Centrifugal compressors, adiabatic compression

In summary: I don't remember the ideal gas law...You are developing a spreadsheet to input engine parameters at a given rotational speed. The engine is a Cummins 5.9L diesel. You are not very clear about what you are trying to develop the spreadsheet for.
  • #1
Rx7man
425
189

Homework Statement


I am working on creating a spreadsheet where you can input the parameters of an engine at a given rotational speed such as volumetric efficiency, boost pressure, atmospheric pressure and temperature, and compressor efficiency... It's been a very long time since I've done thermodynamics, and have forgotten too much of it to derive all the equations.

To start with, let's forget about engine speed, volumetric efficiency, and compressor efficiency, and assume perfect adiabatic compression.

The online calculators I found require the volumes to be known, not the pressures

Homework Equations


Working with an initial volume of 1 m3 at atmospheric conditions

P initial = 101,000 pa
T initial = 300K
V initial = 1
Calculate n from ideal gas law: PV = nRT, (n= PV/RT), n = (101000*1)/(8.314*300), n = 40.5

We know n inital = n final

Pfinal = 303,000 pa (3:1 pressure ratio)
Work = ?
T final =?
V final =?

The Attempt at a Solution


I was trying to work out the solution with the help of this site but I'm not getting too far with it
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/adiab.html

When I get there, I will factor in the compressor efficiency as a function of extra work added to the system... So if a perfect system would require 10J, a 50% efficient system would require 20J, raising the temperature and volume, but keeping the pressure the same (since the pressure is what I measure and control)
Thanks for the help... My mind has turned to mush looking at this for a couple hours
 
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  • #2
I'm a bit confused by your terminology - what type of engine are you trying to develop the spreadsheet for ??
 
  • #3
Cummins 5.9L diesel. the engine isn't terribly important until you want to know the flow...

Where I mention V initial I just choose 1 m^3, which would be the volume of air before the turbocharger, and V final is the volume after the turbocharger, They are just a ratio, not an absolute amount.. I know the pressure ratio (3), but am looking for the volumetric ratio which will NOT be 1/3 because of a lot of added heat, and that's where I run into problems
 

1. What is a centrifugal compressor?

A centrifugal compressor is a type of dynamic compressor that uses rotating impellers to increase the pressure and flow of a gas, typically air. It operates on the principle of centrifugal force, where the gas is drawn into the center of the impeller and then accelerated outward by the high-speed rotation of the impeller blades.

2. What is adiabatic compression?

Adiabatic compression is a thermodynamic process in which the temperature of a gas increases due to its compression without any heat transfer occurring. This means that the energy added to the gas during compression is retained as internal energy, resulting in an increase in temperature and pressure.

3. How do centrifugal compressors achieve compression?

Centrifugal compressors achieve compression through a combination of centrifugal force and a decrease in volume. The gas is drawn into the center of the impeller and then accelerated outward, causing an increase in velocity and a decrease in volume. This decrease in volume leads to an increase in pressure, resulting in compressed gas exiting the compressor.

4. What are the advantages of using a centrifugal compressor for adiabatic compression?

One advantage of using a centrifugal compressor for adiabatic compression is its ability to handle large volumes of gas at high flow rates. It also has a relatively simple design and can operate at high speeds, making it suitable for a wide range of applications. Additionally, adiabatic compression in a centrifugal compressor reduces the risk of heat damage to the gas being compressed.

5. What are some common uses for centrifugal compressors utilizing adiabatic compression?

Centrifugal compressors with adiabatic compression are commonly used in industrial processes, such as in the oil and gas industry for gas compression and transportation. They are also used in air conditioning and refrigeration systems, as well as in power plants for gas turbine compression. In addition, centrifugal compressors are often used in the aerospace industry for aircraft engines and in the chemical industry for gas processing and transportation.

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