Gas Turbine Cycle Quiz

The work required to compress a unit mass of air, calculated as the difference in enthalpy between the compressor inlet (h1) and outlet (h2).

The heat added to the cycle per unit mass of air, calculated as the difference in enthalpy between the combustion chamber outlet (h3) and compressor outlet (h2).

The heat rejected from the cycle per unit mass of air, calculated as the difference in enthalpy between the turbine outlet (h4) and compressor inlet (h1).

The efficiency of the cycle, calculated as the ratio of net work output (work done by the turbine minus work done by the compressor) to the heat input.

The ratio of compressor work to turbine work, indicating how much of the turbine's output is used to drive the compressor.

The back-work ratio for gas turbines is typically much higher than for vapor power plants because the gas density is significantly lower than liquid water density, requiring more work to compress.

The specific enthalpies used in the cycle calculations can be obtained from tables or estimated using constant specific heats, with some loss of accuracy.

The equations derived for the cycle apply even when irreversibilities and losses are present, although these factors significantly affect the overall performance.

The enclosed area within a cycle's thermodynamic path, indicating the amount of work produced per unit of mass flow. A larger enclosed area means greater network developed per unit of mass flow.

The ratio of pressure after compression to pressure before compression in a gas turbine.

For a fixed turbine inlet temperature, net work output per cycle initially increases with pressure ratio, reaches a maximum, then decreases. This is directly related to the efficiency of the system.

The temperature ratio between the hot and cold sides of the turbine.

A mathematical expression used to calculate net work output in a gas turbine cycle, considering temperature ratio, pressure ratio, and specific heat capacity (cp).

A performance metric for gas turbines, calculated by dividing network output by the product of specific heat capacity (cp) and turbine inlet temperature (T1).

Losses and inefficiencies that occur in a real gas turbine cycle due to factors like friction, pressure drops, and heat transfer.

These losses include frictional losses in the compressor and turbine, pressure drops in the heat exchangers, and entropy increases due to irreversibilities. These losses reduce the efficiency of the cycle and can lead to a reduction in power output.

The ratio of the actual enthalpy increase of air flowing through the compressor side of a regenerator to the maximum theoretical enthalpy increase.

A scenario where the temperature difference between two streams approaches zero, leading to near-perfect heat transfer.

The temperature of the air exiting the compressor side of a regenerator, representing the maximum achievable temperature for the colder stream.

The process of increasing the heat transfer area in a regenerator to minimize temperature difference.

The limiting case where the temperature difference between the incoming hot stream and the exiting cold stream approaches zero.

A device used in gas turbines to improve efficiency by transferring heat from the exhaust gases to the incoming air.

The temperature of the air exiting the compressor side of a regenerator in a real-world scenario.

The temperature of the incoming hot stream to a regenerator.

The lowest temperature difference between the water and the gas temperature in a combined gas turbine-vapor power cycle.

The temperature difference between the temperature of steam corresponding to drum operating pressure and water temperature leaving the economizer.

The temperature difference between the saturation temperature of water and the gas temperature leaving the evaporator.

A heat recovery steam generator (HRSG) is used to recover energy from exhaust gases by transferring it to steam in a heat exchanger that serves as the boiler.

The pinch point impacts steam production, cost, and efficiency of HRSG. A lower pinch point leads to higher heat recovery and steam generation but requires a larger heat exchanger, increasing the cost.

The work done during adiabatic compression is represented by the area under the curve on a p-v diagram. This area is larger than the area for compression with heat transfer, indicating that less work is required when heat is removed during compression.

The process of compressing a gas in stages, with cooling between each stage, to reduce the overall work required for compression.

The area under the curve on a p-v diagram represents the work done during compression with intercooling. This area is smaller than the area for adiabatic compression, indicating that less work is required.

An isentropic compression process is one where there is no change in entropy. This means that the process is reversible and there is no heat transfer.

The intercooler acts like a heat sink, removing heat from the compressed gas during the process and reducing the temperature. This cools the gas before entering the next compression stage.

The optimization process involves determining the ideal number of compression stages and the optimal operating conditions for each intercooler to minimize the total work required for compression.

The work input per unit mass during intercooled compression is represented by the area enclosed by the cycle on a p-v diagram. This area is smaller than the area for a single stage adiabatic compression, reflecting the work reduction achieved with intercooling.

Using several stages of compression with intercooling between each allows for a more efficient and effective process for large compressors.

The section of a turbojet engine that decelerates incoming air, resulting in a pressure increase (ram effect).

The section of a turbojet engine that compresses air, increasing its pressure and temperature. This section typically houses a compressor.

The component of a turbojet engine that expands hot, high-pressure gases to generate thrust. It essentially acts as a reverse compressor, converting pressure energy into kinetic energy.

A device that increases thrust by injecting additional fuel into the hot exhaust gases after the turbine. This increases the gas temperature, resulting in higher velocity and more thrust.

In an ideal turbojet cycle, the assumption that air behaves as an ideal gas and the processes are reversible. This simplifies the cycle analysis.

A process in which the air enters the diffuser and decelerates, causing its pressure to increase.

A process where the air experiences an isentropic compression within the compressor, increasing its pressure and temperature.

The process where the air is heated at constant pressure inside the combustion chamber.