Air Standard Cycles
Air Standard Cycles
Air standard cycles are theoretical cycles representative of the operation of heat engines. They make a few simplifying assumptions, such as the working fluid is air, which behaves as an ideal gas.
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The Air Standard Carnot Cycle
The Carnot cycle is a theoretical construct for an engine with the maximum possible efficiency. It's made up of two isothermal and two adiabatic processes.
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Isothermal Expansion
During this process, the gas expands while absorbing heat from the source maintaining a constant temperature.
Adiabatic Expansion
In this phase, the gas continues to expand, but without any exchange of heat. This causes the gas to cool down.
Isothermal Compression
Here, the gas is compressed while releasing heat to the sink at a constant temperature.
Adiabatic Compression
In the last step, the gas is further compressed but without any heat exchange, thus increasing its temperature.
Air Standard Otto Cycle
It's most commonly used in petrol engines. Composed of four internal processes: two isentropic (adiabatic but reversible) and two isochoric.
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Isentropic Compression
Gas is compressed adiabatically, with work done on it.
Isochoric Heat Addition
Heat is added at constant volume, increasing temperature and pressure.
Isentropic Expansion
Gas is expanded, i.e., work is done by the gas.
Isochoric Heat Rejection
Heat is rejected at constant volume, bringing the gas back to its initial state.
Air Standard Diesel Cycle
Used in diesel engines, this cycle involves one isochoric, one isobaric, and two isentropic processes.
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Isentropic Compression
Similar to the Otto cycle, the gas is compressed adiabatically.
Isobaric Heat Addition
Heat is added at constant pressure which differs this from Otto cycle.
Isentropic Expansion
Gas expansion, work is done by the gas.
Isochoric Heat rejection
Heat is rejected at constant volume, returning the gas to its initial state.
Air Standard Dual Cycle
The Dual cycle is a combination of Otto and Diesel cycles and is few times referred to as the Seiliger cycle. It represents a more realistic process than either the Diesel or Otto cycle.
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Gas Turbine - Brayton Cycles
This cycle is used for jet propulsion and for gas turbine engines. It differs from the other cycles in that the combustion process takes place at constant pressure.
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Isentropic Compression
Gas is compressed adiabatically.
Isobaric Combustion
Heat is added at constant pressure.
Isentropic Expansion
The gas expands and work is done by the gas.
Heat Rejection
This process returns the fluid to the state it was in before compression, completing the cycle.
Fuel and Combustion
Study of different fuels and the science of their combustion, their properties and influencing factors on combustion.
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Fuel Types
Different types of fuels used for various purposes.
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Fossil Fuels
Explains about fuels like Coal, Natural Gas, and Petroleum which were formed from remains of living organisms millions of years ago.
Biofuels
Discussion about fuels derived directly from living matter like ethanol, biodiesel, and biogas.
Synthetic Fuels
Synthetic fuels like gas to liquid fuels and coal to liquid fuels are explored in this section.
Combustion Basics
Fundamental concepts related to the process of combustion.
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Defining Combustion
Explanation of combustion as a sequence of exothermic chemical reactions between a fuel and an oxidant.
Types of Combustion
Here we discuss pre-mixed and diffusion types of combustion.
Phases of Combustion
Discussion about the three different phases of combustion - Ignition, Combustion, and Burnout.
Fuel Properties and their Determination Description of the key features of fuels and how they can be determined.
Ignition Temperature
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Calorific Value
Definition and methods to calculate the amount of heat produced by combustion of a fuel.
Ignition Temperature
The lowest temperature at which a volatile material will vaporize to form an ignitable mixture in air.
Flash Point and Fire Point
Study of flash point as the lowest temperature at which vapors of a volatile material will ignite, and fire point as the lowest temperature at which the vapor will continue to burn for at least 5 seconds.
Stoichiometry of Combustion
Study of the reactant and product quantities in chemical combustion reactions.
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Combustion Reaction Balancing
Learn how to balance combustion reactions to ensure mass conservation.
Limiting and Excess Reactants
Concept of limiting and excess reactants in combustion reactions.
Theoretical and Actual Yield
Clarify the difference between theoretical yield, the maximum possible product from a reaction, and actual yield, the amount actually produced in a real-world scenario.