Abstract
In this study, the adaptation possibilities of a constant volume combustion chamber (CVCC) for research on the ignition of hypergolic propellants are presented. The application of hypergolic bipropellants and crucial parameters regarding their ignition behaviour are discussed. The initial studies on ignition delay measurements presented here does not cover the whole range of conditions present in practical systems where hypergolic ignition occurs. In the study, a need for an evaluation of the influence of pressure on the ignition delay was indicated as the reason to conduct research on hypergolic ignition in low and high-pressure environments. Moreover, the study reviews the state-of-the-art experimental methods of investigating the ignition under atmospheric, low and high-pressure conditions, including those utilizing a constant volume combustion chamber. The drop test was pointed out as the most commonly used method; this makes it advantageous in terms of comparing the results with those obtained by other researchers. Therefore, the drop test was selected as a method to be used in a CVCC. The test rig developed here was designed based on a CVCC initially designed for diesel sprays’ visualization in high-pressure conditions. All the required modifications, especially the design of the oxidizer dosing unit, are presented in the study.
Highlights
Hypergolic propellants are pairs of liquid fuels and oxidizers in which ignition occurs spontaneously upon contact between the two liquids; thereby eliminating the need for a complex ignition system [16]
The reliable restart capability of engines based on hypergolic propellants makes them ideal for spacecraft manoeuvring
An important criterion to evaluate the performance of hypergolic bipropellants is the ignition delay, which is defined as the time from the physical contact of the liquid fuel and the oxidizer to the onset of ignition
Summary
Hypergolic propellants are pairs of liquid fuels and oxidizers in which ignition occurs spontaneously upon contact between the two liquids; thereby eliminating the need for a complex ignition system [16]. In order to investigate hypergolic properties of bipropellants, some research methods and procedures have been developed: the drop test and the impingement test They are focused on investigating ignition delay time. It can be used as an initial test for the pre-selection of hypergolic propellants, as applies in this study. The drop test in an atmospheric environment is a successful method for initial determination of ignition delay, especially in the early stage of propellant selection It is far away from the conditions in which these propellants are supposed to operate. In this study a connection between proven and novel solutions is presented and the possibilities of further development are discussed
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