This work was supported by the National Natural Science Foundation of China (Grant Nos. 11802315, 11872368 and 11927803) and Equipment Pre-Research Foundation of National Defense Key Laboratory (Grant No. 6142701190402).

1. Experimental setup and procedures
<ol>
	<li>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.
	<ol>
		<li>Substrate preparation
		<ol>
			<li>Open 3D software ...

<ol>
	<li>Boiron, A. J., Cantwell, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2013).</li><li>Mazzetti, A., Merotto, L., Pinarello, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paraffin-based+hybrid+rocket+engines+applications:+A+review+and+a+market+perspective.">Paraffin-based hybrid rocket engines applications: A review and a market perspective.</a> Acta Astronautica. 126, 286-297 (2016).</li><li>Karabeyoglu, A., Zilliac, G., Cantwell, B. J., DeZilwa, S., Castellucci, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scale-Up+Tests+of+High+Regression+Rate+Paraffin-Based+Hybrid+Rocket+Fuels.">Scale-Up Tests of High Regression Rate Paraffin-Based Hybrid Rocket Fuels.</a> Journal of Propulsion and Power. 20 (6), 1037-1045 (2004).</li><li>Jens, E. T., Narsai, P., Cantwell, B., Hubbard, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2014).</li><li>Kuo, K. K., Chiaverini, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fundamentals of Hybrid Rocket Combustion and Propulsion. , (2007).</li><li>Boardman, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 33rd Joint Propulsion Conference and Exhibit. , (1997).</li><li>Connell, T. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> AIAA Propulsion and Energy 2019 Forum. , (2019).</li><li>Di Martino, G. D., Mungiguerra, S., Carmicino, C., Savino, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computational+fluid-dynamic+modeling+of+the+internal+ballistics+of+paraffin-fueled+hybrid+rocket.">Computational fluid-dynamic modeling of the internal ballistics of paraffin-fueled hybrid rocket.</a> Aerospace Science and Technology. 89, 431-444 (2019).</li><li>Leccese, G., Cavallini, E., Pizzarelli, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> AIAA Propulsion and Energy 2019 Forum. , (2019).</li><li>Cardoso, K. P., Ferr&#227;o, L. F. A., Kawachi, E. Y., Gomes, J. S., Nagamachi, M. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ballistic+Performance+of+Paraffin-Based+Solid+Fuels+Enhanced+by+Catalytic+Polymer+Degradation.">Ballistic Performance of Paraffin-Based Solid Fuels Enhanced by Catalytic Polymer Degradation.</a> Journal of Propulsion and Power. 35 (1), 115-124 (2019).</li><li>Paccagnella, E., Barato, F., Pavarin, D., Karabeyo&#287;lu, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaling+Parameters+of+Swirling+Oxidizer+Injection+in+Hybrid+Rocket+Motors.">Scaling Parameters of Swirling Oxidizer Injection in Hybrid Rocket Motors.</a> Journal of Propulsion and Power. 33 (6), 1378-1394 (2017).</li><li>Kumar, R., Ramakrishna, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+protrusion+on+the+enhancement+of+regression+rate.">Effect of protrusion on the enhancement of regression rate.</a> Aerospace Science and Technology. 39, 169-178 (2014).</li><li>Kumar, R., Ramakrishna, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Hybrid+Fuel+Regression+Rate+Using+a+Bluff+Body.">Enhancement of Hybrid Fuel Regression Rate Using a Bluff Body.</a> Journal of Propulsion and Power. 30 (4), 909-916 (2014).</li><li>Degges, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2013).</li><li>Connell, T., Young, G., Beckett, K., Gonzalez, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> AIAA Scitech 2019 Forum. , (2019).</li><li>Whitmore, S., Peterson, Z., Eilers, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &amp; Exhibit. , (2011).</li><li>Whitmore, S. A., Armstrong, I. W., Heiner, M. C., Martinez, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 2018 Joint Propulsion Conference. , (2018).</li><li>Whitmore, S. A., Peterson, Z. W., Eilers, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+Hydroxyl+Terminated+Polybutadiene+and+Acrylonitrile+Butadiene+Styrene+as+Hybrid+Rocket+Fuels.">Comparing Hydroxyl Terminated Polybutadiene and Acrylonitrile Butadiene Styrene as Hybrid Rocket Fuels.</a> Journal of Propulsion and Power. 29 (3), 582-592 (2013).</li><li>Whitmore, S. A., Sobbi, M., Walker, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2014).</li><li>Whitmore, S. A., Walker, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+Model+for+Hybrid+Fuel+Regression+Rate+Amplification+Using+Helical+Ports.">Engineering Model for Hybrid Fuel Regression Rate Amplification Using Helical Ports.</a> Journal of Propulsion and Power. 33 (2), 398-407 (2017).</li><li>Creech, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 53rd AIAA Aerospace Sciences Meeting. , (2015).</li><li>Lyne, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 2018 Joint Propulsion Conference. , (2018).</li><li>Elliott, T. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 52nd AIAA/SAE/ASEE Joint Propulsion Conference. , (2016).</li><li>Armold, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2013).</li><li>Armold, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. , (2014).</li><li>Fuller, J., Ehrlich, D., Lu, P., Jansen, R., Hoffman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &amp; Exhibit. , (2011).</li><li>Lee, C., Na, Y., Lee, J. W., Byun, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+induced+swirl+flow+on+regression+rate+of+hybrid+rocket+fuel+by+helical+grain+configuration.">Effect of induced swirl flow on regression rate of hybrid rocket fuel by helical grain configuration.</a> Aerospace Science and Technology. 11 (1), 68-76 (2007).</li><li>Tian, H., Li, Y., Li, C., Sun, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regression+rate+characteristics+of+hybrid+rocket+motor+with+helical+grain.">Regression rate characteristics of hybrid rocket motor with helical grain.</a> Aerospace Science and Technology. 68, 90-103 (2017).</li><li>Hitt, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 2018 Joint Propulsion Conference. , (2018).</li><li>Wang, Z., Lin, X., Li, F., Yu, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combustion+performance+of+a+novel+hybrid+rocket+fuel+grain+with+a+nested+helical+structure.">Combustion performance of a novel hybrid rocket fuel grain with a nested helical structure.</a> Aerospace Science and Technology. 97, (2020).</li><li>McBride, J. B., Gordon, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Computer Program for Calculation of Complex Chemical Equilibrium Compositions and APPlications. , (1996).</li><li>De Zilwa, S., Zilliac, G., Karabeyoglu, A., Reinath, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit. , (2003).</li><li>Franco, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regression+Rate+Design+Tailoring+Through+Vortex+Injection+in+Hybrid+Rocket+Motors.">Regression Rate Design Tailoring Through Vortex Injection in Hybrid Rocket Motors.</a> Journal of Spacecraft and Rockets. 57 (2), 278-290 (2020).</li></ol>

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...

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 engines1,2. The low regression rate of traditional fuels limits the improvement of thrust performance for the hybrid rocket engine3,4. 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. Although various techniques have been studied and developed, such as the use of multi-ports6, enhancing additives7,8,9, liquefying fuel10,11,12, swirl injection13, protrusions14, and bluff body15, these approaches are associated with problems in volume utilization, combustion efficiency, mechanical performance, and redundancy quality. Thus far, structural improvement of the fuel grain, which does not have these shortcomings, has attracted more attention as an effective means of improving combustion performance16,17. The advent of three-dimensional (3D) printing has brough an effective way to increase the performance of hybrid rocket engines through the ability to rapid and inexpensively produce either complex conventional grain designs or nonconventional fuel grains18,19,20,21,22,23,24,25,26,27,28,29,30. However, during the combustion process, these improvements in combustion performance diminishes with the characteristic structure burning, resulting in a decrease in combustion performance23. We have demonstrated that a novel design is useful in improving performance of hybrid rocket engines31. The detail for this technique and representative results is presented in this paper.
The fuel grain consists of a helical substrate made by acrylonitrile-butadiene-styrene (ABS) and a nested paraffin-based fuel. Based on centrifugal and 3D printing, the advantages of the two fuels with different regression rates were combined. The special helical structure of the fuel grain after combustion is shown in Figure 2. When gas passes through the fuel grain, numerous recirculation zones are simultaneously created at grooves between blades, which is shown in Figure 3. This characteristic structure on the inner surface increases the turbulence kinetic energy and swirl number in the combustion chamber, which increase the exchanges of both matter and energy in the combustion chamber. Ultimately, the regression rate of the novel fuel grain is effectively improved. The effect of improving the regression rate has been well proven: in particular, the regression rate of the novel fuel grain was demonstrated to be 20% higher than that of the paraffin-based fuel at the mass flux of 4 g/s&#183;cm2,32.
One advantage of the fuel grain with a nested helical structure is that it is simple to manufacture. The molding process mainly requires a melt mixer, a centrifuge, and a 3D printer. The ABS substrate formed by 3D printing greatly reduces the manufacturing cost. Another significant and unique advantage is that the enhancement effect does not disappear during the combustion process.
This paper presents the experimental system and procedure for improving the combustion performance of a hybrid rocket engine using the novel fuel grain structure. Additionally, this paper presents three representative comparisons of combustion performance parameters to prove the feasibility of the technique, including oscillation frequency of combustion chamber pressure, regression rate, and combustion efficiency characterized by characteristic velocity.

<table>
	<tbody>
		<tr>
			<td>3D printer</td>
			<td>Raise3D</td>
			<td>N2 Plus</td>
			<td>305 &#215; 305 &#215; 605 mm</td>
		</tr>
		<tr>
			<td>3D drawing software</td>
			<td>Autodesk</td>
			<td>Inventor</td>
			<td></td>
		</tr>
		<tr>
			<td>ABS</td>
			<td>Raise3D</td>
			<td>ABS black</td>
			<td>1.75 mm</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Sony</td>
			<td>A6000</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon</td>
			<td>Aibeisi</td>
			<td>ATP-88AT</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifugal machine</td>
			<td>Luqiao Langbo Motor Co.Ltd</td>
			<td>Custom</td>
			<td>&#8804;1450 rpm</td>
		</tr>
		<tr>
			<td>Data processing software</td>
			<td>OriginLab</td>
			<td>Origin 2020</td>
			<td></td>
		</tr>
		<tr>
			<td>EVA</td>
			<td>DuPont Company</td>
			<td>360</td>
			<td>binder</td>
		</tr>
		<tr>
			<td>Mass flow controller</td>
			<td>Bronkhost</td>
			<td>F-203AV</td>
			<td>0-1500 ln/min</td>
		</tr>
		<tr>
			<td>Melt mixer</td>
			<td>Winzhou Chengyi Jixie Co.Ltd</td>
			<td>Custom</td>
			<td></td>
		</tr>
		<tr>
			<td>Multi-function data acquisition card</td>
			<td>NI</td>
			<td>USB-6211</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraffin</td>
			<td>Sinopec Group Company</td>
			<td>58#</td>
			<td>Fully refined paraffin, Melting point&#8776;58&#8451;</td>
		</tr>
		<tr>
			<td>PE wax</td>
			<td>Qatar petroleum chemical industry Company</td>
			<td>Custom</td>
			<td></td>
		</tr>
		<tr>
			<td>Slicing software</td>
			<td>Raise3D</td>
			<td>ideaMaker</td>
			<td></td>
		</tr>
		<tr>
			<td>Spark plug</td>
			<td>NGK</td>
			<td>PFR7S8EG</td>
			<td></td>
		</tr>
		<tr>
			<td>Stearic acid</td>
			<td>ical Reagent Company</td>
			<td>Custom</td>
			<td>hardener</td>
		</tr>
	</tbody>
</table>

improving the combustion performance of a hybrid rocket engine using a novel fuel grain with a nested helical structure

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.

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...

Watch this Scientific Journal Video about Improving the Combustion Performance of a Hybrid Rocket Engine using a Novel Fuel Grain with a Nested Helical Structure at JoVE.com

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

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.

A technique to improve the combustion performance of a hybrid rocket engine using a novel fuel grain structure is presented. This technique utilizes the ...

This method can help answer the question of how to improve the combustion performance of grains. The main advantages of this protocol is that the helical structure fuel grains will not disappear with the combustion process. This method can also be applied to grain formula with different material compilations such as EBS and PUX.Begin by preparing the acrylonitrile butadiene styrene, or ABS substrate, using 3D software. Save the 3D substrate structure as an STL file. Then open the 3D slicing software and import the structure.Click start slicing and select speed print mode from the main template. Double-click speed. Then change the infill density to 100%and select raft with skirt for the platform edition.Click save and close and then click slice. Turn on the 3D printer and import the ABS substrate's slice file. Set the temperature of the heated bed and nozzle to 100 and 240 degrees Celsius respectively.Click start to print after stabilization. To ensure successful printing, apply solid glue to the hot plate to increase the adhesion between the ABS substrate and the hot plate. For a paraffin-based fuel preparation prepare raw materials of paraffin, polyethylene wax, steric acid, ethylene vinyl acetate and carbon powder.Configure the paraffin-based fuel according to manuscript directions and place the configured materials into the melt mixer. Then melt and stir them until completely mixed. Place the ABS substrate into the centrifuge and secure it with an end cap.Plug in the powder and turn on the water cooling pump switch. Then turn on the centrifuge relay and increase the speed to 1, 400 RPM. Open the valve on the melt mixer and start casting.Remove the fuel grain and trim the shape. Measure and record the weight, length and inner diameter of the complete fuel grain and photograph it. To assemble the hybrid rocket engine, fix the combustion chamber section on the slide rail, load the fuel grain, and install the post combustion chamber section.Install the head and nozzle. Then install the torch igniter on the head of the hybrid rocket engine. Install the spark plug and connect the power supply.Connect the nitrogen, oxidizer, ignition methane, and ignition oxygen gas supply lines between the test bench and the gas cylinder. Connect the industrial computer, the multifunction data acquisition card, the mass flow controller, and the control box of the test bench. Power on the test bench, the mass flow controller and the igniter.Open the FlowDDE software and click on communication settings. Click the corresponding connection interface and click okay. Click open communication to establish communication with the flow controller.Then open the measurement and control program, or MCP. Set the input and output channel of the multifunction data acquisition card and click run to establish communication with the entire system. Check the MCP running status and set it to manual control mode.Check the working condition of the spark plug and perform a valve test. Test the data recording function. Next, open the setting interface and set test time, including valve opening and closing time, ignition time, and data recording duration.Set safety requirements and clear personnel from the experimental area. Open the cylinder valve and adjust the output pressure of the regulating valve according to the different mass flow rate conditions. Open the setting interface and set the oxidizer mass flow rate.Turn on the camera, then set the MCP to automatic control mode and wait for trigger. Click start on the MCP to start the experiment. After about one minute, click stop and turn off the camera.Close the gas cylinder and open the valve in the pipeline to relieve the pressure. Power off the test bench and remove the fuel grain. Measure and photograph the fuel grain as previously demonstrated.Changes in combustion chamber pressure and oxidizer mass flow rate are shown here. 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 stable. A comparison of combustion chamber pressure oscillation frequency is presented here. The pressure fluctuation spectrum of the novel fuel grain contained three distinct peaks which were associated with the hybrid low-frequency, Helmholtz mode, and the acoustic half-wave in the combustion chamber.The positions of the pressure peaks of the novel fuel grain were basically the same as that of the paraffin-based fuels, which indicates that the novel structure is not likely to introduce additional combustion oscillations. Regression rate as a function of oxidizer flux was compared between the fuel grains. At the same oxidizer mass flow rate, the regression rate of the novel fuel grain was higher than that of the paraffin-based fuel and the gap gradually widened as the oxidizer flux increased.Characteristic velocity was used to compare combustion efficiency. The novel fuel grain exhibited a higher characteristic velocity than paraffin-based grains at various oxidizer and fuel ratios. This corresponds to an average increase of combustion efficiency of about 2%When attempting this protocol, remember that that the casting temperature of paraffin-based fuel cannot be higher than 120 degrees Celsius.

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5.5K visualizações.  Chinese Academy of Sciences. Este método pode ajudar a responder à questão de como melhorar o desempenho de combustão dos grãos. As principais vantagens deste protocolo é que a estrutura helicoidal dos grãos de combustível não desaparecerá com o processo de combustão. Este método também pode ser aplicado à fórmula de grãos com diferentes compilações de materiais, como EBS e PUX.Comece preparando o estireno de butadieno acrilonitrilo, ou substrato ABS, usando software 3D. Salve a estrutura do subs...