Understanding the Constant Volume Cycle

Thermodynamic cycles are sequences of processes that transfer heat and work. Different cycles are named either after their inventors or based on the key thermodynamic processes involved. The question asks to identify the cycle known as the "constant volume cycle". This refers to a cycle where heat is added and rejected at constant volume.

The Otto Cycle Explained

The Otto cycle is a foundational thermodynamic cycle that describes the functioning of a typical spark-ignition internal combustion engine (gasoline engine). It was developed by Nikolaus Otto.

The Otto cycle consists of four main processes:

• Isentropic compression: The fuel-air mixture is compressed.
• Constant volume heat addition: Heat is added instantaneously at constant volume, representing the combustion process.
• Isentropic expansion: The hot gases expand, doing work.
• Constant volume heat rejection: Heat is rejected instantaneously at constant volume, representing the exhaust process.

Because the heat addition and heat rejection processes occur at constant volume, the Otto cycle is commonly referred to as the constant volume cycle.

Analyzing Other Thermodynamic Cycles

Let's look at why the other options are not correct:

• Carnot cycle: This cycle consists of two isothermal and two adiabatic processes. It does not involve constant volume heat addition or rejection.
• Joule cycle (Brayton cycle): This cycle is used in gas turbines and involves constant pressure heat addition and constant pressure heat rejection, along with adiabatic compression and expansion.
• Diesel cycle: This cycle involves constant pressure heat addition and constant volume heat rejection, along with adiabatic compression and expansion. While it has one constant volume process, its heat addition occurs at constant pressure, distinguishing it from a pure constant volume cycle.

Therefore, the cycle also called the constant volume cycle is the Otto cycle.