What is casing temperature in turbine?

It has been found that if a double casing steam turbine having an inlet steam temperature of the order of 1050″ F. is cooled in accordance with the above-described method, the outer casing may be maintained at a temperature of the order of 900 F.

Why is steam turbine exhaust temperature high?

High exhaust temperature from a steam turbine indicates that efficiency of the turbine has reduced due to scaling or some other effects. Additionally, a higher exhaust temperature could result in overstressing turbine blades since as temperature increases the strength of material decreases.

How hot is the steam in a steam turbine?

200 °C to 400 °C.
A steam turbine consists of stationary and rotating blades on an axle. High pressure steam enters the turbine. The steam can be anywhere from 200 °C to 400 °C. The stationary blades direct streams of high pressure steam onto the rotating blades, which turns the axle.

What are the three supply steam conditions that must be determined in the performance test of a steam turbine?

Steam turbines extract power from steam as it passes from high-pressure and high-temperature conditions at the inlet to low-pressure and low-temperature conditions at the outlet.

Why do turbine casings need to be cooled?

The large surplus of air cools the hot sections of the engine to acceptable temperatures ranging from 1,500° to 2,100 °F. Because of the effect of cooling, the temperatures of the outside of the case are considerably less than those encountered within the engine. The hottest area occurs in and around the turbines.

What is steam turbine differential expansion?

Differential Expansion of Steam Turbine:- It is the difference between the rotor expansion and the Casing Expansion. It is +ve if rotor expands more than casing. It is -ve if casing expands more than rotor. During initial startup diff Exp. is +ve as rotor mass is less and expands at more faster stage than casing.

Why is my HP exhaust temperature high?

The HRSGs are duct fired, and in the unfired condition, the HP steam inlet enthalpies are high, resulting in HP turbine exhaust temperatures exceeding 750 F during normal operation. This temperature tends to be even higher during start-up when flow rate is low, approaching the 775-800 F limits for carbon steel.

How heat affects the performance of steam turbine?

Turbine steam inlet temperature is another major parameter affecting turbine performance. Reducing steam inlet temperature reduces the enthalpy, which is a function of both the inlet temperature and pressure. At higher steam inlet temperatures, heat extraction by the turbine will also be increased.

Why is steam turbine efficiency so low?

The compressor efficiency decrease is due primarily to the effects of compressor fouling. Any reduction in the turbine efficiency is due to the decrease in the turbine non-dimensional speed resulting from the increase in the turbine entry temperatures, as observed in Fig. 18.15.

Can steam turbine operates without lubrication?

Steam turbines cannot operate without lubrication. Therefore, turbine lubricating oil systems must be designed, operated and maintained for extreme reliability. Lubricating oil systems affect overall facility loss prevention more than most mechanical systems.

What is the effect of temperature on a turbine casing?

When the casing top is hotter then the bottom, the casing tends to bend down if the temperature gradient is constant from the top of the casing to the bottom and along its lengths, then the maximum bending stress occurs mid- casing vertically and between the casing support horizontally. Due to this effect, the turbine cylinder causes vibration.

Why do most turbines have double shell casings?

Most modern turbines, with steam pressures over 100 bar and ratings greater than 100 MW, have HP casings of double-shell design (Figs 1.92 and 1.93). This has been adopted because of the difficulty of designing a single casing to withstand the thermal and pressure stresses and yet be capable of flexible operation.

What is the difference between the different types of start-up turbines?

The difference between the above types of start-up consists in the fact that in the former case steam supplied to the turbine has greater than casing metal temperature, while in the latter two cases, depending on the boiler characteristics, steam temperature can be lower or higher than the casing temperature.

What is the bending stress in steam turbine blades?

This bending stress is created in blade joints under the pressure effect in the high-pressure steam flowing through the turbine cylinder the magnitude of these stresses is depending upon the steam flow rate, the temperature drops across the blade stages, rotating speed of blades and also blade weight.