Definition
A ring-shaped opening, typically formed by the gap between two concentric circular parts, used to meter or direct the flow of a fluid such as fuel, oil, or air through an engine component.
Plain English
A round, donut-shaped gap that fluid passes through. Instead of a single round hole, the opening is the space between an inner circle and an outer circle.
Context Anchor
Seen in aircraft engine maintenance when describing fuel, oil, or air passages inside powerplant components.
Derivation
From Latin annulus, meaning 'little ring,' and orificium, meaning 'an opening' or 'mouth.' Together they describe a ring-shaped opening — exactly what the part is.
Why Pilots Care
If an annular orifice is blocked, worn, or the wrong size, the engine component may not get the correct flow of air, fuel, or oil.
Analogy
Picture the gap between two stacked drinking glasses of slightly different sizes — fluid flowing down between the outer glass and the inner glass passes through an annular orifice.
Intuition Check
Do not picture a simple round hole. An annular orifice is the ring-shaped opening around a center part.
Example Sentence 1
Fuel sprays out of the nozzle through an annular orifice, producing a cone-shaped pattern that mixes well with the incoming air.
Example Sentence 2
Fuel is metered through the annular orifice before it mixes with air in the venturi.