Influence of backward-facing step on the mixing efficiency of multi microjets at supersonic flow

© 2020 IAA The injection of the fuel is a highly important process for the enhancement of the scramjets. In this article, the presence of the backward-facing step on the mixing of the multi-fuel jets is expansively studied. The primary attention of this article is to scrutinize the flow feature of the fuel jet under the backward-facing step. The mixing mechanism of the fuel is also studied to compare this injection system with conventional methods. To do this, a 3-dimensional model is chosen to consider the real physic of the problem. Reynolds Average Navier-Stocks equations are solved with a computational fluid dynamic method to visualize the flow pattern of the fuel jet at the free stream Mach number of 4. SST turbulence model is also used for the calculation of the viscosity. Our results indicate that increasing the jet space from 4 to 10 times of jet diameter in the presence of the backward-facing step increases the mixing efficiency up to 20% in the downstream. Our findings depict that augmenting the number of fuel injectors from 4 to 8 augments the mixing rate up to 15% inside the combustor

Numerical modelling for nanoparticle thermal migration with effects of shape of particles and magnetic field inside a porous enclosure

Computational modelling for nanoparticle migration inside a permeable space has been reported. Impacts of shape factor and radiation were included in the mathematical model. CVFEM was employed to analyse magnetic force impact. Impacts of magnetic radiative parameters, buoyancy forces and nanoparticle shape on nanomaterial behaviour were demonstrated. Utilizing the Darcy model helps us to predict the behaviour of porous media. Outputs revealed higher convective mode can be achieved with augmenting buoyancy force while opposite outcome appears when magnetic field is imposed. Thermal plume vanishes with the rise of conductive mode which is gained as Hartmann increases

Influence of upstream strut on hydrogen fuel distribution inside the supersonic combustion chamber

© 2020 Hydrogen Energy Publications LLC The efficient fuel mixing in the combustion tank enhances the overall performance of scramjet. Current attempt examines the existence of the strut on the fuel mixing of the multi hydrogen jets at supersonic flow. The numerical approach was employed to visualize the 3D flow behind the strut with multi fuel-jets. The free-stream Mach is 2.2, and four multi jets released hydrogen inside the combustor with the sonic condition. The impact of jet arrangements and the total pressure ratio on the mixing effect of the strut is fully described. Our results indicate that fuel mixing and penetration improved due to the formation of the large subsonic region behind the strut. According to achieved results, the increasing jet space from 1Dj to 5Dj raises the overall mixing to 15% in our proposed model

Simulation of heat transfer in 2D porous tank in appearance of magnetic nanofluid

In current two dimensional nanomaterial convective flow, Lorentz force has been utilized to manage the flow pattern. Nano sized powders with homogeneous behavior were dispersed into H2O within a permeable media. Not only the buoyancy force but also the radiation affects the temperature distribution. In addition, nanoparticles’ shape was involved in correlation of estimating nanomaterial behavior. Result demonstrated that convective flow augments with both Rayleigh and Darcy number and lessen with respect to Hartman number. Augmenting Darcy number wills leads to reduce the effect of Lorentz forces. Nuave augment with thermal radiation Rd and decrease with Hartmann number Ha. Thinner boundary layer is an output of augmenting permeability

Numerical study of periodic magnetic field effect on 3D natural convection of MWCNT-water/nanofluid with consideration of aggregation

In this paper, a numerical study is performed to investigate the effect of a periodic magnetic field on three-dimensional free convection of MWCNT (Mutli-Walled Carbone Nanotubes)-water/nanofluid. Time-dependent governing equations are solved using the finite volume method under unsteady magnetic field oriented in the x-direction for various Hartmann numbers, oscillation periods, and nanoparticle volume fractions. The aggregation effect is considered in the evaluation of the MWCNT-water/nanofluid thermophysical properties. It is found that oscillation period, the magnitude of the magnetic field, and adding nanoparticles have an important effect on heat transfer, temperature field, and flow structure. © 2019 by the authors

Inclusion of nanoparticles in PCM for heat release unit

© 2020 Elsevier B.V. The main motivation of the present work is to scrutinize the solidification of CuO-water within a heat release unit that has innovative fins. This compact structure along with limitation at the surface of the fins is simulated using Finite Element Method (FEM). Mixture of copper oxide and H2O is introduced as a working fluid. Moreover, the nanoparticle-enhanced phase change materials (NEPCM) shows a significant change in thermal behavior of nanofluid and pure PCM properties by considering the Brownian motion. The outcomes are depicted in the form of temperature, solid fraction and phase change front contours. The results are obtained to determine the variation of phase change by adding the nanoparticles in PCM for various time domains. Similarly, significant effects of nanoparticles volume fraction on the total energy and solid fraction are presented. Furthermore, it is found that the nanoparticles and radiation parameter with size of dp = 40 nm has the greatest heat transfer rate

The optimization via response surface method for micro hydrogen gas actuator

Development of an innovative sensor for detection of hydrogen gas is essential for new applications and devices. In current article, inclusive parametric analysis has been performed to disclose the chief operative term on the performance of the micro sensor of MIKRA for the detection of the hydrogen in the mixture. The main mechanism of this micro actuator highly relies on the value of the exerted Knudsen force which occurs owing to the temperature gradient in the low-pressure region. The response surface methodology (RSM) is applied to obtain an optimized formula for the evaluation of sensor performance. Besides, analysis of variance (ANOVA) is employed to analyze the influence of individual factors on sensor formulation. This work tries to estimate the effect of major parameters such as a gap of the arm, the pressure of domain, mass fraction and temperature difference on the value of Knudsen force. Moreover, reliable correlations for the estimation of the Knudsen force are presented to determine the efficiency of the micro gas actuator in the various operating conditions. Our findings confirm that the precision of the sensor enhances as the temperature difference of the cold and hot arms as well as the hydrogen mass fractions augment in our actuator

Effect of inclined block on fuel mixing of multi hydrogen jets in scramjet engine

© 2020 Elsevier Masson SAS Penetration and distribution of fuel inside the supersonic combustor significantly influence on the overall performance of the scramjet. This research employed the numerical technique to examine the mixing performance of the multi-hydrogen jets at supersonic airflow when the downstream step exists in the downstream of the jet. CFD simulations are conducted to disclose the feature of multi jets when a downstream step is applied. The effects of back step height, free stream Mach number and fuel jet pressure on the mixing efficiency of the four hydrogen jets are disclosed. Our study indicates that decreasing the back step height from 3 mm to 1.5 mm increases the mixing rate up to 28% in downstream of the multi jets. Besides, the formation of the normal shock in upstream of the jet reduces fuel mixing while the normalized mixing factor of fuel jets enhances in downstream of injectors

Computational investigation of multi-cavity fuel injection on hydrogen mixing at supersonic combustion chamber

2020 Hydrogen Energy Publications LLC Enhancement of the mixing inside the combustor is a significant process for increasing the efficiency of the scramjet. This work applied the computational method for the investigation of the depth of the cavity on the flow feature of the multi hydrogen jet in the supersonic crossflow. The main focus of this research is to evaluate the depth of the cavity on the mixing rate of the hydrogen jets inside the combustion chamber. CFD method with the SST turbulence technique is applied for the simulation of the fluid flow inside the domain. The impact of the depth of the cavity, the pressure of the fuel jet and the number of the jet are comprehensively explained in this study. Our findings show that the rising of the cavity enhances the mixing inside the domain due to more fuel distribution along the spanwise direction. Our results clearly demonstrate that replacing the single jet with 8 equivalent multi jets increases the mixing rate of more than 45% in the vicinity of the jet injection. Attained results revealed that increasing the jet space develops the mixing in far downstream. Obtained results also show that mixing intensifies 15% when jet space of 8 microjets is increased from 4 dj to 10 dj