A validated numerical model of spark channel expansion was used to investigate the spark channel expansion in a high-pressure hydrogen–oxygen mixture and in nitrogen. The model considers electric ...circuit parameters, gas-dynamic expansion processes, thermal gas ionization, non-equilibrium chemical reactions, vibrational excitation of molecules in a shock wave, electron heat transfer, and radiation. A discharge circuit with specific values of inductance (740 nH), resistance (0.2444
Ω
)
, and capacitance (0.1983
μ
F) was used to calculate a direct detonation initiation in a stoichiometric hydrogen–oxygen mixture at an initial temperature and pressure of 300 K and 0.3 MPa, respectively. A circuit with 2
μ
H inductance, 1
Ω
resistance, and 0.1
μ
F and 0.01
μ
F capacitance was applied to calculate spark expansion in molecular nitrogen with an initial temperature of 300 K and varied initial pressure of 0.1 to 2 MPa. The effect of the spark discharge process on the direct detonation initiation was subsequently considered. It was determined that when a detonation failure occurs, the intensity of the spark-generated shock wave can exceed the intensity causing the detonation initiation. But a failure takes place because the intensity is high only before the detachment of the shock wave from the spark current-conductive channel where the chemical energy is not released due to high gas temperature (above 10,000 K). The inaccuracy of the method of evaluation of spark energy calculated by experimentally measured current and the average spark resistance was also discussed. The influence of initial pressure on the thermodynamic parameters of gas flow, electrical conductivity, discharge current, spark resistance, deposited energy, and component concentration was investigated. The relationship between initial pressure and the deposited energy balance was determined. In considering the influence of the initial pressure on the discharge process, it was determined that an increase in pressure causes an increase in the spark energy transforming into gas flow energy with an efficiency of about 8 % in the first half-period of the discharge.
Based on the new design concept in VGT the commercial turbocharger with vaneless turbine volute and two gas inlet casings was converted to an adjustable one. Modification assumed the processing of ...turbine housing and installation of the specially designed mechanism of adjustment. Prototype of variable geometry turbocharger with two gas inlet casings can be installed on V-type engine in the way when each row of cylinders will deliver exhaust gases to one of the gas inlet casting. In the new design concept the elements of adjustment was profiled in a special way to ensure the adjustment with maximum effectiveness. Adjustable turbocharger was tested on a motorless test bench and characteristics of variable geometry turbine were analyzed in a wide range of the gas flow rates. Only small fluctuations in turbine efficiency during adjustment were detected that is evidence of high gas dynamics performance of VGT. Based on experimental data the possibility to improve engine indices that are most impacted when VGT is used was made. Improvement of torque and power characteristics of diesel engine when turbocharger adjustment with vaneless turbine volute is used also presented.
NiO-Al
2
O
3
and Co
3
O
4
oxide catalysts modified with palladium and oxides of rare earth metals (Ce and La) and formed on structured cordierite supports have been studied in the process of methane ...oxidation at different O
2
/CH
4
ratios. It is shown that methane oxidation proceeds without the formation of CO even at an O
2
/CH
4
ratio of < 2 (in contrast to nickel-containing catalysts) in the presence of cobalt-containing catalysts modified with cerium and lanthanum oxides. The addition of CeO
2
promotes Co
3
O
4
dispersion, increases the number of oxygen vacancies, and prevents agglomeration of the active phase of the catalyst at high temperatures. The modification of Co
3
O
4
-CeO
2
/cordierite with palladium (0.1%) enhances its activity due to increased surface oxygen mobility as a result of the interphase interaction of palladium with cobalt oxides and ceria (according to the TPR-H
2
and XPS data).
Sensitivity of EEHG simulations to dynamic beam parameters Samoilenko, D; Hillert, W; Pannek, F ...
13th International Particle Accelerator Conference, IPAC 2022,Bangkok, Thailand,2022-06-12 - 2022-06-17,
01/2023, Letnik:
2420, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Abstract
Currently, the Free electron laser user facility FLASH at DESY is undergoing a significant upgrade involving the complete transformation of one of its beamlines to allow external seeding. ...With the Echo-Enabled Harmonic Generation (EEHG) seeding method, we aim for the generation of fully coherent XUV and soft X-ray pulses at wavelengths down to 4 nm. The generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile imprinted either deliberately or by collective effects such as Coherent Synchrotron Radiation (CSR). In dedicated particle tracking simulations, one usually makes certain assumptions concerning the beam properties and the collective effects to simplify implementation and analysis. Here, we estimate the influence of some of the common assumptions made in EEHG simulations on the properties of the output FEL radiation, using the example of FLASH and its proposed seeding beamline. We conclude that the inherent properties of the FLASH1 beam, namely the negatively chirped energy profile, has dominant effect on the spectral intensity profile of the radiators output compare to that of the CSR induced chirp.
The aim of the work is to study the influence of the length of the spark gap on energy input into the discharge channel during its gas-dynamic expansion. Methodology. The research is carried out by ...numerical modeling of the process of spark discharge development at variable values of the discharge gap length and at invariable other discharge conditions. The length of the gap was set in the range from 1 mm to 20 mm. The study was conducted using a numerical model of spark development, which takes into account the processes of nonstationary gas-dynamic expansion of the spark channel, the transient process in the electric circuit, nonequilibrium chemical processes, gas ionization, heat transfer and electrons thermal conductivity. The simulation was performed in atmospheric pressure nitrogen. The calculation was performed for various parameters of the RLC circuit, such as capacitance, inductance, resistance and voltage across the capacitor. Results. The study evaluates the influence of the spark length on the discharge current, the resistance of the spark channel, the energy deposited in the spark channel, and the distribution of thermodynamic parameters of the gas during the development of the spark discharge. It is confirmed that increasing the length of the gap increases the resistance of the spark. The deviation from the linear relationship between the deposited energy or the radiated energy and the length of the spark gap is estimated. Scientific novelty. A linear relationship between the gap length and the deposited energy is revealed when the total energy is above tens of Joules. Deviations from the linear dependence were detected in the discharge circuit when the total energy is below one of Joules. Practical value. The research results allow predicting the effect of the spark gap length on the energy input into the discharge channel under conditions of a slight change in the discharge current. In the conditions of essential change of amplitude of discharge current it is expedient to apply numerical researches for specification of changes in the energy deposited into a spark discharge.
The article discusses the applicability of the theory of disasters and nonlinear dynamics in predicting the systemic risks of managing the digital economy and Internet of things systems. One of the ...approaches may be modeling of nonlinear processes based on the use of the concepts of catastrophe theory. Studies have shown a key indicator of such modeling is to determine the essential features of the disaster. The study showed that the widely used models of the economic processes of the digital economy, as well as the software and technical components of the internet of things, can be transformed into the canonical equation of «assembly», which subsequently leads to the emergence of such an area in the space of phase development variables in which jumps can occur or for the better, or vice versa, such as a collapse. Currently, in the digital economy, the study of such phenomena seems to be very relevant, since an uncontrolled «spasmodic» change in the functioning parameters of such systems can lead to disastrous consequences for the functioning of all interconnected subsystems. The collapse or unstable behavior of one of the components of such systems can lead to the collapse of the entire system. Such phenomena are not allowed in the digital economy and can trigger not only economic consequences, but also social ones.
The work is devoted to one of the aspects related to the resolution of disputes over the boundaries of land plots. Recently, the number of these disputes has been steadily growing, which confirms the ...relevance of the chosen topic. Border disputes are currently resolved only through the courts, almost always with a forensic land surveying. The aspect considered in the article concerns the accuracy of constructing models of the objects of surveying, since software products used do not have documentary evidence of the accuracy of the created models. Therefore, experts need to independently test the models for accuracy. Moreover, such tests make it possible to reveal expert errors at the modeling stage. The paper proposes the authors’ method of testing for the accuracy of a computer-graphic model of objects, studied by a forensic land surveying.
Based on experimental data, the present study investigates the influence of turbine adjustment in a turbocharger with vaneless turbine volute on diesel combustion efficiency indices and emission ...characteristics. Experimental investigations were conducted on engine modes as set out by the European Stationary Cycle (ESC). The adjustment algorithms selected for the experiment under ESC modes included adjustment to achieve minimal values of specific fuel consumption (SFC), NOx, CO and particulate matter (PM). In present research only VGT adjustment was investigated, the factors like fuel injection timing and EGR were not investigated. As a result we were able to make a comparison of the engine combustion efficiency and emission indices for VGT and a common turbocharger running on ESC cycle modes.
The article presents selected results of experimental research of the compression ignition engine running on a new type of Fatty Acid Methyl Esters fuel and on a comparative standard fuel which is ...diesel oil. As a part of the test assessment, the waveforms and maximum values of pressure and temperature of the working medium in the combustion chamber under the same operating conditions of the engine supplied with the mentioned fuels were compared. Moreover, the phases of the combustion process were determined together with the exact determination of the share of the amount of heat released in each phase. New data is presented as analyzed and evaluated the tests results. Thus, it was established that the amount of heat released in the afterburning phase, for FAME type fuel, has reached higher values compared to standard fuel. Empirical studies were carried out in the Combustion Engines Laboratory at Institute of Vehicles, Warsaw University of Technology. For this purpose, the experimental stand equipped with a CI engine and AVL IndiSmart system that has an ability of registration of fast-changing parameters was used. An experimental setup has AVL Concerto software that was utilized for analysis.
The action of sulfur diethylaminotrifluoride on 19β,28-epoxyoleanan-3-ol (allobetulin) causes dehydration of the terpenoid and isomerization of the ring A via its contraction to isopropylcyclopentene ...ring resulting in 19β,28-epoxy-A-
neo
-18α-olean-3(5)-ene (α-allobetulin) in a high yield.
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