At some point in the combustion cycle of an engine, the temperature of a combusted air-fuel mixture is 582 degrees Celsius. Given that the pressure in the mixture is 6.2 bar, determine the density of the mixture (in kilogram per cubic metre). Assume the gas constant R is equal to 287.00 J/(kgK).

1 answer

To determine the density of the combusted air-fuel mixture, we can use the ideal gas law, which states:

\[ PV = nRT \]

Rearranging this for density (\(\rho\)), we can express it in terms of pressure (\(P\)), the gas constant (\(R\)), and temperature (\(T\)):

\[ \rho = \frac{P}{RT} \]

Step 1: Convert the temperature from Celsius to Kelvin

The temperature in Kelvin (\(T\)) is given by:

\[ T(K) = T(°C) + 273.15 \]

Substituting \(T = 582\) °C:

\[ T(K) = 582 + 273.15 = 855.15 , \text{K} \]

Step 2: Convert the pressure from bar to Pascals

Pressure in pascals is required for the calculation. Since \(1 , \text{bar} = 100,000 , \text{Pa}\):

\[ P = 6.2 , \text{bar} = 6.2 \times 100,000 , \text{Pa} = 620,000 , \text{Pa} \]

Step 3: Substitute values into the density equation

Now we can substitute \(P\), \(R\), and \(T\) into the density equation:

\[ \rho = \frac{P}{RT} \]

Substituting in:
\(P = 620,000 , \text{Pa}\),
\(R = 287.00 , \text{J/(kgK)}\),
\(T = 855.15 , \text{K}\)

\[ \rho = \frac{620,000}{287.00 \times 855.15} \]

Calculating the denominator:

\[ 287.00 \times 855.15 \approx 245,792.55 \]

Now, calculating the density \(\rho\):

\[ \rho = \frac{620,000}{245,792.55} \approx 2.52 , \text{kg/m}^3 \]

Final Answer

The density of the combusted air-fuel mixture is approximately:

\[ \mathbf{2.52 , kg/m^3} \]