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Technical Paper

Computational design of commercial vehicle for reconciling aerodynamics and engine cooling performance

As the global environmental protection becomes the world consensus recently, the regulations of the fuel consumption and the exhaust gas have large effects on the performance and the fundamental structure of commercial vehicles. Especially the technology concerning "fluid" and "heat" has a close relationship with those issues. Owing to above circumstances, commercial vehicles such as large trucks and buses are forced to be designed near the limit of allowance. Furthermore, a rapid design is another requirement. However, though significant number of variations, i.e., cab configuration, wheel base, rear body configuration, engine specification, etc., are prepared, it is impossible to improve the performance of all those combinations by experiments which cost a lot. Accordingly, the quantitative prediction using computer will become indispensable at the beginning term of new car development.
Technical Paper

Booming noise analysis of passenger car using integrated approach of CAT/CAE

The need of lightweight vehicle design is motivated by the recent global trend of less fuel consumption and lower emission in vehicle. However in NVH development of vehicle, it becomes more difficult for the lightweight vehicle to reach low vibro-acoustic sensitivity than, for the heavy weight one to do so. Inthis environment, this paper describes about the practical finite element (FE) modeling of vehicle structure and acoustics, in order to predict "boom" response to powertrain excitation. The FE modeling process through validation and updating with experimental mode makes, the accumulation of considerable expertise for improving prediction accuracy, possible. FE analysis based on this modeling process is so useful for predicting "boom" levels up to 200 Hz. Using the result of FE analysis, structural optimization is executed in order to improve "boom" level of 80 Hz.
Technical Paper

Prediction of Occupant's Thermal Sensation under the Transient Environment in a Vehicle Compartment

New numerical simulation system and experimental evaluation system has been developed to predict and evaluate occupant's thermal sensation in a passenger compartment in which environment is not steady and not uniform. Transitional effective temperature, which is new index of thermal sensation, is proposed and verified to correspond with subjects' thermal sensation votes. The simulation system has two advantage beside the prediction of thermal sensation; automatic generation of a computational model and coupling analysis of temperature including an analysis of temperature distribution inside a cabin, refrigerating cycle, solar radiation, and so on. It was verified that this system well predicts occupant's thermal sensation in a short time.
Technical Paper

A Study on the Effects of the Active Yaw Moment Control

This paper presents a new torque distribution system-“Right/Left Torque Control System”, aimed at improving a vehicle's cornering properties by using yaw moment control. The torque transfer mechanisms of this system have been analyzed. Also, a yaw moment control algorithm using yaw rate feedback control has been designed. Next, vehicle cornering properties were evaluated using numerical simulation developed from data taken from an actual vehicle. As a result, improvements were achieved in the maneuverability and stability of a vehicle during cornering.
Technical Paper

Optimization of In-Cylinder Flow and Mixing for a Center-Spark Four-Valve Engine Employing the Concept of Barrel-Stratification

Flow and flame structure visualization and modeling were performed to clarify the characteristics of bulk flow, turbulence and mixing in a four-valve engine to adopt the lean combustion concept named “Barrel-Stratification” to the larger displacement center-spark four-valve engine. It was found that the partitions provided in the intake port and the tumble-control piston with a curved-top configuration were effective to enhance the lean combustion of such an engine. By these methods, the fuel distribution in the intake port and the in-cylinder bulk flow structure are optimized, so that the relatively rich mixture zone is arranged around the spark plug. The tumble-control piston also contributes to optimize the flow field structure after the distortion of tumble and to enable stable lean combustion.
Technical Paper

Analysis of Vehicle Wind Throb Using CFD and Flow Visualization

Passenger cars with sunroofs sometimes experience a low frequency pulsation noise called “wind throb” when traveling with the roof open. This “wind throb” should be suppressed because it is an unpleasant noise which can adversely affect the acoustic environment inside a car. In this paper, 3-dimensional numerical flow analysis is applied around a car body to investigate the wind throb phenomenon. The computational scheme and the modeling method of the car body is first described. A flow visualization test in a water tunnel was completed for the simple car body shape to compare against the numerical procedure. The numerical and the visualized results compared well and the numerical simulation method employed was considered to be a reliable tool to analyze the wind throb phenomenon. Calculated results of pressure and vorticity distribution in the sunroof opening were analyzed with the spectrum of pressure fluctuation at the sunroof opening with and without a deflector.
Technical Paper

Control Method of Autonomous Vehicle Considering Compatibility of Riding Comfort and Vehicle Controllability

This paper describes a control strategy for autonomous vehicles in an intelligent vehicle/highway system. The control concept aims at the compatibility of passenger riding comfort and vehicle controllability. The main subject of this paper is lateral control of vehicles. In order to analyze riding comfort, we have experimented on the lateral riding comfort during a lane change. It was found that the riding comfort is mainly related to the jerk more than the acceleration, and that the trajectory pattern is important. According to the experimental results, a motion control system was designed. We found through the computer simulation and the experiment with an autonomous test vehicle that comfortable ride is realized along with system stability. Lastly, in order to apply this strategy to the longitudinal direction, we have experimented on the longitudinal acceleration with the test vehicle. The results shows that the same strategy is applicable to the longitudinal direction.
Technical Paper

Collapse of Thin-Walled Curved Beam with Closed-Hat Section - Part 2: Simulation by Plane Plastic Hinge Model

This paper describes a calculating method to predict the quasi-static collapsing behaviors of spot-welded closed-hat section curved beams under axial compression. The overall deformat ions and the local buckling modes of beams were calculated using a geometrical model. Force-displacement relations were predicted by a elastic-plastic structural analysis method using the ‘plastic hinge’ concept. Collapsing tests were made on beams which are differenting section size, rotation angle, and metal sheet thickness. Comparisons between the calculated and experimental results of deformed shapes of beams, the local buckling modes and the force displacement relations are discussed.
Technical Paper

Reduction of Idling Rattle Noise in Trucks

Optimization of the clutch torsional characteristics is one of the effective methods to reduce the idling rattle noise. Many researches on th.s problem have been reported, but only few of them give sufficient consideration to the drag torque applied to the clutch disc during engine idling. This paper pays attention to the drag torque and discusses the mechanism of idling rattle noise by using vehicle testing, bench test with rotating torsional exciter and computer simulation. Reauction of Idling
Technical Paper

A Study on a Simulation of a Head Form Impact Against Plastic Plates

A Finite Element Method (FEM) simulation was conducted to predict energy-absorbing characteristics in an impact of a head form against plastic plates. Static and dynamic material tests were conducted in order to determine material properties of the plastics. The properties were applied in an explicit FEM code. The FEM results were validated through the impact tests by the head form against the same plastic plates. It was proved that the FEM could simulate the test result well, when the precise material properties were introduced in the simulation. The method can be expected to be available to predict energy-absorbing characteristics during the impact by the head form against automobile plastic components such as shell portions of instrument panels.
Technical Paper

Ventilation Characteristics of Modeled Compact Car Part 3 Airflow Velocity Distribution with Foot Mode

Following the previous reports, ventilation characteristics in automobile was investigated by using a half-scale car model which was created by the Society of Automotive Engineers of Japan (JSAE). In the present study, the ventilation mode of the cabin was foot mode which was the ventilation method for using in winter season. Supplied air was blown from the supply openings under the dashboard to the rear of the model via the driver's foot region in this mode. The experiment was performed in order to obtain accurate data about the airflow properties equipped with particle image velocimetry (PIV). Our experimental data is to be shared as a standard model to assess the environment within automobiles. The data is also for use in computational fluid dynamics (CFD) benchmark tests in the development of automobile air conditioning, which enables high accuracy prediction of the interior environment of automobiles.
Technical Paper

Powertrain Model Selection and Reduction for Real Time Control Algorithm Design and Verification in Rapid Controller Prototyping Environment

New systems or functionalities have been rapidly introduced for fuel economy improvement. Active vibration suppression has also been introduced. Control algorithm is required to be verified in real time environment to develop controller functionality in a short term. Required frequency domain property concept is proposed for representation of target phenomena with reduced models. It is shown how to select or reduce engine, transmission and vehicle model based on the concept. Engine torque profile which has harmonics of engine rotation is required for engine start, take-off from stand still, noise & vibration suppression and misfire detection for OBD simulation. An engine model which generates torque profile synchronous to crank angle was introduced and modified for real time simulation environment where load changes dynamically. Selected models and control algorithms were modified for real time environment and implemented into two linked universal controllers.
Technical Paper

The Prediction of Refrigeration Cycle Performance with Front End Air Flow CFD Analysis of an Automotive Air Conditioner

The purpose of this paper is to present a prediction method for the refrigerator performance of an automotive air conditioner (A/C). In order to predict the refrigerator performance in arbitrary situations, we consider the thermal equilibrium of the refrigeration cycle through A/C components, as the compressor, the evaporator and the condenser. These components are affected by the thermal property of the refrigerant. Influences of circumstantial flow and temperature field in the engine compartment also are reflected upon, because the cooling performance of the condenser is sensitive to that. In this paper, we try to derive algebraic models for the major components with regard to the thermal equilibrium in the refrigeration cycle. Furthermore, we use a Computational Fluid Dynamics analysis (CFD) for the prediction of cooling airflow temperature in the engine compartment, which is another essential factor in determining the state of the refrigeration cycle.