Vehicles experience various frequency excitations from road surfaces. Recent research has focused on active dampers that adapt their damping forces according to these conditions. However, traditional magnetorheological (MR) dampers face a “block-up phenomenon” that limits their effectiveness. To address this, additional flow-type MR dampers have been proposed, although revised designs are required to accommodate changes in damping force characteristics. This study investigates the damping performance of MR dampers with an additional flow path to enhance the vehicle ride quality. An optimization model was developed based on fluid dynamics equations and analyzed using electromagnetic simulations in ANSYS Maxwell software. Vibration analysis was conducted using AMESim by applying a sinusoidal road surface model with various frequencies. Results show that the optimized diameter of the additional flow path obtained from the analysis was 1.1 mm, and it was shown that the total damping force variation at low piston velocities decreased by approximately 56% compared to conventional MR dampers. Additionally, vibration analysis of the MR damper with the optimized additional flow path diameter revealed that at 30 km/h, 37.9% acceleration control was achievable, at 60 km/h, 18.7%, and at 90 km/h, 7.73%. This demonstrated the resolution of the block-up phenomenon through the additional flow path and confirmed that the vehicle with the applied damper could control a wider range of vehicle upper displacement, velocity, and acceleration compared to conventional vehicles.
In use 25ton trailers with Hyundai electronically controlled D6CB was converted to dual fuel system. To estimate economical efficiency, test vehicles have been operated on a certain driving route repeatedly. Test gross weight is about 30ton and both MPI and SPI natural gas injection systems are evaluated. Fuel economy, driving distance per refueling and driveability are examined in the field test including free way. Developed vehicle can be operated over 500km with dual fuel and shows 85% of diesel substitution ratio. Driveability is similar with but passing acceleration. It will be improved by calibration process. Test engine was set up for investigating power output, thermal efficiency and emission. ND 13-mode tests were performed for the test cycle. The emission result of dual fuel meets K2006 regulation the diesel equivalent engine performance output condition. Thermal efficiency is slightly low at full load condition and even worse at low load as compared to diesel operation.
A diesel particulate filter (DPF) is an exhaust after-treatment device designed to capture and store exhaust particulate matter, such as soot and ash, to reduce emissions from diesel-powered vehicles. A DPF has a finite capacity and typically uses a substrate made of ceramic material that is formed into a honeycomb structure. Diesel particulate filters play an important role in diesel-fueled vehicles. Failure to maintain these filters can have significant consequences for vehicles. In this study, we investigated the failure type in cordierite DPF substrates. In addition, we experimentally characterized the particle number (PN) emission and on-board diagnostics (OBD) signal of a 2.0 L diesel-fueled vehicle generated by three types of DPF failure (crack, melting, and hollow). Specifically, X-ray photography analysis of the cordierite DPF was performed. The PN and OBD signals were assessed via the KD-147 vehicle driving mode and measured using a DMS-500 (PN measurement device) and global diagnosis tool (GDS) scanner (OBD diagnostic device), respectively. X-ray photography was used to characterize the internal structure of the three DPF-failure samples. A key result was that the maximum value of the OBD data, including airflow mass, boost pressure, and VGT actuator, was distinctly different for each DPF sample. The exhaust temperature gradient for the normal DPF and crack-damaged DPF followed the KD-147 driving pattern. This was because there was no volume damage inside the cordierite DPF substrates. However, in the case of the hollow and melting-damaged DPF, the volume inside the cordierite DPF substrates was reduced or the time for the exhaust gas to stay in the DPF substrates was decreased. The melting-damaged DPF continuously emitted the largest number of nanoparticles (of the order of 109 #/cc). This was regardless of the vehicle driving speed in the KD-147 driving mode. Eventually, an OBD-based algorithm to determine whether a DPF is damaged was derived in this study.
Most small SUVs in the automotive market are equipped with torsion beam suspension for the rear wheels. Torsion beam suspension consists of a cross-member and a trailing arm. The cross-member plays a crucial role in preventing the vehicle from twisting; therefore, a shape that can withstand loads is essential. In this study, various shapes of cross-member reinforcements were added to the existing torsion beam suspension to analyze its structural strength when subjected to arbitrary forces. Analysis results were obtained for stiffness and driving stability factors such as smooth road shake, impact hardness, and memory shake. Based on these results, we identified the optimal cross-member shape with low torsional stiffness and a small side view swing arm angle by examining the changes in driving stability.
본 연구는 터널 라이닝의 상태 평가를 위한 비파괴 검사 방법인 지상파 레이더(GPR)를 활용하여 실용적인 공동 크기 추정 방법을 개발하고자 하였다. GPR 시험은 미국 GSSI(Geophysical Survey Systems, Inc.)의 장비를 사용하여 다양한 라이닝 두께, 공동 크기 등의 조건을 조합한 실대형의 모형시험체를 제작하여 시험을 수행하였다. 연구 결과, 공동의 크기에 따라 GPR 반사파가 중첩되면서 파형이 변화하는 것을 확인하였다. 이러한 결과를 기반으로 공동 크기를 추정하는 경험적인 방법을 제안하였다. 또한 다른 모형시험체에 대한 시험 결과 및 추정결과를 비교 검증하였다. 제안된 방법은 추정식 제안에 적용된 시험체의 라이닝과 같은 두께의 조건에서 공동 크기를 보다 높은 정확도로 추정할 수 있음을 보여주었다.
수치해석을 통하여 고에너지물질의 초음속 화염 전파에 대한 틈새(gap)의 효과를 연구하였다. 특성음향임피던스(characteristic acoustic impedance) 이론을 적용하여, 고폭약 및 고체추진제의 틈새(gap) 실험과 관계된 반사와 투과 현상들에 대한 이해를 추구하였다. 한편, 여러 개의 틈새(gap)가 위치하고 있는 화약의 한 끝에 초음속 화염이 발생되도록 하여, 여러 틈새(gap)에 전파되나가는 연속적인 화염에 대한 이해를 시도하였다. 이러한 고차원 다물질 해석을 통해, 충격하중 하에서의 고에너지 물질의 반응 특성이 물질 간격 동특성에 의하여 어떠한 영향을 받는지 이해할 수 있다. We study the gap effect on detonating high explosives using numerical simulation. The characteristic acoustic impedance theory is applied to understand the reflection and transmission phenomena associated with gap test of high explosives and solid propellants. A block of charge with embedded multiple gaps is detonated at one end to understand the ensuing detonation propagation through pores and non uniformity of the tested material. A high-order multimaterial simulation provides a meaningful insight into how material interface dynamics affect the ignition response of energetic materials under a shock loading.
As an experiment investigation, the effects of ethanol blended gasoline fuel with different injection method on nano-sized particle emission characteristics were examined in a 0.5L spark-ignited single-cylinder engine with a compression ratio of 10. Because this engine nano-particles are currently attracting interest due to its adverse health effects and their impact on the environments. So a pure gasoline and an ethanol blended gasoline fuels, namely E85 fuel, used for this study. And, as a particle measuring instrument, a fast-response particle spectrometer (DMS 500) with heated sample line was used for continuous measurement of the particle size and number distribution in the size range of 5 to 1000nm (aerodynamic diameter). As this research results, we found that the effect of ethanol blending gasoline caused drastic decrease of nano-particle emissions when port fuel injection was used for making better air-fuel mixture than direct fuel injection. Also injection timing, specially direct fuel injection, could be a dominant factor in controlling the exhaust particle emissions.
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