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Analysis of tandem wing aircraft configurations has been of interest to the aerospace community since the early 1970's. The theoretical performance gains from the use of two similarly-sized wings make this unusual configuration an enticing option for future aircraft designs. In this investigation, a two-dimensional Navier-Stokes analysis previously developed for internal flow geometries has been extended to external flow geometries. The modified flow analysis was validated against two sets of experimental data. A series numerical simulations were then performed for a tandem-airfoil configuration in which the stagger (chord-wise distance between the mid-chord of each airfoil) was varied. At each stagger position, the aerodynamic flow field was investigated at several negative and positive incidence angles. The predicted results indicate that (for moderate-to-large stagger distances) the aft airfoil performs similar to the fore airfoil at lower angles of attack.

Wise specification of dimensional tolerances for manufactured parts is becoming recognized by the industry as a key to being competitive. This paper describes a tolerance allocation methodology that is based on: statistical stack-up approach using Taylor's Series, manufacturing capability, and manufacturing costs. Application of this methodology can yield substantial cost savings, as is shown by a case study of engine compression ratio.

A process for creating a Customer Correlated, Accelerated, Life Test is presented. This process, which results in a model for predicting reliability, has been applied to a cold weather piston scuff problem. In this paper, the authors will discuss development of frequency distributions for customer environmental and operational use, establishment of customer based failure criteria, development of an accelerated test based on degradation, selection of testing strategies, data analyses, and measurement techniques.

A method is described for predicting the reliability and useful life of an automotive powertrain system using a warranty database or from warranty records. The database requires failure corrections for misdiagnosis from duplicate data, trouble-not-identified records and multiple failure modes. Compensations not included in the database for high-mileage drop-out and warranty repairs less than the deductible amount, are also necessary. As an example, the cumulative hazard function of the Bathtub Hazard Rate distribution is fitted to the converted removal data of a typical automotive powertrain, to determine the product life characteristics. An algorithm written in Basic language is used to obtain the analytical results.

A measure of functional degradation or its surrogate is more informative than attribute data such as failure time when improving designs or developing meaningful tests. This paper delineates the advantages and disadvantages of using degradation data, and the situations under which one should or should not use degradation analysis. A comparison has been done between degradation testing, testing to failure, and bogey testing. The steps necessary to apply degradation analysis techniques to product design have been described: determine scope of the project, plan degradation test, collect data, analyze data, and document results. A case study has been used to demonstrate the whole process of degradation analysis techniques.

This document outlines a methodology for generating and allocating diagnostic requirements for avionics and electronic systems and equipment. The diagnostic requirements to be generated include Fault Detection, Fault Isolation and False Alarm rates. These parameters, along with Time to Detect and Time to Isolate are then allocated to the equipment or replaceable item (RI) level. To achieve the allocations for detection and isolation times, it is also necessary to allocate a top Maintainability (MTTR) Requirement. The diagnostic requirement methodology described herein is built around its relationship to maintainability, MTTR in particular. The approach was formulated in this way because diagnostic parameters are a subset of reliability and maintainability, and a strong mathematical foundation is available within R&M to build a mathematical approach to diagnostic requirements allocation.

This paper shows the place of Markov modeling in the spectrum of modeling tools and explains its benefits and limitations. It introduces the basic components of the model, and answers the questions WHY and WHEN to use Markov modeling. It provides the outline of several different types of Markov models and shows the results of Markov modeling. A process flow chart, a step-by-step procedure, and two examples are provided to facilitate the use of Markov modeling. Finally, this paper introduces the software tool used to perform Markov modeling.

Vibration is a major source of failure in electronics. This environment can create repetitive stresses and fatigue in the interconnections of the printed circuit boards and their components. This paper describes procedures for predicting the lifetime to failure of circuit board components exposed to vibration.

The goal of Hughes Aircraft Company's Robost Design for Six Sigma Manufacturability is a product with minimal defects in production, free of waste and rework, resulting in predictable factory performance through high yields. This process has been piloted on the F-15 APG-63 (V)1 radar program. Expected results are higher quality, improved reliability, consistent performance, low cycle time, low inventory, on time delivery and lower costs.

With the introduction of QS-9000 requirement, the automotive industry has reemphasized one more time the importance of the Failure Mode and Effect Analysis (FMEA). In fact, the FMEA now has become one of the most basic requirements in both the QS-90000 and the Production Part Approval Process (PPAP). The importance of the FMEA is to evaluate the extend of risk as a prerequisite to risk reduction. On this basis, our everlasting desire to minimize “all” risks, practical measures for reduction can be planned and implemented. It is precisely this reason why the QS-9000 and the PPAP have recognized the FMEA as a leading practical measure to minimize risk(s) and failure(s). Failure Mode and Effect Analysis (FMEA) is a methodology that helps identify the activities that are potential risks in the introduction of a new product, process or service. In addition, it helps eliminate problems from current designs, processes and or services.

Temperature changes cause thermo-mechanical stresses and creep in solder joints of electronics. These conditions induce cracking in the solder and eventual failure of the electronic component. This paper describes procedures for predicting the lifetime to failure of electronics exposed to thermal cycling.

N-hexadecane, kerosene and diesel fuels were used for powering a new IDI diesel engine in order to elucidate the role of in-cylinder pyrosynthesis of PAH in diesel emissions. The present work is a complementary to previous investigations (1,2,3) where exhaust deposits have contributed to and interfered with the results. This was eliminated by using a brand new deposit-free engine. Nonetheless, high levels of PAH were detected in the exhaust even with the PAH free fuels. This was attributable to the high rates of lube oil consumption during the running-in period of this engine. The fuel PAH were also shown to play a significant role in the total emissions of these species in diesel combustion.

An old single cylinder Petter AA1 and a new four cylinder Ford 1.61 engines were operated over a wide range of steady state conditions using kerosene and diesel fuels. The two engines exhibited different trends in forming the particulate emissions. For both fuels the particulate emissions were dominated by the carbon for the old engine, and by the SOF for the new engine where the latter was characterized by its low level of emissions. The engine operating conditions also influenced the emissions of the different particulate fractions. Generally, the old engine had higher unburnt lube oil emissions as well as high survival of diesel n-alkanes and PAH in the emissions. However, in the case of kerosene and the new engine when operated both with kerosene and diesel fuel, the pyrosynthesis of these compounds was evident. Sulphates in the particulates, which originated mainly in the fuel, were shown to incorporate low levels of background from the engine deposits and the lubricating oil.

A method to collect and speciate the components of gasoline absorbed in the lubricant oil using gas chromatography has been developed. Samples were collected continuously from the piston skirt, baffle and sump in a Saturn engine. A long (18 hours) test was performed to determine the build up of hydrocarbons in the sump, and a shorter (25 min) test was performed to determine the build up of hydrocarbons in the piston skirt and baffle during engine warm-up. The first experiment showed that the total hydrocarbon concentration in the sump oil reached a steady state of about 1.35% mass fraction after 11 hours of engine operation. The relative concentration of individual fuel hydrocarbon species absorbed in the oil increases exponentially with boiling point. Most of the identified species in the oil consist of the heavy end aromatics. Similar compositions but lower concentrations were found for samples collected from the piston skirt during engine warm-up.

Previous studies to improve upon the Noack volatility test have reported a new approach which does not require toxic Wood's Metal for heating yet agrees well with Noack test results. In addition, the new approach collects 99% of the volatilized oil for optional analysis. This can be important apropos to phosphorus levels which are of concern regarding automotive exhaust catalyst life. To more closely compare the new approach with the Noack test, reference oils used in a recent ASTM volatility round-robin study were analyzed and the new approach was found to produce close agreement with the Noack technique and generally greater repeatability.

Engine oils and their environment can have a negative effect on some elastomeric materials. This depends on the brand of the engine oil and how properties of the oil change between drain intervals. Some elastomeric materials perform poorly in unaged engine oils but well in the aged or ‘used’ oils. Others perform poorly in the ‘used’ fluid but well in the unaged oils, and other elastomeric materials are insensitive to the brand of oil or its age.

Six different gasoline blends with different antiknock agents and aromatics content were investigated for its influence on SI engine nitrogen-oxides and carbon monoxide emissions at part-load operating conditions. The six fuel types used were leaded gasoline with 0.5 g Pb/l, commercial unleaded gasoline, unleaded synthetic gasoline and its blends with different proportions of methyl tertiary butyl ether MTBE (10, 15 and 20 vol%). A four- stroke, four- cylinder, spark- ignition Fiat engine (type 138 B 3.000) was used for conducting this study. The exhaust gases were analyzed for nitrogen-oxides and carbon monoxide emitted at part-load operating conditions for the speed range of 1000 to 3000 rpm. The results of this investgation have shown that blending unleaded synthetic gasoline with ethers such as MTBE reduces the aromatic content of the fuel. The 20 vol% MTBE-fuel blend gave the lowest carbon monoxide emissions of all blends used at part load condition.

A test car program was run to determine if California Phase 2 Reformulated Gasoline (CaRFG) might cause performance and/or other fuel-related problems in vehicles currently on the road in California. In this test, the vast majority of vehicles experienced no performance problems with CaRFG. However, the older or high-mileage vehicles in this program, which were on CaRFG, had an increased rate of fuel system elastomer incidents (e.g., fuel leaks) over the vehicles that were operated on conventional fuel.

While most studies addressing the fuel effects are based on the Federal Test Procedure (FTP), there are limited studies investigating the fuel effects outside FTP test conditions. In this study, we investigated the differences in exhaust emissions from California Phase 1 to Phase 2 reformulated gasoline over a wide range of speed and ambient temperatures. Eleven catalyst equipped passenger vehicles were tested. The vehicles were comprised of three fuel delivery system configurations, namely, three from carburetor (CARBU), three from throttle body injection (TBI), and five from multi-port fuel injection (MPFI) group. Each vehicle was given 60 tests with the combination of two reformulated fuels: Phase 1 (without oxygenates) and Phase 2 (with oxygenates), three temperatures (50, 75, and 100 °F), and ten speed cycles (average speed ranges from 4 mph to 65 mph).

The effects of gasoline volatility (T50 and T90), sulfur content and hydrocarbon types on CO, NOx, total hydrocarbon and speciated hydrocarbons were investigated. The properties of the test gasoline were varied in the range of the Japanese marketplace gasoline, which are characterized by low T50, T90 and low sulfur content. Sulfur content is, especially, regulated under 100 ppm. The Japanese 10.15 mode emissions under hot-transient conditions were measured by using a vehicle equipped with a three-way catalyst. The results indicated that the sulfur content was more effective on exhaust CO, total hydrocarbon and NOx emissions than T50, T90 or hydrocarbon types of gasoline were. The sensitivity to sulfur was different depending on the speciated hydrocarbons. Increasing the sulfur content significantly raised exhaust paraffines, but had no significant effect on olefins. Among the aromatics, the exhaust benzene was most sensitive to sulfur.