Combustion Stability Breakthrough

After more than 40 years of research into the most challenging propulsion issue, combustion instability, Dr. G. A. Flandro has successfully developed a self-consistent analytic model and computational algorithm, the Universal Combustion Device Stability (UCDS) model.  This breakthrough in combustion stability analysis provides an unprecedented capability to predict the stability characteristics of combustion devices.  Unlike previous ad hoc attempts, the UCDS model uses calculations that are based entirely on known or measurable parameters. 

With UCDS it is now possible to predict the actual wave geometry, time history of the wave amplitude, limit amplitude reached by the wave system, and accompanying changes in the combustion chamber state properties.  Design of corrective procedures can now be accomplished with full physical understanding of the action of damping mechanisms.  With UCDS, the development cost and risk of a new combustion device can be dramatically reduced by eliminating the need to use cut-and-try methods to overcome stability issues. 

The UCDS Model is physically accurate for ANY steady combustor and can predict the stability characteristics of rockets, jets, and scramjets.  The UCDS Model has accurately predicted the stability characteristics several devices, including the F-1 rocket engine. 

UCDS can be rapidly applied to address the daunting stability challenges faced by current propulsion development efforts.

Gloyer-Taylor Laboratories LLC

Elegant Solutions to Complex Problems

Combustion Instability Risks

Combustion instability represents the single greatest technical risk facing any combustion device development program, and since there has been no effective means to address combustion instability (until UCDS), even a hint that a new combustion device has a combustion stability issue can place a program on the fast track to cancellation.  Modern political and financial constraints prohibit the use of costly cut-and-try techniques that have been historically needed to mitigate a stability issue.  This paradigm is especially troubling to propulsion developers, since demands for high performance almost guarantee that stability issues will arise. 

New Paradigm

UCDS provides an effective means to predict the stability characteristics of a combustion device early in the development process.  It is now possible to provide solid answers to dreaded questions of;

‘how do you know there won’t be a

stability issue?’

&

‘how can you guarantee that you can

 eliminate stability issues?’

It is now possible to bypass costly cut-and-try test programs and avoid the program cancellation axe.

UCDS Functionality

UCDS provides true predictive capability based entirely on known or measurable parameters.  With UCDS, it is now possible to characterize the stability of any steady flow combustion device.

 

An example of this predictive capability is shown to the right.  These graphs show the results from the application of UCDS to the F-1 rocket engine, which was used on the first stage of the Saturn V launch vehicle.

The UCDS predictions successfully captured the stability characteristics of the F-1 engine, which were observed during the extensive development program.   

Using the UCDS prediction results, it is possible to quantify the risk of instability, to understand the wave dynamics, to predict the structural and thermal impact of an instability, and to eliminate or mitigate instability risk.

With this capability, the development cost and risk for new combustion devices will be greatly reduced, by the eliminating the risks of combustion instability.

UCDS Predictive Capabilities

· Limit cycle amplitude vs. net surface admittance

· Critical surface admittance vs. operational parameters (e.g. pressure, flow rates, and mixture ratios)

· Wave frequencies and full waveform geometry

· Time evolution of wave dynamics

· Time to reach limit cycle (or time to decay) vs. pulse size

· Changes in mean pressure, density, temperature and heating vs. time and at limit conditions

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UCDS Services

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UCDS capabilities are described in more detail in the following reference:

Flandro, G. A., "Oscillatory Behavior of Liquid Propellant Rockets, Scramjets, and Thrust Augmentors," Invited Plenary Lecture, Seventh International Symposium on Special Topics in Chemical Propulsion (7-ISICP), Kyoto, Japan, 20 September 2007