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To increase thermal efficiency of internal combustion engines, dilution combustion systems, such as lean burn and exhaust gas recirculation systems, have been developed. These systems require spark-ignition coils generating large discharge current and discharge energy to achieve stable ignition under diluted mixture conditions. Several studies have clarified that larger discharge current increases spark-channel stretch and decreases the possibility of spark channel blow-off and misfire. However, these investigations do not mention the effect of larger discharge current and energy on the initial combustion period. The purpose of this study was to investigate the relation among dilution ratio, initial-combustion period, and coil specifications to clarify the control factor of the dilution limit.

In recent years, improvement of in-use fuel economy is required with tightening of exhaust emission regulation. We assume that one of the most effective solutions is ACC (Adaptive Cruise Control), which can control a powertrain accurately more than a driver. We have been developing a fuel saving ADAS (Advanced Driver Assistance System) application named “Sailing-ACC”. Sailing-ACC system uses sailing stop technology which stops engine fuel injection, and disengages a clutch coupling a transmission when a vehicle does not need acceleration torque. This system has a potential to greatly improve fuel efficiency. In this paper, we present a predictive powertrain state switching algorithm using external information (route information, preceding vehicle information). This algorithm calculates appropriate switching timing between a sailing stop mode and an acceleration mode to generate a “pulse-and-glide” pattern.

Automotive fuel can be efficiently combusted by injecting it into the cylinders at high pressure to atomize it to pass the regulations for exhaust gas and fuel economy. For this reason, automotive companies have developed direct injection engines, which can inject gasoline into the cylinders directly. Furthermore, the demand for lower-noise high pressure pumps is also increasing from the viewpoint of automotive comfort. Since the valve velocity and noise level will increase as the pressure in fuel pumps increases, noise problems need to be solved under the high pressure conditions. Accordingly, the valve motion should be predicted with high accuracy under operating conditions to evaluate the noise caused by valve impingement. In addition, the squeeze film effect phenomenon will occur in the physical fuel pumps affect the prediction of the noise level caused by valve impingement.

We developed the numerical simulation tool by using OpenFOAM® and in-house simulation codes for Gasoline Direct Injection (GDI) engine in order to carry out the precise investigation of the throughout process from the internal nozzle flow to the fuel/air mixture in engines. For the piston/valve motions, a mapping approach is employed and implemented in this study. In the meantime, the spray atomization including the liquid-columnbreakup region and the secondary-breakup region are simulated by combining the different numerical approaches applied to each region. By connecting the result of liquid-column-breakup simulation to the secondary-breakup simulation, the regions which have different physical phenomena with different length scales are seamlessly jointed; i.e., the velocity and position of droplets predicted by the liquid-column-breakup simulation is used in the secondary breakup simulation so that the initial velocity and position of droplets are transferred.

In previous study, a method of combustion detection for homogeneous charge compression ignition (HCCI) using a crank angle sensor and a knock sensor has been estimated [1]. In addition, an ion-current sensor has been used as a countermeasure against abnormal combustion with downsizing and higher compression ratio engines. An ion-current sensor has been newly adopted in engine systems. In this study, detection performance of combustion conditions in HCCI and spark ignition (SI) using with the ion-current sensor was estimated. The purpose of this study was to confirm detectable combustion conditions using with the ion-current sensor, and to confirm a requirement of applied voltage for the ion-current sensor. A detection signal of the ion-current sensor was changed by combustion style (HCCI,SI). Experimental results showed a heat release rate increased with ion signals increasing approximately at the same time in HCCI and SI.

Recently emissions regulations are being strengthened. An air-fuel ratio cylinder imbalance causes emissions to increase due to universal exhaust gas oxygen (UEGO) sensor error or exhaust gas oxygen (EGO) sensor error. Various methods of reducing an air-fuel ratio cylinder imbalance have been developed. It is preferable for a control system to operate over a wide range of conditions. Our target is to expand the operating conditions from idling to high load conditions. Our approach is to use both an UEGO sensor and a crank angle sensor. A two-revolution frequency component calculated from the UEGO sensor output signal and angular acceleration calculated from the crank angle sensor output signal are used to identify the cylinder where the air-fuel ratio error occurs.

The authors developed a multi-swirl type injector characterized by a short spray penetration length and fine atomization to improve exhaust emissions and fuel consumption for port fuel injection (PFI) gasoline engines. In PFI gasoline engines, fuel adhesion to an intake manifold causes exhaust emission. In addition, good mixing of fuel and air causes high combustion efficiency, and as a result the fuel consumption improves. Injectors therefore require two improvements: first, a short spray penetration to avoid fuel adhesion to the intake manifold, and second, a fine atomization spray to generate a good mixture formation of fuel and air. In this study, the authors developed a multi-swirl type injector equipped with multiple orifice holes featuring swirl chambers upstream of each orifice. The key feature of the proposed injector is “involute curve-formed swirl chambers” for generating a uniform thin liquid-film in the orifices.

The cooled EGR system has been focused on as a method for knocking suppression in gasoline engines. In this paper, the effect of cooled EGR on knocking suppression that leads to lower fuel consumption is investigated in a turbo-charged gasoline engine. First, the cooled EGR effect is estimated by combustion simulation with a knock prediction model. It shows that the ignition timing at the knocking limit can be advanced by about 1 [deg. CA] per 1% of EGR ratio, combustion phasing (50% heat release timing) at the knocking limit can be advanced by about 0.5 [deg. CA] per 1% of EGR ratio, and the fuel consumption amount can be decreased by about 0.4% per 1% of EGR ratio. Second, the effect of cooled EGR is verified in an experimental approach. By adding inert gas (N2/CO2) as simulated EGR gas upstream of the intake pipe, the effect of EGR is investigated when EGR gas and fresh air are mixed homogeneously. As a result, the ignition timing at the knocking limit is advanced by 7 [deg.

The robustness control for homogeneous charge compression ignition (HCCI) using a crank angle sensor and a knock sensor has been estimated. On the other hand, an ion current sensor is used as a countermeasure against abnormal combustion with downsized and higher compression ratio engines. This sensor can generally be adopted in engine systems. Therefore, we examined the application of an ion current sensor to robustness control for HCCI. The purpose of this research was to develop a method of detecting combustion conditions to make HCCI engines more robust. Therefore, we evaluated the performance of the ion current sensor. Experimental results comparing ion intensity detection in HCCI. The detection value of the ion current sensor changed based on the form of combustion. Experimental results showed that the heat release rate increased with an increase in ion signals appear during the same time at approximately in both spark ignition (SI) and HCCI.

The internal combustion engines waste large amounts of heat energy, which account for 60% of the fuel energy. If this heat energy could be converted to the output power of engines, their thermal efficiency could be improved. The thermal efficiency of the Otto cycle increases as the compression ratio and the ratio of specific heat increase. If high octane number fuel is used in engines, their thermal efficiency could be improved. Moreover, thermal efficiency could be improved further if fuel could be combusted in dilute condition. Therefore, exhaust heat recovery, high compression combustion, and lean combustion are important methods of improving the thermal efficiency of SI engines. These three methods could be combined by using hydrous ethanol as fuel. Exhaust heat can be recovered by the steam reforming of hydrous ethanol. The reformed gas including hydrogen can be combusted in dilute condition. In addition, it is cooled by directly injecting hydrous ethanol into the engine.

A new diagnosis method for an air-fuel ratio cylinder imbalance has been developed. The developed diagnosis method is composed of two parts. The first part detects an occurrence of an air-fuel ratio cylinder imbalance by using a two revolution frequency component of an EGO sensor output signal or an UEGO sensor output signal upstream from a catalyst. The two revolution frequency component is from a cycle where an engine rotates twice. The second part of the diagnosis method detects an increase of emissions by using a low frequency component which is calculated from the output of an EGO sensor downstream from the catalyst. When the two revolution frequency component calculated using the upstream sensor output is larger than a certain level and the low frequency component calculated using the downstream sensor output is shifted to a leaner range, the diagnosis judges that the emissions increase is due to an air-fuel ratio cylinder imbalance.

In response to the growing demand for fuel economy, we are developing a high-efficient variable displacement pump for hydraulic power steering systems. In order to develop a quiet variable displacement pump which generates lower noise for better vehicle interior sound quality, we have been developing a simulation tool which includes hydraulic analysis, vibration analysis, and vehicle interior noise analysis which combines simulation outputs and measured noise transfer functions of the targeted vehicle. This paper provides both validation results of the simulation tool and application examples to design improvement to conclude the effectiveness of the simulation tool developed.

Hydrogen produced from regenerative sources has the potential to be a sustainable substitute for fossil fuels. A hydrogen internal combustion engine has good combustion characteristics, such as higher flame propagation velocity, shorter quenching distance, and higher thermal conductivity compared with hydrocarbon fuel. However, storing hydrogen is problematic since the energy density is low. Hydrogen can be chemically stored as a hydrocarbon fuel. In particular, an organic hydride can easily generate hydrogen through use of a catalyst. Additionally, it has an advantage in hydrogen transportation due to its liquid form at room temperature and pressure. We examined the application of an organic hydride in a spark ignition (SI) engine. We used methylcyclohexane (MCH) as an organic hydride from which hydrogen and toluene (TOL) can be reformed. First, the theoretical thermal efficiency was examined when hydrogen and TOL were supplied to an SI engine.

Emission regulations continue to be strengthened, and it is important to decrease cold start hydrocarbon concentrations in order to meet them, now and in the future. The HC concentration in engine exhaust gas is reduced by controlling the air-fuel ratio to the low HC range and retarding the ignition timing as much as possible until the engine stability reaches a certain deterioration level. Conventionally however, the target air-fuel ratio has been set at a richer range than the low HC range and the target ignition timing has been more advanced than the engine stability limit, in order to stabilize the engine for various disturbances. As a result, the HC concentration has not been minimized. To solve this problem, a new engine control has been developed. This control uses a crank angle sensor to simultaneously control the air-fuel ratio and the ignition timing so that the HC concentration can be minimized.

Model-based methodologies for the engine calibration process, employing engine cycle simulation and polynomial regression analysis, have been developed and the reliability of the proposed method was confirmed by validating the model predictions with dynamometer test data. From the results, it was clear that the predictions by the engine cycle simulation with a knock model, which considers the two-stage hydrocarbon ignition characteristics of gasoline, were in good agreement with the dynamometer test data if the model tuning parameters were strictly adjusted. Physical model tuning and validation were done, followed by the creation of a dataset for the regression analysis of charging efficiency, EGR mass, and MBT using a 4th order polynomial equation. The stepwise method was demonstrated to yield a logarithm likelihood ratio and its false probability at each term in the polynomial equation.

A new variable valve event and lift (VVEL) system has been developed by applying a multiple-link mechanism. This VVEL system can continuously vary the valve event angle and lift over a wide range from an exceptional small event angle and small lift and to a large event angle and large lift. This capability offers the potential to improve fuel economy, power output, emissions and other parameters of engine performance. The valve lift characteristics obtained with the VVEL system consist of a synthesis of the oscillatory motion characteristics of the multiple-link mechanism and the oscillating cam profile. With the multiple-link mechanism, the angular velocity of the oscillating cams varies during valve lift, but the valve lift characteristics incorporate both gentle ramp sections and sharp lift sections, the same as a conventional engine.

A new urea-dosing device with an active-ammonia production function was developed. This function is achieved by an electrically heated bypass passage with a hydrolysis catalyst for urea-to-ammonia conversion. The new device also has the function of mixing ammonia and exhaust gas. It is compact and has low-pressure loss by using the vortex occurring at the back of a static vane. We built a trial device for a small diesel engine and obtained steady state and transient data. The heated-bypass concept can be used in the aftertreatment system of passenger cars. Although active-ammonia production consumes electric power, a predictive calculation of power consumption (based on experimental results) shows that the developed bypass heater can suppress the energy consumption enough not to harm the high-energy efficiency of diesel engines.

Emission regulations continue to be strengthened, and it is important to decrease cold start hydrocarbon concentrations in order to meet them, now and in the future. The HC concentration in engine exhaust gas can be reduced by optimizing the air-fuel ratio. However, a conventional air-fuel ratio feedback control does not operate for the first ten seconds after the engine has started because the air-fuel ratio sensor has not yet been activated. In this paper, we report on a study to optimize the air-fuel ratio using a crank angle sensor until the air-fuel ratio sensor has been activated. A difference in fuel properties was used as a typical disturbance factor. The control was applied to both a direct-injection engine (DI) and a port-injection engine (MPI). It was evaluated for two fuel types: one which evaporates easily and one which does not. The experimental results show the air-fuel ratio is optimized for both types of fuel.

A continuously variable valve event and lift (VEL) system, actuated by oscillating cams, can provide optimum lift and event angles matching the engine operating conditions, thereby improving fuel economy, exhaust emission performance and power output. The VEL system allows small lift and event angles even in the engine operating region where the required intake air volume is small and the influence of valvetrain friction is substantial, such as during idling. Therefore, the system can reduce friction to lower levels than conventional valvetrains, which works to improve fuel economy. On the other hand, a distinct feature of oscillating cams is that their sliding velocity is zero at the time of peak lift, which differs from the behavior of conventional rotating cams. For that reason, it is assumed that the friction and lubrication characteristics of oscillating cams may differ from those of conventional cams.

Time-resolved continuous images of wrinkling flame front cross-sections were acquired by a laser-light sheet technique in an optically accessible spark ignition engine. The test engine was operated at various engine speeds and compression ratios. The fractal dimension of the curve, D2, was measured in a time series for each cycle. Analysis of the data shows that as the flame propagates the fractal dimension, D2, is close to unity a short time after spark ignition and then increases. Examination of the relationship between the growth rate of the fractal dimension, ΔD2/Δt, and D2 reveals that the higher D2 is, the lower ΔD2/Δt becomes. An Empirical equation for ΔD2/Δt was derived as a function of the ratio of the turbulence intensity to the laminar burning velocity and pressure. This model was tested in an SI engine combustion simulation, and results compared favorably with experimental data.