An intensive analysis of a specific rocket engine design that promises high performance, longevity, and low cost is called for in a $175,000 sub-contract recently awarded to The University of Tennessee Space Institute.

ORBITEC’s innovative vortex combustion rocket engine – labeled the Cool-Wall Vortex Combustion Chamber (CWVCC) — confines the mixing and burning of propellants to the inner region of a whirling flow field, preventing heat damage to the chamber.

“The outer region of the flow field prevents hot combustion products from contacting the chamber wall,” Joe Majdalani, UTSI professor and principal investigator for the contract with the Wisconsin firm, said. “While the chamber walls are subject to the radiant heat transfer, one of the propellants provides effective wall cooling to prevent heat from damaging the chamber.”

The Cool-Wall design also results in minimal heat cycling of the chamber walls, the Jack D. Whitfield Professor of High Speed Flows said. “This extends the lifetime of the chamber and allows for simple, lightweight, low-cost engine designs.”

The ultimate goal of the project is to improve ORBITEC’s computational and theoretical capabilities in modeling heat transfer, lifetime, reusability, and thrust-to-weight ratio for a liquid propelled rocket engine, according to Majdalani. Further expected benefits include simplifying the manufacture of the engine and lowering operational costs.

“Second and third generation launch vehicles will benefit from an available computational model during their developmental stages,” Majdalani said. “Computational fluid dynamics provide a feasible method for simulating combined-cycle engines, liquid propellant rocket motors, and air-breathing engines such as ramjets and scramjets.”

The CWVCC concept can improve performance from commercial and military perspectives, too, the professor noted. Aside from the propulsive applications, he said characterization of the vortex combustion field, with minor changes, may have “significant benefits” in the energy sector.

“For example,” Majdalani continued, “it could be applied to swirl burners and furnaces that employ vortex technology. It can also be applied to model gas and hydrocyclone separators and de-dusters. Potential results include improved combustion efficiency, extended lifetime, and potentially reduced emissions.”

“Our theoretical study aims at better understanding the fundamental behavior of cyclones and their inner workings,” Majdalani added. “We also hope to better understand and quantify the wall-cooling characteristics attributed to cyclonic combustion.”

Since 1996, Majdalani has been engaged in a partnership with ORBITEC.

The first NASA Phase II project was on the Vortex Injection Hybrid Rocket Engine. Since that time, the professor and his students have developed analytical solutions that “capture the essence of the gaseous motion inside the vortex-driven hybrid rockets.” They have provided both theoretical solutions and numerically simulated assessments to the first NASA/ORBITEC vortex-driven liquid rocket engine.

“Now, our focus is switching to modeling an improved version of the ORBITEC engines,” said Majdalani, “including lab scale, full scale, and workhorse engines sanctioned by the U.S. Air Force.”

Majdalani said his lengthy collaboration with Martin J. Chiaverini, Principal Propulsion Engineer at ORBITEC, “has enabled us to solve several problems of key importance – specifically those pertaining to the vortex engine development — to ORBITEC, NASA, the U.S. Air Force and Army. We are extremely grateful for Marty’s efforts to support UTSI and for his contributions in promoting vortex engine technology.” Chiaverini chairs the Wisconsin Section of the American Institute of Aeronautics and Astronautics and the AIAA Hybrid Rocket Technical Committee.

Joe Majdalani