>
;.
reactivity rate is determined from the equation
,
is airtwist in the working wheel.of on the middle radius must be within limits of 0,2-0,35. verify calculations accuracy it is necessary to compute turbine stage work by the formula
.
obtained value differs more than on 3% from accepted at the beginning it is necessary to look for mistake in previous calculations.
Cinematic parameters determination on different turbine stage radiuses
plan calculation and construction (see pic. Xx) is done for chosen law of blade profiling across radius.
. X.x
approximate turbine stage calculations we can accept design sections diameters as average between diameters of inlet and output edge, ie
В
flow parameters calculation first of all law of blade profiling across radius are chosen. For that reactivity rate are determined at rate index value m = 1,0 () from the equation
.
, the law of circulation constancy is accepted, which provide high stage efficiency. In this case angle of nozzle diaphragm blade incidence is changed across blade height., Blades can be profiled by the law of, which allows to obtain same profiles across the blade height and simplifies blade manufacturing technology. Disadvantage of these blades is non-constant axial component of the jet velocity at the exit from the nozzle diaphragm. If value is obtained at index value m = 1,0, then assigning, index value m can be found by the formulas:
, if;
, if.
and on different radiuses in common case are calculated from the equations:
;
.
the law of profiling is accepted, then:
;.
the law of profiling is accepted, velocities and
are calculated from the equations (xx) and (xx) with index value. components of the jet velocity are determined by the formulas:
;
.
the law of profiling is accepted, then:
;.
the law of profiling is accepted, velocities and
are calculated from the equations (xx) and (xx) with index value.
Table 1cinematic parameters on different radiuses
Parameter and formulaSectionNotesleevemiddleperipheral , m , m/s , m/s , m/s , m/s , deg , m/s , m/s , deg < span align = "justify">, m/s , m/s , m/s , deg , deg , m/s , m/s , K , J/kg ,%
Appendix 1
THE EXAMPLE OF gas-dynamic CALCULATION OF THE axial turbine stage
The initial data for the axial turbine stage gas-dynamic calculation are gas parameters and geometrical dimensions at the entry to the turbine obtained during gas-dynamic calculation of the designed engine.main goals of the turbine stage gas -dynamic calculation are geometrical dimensions determination of the turbine stage, speed plans construction in three sections across the blade height.the engine gas-dynamic calculation following parameters are known:
В· gas pressure at the entry to the high-pressure turbine;
В· gas temperature at the entry to the high-pressure turbine;
В· mass gas flow rate;
В· HPT stage work;
В· circumferential velocity on the middle radius;
В· angle of the stream output from nozzle diaphragm;
В· external, middle and sleeve diameters at the entry to the working wheel,,;
В· jet velocity of gas at the exit from the nozzle diaphragm;
В· reduced velocity at the nozzle diaphragm exit;
В· pressure recovery coefficient in the nozzle diaphragm.
Section area at the entry to the HPT first stage working wheel was determined in the engine gas-dynamic calculation:
.
relative density and then;
. dimensions before the working wheel will be found on the basis of the next formulas:
В· blade height
;
В· external diameter
;
В· sleeve diameter
;
В· relative sleeve diameter
;
determine geomet...
