? Similitudes between what and what? Reality and model?

Two engines with the same geometry but different sizes . Usually means a full size engine and a scaled down version . The scaled down version is used for research and development prior to designing and building the full size version .

The scaled down version is not always a complete engine . Quite commonly scaled down versions of sub assemblies and individual components are used .

There is another way of doing scaled down tests . Full size engine components are used but with reduced running conditions . For instance useful information about performance of turbine blades can be obtained by testing them in a moderate speed cold air flow .

## 1. What is turbomachinery?

Turbomachinery is a general term used to describe any type of machine that transfers energy between a rotor and a fluid, such as air or gas. This includes devices such as turbines, compressors, and fans.

## 2. What are the main components of turbomachinery?

The main components of turbomachinery include a rotor, which is a rotating part, and a stator, which is a stationary part. These components work together to transfer energy from the fluid to the rotor and vice versa.

## 3. How does turbomachinery work?

Turbomachinery works by using the energy from a fluid to rotate the rotor. The fluid enters the machine and is directed onto the blades of the rotor, causing it to rotate. This rotation then transfers energy to the fluid, which exits the machine with increased energy.

## 4. What are the applications of turbomachinery?

Turbomachinery is used in a wide range of applications, including power generation, aviation, and industrial processes. It is also used in heating, ventilation, and air conditioning systems, as well as in pumps and fans.

## 5. What are some fundamental questions about turbomachinery?

Some fundamental questions about turbomachinery include how to design and optimize these machines for specific applications, how to improve their efficiency and reliability, and how to minimize their environmental impact. Other questions may focus on the effects of operating conditions, such as temperature and pressure, on the performance of turbomachinery.