【Mechanical Equipment Technology Exchange Edition】Mechanical Equipment 【Daily Question】20191130
Thread Content
Question: What is the moisture loss in a steam turbine? What are the causes of moisture loss? There are no answers provided for this series of posts; fellow netizens are free to share their own opinions – just reply with what you understand. Replies earn rewards ranging from 5 to 15 points; all forum members are welcome to participate actively and support the development of the forum! ! ! Chemical Equipment and Machinery
Moisture loss refers to the situation in the low-pressure area of a turbine where the steam is in a wet state. The water present in this wet steam not only fails to expand and generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades.
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.
This is because in a multi-stage turbine, the enthalpy drop across each stage causes the superheat of the steam to decrease continuously; if the superheat of the dry steam is insufficient, wet saturated steam will appear in the last stages ahead of time. As the rate of increase in humidity decreases, kinetic energy loss and blade drag increase (reactivity increases)
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.
Moisture loss refers to the situation in the low-pressure area of a turbine where the steam is in a wet state. The water present in this wet steam not only fails to expand and generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades.
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.
Insufficient superheat of the dry steam leads to the presence of unsaturated steam on the turbine blades; the moisture in this wet steam causes a loss of kinetic energy and an increase in blade resistance (an increase in reactance), and such losses are referred to as moisture losses. Reasons: 1) If the superheat of the dry steam is insufficient, wet saturated steam will appear in the last stages ahead of time. As the rate of increase in humidity decreases, kinetic energy loss and blade drag increase (reactivity increases). 2) Insufficient water removal from the saturated steam supplied to the turbine. 3) Low superheat of the inlet steam. 4) Low exhaust vacuum.
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.
Wet steam loss refers to the situation in the low-pressure section of a turbine where the steam is in a wet steam state. The water contained in this wet steam not only expands to generate work, but it also consumes the kinetic energy of the steam flow; it further exerts a braking effect on the movement of the blades, thereby wasting useful work, and it also causes erosion of the blades. The reasons for this are as follows: the small water droplets in wet steam have a greater mass than that of the steam itself, so they acquire a lower velocity than the steam. Therefore, when the steam drives these droplets to move, collisions and friction occur between them, resulting in a loss of some of the steam’s kinetic energy ； When wet steam enters the rotor blades, due to the low velocity of the water droplets, at the same circumferential speed, the direction angle at which the water droplets strike the rotor blades differs significantly from the geometric angle at the inlet of the rotor blades. As a result, the water droplets hit the back surface of the rotor blades, exerting a braking effect that prevents the rotation of the impeller. To overcome this braking force exerted by the water droplets, part of the rotational energy is lost ； When water droplets strike the back arc of the moving blades, they splash in all directions, disrupting the main flow and further increasing the friction between the water droplets and the steam, thereby reducing some of the steam’s kinetic energy. The above losses are referred to as moisture loss.