Combustion in Rocket Engine and
Its CFD Modeling
Dr. Sharad N. Pachpute (PhD, IIT Delhi)
Modeling the Combustion System with Highest Thrust To Weight Ratio
1. Introduction to Rocket Engine Combustion
- Rocket engines are widely used for satellite launching and space mission for various applications such telecommunications, weather forecasting and military purpose.
- Rocket engine is placed at the bottom part of space vehicle where the combustion chamber is a heart of rocket engine
- High velocity and temperature exhaust gases passed through combustion and expansion through nozzle of suitable fuel and oxidizer mixture.
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
- Rocket propulsion system works on the principle of thrust generated by high velocity jet, gravity and drag forces
- The thrust is generated due to expulsion of high pressure and temperature flue gases from the nozzle
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
Mesh Model and simulation:
- Meshing of CFD domainwas carried out here using ANSYS mesheing platform
- Simulation was carried out using ANSYS FLUENT
- Using the CFD analysis, heat flux ,velocity and temperature can be predicted
- The following figure show the heat flux and temperature contours for cooling channel and combustion model.
- Temperature contours in the combustion chamber and nozzle
- Rocket engine combustion and engine design depend on type of propellants and igniters
- Liquid rocket engine combustion is complex in space due to very low temperature
- CFD modeling of rocket engine can be used to study the effect of propellants on development of modern rocket engines
References CFD Modeling
M.Panelli, D. Cardillo, D. Ricci, P. Roncioni, F. Battista The HYPROB Liquid Rocket Engine Demonstrator: CFD Modelling and Simulations, Research Gate
V Zubanov, V Egorychev, L Shabliy, Design of Rocket Engine for Spacecraft Using CFD-Modeling, – Procedia engineering, 2015,
- M. J.Nusca, Modeling Combustion Instability in Small MMH-NTO Liquid Rocket Engines Using CFD: Injector-Chamber Coupling, ARC, AIAA, 2012
Research Institute/Laboratory :