Collision Mode Research Articles

Experimental Investigation of Kerosene Droplet Distribution in a Linearized Rotating Detonation Engine

ABSTRACT The atomization and mixing process in a linearized rotating detonation engine supplied with non-premixed kerosene was optically analyzed by experiment. Schlieren, simultaneous LIF/Mie technique and particle/droplet image analysis (PDIA) system were applied to study flow field structure and spray properties under various conditions, including air flow rate, fuel flow rate and flow velocity at injector position. Aerodynamic shearing force and fuel injection pressure contribute to the refinement and uniformity of the spray. The distribution of fuel in the combustor has obvious stratification, which makes the local equivalence ratio higher than the set global equivalence ratio. Compared with full-scale RDE experiments, the detonation wave exists in a dual-wave collision mode. The increased kerosene flow rate refines the droplets, which raises the detonation wave velocity. Furthermore, the detonation wave will propagate more stably due to the slower airflow velocity at higher combustor pressure.

Investigating top-Higgs FCNC couplings at the FCC-hh

We have studied the sensitivity to flavor changing neutral current interaction of top and Higgs boson at the future circular collider in the hadron-hadron collision mode (FCC-hh). Our main concerns are the processes of pp→th (FCNC production) and pp→tt¯ (one top FCNC decay) which contributes to the single lepton, at least three jets and the missing energy transverse in the final state. On the one hand FCC-hh offers very high luminosity and large cross section for these signal processes, on the other hand signal can be distinguished from background which needs application of ingenious methods. Here, we have inspired and followed the searches at the LHC using our analysis path and enhanced attainable limits obtained on the possible top-Higgs FCNC couplings phenomenologically. We obtain new limits which are beyond the current experimental limits obtained from different channels and processes at the LHC. The potential discovery or exclusion limits on branching ratios for tqH FCNC interactions can be set BR(ηuc)disc=9.08×10−6 or BR(ηuc)exc=2.78×10−6 at an integrated luminosity of 30ab−1, respectively. Our results are compatible with the other channels already studied at FCC-hh.

Characterization of wave modes in a kerosene-fueled rotating detonation combustor with varied injection area ratios

The rotating detonation engine (RDE) is an innovative and practical pressure-gain device for rocket and ramjet propulsion, and has been widely investigated. The present work aims to explore at length the characteristics of two-phase rotating detonation waves in a typical RDE, particularly characterizing the effects of the injection area and equivalence ratios on the propagation modes. Series of experimental tests were carried out in the specifically designed rotating detonation combustor propelled by liquid kerosene and oxygen-rich air, where the high-speed imaging technique was adopted for visually capturing the traveling trajectories of the detonation waves. The experimental results demonstrated that the rotating detonation wave always propagated in a hybrid mode of single-wave and dual-wave collision. In the single-wave mode, traces of local combustion in the combustor were clearly observed. While for the dual-wave collision mode, the luminosity denoting the reaction intensity was much weaker, and positions of the collision point shifted frequently. The spontaneous mode transitions in the combustor were presented through the synchronous detection of the high-speed camera and pressure sensors, which are the typical characteristics of the hybrid wave mode. The results also implied that a reduction in the injection area increased the pressure of the RDC and the velocity of the detonation waves, and was likely to suppress the deflagration mode. Such a decrease in the injection area ratio finally increased the occurrence time of the dual-wave collision mode during the operation of RDE. The findings could serve as a reference for the design of the propellant injection structure of liquid-fueled RDE.

Overriding Lithospheric Strength Affects Continental Collisional Mode Selection and Subduction Transference: Implications for the Greater India–Asia Convergent System

The India–Asia collision, starting from 55 ± 5 Ma, leads to the formation of the Himalayas and Tibetan Plateau with great gravity potential energy and large forces acting on the surrounding blocks. However, the subduction transference/jump does not occur in the southern Indian continental margin or the northern Indian oceanic plate as supposed to happen repeatedly during the preceding Tethys evolution. Instead, the continental collision and orogeny continues until present day. The total amount of convergence during the India–Asia collision has been estimated to be ∼2,900–4,000 km and needs to be accommodated by shortening/extrusion of the Tibetan plate and/or subduction of the Greater Indian plate, which is a challenging issue. In order to study the collision mode selection, deformation partition, and continental mass conservation, we integrate the reconstruction-based convergence rate of the India–Asia collision into a large-scale thermomechanical numerical model and systematically investigate the effects of overriding Tibetan lithospheric strength and the amount of convergence. The model results indicate that the absence of subduction transference during the India–Asia collision may be attributed to strain localization and shortening of the rheologically weak Tibetan plate. In case of the India–Asia collision for ∼50 Myr with a total convergence of ∼2,900 km, the model with the intermediately weak Tibetan plate could reconcile the general deformation partition and continental mass balance of the Himalayan–Tibetan system. However, the longer period of India–Asia collision for ∼55 Myr leads to significant shortening of the overriding plate that is not consistent with the Tibetan observations, in which case an oceanic basin may be required for the Greater Indian continent.

Experimental Study on Combustion Efficiency and Gas Analysis of RDC with Different Blockage Ratio

ABSTRACT Rotating detonation experiments with 220 mm outer diameter of combustor are carried out. The experiment used aviation kerosene (RP-3) as fuel and hot air as oxidant. Under the condition that the air flow at the inlet of the combustor is kept constant, when the blockage ratio is 50%, 65%, 75% and 90% respectively, the detonation is successfully initiated and works stably in the experiment. Temperature rise method was used to calculate the combustion efficiency of the rotating detonation combustor outlet. Through sampling, the gas at the rotating detonation combustor outlet was analyzed, and the complete combustion rate based on carbon atoms (CCR) was obtained. There is an optimal blockage ratio and equivalent ratio so that the combustion efficiency and CCR of the rotating detonation combustor reach the maximum value during the experiment. The mode of detonation wave is mainly double-wave collision mode. If the blockage ratio is too large, the propagation mode of detonation wave will change from two wave collision mode to axial pulse mode. At this time, the combustion efficiency and CCR will be greatly reduced. When the blockage ratio is constant, increasing the air flow rate is helpful to improve the combustion efficiency and CCR, and broad the working range of the rotating detonation combustor. The change of air flow rate at combustor inlet has little influence on the wave velocity of detonation wave, and the propagation mode of detonation wave is still two-wave collision mode.

Effects of Plate Velocity Slowdown on Altering Continental Collision Patterns and Crustal-Lithospheric Deformation During the Collision Process

Continental collision zones are widely distributed across the earth’s surface with diverse types of tectonic processes. Even the same collision zone shows significant lateral tectonic variations along its strike. In this study, we systematically investigated how plate velocity slowdown after the closure of the ocean influences the continental collision evolution, as well as the effects of kinematic characteristics and continental rheology on varying the continental collision modes in a plate velocity slowdown model. From the comparison between the constant plate velocity system (CVS) and the plate velocity-dropping system (VDS), we can conclude the following: Plate velocity dropping promotes the extension inside the slab by decreasing the movement of the surface plate, whereas slab pull increases as subduction continues. The timing of the subducting slab break-off and the polarity alteration was initiated earlier in the plate velocity drop models than in the constant plate velocity models, and fast convergence may have triggered multiple episodes of slab break-off and caused strong deformation adjacent to the collision zone. Parametric tests of the initial subducting angle, plate convergence velocity, and continental crustal rheological strength in VDS indicated the following: (1) Three end members of the continental lithospheric mantle deformation modes were identified from the VDS; (2) models with a low subducting angle, fast continental convergence velocity, and medium-strength overriding crust were more likely to evolve into a polarity reversed mode, whereas steep-subducting-angle, slow-plate-velocity, weak-overriding-crust models tended toward a two-sided mode; (3) a strong overriding continent is more liable to develop a stable mode; and (4) overriding crustal rheological strength plays a significant role in controlling changes in continental collision modes.

High energy beam energy measurement with microwave–electron Compton backscattering

The uncertainty of the energy measurement of the electron beam on circular electron positron collider (CEPC) must be smaller than 10 MeV to make sure the accurate measurement of the mass of the Higgs boson. In order to simplify the energy measurement system, a new method is proposed by fitting the Compton edge of the energy distribution of the gamma ray from a microwave–electron Compton scattering. With our method, the uncertainty of the energy measurement is 6 MeV for the electron energy of 120GeV in the Higgs mode. In this system, the energy resolution of the gamma detection needs to reach 10−4. Therefore, only the high-purity germanium (HPGe) detector can meet the critical requirement. In a head-on collision mode, the initial photons should be microwave photons with the wavelength of 3.04 centimeters. A cylindrical resonant cavity with selected TM010 mode is used to transmit microwaves. After the microwave–electron Compton backscattering, the scattered photons and the synchrotron-radiation background transmit a shielding structure and then are detected by a HPGe detector at the end of the beam line of the synchrotron-radiation applications. The hole radius in the side wall of the cavity is about 1.5mm to allow the electron beam passing through. The results of the computer simulation technology (CST) software shows that the influence of the hole radius on the cavity field is negligible. The change of the resonance frequency can be easily corrected by fine-tuning the cavity size.

Two-dimensional collisions of disks and spheres

An oblique collision between two spheres or two disks is usually analysed by ignoring the friction force between the objects. In the present paper, effects of the friction force are examined explicitly to analyse oblique collisions between two circular objects. Two distinct collision modes are described, one where the friction force is due to sliding friction and one where static friction dominates. Experimental results are presented for oblique collisions of two ice hockey pucks. This type of collision could be investigated as a student project, for example by colliding two coins on a smooth horizontal surface or two pucks on an air table.

Trace impurity analysis in uranium materials by rapid separation and ICP-MS/MS measurement with matrix matched external calibration

Analysis of trace impurities in uranium materials is crucial for quality control in the nuclear industry and also informative for nuclear forensics. Herein we developed a rapid and high efficient method for accurate determination of 15 impurity elements (Al, Ti, Cr, Mn, Fe, Ni, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Pb, Th) in uranium materials by combining chemical separation with matrix matched external calibration measurement. Uranium sample was digested, separated with the UTEVA resin and directly diluted for ICP-MS/MS measurement under optimized He collision mode. Recoveries of all the impurities exceed 90%, most of which were more than 95%. The inter-element inferences as well as the solution matrix effects on the impurity signals were investigated. The ICP-MS/MS detected signals of Zn and Sb that have high first ionization potentials were relatively more susceptible to the solution matrix compared with other impurity element signals, and thus highlighted the necessity of solution matrix matched between sample and external calibration standards. The detection limits of the proposed method ranged from ng/g to μg/g level for different impurities. The method was validated and further applied to bulk uranium ore samples. Large variation of some impurities such as Mn, Zr, Nb. Pb and Th among different ore samples were observed, which might be attributed to their different origins.

Development of digital BPM front-end conditioning circuit for BEPCII linac

Aiming to control the rising failure rate of electronics system for BEPC II linac’s beam position measurement, considering the physical design parameters of BEPC II and the requirements of band-pass sampling of BPM electronics ADC chip, a digital BPM RF front-end electronics with high isolation degree and good amplitude and phase consistency is designed. The digital BPM electronics system adopts MicroTCA 4.0 system architecture, takes FPGA as the main controller, and is designed based on EDA software. This paper mainly introduces RF power amplifier, digital adjustable attenuator and bandpass filter in RF front-end electronics module, as well as the laboratory and online test results. In the collision mode of BEPC II, positron beam was used to complete the electronic system online test, and the measurement accuracy of x-direction was about 38.46 μm, while that of y-direction was about 26.16 μm. The measurement accuracy and system stability of the proposed method are better than that of commercial analog BPM electronics module, and can meet the beam position measurement requirements of BEPC II linac.

Frequency splicing code-based Brillouin optical time domain collider for fast dynamic measurement

We propose a frequency splicing code-based Brillouin optical time domain collider (FSC-BOTDC) for fast dynamic sensing. By delicately designing the frequency splicing code (FSC), multiple collision modes with controllable characteristics are realized for probing multiple target areas with a high sampling rate. Moreover, the sensing system is simpler and more robust than the previous BOTDC. In the experiment, the FSC-BOTDC with 10-time enhanced sampling rate is implemented for single and multiple target areas measurements. Results demonstrate that tailorable measurements can be achieved by the tunable FSC. Furthermore, the FSC-BOTDC is executed to measure periodic mechanical vibrations over 7.9-km sensing range with the sampling rate of 625 Hz.

Improving the RF stabilities of BEPCII by a disturbance observer based controller

A digital low level radio frequency (DLLRF) system has been developed to replace the old analog LLRF and operated stably at BEPCII east RF station in the past two years. The RF stabilities required for BEPCII are ± 1% in magnitude and ± 1 degree in phase. These are satisfied both by the new DLLRF and the old analog LLRF. Yet, the DLLRF did not improve the RF stabilities so much as expected, especially when the beam current was high in collision mode. The purpose is to improve the RF stabilities further and meet the requirements by the upgraded BEPCII project (BEPC3). A disturbance observer based (DOB) controller to suppress the noise was developed and tested with beam at BEPCII RF system. The DOB controller works and the RF stabilities with beam may be improved from ± 1% to less than ± 0.5% in magnitude and from ± 1 degree to less than ± 0.5 degrees in phase.

Photoproduction of the J/ψ-pair at the LHC with Forward Detector Acceptances

LHC provides a chance to study the physical processes of γγ collision and γ p collision mode by adding a forward detector. In this paper, we investigate J/ψ-pair photoproduction in NRQCD framework at the LHC with γγ collision mode. We calculate the contributions from ${~}^{3}S_{1}^{1}$ , ${~}^{3}S_{1}^{(8)}$ , ${{~}^{1}}S_{0}^{(8)}$ , ${~}^{3}P_{J}^{(8)}$ Fock states, and find that contribution from the colour octet ${{~}^{1}}{S_{0}^{8}}$ ${~}^{3}P_{J}^{(8)}$ and ${~}^{3} P_{J}^{(8)}{~}^{3}P_{J}^{(8)}$ channels dominates this process with forward detector acceptance 0.0015 < ξ < 0.5. We present the differential cross section distributions of transverse momentum $p_{t}^{J/\psi }$ and rapidity yJ/ψ with forward detector acceptances 0.0015 < ξ < 0.5, analyse the signal for J/ψ decaying to a opposite-sign (OS) muon pair. The results show that this process has the potential to be detected at the 13 TeV LHC with forward detector acceptance 0.0015 < ξ < 0.5.

Solitary waves in a two-dimensional graphene-based superlattice

The article is about the features of the propagation of solitary electromagnetic waves in the two-dimensional graphene superlattice both in the collisionless mode and in the collision mode. The quasiclassical approach has been used, in which the law of the dispersion of charge carriers is determined by the approximation of the quantum mechanical calculations. The magnitude of the electric current has been calculated by using the classic kinetic Boltzman equation with the model collision integral in the constant relaxation frequency approximation. The effect of the high-frequency electric field and the nonadditivity of the energy spectrum on the propagation of a solitary electromagnetic pulse in the arbitrary directions inside a sample has been determined. The numerical simulation of the evolution of solitary electromagnetic pulses is performed by using the method of difference schemes.

Optimization and Numerical Analysis of the Ricochet of Conical Nose Projectile in the Collision with Ceramic-Aluminum Armor

The anti-armored bullets have more kinetic energy due to additional mass than ordinary bullets which increases their likelihood function of penetration for a different target. It is necessary to seek solutions to reduce the possibility of penetration of this type of bullets. One of the most important parameters influencing penetration is projectile impact velocity. The mechanism of penetration varies in different velocity ranges. In this paper, the phenomenon of buckling steel cone with a nose cone in a collision with ceramic targets was investigated by the explicit finite element method using LS-Dayna software. The numerical simulation shows acceptable accuracy after comparing the results with previous research. In this study, the critical angle of ricochet at a different velocity ranging from 700 m/s to 1000 m/s and optimization of the optimal thickness ratio of ceramic/metal targets has been considered. According to the simulation outputs and analytical relations, it is clear that the critical ricocheting angle has increased with increasing velocity and the probability of projectile penetration is higher. The results also show that in the case of an oblique collision at a certain angle, the projectile velocity decreases with increasing target thickness with no drastic changes in the directional angle. As the angle of oblique increases, the amount of penetration in the target decreases. For long rod projectiles, the reduction in kinetic energy at the same collision velocities is not much different for both vertical and oblique collision modes. The erosion of the projectile mass in oblique collisions is less than in vertical collisions at the same time.

Precise predictions for charged Higgs boson pair production in photon-photon collisions

The charged Higgs pair production via photon-photon collisions is investigated in the framework of two Higgs doublet model (2HDM), taking into account a full set of one-loop-level scattering amplitudes, i.e., including electroweak (EW) corrections together with soft and hard QED radiation. The numerical evaluation is carried out for three different scenarios, so-called non-alignment, low-mH and short-cascade, defined in the presence of the up-to-date experimental constraints and consistent with theoretical constraints as well. The total cross sections of γγ→H−H+ are scanned over the plane (mϕ0,s), where ϕ0 is h0 for low-mH0 scenario and H0 for other two scenarios. The regions of the parameter space in which the production rates are sufficiently large are highlighted for each scenario. The production rates in different polarization collision modes of initial beams are also discussed. It can be enhanced up to two-times by oppositely polarized photons at high energies and right-handed polarized photons at low energies. Furthermore, decay channels of the charged Higgs boson are examined for each scenario. It is observed that the one-loop EW corrections, i.e., the virtual plus real radiation corrections, reduce the tree-level cross sections and the relative correction is typically in the range of −10% to −30%, depending on model parameters.

Optimization and Numerical Analysis of the Ricochet of Conical Nose Projectile in the Collision with Ceramic-Aluminum Armor

The anti-armored bullets have more kinetic energy due to additional mass than ordinary bullets which increases their likelihood function of penetration for a different target. It is necessary to seek solutions to reduce the possibility of penetration of this type of bullets. One of the most important parameters influencing penetration is projectile impact velocity. The mechanism of penetration varies in different velocity ranges. In this paper, the phenomenon of buckling steel cone with a nose cone in a collision with ceramic targets was investigated by the explicit finite element method using LS-Dayna software. The numerical simulation shows acceptable accuracy after comparing the results with previous research. In this study, the critical angle of ricochet at a different velocity ranging from 700 m/s to 1000 m/s and optimization of the optimal thickness ratio of ceramic/metal targets has been considered. According to the simulation outputs and analytical relations, it is clear that the critical ricocheting angle has increased with increasing velocity and the probability of projectile penetration is higher. The results also show that in the case of an oblique collision at a certain angle, the projectile velocity decreases with increasing target thickness with no drastic changes in the directional angle. As the angle of oblique increases, the amount of penetration in the target decreases. For long rod projectiles, the reduction in kinetic energy at the same collision velocities is not much different for both vertical and oblique collision modes. The erosion of the projectile mass in oblique collisions is less than in vertical collisions at the same time.

Study on binary collision of rod-like particles under simple shear flow

In this study a theoretical study is carried out on the collision of two rod-like particles suspended in Newtonian fluid under a shear flow. The length of the particle is fixed at 2 µm while the diameter is varied so that the aspect ratio (length/diameter) varies from 1 to 20. Liquid viscosity is changed from 0.01 to 1 Pa·s. The Brownian motion is considered to be negligible. Both hydrodynamic and van der Waals interactions are included in tracking the position and the orientation of each particle. The Hamaker constant is fixed at 1.06 × 10−20 J. The result shows that the kinetic constant of coagulation is reduced to approximately 40% of the value for the non-interacting particles when the viscosity is 1 Pa·s. As collision modes, face-edge, side-side, side-edge and edge-edge are considered. The side-edge mode is most frequently observed in the given range of aspect ratio.

Coagulation kinetics of round-sided disk particles under simple shear flow

In this study a theoretical study is carried out on the binary collision of round-sided disks (RSD) suspended in a Newtonian fluid under a simple shear flow. RSD is composed of a disk part and a half-torus part which circumscribes the side of the disk. The diameter of the disk is fixed at 2 µm while the thickness and the half-torus size are varied so that the aspect ratio varies from 0.13 to 0.288. The liquid viscosity is changed from 0.01 to 1 Pa·s. The hydrodynamic force and van der Waals force with the Hamaker constant of 1.06 × 10−20 J are considered in tracking the position and the orientation of each particle. The Brownian motion is considered to be negligible. The collision of two particles initially separated by sufficiently a long distance is considered and the kinetic constant of coagulation is obtained by considering the presence of collision, the orientations of two particles and the flux of liquid flow. The result shows that the kinetic constant of coagulation is reduced to approximately 1/4 of the kinetic constant of non-interacting particles by the hydrodynamic interaction when the viscosity is 1 Pa·s. As collision modes, side-side and side-edge are considered. Side-side mode is found to be the dominant mode of collision for differing aspect ratio and differing viscosity of the liquid. The dominance of the side-side collision mode implies the formation of two-dimensional flocs in the shear flow.

Collision Modes of Two Eccentric Compound Droplets

A compound droplet with its single inner droplet appears in a broad range of applications and has received much attention in recent years. However, the role of the inner droplet location on the dynamical behaviors of the compound droplet is still not completely understood. Accordingly, the present study numerically deals with the eccentricity of the compound droplet affecting its colliding behaviors with the other droplet in a simple shear flow. The solving method is a front-tracking technique that treats the droplet interface as connected elements moving on a rectangular fixed grid. Initially, two compound droplets assumed circular are placed at a distance symmetrically to the domain center and they come into contact, because of the shear flow, when time progresses. During the collision process, the inner droplet that is initially located at a distance to its outer droplet center circulates around this center. It is found that this rotation also contributes to the formation of the collision modes including the reversing, passing-over and merging ones. Starting from a passing-over mode, a transition to a reversing mode or a merging mode can appear when the inner droplets, in terms of their centroids, are closer than their outer droplets. However, the location of the inner droplet within the outer droplet only has an effect when the value of the Capillary number Ca is varied from 0.01 to 0.08. For Ca &lt; 0.01 corresponding to the merging mode and Ca ≥ 0.16 corresponding to the passing-over mode, the inner droplet position has almost no impact on the collision behaviors of two compound droplets.