Hybrid rocket engine and injection systems. 2011
Simona Silvestri 1
Chapter 1
Definition of the Work
1.1
Research Motivations
The success of the first flight of a manned suborbital non-government space ship (SpaceShipOne) has attracted a big interest in the Hybrid Rocket Engines (HRE), which were installed on it.
The concept of the hybrid rocket propulsion has been known for a long time. In the case of HRE one propellant is liquid while another is solid. Therefore HRE can potentially have the advantages of solid and liquid rocket engines simultaneously. The attribution for reaching these advantages lies in the injection unit. The injection system is the main and practically the only system of control of a HRE. Therefore the injection unit defines the thrust and performance of HRE.
The main problems of HRE are low regression rate and residuals. The burning rate of the solid propellant in a HRE is generally significantly lower than the burning rate in a solid rocket engine. If improperly used, one of the propellants may be expended essentially before the other, which leads to the decrease of the total impulse provided by the engine. Both problems (low regression rate and residuals) can be solved by organizing the proper combustion process using the injection system. Therefore the injector system is a key element in the whole concept of a HRE.
Hybrid rocket engine and injection systems. 2011
Simona Silvestri 2
1.2
Thesis Objectives
The current status of HRE technology in Europe is sounding rockets and sub-scale ground tests. In order to pass on technology with real application, the European Commission supports the Operational Research Project on Hybrid Engines in Europe ORPHEE within the 7th Framework Program (FP7). The project aims to develop HRE technology, where the first applications of the technology could be booster engine and upper stage engine.
The aim of this work is to contribute to the ORPHEE project by collecting and presenting the current state of the art. It is clear that the HRE specifies has specific requirements with regard to the injection system different from those for current liquid rocket engines and demand a unique injection system. Thus the dawn of this work is to review the existing LRPE injection systems and determination of kinetics of the liquid phase in the combustion chamber of HRE.
The objectives of the work are:
• literature research on atomization of liquid propellants;
• review of literature on injection systems of liquid rocket engines; • review of literature on hybrid engine research;
• characterization of key mechanisms of breakup of liquid jets and sheets;
• characterization of key mechanisms of atomization and evaporation of propellants.
1.3
Presentation Plan
Chapter 2
In chapter 2 a review of the literature on solid and liquid propulsion systems is given. The structure and the main characteristics of both types of propulsion are briefly presented.
Chapter 3
In chapter 3 the characteristics of the hybrid propulsion system are described. The structure, the advantages and disadvantages are explained in detail. A comparison between solid and liquid propulsion systems is made. The different types of solid propellants and liquid oxidizers are examined with particular attention to the characteristics of the propellants used in this project (HTPB and LOx).
Hybrid rocket engine and injection systems. 2011
Simona Silvestri 3
Chapter 4
In chapter 4 the kinetics of the liquid phase in the hybrid engine is examined. The different types of jet and liquid sheet break-up are studied in detail. A correlation between the different atomization processes over a wide range of dimensionless numbers is made.
Chapter 5
In chapter 5 a review of injection types is presented. The showerhead, swirl and self impinging jet injectors and their main characteristics are studied. The process of atomization and droplet distribution are analyzed.
Chapter 6
