You have completed your syllabus for the Power plant subject of Mechanical engineering, here you will find the 100 most important questions with solutions of the Power plant subject. Top 10 questions are given for your illustration :
1. In a gas turbine plant operating on the Brayton cycle, select the incorrect statement regarding the effect of reheating____.
A. No change in compressor input is required
B. The work output of turbine increases
C. Efficiency of the cycle increases
D. Both mean temperature of heat addition and mean temperature of heat rejection increases
During reheating in the Brayton cycle:
(i). Cycle efficiency decreases.
(ii). Both mean temperature of heat addition and mean temperature of heat rejection increases.
(iii). No change in compressor input is required.
2. Which of the following is a boiler accessory?
A. Safety Valve
B. Pressure Gauge
C. feed pump
D. fusible plug
Boiler Mountings-These are the equipment in absence of which power-plant will not work.
Accessory- These are the equipment in absence of which power-plant will not work efficiently.
Feed pump is an accessory, rest options are boiler mountings.
3. In the fuel mixture of iso octane and n-heptane, the % of n-heptane by volume is 40. The octane no. of fuel is_____.
The octane no. of a fuel is the % of iso-octane by volume in a mixture of iso-octane and n-heptane which produces the same knock intensity as the given fuel.
% of iso octane = 100 - 40 =60%
Octane no. = 60
4. Rotary compressors are used in those cases where______.
A. High discharge rate at low pressure is required
B. Low discharge rate at high pressure is required
C. Low discharge rate at low pressure is required
D. None of the above
- Rotary compressors are used in those cases where a High discharge rate at low pressure is required.
- Rotary screw compressors are generally used to supply compressed air for larger industrial applications. They are best applied in applications that have a continuous air demand such as food packaging plants and automated manufacturing systems.
5. Which one of the following modifications of the simple ideal Rankine cycle increases the thermal efficiency and reduces the moisture content of the steam at the turbine outlet?
A. Decreasing the condenser pressure.
B. Increasing the boiler pressure.
C. Decreasing the boiler pressure.
D. Increasing the turbine inlet temperature.
Due to the increase in the turbine inlet temperature, the quality of the stream at the outlet of the turbine improves.
Which increases the thermal efficiency and reduces the moisture content of the steam at the turbine outlet.
6. The cycle generally used for gas turbines is___.
A. Otto cycle
B. Brayton cycle
C. Carnot cycle
D. Dual cycle
The Brayton cycle is a thermodynamic cycle named after George Bailey Brayton that describes the workings of a constant pressure heat engine. The original Brayton engines used a piston compressor and piston expander, but more modern gas turbine engines and airbreathing jet engines also follow the Brayton cycle.
7. The cycle in which heat is supplied at constant volume and rejected at constant pressure is known as____.
A. Dual combustion cycle
B. Diesel cycle
C. Atkinson cycle
D. Rankine cycle
In the case of the diesel cycle, heat addition taken place at constant pressure, and heat rejection has taken place at constant volume.
In the case of the Rankine cycle, heat addition and heat rejection taken place at constant pressure.
In the case of dual combustion, heat addition taking place at constant volume, and constant pressure and heat rejection took place at constant volume.
8. Direct system of cooling air is one in which_____.
A.cooling water flows by gravity
B. hot water is continuously cooled and circulated
C. hot water is simply discharged
D. water is allowed to evaporate in the cylinder jacket
A direct system of cooling air is one in which hot water is simply discharged.
With direct cooling, ambient air is taken into cooled hot water discharge.
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