Advanced Swirl Injectors for Low-Cost, Fast-Response Applicationse

Bi-centrifugal swirl injectors have been used extensively in Russian liquid rocket engines. These injectors have been shown to offer many characteristics favorable for rocket engines or development programs including:

• high performance given increased chamber residence times,
• controllable combustion stability,
• effective injection of propellants having both a gas and liquid phase,
• favorable heat transfer characteristics, and
• low fabrication costs due to relatively simple design.

However, traditional bi-centrifugal swirl injectors have a significant fill volume associated with them making them difficult to use in application that require fast on/off times. After designing representative swirl injectors and examining this problem, IN Space created a swirl injector-derived design that retains the benefits of a traditional swirl injector but has a significantly lower fill volume. This new swirl injector design has fill volumes on the order of the industry-standard impinging jet injectors, which are known for their fast response times but also their combustion stability problems and high costs.

Based on the results of the computer model, IN Space developed an engine mass model to determine the effectiveness of injecting and decomposing peroxide in this manner for a launch vehicle application. While some weight savings over a catalyst bed-only approach were possible, the model also highlighted the dependence of the decomposition rate on the ambient gas temperature. This lead to the investigation of a torch ignition system, where significantly higher temperatures could be achieved in a bipropellant combustion process, to efficiently decompose and react the hydrogen peroxide in a launch vehicle.

Test fire of IN Space’s Low-Cost, Fast-Response Swirl Injector.

This study was conducted through a Phase I SBIR contract from the Missile Defense Agency.