Temperature characteristics of flow force in the pre-stage of deflector jet servo valve across a wide temperature range

The deflector jet servo valve is a critical advanced control component in aerospace electro-hydraulic servo systems. The pre-stage, as the core of the valve, features extremely small structural dimensions and a complex jet pattern. Temperature variation significantly reduces the control accuracy of the servo valve. Current models fail to quantify temperature-dependent flow force mechanisms in pre-stages, a limitation to high temperature reliability studies. This paper examines the effect of temperature on the flow force of the pre-stage and establishes a theoretical temperature model for the deflector jet servo valve. To verify this model, a three-dimensional numerical temperature model of the pre-stage flow field is developed. The influence of temperature variation on the initial jet and deflector jet regions is analyzed, along with the combined effect of temperature and deflector displacement on pressure characteristics and flow force. Results show that as temperature increases, the pressure difference, pressure gain, and flow force in the left and right receiver chambers gradually increase—most rapidly within the range of –20 °C to 80 °C. Beyond 80 °C, the rate of increase declines. At constant temperature, these parameters also increase with deflector offset. An indirect method is proposed for measuring the pre-stage flow force, and a dedicated temperature characteristic test bench is constructed. Comparison of simulation, experimental, and theoretical results shows consistent trends, confirming the validity of the proposed temperature model for pre-stage flow force. The validated model enables thermal compensation strategies for aerospace actuators, significantly improving control accuracy under extreme thermal environments.