Niclas Falck (2008). Axial Flow Compressor Mean Line Design
(MSc thesis)

Erick Dick (2015). Fundamentals of

S.L Dixon (1998). Fluid mechanics and
Thermodynamics of fluid machines, 5th edition
























To sum up,
the following flowchart is supposed to be
















Mx1 is the axial
component of entry Mach number.

P denotes the passage
throat before the entry


Introduced for
the factors; maximum thickness to chord (t/c)
and the Axial Velocity Density Ratio, to apply a more advanced correlation as

2.3.2 Koch and Smith

 of diffusion
factor according to Lieblein

Figure 4 Loss coefficient as a function

By establishment of the velocity
gradient on the suction side, in conjunction with results from cascade testing,
Lieblein deduced the following formulae for both diffusion factor and
equivalent diffusion ratio

2.3.1 Lieblein 1957 approach

2.3 Approach methods to Diffusion ratio and Diffusion


It’s defined as

2.2.4 Total pressure
loss coefficient


It’s the ratio between the maximum velocity and the
outlet velocity

2.2.3 Diffusion ratio



To calculate the diffusion factor there are various
approaches to which we are going to expose just before the procedure section.


Figure 3
Velocity distribution



Diffusion factor relates the maximum velocity at the
suction side of the rotor airfoil and the
velocity at the trailing edge as follows

It’s a dimensionless parameter which somehow indicates
the amount of loss due to flow, tells us
what the possibility for the blade to stall, primarily on the suction surface
of the airfoil.

2.2.2 Diffusion factor

Diffusers have a limiting property than nozzles from a
fluid-mechanics point of view, that it
can’t exceed a certain diverging angle to avoid high-pressure
gradient which in
turn facilitates stall, and since the exit velocity decreases as the pressure
increases, De Haller number is defined. Accordingly, from practical analysis, it was found that a safe
value of De Haller number should not be less than 72%.

It’s defined as the ratio between exit and inlet
velocities relative to the rotor.

2.2.1 De
Haller number


2.2 Some
related parameters to compressor losses


We are going to get into further details concerning
these two types, and their related parameters, the objective is to reach more
realistic fluid properties at the rotor exit for our design, worth to be
mentioned it’s constant-mean-diameter based.


It generally
represents the dominant source of loss, occurs near the end walls rather than
blades’ surfaces. It’s classified from the secondary losses due to the secondary crossflow
established by the curved path of the blade.

wall loss


Stagnation pressure
loss takes place as a result of boundary layer growth on the blade surface

Profile loss

On the other hand, from the Fluid mechanics’ perspective, those losses are distributed among
two major loss types


Figure 1
loss aspects through blades


As well as any flow circumstances, fluid flow through
a cascade of axial flow compressor experiences losses which are physically
dependent on various parameters like Tip
clearance, Aspect ratio, Solidity, Mach number& Reynolds number.

2.1 Introduction


2. Axial flow compressor losses