Final answer:
The thrust of a turbofan or turbojet is measured by the rate of mass flow combined with the exhaust velocity, reflecting the engine's power to propel an aircraft by accelerating air rearward.
Step-by-step explanation:
The thrust rating of a turbofan or turbojet engine is measured based on the momentum change of the air and fuel mixture passing through the engine. The basic principle involves Newton's third law, which states that for every action there is an equal and opposite reaction. So, thrust is produced by accelerating a mass of air rearward, which results in an equal force pushing the engine forward. The thrust F can be described mathematically by the equation F = (Am/At)×ve, where Am/At is the rate at which mass m is ejected (mass flow rate), and ve is the velocity at which the mass is ejected.
To measure this in practical terms, engineers can conduct tests with the engine mounted in a stationary test rig where the force it exerts can be measured directly. For a real-world example, the GE90-110B1 engine used in Boeing 777 aircrafts can produce a thrust ranging between 330 and 510 kN. This specification reflects the engine's capacity to accelerate air and fuel to create a powerful jet of exhaust gases, which propels the aircraft. The measurement of thrust is critical for ensuring that the engine provides sufficient power for various phases of flight, including takeoff, climbing, cruising, and landing.