Propulsion and Power Research最新文献

The conversion of solar radiation to thermal energy has recently much interest as the requirement for renewable heat and power grows. Due to their enhanced ability to promote heat transmission, nanofluids can significantly improve solar-thermal systems' efficiency. This section aims to study the heat transfer behavior of the Sutterby hybrid nanofluid flow of magnetohydrodynamics in the presence of a non-uniform heat source/sink and linear thermal radiation over a non-Darcy curved permeable surface. A novel implementation of an intelligent numerical computing solver based on multi-layer perceptron (MLP) feed-forward back-propagation artificial neural network (ANN) with the Levenberg-Marquard algorithm is provided in the current study. Data were gathered for the ANN model's testing, certification, and training. Established mathematical equations are nonlinear, which are resolved for velocity, the temperature in addition to the skin friction coefficient, and the rate of heat transfer by using the bvp4c with MATLAB solver. The ANN model selects data, constructs and trains a network, then evaluates its efficacy via mean square error. Graphs illustrate the impact of a wide range of physical factors on variables, including pressure, velocity, and temperature. In the entire study, the thermal energy improved by the SiO₂ (silicon dioxide) - Au (gold) hybrid nanofluid than the SiO₂-TiO₂ (titanium dioxide) hybrid nanofluid. The higher internal heat generation/absorption parameter values increase the temperature.

The current article investigates the numerical study of the micropolar nanofluid flow through a 3D rotating surface. This communication may manipulate for the aim such as the delivery of the drug, cooling of electronic chips, nanoscience and the fields of nanotechnology. The impact of heat source/sink is employed. Brownian motion and thermophoresis aspects are discussed. The rotating sheet with the impacts of Darcy-Forchheimer law is also scrutinized. Furthermore, the influence of activation energy is analyzed in the current article. The numerical analysis is simplified with the help of befitted resemblance transformations. The succor of the shooting algorithm with built-in solver bvp4c MATLAB software is used for the numerical solution of nonlinear transformed equations. The consequences of different physical factors on the physical engineering quantities and the subjective fields were examined and presented. According to outcomes, it can be analyzed that the flow profile declined with the rotational parameter. It is observed that angular velocity diminishes via a larger porosity parameter. Furthermore, the temperature gradient is declined via a larger magnitude of the Prandtl number. The heat transfer is enhanced in the occurrence of Brownian motion. The activations energy parameter causes an increment in the volumetric concentration field. Moreover, the local Nusselt number is reduced via a greater estimation of the porosity parameter.

The entropy analysis of viscoelastic fluid obeying the simplified Phan-Thien-Tanner (SPTT) model with variable thermophysical properties are obtained for laminar, steady state and fully developed Couette-Poiseuille flow. The homotopy perturbation method (HPM) allows us to solve nonlinear momentum and energy differential equations. The Reynold's model is used to describe the temperature dependency of thermophysical properties. Results indicate that the increase of the group parameter ($Br/\Omega$) and the Brinkman number (Br) which show the power of viscous dissipation effect; increases the entropy generation while increasing fluid elasticity ($\epsilon {De}^2$) decreases the generated entropy. Increasing the Reynolds variational parameter ($\alpha$) which control the level of temperature dependence of physical properties attenuate entropy generation when moving plate and applied pressure gradient have the opposite direction and decreases entropy generation when moving plate and applied pressure gradient have the same direction or both plates are at rest. Also, increasing elasticity reduces the difference between variable and constant thermophysical properties cases. These results may give guidelines for cost optimization in industrial processes.

Hydromagnetic nanoliquid establish an extraordinary category of nanoliquids that unveil both liquid and magnetic attributes. The interest in the utilization of hydromagnetic nanoliquids as a heat transporting medium stem from a likelihood of regulating its flow along with heat transportation process subjected to an externally imposed magnetic field. This analysis reports the hydromagnetic nanoliquid impact on differential type (second-grade) liquid from a convectively heated extending surface. The well-known Darcy-Forchheimer aspect capturing porosity characteristics is introduced for nonlinear analysis. Robin conditions elaborating heat-mass transportation effect are considered. In addition, Ohmic dissipation and suction/injection aspects are also a part of this research. Mathematical analysis is done by implementing the basic relations of fluid mechanics. The modeled physical problem is simplified through order analysis. The resulting systems (partial differential expressions) are rendered to the ordinary ones by utilizing the apposite variables. Convergent solutions are constructed employing homotopy algorithm. Pictorial and numeric result are addressed comprehensively to elaborate the nature of sundry parameters against physical quantities. The velocity profile is suppressed with increasing Hartmann number (magnetic parameter) whereas it is enhanced with increment in material parameter (second-grade). With the elevation in thermophoresis parameter, temperature and concentration of nanoparticles are accelerated.

In this paper, plasma actuators are arranged asymmetrically downstream the wall to improve film cooling performance. Effects of blowing ratio, hole configuration and applied voltage on flow characteristics and film cooling effectiveness were investigated numerically on a flat plate. Results show that highest film cooling effectiveness distribution is obtained both in the spanwise and streamwise directions under blowing ratio of 0.5. Average wall film cooling effectiveness of cylindrical hole increases by 251.9% under blowing ratio of 0.5 compared to that under blowing ratio of 1.5. The scale of the counter rotating vortex pairs (CRVP) from fan shaped hole and sister hole are significantly reduced compared to that from cylindrical hole. The console hole has an anti-counter rotating vortex pair (Anti-CRVP), which weakens the entrainment of the CRVP to the coolant air near the wall. Compared with the cylindrical hole, average wall film cooling effectivenesses for fan shaped hole, sister hole and console hole increase by 73.1%, 97.5% and 119.9%. The adherent performance of the coolant air is enhanced after applying plasma actuator. The aerodynamic actuation of the plasma results in the rebound of the fluid close to the wall at 24 kV applied voltage. Average wall film cooling effectiveness of the console hole at 12 kV applied voltage is 10.6% higher than that without plasma.

Wavecatcher (inward-turning) intake flows, at design Mach 12, are investigated numerically, to display the effect of wall temperature on flow structures and intake performance. Hypersonic experiments on shock wave/boundary layer interaction are used to validate the Spalart-Allmaras turbulence model for reproducing the features of hypersonic flow. Simulations of hypersonic intake flow are performed at different wall temperatures, including isothermal T_w = 300 K, T_w = 1000 K, T_w = 2000 K, and the adiabatic case. The shock structures, impinging shock positions, surface streamlines, and the development of internal streamwise vortices are discussed. The mass-averaged performance of intake flow shows that, when the wall temperature changes from T_w = 300 K to adiabatic, the mass capture coefficient decreases from 0.991 to 0.933, the total pressure recovery decreases from 0.200 to 0.083, while exit section Mach number decreases from 4.478 to 3.514. The results suggest that the osculating design method of wavecatcher intake design can successfully be extended to Mach 12, while capturing all airflow at isothermal wall conditions.

Non-contacting finger seals represent an advanced non-contacting and compliant seal in gas turbine sealing technology. This paper proposes a new structure of non-contacting finger seals with double interlocking pads. The numerical analysis model based on the thermo-fluid-structure coupling method for the new type finger seal was established. The influence of working conditions on leakage of the seal was studied and compared with the single padded non-contacting finger seal. The results show that the interface between the bottom of the finger pad and rotor surface is the main leakage path that forms the gas film with obvious variations of pressure and flow velocity. Under high temperature and high pressure operating conditions, the hydrodynamic effect of the gas film is enhanced, and lifting force is significantly improved. The deformation of fingers is composed of elastic deformation and thermal deformation. At room temperature, the deformation of fingers is mainly elastic deformation and points to the center of the rotor, which reduces the gas film clearance. The deformation of fingers at high temperature and high pressure creates a circumferentially convergent gap between the bottom of the pad and the rotor, which is beneficial to improve the loading capacity and to reduce leakage of the seal. Compared with the typical single padded non-contacting finger seal, the double interlocking padded finger seal proposed in this paper reduces the leakage factor by about 37%, which provides an advanced seal concept with the potential to improve sealing performance under high temperature and high pressure working conditions.

Gas flow in the seal system can be expected during the operation of a turbocharger and is associated with negative effects on the quality of the lubricant or turbocharger efficiency. Gas flow also affects particulate matter production due to lubricant entrainment in the compressor or turbine. The prediction of gas flow rates depends on many design parameters and the operating conditions of the turbocharger, but sufficiently accurate descriptions of the gas flow mechanisms and their quantification depending on the operating conditions have not yet been presented. The proposed computational approach simultaneously solves the gas dynamics in the seal system, the heat transfer in the turbocharger rotor-bearing system and the dynamics of the seal rings and rotor, including the bearings. The computational model for the turbocharger of a heavy-duty vehicle engine is experimentally validated. Two mechanisms have major influences on gas mass flow: the gas flow through the thin gap between the moving ring and groove and the flow through the ring gap. The results show that the importance of these mechanisms depends on several geometrical dimensions of the seal system and the operating conditions of the turbocharger, with a strong connection to the rotor dynamics and thermal load of the impellers. Influences involving rotor movement or rotor thermal conditions are crucial, and their non-inclusion limits the ability to correctly predict gas mass flow.

The current work is being done to investigate the flow of nanofluids across a porous exponential stretching surface in the presence of a heat source/sink, thermophoretic particle deposition, and bioconvection. The collection of PDEs (partial differential equations) that represent the fluid moment is converted to a system of ODEs (ordinary differential equations) with the use of suitable similarity variables, and these equations are then numerically solved using Runge Kutta Fehlberg and the shooting approach. For different physical limitations, the numerical results are visually represented. The results show that increasing the porosity characteristics reduces velocity. The mass transfer decreases as the thermophoretic limitation increases. Increases in the porosity parameter reduce skin friction, increases in the solid volume fraction improve the rate of thermal distribution, and increases in the thermophoretic parameter increase the rate of mass transfer.