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International Journal of Energetic Materials and Chemical Propulsion
ESCI SJR: 0.149 SNIP: 0.16 CiteScore™: 0.29

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v8.i5.70
pages 461-471

USE OF SOLID OXIDIZER FOR IMPROVING THE STARTING CAPABILITY OF TURBINE ENGINES

Amichay H. Gross
RAFAEL Advanced Defense Systems Ltd., Haifa Israel
Savely Khosid
RAFAEL Advanced Defense Systems Ltd., Haifa, Israel
Arie Peretz
Rafael Ltd., Haifa, Israel

ABSTRACT

Small turbine engines are often optimized to operate within a narrow range of rotational speeds, higher than the speed induced by the starting system. Under harsh ambient conditions, such as reduced pressure and density, the decreased flow rate of air may prevent the combustion process from producing sufficient power to accelerate the engine up to its minimal rotational speed for self-sustained operation (idle speed). Many applications for small turbine engines (APUs, decoys, drones, etc.) require a reliable, one-shot starting system that ensures a successful starting at first attempt, in various ambient conditions. Previous work has shown that adding oxygen into the combustion chamber, during the starting process, improves the range of conditions in which the engine could start successfully. Most solutions utilize high-pressure gaseous oxygen supply systems, that remains on-board the platform throughout the entire flight, even after the starting process is completed. The added oxygen in the combustion chamber facilitates the burning of a larger amount of fuel and improves the combustion efficiency in the chamber, thus increasing the power of the turbine, assisting it to accelerate up to idle speed. The approach presented here (patent pending) aims to facilitate the need for oxygen during the starting process, using a simple, expendable, safely storable and relatively low-cost solution. The main concept is to store and supply the oxygen using a solid oxidizing capsule (SOC), installed inside the combustion chamber. The ignition process initiates the thermal decomposition, or deflagration, of the SOC, causing it to release oxidizing species, thus, augmenting the combustion process. The increased power of the hot products going into the turbine will enable the engine to accelerate up to idle speed. After several seconds, the SOC will be fully decomposed and consumed, leaving no unnecessary mass onboard. This study shows that retrofitting an engine with a SOC can lower its minimal starting conditions (pressure and density) by roughly 30%, using available materials and technology to obtain the required properties and configuration.


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