The paper presents the results of a numerical study of gas dynamics and integral parameters of the flow at the channel entrance located behind a conical or plane shock wave. The freestream Mach number range is M = 2–4 and the range of the angles of the compression surfaces of the wedge and cone is δ= 10–90°. Data on the flow structure at the channel entrance, mass-averaged Mach numbers, total pressure loss coefficient, and flow rate coefficients are obtained. A comparative analysis of these parameters is performed, and the advantages and drawbacks of the channel entrance positions in various types of the flow are noted.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation S. M. Aulchenko, V. I. Zvegintsev, S. M. Frolov; Numerical simulation of solid hydrocarbon material pyrolysis in a flow of hot inert gas. AIP Conference Proceedings 16 February 2023; 2504 (1): 030002. https://doi.org/10.1063/5.0132714 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation V. I. Zvegintsev, D. A. Vnuchkov, S. V. Lukashevich; Use of diffusers to increase the run time of a wind tunnel with a vacuum tank. AIP Conference Proceedings 16 February 2023; 2504 (1): 030072. https://doi.org/10.1063/5.0133155 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The traditional approach to measuring the thrust of air-breathing jet engines (ABJEs) was proposed by B.S. Stechkin in 1929. In this approach, the thrust is determined as the difference between the momenta of the gas flows at the engine inlet and outlet. This approach involves some methodological and terminological problems. Based on the critical analysis of available concepts, the present article proposes a new approach to the determination of ABJE thrust in the form of the reduction of the initial drag of the aircraft + ABJE assembly observed when the propulsion system operates with fuel supply and energy release. For the thrust thus obtained, we propose using the term “real thrust”. It is shown that the proposed approach eliminates terminological problems and simplifies the technique for measuring the thrust characteristics of ABJEs. The paper considers various options in applying the proposed approach to the determination of the “real thrust” for different cases of using and modeling ABJEs, including the calculation of flight trajectories of ABJE-powered aircraft.

An experimental study of the flow of air from a container through throttling tubes of various configurations with characteristic times from 0.6 to 9 s was carried out. The equivalent container-outlet area was determined based on the ratio of the length of the throttling tube to its nominal diameter. It was found that during the outflow, the gas temperature inside the container decreased by 10–15

Based on the hypothesis of quasi-stationarity, relations were obtained for calculating the unsteady process of filling a vacuum vessel with a gas. As a criterion for the completion of the filling process, the admissible degree of pressure increase in the vacuum vessel was adopted. An analysis was made of the possibilities of increasing the duration of the filling process for a vacuum vessel of a given volume.

A semi-empirical method is proposed for determining the rate of gas production in a flow-through gas generator (GG) with the allocation of a part of the gas flow produced by gasification of a low-melting solid material (LSM) in the total gas flow rate through the GG. The method is verified by test fires with polypropylene sample gasification by hot air under conditions of incoming supersonic flow with Mach number 2.43, 2.94, and 3.81 and stagnation temperature 600–700 K. The mean flow rates of gasification products obtained in test fires were 0.08 kg/s at Mach 2.43, 0.10 kg/s at Mach 2.94, and 0.05–0.02 kg/s at Mach 3.81. For obtaining 1 kg of gasification products in the test fires there was a need of 1.61 to 2.86 kg of gasifying agent.

Pulsed and continuous detonation of motor fuel o¨ers the most ef- ¦cient fuel utilization in combustion process and allows increasing the e©ciency of jet engines by achieving a lower entropy of expanded combustion products compared to the conventional combustion process at constant pressure [1]. In the last two decades, research and development work aimed at creating various types of jet engines with controlled detonation of motor fuel has been actively carried out worldwide. The paper will provide the thorough analysis of patents on the various designs of pulsed detonation (Fig. 1) and continuous-detonation (Fig. 2) engines as well as the various methods for organizing the operation process in such engines. The main research and technical problems of creating practical detonation engines are identi¦ed. These include low detonability of standard motor fuels, thermal protection and cooling, cyclic loads, vibrations, and noise. The most promising approaches to solving some of these problems have been reported and discussed. Thus, for enhancing fuel detonability in terms of shortening de§agtation-to-detonation (DDT) run-up distance and time, the concept of fast DDT [4] can be used. However, despite some progress in this ¦eld of science and technology, most of the problems have not yet been fully resolved.

The conceptual design of a hydrogen/ethylene fueled detonation ramjet (DR) studied earlier is updated based on numerical simulations and test fires at airflow Mach numbers 1.5, 2.0, and 2.5. The goal of the design update is to increase the operation stability, reduce aerodynamic drag, and improve thrust performance at continuous detonation of hydrogen/ethylene in the DR combustor. The updated DR is fabricated and tested. The thrust performance of the updated DR is increased significantly. At on-design M=2.0, the range of stable operation of hydrogen fueled DR combustor is expanded in terms of the air-to-fuel equivalence ratio from 1.6 to 3.3. At the air-to-fuel equivalence ratio of 3.1, the fuel-based specific impulse reached 4760 s. The maximum value of total thrust is 1000 N. At off-design M=1.5 and 2.5, the fuel-based specific impulse / total thrust attained 2780 s / 740 N, and 3780 s / 1160 N, respectively. Replacement of hydrogen by ethylene leads to the significant narrowing of the DR stable operation domain: continuous-detonation of ethylene–air mixture is registered only for near-stoichiometric mixtures.

The slagging of heating surfaces by fly ash significantly complicates the long term operation of solid-fuel boilers. Gas pulse technologies offer a potentially convenient, inexpensive, yet efficient way for online slag deposits removal. The creation and application of real boiler cleaning systems using gas pulse technologies is a relatively new direction in the energy sector and requires scientific research on various aspects. In this work, the numerical investigation of the gas-dynamic flow arising when the package of heat-exchange tubes is blown with single air jet created by a pneumopulse cleaning system has been carried out. The forces acting on the heat-exchange tubes located at distances 1.0 m and 2.0 m from the exhaust nozzle with various configurations of tubes in the package have been determined. It is shown that an increase in the pressure of the generated air jet makes it possible to significantly increase the acting forces at large distances from the exhaust nozzle. The results of this study and similar calculations for real geometry will increase the validity of engineering solutions used in the development of pneumopulse cleaning systems for large power boilers.

A procedure of mathematical modeling of the characteristics of gasification of a low-melting hydrocarbon material in the flow of a heated inert gas has been proposed which is based on solving the problem of coupled heat transfer in the gas in the channel and in the region occupied by the solid hydrocarbon material. Dependences of the shape of the boundaries of the solid material on the temperature of a carrier gas and on time have been obtained. Calculation results are compared with experimental results.

The detonability of polyethylene pyrolysis products (pyrogas) in mixtures with air is determined for the first time in a standard pulsed detonation tube based on the measured values of deflagration-to-detonation transition run-up time. The pyrogas is continuously produced in a gas generator at decomposition temperatures ranging from 650 to 850 °C. Chromatographic analysis shows that at a high decomposition temperature (850 °C) pyrogas consists mainly of hydrogen, methane, ethylene, and ethane, and has a molecular mass of about 10 g/mol, whereas at a low decomposition temperature (650 °C), it mainly consists of ethylene, ethane, methane, hydrogen, propane, and higher hydrocarbons, and has a molecular mass of 24–27 g/mol. In a pulsed detonation mode, the air mixtures of pyrogas with the fuel-to-air equivalence ratio ranging from 0.6 to 1.6 at normal pressure are shown to exhibit the detonability close to that of the homogeneous air mixtures of ethylene and propylene. On the one hand, this indicates a high explosion hazard of pyrogas, which can be formed, e.g., in industrial and household fires. On the other hand, pyrogas can be considered as a promising fuel for advanced propulsion powerplants utilizing the thermodynamic Zel’dovich cycle with detonative combustion, e.g., solid-fuel detonation ramjets. In view of it, the novel conceptual design of the dual-duct detonation ramjet demonstrator intended for operation on pyrogas at the cruising flight speed of Mach 2 at sea level has been developed. The ramjet demonstrator has been manufactured and preliminarily tested in a pulsed wind tunnel at Mach 1.5 and 2 conditions. In the test fires, a short-term onset of continuous detonation of ethylene was registered at both Mach numbers.

The conceptual design of the hydrogen-fueled detonation ramjet (DR) of a new type for a cruising flight speed of Mach 2 at sea level is developed using 3D numerical simulations of the operation process. The calculated effective thrust of such a DR is shown to become positive at M = 1.3, i.e., the startup Mach number for such a DR can be lower than M ≈ 2.0, which is typical for ramjets operating on continuous-deflagration combustion. A DR demonstrator is designed and manufactured. Its test fires are performed in a blowdown wind tunnel (WT) at free air jet Mach numbers M = 2.0, 1.5, and 0.9. The result of test fires is the experimental proof of the possibility of arranging stable continuous-detonation combustion of hydrogen in the DR of the developed design at both Mach numbers exceeding 1.0. The maximum measured values of the fuel-based specific impulse and total thrust were 1610 s and 650 N for the tests with M = 1.5 and 1630 s and 860 N for the tests with M = 2.0.

The conceptual design of a hydrogen-fueled detonation ramjet (DR) of a new type for a cruising flight speed of Mach 2 at sea level is developed using multivariant three-dimensional (3D) numerical simulations of the operation process. The possibility of arranging the continuous-detonation (rotating or longitudinally pulsating) combustion of hydrogen in an expanding annular combustor of the DR is proved for the first time. 3D numerical simulations of the operation process in the DR for flight conditions with a Mach number M ranging from 1.1 to 2.7 are performed. The calculated effective thrust of such a DR is shown to become positive at M = 1.3, i.e., the startup Mach number for such a DR can be lower than M = 2.0, which is typical for ramjets operating on continuous-deflagration combustion. A DR demonstrator is designed and manufactured. Its test fires are performed in a pulsed wind tunnel (WT) at free air jet Mach numbers M = 2.0 and M = 1.5. The most important result of test fires is the experimental proof of the possibility of arranging stable continuous-detonation combustion of hydrogen in the DR of the developed design at both Mach numbers.

The conceptual design of a hydrogen-fueled dual-duct detonation ramjet (DR) of a new type for a cruising flight speed of Mach 2 at sea level is developed using multivariant three-dimensional (3D) numerical simulations of the operation process. The possibility of arranging the continuous-detonation (rotating or longitudinally pulsating) combustion of hydrogen in an expanding annular combustor of the DR is proved for the first time. The calculated effective thrust of such a DR is shown to become positive at M = 1.3, i. e., the startup Mach number for such a DR can be lower than M = 2.0 which is typical for ramjets operating on continuous-deflagration combustion. A DR demonstrator is designed and manufactured. Its test fires are performed in a pulsed wind tunnel (WT) at free air jet Mach numbers M = 2.0 and 1.5. The most important result of test fires is the experimental proof of the possibility of arranging stable continuous-detonation combustion of hydrogen in the DR of the developed design at both Mach numbers.

Предложена методика экспериментального определения расходных характеристик проточного газогенератора с выделением части расхода, создаваемой за счет газификации твердого легкоплавкого материала (ТЛМ) в суммарном расходе газа, выходящего из газогенератора. Проведены эксперименты по газификации образца полипропилена в проточном газогенераторе с набегающим сверхзвуковым потоком воздуха, нагретом в огневом подогревателе. Средний по времени расход продуктов газификациисоставил 0,080 кг/с (при числе Маха набегающего потока M = 2,43), 0,100 кг/с (при M = 2,94) и 0,050- 0,020 кг/с (при M = 3,81). Отношение суммарного расхода втекающего воздуха к суммарному выходу продуктов газификации полипропилена составило 1,61-2,86.

Предложена методика экспериментального определения расходных характеристик проточного газогенератора, работающего на газификации твердого легкоплавкого материала (ТЛМ) набегающим потоком воздуха. Проведены экспериментальные исследования газификации заряда полипропилена (ПП). В экспериментах выход продуктов газификации составил от 43 до 120 г/с, а соотношение расходов воздуха и продуктов газификации ПП составило 2,3-2,9. Выполнен анализ погрешностей при использовании методики в реальных экспериментах.

A new and intuitive method for evaluating the efficiency of the compression process in a supersonic air intake is proposed. The method is based on a comparison of the geometric compression ratio of the flow tube in the air intake under consideration with the maximum possible isentropic compression. It is shown that a higher value of the geometric compression ratio in the air intake allows obtaining higher thrust characteristics, with other conditions being identical.

The term "detonability" with respect to fuel-air mixtures (FAMs) implies the ability of a reactive mixture of a given composition to support the propagation of a stationary detonation wave in various thermodynamic and gasdynamic conditions. The detonability of FAMs, on the one hand, determines their explosion hazards during storage, transportation, and use in various sectors of the economy and, on the other hand, the possibility of their practical application in advanced energy-converting devices operating on detonative pressure gain combustion.