internal combustion engine cycle thermodynamics

[projectSER]

Dear users,

I have a seen a line in the book INTERNAL COMBUSTION ENGINE FUNDAMENTALS by Heywood which has baffled me and would like to ask the community if somebody can give me some insight into this piece of thermodynamics.

Here is what is stated;

For combustion process:
For the constant volume cycle,
v3=v2

u3-u2=0​

For constant pressure cycle
P3=P2

h3-h2=0​

Where v-volume, u-internal energy, P-pressure, h-enthalpy

I just don't see how any kind of combustion process can lead to no change in internal energy or enthalpy? Is there a typo in this book has anyone come across this conundrum?

From the book see Chapter 5, Ideal Models of Engine Cycles
section 5.3 Thermodynamic relations for engine processes
equations 5.7 on page 165

 

[IRstuff]

What is the context, page number, chapter?

TTFN (ta ta for now)
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[projectSER]

It's Chapter 5, Ideal Models of Engine Cycles
section 5.3 Thermodynamic relations for engine processes
equations 5.7 on page 165

 

[SwinnyGG]

Combustion is a chemical reaction. Like every other chemical reaction, it does not create energy- it only converts it from one form (chemical potential energy in the C-H bonds of the hydrocarbon chains) to another (heat in the fluid being pumped, i.e. the air in the chamber).

Also note the name of the chapter you're reading. Ideal Models of Engine Cycles

These equations represent an idealized, simplified combustion model, which negates a bunch of factors that make these equations not correct in the real world.

 

[EdStainless]

One of those ideal assumptions is likely that there is no heat transfer during the process.
I presume that there are T-s or P-V plots that go with these.

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