MECH0005 Draw a simplified engine diagram suitable for control volume analysis of thrust.

Background

The principle of jet propulsion, based on Newton`s third law, involves emitting a jet of fluid in one direction to propel an object in the opposite direction. This concept finds extensive applications in nature and engineering, such as squids, rockets, and modern airplane jet engines. However, adapting these systems for repeatable, cost-efficient, and sustainable use poses challenges, particularly in designing reusable propulsion systems effective both within and beyond Earth`s atmosphere.

Questions

1. (a) Draw a simplified engine diagram suitable for a control volume analysis of thrust. Ensure all relevant parameters are labeled. Write out the full version of the momentum equation and explain how each term relates to the physical engine.

(b) The engine is tested in a controlled-atmosphere wind tunnel matching conditions at 25 km altitude and Mach 4 speed. Engineers measure steady thrust at 2.5 × 10^6 N. Use the momentum equation and provided data to estimate the exhaust gas speed, detailing each step logically.

Air enters the engine at Mach 4, consistent with undisturbed air. Speed of sound at this altitude is 295 m/s. Assume inflow and outflow mass flow rates from points 2 and 7, with inlet and outlet cross-sectional areas of 5 m^2 and 1.5 m^2, respectively.

2. Apply gas power cycle concepts to develop simplified thermodynamic cycles for analyzing engine performance.

Assumptions:

• Helium loop: closed Brayton cycle.
• Air-breathing engine: open Brayton cycle.

Analyze expansion and compression processes in components (nozzle, compressors, turbines) as isentropic. Use data from Figure 3.

(a) Reconstruct the Helium Loop with constant-pressure heat exchangers and calculate thermal efficiency.

(b) Convert the open cycle to an equivalent closed cycle for analysis. Illustrate and explain cycle stages (states 1-2-3-4-6-7-8).

(c) Calculate thermal efficiency of the equivalent closed cycle.

3. Choose one engine component and analyze it based on fluid mechanics and thermodynamics covered in the module. Describe fluid and energy flow through the component using Figure 3 data. Include concise calculations, discuss engineering concepts, and propose design priorities for improvement.