AERONAUTICAL LECTURING NOTES

What is the need for inlet in gas turbine engine? When aircraft move with some speed, the inlet has to covert the speed to pressure. That means energy interchanging. Speed is Kinetic energy. Pressure is potential energy. The inlet not only accompanying in energy interchange, it also guides the airflow to the engine. In subsonic airplanes energy interchange may or mayn’t be. Define subsonic inlet? The aircrafts that are operating without exceeding speed of sound is called as subsonic aircrafts. Most of the commercial airplanes are subsonic airplanes.  You might have seen if you made your fight. This inlet is so simple and straight. The most upstream point of inlet is called lip. Subsonic airplanes will have thick lip. Define Supersonic inlet? We know that the main problem in supersonic flow is the formation of shock wave. For supersonic aircrafts shock wave may be advantage or disadvantage, this purely depends on the design. Behind Shock wave there will be...

What is the velocity of sound? First we will know what sound is. Sound is the resulting effect of molecular collisions. Speed of sound is the speed of transmission of a disturbance (Molecular collision) through a medium air. Mathematically, a= sqrt (ß* R* T)   m/s ß- Ratio of specific heats Cp/Cv R- Gas constant T- Temperature As the altitude increases, the temperature changes hence speed of sound too. What is Mach number? Mach number came into picture of aerodynamics by engineers in order to make their analysis ease. Mach number (M) is defined as the ratio of Speed of aircraft to the speed of sound. It has no unit. M < 1    Subsonic M=1      Sonic M> 1     Supersonic (Upto 5) M>5      Hypersonic What is critical Mach number? Though the free stream Mach number is subsonic, the aerofoil upper surface accelerates it to attain sonic at some point. Whe...