• Title/Summary/Keyword: Vehicle dynamics analysis

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A Numerical Study on the Optimization of Urea Solution Injection to Maximize Conversion Efficiency of NH3 (NH3 전환효율 극대화를 위한 Urea 인젝터의 분사 최적화에 관한 수치적 연구)

  • Moon, Seongjoon;Jo, Nakwon;Oh, Sedoo;Jeong, Soojin;Park, Kyoungwoo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.3
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    • pp.171-178
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    • 2014
  • From now on, in order to meet more stringer diesel emission standard, diesel vehicle should be equipped with emission after-treatment devices as NOx reduction catalyst and particulate filters. Urea-SCR is being developed as the most efficient method of reducing NOx emissions in the after-treatment devices of diesel engines, and recent studies have begun to mount the urea-SCR device for diesel passenger cars and light duty vehicles. That is because their operational characteristics are quite different from heavy duty vehicles, urea solution injection should be changed with other conditions. Therefore, the number and diameter of the nozzle, injection directions, mounting positions in front of the catalytic converter are important design factors. In this study, major design parameters concerning urea solution injection in front of SCR are optimized by using a CFD analysis and Taguchi method. The computational prediction of internal flow and spray characteristics in front of SCR was carried out by using STAR-CCM+7.06 code that used to evaluate $NH_3$ uniformity index($NH_3$ UI). The design parameters are optimized by using the $L_{16}$ orthogonal array and small-the-better characteristics of the Taguchi method. As a result, the optimal values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance(ANOVA). The compared maximize $NH_3$ UI and activation time($NH_3$ UI 0.82) are numerically confirmed that the optimal model provides better conversion efficiency of $NH_3$. In addition, we propose a method to minimize wall-wetting around the urea injector in order to prevent injector blocks caused by solid urea loading. Consequently, the thickness reduction of fluid film in front of mixer is numerically confirmed through the mounting mixer and correcting injection direction by using the trial and error method.

The Dynamics of Noise and Vibration Engineering Vibrant as ever, for years to come

  • Leuridan, Jan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2010.05a
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    • pp.47-47
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    • 2010
  • Over the past 20 years, constant progress in noise and vibration (NVH) engineering has enabled to constantly advance quality and comfort of operation and use of really any products - from automobiles to aircraft, to all kinds of industrial vehicles and machines - to the extend that for many products, supreme NVH performance has becomes part of its brand image in the market. At the same time, the product innovation agenda in the automotive, aircraft and really many other industries, has been extended very much in recent years by meeting ever more strict environmental regulations. Like in the automotive industry, the drive towards meeting emission and CO2 targets leads to very much accelerated adoption of new powertrain concepts (downsizing of ICE, hybrid-electrical...), and to new vehicle architectures and the application of new materials to reduce weight, which bring new challenges for not only maintaining but further improving NVH performance. This drives for innovation in NVH engineering, so as to succeed in meeting a product brand performance for NVH, while as the same time satisfying eco-constraints. Product innovation has also become increasingly dependent on the adoption of electronics and software, which drives for new solutions for NVH engineering that can be applied for NVH performance optimization of mechatronic products. Finally, relentless pressure to shorten time to market while maintaining overall product quality and reliability, mandates that the practice and solutions for NVH engineering can be optimally applied in all phases of product development. The presentation will first review the afore trends for product and process innovation, and discuss the challenges they represent for NVH engineering. Next, the presentation discusses new solutions for NVH engineering of products, so as to meet target brand values, while at the same time meeting ever more strict eco constraints, and this within a context of increasing adoption of electronics and controls to drive product innovation. NVH being very much defined by system level performance, these solutions implement the approach of "Model Based System Engineering" to increase the impact of system level analysis for NVH in all phases of product development: - At the Concept Phase, to be able to do business case analysis of new product concepts; to arrive at an optimized and robust product architecture (e.g. to hybrid powertrain lay-out, to optimize fuel economy); to enable target cascading, to subsystem and component level. - In Development Phase, to increase realism and productivity of simulation, so as to frontload virtual validation of components and subsystems and to further reduce reliance on physical testing. - During the final System Testing Phase, to enable subsystem testing by a combination of physical testing and simulation: using simulation models to simulate the final integration context when testing a subsystem, enabling to frontload subsystem testing before final system integration is possible. - To interconnect Mechanical, Electronical and Controls engineering, in all phases of development, by supporting model driven controls engineering (MIL, SIL, HIL). Finally, the presentation reviews examples of how LMS is implementing such new applications for NVH engineering with lead customers in Europe, Asia and US, with demonstrated benefits both in terms of shortening development cycles, and/or enabling a simulation based approach to reduce reliance on physical testing.

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Effects of Wing Twist on Longitudinal Stability of BWB UCAV (날개의 비틀림이 동체-날개 융합익형 무인전투기의 종안정성에 미치는 영향에 대한 연구)

  • Ban, Seokhyun;Lee, Jihyeong;Kim, Sangwook;Cho, Jinsoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.1
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    • pp.1-9
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    • 2018
  • Lambda wing type Unmanned Combat Aerial Vehicle(UCAV) which adopts Blended Wing Body(BWB) has relatively less drag and more stealth performance than conventional aircraft. However, Pitching moment is rapidly increased at a specific angle of attack affected by leading edge vortex due to leading edge sweep angle. Wind tunnel testing and numerical analysis were carried out with UCAV 1303 configuration on condition of 50 m/s of flow velocity, $-4^{\circ}{\sim}28^{\circ}$ of the range of angle-of-attack. The effect of wing twist for longitudinal stability at the various angles of attack was verified in this study. When negative twist is applied on the wing, Pitch-break was onset at higher angle of attack due to delayed flow separation on outboard of the wing. On the other hand, pitch-break was onset at lower angle of attack and lift-to-drag ratio was increased when positive twist is applied on the wing.

A Numerical Study of Effects of Body Shape on Cavity and Drag of Underwater Vehicle (몸체 형상이 수중운동체의 공동 발달과 항력특성에 미치는 영향에 대한 수치적 연구)

  • Kim, Hyoung-Tae;Kang, Kyung-Tae;Choi, Jung-Kyu;Jung, Young-Rae;Kim, Min-Jae
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.3
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    • pp.252-264
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    • 2018
  • The calculation of steady-state cavitating flows around Supercavitating Underwater Bodies (SUB's), which consist of a circular disk head (cavitator), a conical fore-body, a cylindrical middle-body and either a boat-tail or a flare-tail, are carried out. To calculate the axisymmetric cavitating flow, used is a commercial computational fluid dynamics code based on the finite volume method, Fluent. From the analysis of numerical results, the cavity and drag, affected by the fore-body and tail of the SUB's, are investigated. Firstly, the effect of the fore-body shape is investigated with the same disk cavitator and a cylindrical rear-body of fixed diameter. Then with the same cavitator and a fixed fore-body, the effect of the rear-body shape is investigated. Before the cavity generated by the cavitator covers the slant of fore-bodies sufficiently, the larger the cone angle of the fore-body(i.e., the shorter the slant length), the larger the drag and the slower the development of cavity. After the cavity covers the fore-body completely so that the pressure drag component of the body is vanished, the characteristics of drag-velocity curves are identical. Also, as the tail angle is bigger, the cavity generated by the cavitator is suppressed further and the drag becomes larger. The peak of the drag appears for the flare-tail, i.e., when the tail angle is positive(+). On the contrary, the trough of the drag appears for the boat-tail, i.e., when the tail angle is negative(-). When the tail angle is 5 degrees, the peak of the drag appears at the body speed of 80m/s and the value of the drag is 43% larger than that at the design speed of 100m/s. When the tail angle is -5 degrees, the trough of the total drag appears at 75m/s and that drag is 30% smaller than that of the cavitator, which means the rest of the body has a negative drag.