Inlet Contour Research Articles

Potential improvement of aerodynamic performance by morphing the nacelle inlet

In this work numerical investigations of the aerodynamic performance of an adaptive turbofan-engine inlet are performed. The adaptation is made on the inner front part of the symmetric inlet by changing the positions of two contour knots, which acts as a possible inlet structure morphing. The contour knots are moved in the axisymmetric and radial directions of the inlet respectively. The numerical calculations are performed using Reynolds Averaged Navier–Stokes (RANS) simulations and are made for climb and cruise flight conditions. The evaluation of the aerodynamic performance is based on the absolute total pressure recovery at the fan plane. The results show that the adaptation of only a small part of the inlet contour gives benefits in the performance at different flight conditions. The radial position increase of the knot closer to the leading edge gives an overall increase of the pressure recovery level for both flight conditions. The radial position change of the knot close to the throat diameter leads to the global maximum of the absolute total pressure recovery almost independent of the axial position change of the same knot, for both flight conditions. These maximums are attained at different radial positions of the knot close to the throat diameter for the two flight conditions.

Experimental Characterization of Various Cold Aisle Containment Configurations for Data Centers

The data center industry has experienced significant growth over the last decade, mainly due to the increased use of the internet for our day to day activities such as e-commerce, social media, video streaming, and healthcare. This growth in demand results in higher energy costs, as data centers can be energy intensive facilities. A significant portion of the energy used in data centers is for cooling purposes. Hence, it is one of the important areas of optimization to be addressed to create more efficient data centers. Among the many ways to increase data center efficiencies, air flow management is a key solution to many existing data centers. Fundamentally, there are three main schemes: hot-aisle containment, cold-aisle containment, and exhaust chimney containment. This paper's focus is to experimentally characterize the following cold aisle configurations: open aisle, partially contained aisle, and fully contained aisles. Experimental data presented to evaluate the effectiveness of the different configurations are rack inlet contour plots, tile and rack flow rates, pressure measurements, and server central processing unit (CPU) temperatures.

Acoustic power in non-uniform lined ducts

A definition of acoustic power in conservation form in lined infinitely long uniform ducts is extended to include axially symmetric non-uniform ducts with potential mean flow and finite length lining. The definition includes a contribution at the lined boundary. Benchmarking is accomplished by verification of acoustic power conservation in the case of a purely reactive lining. Calculations in the case of reactively lined ducts show that intense acoustic gradients near the lined surface can occur, and contributions to acoustic power from the boundary power term become relatively large. This observed behavior diminishes as the resistive component of lining impedance is increased. Power calculations for propagation and radiation from a typical turbo-fan inlet and equivalent calculations for an infinite duct propagation model of the same inlet contour are compared. Results are remarkably similar for the case considered, though it is noted that this conclusion is geometry dependent.

Die Inlet Contour Impact on the Pressure Rise in a Pultrusion Die

The quality of a pultruded composite depends on many process control parameters and variables. The pressure rise in the pultrusion die inlet is one such variable which can impact the quality of a pultruded product. An appreciable die inlet pressure rise can suppress void formation and enhance fiber "wet out." In this study, a model based on Darcy's law for flow in a porous medium and which employs the finite volume solution method is developed to predict the pressure and velocity fields as a function of various die inlet contours. Investigating the behavior of the pressure rise in the pultrusion die inlet as a function of the shape of the die inlet contour can be a very useful and effective tool for analyzing and designing pultrusion die inlets. Various die inlet contours such as the wedge, circular tapered die inlet, and some hypothetical die inlet contours were investigated to determine the impact on die inlet pressure rise. The original contributions of this paper are results which are useful for designing pultrusion dies and for producing an optimum pressure rise which will enhance the quality of the pultruded product.

Die Inlet Contour Impact on the Pressure Rise in a Pultrusion Die

The quality of a pultruded composite depends on many process control parameters and variables. The pressure rise in the pultrusion die inlet is one such variable which can impact the quality of a pultruded product. An appreciable die inlet pressure rise can suppress void formation and enhance fiber "wet out." In this study, a model based on Darcy's law for flow in a porous medium and which employs the finite volume solution method is developed to predict the pressure and velocity fields as a function of various die inlet contours. Investigating the behavior of the pressure rise in the pultrusion die inlet as a function of the shape of the die inlet contour can be a very useful and effective tool for analyzing and designing pultrusion die inlets. Various die inlet contours such as the wedge, circular tapered die inlet, and some hypothetical die inlet contours were investigated to determine the impact on die inlet pressure rise. The original contributions of this paper are results which are useful for designing pultrusion dies and for producing an optimum pressure rise which will enhance the quality of the pultruded product.

Pultrusion die pressure response to changes in die inlet geometry

AbstractPultrusion is a process of manufacturing composites that requires a high resin pressure rise in the tapered die inlet region. A sufficiently high pressure rise is important for a good quality pultruded product, thereby necessitating a study of the mechanisms affecting the die inlet pressure rise. Various process control parameters affect the resin pressure rise in the die inlet. The geometry of the tapered die inlet region can have a significant effect on the pressure rise in the pultrusion die. In this study a finite element model was developed to predict this pressure rise as a function of the tapered die inlet geometry. The composite matrix being pultruded was modeled on the assumptions of Darcy's laws for flow in porous media. A Galerkin's weighted residual based finite element technique was used to solve the governing equations. The pressure rise in the tapered inlet region of the die, as well as in the straight portion of the die, is predicted by this finite element model. Circular, parabolic, and wedge shaped die inlets have been modeled to compare their shapes on the resin pressure rise in the pultrusion die. Different angles for wedge shapes, different radii for circular shapes, and different foci for parabolic shapes were modeled to predict the influence of varying key geometrical parameters for each die inlet contour on pressure rise. The finite element model developed provides insight as to how to design the die inlet to produce a suitable pressure rise in the pultrusion die inlet.

Measured particulate behavior in a subscale solid propellant rocket motor

Particle size distributions were measured in the combustion chamber, exhaust nozzle, and exhaust plume of a small, two-dimensional rocket motor that utilized aluminized propellants. Various nozzle contours and pressures to 4.36 MPa were utilized. For pressures less than approximately 2.4 MPa, D32 of the multimodal size distributions entering the nozzle decreased with increasing pressure. Above 2.4 MPa, the higher propellant burning rates significantly reduced particle agglomeration and increased C* efficiency. At higher pressures, D32 entering the nozzle was quite small (2-6 /u.) and monomodal, and did not vary appreciably with pressure. During tailoff, D32 was significantly larger than during the steady burn, indicating another possible source for plume signature variations. Exhaust particle D32 was 1.2-1.6 /* (with a <2, 8, 28 /* trimodal distribution), independent of pressure, nozzle inlet contour, exit Mach number, degree of underexpansion, or location aft of the exit plane. The existence of a small number of larger particles indicated that either particle collision and/or surface effects occurred in the nozzle convergence, or that the larger particles at the nozzle entrance were concentrated near the wall, out of the viewing volume in the center of the flow.

Numerical investigation of supersonic mixed-compression inlet using an implicit upwind scheme

Numerical simulation of a two-dimensional mixed-compression supersonic inlet by solving time-dependent, compressible Navier-Stokes equations associated with the Baldwin-Lomax turbulent model is presented. An implicit second-order upwind scheme was employed to obtain numerical solutions. The inlet experimentally studied by Anderson and Wong at design Mach number 3.0 and the pressure ratio as high as 31.5 is successfully simulated. The deterioration of the inlet performance caused by viscous effect is controlled by incorporating a bleed system. For a two-dimensional inlet contour designed by method of characteristics, the current numerical experimentation shows that the flow is unstarted (choked). However, an overspeed to Mach number 3.05 can start the inlet flow. To numerically start the inlet at design Mach number 3.0, a minimum 2% increase in the throat area is found necessary. To obtain a uniform velocity profile at the engine face, a simple numerical model for experimentally installed vortex generators was introduced. The relations between the engine face pressure and the total pressure recovery and the flow distortion level are analyzed. Under boundary-layer control, numerical results indicate that a minimum 12% bleed is necessary to sustain a stable operation for the supersonic inlet.

FORTRAN program to generate engine inlet flow contour maps and distortion parameters: NASA Technical Memorandum, NASA TM X-2967 (February 1974)

Program generates inlet contour maps with choice of mapping parameters. Contour maps are represented by symbols on picture produced by line printer. Program also generates variety of simple circumferential and radial distortion parameters that enable calculation of almost any specific distortion parameter.