A fire pump mounted on the fire engine is driven by a car engine. The engine has plurality of combustion chambers and converts the reciprocating motion of the pistons into rotational motion while shifting the combustion timing of each combustion chambers. When the force generated by the combustion is converted into torque, periodic torque fluctuation is generated. Torque fluctuation finally generates the rotation fluctuation. We analyzed pump performance by the rotation with the sinusoidal fluctuation for the impeller. From the viewpoint of torque and total head, each variable fluctuated in the same phase, but it was confirmed that there was a difference in fluctuation range. With engine rotation fluctuation given to the pump, we verify the pressure characteristics and efficiency on the outlet side change by CFD. In this paper, therefore, we report the results of CFD on pump output characteristics when periodic rotational fluctuations occur due to unsteady torque characteristics of the engine.
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