ESDU 90025

Performance of conical diffusers in subsonic compressible flow.

Abstract:

ESDU 90025 gives performance maps for straight axis diffusers with sharp transition from an inlet pipe with naturally-developing flow. They apply for an inlet Reynolds number (based on pipe diameter) of one million. They plot static pressure recovery against diffuser area ratio (inlet/outlet) and length ratio (length/inlet radius) and each applies to a specific value of inlet Mach number (from 0.2 to 0.8) and a limited range of inlet pipe length/diameter ratios (from 0 to 35.5). Shown on each map are curves of optimum performance for either given length ratio or given area ratio. The maps, whose use is illustrated by two worked examples, can be applied to determine the performance of a given design or to design an optimum diffuser. An approximate method is suggested for deriving the total head loss from the static pressure recovery. Various other influences on diffuser performance are discussed and illustrated with sketches for specific cases. They include Reynolds number variation, inlet turbulence intensity, inlet velocity profile shape, upstream shock wave/boundary layer interaction, the approach to choking Mach number, fairing the inlet/diffuser junction, and fitting a tailpipe.

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Details:

Data Item ESDU 90025
Format:	PDF with interactive graphs
Status:	Amendment (A), 01 Mar 2007 Published in Release 2007-02
Previous Releases:	ESDU 90025
ISBN:	978 0 85679 751 4

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This Data Item contains 34 interactive graph(s) as listed below.

Graph	Title
Figure 1	Variation of diffuser inlet blockage ratio with upstream pipe length
Figure 10 - Part 1	Performance map for M‾₁ = 0.4 and L_u/D₁ = 30 - 35.5
Figure 10 - Part 2	Performance map for M‾₁ = 0.4 and L_u/D₁ = 30 - 35.5
Figure 11 - Part 1	Performance map for M‾₁ = 0.6 and L_u/D₁ = 0 - 1.0
Figure 11 - Part 2	Performance map for M‾₁ = 0.6 and L_u/D₁ = 0 - 1.0
Figure 12 - Part 1	Performance map for M‾₁ = 0.6 and L_u/D₁ = 9 - 10.5
Figure 12 - Part 2	Performance map for M‾₁ = 0.6 and L_u/D₁ = 9 - 10.5
Figure 13 - Part 1	Performance map for M‾₁ = 0.6 and L_u/D₁ = 20
Figure 13 - Part 2	Performance map for M‾₁ = 0.6 and L_u/D₁ = 20
Figure 14 - Part 1	Performance map for M‾₁ = 0.6 and L_u/D₁ = 30 - 35.5
Figure 14 - Part 2	Performance map for M‾₁ = 0.6 and L_u/D₁ = 30 - 35.5
Figure 15 - Part 1	Performance map for M‾₁ = 0.8 and L_u/D₁ = 0 - 1.0
Figure 15 - Part 2	Performance map for M‾₁ = 0.8 and L_u/D₁ = 0 - 1.0
Figure 16 - Part 1	Performance map for M‾₁ = 0.8 and L_u/D₁ = 9 - 10.5
Figure 16 - Part 2	Performance map for M‾₁ = 0.8 and L_u/D₁ = 9 - 10.5
Figure 17 - Part 1	Performance map for M‾₁ = 0.8 and L_u/D₁ = 20
Figure 17 - Part 2	Performance map for M‾₁ = 0.8 and L_u/D₁ = 20
Figure 18 - Part 1	Performance map for M‾₁ = 0.8 and L_u/D₁ = 30 - 35.5
Figure 18 - Part 2	Performance map for M‾₁ = 0.8 and L_u/D₁ = 30 - 35.5
Figure 2	Variation of diffuser inlet turbulence parameter with upstream pipe length (Derivation 14)
Figure 3 - Part 1	Performance map for M‾₁ = 0.2 and L_u/D₁ = 0 - 1.0
Figure 3 - Part 2	Performance map for M‾₁ = 0.2 and L_u/D₁ = 0 – 1.0
Figure 4 - Part 1	Performance map for M‾₁ = 0.2 and L_u/D₁ = 9 - 10.5
Figure 4 - Part 2	Performance map for M‾₁ = 0.2 and L_u/D₁ = 9 - 10.5
Figure 5 - Part 1	Performance map for M‾₁ = 0.2 and L_u/D₁ = 20
Figure 5 - Part 2	Performance map for M‾₁ = 0.2 and L_u/D₁ = 20
Figure 6 - Part 1	Performance map for M‾₁ = 0.2 and L_u/D₁ = 30 - 35.5
Figure 6 - Part 2	Performance map for M‾₁ = 0.2 and L_u/D₁ = 30 - 35.5
Figure 7 - Part 1	Performance map for M‾₁ = 0.4 and L_u/D₁ = 0 - 1.0
Figure 7 - Part 2	Performance map for M‾₁ = 0.4 and L_u/D₁ = 0 - 1.0
Figure 8 - Part 1	Performance map for M‾₁ = 0.4 and L_u/D₁ = 9 - 10.5
Figure 8 - Part 2	Performance map for M‾₁ = 0.4 and L_u/D₁ = 9 - 10.5
Figure 9 - Part 1	Performance map for M‾₁ = 0.4 and L_u/D₁ = 20
Figure 9 - Part 2	Performance map for M‾₁ = 0.4 and L_u/D₁ = 20