Experimental study on the gas engine speed control and heating performance of a gas Engine-driven heat pump

•An engine speed control model is established and identified by step experiments.•A gas engine speed control strategy is proposed and applied to control the engine speed of GEHPs.•The engine speed controller has a good performance in terms of settling time and overshoot. The gas engine-driven heat pump (GEHP) system is an energy saving device for heating, cooling or hot water supply. As the power source of the system, the performance of gas engine speed control directly has a significant impact on the system stability and efficient operation. However, gas engine is typically a nonlinear dynamical system and easily disturbed by the load fluctuation, which increases the difficulty of control of gas engine speed. Therefore, a gas engine speed control strategy is proposed for a GEHP system. Aiming at achieving this objective, a test facility is developed and an engine speed controller is designed according to the characteristics of the gas engine and the GEHP system. Then the engine speed controller is applied to the GEHP system and experiments are performed under different conditions: engine speed setting control and anti-disturbance control. The experimental results show that it costs less than 40 s to make the engine speed steady without overshoot when engine speed setting changes. When the disturbances of superheat change occur, the error (accuracy) of the engine speed is controlled within ± 50 rpm. The engine speed control strategy can not only guarantee the stable operation but also satisfy the capacity adjustment performance of the GEHP system. Finally, performance characteristics of the GEHP are characterized by heating capacity and primary energy ratio (PER). The results indicate that engine speed is an important factor which influences the performance of the GEHP. The heating capacity increases with the increase of engine rotational speed, while PER of the GEHP decreases. In terms of energy saving, the GEHP system should operate at lower engine speed in the case of satisfying the system load.