How does indicated power differ from brake power in an internal combustion engine?

Explanation:

Indicated Power (IP):

• Indicated power refers to the total power generated within the engine’s cylinders as a result of the combustion process. It is calculated based on the pressures exerted by the combustion gases on the piston during the power stroke. This power is theoretical in nature and does not account for the losses incurred due to friction and other mechanical inefficiencies.

The formula for indicated power is as follows:

IP = (P_m × L × A × N × K) / 60

Where:

• P_m: Mean effective pressure in the cylinder (N/m²)
• L: Stroke length (m)
• A: Area of the piston (m²)
• N: Engine speed (RPM)
• K: Number of power strokes per revolution (for a four-stroke engine, K = 0.5)

Indicated power is derived from the pressure-volume (P-V) diagram of the engine and represents the gross power developed by the engine before any losses are considered.

Brake Power (BP):

• Brake power, on the other hand, is the net useful power available at the engine’s output shaft (crankshaft). It is the power that can be harnessed for performing external work, such as driving a vehicle or running machinery. Brake power accounts for mechanical losses due to friction, heat dissipation, and other factors within the engine.

Brake power is measured using a dynamometer, which applies a controlled load to the engine and measures the torque and rotational speed. The formula for brake power is:

BP = (2 × π × N × T) / 60

Where:

• N: Engine speed (RPM)
• T: Torque applied (Nm)

Brake power represents the actual, usable output of the engine after accounting for internal losses.

Correct Option Analysis:

The correct option is:

Option 3: Indicated power is derived from combustion chamber pressures, whereas brake power is the net output at the crankshaft after mechanical losses.

This option accurately describes the distinction between indicated power and brake power:

• Indicated power is determined based on the pressure generated in the combustion chambers during the power stroke. It is a theoretical measure of the engine’s gross power output.
• Brake power, in contrast, is the practical, net power output available at the crankshaft. It accounts for losses due to friction, heat, and other inefficiencies within the engine.

Thus, indicated power represents the engine’s potential power output, while brake power indicates the actual power that can be utilized for external applications. The difference between the two is attributed to the mechanical losses within the engine.