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A simulation framework for vehicle aerodynamics using up to 10 billion fully unstructured cells has been developed on a world-fastest class supercomputer, called the K computer, in Kobe, Japan. The simulation software FrontFlow/red-Aero was fully optimized on the K computer to utilize up to 10,000 processors with tens of thousands of cores. A hybrid parallelization method using MPI among processors and OpenMP among cores inside each processor was adopted. The code was specially tuned for unsteady aerodynamic simulation including large-eddy simulation, and low Mach number approximation was adopted to avoid excessive iterations usually required for the fully incompressible algorithm. The automated mesh refining system was developed to generate unstructured meshes of up to 10 billion cells. In the system, users only generate unstructured meshes in the order of tens of millions of cells directly using commercial preprocessing software.

This paper describes our attempts to improve the power generation efficiency of single-phase permanent magnet generators of outer-rotor type for motorcycles by their reducing electric losses (iron loss and copper loss) by electromagnetic analysis. In this study, we first broke down the electric losses into iron loss and copper loss by electromagnetic analysis. Then, focusing on the iron loss that the loss ratio was high, we modified the thickness and material of the stator core sheets and reduced the iron loss in the non-magnetic protection covers of the magnets on the rotor, and thus improved power generation efficiency. Further, we analyzed the flow of magnetic flux and magnetic flux density and found that it would be effective against leakage of the flux between the magnets if we spaced the magnets, which we did and which also allowed us to reduce the amount of magnets used.

For better performance of outboard motors for high speed craft, improvement in the performance of the propeller strut located ahead of the propeller is indispensable in addition to ameliorating the performance of the screw propeller itself. Thus, it is extremely important to reduce the drag of the propeller strut, which accounts for the predominant portion of the submerged parts of the motor and hull when the craft is running at high speed and to improve the propeller efficiency in the wake of the propeller strut. This paper, taking up two different shapes of the propeller strut, compares the performances of the propeller placed in the wake of the propeller strut in tank tests, and discusses the drag of the propeller strut. The two propeller strut shapes are that of a 70% scaled down model of the propeller strut SUZUKI's 200 PS outboard motor and its improved version.

Currently, the improvement of fuel economy is the most important issue in automobile engine development. To improve fuel economy via greater thermal efficiency, the enhancement of the compression ratio and the reduction of thermal losses because of cooling have been widely investigated. These efforts to improve thermal efficiency increase the thermal load on pistons. Ensuring the reliability of the pistons and the antiknocking capacity of engines require a better understanding of piston temperature distributions through accurate measurements under various engine operating conditions. Thus, direct and indirect measurement methods have been developed to estimate the actual piston temperature. Direct methods, such as linkage-type measurements, are not typically applicable under higher engine speeds because of the poor durability of linkages.

The critical change in drag occurring on the Ahmed body when the slanted base has an angle of 30° is due to a transition in the wake structure. In a previous study on flow analysis across the Ahmed body, we investigated the unsteady wake experimentally using hot-wire and particle image velocimetry measurements. However, because the experimental analysis yielded limited data, the spatially unsteady wake behaviour, interaction between the trailing vortex and transverse vortices (up/downwash), and flow mechanism near the body were not discussed sufficiently. In this study, the unsteady wake structures were analysed computationally using computational fluid dynamics to understand these issues, and the hypothesis was tested. The slant angle was 27.5°, which is identical to that in the experiment and corresponds to a high drag condition indicated experimentally.

When the planing craft with outboard motor is running, cavitation occurs around the surface of propeller and lower unit of outboard motor. Cavitation has been classified under several categories by the feature and cause of occurrence. Among them, cloud cavitation and root cavitation lead to erosion damage on the surface of lower unit and propeller. To prevent from poor appearance or performance deterioration of outboard motor by erosion damage, it is important problem to predict the erosion occurrence. Currently we can predict the cavitation phenomena sufficiently, but the area of cavitation does not necessarily correspond with the area of erosion. In this study, we present the new method to predict the area of erosion due to cavitation using CFD (computer fluid dynamics) analysis. In order to evaluate the accuracy of erosion occurrence simulation, the simulation results are compared against the result of a full-scale cruising test.

Reduction of flow resistance in an intake system is essential for increasing the output of a four-stroke engine. Evaluation method regardless engine displacement or number of valves or cylinder must be required in intake system design. This study proposes intake loss coefficient as total evaluation method from flow in an intake port to charging flow into a cylinder. A three-dimensional, general-purpose Computational Fluid Dynamics (CFD) code was used to calculate an intake loss coefficient. A correlation was confirmed between an intake loss coefficient and the engine power output. Intake loss coefficients and the CFD technique may be used for efficient optimization of the shape of an intake system.

In open-grille vehicle aerodynamics simulation using computational fluid dynamics, in addition to basic flow characteristics, such as turbulent flow with a Reynolds number of several million on the bluff body, it is important to accurately estimate the cooling air flow introduced from the front opening. It is therefore necessary to reproduce the detailed geometry of the entire vehicle including the engine bay as precisely as possible. However, there is a problem of generating a good-quality calculation grid with a small workload. It usually takes several days to a week for the pretreatment process to make the geometry data ‘clean’ or ‘watertight’. The authors proposed a computational method for complex geometries with a hierarchical Cartesian grid and a topology-independent immersed boundary method with dummy cells that discretize the geometry on a cell-by-cell basis and can set an imaginary point arbitrarily.

In recent years, one of the most important issues in the automotive industry is the improvement of fuel economy started from the environmental problem. Making cars lighter and reducing the coefficient of friction are two ways to improve fuel economy. Reducing the weight of a cylinder, an engine component, is a typical example. The traditional, mainstream method to reduce cylinder weight has been to convert cast iron cylinder blocks into aluminum cylinder blocks by using cast iron sleeves. To further make engines lighter and more compact, however, it is desirable that cast iron sleeves be abolished, or, in other words, making cylinder blocks sleeveless. A typical technology to make cylinder blocks sleeveless is applying anti- wear coating on a bore wall. Electroplating is currently the mainstream method used for this technology. It must be noted, however, electroplating is used primarily for low-pressure cast cylinders.

One of the fuel efficiency improvement policy of Small vehicle included Regenerative Braking System (JSAE 20139006 / SAE 2013-32-9006), but developed New Compact Hybrid System to realize further fuel efficiency improvement. The previous system has losses for the engine friction when deceleration energy is collected, but the new system realizes effective regeneration with separating the engine. The new system collect deceleration energy in decelerating time and coasting as well as the previous system, but the fuel consumption with the engine is minimized by running EV with the collected energy and realize further fuel efficiency improvement. In addition, the assist is also performed with collected energy, so both good efficiency and good accelerating performance are realized. This system adopts Auto Gear Shift® system (following, AGS) which is based on a manual transmission.

The objective of this paper is to investigate the potential of lean burn combustion to improve the thermal efficiency of spark ignition engine. Experiments used a single cylinder gasoline spark ignition engine fueled with primary reference fuel of octane number 90, running at 4000 revolution per minute and at wide open throttle. Experiments were conducted at constant fueling rate and in order to lean the mixture, more air is introduced by boosted pressure from stoichiometric mixture to lean limit while maintaining the high output engine torque as possible. Experimental results show that the highest thermal efficiency is obtained at excess air ratio of 1.3 combined with absolute boosted pressure of 117 kPa. Three dimensional computational fluid dynamic simulation with detailed chemical reactions was conducted and compared with results obtained from experiments as based points.

The aerodynamic performance of new vehicles is commonly determined using computational fluid dynamics (CFD) and wind tunnel tests. The final assessment is carried out by actual running tests. In particular, ideas regarding fuel consumption improvement that relate to components for the reduction of the coefficient of drag (CD) value are evaluated by coast-down tests. However, a difference often exists between the component's efficiency between wind tunnel tests and coast-down tests. Therefore, we focused on the efficiency of an air-dam spoiler in reducing CD values. A comparison was made between the aerodynamic effect of the air-dam spoiler in wind tunnel and coast-down tests in terms of the CD value and the wake structure behind the vehicle. To determine the relationship between the CD value and the wake structure behind the vehicle, we measured vehicle speed, wind velocity and direction, vehicle height, and pressure distribution on the back door.

We have developed a small-displacement gasoline direct-injection engine (1.3L). Gasoline direct-injection engines rely on ultra-lean stratified combustion to deliver significantly better fuel economy, and are already used in many practical applications. When gasoline direct-injection is applied to a small-displacement engine, however, the amount of wall wetting of fuel on the piston surface will increase because the traveled length of the fuel spray is short. This may result in problems such as smoke production, high emissions of unburned HC, and poor combustion efficiency.