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Premixed diesel combustion blending high volatility fuels into diesel fuel were investigated in a modern diesel engine. First, various fractions of normal heptane and diesel fuel were examined to determine the influence of the blending of a highly ignitable and volatile fuel into diesel fuel. The indicated thermal efficiency improves almost linearly with increasing normal heptane fraction, particularly at advanced injection timings when the fuel is not injected directly into the piston cavity. This improvement is mainly due to decreases in the other losses, ϕother which are calculated with the following equation based on the energy balance. ηu: The combustion efficiency calculated from the exhaust gas compositions ηi: The indicated thermal efficiency ϕex: The exhaust loss calculated from the enthalpy difference between intake and exhaust gas The decreases in the other losses with normal heptane blends are due to a reduction in the unburned fuel which does not reach the gas analyzer.

Premixed diesel combustion offers the potential of high thermal efficiency and low emissions, however, because the rapid rate of pressure rise and short combustion durations are often associated with low temperature combustion processes, noise is also an issue. The reduction of combustion noise is a technical matter that needs separate attention. Engine noise research has been conducted experimentally with a premixed diesel engine and techniques for engine noise simulation have been developed. The engine employed in the research here is a supercharged, single cylinder DI diesel research engine with a high pressure common rail fuel injection system. In the experiments, the engine was operated at 1600 rpm and 2000 rpm, the engine noise was sampled by two microphones, and the sampled engine noise was averaged and analyzed by an FFT sound analyzer.

When fuel is vaporized and mixed well with air in the cylinder of premixed diesel engines, the mixture auto-ignites in one burst resulting in strong combustion noise, and combustion noise reduction is necessary to achieve high load premixed diesel engine operation. In this paper, an engine noise analysis was conducted by engine tests and simulations. The engine employed in the experiments was a supercharged single cylinder DI diesel engine with a high pressure common rail fuel injection system. The engine noise was sampled by two microphones and the sampled engine noise was averaged and analyzed by an FFT sound analyzer. The engine was equipped with a pressure transducer and the combustion noise was calculated from the power spectrum of the FFT analysis of the in-cylinder pressure wave data from the cross power spectrum of the sound pressure of the engine noise.

The influence of fuel properties on the operational range and the thermal efficiency of premixed diesel combustion was evaluated with an ordinary diesel fuel, a primary reference fuel for cetane numbers, three primary reference fuels for octane numbers, and two normal heptane-toluene blend fuels in a single-cylinder DI diesel engine. The fuel injection timing was set at 25°CA BTDC and the maximum rate of pressure rise was maintained below 1.0 MPa/°CA when lowering the intake oxygen concentration by cooled EGR. With increasing octane numbers, the higher intake oxygen concentration can be used, resulting in higher indicated thermal efficiency due to a higher combustion efficiency. The best thermal efficiency at the optimum intake oxygen concentration with the ordinary diesel fuel is lower than with the primary reference fuels with the similar ignitability but higher volatility.

Water and diesel fuel emulsions containing 13% and 26% water by volume were investigated in a modern diesel engine with relatively early pilot injection, supercharging, and cooled EGR. The heat release from the pilot injection with water emulsions is retarded toward the top dead center due to the poor ignitability, which enables larger pilot and smaller main injection quantities. This characteristic results in improvements in the thermal efficiency due to the larger heat release near the top dead center and the smaller afterburning. With the 26% water emulsion, mild, smokeless, and very low NOx operation is possible at an optimum pilot injection quantity and 15% intake oxygen with EGR at or below 0.9 MPa IMEP, a condition where large smoke emissions are unavoidable with regular unblended diesel fuel. Heat transfer analysis with Woschni's equation did not show the decrease in cooling loss with the water emulsion fuels.

Combustion and exhaust gas emissions of alcohol and vegetable oil blends including a 20% ethanol + 40% 1-butanol + 40% vegetable oil blend and a 50% 1-butanol + 50% vegetable oil blend were examined in a single cylinder, four-stroke cycle, 0.83L direct injection diesel engine, with a supercharger and a common rail fuel injection system. A 50% diesel oil + 50% vegetable oil blend and regular unblended diesel fuel were used as reference fuels. The boost pressure was kept constant at 160 kPa (absolute pressure), and the cooled low pressure loop EGR was realized by mixing with a part of the exhaust gas. Pilot injection is effective to suppress rapid combustion due to the lower ignitability of the alcohol and vegetable oil blends. The effects of reductions in the intake oxygen concentration with cooled EGR and changes in the fuel injection pressure were investigated for the blended fuels.

The HCCI engine offers the potential of low NOx emissions combined with diesel engine like high efficiency, however HCCI operation is restricted to low engine speeds and torques constrained by narrow noise (HCCI knocking) and misfiring limits. Gasoline like fuel vaporizes and mixes with air, but the mixture may auto-ignite at the same time, leading to heavy HCCI knocking. Retarding the CA50 (the crank angle of the 50% burn) is well known as a method to slow the maximum pressure rise rate and reduce HCCI knocking. The CA50 can be controlled by the fuel composition, for example, di-methyl ether (DME), which is easily synthesized from natural gas, has strong low temperature heat release (LTHR) characteristics and ethanol generates strong LTHR inhibitor effects. The utilization of DME-ethanol binary blended fuels has the potential to broaden the HCCI engine load-speed range.

Unsteady aerodynamic forces acting on vehicles during a dynamic steering action were investigated by numerical simulation, with a special focus on the vehicles' yaw and lateral motions. Two sedan-type vehicles with slightly different geometries at the front pillar, side skirt, under cover, and around the front wheel were adopted for comparison. In the first report, surface pressure on the body and total pressure behind the front wheel were measured in an on-road experiment. Then the relationships between the vehicles' lateral dynamic motion and unsteady aerodynamic characteristics during cornering motions were discussed. In this second report, the vehicles' meandering motions observed in on-road measurements were modeled numerically, and sinusoidal motions of lateral, yaw, and slip angles were imposed. The responding yaw moment was phase averaged, and its phase shift against the imposed slip angle was measured to assess the aerodynamic damping.

This study makes use of the detailed mechanisms of n-heptane combustion, from gas reactions to soot particle formation and oxidation, and a two-stage model based on the CHEMKIN reactor network is developed and used to investigate the trade-off between soot and NOx emissions. The effects of the equivalence ratio, EGR, ambient pressure and temperature, and initial particle diameter are observed for various residence times. The results show that high rates of NOx formation are unavoidable under conditions where high reduction rates of soot particles are obtained. This suggests that suppression of the amount of soot during the formation stage is essential for simultaneous reductions in engine-out soot and NOx emissions.

Port injection of ethanol addition as an ignition inhibitor was implemented to control ignition timing and expand the operating range in DME fueled HCCI combustion. The ethanol reduced the rate of low-temperature oxidation and consequently delayed the onset of the high-temperature reaction with ultra-low NOx over a wide operating range. Along with the ethanol addition, changes in intake temperature, overall equivalence ratio, and engine speed are investigated and shown to be effective in HCCI combustion control and to enable an extension of operation range. A chemical reaction analysis was performed to elucidate details of the ignition inhibition on low-temperature oxidation of DME-HCCI combustion.

Silent, clean, and efficient combustion was realized with emulsified blends of aqueous ethanol and diesel fuel in a DI diesel with pilot injection and cooled EGR. The pilot injection sufficiently suppressed the rapid combustion to acceptable levels. The thermal efficiency with the emulsified fuel improved as the heat release with the pilot injection was retarded to near top dead center, due to poor ignitability and also due to a reduction in afterburning. With the emulsified fuel containing 40 vol% ethanol and 10 vol% water (E40W10), the smokeless operation range can be considerably extended even under low fuel injection pressure or low intake oxygen content conditions.

Large eddy simulation based on high-performance computing technique was conducted to investigate the unsteady aerodynamic forces acting on a full-scale heavy duty truck subjected to sudden crosswind. The CFD results were applied to evaluate the effect of the unsteady external forces on a vehicle motion, as a first step toward a more reliable vehicle motion analysis. As the first report, the numerical method was validated on the DNW wind-tunnel data by comparing the time-averaged drag and lateral forces at various yawing angles up to 10 degrees. Then the method was applied to the case when the vehicle goes through the crosswind region. The time series of the aerodynamic forces were acquired and discussed through the visualization of instantaneous flow structures around the vehicle. It was observed that drastic undershooting and overshooting of the yawing moment acts on the vehicle during the rushing in and out process.

The effect of unsteady aerodynamics on the motion of a heavy duty truck subjected to sudden crosswinds was analyzed in vehicle-dynamics simulations. Large eddy simulation based on high-performance computing (LES-HPC) was applied to evaluate the effect of unsteady external forces on vehicle motion as a first step toward a more reliable vehicle motion analysis. Before the vehicle-dynamics simulations, the steady and unsteady aerodynamics of a simplified model of a heavy truck developed in our first report were analyzed by HPC-LES for various aerodynamic yaw angle conditions. On the basis of these aerodynamic analyses, two vehicle-dynamics simulations were conducted for transient crosswind conditions. One simulation was coupled with unsteady aerodynamic forces and the other applied a conventional approach with quasi-steady aerodynamics.

Premixed diesel combustion modes including low temperature combustion and MK combustion are expected to realize smokeless and low NOx emissions. As ignition must be delayed until after the end of fuel injection to establish these combustion modes, methods for active ignition control are being actively pursued. It is reported that alcohols including methanol and ethanol strongly inhibit low temperature oxidation in HCCI combustion offering the possibility to control ignition with alcohol induction. In this research improvement of diesel combustion and emissions by ethanol intake port injection for the promotion of premixing of the in-cylinder injected diesel fuel, and by increased EGR for the reduction of combustion temperature.

The control of fuel ignition timing and suppression of rapid combustion in a premixed charge compression ignition (PCCI) engine was attempted with direct in-cylinder injection of water as a reaction suppressor. The water injection significantly reduced the heat release at low temperature oxidation, which suppressed the increase in charge temperature after the low temperature oxidation and the rapid combustion caused by the high temperature oxidation. The possible engine operating range with ultra low NOx and smokeless combustion was extended to a higher load range with the water injection. Rapid combustion was suppressed by reductions in the maximum in-cylinder gas temperature due to water injection while the combustion efficiency suffered. Therefore, the maximum charge temperature needs to be controlled within an extremely limited range to maintain a satisfactory compromise between mild combustion and high combustion efficiency.

The past efforts to develop aluminum alloy engine parts were focused on the formulation of chemical composition rather than the heat treatment conditions of aluminum alloys. Only a few studies have been made on optimizing heat treatment conditions. This paper deals with the effects of artificial aging on two aluminum alloys, A356 and A319, which have been often used for engine cylinder heads. The aluminum alloys were artificially aged under several different conditions after T6 heat treatment. The alloys were tested for such mechanical properties as pure tension, cyclic loading resistance and thermo-mechanical fatigue failure. The microstructure was observed by TEM to see the effects on microstructure in terms of mechanical properties.

Critical for the use of aluminum alloys for cylinder heads are strength and durability. In our study, the mechanism of the low cycle fatigue and creep was clarified based on the mechanical properties of aluminum alloys, such as tensile, compressive, thermal fatigue and creep characteristics, which were determined by conducting tests on test pieces. The behavior of a cylinder head under cyclic thermal condition was represented by using a high-precision analysis method with cyclic creep taken into consideration. Moreover, the high-precision analysis method turned out to be effective in estimating a low cycle fatigue life under the cyclic thermal condition.

Smokeless and ultra low NOx combustion without knocking in a dual-fuel diesel engine with induced LPG as the main fuel was established with a uniquely developed piston cavity divided by a lip in the sidewall. A small quantity of diesel fuel was directly injected at early compression stroke into the lower part of the cavity as an ignition source for this confined area, and this suppressed explosively rapid combustion just after ignition and spark-knock like combustion at later stage. A combination of the divided cavity, EGR, and intake air throttling was effective to simultaneously eliminate knocking, and reduce THC and NOx significantly.

Ultra low emissions and high performance combustion was achieved with a combination of high EGR, a three-way catalyst, and a highly oxygenated liquid fuel, neat dimethoxy methane (DMM), in an ordinary DI diesel engine. The smokeless nature of neat DMM effectively allowed stoichiometric diesel combustion by controlling BMEP with EGR. NOx, THC, and CO emissions were reduced with a three-way catalyst. At lower BMEP with excess air, the EGR effectively reduced NOx. High-speed video in a bottom view type engine revealed that luminous flame decreased with increased fuel oxygen content and almost disappeared with DMM.

The fuel spray distribution in a DI diesel engine with pilot injection was actively controlled by pilot and main fuel injections at different piston positions to prevent the main fuel injection from hitting the pilot flame. A CFD analysis demonstrated that the movement of the piston with a cavity divided by a central lip along the center of the sidewall effectively separates the cores of the pilot and main fuel sprays. Experiments showed that an ordinary cavity without the central lip emitted more smoke, while smokeless, low NOx operation was realized with a cavity divided by a central lip even at heavy loads where ordinary operation without pilot injection emits smoke.