Subtopic: Calculation of power, torque, fuel consumption, heat load and power losses
Question Statement:
A four-stroke 3-cylinder tractor diesel engine has a total displacement volume of $V_d = 2.4\text{ L}$ ($2.4 \times 10^{-3}\text{ m}^3$). At an engine speed of $N = 2100\text{ rpm}$, the engine develops a brake power of $BP = 35.0\text{ kW}$. The brake mean effective pressure ($bmep$) of the engine in $\text{kPa}$ is ________ (round off to 1 decimal place).
Answer Key:
833.3
Step-by-Step Solution & Explanation
For a four-stroke multi-cylinder engine, brake power is given by:
$BP = \frac{bmep \cdot V_d \cdot N}{120 \times 1000}$
Where $bmep$ is in $\text{kPa}$, $V_d$ is total displacement in $\text{m}^3$, and $N$ is engine $\text{rpm}$:
$bmep = \frac{BP \times 120 \times 1000}{V_d \times N}$
$bmep = \frac{35.0 \times 120,000}{(2.4 \times 10^{-3}) \times 2100} = \frac{4,200,000}{5.04} \approx 833.33\text{ kPa} \approx 833.3\text{ kPa}$