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The technology concerning thermo and fluid dynamics is one of the important fields which have made great progress along with rapid advance in computational resources. Especially, the CFD technology has been proved as successful contribution to the development of the engine cooling system. Therefore, this technology is widely used at early phase of the vehicle development. However, a serious problem has been remained that it does not always give practical precision. Particularly, the cooling fan is one of the primary components in the cooling system to determine the performance, while practical calculation method without depending on large resources has not established.

A cooling fan is one of the primary components affecting the cooling performance of an engine cooling system. In recent years, with the increase in electric vehicles (EVs) and hybrid vehicles (HVs), the cooling performance and noise level of the cooling fan have become very important. Thus, the development of a low-noise fan with the same cooling performance is urgently required. To address this issue, it is critical to find the relation between the performance of the fan and the flow structures generated around it, which is discussed in the present paper. Specifically, a computational method is employed that uses unsteady Reynolds-averaged Navier-Stokes (URANS) coupling with a sliding mesh (SLM). Measurements of the P-Q (Pressure gain-Flow rate) characteristics are performed to validate the predictive accuracy of the simulation.

This paper analyzes low-speed pre-ignition (LSPI), a sudden pre-ignition phenomenon that occurs in downsized boosted gasoline engines in low engine speed high-load operation regions. This research visualized the in-cylinder state before the start of LSPI combustion and observed the behavior of particles, which are thought to be the ignition source. The research also analyzed pre-ignition by injecting deposit flakes and other combustible particulate substances into the combustion chamber. The analysis found that these particles require at least two combustion cycles to reach a glowing state that forms an ignition source. As a result, deposits peeling from combustion chamber walls were identified as a new mechanism causing pre-ignition. Additionally, results also suggested that the well-known phenomenon in which the LSPI frequency rises in accordance with greater oil dilution may also be explained by an increase in deposit generation.

This paper evaluates the effect of our new alternator concept for a conventional vehicle, which is able to generate electricity by storing kinetic energy of the vehicle in the high speed flywheel as rotation energy under deceleration. The alternator constructs a planetary gear device and multiple clutch-brakes perform CVT, alternator and high speed flywheel without an expensive electric device, mechanical CVT and vacuum pump. So it has high cost performance.

Higher pressure and higher precision are required for diesel fuel injection equipment in response to increasingly severe emissions control regulations. Market diesel fuels have become more diversified than in the past. Diesel fuel quality has also been changing, being affected by crude oil slate, extreme lowering of sulfur content, and diesel reformulated from heavy fuel oil, among other reasons. As a result of this, deposits thought to have a fuel origin have been observed within diesel fuel injectors in certain regions. Related changes in fuel injection quantity have also been observed. This paper determines injector deposit production mechanisms. It focuses on the structural changes of deposit causative substances by temperature as well as injector design change improvements to prevent deposits.

Reduction of oil consumption of engines is required to avoid a negative effect on engine after treatment devices. Engines are required fuel economy for reduction of carbon-dioxide emission, and it is known that reduction of piston frictions is effective on fuel economy. However friction reduction of pistons sometimes causes an increase in engine oil consumption. Therefore reduction of engine oil consumption becomes important subject recently. The ultimate goal of this study is developing the estimation method of oil consumption, and the mechanism of oil upward transport at oil ring gap was investigated in this paper. Oil pressure under the oil ring lower rail was measured by newly developed apparatus. It was found that the piston slap motion and piston up and down motion affected oil pressure rise under the oil ring and oil was spouted through ring-gap by the pressure. The effect of the piston design on the oil pressure generation was also investigated.

A new ignition-combustion concept named PCC (Plume Ignition Combustion Concept), which ignite rich mixture plume in the middle of injection period or right after injection of hydrogen is completed, is proposed by the authors in order to reduce NOx emissions in high engine load conditions with minimizing trade-offs on thermal efficiency. In this study fundamental requirements of hydrogen jet to optimize PCC are investigated by using single and multi-hole nozzle with a combination of high speed laser shadowgraphy to visualize propagating flame. As a result, it was infered that igniting the mixture plume in the middle of injection period with minimizing jet penetration to chamber wall is effective reducing NOx formation even further.

Key requirements of engines for vehicles are large output power and high efficiency, low emission as well as small size and light weight. Hydrogen combustion engines with direct injection have the characteristics to meet these factors. Tokyo City University, former Musashi Institute of Technology, has studied hydrogen fueled engines with direct injection since 1971. The key technology in the development of hydrogen fueled engines is the hydrogen injector for direct injection with the features such as high injection rate, high response and no hydrogen gas leakage from the needle valve of the hydrogen injector. A common-rail type system to actuate the needle valves of the high pressure hydrogen injectors was intentionally applied to fulfill good performances such as large injection rate, high response and no hydrogen gas leakage.

To reduce friction is required to improve engine fuel economy. This study aimed to reduce piston skirt friction, which is a major factor in engine friction. ‘Soft skirt’ is a trendy item in recent gasoline engines, which can improve skirt sliding condition by larger deformation when the piston is pressed to the liner. The effect is confirmed by friction measurement and oil film observation, using prototype pistons. And also one major factor of the effect is clarified that not only side force but also cylinder pressure causes effective deformation of the skirt to create thick oil film at early combustion stroke.

The ejector is a fluid pump that recovers expansion energy, which is wasted in the conventional refrigeration cycle decompression process, and converts the recovered expansion energy into pressure energy. In the ejector cycle, the ejector helps to reduce power consumption of the compressor by using the above mentioned pressure-rising effect. Consequently, the ejector system can improve energy efficiency of the refrigeration cycle. In previous work, the ejector cycle was used to reduce power consumption in refrigeration cycles for a cool-box (a beverage cooling inside the vehicle) and refrigerated truck box. Both of these applications used the ejector to achieve refrigerant pressure/temperature below the vehicle cabin temperature. Now, the ejector has been integrated into the vehicle cabin evaporator to reduce power consumption of the refrigeration cycle for vehicle cabin cooling.

In recent years, fuel consumption regulations are becoming more severe in every country in the world. Engine size reduction plus turbo is one of the solutions. Our turbo system has an intercooler which cools high temperature gas compressed by a turbocharger. The structure of the intercooler is a tank mounted on both sides of a heat exchanger. The tank connects to the heat exchanger and turbo system allowing EGR (Exhaust Gas Recirculation) gas through the heat exchanger in response to the tightening of exhaust gas regulations. Use of the LPL (Low Pressure Loop) system which refluxes EGR gas is expected to increase from now. Since EGR gas is characterized by high temperature, high pressure, and acidic condensed water, high fatigue strength at high temperature and acid resistivity is required. Therefore aluminum (Al) is generally applied for “intercooler tank” (hereafter referred to as “tank”).

For nearly twenty years, DiMethyl Ether has been known to be an outstanding fuel for combustion in diesel cycle engines. Not only does it have a high Cetane number, it burns absolutely soot free and produces lower NOx exhaust emissions than the equivalent diesel. However, the physical properties of DME such as its low viscosity, lubricity and bulk modulus have negative effects for the fuel injection system, which have both limited the achievable injection pressures to about 500 bar and DME's introduction into the market. To overcome some of these effects, a common rail fuel injection system was adapted to operate with DME and produce injection pressures of up to 1000 bar. To understand the effect of the high injection pressure, tests were carried out using 2D optically accessed nozzles. This allowed the impact of the high vapour pressure of DME on the onset of cavitation in the nozzle hole to be assessed and improve the flow characteristics.

Global warming caused by greenhouse gases are currently a significant problem in the world. Hydrogen is regarded as one of the possible sources of energy for the future. Hydrogen fueled engines emit no carbon dioxide as tank-to-wheel. Hydrogen engines can reduce greenhouse gases in comparison to engines fueled with fossil fuels. A pre-mixed hydrogen-fueled engine, specifically, can be put into practical use in a short period of time from a technical point of view. However, there are some technical issues, such as backfiring and low power output to resolve. With the aim to put a pre-mixed hydrogen-fueled engine for trucks and buses into practical use, it is necessary to prevent backfiring and to develop a high output engine. A diesel engine modified as a pre-mixed hydrogen-fueled engine was equipped with a variable geometry turbo-charger for higher output.

As the demand for improved fuel economy increases and new CO2 regulations have been issued, aerodynamic drag reduction has become more critical. One of the important factors to consider is cooling drag. One way to reduce cooling drag is to decrease the air flow volume through the front grille, but this has an undesirable impact on cooling performance as well as component heat load in the under-hood area. For this reason, cooling drag reduction methods while keeping reliability, cooling performance and component heat management were investigated in this study. At first, air flow volume reduction at high speed was studied, where aerodynamic drag has the greatest influence. For vehicles sold in the USA, cooling specification tends to be determined based on low speed, while towing or driving up mountain roads, and therefore, there may be extra cooling capacity under high speed conditions.

Requirements for fuel economy improvement and reduction in the vehicles engine compartment have increased significantly in the pass years. Performances in radiators have driven changes in terms of compactness and weight reductions. By focusing on the air flow we have optimized the radiator fin and developed a high performance radiator. A similar performance was achieved using an 11mm core depth which has 30% weight reduction compared to a 16mm core depth. The purpose of this paper is to present a technical outline about fin optimization.

This study investigates the reduction of the Blade Passing Frequency (BPF) noise radiated from an automotive engine cooling fans, especially in case of the fan with an eccentric shroud. In recent years, with the increase of HV and EV, noise reduction demand been increased. Therefore it is necessary to reduce engine cooling fan noise. In addition, as a vehicle trend, engine rooms have diminished due to expansion of passenger rooms. As a result, since the space for engine cooling fans need to be small. In this situation, shroud shapes have become complicated and non-axial symmetric (eccentric). Generally, the noise of fan with an eccentric shroud becomes worse especially for BPF noise. So it is necessary to reduce the fan BPF noise. The purposes of this paper is to find sound sources of the BPF noise by measuring sound intensity and to analyze the flow structure around the blade by Computational Fluid Dynamics (CFD).

Improving the engine efficiency to respond to climate change and energy security issues is strongly required. In order to improve the engine efficiency, lower fuel consumption, and enhance engine performance, OEMs have been developing high compression ratio engines and downsized turbocharged engines. However, higher compression ratio and turbocharging cause cylinder pressure to increase, which in turn increases the demand voltage for ignition. To reduce the demand voltage, a new ignition system is developed that uses a high voltage Zener diode to maintain a constant output voltage. Maintaining a constant voltage higher than the static breakdown voltage helps limit the amount of overshoot produced during the spark event. This allows discharge to occur at a lower demand voltage than with conventional spark ignition systems. The results show that the maximum reduction in demand voltage is 3.5 kV when the engine is operated at 2800 rpm and 2.6 MPa break mean effective pressure.

The demand for better driving comfort, fuel efficiency and reduced CO2 output has been becoming increasingly stringent. In response to such needs, we developed Transmission Electro-Hydraulic Control Module (TEHCM). For Automatic Transmission, expanding the lock-up control area is necessary to improve fuel efficiency. Meanwhile, lock-up control at lower speeds aggravates shift quality. To improve shift quality, Automatic Transmission Fluid (ATF) pressure control must be precise is needed. This can be accomplished by compensating for deviation in TEHCM, which integrates Transmission Control Unit (TCU) and the pressure control actuator, Variable Force Solenoid (VFS). However, there are two problems in installing TEHCM in compact vehicle. The first problem is the miniaturization of such TEHCM. Regarding modules that require a high electrical current to operate the VFS, thermal conductivity contradicts miniaturization.