Non-dimensional Design Parameters Research Articles

A point model for the design of a sulfur trioxide decomposer for the SI cycle and comparison with a CFD model

Operating under the harsh environment with the significant energy consumption, the sulfur trioxide decomposer is one of the most important components, yet challenging tasks for the designers of an efficient SI cycle. We developed a point model to provide important guidelines for designers of a sulfur trioxide decomposer through estimating outlet physical quantities, such as outlet decomposition ratio, outlet temperature, and pressure drop of a sulfur trioxide decomposer. Then, results of the point model were compared to independent predictions obtained using a CFD model over a wide range of conditions with good agreement. The model indicates that decomposition ratio is a function of the representative non-dimensional design parameter and inlet flow composition. As inlet flow composition rarely affects outlet decomposition ratio, we found out that outlet decomposition ratio can be approximated solely as a function of the non-dimensional design parameter. We demonstrated that the model can provide general guidelines for designers of a sulfur trioxide decomposer to achieve a target decomposition ratio with an economical design. It turns out that an increase in operating pressure and catalyst surface area leads to an increase in outlet decomposition ratio while the reverse is true for an increase in mass flow rate.

Exergy Effectiveness Analysis of Three-Fluid Heat Exchanger

In this paper, exergy effectiveness is defined to describe the thermodynamic performance of three-fluid heat exchangers with three thermal communications. It is systemically discussed that the effects of eight non-dimensional design parameters, which include the ratio of the thermal resistances between fluids, the ratio of thermal capacity between fluids, the number of transfer units, the dimensionless inlet temperature of fluid, and the ratio of the inlet temperature of fluids on exergy effectiveness of three-fluid heat exchangers. Furthermore, the exergy effectiveness of the parallel flow is compared with that of the counter flow. The obtained results are helpful for engineers to evaluate and improve the performances of three-fluid heat exchangers.

Non-dimensional analysis and design of a magnetorheological damper

This paper presents a non-dimensional design scheme for a magnetorheological (MR) mixed-mode damper. Based on the Bingham plastic constitutive equation of the MR fluid, four non-dimensional design parameters are defined: Bingham number, non-dimensional damping force, dynamic range and geometric ratio. After investigating the design characteristics of each parameter, sequential design steps for the MR damper are formulated. A single dof vibration model consisting of a spring and an MR damper is then utilized to demonstrate the effectiveness of the proposed design methodology. By imposing equality constraints on required damping force and dynamic range of the vibration model, the principal design parameters, such as electrode length, can be determined from the non-dimensional analysis. Subsequently, the MR damper is manufactured and its measured damping force characteristics are evaluated and compared with the predicted results.

Analysis of Governing Parameters for Silver-Silver Chloride Electrodes in Microfluidic Electrokinetic Devices

Electrokinetics has become a popular method of both particulate and fluidic control in microdevices. In an effort to address the problems associated with conventional electrokinetic control, we use silver-silver chloride electrodes for low-voltage, spatially localized electrokinetic control in microfluidic devices. This work presents an analysis of the electric fields generated by silver-silver chloride electrodes and establishes a nondimensional design parameter that governs the device performance. In addition, an optimal parameter space for maximum electrode longevity is presented.

Three-fluid heat exchangers with three thermal communications. Part B: effectiveness evaluation

Six different effectiveness parameters or figures of merit are defined based on the five identified engineering goals of three-fluid heat exchangers having three thermal communications. The effect of six non-dimensional design parameters on the defined figures of merit is discussed. It is shown that various effectivenesses of this class of heat exchangers strongly depend on the relative thermal capacities of three fluid streams. Any single definition is shown incapable of incorporating all of the five different objectives. A distinction is made between the thermal and temperature effectivenesses of heat exchangers.

Three-fluid heat exchangers with three thermal communications. Part A: general mathematical model

A general, simple and easy to implement analytical model that enables design and analysis of three-fluid heat exchangers with three thermal communications for all flow arrangements is developed. The model is shown to reduce to either a three-fluid, two thermal communications model or the traditional two-fluid heat exchanger model under proper conditions. Six non-dimensional design parameters are identified and their effect on the temperature distributions of the different fluid streams is presented. The model shows that the presence of three coupled thermal interactions makes temperature distributions of the different streams difficult to assess due to slight changes in the design parameters.

LAMINATE MIXING IN MICROSCALE FRACTAL-LIKE MERGING CHANNEL NETWORKS

A two-dimensional model was developed to predict concentration profiles and degree of mixing resulting from diffusion across laminate fluid layers within a fractal-like merging flow network. Numerical results were compared with concentration profiles experimentally acquired using laser-induced fluorescence. Although the numerical model well predicts DoM for Reynolds number less than or equal to 5, for higher Reynolds numbers the three-dimensionality of the experimental flow yields a higher degree of mixing than predicted by the model. The degree of mixing was studied for various geometries, and a nondimensional design parameter was developed to find an optimum number of branching levels for a given channel depth, final width, and total length.

Aerodynamic-Rotordynamic Interaction in Axial Compression Systems—Part II: Impact of Interaction on Overall System Stability

This paper presents an integrated treatment of the dynamic coupling between the flow field (aerodynamics) and rotor structural vibration (rotordynamics) in axial compression systems. This work is motivated by documented observations of tip clearance effects on axial compressor flow field stability, the destabilizing effect of fluid-induced aerodynamic forces on rotordynamics, and their potential interaction. This investigation is aimed at identifying the main nondimensional design parameters governing this interaction, and assessing its impact on overall stability of the coupled system. The model developed in this work employs a reduced-order Moore-Greitzer model for the flow field, and a Jeffcott-type model for the rotordynamics. The coupling between the fluid and structural dynamics is captured by incorporating a compressor pressure rise sensitivity to tip clearance, together with a momentum based model for the aerodynamic forces on the rotor (presented in Part I of this paper). The resulting dynamic model suggests that the interaction is largely governed by two nondimensional parameters: the sensitivity of the compressor to tip clearance and the ratio of fluid mass to rotor mass. The aerodynamic-rotordynamic coupling is shown to generally have an adverse effect on system stability. For a supercritical rotor and a typical value of the coupling parameter, the stability margin to the left of the design point is shown to decrease by about 5% in flow coefficient (from 20% for the uncoupled case). Doubling the value of the coupling parameter not only produces a reduction of about 8% in the stability margin at low flow coefficients, but also gives rise to a rotordynamic instability at flow coefficients 7% higher than the design point.

2301 フラッター発電システムの多目的最適設計

“Flapping Wing Power Generator” extracts wind energy from the flutter phenomenon. The system is governed by six non-dimensional design parameters. Present study carried out a multi-objective design for efficiency and power, and revealed the behavior of the system in detail. To obtain a wide variety of Pareto solutions efficiently, Adaptive Neighboring Search (ANS), one of Evolutionary Algorithms, has been extended to handle multiple objectives in the present study. Tradeoff between efficiency and power was obtained, and the behavior of the system was discussed.

Characterization of fracture behavior in repaired skin/stiffener structure with an inclined central crack

Finite element analysis for the stress intensity factor (SIF) at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels is developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior at the inclined crack. In order to investigate the crack growth direction, maximum tangential stress (MTS) criterion are used. Also, this paper is to study the performance of the effective bonded composite patch repair of a plate containing an inclined central through-crack. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stress intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter, including; composite patch thickness and stiffener distance. We report, the results of finite element analysis on the stiffener locations and crack slant angles and discuss them in this paper. The research on cracked structure subjected to mixed mode loading is accomplished and concludes that more work using a different approaches is necessary. The authors hope the present study will aid those who are responsible for the repair of damaged aircraft structures and also provide general repair guidelines.

Fracture mechanics analysis on the bonded repair of a skin/stiffener with an inclined central crack

The enhancement of the service life of damaged or cracked structures is currently a major issue for researchers and engineers. An analysis for the stress intensity factor (SIF) at a skin/stiffener structure with an inclined central crack repaired by composite stiffened panels is developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior at an inclined crack. In order to investigate the crack growth direction, maximum tangential stress (MTS) criterion are used. Also, this paper studies the performance of an effective bonded composite patch repair of a plate containing an inclined central through-crack. The main objective of this research is the validation of an inclined crack patching design. In this paper, the reduction of SIFs at the crack-tip and prediction of crack growth direction are determined in order to evaluate the effects of various non-dimensional design parameters including: composite patch thickness and stiffener distance. The results of finite element analysis on the stiffener locations and crack slant angles are discussed herein. Research on cracked structure subjected to mixed-mode loading is reported and concludes that more work using a different approach is necessary. The authors hope the present study will aid those who are responsible for the repair of damaged aircraft structures and also provide general repair guidelines.

Optimal design of a thick-walled sandwich pipe

This paper presents a procedure for obtaining an optimal design for sandwich composite pipes. Two designs are considered, namely the optimal design of flexural stiffness and bending strength with regard to certain weight or cost and that of minimum weight and minimum cost with regard to certain flexural stiffness or bending strength. There are many design variables to consider when structuring a sandwich composite pipe. To simplify the design parameters, therefore, a set of non-dimensional variables is presented as design parameters for the optimization of sandwich pipe structures. In this paper, the influence of the design parameters on the flexural rigidity and bending strength of sandwich pipes is discussed with reference to such non-dimensional design parameters. Reduced weight and cost can be achieved by carefully selecting the parameters and geometry of a sandwich pipe.

Fracture Mechanics Analysis of Cracked Plate Repaired by Patch (I)

The enhancement of service life of damaged or cracked structures is currently major issue to the researchers and engineers. In order to improve the life of cracked aging aircraft structures, the repair technique which uses adhesively bonded boron/epoxy composite patches is being widely considered as a cost-effective and reliable method. This paper is to study the performance of the bonded composite patch repair of a plate containing an inclined central through-crack. A 3-dimensional finite element method having three layers to the cracked plate, composite patch and adhesive layer, is used to compute the stress intensity factor. In this paper, the reduction of stress intensity factors near the crack-tip are determined to evaluate the effects of various non-dimensional design parameter including composite patch thickness, and material properties of the composite patch and thickness of the adhesive layer, materials of patch etc., and the crack length, Finally, The problem of how to optimize the patch geometric configurations has been discussed

Analysis of cracks in aging aircraft structures, with and without composite-patch repairs

In this paper, the problems of composite-patch repair of (i) center and edge-cracked panels loaded in the far-field; and (ii) cracks emanating from pin-loaded fastener holes, are examined in thorough detail. The effects of various non-dimensional design parameters on the reduction in the stress-intensity factors near the crack-tip are determined, and are presented in the form of design charts. Both analytical and numerical methods are employed in this study. In the analytical method, the cracked metallic plate was considered to be infinitely large, and the composite patch was modeled as a long orthotropic strip of finite height (in the direction perpendicular to the crack axis). Next, by using the Finite Element Alternating Method (FEAM), a more general analysis capability that can treat arbitrary shapes of the cracked metallic sheet, as well as of the composite patches, is developed. This general FEAM is applied to: (i) composite patch repairs of cracks emanating from loaded fastener holes (the MSD problem); (ii) composite patch repairs of semi-elliptical surface flaws in thick plates; and (iii) composite patch repairs of quarter-elliptical surface flaws emanating from fastener holes. Problem (i) is two-dimensional in nature while problems (ii) and (iii) are fully three-dimensional. In all these cases, the effects of various design parameters on the crack-tip (front) stress-intensity factors are fully discussed.

Optimum Nonlinear Suspension Systems

Global optimal isolation is presented in this paper. Results indicate that to optimally isolate a system, it should be totally disconnected from the disturbance. A model is then selected to optimize nonlinear suspension systems which, in the limits, approach optimal isolation characteristics. Nondimensional design parameters that themselves are made to be dependent on the input are employed. A step disturbance is selected to equivalently represent real excitations. The objective function incorporates the tire-terrain normal force as an indicator of the vehicle controllability which is unconstrained or constrained by a comfort criterion (acceleration). The advantages of optimized realistically nonlinear systems over their linear counterparts are indicated.

System Operational Readiness and Equipment Dependability

The concept of operational readiness of repairable systems is defined in terms of finite queueing theory as the probability that a multidevice, multimodal system will meet specified operational requirements at any given time. The primary determinants are shown to be design parameters and use parameters. Design parameters, which include reliability and maintainability (as measured by MTBF and MTR), can be lumped into a single non-dimensional design parameter, the ``dependability ratio.'' Relationship of this design parameter to single-device availability is first shown. Next, the more general cases are developed: Readiness of exactly N devices, assuming Q ≡ N repairmen (multiple or compound availability). Readiness of at least N - k devices, assuming Q ≦ N repairmen (operational readiness). Single-device availability is shown to be a special case of operational readiness in which full-time availability of a repairman is implicitly assumed. By the use of an example, certain possibilities for tradeoffs among men, machines, and operational requirements are examined, along with implications for design costs vs. procurement costs vs. personnel costs, using the nondimensional dependability ratio as a system variable. For repairable systems, the tradeoff possibilities between reliability and maintainability are indicated. Limitations of the work to date are noted, and directions for further work are indicated. An appendix contains a derivation of singledevice availability for Weibull-distributed time to failure and repair.