Improving the Combustion Performance of a Hybrid Rocket Engine using a Novel Fuel Grain with a Nested Helical Structure

Summary

A technique utilizing a solid fuel grain with a novel nested helical structure to improve the combustion performance of a hybrid rocket engine is presented.

Abstract

A technique to improve the combustion performance of a hybrid rocket engine using a novel fuel grain structure is presented. This technique utilizes the different regression rates of acrylonitrile butadiene styrene and paraffin-based fuels, which increase the exchanges of both matter and energy by swirl flow and recirculation zones formed at the grooves between the adjacent vanes. The centrifugal casting technique is used to cast the paraffin-based fuel into an acrylonitrile butadiene styrene substrate made by three-dimensional printing. Using oxygen as the oxidizer, a series of tests were conducted to investigate the combustion performance of the novel fuel grain. In comparison to paraffin-based fuel grains, the fuel grain with a nested helical structure, which can be maintained throughout the combustion process, showed significant improvement in the regression rate and great potential in improvement of combustion efficiency.

Introduction

A technique to improve the combustion performance of a hybrid rocket engine is urgently required. To date, practical applications of hybrid rocket engines are still far less than those of solid and liquid rocket engines^1,2. The low regression rate of traditional fuels limits the improvement of thrust performance for the hybrid rocket engine^3,4. In addition, its combustion efficiency is slightly lower than that of other chemical energy rockets due to internal diffusion combustion⁵, as shown in Figure 1

Protocol

1. Experimental setup and procedures

1. Preparation of fuel grain
   NOTE: The fuel grain with novel structure consisted of two parts, which are shown in Figure 4. As the main part of the novel grain, the paraffin-based fuel accounts for more than 80% of the total mass. The ABS substrate is used as an additional fuel. The preparation of this fuel grain was realized by combining 3D printing and centrifugal casting.
   1. Substrate preparation
      1. Open 3D software for ABS substrate drawing.
         NOTE: The ABS substrate, which intended to provide the helical framework and support for the paraffin-based fuel, is c....

Results

Figure 7 shows the changes in combustion chamber pressure and oxidizer mass flow rate. To provide the necessary time for flow regulation, the oxidizer enters the combustion chamber in advance. When the engine builds pressure in the combustion chamber, the oxygen mass flow rate drops rapidly and then maintains a relatively steady change. During the combustion process, the pressure in the combustion chamber remains relatively stable.

Images showing a comparison of c.......

Discussion

The technique presented in this paper is a novel approach using a fuel grain with a nested helical structure. There are no difficulties in setting up the necessary equipment and facilities. The helical structure can be easily produced by 3D printing, and nesting of paraffin-based fuels can be easily carried out by centrifugal casting. Fused deposition molding (FDM) 3D printers are not expensive and the cost of centrifuges is low.

When the inner surface of the shaped fuel grain was found to hav.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3D printer	Raise3D	N2 Plus	305 × 305 × 605 mm
3D drawing software	Autodesk	Inventor
ABS	Raise3D	ABS black	1.75 mm
Camera	Sony	A6000
Carbon	Aibeisi	ATP-88AT
Centrifugal machine	Luqiao Langbo Motor Co.Ltd	Custom	≤1450 rpm
Data processing software	OriginLab	Origin 2020
EVA	DuPont Company	360	binder
Mass flow controller	Bronkhost	F-203AV	0-1500 ln/min
Melt mixer	Winzhou Chengyi Jixie Co.Ltd	Custom
Multi-function data acquisition card	NI	USB-6211
Paraffin	Sinopec Group Company	58#	Fully refined paraffin, Melting point≈58°C
PE wax	Qatar petroleum chemical industry Company	Custom
Slicing software	Raise3D	ideaMaker
Spark plug	NGK	PFR7S8EG
Stearic acid	ical Reagent Company	Custom	hardener