Supersonic Hydrogen Jet Research Articles

A LES study on the instantaneous H2 jet-ignited combustion characteristics of H2/NH3 mixtures

This paper presents a Large Eddy Simulation (LES) study investigating jet flame ignition characteristics to achieve stable ammonia combustion for novel applications in gaseous ammonia/hydrogen-fueled engines with an active prechamber. The study investigated three cases with initial global equivalence ratios of 0.6, 0.8, and 1.0. Two main ignition modes were proposed, and five stages of coupled flame propagation processes were identified. The oscillation of supersonic hydrogen jet flame was investigated. The modes of flame-vortex interaction including vortex ring formation, along with the mechanism of highly reactive zone formation, were proposed. The effects of reactivity and turbulence transition on piloted ammonia flame were investigated to attain stable ammonia combustion and achieve a high heat release rate. The results showed that oscillations in the jet flame were strengthened at low global equivalence ratios with high hydrogen mass ratios. Enhancing propagation of initial and secondary vortex rings broadened highly reactive zones. Vorticity dissipated more rapidly at low equivalence ratios, leading to a stratified structure and enhanced piloted spherical flame. The Unsteady Flamelet Ignition Prediction (UFIP) sub-model of combustion was verified for the piloted ammonia flame, enabling a more comprehensive discussion of flame propagation tendencies.

Effect of the Ambient Medium Parameters on Ignition and Combustion of a Supersonic Hydrogen Jet Expanding into a Still Space

Effect of the Ambient Medium Parameters on Ignition and Combustion of a Supersonic Hydrogen Jet Expanding into a Still Space

Effect of the Ambient Medium Parameters on Ignition and Combustion of a Supersonic Hydrogen Jet Expanding into a Still Space

Effect of the Ambient Medium Parameters on Ignition and Combustion of a Supersonic Hydrogen Jet Expanding into a Still Space

LES of H2-air jet combustion in high enthalpy supersonic crossflow

Here, we report on large eddy simulation (LES) of supersonic flow, mixing, self-ignition, and combustion in a supersonic hydrogen jet in a crossflow configuration. The configuration has been experimentally investigated at Stanford and consists of a rectilinear channel with a ramp inlet in which a hydrogen jet discharges at a 90° angle to the high enthalpy supersonic crossflow. This configuration has been extensively studied by several research groups and constitutes a good validation case for model development and physics elucidation. The LES model used is based on an unstructured finite volume discretization of the filtered mass, momentum, species, and energy equations and an explicit flow solver. In this study, we investigate the effects of the jet-to-crossflow momentum ratio, the chemical reaction mechanism, and the combustion subgrid model by comparing predictions and by comparing with experimental data including OH* chemiluminescence images and jet penetration data. In general, good agreement is found but with some departures for the smallest reaction mechanisms and some of the LES combustion models. The LES results are also used to elucidate the flow, mixing, and combustion features of this configuration.

High-fidelity resolution of the characteristic structures of a supersonic hydrogen jet flame with heated co-flow air

In the present paper, direct numerical simulation (DNS) is performed to analyze the characteristic structures of a supersonic jet lifted hydrogen-air flame with Reynolds number of 22, 000, and Mach number of 1.2. The fuel consisting of 85% H2 and 15% N2 by volume is injected into hot co-flow air from a round orifice. Overall 975 million grids are used to compute the complex multi-scales phenomena. A Damköhler number and a flame index are defined to analyze combustion modes and the mixedness of the flame. Complicated characteristic elements of the supersonic jet lifted flame are observed, i.e. a stable laminar flame base with auto-ignition as the stabilization mechanism, a violent mixing region in which vigorous turbulent combustion occurs with both fuel-lean and fuel-rich mixtures, and a flame region consisting of outer diffusion combustion and inner weaker premixed combustion in the far field. At the leading edge of the fame base, auto-ignition takes place primarily in the fuel-lean mixture where the mixedness mode is opposed. Downstream of the laminar flame base, the combustion becomes turbulent due to the intensified mixing of fuel and air, which results in the subequilibrium values of temperature and OH concentration. Detonation occurs near the sonic layer, and then sustains the combustion in higher dissipative mixture. The flame near the stochiometric condition keeps non-premixed, and the other non-premixed flame elements could be observed in the very fuel-rich region. Through the reacting field the premixed flame appears near the shear layer. The combustion intensity decreases in the far field where the inner non-premixed flame disappears gradually.

Characteristics of supersonic combustion of unmixed gases in channels

6. P. N. Rowe, K. T. Claxton, and J. B. Lewis, Trans. Inst. Chem. Eng., 43, TI4-T31 (1963). S. V. Bukhman and E. Nurekenov, Problems in Thermal Power Generation and Applied Thermophysics [in Russian], No. 2, Nauka, Alma-Ata (1965). CHARACTERISTICS OF SUPERSONIC COMBUSTION OF UNMIXED GASES IN CHANNELS V. L. Zimont, V. M. Levin, E. A. Meshcheryakov, and V. A. Sabel'nikov UDC 536.46:533.6 Supersonic combustion of unmixed gases in channels is determined by the interaction of turbulent diffusion, chemical kinetics, and gasdynamic effects accompanying the liberation of heat. Under certain conditions, the influence of each of the factors listed can become critical for the combustion process. In this paper we present the results of measurements and of calculations in order to clarify the role of these factors in the formation of the physical picture of the flow. Primary attention is devoted to the analysis of the influence of deceleration of the supersonic flow to subsonic velocities, pulsations in the concentra- tion, and finite rates of chemical reactions on the combustion. i. Two regimes, which are analogs of undercompressed (combustion products have super- sonic velocity, M > i) and overcompressed (M i. With combustion in a pseudojump, a broad subsonic region occurs at the center of the channel. This is what distinguishes the pattern of the flow in the second case (with the flow of fuel examined) from the flow in the pseudojump without combustion, where the sub- sonic zone is situated near the wall [2]. This circumstance must be taken into account in developing models of such flows. Apparently, a correct calculation of such flows is possible only based on the solution of the complete elliptical system of transport equations. 2. At the present time, numerical investigations of combustion in channels are per- formed primarily in the boundary layer approximation. The influence of concentration pulsa- tions on the process of diffusion combustion with subsonic flow velocities in channels was analyzed in [5]. Here the analysis is generalized to the combustion of a supersonic hydrogen jet. In contrast to subsonic combustion, in the case examined, the kinetic energy in the expression for the total energy (enthalpy) cannot be neglected. For this reason, the unaver- aged density and temperature depend on the concentration of the inert admixture Z and the velocity u. To determine the average values of the density $ and the temperature T, the joint probability density P(Z, u) was approximated by the following expression (if this ex- pression is integrated over u, then we obtain the approximation of the probability density P(Z) used in [5]): p (z, u) = (1 - v) 6 (u - u~) 8 (z) + v8 (u - ut) 6 (z - zt),

509. A supersonic hydrogen jet in a vacuum: V B Yuferov et al, Zh Tekn Fiz (USSR), 35 (8), Aug 1965, 1522–1523, (in Russian). English translation in Soviet Phys Tech Phys, (USA), 10 (8), Feb 1966

509. A supersonic hydrogen jet in a vacuum: V B Yuferov et al, Zh Tekn Fiz (USSR), 35 (8), Aug 1965, 1522–1523, (in Russian). English translation in Soviet Phys Tech Phys, (USA), 10 (8), Feb 1966