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

(MSc thesis)

Erick Dick (2015). Fundamentals of

Turbomachines

S.L Dixon (1998). Fluid mechanics and

Thermodynamics of fluid machines, 5th edition

Bibliography

No

To sum up,

the following flowchart is supposed to be

followed

2.4

Procedure

Mx1 is the axial

component of entry Mach number.

P denotes the passage

throat before the entry

Where

Introduced for

the factors; maximum thickness to chord (t/c)

and the Axial Velocity Density Ratio, to apply a more advanced correlation as

follows

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

factor

It’s defined as

follows

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.

·

End

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

Energy

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