[Julian121]

I am running a simulation at two mass flow rates 1.92 and 1.52 kg/s.

At 1.92 kg/s, the blade passing frequency (1900 Hz) and its harmonics is seen.

At 1.52 kg/s, there exists a range of frequencies and a peak at 805 Hz which has the most power spectral density.

From experimental data, I know that 1.52 kg/s is close to rotating stall.

From the literature I understand that a stall cell must have a low frequency of 20%-70% of rotor frequency which is 50 Hz in my case. So, the rotating stall should have a frequency of 10 Hz to 35 Hz in my case.

At 1.52 kg/s the separation region has extended to rotor leading edge plane and the flow to the passage has been fully blocked.

Could that 805 Hz be the frequency of the recirculating flow upstream of the rotor which has not turned into a stall cell yet?

What is the cause of 805 Hz?

[Julian121]

I still have difficulty in explaining the peak frequency at 805 Hz.

As I said in my previous post, a stall cell should have a lower frequency than rotational frequency of the rotor (50 Hz). So, that 805 Hz is not the stall cell frequency.

However, I have discoverd that the peak at 805.912231 Hz and the rest unknown frequencies at 1.52 kg/s are an integer multiplier of the base 24.4215832 Hz frequency which has been shown by a black arrow.

Could someone please explain its meaning?

[AtoHM]

How many blades are there on each row?

[Julian121]

Originally Posted by AtoHM

How many blades are there on each row?

There are 34, 38, 37 blades in IGV, Rotor and Stator respectively.

In addition to them, there are 120 vanes in the casing treatment.

The probe which I have used to analyse the frequency has been placed in the casing treatment.

[Julian121]

The peak at 805.912231 Hz is not an integer multiplier of any blade row numbers but it is an integer multiplier (33x) of the 24.4215832 Hz (lowest frequency in the frequency spectrum).


Can the peak at 805.912231 Hz be a harmonic of 24.4215832 Hz frequency?