1. Introduction to Rocket Engine Combustion

 2.Principle of Jet Propulsion 

• In a rocket engine, the source of oxygen is called an oxidizer. The oxidizer  and fuel are mixed  and burn a combustion chamber.
• The high temperature and pressure gases produced from combustion  are allowed  through a nozzle at very high velocity. That creates a upward thrust.
• There three types of propellant are used in rocket engine: solid, liquid and gases
•  In a solid propellant are less efficient compared to liquid propellant but they can be stored for a long time without degradation.
• Solid Propellants are heavier than liquid propellant. Hence, most of rocket engines use solid propellants initially followed by liquid propellant for thrust generation.
• The following figure show the physical understanding of action and reaction principles

3.Classification of Rocket Propellant

3.1 Solid Propellant Rocket

• This rocket engine uses  sold fuels which is called as solid propellants
• Solid propellants are in composites forms which can be homogeneous mixtures of one or more  chemicals
• Composites typically are  a mixture of granules of solid oxidizer
• Solid Propellant consist of one or more ingredients:
  • Polymer binder with flakes or powders: ammonium nitrate, ammonium per chlorate, potassium nitrate
  • Energetic or explosive compounds: RDX, HMX
  • Metallic Additives: Aluminum, Beryllium
  • Burn rate modifiers: iron oxide, copper oxide

•  In a solid propellant rocket engine, igniter is used to burn the solid propellant
• The high velocity flue gases are allowed to pass through the exhaust nozzles to produce the thrust

• Schematic for Combustion chamber of Solid propellant rocket engine
• Thrust vectoring mechanism is provided to control the direction of nozzle and flue gases

• Solid propellant rocket 

• Application of Rocket Engine
  • Missile and military applications
  • Launching of light weight satellite (payloads from 500 kg to 2 tons)  up to low Earth orbit (LEO)

4.Liquid Rocket Jet Engine 

• This rocket engine used liquid propellant for combustion.
•  In liquid rocket engine, stored liquid fuels  fuel and oxidizer are injected  into a combustion chamber where they mix and produces product of combustion. Then after, the hot flue gases passes through a nozzle to accelerate. Thrust is produced to lift the rocket.
• These rocket engines are useful for  Space Shuttle to place human being  in orbit or space station

 

• The vortex generator is provide for strong and fast mixing of liquid and oxidizer
• The actual view of liquid propellant rocket engines . It comprises boost turbo-pump and combustion chamber and nozzle

•  In the cut section, we can see many nozzles are placed for quick mixing  
• Cut-section of Combustion Chamber for liquid Rocket engine  

5. Comparison of  solid and  liquid propellant rocket engine

7.CFD Modeling of Rocket Engine

Case Study 1: The Hybrid Liquid Rocket Engine

 CFD Model of Hybrid Rocket Engine

• Select the appropriate computational domain for analysis of rocket engines
• CFD modeling of rocket engines involves multi-phase turbulent combustion. To understand the solver setting in CFD solvers,  select appropriate models as per type of fuels.
• For liquid propellant,
  • Species transport model,: select non-premixed combustion model
  • Turbulence Model: k- e realizable model
  • Spray  Break up Models
  • Multiphase Models: DPM
  • Thermal Radiation model: DO Model
• Select numerical solution procedures as per basic CFD solver setting
  
• Computational Domain:  (a) cooling channel (b combustion model.

• Boundary Conditions  (a) cooling channel (b) combustion model.
  • Inlet: specify the mass flow rate of oxidizer and fuel, temperature and turbulent quantitates
  • Periodic Boundary: select periodic boundary
  • Outlet: specify pressure outlet

References

1. Lawrence Livemore National Lab