MATLAB Answers

## How can i create efficiency isolines in a compressor map?

Asked by chapuisat

### chapuisat (view profile)

on 12 Sep 2018
Latest activity Edited by jonas

### jonas (view profile)

on 27 Sep 2018
Accepted Answer by jonas

### jonas (view profile)

I have mass flow, pressure ratio and efficiency values of about 30 points for 3 different rotation speed. I need to plot a compressor map as in the link by using these datas: https://www.uniplot.de/_images/metafiles-compressormap-80.png
I used interp1 with spline as method to create constant rotation speed lines (black lines in link above). And now i need to create efficiency isolines. I tried with different commands(for example; contour, griddata) but it did not work so far.
How can i create efficiency isolines?

jonas

### jonas (view profile)

on 12 Sep 2018
Could you upload the data?
chapuisat

### chapuisat (view profile)

on 12 Sep 2018
here you are

Sign in to comment.

## 2 Answers

Answer by jonas

### jonas (view profile)

on 12 Sep 2018
Accepted Answer

This is what I'm getting from the data you uploaded.
%%Load data
rpm{1}=xlsread('data_compressor_map.xlsx','A3:D10');
rpm{2}=xlsread('data_compressor_map.xlsx','A14:D25');
rpm{3}=xlsread('data_compressor_map.xlsx','A29:D33');
data=vertcat(rpm{:});
x=data(:,2)
y=data(:,4)
z=data(:,3)
%%Interpolate on grid
[X,Y]=meshgrid(min(x):.01:max(x),min(y):.01:max(y))
Z=griddata(x,y,z,X,Y)
%%Plot contour
contourf(X,Y,Z);hold on
%%Plot lines
plot([x(1:8);NaN;x(9:20);NaN;x(21:end)],[y(1:8);NaN;y(9:20);NaN;y(21:end)],'-k','linewidth',2)
cb=colorbar #### 0 Comments

Sign in to comment.

Answer by chapuisat

### chapuisat (view profile)

on 16 Sep 2018

Your answer helped me a lot! Thank you!
I think the map in the link below looks visually better with regards to efficiency area.
How can i change efficiency area as in the link below?
https://www.google.de/imgres?imgurl=x-raw-image%3A%2F%2F%2F405abd0c340c8e0e2f65d63f06a2eb7b6cc5c02a70d88a6f246ae45c93063160&imgrefurl=http%3A%2F%2Fpublications.lib.chalmers.se%2Frecords%2Ffulltext%2F196400%2F196400.pdf&docid=CpI22Qr1H9koZM&tbnid=Do4MNAy9WkBVRM%3A&vet=12ahUKEwiEmYOb6b_dAhVGkCwKHancCrU4ZBAzKBYwFnoECAEQFw..i&w=727&h=625&bih=754&biw=1536&q=compressor%20map%20contour&ved=2ahUKEwiEmYOb6b_dAhVGkCwKHancCrU4ZBAzKBYwFnoECAEQFw&iact=mrc&uact=8

jonas

### jonas (view profile)

on 16 Sep 2018
The link brought me to a master thesis pdf but I think I know which fig you are referring to. Basically its a surface plot with some added features.
There are a million things you can change to make the surface look more visually appealing. Here's an example of some things you could try:
%%Load data
rpm{1}=xlsread('data_compressor_map.xlsx','A3:D10');
rpm{2}=xlsread('data_compressor_map.xlsx','A14:D25');
rpm{3}=xlsread('data_compressor_map.xlsx','A29:D33');
data=vertcat(rpm{:});
x=data(:,2)
y=data(:,4)
z=data(:,3)
%%Interpolate on grid
[X,Y]=meshgrid(min(x):.002:max(x),min(y):.01:max(y));
Z=griddata(x,y,z,X,Y)
%%Tighten surface to avoid extrap
b = boundary(x,y,1)
in=inpolygon(X,Y,x(b),y(b));
Z(~in)=NaN;
%%Plot contour
h=pcolor(X,Y,Z);hold on
set(h,'linestyle','none')
%%Plot lines
plot([x(1:8);NaN;x(9:20);NaN;x(21:end)],[y(1:8);NaN;y(9:20);NaN;y(21:end)],'o-k','linewidth',1.5,'markerfacecolor','k')
cb=colorbar
%%Plot boundary
plot(x(b),y(b),'k','linewidth',1)
xlim([.2 1.8])
ylim([1 4.5])
set(gca,'layer','top') chapuisat

### chapuisat (view profile)

on 27 Sep 2018
How did you define x(b) and y(b)?
jonas

### jonas (view profile)

on 27 Sep 2018
If I remember correctly I used.
b = boundary(x,y,1);
That line got lost somehow, sorry.

Sign in to comment.