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It was designed and tested at the design point that an oxidizer rich preburner for a staged combustion liquid rocket engine propelled by kerosene and LOx. The oxidizer rich preburner was designed as some of LOx injected from the mixing head was burned with kerosene and the rest of LOx injected from injection holes in the regenerative cooling chamber was vaporized by combustion gas. The preburner is operated at OF ratio of 60 and combustion pressure of 20 ㎫. The Preburner has a honeycomb type mixing head with simplex swirl injectors, a turbulence ring improving combustion stability and uniformity of product gas temperature distribution, and a nozzle simulating the duct. With the combustion test results at the design point, the oxidizer rich preburner showed high combustion stability and uniformity of product gas temperature distribution.

In the Republic of Korea, research on staged-combustion cycle liquid propellant rocket engines (LPRE) is proceeding to improve efficiency of rocket engines. Recently oxidizer-rich preburner using single triplex injector is developed in relation to the main injector development and combustion tests have been performed. This preburner is designed to operate in nominal conditions with the combustion pressure of 10 MPa, OF ratio of 60. For a stable ignition, LOx is fed in two steps. Triethylaluminum-Triethylborane (TEAB) is used as hypergolic fuel for ignition, supplied through a fuel injector. Despite the small amount of fuel flow rate and high pressure condition, the combustion pressure was stably maintained around 10 MPa as designed. As a result of Fast Fourier Transform (FFT) of the combustion chamber dynamic pressure, 1L mode frequencies related to the acoustic instability and hydraulic resistance exist in the combustion chamber. But their amplitudes are less than 1% of the combustion pressure and it does not affect the combustion. Therefore combustion test is stably completed. In the near future, coupled tests with uni-element triplex injector preburner and uni-element gas/liquid injector main combustion chamber will be carried out.

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Korea Aerospace Research Institute (KARI) is developing gas generator cycle kerosene engines and also researching technologies of staged combustion cycle LREs for the next generation engine development. As a first step to study the staged combustion cycle, an oxygen rich combustion preburner was developed. The preburner is characterized with ultra-lean burn and high combustion pressure of O/F 60 and 200 bar, respectively. The exhaust gas of the preburner is so similar to high temperature pure oxygen gas that it may burn any metal contacted if the temperature is not strictly controlled. Hot fire tests showed that the combustion pressure was stable and the exhaust temperature satisfied the requirements of the average value and the spatial dispersion. This article will introduce the preburner and show the results of the hot fire tests Nomenclature O/F = oxygen to fuel mass flow rate LOx = liquid oxygen TEAL = triethylaluminum TEAB = triethylaluminum/boron