Mixing and flameholding in supersonic combustor by electrical discharge

Compared to a basic scramjet design, operation of scramjet combustors using plasma assisted ignition and flameholding offers considerably more flexibility over the choice of its geometry, due to replacing mechanical flameholders with a highly effective electrically driven apparatus. The articlce presents the results of an experimental study of supersonic combustor operation enhanced by an electrical discharge. A novel scheme of plasma assisted mixing, ignition, and flameholding is demonstrated, which combines a wall fuel injector and a high-voltage electric discharge into a single module. The experimental combustor with the cross-section of 72 mm (width) ´ 60 mm (height) and length of 600 mm operates at a Mach number of M = 2, initial stagnation temperature of airflow of T0 = 290–300 K, and stagnation pressure of P0 = 1.3–2.0 Bar. The combustor is equipped with four plasma ignition modules, flush-mounted side-by-side on the plane wall of the combustion chamber. The combustion tests were performed using ethylene injection with a total mass flow rate of GC2H4 \u3c 10 g/s and discharge power in the range of Wpl = 3 – 24 kW. The scope of the experiments includes characterization of the discharge interacting with the main flow and fuel injection jet, parametric study of ignition and flame front dynamics, and comparison of this scheme to earlier tested configuration. This approach demonstrates a significant advantage in terms of flameholding limits. An operation mode with strong combustion oscillations was observed at high fuel injection flow rates. Methods of flame front stabilization based on plasma application are discussed. The technique studied in this study may have significant potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode and off-design operation

Resolving Structural Vibration Issues On a Water Flood Pump

Case Stud

Function of the ribosomal E-site: a mutagenesis study

Ribosomes synthesize proteins according to the information encoded in mRNA. During this process, both the incoming amino acid and the nascent peptide are bound to tRNA molecules. Three binding sites for tRNA in the ribosome are known: the A-site for aminoacyl-tRNA, the P-site for peptidyl-tRNA and the E-site for the deacylated tRNA leaving the ribosome. Here, we present a study of Escherichia coli ribosomes with the E-site binding destabilized by mutation C2394G of the 23S rRNA. Expression of the mutant 23S rRNA in vivo caused increased frameshifting and stop codon readthrough. The progression of these ribosomes through the ribosomal elongation cycle in vitro reveals ejection of deacylated tRNA during the translocation step or shortly after. E-site compromised ribosomes can undergo translocation, although in some cases it is less efficient and results in a frameshift. The mutation affects formation of the P/E hybrid site and leads to a loss of stimulation of the multiple turnover GTPase activity of EF-G by deacylated tRNA bound to the ribosome

NUMERICAL METHODS FOR SOLVING PROBLEMS WITH CONTRAST STRUCTURES

In this paper, we investigate the features of the numerical solution of Cauchy problems for nonlinear differential equations with contrast structures (interior layers). Similar problems arise in the modeling of certain problems of hydrodynamics, chemical kinetics, combustion theory, computational geometry. Analytical solution of problems with contrast structures can be obtained only in particular cases. The numerical solution is also difficult to obtain. This is due to the ill conditionality of the equations in the neighborhood of the interior and boundary layers. To achieve an acceptable accuracy of the numerical solution, it is necessary to significantly reduce the step size, which leads to an increase of a computational complexity. The disadvantages of using the traditional explicit Euler method and fourth-order Runge-Kutta method, as well as the implicit Euler method with constant and variable step sizes are shown on the example of one test problem with two boundaries and one interior layers. Two approaches have been proposed to eliminate the computational disadvantages of traditional methods. As the first method, the best parametrization is applied. This method consists in passing to a new argument measured in the tangent direction along the integral curve of the considered Cauchy problem. The best parametrization allows obtaining the best conditioned Cauchy problem and eliminating the computational difficulties arising in the neighborhood of the interior and boundary layers. The second approach for solving the Cauchy problem is a semi-analytical method developed in the works of Alexander N. Vasilyev and Dmitry A. Tarkhov their apprentice and followers. This method allows obtaining a multilayered functional solution, which can be considered as a type of nonlinear asymptotic. Even at high rigidity, a semi-analytical method allows obtaining acceptable accuracy solution of problems with contrast structures. The analysis of the methods used is carried out. The obtained results are compared with the analytical solution of the considered test problem, as well as with the results of other authors

Spiral spin-liquid and the emergence of a vortex-like state in MnSc2_2S4_4

Spirals and helices are common motifs of long-range order in magnetic solids, and they may also be organized into more complex emergent structures such as magnetic skyrmions and vortices. A new type of spiral state, the spiral spin-liquid, in which spins fluctuate collectively as spirals, has recently been predicted to exist. Here, using neutron scattering techniques, we experimentally prove the existence of a spiral spin-liquid in MnSc$_2$S$_4$ by directly observing the 'spiral surface' - a continuous surface of spiral propagation vectors in reciprocal space. We elucidate the multi-step ordering behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase on application of a magnetic field. Our results prove the effectiveness of the $J_1$-$J_2$ Hamiltonian on the diamond lattice as a model for the spiral spin-liquid state in MnSc$_2$S$_4$, and also demonstrate a new way to realize a magnetic vortex lattice.Comment: 10 pages, 11 figure

Determination of measurement errors when testing YAMZ engines

Internal combustion engine testing after repair work is a modern and up-to-date type of repair quality analysis. Normalization of measurement errors of controlled quantities plays an important role in the process of testing and checking engine parameters. The article defines the measurement errors of a number of values controlled during the testing of YAMZ diesel engines, which allow you to select the appropriate control and measuring devices. Formulas and equations used to process the data obtained during the tests are also considered. The list of controlled parameters has been updated based on the current standards

The Problem of Experimental Evaluation for Corona Resistance of VFD Cables

This article describes an approach for evaluating experimental cable insulation resistance electro-thermal aging, typical for the drive frequency being adjusted. It estimates the average time until the insulation breakdown when exposed to a sample of high electrical loads. The possibility for an adequate choice of insulating materials, which are used in the insulation of VFD cable and shown ways to improve testing methods

Coupling effect in field Hall elements based on thin-film SOI MOS transistors

The influence of the coupling effect on the parameters of field Hall elements based on thin-film MOS transistors has been studied. Analysis of the development of today’s microelectronics shows the necessity of developing the element base for high performance sensors based on silicon technologies. One way to significantly improve the performance of sensing elements including magnetic field sensors is the use of thin-film transistors on the basis of silicon on insulator (SOI) structures. It has been shown that field Hall sensors (FHS) may become the basis of high-performance magnetic field sensors employing the coupling effect occurring in the double gate vertical topology of these sensing elements. Electrophysical studies of FHS have been conducted for different gate bias and power supply modes. The results show that the coupling effect between the gates occurs in FHS if the thickness of the working layer between the gates is 200 nm. This effect leads to an increase in the effective carrier mobility and hence an increase in the magnetic sensitivity of the material. Thus field Hall elements based on thin-film transistors fabricated using silicon technologies provide for a substantial increase in the magnetic sensitivity of the elements and allow their application in highly reliable magnetic field sensors