Steam turbine rotor cascade

Application Challenge 6-12 © copyright ERCOFTAC 2004

Description

Introduction

The results of experimental investigation of fluid flow in blade cascades at transonic flow regimes are invaluable for improvements of turbine designs and for verification of CFD codes. Higher efficiency and operational reliability of turbines and compressors can be reach by coupling of experimental and numerical modelling of flow in cascades.

The transonic flow in a steam turbine rotor cascade was selected for the application challenge. The investigation of the SE 1050 blade cascade includes experimental test data based on interferometric pictures of fluid flow and numerical simulation using models of inviscid flow (home-made software) and of viscous flow (FLUENT code).

As the testcase, the measurement for the inlet angle β₁ = 70.7 deg and the exit isentropic Mach numbers 1.198 was chosen. The basic series of measurements was made for the inlet angle β₁ = 70.7 deg (incidence i = 0 deg) with the exit isentropic Mach numbers changed in the range (0.489, 1.387). Some additional experiments were carried out for extreme values of incidence covering the range from very small loading to overloading conditions.

Relevance to Industrial Sector

The blade cascades belong to most important elements in turbomachinery and their design is crucial for the efficiency and operational reliability of turbines and compressors. This is valid especially for turbines of large output. The chosen profile cascade called SE 1050 was designed for the last stage of a SKODA steam turbine with the blade length 1085 mm and a nominal speed of 3000 rpm. The SE 1050 profile is a section of a rotor blade at the distance 320 mm from the root. The cascade operated in the transonic regime was chosen as the testcase suitable for testing of numerical methods and verification of experimental methods as well.

Design or Assessment Parameters

Following parameters are used as crucial for the appraisal of CFD calculations:

isolines of the Mach number and/or density in the flow field of the blade cascade

pressure and Mach number distribution on the profile surface

energy losses

exit flow angle

Flow Domain Geometry

Fig.1 Scheme of the SE 1050 blade cascade

The scheme of the cascade is given in Fig.1. The basic data of the cascade and coordinates of the profile SE 1050 are given in Tables 1 and 2.

Table 1 Basic data of the SE 1050 cascade
chord b	100 mm
blade span	160 mm
pitch t	55.12 mm
stagger angle ?	37.11 deg
number of blades	8
inlet angle ß₁	70.7 deg
incidence angle i	0 deg

x (mm)	y (mm)	x (mm)	y (mm)
99.999282	0.352723	3.464884	1.225294
99.926424	0.59935	4.753891	2.022511
99.521423	0.815971	6.139122	2.825664
96.001435	2.136338	7.530131	3.572762
92.481447	3.456706	8.921242	4.265414
88.961459	4.777074	10.312443	4.909197
85.441471	6.087441	11.703727	5.508339
81.921483	7.417808	13.095083	6.07044
78.401495	8.738176	14.486504	6.596632
74.881508	10.058544	15.877984	7.091291
71.361520	11.378911	17.269517	7.55728
67.841532	12.699278	18.661100	7.996743
64.321544	14.019646	20.052729	8.411307
60.801556	15.340013	21.444403	8.802027
57.281568	16.660381	22.836120	9.169491
53.761581	17.980748	24.264540	9.520354
50.507366	19.201423	26.037267	9.908534
49.152583	19.702386	28.440150	10.37689
47.520269	20.261961	31.187419	10.839571
45.296321	20.902956	33.971529	11.212068
42.293512	21.587151	36.755824	11.484898
38.685177	22.217304	39.540299	11.661747
35.342716	22.590225	42.324939	11.750299
32.000704	22.723076	45.109726	11.759488
28.683738	22.598581	47.894645	11.697599
25.611367	22.285806	50.679701	11.562528
23.652286	21.966315	53.464905	11.348665
21.977517	21.592001	56.250256	11.05505
20.307477	21.139681	59.035747	10.687274
18.498444	20.555481	61.821342	10.262674
16.828738	19.924468	64.607030	9.789283
15.159193	19.207027	67.392813	9.261068
13.489828	18.392915	70.178720	8.672954
11.681632	17.359536	72.964738	8.021636
10.012817	16.250972	75.750873	7.306083
8.344302	14.981078	78.537134	6.526853
6.676158	13.512223	81.323504	5.686874
4.869618	11.59038	84.109980	4.790667
3.203006	9.300038	86.896902	3.844904
1.600882	6.343956	89.698387	2.853376
0.444430	3.346941	92.489059	1.837071
0.000239	1.258739	94.522906	1.084837
0.053144	0.876155	95.303546	0.812817
0.221685	0.528644	96.096132	0.577871
0.489364	0.250224	96.898907	0.380521
0.829978	0.068148	97.710087	0.221207
1.210186	0.000239	98.527871	0.100282
1.592770	0.053144	99.600827	0.000718
1.946786	0.226249	99.791554	0.039377
2.440690	0.560226	99.937399	0.16822

Flow Physics and Fluid Dynamics Data

The compressible adiabatic flow in the blade cascade is mostly laminar with the transition to turbulence in the exit part of the cascade. The fluid flow is accelerated in the blade passage. Air is considered as a perfect gas. The governing parameters are as follows: