Chapter 4 - Ideal and Real Gases

Chapter 4 - Ideal and Real Gases - Chapter 4 - Ideal Gases...

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Chapter 4 - Ideal Gases The performance of an aircraft engine depends primarily on the density, pressure, viscosity, and temperature of the atmosphere in which it operates. We will first discuss ideal gases. An ideal gas is one that obeys the ideal gas equation . Under normal atmospheric conditions, many gases, including air, can be modeled as an ideal gas. At very low temperatures and high pressures, the behavior of a gas will depart from the ideal. Real gases do not obey the ideal gas law, although with just slight modifications, we can create a mathematical model to describe real gases. What makes the gas behave non-ideally? One almost trivial answer is that real gases liquefy if the temperature becomes very low, whereas ideal gases do not change their fundamental behavior however low the temperature. In our discussion of propulsion, the temperature and pressure ranges of our gas allow us to treat the gas as ideal. The density of a gas is the amount of mass in a certain volume and is expressed as mass per unit volume . We express density in the SI system as kilograms per cubic meter (kg/ m 3 ) . At sea level, the density is approximately 1.225 kg/m 3 . Typical units in the English system are slugs per cubic feet or slugs per cubic inch . At sea level, there are about 2.38 x 10 -3 slugs per cubic foot. The actual value depends on local atmospheric conditions. Viscosity is a property that describes the resistance of a fluid to flow.
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Chapter 4 - Ideal and Real Gases - Chapter 4 - Ideal Gases...

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