ABSTRACT
Besides the radial-flow gas turbine discussed in Chapter 7, two additional types of gas turbines are commonly used: the axial-flow impulse turbine and the axial-flow reaction turbine. The axial-flow impulse turbine is discussed in Chapters 2 and 9. As shown in Figure 2.10, the impulse turbine has a symmetrical blade profile; moreover, the velocity diagram shown in Figure 9.2 is drawn with W 2 = W 3 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_1.tif"/> ; i.e., there is no change in the magnitude of the relative velocity of the gas in the impulse rotor. Equation 2.49 for reaction, when applied to the impulse rotor with inlet at station 2 and exit at station 3, shows that R = 0 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_2.tif"/> ; i.e., the impulse turbine is a zero-reaction turbomachine. Equation 9.18 shows further that h 2 = h 3 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_3.tif"/> , which, for a perfect gas, means that T 2 = T 3 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_4.tif"/> and p 2 = p 3 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_5.tif"/> . In the stator or nozzle section, which is located upstream of the rotor, the gas expands and its velocity increases. Application of Equations 2.47 and 2.48 to the impulse rotor yields E = h 02 − h 03 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226484/99e2bee4-3d8d-4d8b-aea7-3ceba15497d5/content/math8_6.tif"/>
