Needle Valve Actuator
May - June 2024
OBJECTIVE:
The objective of this project was to design and implement an electronically actuated needle valve system to replace traditional pressure regulators in the AerospaceNU rocket engine test stand feed system. This approach was intended to increase flow capacity, reduce weight, and enable PID-controlled pressurant flow while demonstrating feasibility for future flight-weight liquid rocket applications.
PROCESS:
The design began by calculating the required flow coefficient using upstream and downstream pressures and the nitrogen volumetric flow rate at standard temperature and pressure. To maintain flexibility for future, higher-flow engine testing, I selected a needle valve with a higher than necessary flow coefficient. Because the valve needed to seal and reopen under high pressure, the breakaway torque was measured using a precision torque wrench to determine the required actuation torque. Using these results, I selected a stepper motor with sufficient torque margin and adequate positional control (400 steps / rotation).
I then focused on the mechanical integration between the motor and valve. I designed a 3D-printed actuator mount to rigidly support the stepper motor while minimizing backlash and allowing vertical compliance to accommodate valve stem translation during operation. I also designed a custom coupler to transmit torque between the motor shaft and valve stem while maintaining alignment under load. After printing the components, I assembled the actuator and used through-bolts to clamp the assembly directly to the valve body, creating a compact and serviceable unit suitable for repeated test stand use.
To support hardware testing, I wrote basic C++ control code for an Arduino and stepper driver that allowed manual positioning of the valve using a potentiometer input. This enabled repeatable functional testing of the actuator system across the full range of valve motion.
RESULTS:
The final result was an electronically actuated needle valve assembly capable of reliable sealing and reopening under high-pressure conditions. The actuator mount minimized play while allowing axial motion of the valve stem during rotation, and the custom coupler ensured consistent torque transmission without introducing misalignment. The assembled unit successfully demonstrated controlled valve positioning on the test stand, validating the mechanical actuator design and providing a foundation for future closed-loop control and flight-weight development.
