1. What is the difference between scavenging and supercharging ? Ans: Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. 2. What are the names given to constant temperature, constant…
Question No. 1 What maybe the possible causes for the safety trip to trip at normal speed? Answer: 1. Excessive vibration. 2. Leakage in the pilot valve. 3. Deposition of dirt in the safety trip valve. Question No. 2 What other parts of the steam turbine blades suffer from damage? Answer: 1. Blade roots. 2. Shroud band.
Question No. 1 What is combined-cycle cogeneration? Answer: A combined cycle using a gas turbine or diesel, usually driving a generator in which the exhaust gases are directed to a waste heat-recovery boiler or heat-recovery steam generator (HRSG). The steam from the HRSG is then directed to a steam turbo-generator for additional electric power production….
Question No. 1 What factors are responsible for turbine-blade failures? Answer: In the high pressure cylinder, the turbine blades are mostly affected by: 1. Solid-particle erosion (SPE) 2. High cycle fatigue Whereas, in the last few stages of the low-pressure cylinder, the blade damage is mainly afflicted by: 1. Erosion 2. Corrosion 3. Stress/fatigue damage mechanism 4. According to EPRI (Electric…
Question No. 1 What are the losses in steam turbines? Answer: 1. Residual Velocity Loss – This is equal to the absolute velocity of the steam at the blade exit. 2. Loss due to Friction – Friction loss occurs in the nozzles, turbine blades and between the steam and rotating discs. This loss is about 10%. 3. Leakage Loss. 4. Loss…
Question No. 1 Usually it has been found that SCC attack takes place particularly at key-ways of shrunk-on-disc rotors of low-pressure turbines. Why are key-ways prone to SCC attack? Answer: 1. Key-ways shrunk-fit each disc onto tile rotor shaft. They improve the rigidity of the connection between the disc and the central shaft However, key ways…
Question No. 1 In which turbine is velocity compounding utilized? Answer: In the Curtis turbine. Question No. 2 In which zone of steam turbines has temperature-creep rupture been observed? Answer: Damage due to creep is encountered in high temperature (exceeding 455°C) zones. That is, it has been found to occur in the control stages of…
Question No. 1 How would you stop air from leaking into a condenser? Answer: First, find the leak by passing a flame over the suspected part while the condenser is under vacuum. Leaks in the flange joints or porous castings can be stopped with asphalt paint or shellac. Tallow or heavy grease will stop leaks…
Question No. 1 How is pressure compounding accomplished? Answer: 1. This is accomplished by an arrangement with alternate rows of nozzles and moving blades. 2. Steam enters the 1st row of nozzles where it suffers a partial drop of pressure and in lieu of that its velocity gets increased. The high velocity steam passes on to the…
Question No. 1 How can problems of “excessive vibration or noise” due to piping strain be avoided on steam turbines? Answer: 1. The inlet as well as exhaust steam lines should be firmly supported to avoid strains from being imposed on the turbine. 2. Adequate allowance should be made for expansion of steam pipes due to heat….