What equation would be used to estimate the temperature?

In summary, the conversation discusses the process of compression in a Diesel engine and how it affects the temperature of the air in the cylinder. The adiabatic condition and ideal gas law are mentioned as methods for estimating the temperature, while the concept of quick compression is highlighted as the reason why spark plugs are not needed in a Diesel engine.
  • #1
jlmac2001
75
0
Can someone help me get started on this question?:

In a Diesel engine, atmospheric air is quickly compressed to about 1/20 of its original volume. Estimate the temperature of the air after compresion and explain why a Diesel engine does not require spark plugs.


What equation would be used to estimate the temperature?
 
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  • #2
Use the adiabatic condition [itex]\left(PV^\gamma = \textit{constant}\right)[/itex] to find the pressure in the cylinder after the volume has been reduced to 1/20 of its initial volume.

Next, use the ideal gas law [itex]\left(PV = nRT\right)[/itex] to calculate the temperature.

- Warren
 
  • #3
chroot, how do you know it's adiabatic? Is this an approximation? I don't see how heat is prevented from transfer to the cylinder wall.
 
  • #4
The key word is "quickly." Given that the compression happens quickly, not enough time is available for significant heat transfer to occur.

- Warren
 
  • #5
Thanks chroot. That's exactly the kind of clarification I was looking for, and it makes sense to me now.
 

1. How do scientists estimate temperature using an equation?

Scientists use an equation called the ideal gas law to estimate temperature. This equation relates the pressure, volume, and temperature of a gas and can be used to calculate the temperature of a gas sample.

2. What is the ideal gas law equation?

The ideal gas law equation is PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is the temperature in Kelvin.

3. Can the ideal gas law be used to estimate temperature in any situation?

No, the ideal gas law is only applicable to ideal gases, which have no intermolecular forces and occupy negligible volume compared to their container. Real gases deviate from ideal behavior at high pressures and low temperatures.

4. How accurate is the ideal gas law in estimating temperature?

The ideal gas law is accurate under certain conditions, but it does not account for factors such as the size of gas molecules and intermolecular forces. As a result, the ideal gas law may not give precise results for real gases, especially at high pressures and low temperatures.

5. Are there other equations that can be used to estimate temperature besides the ideal gas law?

Yes, there are many other equations and methods that can be used to estimate temperature, depending on the specific situation. Some examples include the Stefan-Boltzmann law for blackbody radiation, the Clausius-Clapeyron equation for phase transitions, and the Boltzmann distribution for molecular energies.

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