Reheating in a gas turbine
Reheating is a method of increasing the mean temperature of heat reception. In this the gas is again heated after it has expanded in the gas turbine. This increases the work output of the turbine by keeping the compressor work constant. By reheating the mean temperature of heat rejection is also increased, resulting in a decrease in the thermal efficiency of the plant.
When inspection doors on the walls of boilers are opened, flame does not leap out because
The flame does not leap out during opening of inspection door because there is negative pressure in the combustion area. Negative pressure is achieved in balanced draft boilers by using forced draft fans to force air into boiler (pressuring it) and Induced draft fans to remove air from the boilers to create negative pressure
Boiler rating is usually defined in terms of
Boiler rating is the heating capacity of a steam boiler. It is expressed in BTU per hour (BTU/h), horsepower (hp), or steam output in kg/hr at 100°C’ and atmospheric pressure. Each kilogram of steam receives 2257 kJ of heat from the boiler.
The rating indicates the maximum capacity of a boiler. When a boiler operates at its maximum rated capacity, it is referred to as the maximum load. If the load varies from hour to hour, it operates at a varying load. Load and load variations can influence the amount of chemicals required for treatment and the treatment controls required.
Cochran boiler is a
It is a multi-tubular vertical fire tube boiler having numbers of horizontal fire tubes. It is the modification of a simple vertical boiler where the heating surface has been increased by means of numbers of fire tubes.
Coke is produced by
Coke is produced by heating coal for several hours to high temperature (T ≈ 1000‐1100oC) out of contact of air until all volatile matters are removed. The process is called “carbonization” or Destructive distillation of coal”
Which solution is used in ice plant?
There are three main circuits of working medium in ice plant:
Refrigeration circuit: Ammonia as working medium (primary refrigerant) which produces the cold by changing its phase at different location.
Cooling water circuit: Cooling water as working medium to remove the heat of condenser.
Brine circuit: Brine solution as working medium which transfers the cold from ammonia to water filled cans where ice is to be formed.
Rotary compressor is used in those cases where:
Joule cycle is used in:
Gas turbines operate on Brayton cycle/Joule cycle. The Joule cycle consists of four internally reversible processes:
What is a load curve?
A load curve, also known as load profile, is a chart illustrating the variation of electrical load over a period of time. Generating companies or electrical utilities use this chart to study the pattern of load variation and to obtain information regarding the amount of power to be generated at a specific time.
A gas turbine plant working on Joule cycle produces 4000 kW of power. If its work ratio is 40%, what is the power consumed by the compressor in (kW
In Bryton cycle, heat addition is a________.
Brayton cycle is a theoretical cycle for gas turbines. This cycle consists of two reversible adiabatic or isentropic processes and two constant pressure processes. The heat addition and rejection takes place at constant pressure.
In a 50% reaction stage of a gas turbine
R = static enthalpy change in rotor/static enthalpy change in stage
ΔhR = 0.5 ΔhR + 0.5 ΔhS
ΔhR = ΔhS
The compressor does not form a part of
A deceleration of the air from Mach number 3 at diffuser inlet to Mach 0.3 in combustion chamber causes the pressure ratio to rise to more than 30. Due to shock and other losses inevitable at such velocities of the pressure rise is not available at the required combustion pressure. This principle of ram pressure rise is used in the ramjet engines. Thus compressor does not form a part of ramjet.
The primary fuel used in nuclear power plants is
Uranium-235, enriched to about 5% from its naturally occurring level of 0.7% is used as primary fuel in the nuclear power plants.
Which of the following is the non-positive displacement compressor?
Example of non-positive displacement compressor :
i) Centrifugal compressor
ii) Axial flow compressor
iii) Dynamic compressor
iv) Blade comrpessor
The once-through boiler is
The Benson boiler employs forced circulation and has a unique characteristic of the absence of steam separating drum. The entire process of heating, steam formation and superheating is done in a continuous tube and accordingly it is called as once-through boiler.
Free air is air at
Free air delivered is a term used to compare the handling capacity of different compressors. It is volume of air when converted to 1 bar pressure and 15°C.
In an impulse turbine, the pressure drops
In impulse turbine pressure drop takes place only in the nozzle. There is no pressure drop either in moving or in fixed blades. The pressure in the moving and fixed blades remains constant.
The efficiency of jet engine is
For turbo jet engines the efficiency is higher for higher speeds. Whereas in turbo prop engines it first increases then decreases.
For minimum work input in a two-stage compression process the intermediate pressure is the
For minimum work input during compression precess,