N5 Power Machines steam turbines

For more information: ialegodi@gmail.com 082 396 7717 STEAM TURBINES Two types of steam turbines: I. Reaction turbine II. Impulse turbine The function of steam turbine:  it converts the kinetic energy of a moving fluid or gas into rotational energy that can be used to drive the dynamo and generate electricity The special statements about steam turbine (conditions)  The blades are symmetrical [inlet angle = outlet angle]  There is no AXIAL thrust [Vf1=Vf2]  The flow is frictionless [µ,k=1; Vr1=Vr2]  The gas discharge at an AXIAL direction [ β=90] The symbol used in steam turbine The meaning about those symbols 1. U  DN The mean blade speed , peripheral mean blade 2. V1 The velocity of the gas leaving the nozzle The velocity of the steam entering the turbine 3. V2 The velocity of the gas leaving the turbine 4. Vr1 Inlet relative velocity of the moving blade 5. Vr 2  kVr1 Outlet relative velocity of the moving blade 6. α The nozzle velocity 7. β Angle of the gas leaving the turbine 8.  Inlet angle of the moving blade 9.  Outlet angle of the moving blade 10. k Velocity co-efficient of friction Formula: P  power developedby turbine  muw;  diagram  2uw v12    100; f axial  m v f 1  v f 2 ; the driving force  mw Possible questions about steam turbine: 1. The velocity of the steam leaving the nozzles of an impulse turbine is 900 m/s and the nozzle angle is 20 . The blade velocity is 300 m/s and the velocity coefficient of friction is 0, 7. The blading is symmetrical and the mass flow rate is 1, 8 kg/s. Downloaded from hlayiso.com

For more information: ialegodi@gmail.com 082 396 7717 1.1. Use the scale of 1 cm = 50 m/s and construct a velocity diagram 1.2. Use the diagram and determine the following: 1.2.1. The blade inlet angle 1.2.2. The driving force on the wheel 1.2.3. The axial thrust 1.2.4. The diagram power 1.2.5. The diagram efficiency 2. Steam with a velocity of 600 m/s enters an impulse turbine blades at an angle of 25 to the plan of rotation of the blades. There is 10% loss in relative velocity due to friction in the blades. The blade exit angle is 30 and the mean blade speed is 255 m/s. 2.1. Use the scale of 1 cm = 50 m/s, and construct a velocity diagram 2.2. Use the diagram and determine the following: 2.2.1. The inlet angle of the moving blade 2.2.2. The exit angle of the gas from the turbine 2.2.3. The power developed by the turbine 2.2.4. The efficiency of the diagram 2.2.5. The axial thrust per kg of steam 3. The nozzles of an impulse turbine are inclined at an angle of 20 to the plane of rotation of the wheel and steam enters the blades of the wheel at a velocity of 535 m/s, the nominal diameter of the moving blades is 474 mm and the steam exits them at an angle of 22 . Test conducted on the steam turbine indicates that for the speed of 9 872 r/min, the steam consumption is 45 kg/min and the power developed is 84, 6 kW. 3.1. Calculate the blade velocity of the turbine in m/s 3.2. Calculate the total whirl velocity of the turbine 3.3. Construct the velocity diagram in the ANSWER BOOK by using the scale 1 mm = 5 m/s 3.4. Use the data from the diagram and calculate the velocity co-efficient of friction of the moving blades 4. An impulse turbine rotates at a speed of 3 000 r/min and it has a radius of 334 mm. The outlet and inlet angles of the moving blades are 30 each and the turbine develops 120 kW of power. The gas is discharge in an axial direction and the loss in velocity due to friction is 9% 4.1. Calculate the blade velocity of the turbine in m/s 4.2. Construct a velocity diagram by using the scale of 1cm = 10 m/s Downloaded from hlayiso.com

For more information: ialegodi@gmail.com 082 396 7717 4.3. Determine the nozzle angle 4.4. Determine the mass of the gas which flows through the turbine every minute 5. Gas leaves a single-stage impulse turbine at an angle of 42 . The friction over the blading causes a 10% loss in velocity. The relative velocity of the gas at the inlet to the moving blades is 350 m/s at an angle of 30 . The blade experiences a peripheral velocity of 175 m/s, when 50 kg of gas flows through the turbine every second. 5.1. Use the scale of 1 cm = 25 m/s and construct a velocity diagram 5.2. Determine the following from the diagram: 5.2.1. The nozzle angle 5.2.2. The nozzle velocity 5.2.3. The exit angle of the moving blades 5.2.4. The axial thrust 5.2.5. The power developed 6. The nozzles of an impulse turbine are inclined at 20 to the plane of the wheel. The steam enters the turbine at a velocity of 720 m/s and leaves the turbine at a velocity of 480 m/s. The friction of the steam flowing over the blades is negligible. The blades rotate at an average radius of 250 mm and at a speed of 6 876 r/min. The nozzles deliver 240 kg of steam every minute to the turbine. 6.1. Use the scale of 1 cm = 50 m/s and construct a velocity diagram 6.2. Determine the following: 6.2.1. The power developed by the turbine 6.2.2. The diagram efficiency 6.2.3. The inlet blade angle 6.2.4. The exit blade angle 6.2.5. The angle at which the steam leaves the turbines 7. An impulse turbine develops 125 kW at a mean blade diameter of 805 mm and a speed of 9 490 r/min. The inlet and outlet of the moving blade is 30 and the coefficient of velocity is 0,8. The gas exit the turbine at an angle of 87 . 7.1. Use the scale of 1 cm = 50 m/s and construct a velocity diagram 7.2. Determine the following: 7.2.1. The nozzle angle Downloaded from hlayiso.com

For more information: ialegodi@gmail.com 082 396 7717 7.2.2. The mass flow rate 7.2.3. The efficiency of the diagram 8. The mean blade diameter of a single-stage impulse turbine is 1 960 mm and it rotates at a speed of 3 898 r/min, the blade speed is 0,4 of the speed of the gas velocity leaving the nozzles. The nozzle are inclined at an angle of 22 to the plane of the wheel and the blading is symmetrical. The gas loses 12% velocity due to friction as it moves over the blades. The turbine uses 100 kg of gas every minute. 8.1. Calculate the peripheral speed of the blade 8.2. Calculate the nozzle velocity of the gas 8.3. Use the scale of 1 cm = 50 m/s and construct a velocity diagram 8.4. Determine the following: 8.4.1. The relative velocity of the gas at the inlet of the moving blade 8.4.2. The relative velocity of the gas at the outlet of the moving blade 8.4.3. The velocity of the gas leaving the turbine 8.4.4. The end thrust developed 9. An impulse turbine has a blade ring of which is 1, 91 m in diameter and it rotates at 3 500 r/min. The blade is 0, 35 of the steam velocity leaving the nozzles, which are inclined at 20 to plane of the wheel. The velocity coefficient of friction is 0, 9 and there is NO AXIAL THRUST. 9.1. Calculate the blade velocity of the turbine in m/s 9.2. Calculate the velocity of the gas leaving the nozzles 9.3. Use the scale of 1 mm = 5 m/s and construct a velocity diagram 9.4. Use the diagram and determine the following: 9.4.1. The efficiency of the diagram 9.4.2. The power developed per kg of steam per second 10. 5 Mg of steam per hour leaves the nozzles of an impulse turbine at 1000 m/s at 20 to the plane of the wheel. The inlet and outlet angles of the moving blades are 35 and 30 respectively. The steam leaves the turbine at angle of 85 . The wheel rotates at 11 000 r/min. 10.1. Use the scale of 1 mm = 5 m/s to construct a velocity diagram 10.2. Determine the following: 10.1. The mean blade speed in m/s Downloaded from hlayiso.com

For more information: ialegodi@gmail.com 082 396 7717 10.2. The diameter of the wheel in mm 10.3. The relative velocities of the moving blade 10.4. The velocity co-efficient 10.5. The power developed 11. This information applies to a single-stage impulse turbine: the peripheral mean blade speed is 400 m/s, the nozzles are inclined at angle of 20 , the angles of the moving blades are equal at angle of 30 and the steam leaves the turbine at an angle of 85 to the plane of the wheel. 11.1. Use the scale of 1 mm = 5 m/s and construct a velocity diagram 11.2. Determine the following from the diagram: 11.2.1. The velocity of the steam entering the turbine 11.2.2. The velocity of the steam leaving the turbine 11.2.3. The velocity co-efficient of friction 11.2.4. The efficiency of the diagram Downloaded from hlayiso.com