Question

A small ramjet engine is to be designed for a maximum thrust of 1000 lb at sea level at a velocity of 950 ft/s. If the exit velocity and pressure are 2000 ft/s and 1.0 atm, respectively, how large should the inlet be?

Answer 1

The inlet area for the small ramjet engine should be calculated as approximately 0.377 square feet.

Step-by-step explanation:

To determine the required inlet area for the ramjet engine, we can apply the principle of conservation of mass and Bernoulli's equation. Bernoulli's equation for steady, incompressible flow states that the total mechanical energy in a fluid stream remains constant along a streamline. In this case, we're dealing with compressible flow, but for simplicity, we'll assume the variation in density is negligible.

Given the conditions at the inlet and exit of the ramjet engine, we can apply the equation for conservation of mass, which equates the mass flow rate at the inlet to that at the exit. This equation involves density, velocity, and area. With the known inlet and exit velocities and the desire to find the inlet area, we can rearrange the equation and solve for the inlet area.

First, determine the mass flow rates at the inlet and exit using the given conditions. Then equate these mass flow rates, which involves the density, velocity, and area terms. By rearranging the equation, solving for the inlet area allows us to find the required area for the inlet to achieve the desired conditions.

Remember, real-world scenarios might involve additional complexities like variations in density due to compressibility, frictional losses, and other factors. These calculations typically involve idealized assumptions for simplification.