Study on shaft alignment of propulsion shafting system depending on single reaction force supporting position of aft stern tube bearing

Journal of Marine Science and Technology - Trends of large-scale ships have seen propulsion shaft and propeller sizes increase. This has enabled shafts to have greater stiffness, yet has caused...     

Service design for public transportation to address the issue of females’ fear of crime

Transportation - In conjunction with their gender, how does the current design of public transport services affect female passengers’ feelings of safety and fear when using the service? This...     

A tyre slip-based integrated chassis control of front/rear traction distribution and four-wheel independent brake from moderate driving to limit handling

This paper presents a tyre slip-based integrated chassis control of front/rear traction distribution and four-wheel braking for enhanced performance from moderate driving to limit handling. The proposed algorithm adopted hierarchical structure: supervisor – desired motion tracking controller – optimisation-based control allocation. In the supervisor, by considering transient cornering characteristics, desired vehicle motion is calculated. In the desired motion tracking controller, in order to track desired vehicle motion, virtual control input is determined in the manner of sliding mode control. In the control allocation, virtual control input is allocated to minimise cost function. The cost function consists of two major parts. First part is a slip-based tyre friction utilisation quantification, which does not need a tyre force estimation. Second part is an allocation guideline, which guides optimally allocated inputs to predefined solution. The proposed algorithm has been investigated via simulation from moderate driving to limit handling scenario. Compared to Base and direct yaw moment control system, the proposed algorithm can effectively reduce tyre dissipation energy in the moderate driving situation. Moreover, the proposed algorithm enhances limit handling performance compared to Base and direct yaw moment control system. In addition to comparison with Base and direct yaw moment control, comparison the proposed algorithm with the control algorithm based on the known tyre force information has been conducted. The results show that the performance of the proposed algorithm is similar with that of the control algorithm with the known tyre force information.     

Vibration transmission reduction from a centrifugal turbo blower in a fuel cell electric vehicle

This paper presents a multi-body flexible dynamic analysis of a centrifugal turbo blower for a fuel cell electric vehicle (FCEV) based on the application of computer-aided engineering (CAE) to predict the acceleration at the mount position of the blower. This predicted acceleration is validated by using the measured acceleration data. The numerical simulation for the multi-body flexible dynamics of the blower is used not only to identify the most effective mount among four mounts in an FCEV by controlling the complex stiffness of the isolator, but also to suggest the range of complex stiffness of the isolator at the most effective mount. This numerical simulation technology can be useful for the estimation of the variation of vibration transmission for the structural modification of the turbo blower.     

Crash protection of Hybrid Electrical Vehicles for amending the KMVSS No. 91

This paper explores issues related to the electrical safety of Hybrid Electrical Vehicles (HEVs) during and after various crash events. Japanese and American federal regulations regarding occupant protection against high voltages in Electric Vehicles (EVs) and HEVs were surveyed and analyzed in this study. Front, side and rear impact tests for two types of HEVs were conducted to investigate electrolyte spillage, the retention of the propulsion battery system and the electrical isolation of the occupant. The test results met the related criteria. The test procedures and the criteria for occupant protection established through this study were amended to Korean Motor Vehicle Safety Standard (KMVSS) No. 91 to add the crash protection of the EVs and the HEVs.     

Development of electrostatic diesel particulate matter filtration systems combined with a metallic Flow-Through Filter and electrostatic methods

A 3000 cc diesel engine attached to an engine dynamo was used to test three newly developed electrostatic Diesel Particulate matter filtration Systems (DPS 1, 2, and 3) under four steady-state engine operating conditions: idle, 2000 rpm with no load, and 2000 rpm under 25% and 50% loads. Of the two developed alternatives, DPS 1 and DPS 2, DPS 2 comprises an ionization section, electrostatic field additional section and Flow-Through Filter (FTF), which achieved almost 90% removal of particulate matter (PM) under the engine’s operating conditions, and the efficiency of the FTF was maintained between 20% and 50%. Comparing the long-term performance of DPS 2 and DPS 3 (effectively a serial combination of two DPS 2s) with a commercially-available Diesel Particulate Filter (DPF), the DPS 2 and DPS 3 achieved almost the same efficiency for removing PM as the DPF but had significantly improved (75%∼90% lower) differential pressure drops.     

Design of power split transmission: Design of dual mode power split transmission

The power split type hybrid system transmits engine power by dividing it into the electrical unit and the mechanical unit. Its power transmission efficiency is highest at the mechanical point (MP), where the full power is transmitted to the mechanical unit. In this study, the equation for the MP was derived for the gear ratios of a general 4-node lever model. The MP characteristics for the transmission ratio (TR) of the input split and compound split structures were examined using the equation derived. Using the examined input split and compound split structures, a systematic design method for the dual mode power split transmission was proposed. In the dual mode power split transmission, the MP could be positioned at the desired TR, and the input split and compound split modes could be selectively used according to the clutch combination, which leads to the operation of the vehicle within a high system efficiency range.     

Design and optimization of an LPG roller vane pump for suppressing cavitation

A roller vane type liquefied petroleum gas (LPG) pump was developed for a liquid phase LPG injection (LPLi) engine. Most of the LPG pumps used in the current LPLi engines are installed inside of the LPG tank, but this pump is intended to be installed outside of the LPG tank to overcome the difficulty of fixing an in-tank pump. Because LPG has a low boiling point and high vapor pressure, it usually causes cavitation in the pump and consequently deteriorates the flow rate of the pump. The purpose of this work is to optimize the design of the roller vane pump in order to suppress cavitation and increase the fuel flow rate by using a computational fluid dynamics (CFD) analysis. In order to achieve these goals, the intake port configuration and the rotor of the roller vane pump were redesigned and simulated using STAR-CD code. Computation was performed for six different models to obtain the optimized design of the roller vane pump at a constant speed of 2600 rpm and a constant pressure difference between the inlet and outlet of 5 bar. The computation results show that an increased intake port cross-section area can suppress cavitation, and the pump can achieve a higher flow rate when the rotor configuration is changed to increase its chamber volume. When the inlet pressure difference is 0.1 bar higher than the fluid saturation pressure, the pump reaches its maximum flow rate.     

Simple estimation of high-frequency radiation from a muffler shell

The acoustic design of exhaust mufflers has mainly focused on reducing the discharge noise from the tailpipe. However, the noise that is transmitted through the muffler jacket and the endplate becomes important since the muffler reduces the amount of discharge noise when it has an optimized design. It is known that the contribution to the overall exhaust noise of the muffler shell is significant in the mid- and high-frequency ranges. The current problem is that there are no appropriate computational tools at high frequencies. A simple method to analyze the 1/3-octave band of sound radiating from an arbitrary shape (like a muffler) was employed to predict the band spectrum of the radiated noise. The calculation method included formulating the boundary integral, which was modified into a quadratic form in order to enable the prediction of the intensity levels in a band analysis. Monopole and dipole source terms in the conventional BEM were transformed into the auto- and cross-spectra of the two vibrating sources, in which the cross-spectra could be eventually omitted by assuming that the correlation coefficients were negligible. The method was adopted in an abrupt calculation of the shell noise in 1/3-octave band levels without nonuniqueness problem. In comparison with the measured data, the simulation result showed roughly 3-dB errors at most of the field points, excluding several special points that were normal to the shell and exhibited a maximum 5-dB error.     

Conceptual design of economic hybrid vehicle system using clutchless geared smart transmission

Most hybrid vehicles employ the continuously variable transmission (CVT or eCVT) currently as their choice of the transmissions. Recently, an automated geared transmission (AGT) or dual clutch transmission (DCT) is being tried for some hybrid vehicles for the better fuel economy than the CVT hybrid. However, this AGT or DCT is using automated clutches which require the hydraulic power in addition to the slippage in the clutch plate invoking some energy loss as well as wear. Also, they require a motor with significant power to match to the engine power. The clutchless geared smart transmission (CGST) has no clutch and the clutch function is performed by a planetary gear system controlled by a motor-generator. The hybrid vehicles proposed here using CGST may have some merits in durability, fuel efficiency, and cost since they do not have clutches. The motor used for the clutch function can be also working for power merge with the engine in propelling the vehicle. The proposed hybrid system can be either mild hybrid or full hybrid by adopting a different capacity of battery with much smaller motor-generator due to the planetary gear system compared to the other type hybrid vehicles. In this study, the prospects of newly proposed CGST hybrid system are examined in practical aspects compared with AGT hybrid or DCT hybrid systems.