LATEST TURBINE OPERATION QUESTION ANSWER 2018
Hello ! power engineers today we discussed about the LATEST TURBINE OPERATION QUESTION ANSWER 2018 . these question answer is helpful for those who worked as a turbine operation engineer and who want to know more about the turbine operation . turbine is critical component of any power generation plant because its consist very critical component like thrust pad , blades , bearing etc. which takes extra care during start up of the turbine . these question answer help us the our readers know more about the turbine operation. lets discussed the question answer in detail way
Q、Why is it required to cool down the generator during running?
Ans. The vortex loss and circuit resistance loss in the magnetic inductance during generator running is transferred to thermal energy resulted in the heating of the rotor and stator. The reduction of the insulation strength due to temperature rise at the insulation material of generator coil leads to the generator insulation breakdown, therefore the continuous discharging the heat due to energy loss is a must. tb- t2=δt。
Q、What is the degree of super cooling of the condensed water? What is the heat transferring terminal difference of the condenser.
Ans. The degree of super cooling of the condensed water refers to the difference of the saturated temperature tb and the condensed water temperature tn under the condensing pressure. heat transferring terminal difference of the condenser refers to the difference of the turbine exhaust steam temperature tb and the outlet temperature of the condenser cooling water t2 . it can be state in the following formula tb- t2=δt .
Q、What is the vacuum and degree of vacuum of the turbine? Please briefly state its physical meaning.
Ans. When the pressure inside the vessel is lower than the atmospheric pressure, this part of pressure is called vacuum while the pressure inside the vessel is called the absolute pressure. Another way to refer vacuum is any pressure that is lower than the atmospheric pressure. Vacuum varies in degrees: when there is no pressure inside the vessel, that is, the absolute pressure is zero, it is called the complete vacuum. Other conditions are referred as incomplete vacuum. The vacuum inside the condenser is incomplete vacuum.
The relationship between vacuum, absolute pressure and the atmospheric pressure is as follows:
h1 + h2 = h
h1: height of the vacuum mercury column inside the vessel, unit: mm
h2: height of the absolute pressure mercury column inside the vessel, unit: mm
h: height of the atmospheric pressure mercury column inside the vessel, unit: mm
Degree of vacuum refers to the proportional vacuum indication. That is, degree of vacuum = h1/ h×100%. (h1 is the measured height of the vacuum mercury column; h is height of the atmospheric pressure mercury column).
When the absolute pressure of the condenser is stable, the degree of vacuum varies with the atmospheric pressure. It is proper to calculate the value by the absolute pressure. After measured the height of the atmospheric pressure mercury column and the vacuum mercury column inside the condenser, the absolute pressure can be calculated like this: P =( h – h1)/735.6 (engineering atmospheric pressure). Such as, if the measured vacuum inside the condenser is 720mm mercury column, with the atmospheric pressure from referring to the manometer is 750mm mercury column. The absolute pressure and degree of vacuum will be P =(h – h1)/735.6 =(750 – 720)/735.6=0.04 and degree of vacuum= h1/ h×100% =(720/750)×100% =96% respectively.
Q、Why is the given vacuum required during turbine driving and rotating?
Ans. Certain vacuum normally around -70kpa shall be prepared before the turbine driving. If the vacuum is too low, more steam shall be required to rotor and the sudden exhausting of the excessive exhaust steam to the condenser, making its pressure of steam side transiently increased too much probably resulted in the steam side of condenser being pressurized, and the safety module of the condenser to be damaged with great heat impact to the cylinder and the rotor.
During the rotor being driven, excessive high vacuum is not required because the excessive high vacuum not only extend the duration for vacuum formation, but also cause the heating up to slow down and unsteady speed due to the less steam flow through the turbine and small heat discharging factor, thereafter to extend the start-up duration.
Q、What are the main tasks of the condenser?
Ans. 1. Establish and maintain vacuum at the turbine exhaust outlet.
2. Re-circulate the working fluid after they are deaerated from the condensed water having done
LATEST TURBINE OPERATION QUESTION ANSWER 2018
Q、How does the vacuum in the condenser formed?
Ans. During normal running, the exhaust steam in the condenser suddenly condensed to condensed water resulted in the abrupt contraction of the specific volume, thereafter establish the vacuum in the condenser.
The vacuum in the condenser is established by the extraction of air from the turbine and condenser through the water jet air ejector.
Q、What are the indications for observing the running performance of the condenser?
Ans. It mainly consists of three aspects:
1. Being most optimized vacuum or not.
2. Secure the condensed water quality.
3. The ability to maintain the minimum degree of super cooling condensed water.
Q、What are the damages thereby if the vacuum reduction at the turbine?
Ans.(1) The available enthalpy drop of exhaust steam pressure reduces and not economical, at the same time make the unit output reduced.
(2) Heating expansion at the exhaust cylinder and bearing support may cause the eccentric changes and vibration.
(3) Excessive high temperature exhaust steam may cause the copper pipe loosening and break the compactness.
(4) May increase the axial thrust of the turbine
(5) Vacuum reduction will cut the flow rate of the exhaust steam and affect the working of the last stages. Separate flow and spiral flow shall appear and big shock at certain blade and damage the blade.
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