Effects of Tank Shape on the Roll Dynamic Response of a Partly Filled Tank Vehicle

The directional response and roll stability characteristics of a partly filled tractor-semitrailer vehicle, equipped with various cross-section tanks, are investigated as functions of fill volume and steer inputs. The tank-vehicle combination is analytically modeled upon integrating a quasi-static roll plane model of a partly filled tank of generic cross-section with a three-dimensional directional dynamic model of a five-axle tractor-semitrailer vehicle, assuming constant forward speed. The vehicle model is analyzed for different cross-sections of partly filled tanks, including circular, modified-oval and two optimal cross-sections. The directional response characteristics of the vehicle are evaluated to study the influence of partial-fill condition, steering maneuver, and vehicle speed on the roll dynamic performance of the tank cross-section and the vehicle. A comparison of the response characteristics, in terms of variations in cargo c.g. shift and roll mass moment of inertia, roll angle, lateral acceleration and yaw rate of the trailer sprung mass, revealed that the optimal tank geometry yields considerably less variations in the cargo c.g. coordinates and can thus significantly enhance the directional response and roll stability characteristics of partly-filled tank vehicles.     

Numerical simulation of viscous liquid sloshing by moving-particle semi-implicit method

A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method （ICCG）, the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface.     

Strip method for a laterally drifting ship in waves

Lateral drift occurs due to the effects of wind forces, wave drifting forces, or both on ships sailing in actual seas. It is important therefore to investigate the influence of lateral drift on seakeeping performance for improved ship operation. The velocity potential was expanded as an asymptotic power series in terms of the lateral speed parameter, τ, defined as ω _e V ₀/g, where ω _e is the frequency of wave encounter; V ₀ denotes the lateral velocity, which is assumed to be sufficiently small; and g is the acceleration due to gravity. By combining this technique with the strip method, two sets of motion equations of all the hydrodynamic force coefficients for ship seakeeping were derived. The first set is for ships without lateral drift and is the same as the equations in the new strip method, and the second set is for the additional motions induced by lateral drift. It was found that all ship motion modes except surge are coupled when a ship drifts laterally in waves.     

Confidence bounds on structural reliability estimations for offshore platforms

Second-order estimates to measure platform reliability are generated and used to provide an additional space to select safety margins appropriate to the owner's perception or for risk-averse managers. The aleatory and epistemic uncertainties in the parameters of an offshore platform are explicitly considered in the reliability analysis and the platform structural reliability becomes a random variable, assessing then the beneficial effects of a reduction on these uncertainties. One of these benefits is for risk-aversive managers who often demand additional room to make conservative decisions regarding reliability estimations. Proposed here is a procedure to generate the frequency diagram of platform reliability with the use of confidence bounds to support reliability and cost decisions based on percentiles instead of mean values. The concepts are illustrated through a typical offshore platform in Mexico. The frequency diagram of the platform reliability index is built for several alternative designs and three levels of epistemic uncertainty. The results may be applied for decision making on new designs and also on the assessment and optimal inspection, retrofit, and decommissioning of existing platforms.     

Two-phase evaporative battery thermal management technology for EVs/HEVs

Electric vehicle’s motor draws power from battery to meet its power demand in different road profiles. Battery high discharged currents are causes of warming battery’s cells. The temperature of 40 ºC and above reduces battery life span. The rationale of fuzzy controlled evaporative battery thermal management system (EC-BThMS) development from this study is to control the battery temperature in the range of 20 ~ 40 ºC both in charging/discharging modes. The proposed system has been developed with estimating the total cooling loads and thermal behavior of the battery cells. A fuzzy controlling system has been introduced with the EC-BThMS to control the electro-compressor and the expansion valve based on the response of battery temperature sensors.A battery pack of 8.6 kWh equipped EV has been operated with 60 km/h on 0 % gradient and 40 km/h on 5 % gradient in IIUM campus while 130 km/h on 0 % gradient and 50 km/h on 3.67 % gradient in Malaysia International Formula circuit to study the battery temperature profile and percentage of battery power saving. Comparison has been made on the performance of EC-BThMS with air cooling battery thermal management system (AC-BThMS) by using same vehicle. Result shows that EC-BThMS can save energy 17.69 % more than AC-BThM 1 and 23 % more than AC-BThM 2.     

Coupled thermo-mechanical analysis and shape optimization for reducing uneven wear of brake pads

In vehicle braking systems, the non-uniform contact pressure distribution on the brake pad is a major cause of uneven wear. The experimental approach of the wear phenomenon is the time consuming and costly. For this reason, a threedimensional finite element (FE) model of a brake system is presented for numerical simulation in this paper. A coupled thermo-mechanical analysis is carried out to confirm the non-uniform contact pressure distribution. A correlation between the non-uniform contact pressure and uneven wear is confirmed by measuring the amount of wear in the brake pad. The shape optimization of the brake pad is performed to reduce the uneven wear. In addition, the simulation results, such as natural frequency and temperature, are compared to experimental results.     

Aerodynamic study of a generic car model with wheels and underbody diffuser

Being a continuous subject of research, this study presents new aspects regarding the relevance of underbody diffusers in road vehicle aerodynamics. Using a generic car model on wheels as a reference, the effect of the wheels on the body fitted with an underbody diffuser was studied, where the diffuser length and angle were varied within ranges which are applicable for hatchback passenger cars. The results show that the vortices which originate from the rear wheelhouses have a major impact on the aerodynamics of the underbody diffuser, which results in increasing of drag and lift of the body. For cases studied, the average drag and lift increment due to the addition of wheels were (Δc_D)_mean = 0.058, respectively (Δc_L)_mean = 0.243. The lift of the body on wheels decreases with both diffuser length and diffuser angle, and there are situations when it may become negative as for a body without wheels. The results show also the possibility to reach a minimum drag according with normalised diffuser length.     

Energy management and design optimization for a series-parallel PHEV city bus

Series-parallel PHEV city buses combine the advantages of series and parallel configurations and have been used in China. However, the design and energy management of series-parallel PHEV city buses based on Chinese driving conditions still need to be investigated. In this paper, an equivalent consumption minimization strategy is provided to optimize energy management for series-parallel PHEV city buses, and the process of the equivalent consumption minimization strategy for series-parallel is presented in this paper. Compared with the validated rule-based energy control strategy, ECMS shows a fuel economy improvement of 8.2 % in the CBCD (Chinese Bus Driving Cycle). Based on the optimal energy management, a design for a generator motor in the series-parallel configuration has been processed. The fuel consumption has been shown to decrease, with an increase in generator power, because the system with the higher generator power can work at a higher efficiency in the series mode and operate the engine in the high efficiency area in the parallel mode. Besides, in terms of costof- ownership for a PHEV bus for lifetime of 8 years, although the high generator power will lead to high purchase cost for series-parallel PHEV bus, a series-parallel PHEV city bus with a generator of 100 kW maximum power will still show small advantage in cost-of-ownership, based on current motor price and natural gas price.     

Evaluation and Measurement the Recovered Energy from Automobile Suspension in the Operation Conditions

The purpose of this paper is to verify if it is possible to recover the energy from automobile suspensions, using a system who replace the shock absorber. The system consists of an electric generator, a mechanical system for transforming the translation of body car in rotational movement and an electronic control system. The tests were made on three road types, according to ISO 8608/1995 with four different driving speeds. The results showed that a significant quantity of energy was recovered during the test on inferior type of road, even at reduced speed. For the superior type of the road, the energy can be recovered only at high speed. The parameters that influences the system capacity of recovering energy are gross weight of the vehicle, road type and the vehicle speed.     

Gaussian Process Regression Feedforward Controller for Diesel Engine Airpath

Gaussian Process Regression (GPR) provides emerging modeling opportunities for diesel engine control. Recent serial production hardwares increase online calculation capabilities of the engine control units. This paper presents a GPR modeling for feedforward part of the diesel engine airpath controller. A variable geotmetry turbine (VGT) and an exhaust gas recirculation (EGR) valve outer loop controllers are developed. The GPR feedforward models are trained with a series of mapping data with physically related inputs instead of speed and torque utilized in conventional control schemes. A physical model-free and calibratable controller structure is proposed for hardware flexibility. Furthermore, a discrete time sliding mode controller (SMC) is utilized as a feedback controller. Feedforward modeling and the subsequent airpath controller (SMC+GPR) are implemented on the physical diesel engine model and the performance of the proposed controller is compared with a conventional PID controller with table based feedforward.