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A high compression ratio is an effective means for improving the thermal efficiency of an internal combustion engines. However, a high compression ratio leads to a rapid rise in the combustion pressure, as it causes a high impulse force. The impulse force generates vibrations and noise by spreading in the engine. Therefore, reducing the vibration of the combustion (which increases as the compression ratio increases) can improve the thermal efficiency while using the same technology. We are conducting model-based research on technologies for reducing combustion vibration by applying a granular damper to a piston. To efficiently reduce the vibration, we suppress it directly with the piston, i.e., the source of the vibration. Thus, the damping effect is maximized within a minimized countermeasure range.

Owing to the small size of engines and high injection pressures, it is difficult to avoid the fuel spray impingement on the combustion cylinder wall and piston head in Direct Injection Spark Ignition (DISI) engine, which is a possible source of hydrocarbons and soot emission. As a result, the droplets size and distribution are significantly important to evaluate the atomization and predict the impingement behaviors, such as stick, spread or splash. However, the microscopic behaviors of droplets are seldom reported due to the high density of small droplets, especially under high pressure conditions. In order to solve this problem, a “spray slicer” was designed to cut the spray before impingement as a sheet one to observe the droplets clearly. The experiment was performed in a constant volume chamber under non-evaporation condition, and a mini-sac injector with single hole was used.

The Wankel rotary engine is more compact than conventional piston engines, but its oil and fuel consumption must be reduced to satisfy emission standards and customer expectations. A key step toward this goal is to develop a better understanding of the apex seal lubrication to reduce oil injection while reducing friction and maintaining adequate wear. This paper presents an apex seal dynamics model capable of estimating relative wear and predicting friction, by modeling the gas and oil flows at the seal interfaces with the rotor housing and groove flanks. Model predictions show that a thin oil film can reduce wear and friction, but to a limited extent as the apex seal running face profile is sharp due to the engine kinematics.

It has been required recently that diesel engines for passenger cars meet various requirements, such as low noise, low fuel consumption, low emissions and high power. The key to improve the noise is to reduce a combustion noise known as “Diesel knock noise”. Conventional approaches to reduce the diesel knock are decreasing combustion excitation force due to pilot/pre fuel injection, adding ribs to engine blocks or improving noise transfer characteristics by using insulation covers. However, these approaches have negative effects, such as deterioration in fuel economy and increase in cost/weight. Therefore, modification of engine structures is required to reduce it. We analyzed noise transfer paths from a piston, a connecting rod, a crank shaft to an engine block and vibration behavior during engine operation experimentally, and identified that piston resonance was a noise source.

This study simulates soot formation processes in diesel combustion using a large eddy simulation (LES) model, based on a one-equation subgrid turbulent kinetic energy model. This approach was implemented in the KIVA4 code, and used to model diesel spray combustion within a constant volume chamber. The combustion model uses a direct integration approach with a fast explicit ordinary differential equation (ODE) solver, and is additionally parallelized using OpenMP. The soot mass production within each computation cell was determined using a phenomenological soot formation model developed by Waseda University. This model was combined with the LES code mentioned above, and included the following important steps: particle inception during which acenaphthylene (A2R5) grows irreversibly to form soot; surface growth with driven by reactions with C2H2; surface oxidation by OH radical and O2 attack; and particle coagulation.

The objective of the present study is to analyze soot formation in diesel engine combustion by using multi-dimensional combustion simulations with a parallelized explicit ODE solver. Parallelized CHEMEQ2 was used to perform detailed chemical kinetics in KIVA-4 code. CHEMEQ2 is an explicit stiff ODE solver developed by Mott et al. which is known to be faster than traditional implicit ODE solvers, e.g., DVODE. In the present study, about eight times faster computation was achieved with CHEMEQ2 compared to DVODE when using a single thread. Further, by parallelizing CHEMEQ2 using OpenMP, the simulations could be run not only on calculation servers but also on desktop machines. The computation time decreases with the number of threads used. The parallelized CHEMEQ2 enabled combustion and emission characteristics, including detailed soot formation processes, to be predicted using KIVA-4 code with detailed chemical kinetics without the need for reducing the reaction mechanism.

The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. A model of the oil seals is developed to calculate internal oil consumption (oil leakage from the crankcase through the oil seals) as a function of engine geometry and operating conditions. The deformation of the oil seals trying to conform to housing distortion is calculated to balance spring force, O-ring and groove friction, and asperity contact and hydrodynamic pressure at the interface. A control volume approach is used to track the oil over a cycle on the seals, the rotor and the housing as the seals are moving following the eccentric rotation of the rotor. The dominant cause of internal oil consumption is the non-conformability of the oil seals to the housing distortion generating net outward scraping, particularly next to the intake and exhaust port where the housing distortion valleys are deep and narrow.

The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. In order to better understand oil transport, a laser induced fluorescence technique is used to visualize oil motion on the side of the rotor during engine operation. Oil transport from both metered oil and internal oil is observed. Starting from inside, oil accumulates in the rotor land during inward motion of the rotor created by its eccentric motion. Oil seals are then scraping the oil outward due to seal-housing clearance asymmetry between inward and outward motion. Cut-off seal does not provide an additional barrier to internal oil consumption. Internal oil then mixes with metered oil brought to the side of the rotor by gas leakage. Oil is finally pushed outward by centrifugal force, passes the side seals, and is thrown off in the combustion chamber.

The effects of spray/wall interaction on diesel combustion and soot formation in a two-dimensional piston cavity were studied with a high speed color video camera in a constant volume combustion vessel. The two-dimensional piston cavity was applied to generate the impinging spray flame. In the cavity, the flat surface which plays a role as the cylinder head has a 13.5 degree angle with the injector axis and the impinging point was located 30 mm away from the nozzle tip. Three injection pressures of 100, 150, and 200 MPa and a single hole diesel injector (hole diameter: 0.133mm) were selected. The flame structure and combustion process were examined by using the color luminosity images. Two-color pyrometry was used to measure the line-of sight soot temperature and concentration by using the R and B channels of the color images. The soot mass generated by impinging spray flame is higher than that of the free spray flame.

Internal combustion engines still play a vital role in realizing the low carbon society. For spark ignition engines, further improvement in thermal efficiency can be achieved by increasing both compression and specific heat ratios. In the current work, the authors developed practical technologies to prevent output power loss due to knocking at full load, which is a critical issue for increasing compression ratio. These new technologies allowed to increase the compression ratio significantly and provide an equivalent torque level as a conventional engine. As a result, thermal efficiency has been improved at partial load.

Improvement of indicated thermal efficiency of internal combustion engines is required, and increasing the compression ratio is an effective solution. In this study, using a CAE analysis coupling a 0-dimensional combustion analysis and a 1-dimensional heat conduction analysis, the influence of compression ratio on indicated thermal efficiency and combustion was investigated. As a result, it was found that there was an optimal compression ratio that gave the best indicated thermal efficiency, because the increase of cooling loss caused by high compression was bigger than the increase of theoretical indicated thermal efficiency in some cases. Next, the influence of cooling loss reduction on the optimal compression ratio was investigated. It was found that indicated thermal efficiency improved by reducing cooling loss, because the compression ratio which made the best indicated thermal efficiency was shifted to higher compression ratio.

Understanding of the oil film formation mechanism around a piston skirt is very important to reduce the friction loss at piston skirt. We have investigated lubricant oil film behavior around piston skirt which is affected by piston slap under motoring condition. In this study, a cylinder liner of a commercial engine is displaced with a quartz cylinder. Photographic observations of oil film behavior between the cylinder liner and the piston skirt were performed with two kinds of methods; direct monochromatic photography and LIF (Laser Induced Fluorescence) image using a high speed camera. The oil film distributions were determined from oil boundary observed by the direct photography, and oil film thickness was estimated from the LIF intensity. Differences of the oil film distributions and the oil film thickness depending on piston shapes were investigated for four types of pistons.

Mazda announced that all customers who purchase Mazda cars are provided with the joy of driving and excellent environmental and safety performance under slogan of "Sustainable Zoom-Zoom" long-term vision for technology development. The purpose of this study is to develop a new approach of Life Cycle Assessment (abbreviated to LCA) to be applied to clean energy vehicles and new car models. The improvement of both environmental performance, e.g., fuel consumption, exhaust emissions, vehicle weight reduction, and LCA that is a useful methodology to assess the environmental load of automobiles for their lifecycles has become more important. LCA by inventory analysis, for RX-8 Hydrogen RE as a rotary engine vehicle used hydrogen as clean energy, was carried out and disclosed the world for the first time. LCA for new Mazda 5 was carried out as the portfolio of all models, previously only the specific model equipped with fuel efficiency device based on ISO14040.

Effects of split injection, with a relatively short time interval between the two sprays, on the spray development process, and the air entrainment into the spray, were investigated by using laser induced fluorescence and particle image velocimetry (LIF-PIV) techniques. The velocities of the spray and the ambient air were measured. The cumulative mass of the ambient air entrained into the spray was calculated by using the entrainment velocity normal to the spray boundary. The vortex structure of the spray, formed around the leading edge of the spray, showed a true rotating flow motion at low ambient pressures of 0.1 MPa, whereas at 0.4 MPa, it was not a true rotating flow, but a phenomenon of the small droplets separating from the leading edge of the spray and falling behind, due to air resistance. The development processes of the 2nd spray were considerably different from that of the 1st spray because the 2nd spray was injected into the flow fields formed by the 1st spray.

In order to study alternate methods of Air Fuel ratio (A/F) perturbation for maximizing three-way catalyst conversion efficiency, two methods for measuring the Oxygen Storage Capacity (OSC) of Catalyst were developed on an engine test bench. The first is to measure just the break-through Perturbing Oxygen Quantity (POQ, which is defined as the product of A/F amplitude, perturbation period and gas flow), and the second is to measure the response delay of the rear A/F sensor, which has been improved to be very similar to the former. Then, the OSC values of many catalysts were investigated with different perturbation parameters. The results show that OSC would not be affected by amplitude, period of perturbation and gas flow, and that the best conversion efficiency is obtained when the value of POQ is about 1/2 of the value for OSC. These results suggest that the best way to control perturbation is to keep POQ at 1/2 of OSC by setting perturbation parameters.

Aldehydes are the cause of sick house syndrome or chemical sensitivity and have harmful influences for human beings. In the cabin of vehicle, aldehydes which are included in the volatilization gas from the interior materials, DE emission gas in intake air, cigarette smoke and so on spoil the comfortableness. Active carbon, which has been used as an adsorbent, shows an excellent removal efficiency for most of the gas components by physical adsorption. But for aldehydes, it has difficulty because aldehydes are hard to be adsorbed physically. We have developed new aldehydes adsorbent undergoing addition reaction with gaseous aldehydes on its surface. Aldehydes capture material (ACM) make use of the chemical reaction using a resorcin as a reagent and an H-type zeolite as a water-containing support, and active hydrogen is used as a catalyst to promote the reaction. In addition, we have applied ACM to cabin air filter (CAF) of vehicle.

Today, most widely used synchronizer rings (SNRs) are made of brass (brass SNR). The development of superior SNR to brass SNR has been required for both shift feeling and durability, which are two important requirements for SNRs. Carbon-based friction material (carbon material) is selected to develop superior friction material to brass because carbon material is one of the most durable materials for an application of clutch and brake. Carbon material is placed on the friction surface of SNR (carbon SNR). The structure of carbon material, kinds of raw materials and their combination ratio are selected and optimized. The carbon SNR is confirmed to have higher performance than brass SNR for both shift feeling and durability. At present, our carbon SNRs have been introduced into pickup trucks and SUVs in USA.

A pancake-type constant-volume combustion chamber was used to investigate the combustion and NOx emission characteristics of propane-air and hydrogen-air mixtures under various charge stratification patterns, which were obtained by variations of the initial charge and injected mixture concentrations and the ignition spark timing. A planar laser-induced fluorescence from nitrogen dioxide as gas fuel tracer was applied to measure the mixture distribution in the test chamber. The second harmonic output of pulsed Nd; YAG laser was used as a light source for fluorescence excitation. The fluorescence images were corrected by a gated image-intensified CCD camera. The quantitative analysis of fuel concentration was made possible by the application of linearity between fluorescence intensity and NO2 concentration at low trace level.

In order to control the mixture formation, a mixture injected 4-valve SI engine was developed with a small mixture chamber and mechanically driven mixture injection valve installed into the cylinder head. The mixture injection valve was located at the center of the combustion chamber. The mixture was injected from the final stage of the intake stroke to the beginning of the compression stroke. The mixture distribution and in-cylinder flow field inside the combustion chamber were measured by a pair of laser two-dimensional visualization techniques. A planar-laser-induced exciplex fluorescence technique was used to visualize the in-cylinder mixture formation by obtaining spectrally separated fluorescence images of liquid and vapor phase fuel distribution. Particle image velocimetry (PIV) was used to obtain flow field images. In the case of the mixture injected SI engine, the mixture injected into the swirl center was retained during the compression stroke.

Recently, an audible clattering noise has been noticed in some vehicles during cold engine starts, mainly in the U.S. The clattering is referred to by various names, such as “carbon knock,” “carbon rap,” “mechanical knock” and “combustion chamber deposit interference (CCDI).” CCDI is believed to be caused by the deposit formation in the combustion chamber. In the research effort described here, CCDI was successfully reproduced in a 2.5-liter multipoint injection engine with a polyolefin amine gasoline additive. It was determined that the CCDI was caused by mechanical contact between the piston top and the cylinder head deposits. The vibration due to CCDI originated mainly at the thrust side of the piston right after top-dead-center on compression stroke and was characterized by a high frequency response. Combustion chamber deposit (CCD) formation depends on many factors, including gasoline additives.