Danfoss Motor – Motor: Thermal Efficiency, Propulsion Efficiency, Total Efficiency


The    Danfoss Motor     states that motor efficiency is the degree to which the motor utilizes the chemical energy of the propellant. When the motor is working, only a part of the heat energy contained in the fuel is converted into propulsion work, and the rest is lost in the form of heat or kinetic energy. motor efficiency is one of the indicators for evaluating motor performance. It is divided into thermal efficiency, propulsion efficiency and total efficiency.

  The efficiency of the solid rocket motor and the liquid rocket motor can be expressed by the ratio of the motor specific impulse to the propellant theoretical specific impulse under standard conditions, that is, the thrust generated by the unit flow of the propellant in the motor and the thrust generated by the theoretical heat of the unit flow. The ratio is expressed.

  Thermal efficiency

  The ratio of the thermal equivalent of the motor’s effective power to the heat content of the fuel consumed per unit time is called thermal efficiency (effective efficiency) and is used to assess the economics of the motor as a heat motor.

  The effective power of a piston aeromotor is shaft power; the jet motor’s effective power is equal to the kinetic energy increment of the airflow flowing through the motor unit per unit time. The thermal efficiency of turbojet motors is typically 24% to 30%.

  Propulsion efficiency

  The ratio of propulsion power to effective power of the motor (or propeller) is called propulsion efficiency (flight efficiency) to assess the effectiveness of the propeller. The propulsion efficiency of modern turbojet motors is generally 50% to 65%, and the propulsion efficiency of propeller propeller motors can reach 80% to 90%. [2]

  Total efficiency

  The ratio of the thermal equivalent of the propulsion power to the calorific value of the fuel consumed per unit time is the total efficiency, which is equal to the product of the thermal efficiency and the propulsion efficiency to assess the economics of the entire propulsion system, including the motor and propeller.