Performance Prediction Program Research Articles

Determination of Price Reduction Factors for Density-Deficient Asphalt Pavements

Abstract This paper presents the research undertaken for the development of price reduction factors for density-deficient asphalt pavements. Performance characteristics included in this study are fatigue cracking and rutting. The following laboratory tests were performed on two North Carolina Superpave mixtures with varying air void contents: (1) axial compression dynamic modulus tests for modulus determination; (2) indirect tension tests for fatigue performance evaluation; (3) triaxial repeated load permanent deformation tests for rutting evaluation; and (4) accelerated pavement tests on laboratory pavement slabs for fatigue and rutting evaluation using the third-scale Model Mobile Loading Simulator (MMLS3). Air void models for the dynamic modulus, fatigue cracking, and rutting were developed using the laboratory test data. These models and the results from the MMLS3 testing were used to develop the price reduction factors for density-deficient asphalt mixtures. In order to determine the effect of deficient density of hot-mix asphalt (HMA) on the performance of asphalt pavement as a system, a computer program called AP4 (Asphalt Pavement Performance Prediction Program) was developed. The algorithm adopted in AP4 for the damage calculation is based on the incremental damage concept and is very similar to that used in the National Cooperative Highway Research Program (NCHRP) 1-37A Mechanistic-Empirical Pavement Design Guide. This program allows the determination of the service life for fatigue cracking and rutting based on the inputs of air void contents in all the HMA layers. Case studies of five density-deficient pavements were conducted, and the price reduction factors were determined.

선형 근사화에 의한 가변추진시스템 내탄도 성능 변화 예측

일반적으로 고체 추진기관은 안전성, 설계/제작의 용이성 그리고 구조가 간단하다는 장점이 있으나 추진제의 그레인 형상과 노즐목 크기가 결정되면 추력 크기를 임의로 조절하는 것이 불가능하기 때문에 최근 들어 고체 추진기관의 추력을 조절할 수 있는 방법들이 활발하게 연구되고 있다. 본 논문에서는 연소관 압력과 노즐목 크기 변화에 따른 고체 추진기관의 추력 및 주요 내탄도 성능 변화를 선형 근사화로 예측하였으며 내탄도 분석 전용 프로그램(SPP)의 분석 결과와 상호 잘 일치함을 확인하였다. Generally Solid Rocket Motor(SRM) has advantages like this - safety, simplicity and flexibility in design and manufacturing process. However, once propellant grain shape and nozzle throat area are determined, modification of thrust magnitude is nearly impossible. Recently, methods for controlling the thrust magnitude of SRM are vigorously developed. This paper predicts internal ballistic performance variation, especially thrust of SRM by means of Linear Approximation according as chamber pressure or nozzle throat area is changed. The results predicted by the proposed method are good agreement with the those of exclusive Ballistic Performance Prediction Program(SPP).

재생형 연료펌프의 채널 면적 변화가 성능 특성에 미치는 영향에 대한 수치해석적 연구

The effects of channel area on the performance of regenerative type fuel pump were numerically studied by commercial CFD code (ANSYS CFX-10). To examine the effects of channel area, the shapes of the side channel and blade were simplified. The channel area affected the flow characteristics of the internal recirculation flow between the side channel and the blade groove and also made a difference in the overall performance. These loss mechanism with circulation flow were adopted as a loss coefficient in the performance prediction program. The loss coefficient was newly derived from the results of calculations with different channel area, and compared with the experimental results in the reference paper and used to modify the performance prediction program. The circulation flow characteristics with different channel area, which is related with loss mechanism, were also discussed with the results of 3-dimensional flow calculations.

활주형 선박의 선형설계를 위한 통합 CAD/CAE 시스템

In this paper a free-form hull design program and performance prediction program for planing boat is introduced. This program enables the designer to do complex geometric hull shape design on a personal computer and accurately to predict power requirements for a given loading and velocity. For a free form design, Bezier curve model is adopted as a basic representation tool of curves and surfaces, and this program has versatile functions to do fairing jobs with a convenient graphical user interface. After creating a hull form the geometric data is provided in a manner compatible with a variety of analysis tools including 'Motion Analysis(by Zarnick)' for prediction of motion characteristics in regular waves, 'Running Attitude (by Savitsky)' for prediction of the running attitude and required power.

The engine performance prediction by quasi-steady method

In this paper, the theory of Quasi-steady is applied to the calculations of turbochargers matching to the diesel engines and performance prediction. The engine performance prediction programs written in languageC have been used for calculations of various turbocharged diesel engines. It has been confirmed by the comparisons with experimental data that the results of the calculation are reasonable, reliable and satisfied for the engineering applications.

Frequency Domain Analysis of the Performance of a Valved Helmholtz Pulse Combustor*

Abstract A theoretical study of the limit cycle characteristics of a gas fired, mechanically valved, Helmholtz pulse combustor is presented. The analysis is carried out in the frequency domain rather than the time domain in order to develop a performance prediction program that can be run on a personal computer. The pulse combustor is treated as a feedback system. The forward branch of the system consists of the acoustic resonator while the feedback loop consists of the combustion process and heat losses through the pulse combustor walls. The model is based upon an energy balance of the combustion chamber and an analysis of the acoustics of the tail pipe. A previously developed nonlinear model is used to describe the periodic inflow of reactants through the flapper valves and experimental data is used to develop a relationship between the reactants inflow and the magnitude of the oscillatory heat addition by the combustion process. The model predicts that the energy needed to drive the combustor oscillati...

Turbine Preliminary Design Using Artificial Intelligence and Numerical Optimization Techniques

This paper describes a new software approach to the preliminary design of aircraft engine turbines. A hybrid artificial intelligence and numerical-optimization-based design shell called Engineous was used to capture some basic turbine preliminary design knowledge, manipulate turbine design parameters, execute a turbine performance prediction program and its preprocessors, and analyze results. Engineous automatically supplements incomplete human design knowledge with symbolic and numerical search techniques when needed. This approach produced designs with higher predicted performance gains than the existing manual design process in a tenth of the turnaround time and has yielded new insights into turbine design. A comparison of turbine designs obtained by designers and by Engineous is presented here along with an overview of Engineous system architecture.

Calculation of monthly average insolation on a shaded surface at any tilt and azimuth

Estimation of the monthly average solar radiation on surfaces of arbitrary orientation is necessary for many solar performance prediction programs and is useful for other applications. For passive solar applications, especially, overhangs are often used to seasonally modulate the amount of radiation striking the surface. Liu and Jordan[1] have developed a method for estimation of monthly average radiation on unshaded tilted surfaces based on horizontal surface data. This method has been extended to unshaded surfaces of arbitrary tilt and azimuth by Klein[2]. Utzinger and Klein[3] have presented a graphical method for estimating monthly average radiation on shaded vertical surfaces, while Jones [4]has offered an analytical method for the same configuration. This paper presents an analytical solution to the calculation of monthly average insolation on shaded surfaces at any tilt and azimuth. Results are comparable among the three methods when shaded vertical surfaces are analyzed. This analytical method offers an alternative to slower and less accurate numerical integration and to less general regression of numerical integration results for use in solar performance prediction programs.

Specific Impulse Prediction of Solid-Propellant Motors

The methods for the theoretical prediction of delivered specific impulse are relatively well known. They involve computing the losses due to two-phase flow, divergence, boundary layer, kinetics, nozzle submergence, and combustion inefficiency. The largest computed loss in typical aluminized solid propellants is the two-phase flow loss; this computation also has the largest uncertainty because the particle size and distribution are not precisely known. In this paper, a correlation of mean particle diameter vs throat diameter from experimental data was used with the solid-rocket performance prediction program to predict the propellant specific impulse of a number of motors. These predictions are compared to the experimental values. The results indicate that the specific impulse efficiency appears to be an inherent property of the propellant. In addition, the experimental specific impulse and specific impulse efficiency were statistically correlated against motor and propellant variables. These correlations are as accurate as the longer, more expensive, theoretical analysis. In addition to specific impulse prediction, the correlation equations are useful in optimization of motor designs.

Impact of surge waveshape and distribution on the prediction of line performance

Engineering assumptions are the key to the successful prediction of switching surge line performance by statistical methods. Based on hybrid simulator transient analysis and statistical insulation performance prediction programs, several key engineering assumptions are investigated. The insulation strength variation with stress waveshape is well known. However, the impact of this variation on tower clearances has not been well documented and is evaluated in this paper. The nature of the stress distribution also varies, depending on system conditions, breaker design and type of operation (energizing or reclosing). One aspect of this stress distribution is investigated — the allocation of surge magnitudes among the three phases. Again, some work has been devoted to defining this allocation; however, the impact on tower clearances has not been defined. The analysis of these two aspects of switching surge line performance will provide the line designer with basic information for improved engineering assumptions.

An Inverse Design Procedure For High Speed Forms

Due to modern effective missile and sensor systems high speed small to medium sized corvettes and frigates have become the main force in many navies. These craft are cheap alternatives to larger and more expensive conventional warships. However, being small brings its own problems, particularly in seakeeping performance in rough seas. Due to relative smallness in size these vessels must have superior seakeeping performance characteristics in order to carry out complex missions. In the design of these ships proper selection of main dimensions and hull form parameters will influence the operational effectiveness of the vessel. In order to achieve a balanced design an inverse design methodology is developed and applied to high speed small to medium sized vessels. This methodology is based on a direct search method and employs various hull form generation routines, seakeeping performance prediction programs as well as stability and resistance routines. Introduction The primary objective of a ship designer is to obtain the most effective ship that satisfies all requirements of an owner, such as payload, speed, and endurance as well as fulfilling certain safety requirements. Since the hull is the major element of the ship which provides form and structure and contains all other elements of the ship the effectiveness of the design largely depends on the degree of excellency of the hull form design. The design of a high speed vessel is basically a search for the least cost synthesis capable of delivering a required level of performance. Traditionally, it was considered that the best design was determined more by intuition based on the experience of the designer. However, modern weapon and Transactions on the Built Environment vol 5, © 1994 WIT Press, www.witpress.com, ISSN 1743-3509