טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentSaraf Shimon
SubjectParametric Investigation of Aluminized Solid Fuel
Combustion in Ramjets and Scramjets
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Emeritus Alon Gany
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

In recent years there is a growing interest in propulsion systems that can support long range supersonic and hypersonic in-atmosphere flight vehicles. The ramjet engines are an ideal solution for such cases, since they can operate at much higher Mach numbers compared to conventional turbojet engines, and give much better performance in terms of fuel consumption compared to rockets. In addition, the simple structure of the ramjet engine makes it very cost effective, since there is no need for complex turbo-machinery components. The Solid Fuel Ramjet (SFRJ) is the simplest ramjet engine, having no fuel injection and control systems; therefore it may be a good solution for disposable applications.

The objective of the present research is to investigate theoretically and experimentally, the characteristics of an aluminized solid fuel ramjet and scramjet combustor in comparison with non-metalized fuels. The research is motivated by previous theoretical studies showing that metals such as magnesium, aluminum, and zirconium can provide much higher heat release per unit mass of air than hydrocarbon fuel; hence, substantially increasing the specific thrust of the engine.

In order to simulate experimentally the combustor inlet stagnation conditions in a high flight Mach number, vitiated air heater was used. The heater uses hydrogen gas to heat the air to simulate air stagnation properties corresponding to flight conditions of up to Mach 5.5 at high altitude (1500K and 50 atm), and is capable of testing various combustion chamber configurations. Pressure is measured along the combustion chamber and in the heater, and the thrust of the entire system is also measured. Airflow rate, as well as hydrogen and oxygen (makeup) flow rates, are also measured. For the theoretical analysis, a quasi-steady one-dimensional model of the flow within the engine was made to provide prediction of the performance for comparison with the experimental results.

Results show good agreement with the model prediction in the subsonic combustion mode, with a substantial increase of specific thrust for the aluminized fuels.  The experiments in the supersonic combustion mode maintain the same trend. However, the experimental results are lower than the theoretical prediction, indicating lower combustion efficiency and higher stagnation pressure losses. Even though, these results are significant, as they demonstrate for the first time that aluminum can burn in supersonic combustion within a solid fuel scramjet combustor.