1. Design &Types of Steam Turbines
Prof. Osama El Masry

2. Design Characteristics for a Steam Turbine
Custom design
Thermal output
Fuel flexibility
Reliability and life
Size range
Emissions

3. Performance and Efficiency Enhancements
Electrical Efficiency
Thermodynamic Efficiency
Efficiency Enhancements

4. Condensing Turbine
The condensing turbine processes result in maximum power and electrical generation efficiency from the steam supply and boiler fuel
Inlet pressure is relatively high
and exhaust pressure is
largely reduced
The power output of condensing
turbines is sensitive to
ambient conditions

5. Condensing Turbine
Increasing condensation temp. from 38 oC to 45°C, gives 6.5% less power output
When condensation temp. is reduced to 27°C the power output is increased by 9.5%

6. Example 5.1
In a condensing turbine cycle, the turbine generates 3.5 MW of Electric power with inlet steam at 27 bar & 71oC of superheat, the turbine efficiency is 75%, and the condenser pressure is 0.07 bar. The plant has also a separate low-pressure boiler, which generates saturated steam at 2.7 bar from feed water at 130oC and the boiler provides the heating capacity of 70x103 MJ/h. Calculate the steam mass flow rate and heat added in the two boilers if the boiler efficiency is 84% in both boilers.

7. Solution
For the condensing turbine E=3.5 x 1000=ms1(h1-h2)ηT h1= 3000 kJ/kg h2=2o65 kJ/kg ms1= 5 kg/s Q1= ms1(h1-h`pc)/ηb=5( )/0.84=16.88 MW For the heating boiler H=70 x 106/3600== ms2 (h3-h4) = ms2( x 4.187) ms2=8.94kg/s Q2= ms2(h3-h4)/ηb=70 x 106/3600 x 0.84=23.1 MW mtotal=13.94 kg/s Qtotal=40 MW

8. Back-pressure Turbine
The term “back-pressure” refers to turbines that exhaust steam at atmospheric pressures and above
A back-pressure turbine exhausts its entire flow
of steam to the
industrial or facility
process

9. Back-pressure Turbine
Combined Heat and Power is the main application
For industrial plants: H.P steam flows through the turbine to a low pressure steam tank and then desuperheated (by small jet) to dry and saturated condition and then allowed to
flow to the process where
it gives off its latent heat

11. Example 5.2
For the plant in example 5.1 if a back pressure turbine is used under the same inlet steam conditions, exit pressure is 1.4 bar and turbine efficiency is 75%. If the exhaust steam is used in the heating process and heating capacity needed is 70x103 MJ/h, calculate the steam mass flow rate, the power generated and the heat added in the boiler. Assume that the boiler efficiency is 84%, and the heating condensate is returned back to the boiler as saturated liquid.

12. h1=3000kJ/kg h2s=2333kJ/kg h2=2500kJ/kg h3=458.5kJ/kg
H=70 x 106/3600== ms (h2 –h3) =
ms= 9.52 kg/s
Power(E)= ms(h1-h2)=4760 kW
Neglecting the pump power
Qadd= ms(h1-h3)/ηb
=24195 kW

13. Extraction Turbine
The extraction turbine has opening(s) in its casing for extraction of a portion of the steam at some intermediate pressure before condensing the remaining steam

14. Extraction Turbine
At steam extraction locations there are usually steam flow control valves that control system flow rates and cost.

15. Mixed Pressure Turbine
used in conjunction with a multistage turbine in cases where the exhaust is not sufficient to develop the power required

16. Mixed Pressure Turbine
A heat accumulator in its simple form, is a cylindrical vessel where exhaust steam is led to submerged orifices,
The steam condenses by direct contact with water. The water absorbs its latent heat, thus its sensible heat increases, and the pressure of steam above it rises.
When the turbine consumes more steam than is coming, there is a slight reduction of pressure in the steam space which causes the water to evaporate, thus causing the pressure to fall gradually and the water looses sensible heat so on……..
The first operation is called storage period while the second is called the generation period. The steam consumption and the pressure of the steam in the accumulator is shown next

17. Mixed Pressure Turbine

18. Mixed Pressure Turbine
-Case (1) Power from H.P. turbine work only,
Power1 = m x Δ hHP
where m is the steam consumption in H.P. turbine work only
-Case (2) Power from L.P. turbine work only
Power2 = m1 x Δ hLP
Where m1 is the steam consumption in L.P. turbine work only

19. Case (3) Power from both L.P & H.P. turbine work
h3M(m+m1) =m h2+m1h3