A new challenge for improvement of recession rate of high density polyethylene fuel and paraffin fuel of hydrid rocket rocket with multi-section swirl injection

In order to improve combustion mechanism of hybrid rocket a new method for enhancement of combustion has been proposed. The new method is to introduce swirling flow throughout fuel grain tube through multi-layer swirl injection ports, which are placed at several locations along fuel grain tube. The key issue is the method to generate swirling flow in the cavity of fuel grain at several cross section. In the outer tube fuel grain tube is located and gaseous oxygen is introduced through holes located in the narrow gap between outer cylinder and inner fuel grain from upstream and oxygen gas in injected into the inner fuel grain cavity through multiple injection ports. At one cross section of fuel grain four injection ports are located at every 90 degrees location with deflected angle where injected oxygen generates swirl at multiple cross section in the fuel grain cavity. The length of fuel grain is 400 mm and at four locations along the axis of fuel grain tube four sets of four injection ports are located. The method has been tested for high density polyethylene fuel and paraffin fuel (FT-0070) with pressurized gaseous oxygen. Several combustion test have been conducted successfully with various injection methods. The results show the recession rate of the new method is 3 times larger for high density polyethylene fuel and 5 times larger for paraffin fuel compared with the conventional method without multi-section swirl injection. The present authors are still conducting combustion experiment intensively and the results will be shown on the Symposium. The results show the new method is quite useful for the increase of the recession rate of paraffin fuel and the increase of the thrust of hybrid rocket engine.