An Hybrid Microcombustor for Regression Rate Measurements

Paper number

IAC-06-C4.2.01

Author

Dr. Luigi T. DeLuca, Politecnico di Milano, Italy

Coauthor

Dr. Luciano Galfetti, Politecnico di Milano, Italy

Coauthor

Mr. Federico Bosisio, Politecnico di Milano, Italy

Coauthor

Mr. Hari Raina, Politecnico di Milano, Italy

Coauthor

Mr. Giovanni Colombo, Politecnico di Milano, Italy

Coauthor

Mr. Filippo Maggi, Politecnico di Milano, Italy

Year

2006

Abstract

The increased worldwide interest in hybrid propulsion and the recent success of Scaled Composites’s SpaceShip One in the X-Prize contest led Space Propulsion Laboratory (SPLab) of Politecnico di Milano to develop a microsized testing facility for hybrid combustion investigations.  This experimental facility mainly includes a pressurized test chamber capable of reaching pressures up to 30 bar, the oxidizer line, the cooling system of the exhaust piping, the video acquisition system for the quasi-steady solid grain regression rate measurements, a CO2 laser for primer charge ignition, and the burnt gases dump system (also used for pressure regulation through electric valves).

The objective of this facility is to quickly assess the influence of the main parameters, (such as grain composition, oxidizer composition and flow rate, and chamber pressure) on the solid grain regression rate under operating conditions close as much as possible to those of real engines.  The grain samples, prepared at SPLab, can be enriched with a variety of high-energy ingredients (including uncoated and coated nano-aluminum powders, along with aluminum hydride), in order to evaluate their efficiency in increasing the notably low regression rates of hybrid engines. The sample geometry simulates a single port grain; the design of the central perforation can easily be modified during propellant preparation, thus allowing a straightforward testing of new geometries and of their influence on ignition and flame stability.

Numerical simulations of the chamber operations are also being conducted to properly support the development of the test facility.  The open-source OpenFoam software, running on Linux platform, was chosen because of its high versatility and reliability in solving 3D reactive flows.  Specific objectives are the fluid dynamic optimization of the test line and simulation of the burning mechanism.

While setting-up the hybrid microcombustor, preliminary experiments using a micro 2-D hybrid configuration are also being performed in order to investigate the performance of aluminized solid fuels with compressed air as oxidant. Two kinds of solid fuels were manufactured based on different inert binders: R45 HTPB or isoprene rubbers. Results obtained with R45 HTPB binder show that increasing the Al mass fraction from 5 to 20 percent, the mass burning rate gradually increases from 0.028 g/s (0 percent Al) up to 0.038 g/s (20 percent Al) at 7 bar of chamber pressure.  Under the same operating Inder the same conditions isoprene rubbers features a lower regression rate.

Abstract document

IAC-06-C4.2.01.pdf

Manuscript document

IAC-06-C4.2.01.pdf (🔒 authorized access only).

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