Search Results

This study investigates if particulates from a GDI engine can be significantly suppressed by use of ultra-high injection pressures under 2 different engine conditions known to be associated with high particulate numbers (PN): warm-up and transients. Experiments were carried out in a single-cylinder GDI engine equipped with an endoscope connected to a high-speed camera to enable combustion visualization. To mimic the warming-up, the coolant temperature was varied between 20 °C and 90 °C. A Diesel injector with modified nozzle was used and the injection pressures were varied between 400 and 1500 bar. The results revealed that increasing the fuel injection pressure decreased engine out HC and PN under warming-up conditions. However, the coolant water temperature was the most dominant factor affecting the emissions. For coolant temperature of 20 °C, the use of 1500 bar fuel injection pressure in comparison to lower fuel pressures resulted in significantly lower PN.

Global exhaust emission regulations are becoming stricter, and vehicles equipped with the idle stop system (ISS) are increasing. Recently, starters for vehicles equipped with ISS are required to improve operation feel when speedily restarted. To satisfy this demand, starters must rotate at higher rotational speeds, and heavier wear in their brushes may cause problems. Tribofilm formed on commutators surface by the brush sliding is an important factor in the brush commutator wear, because tribofilm is said to have a property to increase lubricity and decrease mechanical wear in brushes and commutator, as well as to improve commutation and decrease arc wear. Therefore, for reducing brush commutator wear, it is considered effective to promote film formation by improving materials. However, few researches have been conducted to evaluate the relationship between brush materials and tribofilm formation.

With the global adoption of diesel common rail systems and the wide variation in composition of local commercial fuels, modern fuel injection systems must be robust against diverse fuel properties. To bridge the knowledge gap on the effects of compositional variation for real commercial fuels on spray combustion characteristics, the present work quantifies ignition and soot formation/oxidation in three unique, international diesel blends. Schlieren imaging, excited-state hydroxyl radical (OH*) chemiluminescence imaging and diffused back-illumination extinction imaging were employed to quantify vapor penetration, ignition, and soot formation and oxidation for high-pressure sprays in a constant-volume, pre-burn chamber. The three fuels were procured from Finland, Japan and Brazil and have cetane numbers of 64.1, 56.1 and 45.4, respectively.

Continuous improvement of gasoline engine emissions performance is required to further protect the global environment and also the impact of emissions on a local level. During real world driving, transient engine operation and variation in fuel injection, airflow, and wall temperature are key factors to be controlled. Due to the limited opportunity for optimization of engine control, generation of a well-mixed fuel spray is necessary to create a suitable combustion environment to minimize emissions. Optimum spray performance achieves minimum surface wetting as well as promoting evaporation and diffusion if wetting occurs. Improvement in spray homogeneity is an important step to achieve this. Higher fuel pressure is initially considered to achieve improvements, as it is expected to improve mixture formation by reduction of wall wetting due to high atomization and lower penetration, as well as improvement in spray homogeneity.

This paper presents an improvement in the accuracy of NOx sensors at high NOx concentration regions by optimizing the manufacturing process, sensor electrode materials and structure, in order to suppress the deterioration mechanism of sensor electrodes. Though NOx sensors generally consist of Pt/Au alloy based oxygen pump electrodes and Pt/Rh alloy based sensor electrodes, detailed experimental analysis of aged NOx sensors showed changes in the surface composition and morphology of the sensor electrode. The surface of the sensor electrode was covered with Au, which is not originally contained in the electrode, resulting in a diminished active site for NOx detection on the sensor electrode and a decrease in sensor output. Theoretical analysis using CAE with molecular dynamics supported that Au tends to be concentrated on the surface of the sensor electrode.

According to the advance of engine control development, demands for direct sensing of physical quantity have been growing. Regarding pressure sensing, key properties for direct sensing are robustness against high temperature and pressure, and response time in addition to accuracy. In this work, a pressure sensor module with these key properties was developed. First of all, a piezoelectric device was selected as a suitable sensing principle for the required properties because of its thermally stable piezoelectric effect and potential for simple installation structure. Regarding robustness against temperature, the sensor module was designed to form thermal isolation layer with outer housing which is optimized according to its application. Regarding robustness against pressure and response time, breakage of the piezoelectric element is the main technical issue.

To comply with increasing fuel efficiency regulations, a low temperature radiator (LT radiator) is required to cool the charge-air system of a turbocharged engine. These engines are important to use for environmentally-friendly cars. Since heavy-duty and high-performance cars demand high cooling performance, the main radiator alone is typically insufficient in meeting the vehicle’s cooling requirements. An additional radiator installed in the front of the wheel-well is required to meet the extra cooling demand. In order to install this radiator in the front of the wheel-well, guaranteed performance in the limited packaging space and impact resistance of the leading tube edge are required. We developed the Supplementary Inner-Fin Radiator (SIR) which achieves the compact, high-performance, and durability requirements by use of an inner-fin tube (I/F tube). The purpose of this paper is to report our design approach and product specifications of the SIR.

For the purpose of coping with the strengthening of NOx exhaust gas control and fuel consumption control, it is indispensable to improve the NOx purification capacity. In view of this, vehicle manufacturers are in the course of developing high performance SCR (Selective Catalytic Reduction) systems [1, 2]. For such SCR systems to be realized, high precision NOx sensors for carrying out urea injection quantity control and SCR degradation diagnosis are absolutely indispensable. Detection of NOx concentration by means of a NOx sensor is generally performed as follows: O2 is discharged by means of an O2 detection electrode; remaining NOx is decomposed by a NOx detection electrode; NOx concentration is then detected as electric current that flows when oxygen ions are conduct through solid electrolyte. In order to detect NOx of ppm-order, it is necessary to detect minute current of nA-order with high accuracy.

As vehicle emission regulations become increasingly rigorous, the automotive industry is accelerating the development of electrified vehicle platforms such as Battery Electric Vehicles (BEV) and Plug-in Hybrid Electric Vehicles (PHEV). Since the available waste heat from these vehicles is limited, additional heat sources such as electric heaters are needed for cabin heating operation. The use of a heat pump system is one of the solutions to improve EV driving range at cold ambient conditions. In this study, an efficient gas-injection heat pump system has been developed, which achieves high cabin heating performance at low ambient temperature and dehumidification operation without the assistance of electric heaters in ’17 model year Prius Prime.

The coming Diesel powertrains will remain as key technology in Europe to achieve the stringent 2025 CO2 emission targets. Especially for applications which are unlikely to be powered by pure EV technology like Light Duty vehicles and C/D segment vehicles which require a long driving range this is the case. To cope with these low CO2 targets the amount of electrification e.g. in form of 48V Belt-driven integrated Starter Generator (BSG) systems will increase. On the other hand the efficiency of the Diesel engine will increase which will result in lower exhaust gas temperatures resulting in a challenge to keep the required NOx reduction system efficiencies under Real Drive Emissions (RDE) driving conditions. In order to comply with the RDE legislation down to -7 °C ambient an efficient thermal management is one potential approach. Commonly utilized means to increase exhaust gas temperature are late injection and/or intake throttling, which enable sufficient NOx reduction efficiency.

In respect to the present large refrigerator trucks, sub-engine type is the main product, but the basic structure does not change greatly since the introduction for around 50 years. A sub-engine type uses an industrial engine to drive the compressor, and the environmental correspondence such as the fuel consumption, the emission is late remarkably. In addition, most of trucks carry the truck equipment including the refrigerator which consumes fuel about 20% of whole vehicle. Focusing on this point, the following are the reports about the system development plan for fuel consumption reduction of the large size refrigerator truck. New concept is to utilize electrical power from HV system to power the electric-driven refrigerator. We have developed a fully electric-driven refrigerator system, which uses regenerated energy that is dedicated for our refrigerator system.

In general, CFD analysis with porous media is precise enough to simulate airflow behavior in a heat exchanger core, placed in the vehicle. In a case when the airflow behavior is complex, however, the precision lowers according to our study. Therefore, we developed a new modeling method to keep high-precision and applied it to analysis of airflow in the vehicle. The concept is at first that the shape of tubes and the distance between the tubes are as the actual product so that the airflow with an oblique angle is to pass through a core. With this concept, airflow with an oblique angle hits the surface of tubes and passes through a core with changing the direction. Next, the concept is to reproduce the air pressure loss in actually-shaped fins, and therefore, we use a porous medium for the modeling of the fins instead of the product shape modeling to combine with the the tubes.

A methodology for simulating effect of international variations in fuel compositions on spray combustion is proposed. The methodology is validated with spray combustion experiments with real fuels from three different countries. The compositions of those fuels were analyzed through GC×GC and H-NMR. It was found that ignition delay times, flame region and flame luminosity were significantly affected by the compositional variations. For the simulation, an evaporation surrogate consisting of twenty two species, covering basic molecular types and a wide range of carbon numbers, is developed. Each species in the evaporation surrogate is then virtually converted to a reaction surrogate consisting of n-hexadecane, methylcyclohexane and 1,2,4-trimethyl benzene so that combustion reactions can be calculated with a published kinetic model. The virtual species conversion (VSC) is made so as to take over combustion-related properties of each species of evaporation surrogates.

Tightening global emissions standards are driving automotive Original Equipment Manufacturer’s (OEM’s) to utilize Three Way Catalyst (TWC) aftertreatment systems that can perform with greater efficiency and greater measured control of Precious Group Metals (PGM) use. At the same time, TWC aftertreatment systems minimize exhaust system pressure drops. This study will determine the influence of catalyst substrate cell geometry on emission and PGM usage. Additionally, a study of lightoff and backpressure comparisons will be conducted. The two substrate configurations used are hex/750cpsi and square/750cpsi.

In order to comply with emission regulation, reach their profitability targets and minimise the in-use cost of their vehicles, OEMs are seeking solutions to optimise their aftertreatment systems. For Selective Catalytic Reduction (SCR) system engineers, one of the most important challenges is to reduce the system's cost, while keeping its high level of NOx emission reduction performance. Ways to achieve this cost reduction include 1. using an engine out NOx estimation model instead of a NOx sensor upstream of the SDPF (DPF coated with SCR) catalyst and 2. eliminating the Ammonia Slip Catalyst (ASC) downstream of the SDPF catalyst. Achieving these challenging targets requires actions on the complete SCR system, from the optimisation of mixing and uniformity in the SDPF catalyst to the development of robust controls. To face these challenges, a novel exhaust reverse flow concept with a blade mixer was developed.

New 2A/F systems different from usual A/F-O2 systems are being developed to cope with strict regulation of exhaust gas. In the 2A/F systems, 2A/F sensors are equipped in front and rear of a three-way catalyst. The A/F-O2 systems are ideas which use a rear O2 to detect exhaust gas leaked from three-way catalyst early and feed back. On the other hand, the 2A/F systems are ideas which use a rear A/F sensor to detect nearly stoichiometric gas discharged from the three-way catalyst accurately, and to prevent leakage of exhaust gas from the three-way catalyst. Therefore, accurate detection of nearly stoichiometric gas by the rear A/F sensor is the most importrant for the 2A/F systems. In general, the A/F sensors can be classified into two types, so called, one-cell type and two-cell type. Because the one-cell type A/F sensors don’t have hysteresis, they have potential for higher accuracy.

For the purpose of improving vehicle fuel efficiency, it is necessary to reduce energy loss in the alternator. We have lowered the resistance of the rectifying device and connecting components, and control the rectifying device with an IC to reduce rectification loss. For the package design, we have changed the structure of the part on which the rectifying device is mounted into a high heat dissipation type. The new structure has enabled optimizing the size of the rectifying device, resulting in the reduction of size of the package. In addition, the rectifying device is mounted using a new soldering material and a new process, which has improved the reliability of the connection. Moreover, since the alternator has introduced a new system, the controller IC has a function for preventing malfunction of the rectifying device and a function for detecting abnormalities, in order to ensure safety.

Alternator, which supplies electric energy to a battery and electrical loads when it is rotated by engine via belt, is one of key components to improve vehicle fuel efficiency. We have reduced rectification loss from AC to DC with a MOSFET instead of a rectifier diode. It is important to turn on the MOSFET and off during a rectification period, called synchronous control, to avoid a current flow in the reverse direction from the battery. We turn it off so as to remain a certain conduction period through a body diode of the MOSFET before the rectification end. It is controlled by making a feedback process to coincide with an internal target conduction period based on the rotational speed of the alternator. We reduced a voltage surge risk at turn-off by changing the feedback gain depending on the sign of the time difference between the measured period and the target.

Exhaust Gas Recirculation (EGR) systems reduce exhaust emissions and improve fuel efficiency. Recently, the number of EGR system installed vehicles has been increasing, especially for gasoline engine systems. One of the major causes of decreasing EGR function is deposit accumulation on a gas passage. The deposit consists mainly of hydrocarbons which are degradation products of fuel, thus the amount of deposit seems to be strongly affected by fuel compositions. Unfortunately there are not as many studies on EGR deposits with gasoline fuel as there are with diesel fuel. In this study, the influence of gasoline fuel compositions, especially aromatics which are major components of EGR gas, on chemical structures of the deposit were investigated. To clarify the accumulation mechanism of EGR deposits, a thermal oxidative degradation test with an autoclave unit and an actual gasoline engine test were employed.

In recent years, from a viewpoint of global warming and energy issues, the need to improve vehicle fuel economy to reduce CO2 emission has become apparent. One of the ways to improve this is to enhance engine thermal efficiency, and for that, automakers have been developing the technologies of high compression ratio and dilute combustion such as exhaust gas recirculation (EGR), and lean combustion. Since excessive dilute combustion causes the failure of flame propagation, combustion promotion by intensifying in-cylinder turbulence has been indispensable. However, instability of flame kernel formation by gas flow fluctuation between combustion cycles is becoming an issue. Therefore, achieving stable flame kernel formation and propagation under a high dilute condition is important technology.