Figure 13. Static pressure distribution in 6-stage counter-rotating turbine

Aerodynamic design summary. Flow path calculations show integral results presented above and distribution of thermodynamic and kinematic parameters. Kinematic data investigation showed that Mach number is in subsonic ranges for both designed counter-rotating turbines. This means that we avoid additional shock losses and the necessity of applying special supersonic profiles. The main resume from summarizing the integral performances is that it’s possible to obtain more efficient counter-rotating flow path compared to traditional prototype with decreasing overall flow path length. Counter-rotating turbine capacity with 6 stages is increased up to 0.2 MW (1%) and total-to-total efficiency by 0.57% compared with 4-stage design and by 0.7% compared with initial design.

Off-design performance analysis. Initial axial turbine design and 4-stage counter-rotating design was chosen for preliminary comparing off-design performances with the initial ones. The analysis of off-design performances is the essential moment for every gas turbine, because they operate on off-design modes a significant part of their working time. Of course, the analysis of jet engine performances is incomplete without taking into account compressor maps, but in this article we will consider only turbine characteristics. Initial data for off-design performances calculations is given below. We assume that on partial modes the inlet pressure is lower due to nature of gas turbine engine cycle and for off-design calculations we select the next conventional inlet pressures.

Table 2

Turbines Integral Performances Comparison