Method of evaluating aircraft engine components for compliance with flow requirements

A method of evaluating compliance of a component of an aircraft engine with flow requirements through apertures defined through the component, the method comprising:

• obtaining experimental data from experimental testing on a prototype of the component, the experimental testing including flowing a flow of a fluid through apertures of the prototype to obtain a coefficient of discharge (Cd) and an experimental mass flow rate through the apertures of the prototype, and including computing a reference nominal mass flow rate through digitized apertures of a digitized model of the prototype, including computing the coefficient of discharge with:
• C
• d
• =
• 4
• ⁢
• q
• rig
• ⁢
• D
• 4
• -
• d
• 4
• ϵπ
• ⁢
• D
• 2
• ⁢
• d
• 2
• ⁢
• 2
• ⁢
• Δ
• ⁢
• pp
• ,
• where qrig is an experimental mass flow rate from the experimental data, D is a diameter of a conduit feeding the flow to the apertures of the prototype during the experimental testing, d is a mean diameter of maximum diameters of cylinders able to fit in the apertures of the prototype, and e is an expansion coefficient calculated as follows:
• ϵ
• =
• 1
• -
• [
• (
• 0.351
• +
• 0.256
• β
• 4
• +
• 0.93
• β
• 8
• )
• ⁢
• (
• 1
• -
• γ
• ⁢
• p
• -
• Δ
• ⁢
• p
• p
• )
• ]
• where ρ is a pressure of the flow upstream of the apertures of the prototype, g is a specific heat ratio of the fluid, and b is a ratio of the mean diameter (d) to the diameter (D) of the conduit;
• obtaining a digitized model of a production model of the component, the digitized model including digitized apertures having geometrical data corresponding to that of apertures defined in the production model;
• computing a nominal mass flow rate through the digitized apertures of the digitized model of the production model using the geometrical data from the digitized model, flow parameters from the experimental data, and the coefficient of discharge from the experimental data, wherein the computing of the nominal mass flow rate includes:
• calculating a total flow passage area of the flow through the digitized apertures of the component from the digitized model;
• and
• computing the nominal mass flow rate with:
• qm=CdAtotal√{square root over (2ΔPρ)}
• where qm is the nominal mass flow rate, Cd is the coefficient of discharge obtained from the experimental data, Atotal is the total flow passage area obtained from the geometrical data of the digitized model, ρ is a density of the fluid flown through the apertures of the prototype during the experimental testing and taken upstream of the apertures of the prototype, and Dp is a pressure differential between pressures respectively upstream and downstream of the apertures of the prototype during the experimental testing;
• correcting the nominal mass flow rate of the digitized model using the experimental data to obtain a computed mass flow rate of the production model, the correcting of the nominal mass flow rate including multiplying the nominal mass flow rate by a ratio of the experimental mass flow rate to the reference nominal mass flow rate;
• and
• one of:
• installing the component in the aircraft engine upon determining that the computed mass flow rate is within a prescribed range of the flow requirements, and
• discarding the component upon determining that the computed mass flow rate is outside the prescribed range of the flow requirements.