Internal combustion engine problem.

• fraggedmemory
In summary: That's why it's hard to conceptualize the problem.In summary, the problem involves an internal combustion engine that runs on octane with an enthalpy of combustion of -5512 kJ/mol. The mass of octane is not specified, but we know that the molar mass of octane is 0.1142 kg/mol and that there are 26.3 moles of octane involved. The engine temperature is given as 2000 degrees C and the exit temperature is 800 degrees C. However, there is no information about the starting temperature, pressure, or amount of octane involved. This makes it difficult to accurately calculate the work done by the engine.
fraggedmemory
An internal combustion engine runs on octane, the enthalpy of combustion is -5512 kJ/mol. The mass of 1 gallon of fuel is 3 kg.
The engine temperature is 2000 degrees C and the exit temperature is 800 degrees C. What is the work done?

The total enthalpy is -145053 kJ. The total number of moles of octane is 26.3. The molar mass of octane is .1142 kg/mol

I spent a good deal of time on this, and I am not sure how to conceptualize this problem.

*I edited the problem so you don't have to read the poorly written original problem. *

Last edited:
fraggedmemory said:
An internal combustion engine runs on octane, the enthalpy of combustion is -5512 kJ/mol. The mass of 1 gallon of fuel is 3 kg.
The engine temperature is 2000 degrees C and the exit temperature is 800 degrees C. What is the work done?

The total enthalpy is -145053 kJ. The total number of moles of octane is 26.3. The molar mass of octane is .1142 kg/mol

I spent a good deal of time on this, and I am not sure how to conceptualize this problem.

*I edited the problem so you don't have to read the poorly written original problem. *
You've mentioned you've spent a good deal of time on this, so show us what you've come up with so far! We can't help you unless you show us your work.

That said, I think I'd like to see original problem anyway. The way it's written above contains multiple ambiguities. For example, are we dealing with 1 gallon of octane, 3 kg of octane, or some other amount of octane? It can't be both 1 gallon and 3 kg of pure octane, since the density of octane is $0.703 \ \mathrm{gm/cm^3} = 2.661 \ \mathrm{kg/gal}$. So the first question is, how much actual ocatane are we dealing with here?

The problem states the "ending" temperature is 800 deg C, but what about the "starting" temperature? Is that the same as the engine temperature? What about pressure? Is the starting pressure the same as the ending pressure?

I think we can assume that the reaction involves oxygen and the byproducts are water and carbon dioxide, but what are the starting temperature and pressure of intake gas?

My point of all this is there seems to be some information left out here and there.

1. How does an internal combustion engine work?

An internal combustion engine works by using controlled explosions to create energy. Fuel is mixed with air and ignited inside the engine's cylinders, which produces a series of small explosions. These explosions create pressure that pushes against pistons, which then turn a crankshaft and ultimately power the vehicle.

2. What are common problems with internal combustion engines?

Some common problems with internal combustion engines include overheating, oil leaks, faulty spark plugs, and issues with the fuel system. These problems can lead to reduced performance and potential engine failure if not addressed.

3. How do you diagnose an internal combustion engine problem?

Diagnosing an internal combustion engine problem typically involves checking for warning signs such as strange noises, decreased performance, and visible leaks. Additionally, a mechanic may use diagnostic tools and perform tests to identify the specific issue.

4. How can I prevent internal combustion engine problems?

To prevent internal combustion engine problems, it is important to regularly maintain your vehicle. This includes changing the oil and other fluids, replacing worn-out parts, and following the manufacturer's recommended maintenance schedule. It is also important to use high-quality fuel and avoid overloading the engine.

5. Can internal combustion engine problems be fixed?

In most cases, internal combustion engine problems can be fixed by a trained mechanic. The specific solution will depend on the type and severity of the problem. Regular maintenance can also help prevent potential issues and extend the lifespan of the engine.

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