Question

Would it work if a turbine engine intake was extended and passed through an increasing in radius size pipe? You know how angular momentum increases the velocity with decreased radius? What if we increased the airflow to hypersonic speeds?

Answer 1

Extending a turbine engine intake and passing it through an increasing radius pipe would not necessarily result in increased airflow velocity or hypersonic speeds. While it is true that angular momentum is conserved and velocity increases as radius decreases, there are several factors to consider in this scenario.

1. Compressibility: As the airflow approaches and exceeds the speed of sound, it enters a regime known as compressible flow. In this regime, the behavior of the airflow is significantly different from incompressible flow. Shockwaves, expansion waves, and other complex phenomena occur, which can limit the effectiveness of simple geometric changes in increasing airflow velocity.

2. Choking: In compressible flow, there is a critical point called the choke point where the airflow reaches its maximum velocity. Beyond this point, further reductions in the pipe's radius will not increase the airflow velocity. Increasing the radius after the choke point will not result in further acceleration.

3. Flow uniformity: Increasing the radius along the length of the intake pipe can lead to non-uniform airflow distribution. This can result in flow separation, turbulence, and pressure losses, reducing the overall efficiency of the system.

4. Structural considerations: Designing and maintaining an intake system capable of handling hypersonic airflow presents significant engineering challenges. The extreme temperatures, pressure differentials, and aerodynamic forces associated with hypersonic flow require specialized materials and designs to withstand such conditions.

In summary, while angular momentum principles can be used to increase velocity with decreased radius, achieving hypersonic speeds through simple changes in the intake pipe design is not feasible. Hypersonic airflow involves complex phenomena and requires careful consideration of compressibility effects, flow uniformity, and structural integrity. Developing a successful hypersonic propulsion system requires advanced engineering and specialized designs tailored to those extreme conditions.