The chamber pressure required for combustion in a turbojet engine is a crucial parameter that affects the engine’s performance. It’s typically measured in Pascals (Pa) in the International System of Units (SI). Chamber pressure is the pressure inside the combustion chamber of the engine, where the air and fuel are mixed and ignited.
The formula for chamber pressure (P_c) can be expressed as:
where,
- is the chamber pressure in Pascals (Pa).
- is the specific gas constant of the working fluid in the combustion chamber in J/(kg·K).
- is the absolute temperature of the combustion chamber in Kelvin (K).
-  is the cross-sectional area of the combustion chamber in square meters (m²).
- ην is the combustion efficiency (dimensionless), which represents how effectively the air and fuel are converted into useful work. It is typically less than 1, and its value depends on the design and operating conditions of the engine.
-
 is the mass flow rate of air through the engine in kilograms per second (kg/s).Please note that the specific gas constant, , may vary depending on the composition of the working fluid in the combustion chamber. For simplicity, the formula above assumes air as the working fluid, but in reality, the combustion process may involve other gases or mixtures, and the specific gas constant should be adjusted accordingly.
The chamber pressure in a turbojet engine is a critical parameter because it affects the thrust generated by the engine and, subsequently, the overall performance of the aircraft. The goal is to achieve a sufficient chamber pressure to ensure effective combustion and produce the desired thrust while considering factors like engine design, materials, and operating conditions.