Centrifugal compressors, adiabatic compression

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SUMMARY

This discussion focuses on the calculations involved in adiabatic compression for a Cummins 5.9L diesel engine. The user is attempting to create a spreadsheet to compute parameters such as final pressure, work done, and final temperature based on initial conditions of 1 m³ volume at atmospheric pressure (101,000 Pa) and temperature (300 K). The user has calculated the number of moles (n) using the ideal gas law and is seeking to understand the volumetric ratio after compression, which is affected by heat addition and compressor efficiency. The conversation highlights the need for precise calculations in thermodynamics to accurately model engine performance.

PREREQUISITES
  • Understanding of ideal gas law (PV = nRT)
  • Knowledge of adiabatic processes in thermodynamics
  • Familiarity with volumetric efficiency and pressure ratios
  • Basic skills in using spreadsheet software for calculations
NEXT STEPS
  • Research the principles of adiabatic compression in thermodynamics
  • Learn how to calculate compressor efficiency and its impact on performance
  • Explore the use of online calculators for thermodynamic properties
  • Investigate the relationship between temperature, pressure, and volume in gas dynamics
USEFUL FOR

Engineers, automotive technicians, and students studying thermodynamics who are involved in designing or analyzing compressor systems, particularly in diesel engines.

Rx7man
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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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I'm a bit confused by your terminology - what type of engine are you trying to develop the spreadsheet for ??
 
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
 

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