Design and Testing of a Paraffin-Based 1000 N HRE Breadboard

Abstract

The paper presents some relevant achievements in hybrid rocket propulsion carried out by the Italian Aerospace Research Centre. On the basis of the experimental results obtained on a 200 N thrust class engine, a 1000 N class breadboard, fed with gaseous oxygen coupled with a paraffin-based fuel grain, was designed and experimentally tested in different conditions. The breadboard exhibited a stable combustion in all the firing test conditions; the testing campaign allowed the acquisition of different experimental data, as pre and post-combustion chamber pressure, throat material temperature, pre-combustion chamber temperature. The new breadboard was characterized by higher measured regression rate values with respect to corresponding data obtained with the smaller scale one, highlighting that the oxidizer mass flux is not the only operating quantity affecting the fuel consumption behavior, which could be also influenced by scale parameters, such as the grain port diameter, and other operating conditions, such as the mixture ratio. Aerospace 2019, 6, 89 2 of 15Detailed studies have been presented by Karabeyoglu [4,5], where it is demonstrated that the fuel composition and its thermo-mechanical properties strongly affect the liquid layer instability and, therefore, the fuel regression rate.In this scenario, the present research was mainly focused on the investigation of the fuel characteristics, in order to ensure high performance in terms of regression rate but maintaining good mechanical properties. In a previous authors' work, results of an experimental test campaign, performed at subscale level on a 200 N breadboard, demonstrated very good performances and mechanical properties of the analyzed paraffin-wax formulation [6].Based on these results, the main objective of the present work is the scale-up of the fuel grain, adopting the same fuel formulation, and the design of a new breadboard, moving towards the 1000 N thrust class. A new experimental test campaign was carried out on the 1000 N breadboard, allowing for the investigation of the paraffin-based fuel blend behavior on a larger scale. In particular, with respect to subscale experiments, the oxidizer to fuel mixture ratio range was extended. Numerous data were acquired, including chamber pressure, thrust, temperature of the flow in the pre-chamber and temperature inside the graphite nozzle material. The latter parameter allows for the estimation of the convective heat transfer coefficient in the nozzle region, which is strictly linked to the graphite nozzle thermo-chemical erosion. This is an extremely important parameter to be evaluated, since the throat area enlargement directly affects the motor performances [7].The results of the experimental test campaign show that hybrid rocket engine can operate, with good efficiency and stability, in a wide range of operating conditions, confirming some of the advantages over both solid and liquid technologies often mentioned in the relevant literature [1,2,8,9]. Methodology and Design Design LogicThe procedure, ad...

Regression rate performance of paraffin wax and bees wax –Gox with varied grain configuration in a hybrid rocket motor

“…Paraffin wax/oxygen gas has a regression rate of 1.2 mm/s, and beeswax/oxygen has a regression rate of 1.8 ± 0.33 mm/s, a = 0.488, n = 0.62 (Putnam, 2007). Paraffin-based fuel, a = 0.071, n = 0.795, 1–3 mm/s regression rate at 40–110 kg/m 2 s oxidizer mass flux (Battista et al , 2019). Karabeyoglu et al (2004) achieved a regression rate in the range of 0.5–2 mm/s at an oxidizer mass flux of 50–150 kg/m 2 s using paraffin/oxygen.…”

“…Hybrid rockets are entitled with unique features such as simplicity, thrust modulation, safety and low cost compared to conventional liquid and solid rockets. Despite their distinct advantages, the polymeric solid fuels exhibit a low regression rate, limiting their potential as conventional hybrid fuels (Karabeyoglu et al , 2003, 2004; Karabeyoglu and Zilliac, 2006; Lee and Tsai, 2008; Sakote, 2014; Battista et al , 2019). Several researchers were found that paraffin fuel achieved promising results with various oxidizers, gaseous oxygen, liquid oxygen, hydrogen peroxide and nitrous oxide (Brown and Lydon, 2005; Karabeyoglu et al , 2004; Santos et al , 2005; Wu et al , 2018; McCormick et al , 2005).…”

Experimental Firing Test Campaign and Nozzle Heat Transfer Reconstruction in a 200 N Hybrid Rocket Engine with Different Paraffin-Based Fuel Grain Lengths

“…The domain in Figure 12a also shows the thermocouple positioning inside the nozzle wall. As previously mentioned, the imposed ℎ 𝑐 axial profile distribution was preliminary derived using numerical calculations [7]. The gas properties in these calculations took into account the OF variation over time, as reported elsewhere [7].…”

“…In this context, studies on hybrid propulsion with paraffin-based fuels have been initiated, developing and testing different engines in the thrust class of 100 to 1000 N [7,8]. In this study, following the experimental activities performed on a paraffin-based 200 N engine [9], where a 220 mm propellant grain length was adopted to perform an extensive firing test campaign, additional firing tests were conceived, reducing the propellant grain length to 130 mm and 70 mm.…”

Special Issue “Advances in Hybrid Rocket Technology and Related Analysis Methodologies”

“…They focus on the scaling up problem, the CFD modeling of the regression rate, the application of ballistic reconstruction methods to the engine performance evaluation and the effect of energetic ingredients to improve the regression rate. Experimental results from a number of firings of a paraffin-based, 1 kN thrust rocket are discussed by Battista et al [16]; the results of numerical simulations carried out with an ad-hoc CFD code are reported by Bianchi et al [17] for the high-density polyethylene regression rate calculation, highlighting the influence of the gas-phase radiation contribution to the total heat flux to the surface; some preliminary data from small-scale static firings of 3D printed fuel grains made by several materials are shown in [18], by Mc Farland and Antunes; the experimental performance data acquired from a hybrid rocket fed by nitrous oxide and high density polyethylene for the application to an apogee kick motor were treated by Kamps et al [19]. Regression rate and mass burning rate obtained with the addition of nano-or micron-sized aluminum powders and oxidizer-containing fuel-rich composites to HTPB (Hydroxyl-terminated Polybutadiene) are investigated in comparison to the baseline pure fuel in the paper of Paravan [20].…”