Computer modeling helps engineers build more efficient and stable RDE rocket engines

Engineers at the University of Washington are working on a new type of rocket engine. For a long time, researchers have faced great difficulties in the development of mathematical models. But with the help of computer modeling, the rotary detonation engine (RDE) is expected to be lighter, more efficient and easier to manufacture than conventional liquid-fueled rockets. It is reported that the model can describe the very unpredictable engine design, and how to make it work more stable.

Computer modeling helps engineers build more efficient and stable RDE rocket engines

This RDE lab controls different parameters, including cylinder clearance (from: James Koch)

The base of the RDE rocket engine is similar to the pulsed jet engine on the infamous German V1 cruise missile during World War II.

It contains a simple combustion chamber with an exhaust pipe at one end and a spring slat on the front. When operating, air can enter from the slats, mix with the fuel, and then detonate to generate a thrust pulse.

However, RDE’s research and development engineering team wants to go further in the design. James Koch, a PhD student in aeronautics and aerospace at the University of Wisconsin, says rotary blast engines take different controls in the use of combustion.

It is made of concentric cylindrical system, where propellant flows between cylinders and quickly releases heat after ignition to form shock waves. This is a strong pulse of gas, with pressure and temperature significantly exceeding the speed of sound.

In other words, the burning process of the RDE is actually an explosion. However, after the initial start-up phase, a more stable combustion pulse form can be utilized.

With the continuous consumption of propellants and the production of high pressure and high temperatures, the RDE can drain the exhaust gas from the combustion chamber. The high speed of the engine provides strong thrust.

The tricky thing is that the formation and maintenance of the explosion shock waves is very unpredictable. To better understand what is happening, the Washington team built an experimental RDE device.

The unit is able to perform different operating parameters during a series of half-second experiments and then capture the recording with a high-speed camera of 240,000 fps.

Ignition, deflagration-to-detonation (via)

Based on this data, the team created a mathematical model to determine whether the engine is running steadily as established. Even so, there is still a long way to go to determine the overall performance of the RDE.

Koch says the current goal is simply to reproduce the observed pulse behavior to ensure that the output model is similar to the experimental results (the main physics and its interactions have been identified). The follow-up task is to quantify the results of the study to see how to build a better rocket engine.

Details of the study have been published in the recent journal Physical Review E. Originally published as:

Mode-locked rotating detonation waves: Experiments and a model equation