טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDaniel Komornik
SubjectStudy of a Hybrid Gas Generator for a Ducted Rocket
DepartmentDepartment of Aerospace Engineering
Supervisor


Abstract

Ramjets are supersonic air-breathing engines having higher specific impulse and, hence, longer range than rockets for the same amount of fuel. The ducted rocket (DR), also known as ram-rocket, is a type of ramjet engine consisting of two combustion chambers: a gas generator (typically containing a fuel-rich solid propellant); and a ram combustor where the fuel rich gases generated in the first chamber are introduced and burned further with ambient air coming through inlets.

The main objective of this research was to study a hybrid gas generator for use in a ducted rocket. To the best of our knowledge, such system has never been tested, whereas it exhibits some potential advantages with regard to safety, performance, cost, availability of the fuel components, storability, and thrust control.

A hybrid gas generator was theoretically analyzed, and experimentally designed, built, and tested. Over 50 experiments were conducted and revealed that the use of paraffin wax (PW-624) as fuel with gaseous oxygen as oxidizer enabled oxidizer/fuel (O/F) ratio as low as 0.14 in the gas generator (the stoichiometric O/F ratio is 3.4), suggesting a good overall performance potential (Isp) of the ducted rocket. A theoretical evaluation of storable oxidizers such as nitrous oxide and hydrogen peroxide was done as well.

            Experimental correlation between fuel regression rate and oxidizer mass flux indicated easy and broad control of the fuel flow rate to the ram combustor and, hence, control of the overall thrust, by controlling the oxidizer cold flow.  This cold flow control is very advantageous compared to the control of the flow rate of a fuel-rich solid propellant which is done by changing the pressure regulated burning rate via a change in the hot nozzle flow cross section. The latter is difficult technically and results in a very large chamber pressure range. Given that the fuel flow rate is not controlled by the nozzle cross section area, a hybrid gas generator can also operate with an unchoked nozzle. In addition to the gas generator experiments preliminary static firing tests of a ducted rocket system employing such a gas generator were conducted as well. Such experimental studies have not been reported in the literature; additionally, these were the first ducted rocket experiments conducted at the Technion, indicating new and original data.