Fuel Valve

Description

The Fuel Valve controls fuel flow between connected components in a spacecraft propulsion system. It has two physical ports—inlet and outlet—and actuates between closed and fully open positions at a configurable angular velocity. The valve supports cycling operations commonly used to clear impurity buildup in the mechanism. Flow through the valve scales with the current open fraction and is limited by a maximum flow rate.

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Example Use Cases

• Propellant Isolation: Control fuel flow from tanks to thrusters for safe engine shutdown.
• Tank Selection: Switch between primary and backup propellant tanks using isolation valves.
• Flow Regulation: Throttle fuel delivery by commanding partial valve positions.
• Valve Cycling: Execute rapid open-close sequences to clear contamination buildup.

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Module Implementation

Valve Position

The valve position ranges from 0 (fully closed) to 1 (fully open). The actual position actuates toward the commanded position at the configured angular velocity:

$$\Delta p=\frac{\omega }{\pi /2}\cdot \Delta t$$

where $\omega$ is the actuation angular velocity in rad/s, and the valve mechanism travels through a $\pi /2$ radian (90°) arc from closed to fully open. A maximum angular velocity of $\pi /2$ rad/s allows the valve to traverse its full range in one second.

Flow Rate

The effective flow rate through the valve depends on the current position and maximum flow rate:

$${\dot{m}}_{\text{eff}}=p\cdot {\dot{m}}_{\text{max}}$$

where $p$ is the current percent open and ${\dot{m}}_{\text{max}}$ is the valve’s rated flow capacity.

Network Connections

The valve exposes inlet (+Z) and outlet (-Z) ports for connecting to the fuel network:

Port	Direction	Valid Connections
Inlet	Upstream	Fuel Source, Consumer, Pump (Downstream), Interconnect
Outlet	Downstream	Fuel Source, Consumer, Pump (Upstream), Interconnect

Both ports support multiple simultaneous connections for parallel flow configurations.

Valve Cycling

Cycling rapidly alternates the valve between open and closed positions to clear impurity buildup. Each cycle consists of one complete open-close sequence at a specified frequency:

$$T_{\text{half}}=\frac{1}{2f}$$

where $f$ is the cycling frequency in Hz and $T_{\text{half}}$ is the duration of each opening or closing phase. Cycling can run continuously or for a specified number of cycles.

Range of Motion Limits

The valve’s range of motion is bounded by minimum and maximum percent open values. Error models can modify these limits to simulate degraded performance, such as a valve becoming partially stuck due to contamination or mechanical wear.

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Assumptions/Limitations

• The valve actuates at constant angular velocity; acceleration and deceleration transients are not modeled.
• Flow scales linearly with position; nonlinear flow characteristics are not represented.
• Cycling commands the valve to its full range limits; partial-stroke cycling is not supported.
• The valve does not model pressure drop, cavitation, or fluid hammer effects.
• Bidirectional mode must be explicitly enabled; default operation is inlet-to-outlet only.
• Cumulative transferred mass is tracked from creation and is not reset automatically.