Liquid Propellant Research Articles

Petri Nets Applied in Purge Algorithm Analysis for a Rocket Engine Test with Liquid Propellant

During the development stage of a space vehicle, instrumented tests are carried out on the ground to prove the operational capacity of each liquid-propellant rocket engine, which is installed in this type of vehicle. The task of elaborating a Test Bench project for a propulsion unit with this application is complex and involves several steps, one of these steps being related to the analysis of this bench capacity to meet the algorithms for the liquid-propellant rocket-engine full run of tests, which is considered fundamental for this project’s operational success. Due to the high costs involved in this project’s elaboration and execution, it is strategic to use computational resources to evaluate, by simulation, the main operational functionalities that are previously established for this bench to perform. In this context, this work presents a model proposal through Petri Nets to evaluate, by computer simulation, an architecture capacity that was designed for the Test Bench to meet an algorithm dedicated to the liquid-propellant pipelines purge during the run of hot tests with the liquid-propellant rocket engine. The method used in this work to carry out the simulation shows the operational response of each module of this architecture, in accordance with the steps contained in the purge algorithm, which allows for analyzing, for each event of the process, the Petri Nets properties, mainly those related to the conservativeness, liveliness, deadlock-type, and confusion-type conflicts. The simulation carried out with the proposed model allows for the portrayal of the physical architecture and the operational states of the purge system according to the steps foreseen in the algorithm, showing that the conservation property is met because the number of marks remains constant, the vivacity property is also met since all positions have been reached, and there is no mortal-type conflict, as the simulation is not stopped; only confusion-type conflict is identified, which was solved with the strategic insertion of resources in the model in order to fix crashes related to the competition for tokens in the transition-enabled entries. The satisfactory results obtained in these simulations suggest that the modules provided for this architecture are sufficient and appropriate for carrying out all the steps contained in the purge algorithm, which will minimize or even eliminate the disorders that may be caused by the presence of foreign elements in the propellant supply lines during the tests with the rocket engine.

Numerical Study of Flow Boiling of ADN-Based Liquid Propellant in a Capillary

During the operation of ADN (ammonium dinitramide, (NH4+N(NO2)2-))-based thrusters, the ADN-based liquid propellant, a non-toxic green energetic material, tends to flow boil in the capillary tube due to heat transfer from the wall. A three-dimensional transient numerical simulation of the flow boiling of ADN-based liquid propellant in the capillary tube was carried out using the VOF (Volume of Fluid) coupled Lee model. The flow-solid temperature and the gas-liquid two-phase distribution and the wall heat flux at different heat reflux temperatures were analyzed. The results show that the magnitude of the mass transfer coefficient of the Lee model significantly influences the gas-liquid distribution in the capillary tube. The total bubble volume increased from 0 mm3 to 957.4 mm3 when the heat reflux temperature was increased from 400 K to 800 K. The bubble formation position moves upwards along the inner wall surface of the capillary tube. Increasing the heat reflux temperature intensifies the boiling phenomenon. When the outlet temperature exceeded 700 K, the transient liquid mass flow rate in the capillary tube was already reduced by more than 50%. The results of the study can be used as a reference for the design of ADN-based thruster.

ВИКОРИСТАННЯ ПІДШИПНИКІВ КОВЗАННЯ У АВІАЦІЙНІЙ ТА КОСМІЧНОЇ ТЕХНІЦІ

Examples and prospects of various types of sliding bearings applications in power elements of aircraft engines and in turbopump units (TPU) of liquid propellant rocket engines (LPRE) are discussed in this article.In the second half of the last century, piston aircraft engines were replaced by turboprop (TPE) and turbojet (TJE) engines. Almost all leading manufacturers of these motors use rolling bearings as rotor supports for the main power units. The use of sliding bearings is extremely rare and is the exception rather than the rule. These exceptions include the company Pratt & Whitney, which has been using sliding bearings since the 1950s (engine PT6A). The sliding bearings are also used in modern turbofan engines Pratt & Whitney PW1000G series. The use of sliding bearings as a support for planetary gearbox elements has a number of advantages over rolling bearings, since under normal operating conditions such supports have a significantly longer service life.In rocketry, sliding bearings are used as supports for a LPRE TPU. Examples of such supports are hydrodynamic sliding bearings of the first German missiles during the Second World War (one of them was the FAU-2) and Soviet missiles developed by S.P. Korolev and V.P. Glushko. As our analysis has shown, in the 50s the use of sliding bearings in LPRE was abandoned due to a number of advantages of rolling bearings over sliding bearings, especially taking into account the very short service life of these engines (hundreds of seconds). Recently, however, sliding bearings as supports for a TPU have been attracting more attention again due to the development of reusable missile systems with a sharp increase in required service life. Although the results achieved for TPU with rolling bearings still provide the required durability, studies of the sliding bearings for TPU design with increased service life are relevant.The data obtained as the result of the analysis describe existing practice of using sliding bearings in units of aircraft and rocket engines, as well as the prospects for their further use.

Removal of unsymmetrical dimethylhydrazine: A critical review with particular focus on photocatalytic oxidation

Unsymmetrical dimethylhydrazine (UDMH) has been widely used in liquid propellant, as well as plant growth regulation, chemical synthesis, photographic chemicals, etc. However, its uncontrolled discharge into environment could cause severely adverse effect on ecosystem and human health due to its highly toxic nature. Therefore, biodegradation, adsorption and advanced oxidation process (AOP) techniques have been intensively applied for UDMH removal. Among the AOP techniques toward UDMH removal, photocatalytic oxidation has been attracting increasing attention due to its low energy and oxidant consumption at the function of TiO2-based or other photocatalysts with modifications of chemical doping or heterojunction constructing. This overview comprehensively reviews the nature of UDMH and the recent reported techniques for UDMH removal, with a specific focus on the available works on photocatalytic oxidation of UDMH. The corresponding adsorptive-degradation mechanisms and performances in photocatalytic UDMH degradation are summarized, and opinions on the future directions for UDMH removal techniques are provided.

Investigation on heat transfer and flow of a sonic steam jet condensation in crossflow of water in pipes

Direct contact condensation is widely used in nuclear reactor thermal-hydraulic systems, underwater propulsion systems, liquid propellant rocket engines and other industrial fields due to its highly efficient heat and mass transfer. Understanding the distribution of the thermal-hydraulic parameters of steam jet condensation systems has become an urgent need for optimal design and safe operation of industrial processes. In this paper, the flow characteristics and heat transfer for the condensation of sonic steam jet in crossflow in a subcooled water pipe are numerically simulated based on experimental results. A two-resistance model under the framework of two-fluid model is employed to consider the mass and heat transfer across the steam-water interface. The steam plume transforms from contraction-cone into expansion-cone when steam mass flux rises from 500 to 900 kg/m2s, and the plume length gradually increases approximately linearly from 2.43de to 4.17de. When the steam mass flux is 900 kg/m2s, the expanding channel of the steam plume allows the jet to accelerate from sonic to supersonic with Ma = 1.43. At the transition of expansion to contraction, the steam dynamic pressure reaches a maximum and the steam total pressure decreases to a minimum. Because the water dynamic pressure is significantly higher than the steam dynamic pressure, the total pressure is maximum at the end of the two-phase region. Mass transfer is much higher in two-phase region than in other regions. The heat transfer coefficient calculated from the interface area decreases from 1.98 to 1.56 MW/m2K, and that calculated from the two-phase region volume increases from 3.37 × 103 to 4.05 × 103 MW/m2K.

Парирование нештатных ситуаций при пусках исследовательских баллистических ракет с созданием резервных условий входа объекта испытаний в атмосферу

The article is devoted to solving the problem of determining and implementing backup conditions for the research ballistic missiles entry with the test objects in the inflight emergency situations. A test object is understood as a descent vehicle entering the atmosphere and moving at the speed close to the first cosmic velocity. In emergency situations during launch and on the active trajectory leg, backup entry conditions are making it possible to carry out the guaranteed flight testing, albeit with less efficiency, but with exception of the launch emergency completion and complete failure in fulfilling the flight test tasks. Detailed study of this problem is quite suitable for practical implementation and goes far beyond the scope of this work, since it requires design studies, including aerodynamic, dynamic, thermal and strength calculations, as well as the development of additional onboard and prelaunch algorithms. This paper notes only certain main features in decision making to terminate or continue the flight after the emergency situations for а research ballistic missile with liquid rocket engines and solid propellant rocket engines. Mathematical apparatus of the external ballistic design is used to solve the problem.

Study on Measurement of Adsorption Capacity of Unsymmetrical Dimethylhydrazine Gas based on Stainless Steel

Unsymmetrical dimethylhydrazine (UDMH), as a high-energy liquid propellant, is widely used in aerospace, rocket, aircraft, and other fields. However, it also has certain toxicity, fire, and explosion risks, which will cause harm to the human liver, kidney, central nervous system, blood system, etc., especially the nervous system. UDMH is easy to be adsorbed on the surface of the human body or other substances, but there is a lack of research reports on the measurement of its adsorption capacity. In this paper, based on the principle of measuring gas adsorption capacity by the volumetric method, a set of UDMH gas adsorption capacity testing devices was built. In the experiment, 304 and 316L stainless steel materials were used as the adsorbent. Under the same experimental temperature and pressure conditions, the test bottle containing the adsorbent was filled with UDMH gas of different concentrations and fully adsorbed until saturation to explore the influence of 304 stainless steel surface roughness and 304 and 316L stainless steel materials on the adsorption capacity of UDMH gas under the same experimental conditions. The experimental results show that the adsorption capacity of 304 and 316L stainless steel materials to UDMH gas increases with the increase of UDMH gas concentration in the concentration range (0~100 ppm) studied in this paper. After polishing the surface of 304 stainless steel material, compared with the unpolished 304 stainless steel material under the same conditions, the adsorption capacity after polishing is significantly smaller, indicating that the larger the surface roughness of the adsorbent, the more adsorption capacity. Under the same conditions, the adsorption capacity of UDMH gas on 304 and 316L stainless steel materials is approximately equal. The experiment also proves that the adsorption of UDMH gas on stainless steel materials conforms to monolayer adsorption within the concentration range studied in this paper.

Development of a Liquid-Propellant Rocket Powered by a Rotating Detonation Engine

This paper presents work on a demonstrator rocket powered by a rotating detonation engine (RDE) fed by liquid propellants. Key to the success of the project was the development of a suitably efficient and lightweight RDE. After selecting the propellants: nitrous oxide () and propane (), laboratory tests were carried out on RDEs with different combustion chamber geometries. The conical geometry showed the best performance, and it was selected for further development; on this basis, the target RDE was designed and built in two versions: uncooled and regeneratively cooled. These were tested in laboratory conditions, but only the regeneratively cooled engine met the requirements. After successful laboratory testing of the engine, a demonstration rocket was designed and built. Static tests made in a vertical position confirmed that the rocket had sufficient operational performance (net thrust and total impulse). Ultimately, the liquid-propellant RDE-powered rocket made a successful flight. To the authors’ knowledge, it was the first liquid-fuel rocket in the world to take off and fly exclusively by means of RDE propulsion.

Visualization and Performance Evaluation of a Liquid-Ethanol Cylindrical Rotating Detonation Combustor

Rotating detonation combustors (RDCs) are among the combustors that use supersonic combustion waves known as detonation waves, and are expected to simplify engine systems and improve thermal efficiency due to their supersonic combustion and compression performance using shock waves. Research is also being actively conducted worldwide on a cylindrical RDC; a RDC without an inner cylinder, which is expected to simplify and downsize the combustor. However, most of the research was performed using gas propellants, and liquid propellants were rarely used. Since liquid propellants are used in many combustors, it is important to evaluate the performance of RDCs with liquid propellants. In this study, a cylindrical RDC with a liquid ethanol–gas oxygen mixture was constructed and tested at a flow rate of 31.5 ± 5.0 g/s, an equivalence ratio of 0.46–1.39, and a back pressure of 14.5 ± 2.5 kPa. The thrust was shown to depend strongly on the combustor bottom pressure history. In addition, the start-up process of the cylindrical RDC with liquid fuel was clarified by self-luminous and CH* radical visualizations. It was found that the detonation wavefront propagated at a distance of 2–3 mm from the combustor bottom, and the main combustion region was 10–15 mm in height.

Ersatzstoffe im Zeitalter der Weltkriege: Geschichte, Bedeutung, Perspektiven ed. by Elisabeth Vaupel

Reviewed by: Ersatzstoffe im Zeitalter der Weltkriege: Geschichte, Bedeutung, Perspektiven ed. by Elisabeth Vaupel Rouven Janneck (bio) Ersatzstoffe im Zeitalter der Weltkriege: Geschichte, Bedeutung, Perspektiven Edited by Elisabeth Vaupel. Munich: Deutsches Museum, 2021. Pp. 348. In 2002, the German historian of technology Ulrich Wengenroth published his controversial article, "Die Flucht in den Käfig." He argued that German innovation culture was decisively shaped by the two world wars, which led German science to focus on substitute materials even during peacetime and explained the lagging behind of German science after 1945. Th is view quickly met opposition that led to numerous research projects. The critical discussion of Wengenroth's thesis is the guideline of the present compilation on substitute materials in the age of the two world wars. Asking what was the lasting effect of research on substitutes and their uses in Germany between 1871 and 1945, Ersatzstoffe im Zeitalter der Weltkriege [Substitutes in the era of the world wars] consists of three parts that are instructively introduced by the volume's editor, Elisabeth Vaupel. The first part is dedicated to substitutes for ferrous and nonferrous metals. One of the challenges for the German war economy in World War I was a lack of the strategic metal copper. As Helmut Maier shows in his article on nonferrous metals, major efforts to find a replacement resulted in useful scientific findings in the field of steel production but did not produce an [End Page 276] economic alternative in times of peace. Therefore, Maier argues, the effective innovation and modernization push should be considered a transformation of the culture of innovation. The prevailing practical experience was replaced by scientification. This interpretation is shared by Andreas Zilt, who gives an overview of the endeavors to find a replacement for manganese or at least a way to economize its use, which resulted in an accelerated scientification of materials and process engineering in industry. Addressing the aspect of synthetic rubber, Peter Morris draws a different picture. In his view, World War I was not a crucial factor for the scientific development of this field. Only British attempts to control the world's natural rubber market in the 1920s pushed chemical companies to pick up the question of synthetic rubber again, even though its success remained doubtful for a long time. The contributions of Markus Raasch on liquid propellants and lubricants and Sandor Fehr on Chile saltpeter discuss substitutes for basic chemicals and chemical products. Raasch gives a comprehensive overview of the different approaches undertaken during World War I. In the long run, this led to the foundation of societies and university institutes that were dedicated to the issues of coal research and mineral oil synthesis. Ultimately, all efforts—even under the National Socialist autarky program—remained unsuccessful, because the expansion of science and industry overstretched the financial and economic power of the German Reich. This is not the case, however, with nitrogen synthesis. After a short presentation of the different approaches to synthesis, Sandro Fehr argues that World War I became a decisive innovation driver for the final success of the Haber-Bosch process. Nonetheless, its undisputed international triumph followed only after 1945. The field of luxury food, foodstuffs, and feedstuffs is the subject of the third part of the volume. In his detailed discussion of Coffarom, Claus Priesner presents the insightful case of the hunt for a synthesis of coffee flavor. Although a successful product could not be offered due to an erroneous economic assessment of the market and of the acceptance by customers, Priesner convincingly shows the persistent secondary effects of the undertaking. The most important one was that the research undertaken expanded the methods for classical organic microanalysis, which was essential for the achievements in many other fields such as hormones. Ulrike Thoms sheds light on the topic of the utilization of animal carcasses as animal feed with emphasis on the time of the Great War. Among the different methods applied, meat-and-bone meal prevailed as the dominant one. Its use was continued after the war and underwent a breakthrough after 1945, before it was prohibited at the end of the century. In summary, the book gives an instructive insight into the history...

EXPERIMENTAL INVESTIGATION OF UNLIKE TRIPLET SPRAYS USING HIGH-MAGNIFICATION SHADOWGRAPHY: INFLUENCE OF THE JETS VELOCITIES AND CENTRAL JET PROPERTIES

In this study, inert liquid sprays are generated by impinging two symmetric jets of water with a central jet of water, ethanol, or n-dodecane. This configuration, referred to as an unlike triplet injector, can be used in rocket engines to atomize liquid storable propellants, for instance, hydrogen peroxide oxidizer combined to a fuel. Here, the inert sprays are investigated in the so-called impact waves regime, which corresponds to jets a Weber number of higher than 1000. The atomization process is characterized using high-magnification shadowgraphy (HMS) from the impinging point of the jets into a sheet until it breaks up into ligaments and droplets. The HMS technique enables 10 kHz visualizations with an interframe of 4 μs and a spatial resolution up to 6.4 μm/pixel (1024 × 1024 pixels). Characteristic lengths of the primary atomization are measured: breakup length, apparent wavelength, and ligaments size. Similarly, the droplet populations are described based on arithmetic and Sauter mean diameters, shape, and velocity. Statistics of large droplet distributions are analyzed regarding the injection conditions and distance to the impingement point. Compared to like-doublet spray, the like-triplet evidences a slower atomization (longer breakup distance) and generates larger drops that require more distance to stabilize in size, centricity, and velocity. Unlike-triplet sprays exhibit a similar behavior to like-triplet spray while producing larger droplets, probably because of the fuel properties that stabilize the liquid sheet.

Validation of Soave–Redlich–Kwong equation of state coupled with a classical mixing rule for sound speed of non-ideal gas mixture of oxygen-hydrogen as liquid rocket propellants

Numerical simulations of inlet jets flow of propellants in the main combustion chamber equipped in a liquid rocket engine have been conducted by compressible CFD technics employing a van der Waals-type equation of state (EOS) and chemical reaction models. Various simulations have been already conducted both for combustion and non-combustion state in the chamber; however, the accuracy of EOS for the mixture of propellant employing a classical mixing rule (CMR), particularly for the sound speed, has not been understood well. Therefore, we have validated the applicability of Soave–Redlich–Kwong (SRK) EOS as one of the van der Waals-type EOSs coupled with the CMR for the sound speed using molecular dynamics (MD) simulations against an imaginary model of oxygen-hydrogen mixture system. We found that SRK EOS coupled with a well-employed CMR can reproduce the sound speed in the MD simulations within a relative error of several percent and that the CMR hardly increases the deviation of the SRK EOS in the single component. The present results suggest that the SRK EOS with the CMR cannot be the main factor to cause critical errors in the CFD based on RANS, which will give reliability to current CFD simulations for internal flows in a combustion chamber of a liquid rocket engine.

Choice of the Optimum Design of Lateral PMD Using the CFD Method

Residues of propellant components in the power system of the propulsion system, at the end of the operation of the launch vehicle, to a large extent affect its energy characteristics. Propellant management devices (PMD), which are equipped with tanks of modern launch vehicles, provide a continuous supply of liquid propellant components from the tank to the propulsion system without disturbing the continuity of the flow and minimize of the residues of the propellant components. In the tank of a launch vehicle, the presence of a tunnel pipeline complicates, and in certain cases excludes the possibility of taking from the pole of the tank. In this case, the use of a lateral PMD allows solving the problem of propellant intake. The authors carried out a search and justification for the optimal design of the PMD using the example of the fuel tank of the first stage of the "Cyclone-4" launch vehicle, which is equipped with an PMD in the form of a profiled plate. The designs of the siphon and annular PMD are considered. An analytical calculation using empirical dependences, a physical experiment and numerical simulation of their main parameters was carried out. The result of the experimental and computational-analytical work was the determination of the most optimal variant of the PMD, which, according to several parameters, turned out to be a siphon PMD. The introduction of a more advanced siphon PMD into the design of the fuel tank of the "Cyclone-4" launch vehicle will improve the energy characteristics of the launch vehicle by increasing the weight of the output payload by 5.4 kg.

An environment friendly electrochemical synthesis of 1,1,4,4-tetramethyl-2-tetrazene energetic materials from undimethylhydrazine.

As a prospective alternative liquid propellant, 1,4,4-tetramethyl-2-tetrazene (TMTZ) possesses high enthalpy of formation and environment friendly decomposition products, and shows a promising application prospect in aerospace, munitions manufacturing, etc. An environment friendly and convenient synthesis of TMTZ through electrochemical oxidative coupling of undimethylhydrazine (UDMH) on commercially procured electrodes was carried out under mild conditions, in which the purity is up to 98.5% with a yield of over 45%. It is a simple, clean and suitable method for industrial production in contrast with the previously reported conventional chemical oxidation syntheses.

Technology for Obtaining Tangential Holes in the Shell of the Combustion Chamber of a Liquid Propellant Rocket Engine

Method of obtaining tangential holes in the shell of a combustion chamber of liquid-propellant rocket engine is presented in this article. Advantages and disadvantages of technologies for making small diameter holes are consired. The developed technology and tooling made it possible to obtain small diameter holes designed to swirl the coolant flow in the veil belt of the combustion chamber shell. As a result, material and labor costs were reduced in the manufacture of engine components.

Isomerization and reaction process of N2O4(H2O) n.

Liquid propellant N2O4 is prone to absorb H2O to form an N2O4(H2O) n system during long-term storage, ultimately generating HNO3, HNO2, and other substances capable of corroding the storage tank, which will adversely affect the performance of weapons and equipment. In this work, the reaction process of the N2O4(H2O) n system is simulated using density functional theory, and the potential energy surface, the geometric configurations of the molecules, the charge distribution, and the bond parameters of the reaction course at n = 0-3 are analyzed. The results show that the potential energy of the system is lower and the structure is more stable when the H2O in the N2O4(H2O) n system is distributed on the same side. When n = 1 or 2, the reaction profiles are similar, and the systems are partly ionic, although still mainly covalently bonded. When n = 3, the charge on the trans-ONONO2 group and the ON-ONO2 bond length change abruptly to -0.503 a.u. and 2.57 Å, respectively, at which point the system is dominated by ionic bonds. At n = 2, a proton-transfer phenomenon occurs in the reaction course, with partial reverse charge-transfer from NO3 - to NO+, making the ON-ONO2 bond less susceptible to cleavage, further verifying that N2O4(H2O) n tends to afford the products directly in one step as H2O accumulates in the system.

Tapered LADs: Acquiring Cryogenic Liquid Propellants in Deep Space

To carry out complex manoeuvres such as orbit insertion, large spacecraft on long voyages must carry tanks of liquid propellants, kept at ultra-cold temperatures. In existing designs, however, heat leaking into these tanks can form unwanted vapour bubbles in the channels required to extract their contents – which are especially difficult to remove in the microgravity environment of deep space. In their research, a team at the Southwest Research Institute presents a simple solution to this problem – through which the sides of these extraction channels are tapered, allowing vapour bubbles to escape. Results from recent microgravity testing of this technology could lead to exciting new opportunities for future space missions.

Conceptual Design of Small-Sized Thruster Using Laser Ignition of High-Energy Monopropellant

Ammonium dinitramide (ADN)-based energetic ionic liquid propellants (ADN-EILPs) present considerable potential as monopropellants due to high energy density, high thermal/chemical stability, and low toxicity. Consequently, a chemical thruster system based on ADN-EILPs can be employed in the development of high-performance ultrasmall/small satellites. However, the characteristics of the ADN-EILPs present various problems in their ignition during the thruster development. To solve this problem, the authors have previously achieved the continuous-wave (CW) laser ignition of ADN-EILPs using laser absorbers composed of carbon wools. However, the conventional propellant injection of ADN-EILPs with carbon wool using high-pressure gas faces several limitations. Therefore, a propellant feed system suited for the ignition method is proposed here, as well as a conceptual model of a 0.5 U/0.5 N-class thruster operated by the CW laser ignition of ADN-EILPs (). Additionally, an attempt is made to manufacture a laboratory model (LM) thruster, and its fundamental operation properties are determined. The future research implications of this study include the further observation of the combustion of the decomposed gas before its emission from the throat of the LM thruster, along with the further development of the propellant feeding system proposed in this study and the hot-fire tests performed for the feeding systems.

Effect of Microwave Power and Gas Flow Rate on the Combustion Characteristics of the ADN-based Liquid Propellant

As a new type of energy-containing material, Ammonium dinitramide based liquid propellant has the advantages of being green, having low toxicity, good stability, and high safety performance. Traditional catalytic combustion methods require preheating of the catalytic bed and deactivation of the catalytic particles at high temperatures, while microwave ignition methods can effectively solve these problems. To study the combustion characteristics of ADN-based liquid propellants during microwave ignition, the influence of microwave power and gas flow rates on the combustion process are analyzed using experimental methods. A high-speed camera was used to observe the enhanced effects of microwave power and gas flow on plasma and flame. Combined with temperature measurement, the combustion process of ADN-based liquid propellants under the action of plasma was analyzed. The combustion process in the presence of microwaves was observed by comparing parameters such as flame length, flame temperature, and radical intensity. Those results show that, with the increase in microwave power, the luminous burning area of the flame grows significantly. The microwave power is increased by 250 W each, and the flame jet length is increased by nearly 20%. The increase in microwave power also leads to an increase in propellant combustion temperature, however, this increase gradually slows down. At a gas flow rate of 20 L/min, the ADN-based liquid propellant showed the best combustion performance with a maximum jet length of 14.51 cm and an average jet length increase of approximately 85.9% compared to 14 L/min. Too much gas flow rate will hinder the development of the jet, while the high-velocity airflow will have a cooling effect on the flame temperature. The results provide a basis for the specific parameter design of microwave ignition and promote the application of ADN-based liquid propellants in the aerospace field.

Effect of absorption depth on chemical energy release from laser ablation of ADN-based liquid propellants

Ammonium dinitramide is a new green oxidant, which has been widely used in the field of liquid propulsion. In order to study the influence of doping laser absorber on the propulsion performance of liquid targets, the mixed solution of ammonium dinitramide and ionic liquid 1-allyl-3-methylimidazolium dicyandiamide was used as the ablation target, and the infrared dye was used as the laser absorber to change the doping content of infrared dye and laser energy density. The results show that the light absorption performance of liquid propellant is obviously improved with the increase of infrared dye content. The absorption coefficient and absorption depth of liquid propellant with infrared dye content of 0.6wt% are 425.19 cm−1 and 23.52 μm, respectively. The propellant with lower absorption depth produces high values of impulse bit, specific impulse, impulse coupling coefficient and ablation efficiency under the ablation of high laser energy density. The propellant sample doped with 0.6wt% infrared dye yielded the highest impulse bit of 114.32 μN·s, largest specific impulse of 84.14 s, highest impulse coupling coefficient of 1.07 mN·s·J−1, and the maximal ablation efficiency of 44% at the laser energy density of 21.51 J·cm−2. Furthermore, the effects of laser energy density and absorption depth on the chemical energy release of liquid propellant were studied. It was found that the maximum contribution of chemical energy to kinetic energy of ammonium dinitramide based liquid propellant is 93.93%. In general, improving the absorption performance of propellant can significantly enhance the energy release of energetic propellant. Which has guiding significance for propellant design and selection.