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Currently, two consolidated aftertreatment technologies are available for the reduction of NOx emissions from diesel engines: Urea SCR (Selective Catalytic Reduction) systems and LNT (Lean NOx Trap) systems. Urea SCR technology, which has been widely used for many years at stationary sources, is becoming nowadays an attractive alternative also for light-duty diesel applications. However, SCR systems are much more effective in NOx reduction efficiency at high load operating conditions than light load condition, characterized by lower exhaust gas temperatures.

Using a 109.2 cm3, four-stroke, single-cylinder, two-valve gasoline engine, improvement of fuel economy by extension of lean burn range has been attempted with invented way to intensify tumble flow from a simple mechanical arrangement. With a part of the intake valve was jutted out beyond the perimeter of the cylinder bore, the masking effects from the valve recess on top of the cylinder sleeve created a strong tumble flow, which enabled lean burn at an air fuel ratio leaner than the conventional design by two points. The motorcycle equipped with this engine attained better fuel economy by 5.7% to the base model when measured in Indian Driving Cycle (IDC). The outward-laid intake valve also increased the clearance from the exhaust valve, which enabled use of a large-diameter intake valve to minimize the reduction of maximum power.

Research has been conducted on Controlled Auto-Ignition (CAI) engine with natural gas. CAI engine has the potential to be highly efficient and to produce low emissions. CAI engine is potentially applicable to automobile engine. However due to narrow operating range, CAI engine for automobile engine which require various speed and load in real world operation is still remaining at research level. In comparison some natural gas engines for electricity generation only require continuous operation at constant load. There is possibility of efficiency enhancement by CAI combustion which is running same speed at constant load. Since natural gas is primary consisting of methane (CH4), high auto-ignition temperature is required to occur stable auto-ignition. Usually additional intake heat required to keep stable auto-ignition. To keep high compression temperature, single cylinder natural gas engine with high compression ratio (CR=26) was constructed.

HCCI combustion can realize low NOx and particulate emissions and high thermal efficiency. Therefore, HCCI combustion has a possibility of many kinds of applications, such as an automotive powertrain, general-purpose engine, motorcycle engine and electric generator. However, the operational range using HCCI combustion in terms of speed and load is restricted because the onset of ignition and the heat release rate cannot be controlled directly. For the extension of the operational range using either an external supercharger or a turbocharger is promising. The objective of this research is to investigate the effect of the intake pressure on the HCCI high load limit and HCCI combustion characteristics with blowdown supercharging (BDSC) system. The intake pressure (Pin) and temperature (Tin) were varied as experimental parameters. The intake pressure was swept from 100 kPa (naturally aspirated) to 200 kPa using an external mechanical supercharger.

A simple method is frequently used to calculate a reciprocating engine’s bearing load from the measured cylinder pressure. However, it has become apparent that engine downsizing and weight reduction cannot be achieved easily if an engine is designed based on the simple method. Because of this, an actual load on a bearing was measured, and the measured load values were compared with a bearing load distribution calculated from cylinder pressure. As a result, it was found that some of actual loads were about half of the calculated ones at certain crank angles. The connecting rod’s elastic deformation was focused on as a factor behind such differences, and the rod’s deformation due to the engine’s explosion load was studied. As a result, it was found that the rod part of the engine’s connecting rod was bent by 0.2 mm and became doglegged. Additional investigation regarding these findings would allow further engine downsizing.

The reduction of cycle-to-cycle variations (CCV) is a prerequisite for the development and control of spark-ignition engines with increased efficiency and reduced engine-out emissions. To this end, Large-Eddy Simulations (LES) can improve the understanding of stochastic in-cylinder phenomena during the engine design process, if the employed modeling approach is sufficiently accurate. In this work, an inhouse code has been used to investigate CCV in a direct-injected spark ignition (DISI) engine under fuel-lean conditions with respect to a stoichiometric baseline operating point. It is shown that the crank angle when a characteristic fuel mass fraction is burned, e.g. MFB50, correlates with the equivalence ratio computed as a local average in the vicinity of the spark plug. The lean operating point exhibits significant CCV, which are shown to be correlated also with the in-cylinder subfilter-scale (SFS) kinetic energy.

Recently, emission regulations have been strict in many countries, and it is very difficult technical issue to reduce emissions of diesel cars. In order to reduce the emissions, various combustion technologies such as Massive EGR, PCCI, Rich combustion, etc. have been researched. The combustion technologies require precise control of the states of in-cylinder gas (air mass flow, EGR rate etc.). However, a conventional controller such as PID controller could not provide sufficient control accuracy of the states of in-cylinder gas because the air-pass system controlled by an EGR valve, a throttle valve, a variable nozzle turbo, etc. is a multi-input, multi-output (MIMO) coupled system. Model predictive control (MPC) is well known as the advanced MIMO control method for industrial process. Generally, the sampling period of industrial process is rather long so there is enough time to carry out the optimization calculation for MPC.

The chief goal of engineers studying internal combustion engines is to improve energy efficiency in the face of the increasingly severe global warming and energy issues. Hence, there have been numerous studies focusing on the combustion reactions in order to develop clean and reliable combustion that is capable of operating using less fuel. And to improve the comprehension of engine performance and its combustion reactions, development of comprehensive measurement technique for engine performance, in-cylinder visualization technique, and numerical simulations, is essential and strongly demanded. There have hitherto been numerous studies about combustion diagnostics and analysis, including high-efficiency measurement techniques using response surface method the air-fuel mixture distribution and flame propagation measurement with optical visualization techniques, and numerical calculations of combustion reaction with elementary reactions.

The performance of Gasoline Direct Injection (GDI) engines is governed by multiple physical processes such as the internal nozzle flow and the mixing of the liquid stream with the gaseous ambient environment. A detailed knowledge of these processes even for complex injectors is very important for improving the design and performance of combustion engines all the way to pollutant formation and emissions. However, many processes are still not completely understood, which is partly caused by their restricted experimental accessibility. Thus, high-fidelity simulations can be helpful to obtain further understanding of GDI injectors. In this work, advanced simulation and experimental methods are combined in order to study the spray characteristics of two different 3-hole GDI injectors.

The field of diesel combustion research is producing numerous reports on studies of premixed combustion, which promises simultaneous reduction of both NOx and soot, in order to meet increasingly stringent regulations on harmful emissions from automobiles. However, although premixed combustion can simultaneously reduce both NOx and soot, certain issues have been pointed out, including the fact that it emits greater quantities of unburned HC and CO gases and the fact that it limits the operating range. Furthermore, this combustion method sets the ignition delay longer with the aim of promoting the mixing of fuel and air. This raises issues with the product due to the combustion instability and sensitivity to the uneven fuel properties that are found on the market, the capability of the engine response under transient conditions, the deterioration in combustion noise, and so on.

Honda diesel engine vehicles that go on the market in 2018 will be equipped with a newly developed silver (Ag)-type catalyzed diesel particulate filter (cDPF). Ag has high particulate matter (PM) oxidation performance, but conventional catalyst-carrying methods cause weak contact property between PM and Ag; therefore, the newly Ag-type cDPF was developed on the concept of enhancing the property of contact between PM and the catalyst to realize contact property enhancement at the macro, meso, and nano scales. As a result, the newly developed catalyst showed an enhancement of T90 performance by a factor of approximately 2 relative to the conventional Ag-type catalyst in fresh condition. Durability in the environment of an automobile in use was examined through hydrothermal aging, lean-rich (L/R) aging, sulfur (S) poisoning, and ash deposition. The results have confirmed that hydrothermal aging is the greatest factor in deterioration.

A new concept for trapping NOx and HC during cold start, the NOx Trap Three-Way Catalyst (N-TWC), is proposed. N-TWC adsorbs NOx at room temperature, and upon reaching activation temperature under suitable air-fuel ratio conditions, it reduces the adsorbed NOx. This allows a reduction in NOx emissions during cold start. N-TWC's reduction mechanism relies on NOx adsorption sites which are shown to be highly dispersed palladium on acid sites in the zeolite. Testing on an actual vehicle equipped with N-TWC confirmed that N-TWC is able to reduce emissions of NOx and HC during cold start, which is a challenge for conventional TWCs.

A technique was created to separate the contributions of combustion noise and mechanical noise to engine noise in the time domain in order to achieve efficient measures for enhancing the sound quality of combustion noise. There is an existing technique based on 1/3 octave band analysis that is known as a method for separating the contributions to engine radiation noise, but this technique cannot provide time-domain data. Therefore, the author has proposed a technique that separates engine radiation noise into combustion noise and mechanical noise in the time domain by finding the combustion noise for each cylinder and calculating its structural response function by considering its real and imaginary components. Results of analysis of actual engine radiation noise with this technique confirmed that combustion noise, which is characterized by strong pulsation, and irregular mechanical noise can be separated in the time domain with good precision.

Bio-ethanol is one of the candidates for automotive alternative fuels. For reduction of carbon dioxide emissions, it is important to investigate its optimum combustion procedure. This study has explored effect of ethanol fuels on HCCI-SI hybrid combustion using dual fuel injection (DFI). Steady and transient characteristics of the HCCI-SI hybrid combustion were evaluated using a single cylinder engine and a four-cylinder engine equipped with two port injectors and a direct injector. The experimental results indicated that DFI has the potential for optimizing ignition timing of HCCI combustion and for suppressing knock in SI combustion under fixed compression ratio. The HCCI-SI hybrid combustion using DFI achieved increasing efficiency compared to conventional SI combustion.

In PCCI diesel engine, the fuel is injected much earlier than the injection timing of conventional diesel engines. Exhaust-emission improvements are attained by the lean-premixed combustion. It is expected that fuel properties influence mixture formation and combustion characteristics. In this research, experiments were carried out using a single-cylinder PCCI diesel engine operating on pure fuels with different volatilities. The injection timing and overall equivalence ratio of the premixed spray were varied. The results showed that the maximum heat release rate was smaller for lower-volatility fuel while ISFC was maintained smaller. So the combustion of a lower-volatility fuel would moderately make progress.

In recent years, emission regulations have become more stringent as a result of increased environmental awareness in each region of the world. For diesel engines, reducing NOX emissions is a difficult technical challenge.[1],[2],[3],[4]. To respond to these strict regulations, an exhaust gas aftertreatment system was developed, featuring a lean NOX catalyst (LNC) that uses a new chemical reaction mechanism to reduce NOX. The feature of the new LNC is the way it reduces NOX through an NH3-selective catalytic reduction (SCR), in which NOX adsorbed in the lean mixture condition is converted to NH3 in the rich mixture condition and reduced in the following lean mixture condition. Thus, the new system allows the effective reduction of NOX. However, in order to realize cleaner emission gases, precise engine control in response to the state of the exhaust aftertreatment system is essential.

In recent years, emission regulations have become more stringent as a result of increased environmental awareness in each region of the world. For lean-burn diesel engines, since it is not possible to use three-way catalytic converters, reducing NOX emissions is a difficult technical challenge. To respond to these strict regulations, an exhaust gas aftertreatment system was developed, featuring a lean NOX catalyst (LNC) that uses a new chemical reaction mechanism to reduce NOX. The feature of the new LNC is the way it reduces NOX through an NH3-selective catalytic reduction (SCR), in which NOX adsorbed in the lean mixture condition is converted to NH3 in the rich mixture condition and reduced in the following lean mixture condition. Thus, the new system allows more efficient reduction of NOX than its conventional counterparts. However, an appropriate switching control between lean and rich mixture conditions along with compensation for catalyst deterioration was necessary.

A continuously variable valve lift gasoline engine can improve fuel consumption by reducing pumping loss and increase maximum torque by optimizing valve lift and cam phase according to engine speed. In this research, a new control system to simultaneously ensure good driveability and low emissions was developed for this low fuel consumption, high power engine. New suction air management through a master-slave control made it possible to achieve low fuel consumption and good driveability. To regulate the idle speed, a new controller featuring a two-degree-of-freedom sliding-mode algorithm with cooperative control was designed. This controller can improve the stability of idle speed and achieve the idle operation with a lower engine speed. To reduce emissions during cold start condition, an ignition timing control was developed that combine I-P control with a sliding mode control algorithm.

It is important in the application of bio-ethanol in homogeneous-charge compression ignition (HCCI) engines to investigate the HCCI combustion characteristics of ethanol. As the inhibitory mechanism of ethanol on HCCI combustion is a key factor, simulated chemical reactions are necessary. In this study, chemical reaction simulations in the combustion chamber of a rapid compression machine (RCM) were performed in order to investigate the inhibitory mechanism of ethanol on the HCCI combustion of heptane. The sensitivity analysis results suggested that the OH radical consumption reaction by ethanol that occurs would inhibit the cool flame reaction of heptane. Furthermore, visualization of HCCI combustion with the RCM was conducted using a quartz glass combustion chamber head and ICCD camera. As a result, the cool flame luminescence intensity of heptane was reduced by the addition of ethanol.

Just as CO2 reduction is required of four wheeled vehicles for environmental protection, similar environmental concerns drive the development of motorcycle oil technology. Zinc dialkyldithiophosphate (Zn-DTP) type additives are widely used for engine oil formulations. However, phosphorus compounds are environmental load materials. The reduction of the quantity of phosphorus compounds in engine oils is required to reduce poisoning of three-way catalysts used to purify exhaust gases from internal combustion engines. Mr. Ito and his co-authors1) reported that they developed a sulfur-based additive as a substitute for Zn-DTP. Their non-phosphorus engine oil formulation for four-wheeled vehicles with a sulfur-based additive was examined to evaluate its anti-wear performance using the following test methods:JASO M328 for gasoline engines (KA24E) and JASO M354 for Diesel engine (4D34T4).