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In this study, the authors analyze the concentration distribution of an evaporative spray mixture with LIEF (Laser induced exciplex fluorescence) method, which is a type of optical measurement. LIEF method is one of the optical measurements for obtaining the spray concentration distribution for separating vapor/liquid phases based on the fluorescence characteristics. In this paper, a quantitative concentration distribution analysis method for wall impingement spray in heterogeneous temperature field has been proposed. Then, a series of experiments were performed in varying injection pressure and ambient density. As a result, a two-dimensional concentration distribution was obtained for the free spray and wall impingement spray.

Electric vehicles have become more widespread globally, with the aim of realizing a carbon-neutral society. In addition, the various policies for vehicle engines have become increasingly strict. It is desirable to evaluate fuel consumption and exhaust emissions using real vehicles on actual roads, with the goal of improving air quality. Hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) have a high frequency of engine stops during driving. In a real driving emission (RDE) test, a portable emission measurement system (PEMS) is used, which continues to measure emissions even when the engine stops; this can decrease the emission concentration inside the tailpipe and result in an inaccurate emission measurement. Furthermore, RDE tests are affected by the installation performance of the PEMS; the emission intake is often installed by extending the exhaust outlet.

To reduce carbon dioxide emissions, the use of vehicles operating on electrification technology, such as plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs) is rapidly increasing. A similar trend also exists in the field of heavy-duty vehicles, such as trucks and buses. When evaluating—via the certification test method—the fuel efficiency, electricity efficiency, and exhaust gas emission of heavy-duty vehicles that have many batteries, the powertrain, including the batteries, is modeled and investigated. However, such modeling is difficult because batteries deteriorate, and the ambient temperature fluctuates during vehicle operation. To resolve this issue, we developed a new evaluation method that enables real-time cooperative control of actual batteries and hardware-in-the-loop simulation (HILS).

Fuel consumption and exhaust gas emission regulations are being tightened around the world year by year. Electric vehicles are needed to reduce carbon dioxide emissions. Especially, Plug-in hybrid heavy-duty vehicles (PHEVs) are expected to become widespread. PHEVs enable all-electric modes, as well as hybrid modes, using both engines and electric motors, but the control system significantly affects the characteristics of fuel consumption and gas emission. In this study, we used new testing machine (we call extended HILS) to analyze the fuel consumption and gas emission for different plug-in hybrid control systems and investigated the optimal control method for PHEVs.

In previous study, the model for flash-boiling spray of multicomponent fuel was constructed and was implemented into KIVA code. This model considered the detailed physical properties and evaporation process of multicomponent fuel and the bubble nucleation, growth and disruption in a nozzle orifice and injected fuel droplets. These numerical results using this model were compared with experimental data which were obtained in the previous study using a constant volume vessel. The spray characteristics from numerical simulation qualitatively showed good agreement with the experimental results. Especially, it was confirmed from both the numerical and experimental data that flash-boiling effectively accelerated the atomization and vaporization of fuel droplets. However, in this previous study, injection pressure was very low (up to 15 MPa), and the spray characteristics of high pressure injection could not be analyzed.

Fuel consumption rate (fuel economy) and exhaust gas emission regulations are being tightened around the world year by year. In Europe, the real driving emission (RDE) method for evaluating exhaust gas emitted from road-going vehicles was introduced after September 2017 for new types of light/medium-duty vehicles, in addition to the chassis dynamometer test using the worldwide harmonized light vehicles test procedure (WLTP). Further, the worldwide harmonized heavy-duty certification (WHDC) method was introduced after 2016 as an exhaust gas emission test method for heavy-duty vehicles. In each evaluation, the tests of vehicles and engines are initiated from cold states. Heavy-duty hybrid vehicles are evaluated using the vehicle simulation method. For example, the power characteristics of a engine model is obtained during engine warm operation. Therefore, various performances during cold start cannot be precisely evaluated by using simulator.

Around the world, fuel economy and emission regulations for vehicles have become increasingly stringent year by year. In Europe, the real driving emission (RDE) testing was introduced for evaluating the emission at driving the road-going vehicles after September 2017. In order to effiency produce the actual vehicles, Each automobile manufacturer introduce the “Hardware In the Loop Simulator” (HILS) and “Engine In the Loop Simulator” (which is called the EILS or the extended HILS [1, 2]), which is combined with HILS and an actual engine. However, if the driver model used in the vehicle simulation (HILS, extended HILS) does not correctly simulate actual human driving behaviors, the model vehicle performances will differ from the actual vehicle performance. The fuel economy and emission characteristics are affected by the differences of the driver model control logic during the execution of vehicle simulation.

Next-generation vehicles which include the Electric Vehicles, the Hybrid Electric Vehicles and the Plug-in Hybrid Electric Vehicles are researched and expected to reduce carbon dioxide (CO2) emission in the future. In order to reduce the emissions of the heavy-duty diesel plug-in hybrid electric vehicles (PHEV), it is necessary to provide the high exhaust-gas temperature and to keep the exhaust-gas aftertreatment system effective. The engine starting condition of the PHEV is cold, and the engine start and stop is repeated. And, the engine load of the PHEV is assisted by the electric motor. Therefore, the exhaust-gas aftertreatment system of the PHEV is not able to get the enough high exhaust-gas temperature. And, the warm-up of the exhaust-gas aftertreatment system for the PHEV is spent the long time. So, it is worried about a bad effect on the emission characteristics of the PHEV.

In order to improve the fuel economy of the heavy duty trucks at a highway driving condition, the heavy duty hybrid trucks with new type of hybrid electric assist engine system were proposed at the previous report. The new system consists of a downsizing diesel engine with a two-stage charging structure, which has an electric supercharger with bypass circuit and a conventional turbocharger, the hybrid electric motor and the small-capacity battery. The electric power consumption of an electric supercharger is equivalent to the amount of the regeneration power produced during high-speed driving where the opportunity of the regeneration is small. In this report, an electric supercharger for the heavy duty hybrid truck was produced experimentally. First, the engine performance and exhaust emissions were investigated using the 4 cylinder diesel engine equipped with an electric supercharger.

Next-generation vehicles which include Electric Vehicles and Hybrid Electric Vehicles are studied and expected to reduce carbon dioxide emissions. The number of small delivery hybrid trucks has increased in the commercial vehicle class. The engine load of a commercial hybrid truck is reduced by using an electric motor. Fuel economy of the hybrid truck is improved with the assist. On the other hand, exhaust-gas temperature is decreased, and it has a negative effect on the purification performance of aftertreatment system. In this report, the fuel performance and emission gas characteristics of marketed small hybrid trucks were surveyed using the chassis dynamometer test system.

The atomization structure of the fuel spray is known to be affected by flow conditions and cavitation inside the nozzle hole. In this paper, the cavitation phenomena inside the nozzle hole was visualized by using large-scale transparent nozzles, as well as the effect of length-to-width ratio (l/w ratio) of the nozzle hole on cavitation and on the behavior of injection liquid jet. In addition, various flow patterns inside the nozzle hole same as experimental conditions were simulated by the use of Cavitation model incorporated in Star-CCM+, which was compared with experimental results.

Next-generation vehicles which include Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) are researched and expected to reduce carbon dioxide (CO2) emissions in the future. In the national new-car sales in 2012 of Japan, the total sales of hybrid vehicles kept 26.5% share. In the field of passenger cars, this share was 29.7%. And, this share rose about four times compared to that of 2008 [1]. Also, small delivery hybrid trucks are increased in the commercial vehicle class. Fuel economy of hybrid trucks in the catalog specifications is relatively better than that of the diesel tracks which have no hybrid systems. Nevertheless, hybrid trucks' users report that advantages of fuel economy of hybrid trucks at the real traffic driving conditions are small.

Next-generation vehicles which include Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) are researched and expected to reduce CO2 emissions in the future. Generally, the main factor to support high efficiency of EV and HEV is the idle stop, motor assistance and regenerative braking. The vehicle mechanism of HEV is complex, compared with conventional internal combustion engine vehicle. Certification test method of gas emissions and fuel consumption is used driving mode, which is currently reflecting the typical driving conditions in the market. And driving mode of certification test is established focusing on the reproducibility of driving by conventional internal combustion engine vehicles. It is necessary to consider that the driving mode for the vehicle used regenerative energy is reflected correctly. And high accuracy certification test method for next generation HEVs is necessary in order to evaluate exhaust gas and fuel economy.

At interurban transportation, improvement of fuel economy of hybrid electric heavy-duty diesel vehicles, which assist drive-axle by using regeneration energy, is minimum, compared to heavy-duty diesel vehicles. One of the factors is that hybrid electric heavy-duty vehicles are not able to balance regeneration energy (input) and power energy (output) at high speed driving. One reason is not opportunity to operate of braking at high speed driving for the heavy-duty vehicle. In this research, we focus on the method used for the battery energy, and propose a new concept of hybrid electric system to efficiently utilize battery energy. That system consists of electrical booster for supercharging intake air into engine cylinder. We have confirmed the feasibility of the electric system of a new HEV concept by using the simulation I created.

In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.

Three-dimensional large eddy simulation (LES) has been conducted for a diesel spray flame using KIVALES which is LES version of KIVA code. Modified TAB model, velocity interpolation model and rigid sphere model are used to improve the prediction of the fuel-mixture process in the diesel spray. Combustion is simulated using the Eddy-Dissipation model. CIP method was incorporated into the KIVALES in order to suppress the numerical instability on the combustible flow. The formation of soot and NO was simulated using Hiroyasu model and KIVA original model. Three different grid resolutions were used to examine the grid dependency. The result shows that the LES approach with 0.5 mm grid size is able to resolve the instantaneous spray with the intermittency in the spray periphery, the axi-symmetric shape and meandering flow after the end of injection as shown in the experimental results.

The authors have explored the potential of fuel to control spray and its combustion processes in a diesel engine. Fuel has some potential for low emission and high thermal efficiency because its volatility and ignitability are one of the ultimate performing factors of the engines. In present study, the ignition process of mixed fuel spray was investigated in a constant volume combustion vessel and in a rapid compression and expansion machine, The ignition delay based on the diagram of rate of the heat release, the imaging of natural flame emissions and the numerical simulation were carried out to clarify the effect of the physical and chemical properties of mixed fuel on ignition characteristics.

Large Eddy Simulation (LES) is applied to non-evaporative and evaporative diesel spray simulations. KIVALES, which is LES version of KIVA code, is used as the LES computational code. Modified TAB model is used as breakup model, and interpolated donor cell differencing scheme is employed to calculate convective terms. To validity LES simulation, LES results using KIVALES are compared with experimental results and simulated results with conventional RANS approach using KIVA3V res.2. The results show that the LES simulation of non-evaporative spray depends on the grid size in comparison with RANS simulation, and good agreement is obtained between experimental results and the LES results with fine grid (720,000 cells). Furthermore, asymmetric non-evaporative spray which has intermittency at the outer edge of sprays is simulated, since instantaneous turbulent flow field can be predicted directly in LES case.

The Flame structure and combustion characteristics for two waste-cooking oils were investigated in detail. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is the fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. In the experiments, the used fuels were gas oil, i-BDF, B100 and B20. Spray characteristics and basic combustion properties were measured inside a rapid compression and an expansion machine (RCEM).

The maximum liquid-phase penetration and vaporization behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters (injection pressure, ambient gas condition and fuel temperature) and fuel properties on vaporization behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector.