1,720,974 research outputs found
Numerical and Experimental Characterization of Throttleable Hybrid Propulsion Systems. Caratterizzazione Numerica e Sperimentale di Sistemi Propulsivi Ibridi a Spinta Variabile
Full text linkThe 1960s have been flourishing years for hybrid rocket propulsion: the thirst for knowledge pushed the engineers of those years to design and test any kind of motor configuration, and for several possible applications. Many projects of those years are fascinating and outstanding still nowadays.
The cold war era had extinguished any enthusiasm and interest for hybrids for years. It is approximately at the beginning of the '90s that a renew interest for hybrids has come alive, since, besides the pure performance, affordability and safety have become a must.
Hybrids are safe, simple, reliable, low cost and throttleable. All these characteristics make them suitable for several applications, not necessarily in replacement of solids and liquids, but possibly complementary. The TRL of hybrids has still to be improved in order to put hybrids on the market.
Among the aforementioned peculiarities of hybrids, their throttleability is the object of the present research.
This work is focused on the investigation of a high performing throttleable hybrid motor, conceived for soft-landing applications.
The main purpose of the research is to develop and characterize a motor in the 1kN-class, with characteristics like: high performance at different operative conditions, both in terms of regression rate and combustion efficiency enhancement, safety and simplicity, reliability.
The research is part of a wider framework: a EU FP7 granted project, called ``SPARTAN'', leaded by Thales Alenia Space, and aimed at developing a soft-lander demonstrator for planetary exploration, provided by a hybrid propulsion system. The University of Padova is partner of the project, so the preliminary design guidelines of the motor have been defined according to the requirements of the SPARTAN consortium.
The motor considered burns HTPB as fuel and 87.5%H2O2. High performance is expected to be achieved by means of vortex injection. The selection of H2O2 as oxidizer has been made to take advantage from its many qualities, like high density and high OF ratio, non-toxicity, possibility to decompose it through a catalyst. Thanks to this last aspect, fuel ignition is expected to be accomplished thanks to the hot gases resulting from oxidizer decomposition.
The doctoral research has been conducted combining several tools in synergy: analytic models, CFD simulations and experimental tests. The analytic models have supported the comprehension of the physical processes involved. The numerical simulations have been useful tools both to provide indications for final design purposes and to investigate in detail aspects of the internal ballistic of the motor, which were difficult to be observed in experimental tests. Finally, experimental tests have been conducted to validate the numerical prediction and assess the achievement of the desired and expected results.
As a first step, once defined the preliminary design of the motor according to the SPARTAN requirements, a deep CFD investigation has been performed, in order to finalize the design.
Preliminary CFD simulations have been carried out on a motor configuration already developed and tested at UPD, in order to study and characterize the physics beyond vortex injection, and thus assess its effectiveness in enhancing the hybrid motor performance. The numerical results have been compared with an analytic model of the vortex flowfield. The outcome of this phase has been compared with the experimental data available.
In a second phase, the preliminary design produced within SPARTAN has been simulated to predict its performance and its sensitivity to some changes in the motor configuration and operative conditions. A prediction of the expected performance and some useful indications for the experimental tests are the main output of this second phase.
Then experimental tests of the motor have been performed to evaluate the actual performance at different throttling levels.
In order to overcome the issues related to handle and store hydrogen peroxide in high concentration, the design of the experimental test-bed foresaw the integration of the hybrid motor with a gas generator, responsible of reproducing 87.5% H2O2 in decomposed condition, as it would be passing through a catalyst. The mixture produced inside the gas generator is then injected as oxidizer into the combustion chamber of the hybrid motor.
The experimental test-bed has been integrated and a preliminary phase of calibrations has been required to assess the correct functioning of the feed lines.
Moreover a complete diagnostic system has been defined and installed, in order to have a full and accurate monitoring of the interesting parameters.
Many tests have been performed at the beginning, to optimize the functioning of each subsystem composing the test-bed, and in order to obtain the correct oxidizer mixture and to assure HTPB ignition.
Finally, the hybrid motor has been successfully tested at three different fixed throttling levels: full thrust, 75% thrust and 50% thrust.
Fuel ignition has been achieved at each throttling level, and the dependency of the ignition delay from the throttling level has been considered.
The performance of the motor has been analyzed at each level, in terms of: resulting regression rate, as a function of the oxidizer flux; combustion efficiency; combustion stability. A comparison between the performance obtained at each level has been performed.
Any possible evidence of nozzle throat erosion has been monitored.
Finally, the results have been compared with the reference regression rate law, proper of 87.5%H2O2-HTPB, in order to demonstrate the effectiveness of the gas generator in simulating decomposed hydrogen peroxide in high concentration.
The actual mixture composition has also been estimated
Numerical and Experimental Activities in Support of the Development of Hybrid Rocket Engine for Soft-Landing Applications
No full text
The "Vortex Reloaded" project: numerical investigation on fully tangential vortex injection in N2O - paraffin hybrid motors
No full text
Advanced CFD Investigation for Predicting Regression Rate in Hybrid Rockets49th AIAA/ASME/SAE/ASEE Joint PropulsionConference
No full textNumerical Model to Analyze Transient Behavior and Instabilities on Hybrid Rocket Motors
No full textThe study of hybrid rocket transient behavior is a very important issue in order to analyze instabilities and develop throttleable motors. In this paper, an unsteady numerical model is presented. The model is composed of three submodels linked together: 1) zero-dimensional model of the combustion chamber, 2) one-dimensional (1-D) radial model of the fuel grain, and 3) zero-dimensional model of the feeding system. The first model simulates combustion chamber dynamics. The one-dimensional radial model of the fuel grain includes both standard polymeric and liquefying propellants characterized by a melting layer. The fuel block models the heat exchange to the wall, the heat propagation through the solid/liquid phase, and the fuel surface evaporation/entrainment. Finally, the injection system block simulates the unsteady behavior of the feeding line and droplets break-up-evaporation dynamics. In this paper, all the blocks are presented together with their validation versus analytical test cases. For each block, an analysis of the effect of the influencing parameters on the transient thruster behavior is presented
Numerical and Experimental Investigation of Unidirectional Vortex Injection in Hybrid Rocket Engines
No full text
- …
