characteristic is lower than k ¼ u=c 1 . This is because when the residual kinetic
energy loss decreases with the increase of rotational speed, other losses such as disk
friction blast loss and partial intake loss increase sharply with the increase of
rotational speed, partially offsetting the gains from reducing the residual kinetic
energy loss.
The best working point can be easily obtained by computer (Table 9.13,
Fig. 9.47). In this case, at N ¼ 97000 r=min, the efficiency of the turbine is the
highest. The losses at design point g e ¼ 27:7%, N e ¼ 5:88 kW are shown in
Table 9.14. Comparing Table 9.14 with Table 9.12, it can be seen that the residual
kinetic energy loss decreased from 389806:1 to 255932 J per kilogram of gas. The
friction blast loss increased from 6328:7 to 27226:0 J, and the partial intake loss
increased from 172423:0 to 278751 J. These two losses increased sharply with the
increase of rotational speed. But overall, the efficiency increased from 23:4% to
Fig. 9.46 Triangular vector distribution of airflow velocity at rotational speed 6000 r/min
Table 9.13 Variation of power with rotational speed of gas turbine in initial and final state of
working medium
N = 40000
N e = 3.767295
N = 100000
N e = 5.877799
N = 45000
N e = 4.112336
N = 105000
N e = 5.841069
N = 50000
N e = 4.428102
N = 110000
N e = 5.769031
N = 55000
N e = 4.714175
N = 115000
N e = 5.661011
N = 60000
N e = 4.970128
N = 120000
N e = 5.516279
N = 65000
N e = 5.195523
N = 125000
N e = 5.33405
N = 70000
N e = 5.38991
N = 130000
N e = 5.113459
N = 75000
N e = 5.552823
N = 135000
N e = 4.858552
N = 80000
N e = 5.683781
N = 140000
N e = 4.553248
N = 85000
N e = 5.782289
N = 145000
N e = 4.211325
N = 90000
N e = 5.847825
N = 150000
N e = 3.826358
N = 95000
N e = 5.879851
142
9 High-Temperature and High-Speed Gas Turbine Pump …