Prediction Method of Snow Ingress Amount into the Engine Air Intake Duct Employing LES and Detailed Snow Accumulation Model
動画引用元論文
Prediction Method of Snow Ingress Amount into the Engine Air Intake Duct Employing LES and Detailed Snow Accumulation Model
- 著 者
- Kunihiko Yoshitake, Naoshi Kuratani, Fortunato Nucera, Akihisa Nikami, Akio Takamura
- 収 録
- 2019 WCX SAE World Congress Experience
- 発 行
- April 2, 2019
- 要 旨
- When a vehicle is driven in snowy conditions, if a proper air intake design is not adopted, the snow lifted by the leading vehicles may penetrate into the engine air intake, in case of large snow ingress amount, causing a power drop. The evaluation of such risk for the intake is carried out through climatic wind tunnel tests, which cannot be conducted at the early stage of vehicle development when the prototype vehicle does not exist. In order to study that risk prior to the prototype vehicle delivery, computational fluid dynamics (CFD) which predicts the snow ingress amount accurately was established with taking into account unsteady air flow and snow accumulation. Large Eddy Simulation (LES) was used to reproduce the unsteady flow field, leading to a good agreement of the flow downstream from the snow generator with the experimental one measured by Particle Image Velocimetry (PIV). As for the snow particle behavior model, the Lagrangian method was chosen. In order to study the snow tracking property, the velocity difference between air flow and snow particles was measured by PIV, whilst super-slow snow particle motions were visualized with a high speed camera. Through comparison between experimental results and customized CFD results, non-spherical drag coefficient and turbulent dispersion are found to be crucial to reproduce the tracking properties. Regarding the restitution coefficient at the walls, elastic-plastic deformation and surface friction were taken into account. In addition, an accumulation model was developed, in order to stop the particles and force them to accumulate at the wall when a certain criterion is satisfied. The accumulation model also takes into account the accumulation height limitation by recognizing the height of the flow path. The snow ingress amounts of CFD implementing those new techniques showed good correlation with experimental results for multiple vehicle categories.
Speaker
吉武 邦彦 / Kunihiko Yoshitake
その他 執筆論文（共著含む）
Prediction Method for Water Intrusion into the Engine Air Intake Duct while Running on Flooded Road at the Early Stage of Vehicle Development
- 著 者
- Kunihiko Yoshitake, Hiroyuki Tateyama, Atsushi Ogawa
- 収 録
- SAE Int. J. Passenger. Cars - Mech. Syst.
- 発 行
- 2017年3月
- 要 旨
- Vehicles are required durability in various environments all over the world. Especially water resistance on flooded roads is one of the important issues. To solve this kind of problem, a CFD technology was established in order to predict the water resistance performance of the vehicle at the early development stage. By comparison with vehicle tests on flooded roads, it is clarified the following key factors are required for accurate prediction; the vehicle velocity change, the vehicle height change and the air intake flow rate. Moreover, these three key factors should be appropriately determined from vehicle and engine specification to predict water intrusion for flooded roads at the early stage of development. In this paper, a methodology which determines appropriate analysis conditions mentioned above for flooding simulation from vehicle and engine specification is described. The methodology enables us to determine whether the vehicle provides sufficient waterproofness. Further, it is confirmed that the CFD with the methodology can successfully reproduce critical phenomena for water intrusion into the air intake duct.
Development of Cooling Fan Model and Heat Exchange Model of Condenser to Predict the Cooling and the Heat Resistance Performance of Vehicle
- 著 者
- Yuichi Fukuchi, Kunihiko Yoshitake, Kazutaka Yokota
- 収 録
- SAE International Journal of Advances and Current Practices in Mobility
- 発 行
- 2020年4月
- 要 旨
- The cooling performance and the heat resistance performance of commercial vehicle are balanced with aerodynamic performance, output power of powertrain, styling, cost and many other parameters. Therefore, it is desired to predict the cooling performance and the heat resistance performance with high accuracy at the early stage of development. Among the three basic forms of heat transfer (conduction, convection and radiation), solving thermal conduction accurately is difficult, because modeling of “correct shape” and setting of coefficient of thermal conductivity for each material need many of time and efforts at the early stage of development. Correct shape means that each part should be attached correctly to generate the solid mesh with high quality. Therefore, it is more efficient and realistic method to predict the air temperature distribution around the rubber/resin part instead of using the surface temperature at the preliminary design stage. The air temperature distribution in the engine compartment is dominated by the flow distribution from fans, the heat rejected by heat exchangers, AC-generator and the convecting heat by surface temperature of parts. In the case of steady middle/high vehicle speed modes, thermal convection has larger effects on the air temperature distribution. To predict these phenomena with high accuracy, the fan model and condenser model are developed. The fan model provides the accurate P-Q performance based on a specification and the flow distribution based on the LES results of the sliding mesh method with low computational cost. The heat rejection by the condenser is concentrated around the inlet tube of core. To reproduce this distribution, the phase change of refrigerant is solved in the condenser model. The accuracy of these models is confirmed by using component experiments and vehicle measurements. Accuracy of heat-exchanger coolant temperature is within 2K and air temperature in the engine compartment is 5K respectively.