Search Results

It is well known that a high-pressure fuel injection is effective for the reduction in particulates and smoke emissions. Exhaust gas recirculation (EGR) is effective for the reduction in NOX emission. In this study an experiment aiming to understand more comprehensive combustion under the condition of EGR and high-pressure fuel injection was carried out by using gas sampling method for the purpose of understanding what occurred inside the spray before and after combustion. The number of combustion cycles in this engine can be controlled in order to change EGR conditions by adjusting the residual gas concentration in the cylinder. Main results were: (1) Close to the nozzle tip, the sampling gas data showed little reaction which implies that combustion never occurs in this area during the injection period. (2) In the case of high-pressure fuel injection O2 concentration decreased faster and air dilution was more active and earlier.

An experimental study aiming to investigate the effects of combustion chamber geometry on combustion process has been carried out in an optically accessible DI diesel engine. The combustion processes of three different chamber geometries, included the production type, were revealed and the flame movement behaviors such as the distribution of flame velocity vectors and the averaged flame velocity inside and outside the combustion chamber were measured by means of a cross-correlation method. Meanwhile, an endoscope system was used to acquire information about the distribution of flames inside and outside the chamber. BY comparing the flame movement and distribution between different chambers and nozzle protrusions, the results showed that; The chamber geometry has significant effect on the flame velocity, the flame velocities of the reentrant chamber were larger than that of the dish chamber during expansion period.

A lot of countermeasures have been developed in order to reduce interior noise. For example, improvements of rubber mount characteristics and other measures have been implemented. Recently electromagnetic active engine mounts based on a hydraulic engine mount have been developed. They are significantly effective for the reduction of the booming noise which is unpleasant for passengers. Although the LMS algorithm has been generally used for the active control, it has been used only for reducing booming noise. The authors developed a new control method in order to reduce not only the booming noise but also the noise and the vibration over wide frequency band for comfortable vehicle interior space. The authors studied the method which determines the feedback gain according to various conditions by modifying LMS algorithm. In this modified LMS algorithm, only an error signal was used as an input signal.

To analyze the combustion phenomena of DI diesel engines in detail, the “cross-correlation method” and the “two-color method” have been applied to measure the combustion flame motion and the flame temperature, respectively by processing the high speed photographs. The purpose of this investigation is to study the effects of engine parameters such as pumping rate, injector nozzle hole size, and injection timing on combustion processes; particularly on flame motion and flame temperature. The results showed that the flame motion was more active during the injection period; and after the end of injection, the motion of flame was largely governed by the air swirl. Increasing fuel pumping rate and using a small hole area injector nozzle, caused the flame motion to become more active, especially during the injection period. The flame temperature was higher with both increased pumping rate and advanced injection timing.

Supercharging as the method of increasing the output of diesel engines has a long history. Recently, because the potential for lower exhaust emissions for a given power output, supercharging has been considered as a method to reach increasingly strict emissions standards. Some research investigating the effects of supercharging has shown favorable results in terms of emissions(e.g.[1][2][3] *). Also some fundamental studies have examined the effect of ambient pressures on the characteristics of spray and ignition in constant volume combustion borb[4][5][6][7]. However, for further improvement of combustion when utilizing supercharging, more detailed information inside of the combustion chamber is needed about the effects of supercharging on fuel spray and combustion. In order to gather this information, it is necessary to observe the processes within the combustion chamber of a supercharged engine.

The behavior of air-entrainment in a Diesel fuel spray was studied by analyzing the air movement around a free non-evaporated Diesel fuel spray in a pressurized vessel. To measure the air movement around the spray. The density difference in the air near the surface of spray was measured as a tracer of the moving air. This was accomplished heating a stainless steel (SUS) wire with large current. The movement of air caused by the air-entrainment into the spray was recorded by a high speed camera system. By analyzing the recorded air movement, the air-entrainment was obtained. The effects of nozzle hole diameter, injection velocity and ambient gas density on the air-entrainment behavior were investigated. Some discussions were added to help considering the complex phenomena of air-entrainment into a Diesel spray, based on comparing the averaged air/fuel ratio inside the spray with both values of measurement and predicted by momentum theory.

Premixed diesel combustion was performed and various characteristics examined with fuel injection timing near top dead center (TDC). A lean and uniform fuel-air mixture was found to during 25° C.A. with a narrow injection angle (27.5° with respect to horizontal), shallow dish combustion chamber, and low cetane number fuel (CN=19). These conditions enabled low NOx combustion in no exhaust gas re-circulation (EGR), despite fuel injection timing around 25° BTDC. Furthermore, HC emissions were lower than with premixed diesel combustion of the early injection type. Because fuel injection timing was near TDC, the volume of the mixture dispersed to a squish area was decreased. This combustion mode was also achieved with a high-cetane fuel (conventional diesel fuel) and high EGR rate conditions. However, in this case, it was difficult to adjust the ignition timing near top dead center. This combustion system also showed good performance in conventional diesel combustion mode.

Fuel injection rate pattern represents an important factor for emissions reduction. In this study, fuel spray photography, combustion photography and experimental data analysis indicate. 1) effect of pilot injection 2) effect of a gradual shaped injection profile using nozzle needle lift control 3) effect of a boot shaped injection profile using pressure control Common rail type fuel injection equipment was used in these experiments, and the engine was single cylinder naturally aspirated D.I. diesel engine. As a result, we found out that it is important to control the pre-mixed combustion for NOx reduction and to activate the diffusion combustion for smoke, and various fuel injection rate patterns we studied have similar effect on combustion and emissions at the most suitable condition respectively.

Various premixed diesel combustion concepts are suggested as the way of simultaneous reduction of NOx and PM emission from diesel engines. However, every combustion concept has common problems, such as difficulty of ignition timing control, a great deal of HC and CO emissions and limiting the operation region to low load operation. The purpose of this study is to expand the operation region of Premixed Compression Ignition (PCI) combustion, which is a premixed diesel combustion concept that realizes the fuel injection around the top dead center. As a result of examining it with EGR, supercharging operation and low compression ratio piston, PCI combustion region was expanded to cover higher load operation. And the high load region was limited by not only stoichiometric air fuel ratio but also permissible maximum in-cylinder pressure.

DME as a fuel for compression ignition (diesel) engines has been actively studied for about ten years due to its characteristically low pollution and reputation as a “smokeless fuel”. During this time, the practical application is taking shape based on necessary tasks such as analysis of injection and combustion, engine performance, and development of experimental vehicles. At this moment, standardization of DME as a fuel was started under ISO in 2007. There are concerns regarding the impurities in DME regarding the mixing during production and distribution as well as their effect on additives for lubricity and odor. In this report, the effect of DME fuel impurities on performance of a DME powered diesel engine was investigated. The platform was a DME engine with common-rail fuel injection and was evaluated under partial load stable mode and Japanese transient mode (JE05) testing parameters.

In-cylinder total sampling technique utilizing a single-cylinder diesel engine equipped with hydraulic valve actuation system has been developed. In this study, particulate matter (PM) included in the in-cylinder sample gas was collected on a quartz filter, and the polycyclic-aromatic hydrocarbons (PAHs) component and soot were subsequently quantified by thermal desorption-gas chromatograph mass spectrometry (TD-GCMS) and a carbon analyzer, respectively. Cylinder-averaged histories of PAHs and soot were obtained by changing the sampling timing. It was found that decreasing intake oxygen concentration suppresses in-cylinder soot oxidation, and the fuel with higher aromatic and naphthenic contents accelerates soot production.

This paper introduced a very simple method to measure the liquid phase of spray in an optically accessible DI diesel engine. Particular attention was paid to easy usage and maintaining the compression ratio of the real engine. As a result, a less-expensive 4 W argon laser was used as the beam source and an E-10 high-speed camera was used for continuously observing the elastic-scatter liquid phase image. Meanwhile, the compression ratio can be kept as the real engines by this method. Through this method, the effects such as injection pressure, nozzle specification, intake air boost and temperature on liquid phase penetration before ignition were investigated. Reducing nozzle hole diameter decreased the length of the liquid phase. Increasing injection pressure hastened the evolution of liquid phase, while the liquid phase length varied complexly. Increasing intake air boost considerably shortened the liquid phase penetration and ignition delay.

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, consisting of a cylinder head, a cylinder block and a bed-plate. Each has the same outer size of 150mm × 150mm; the different heights are 100mm, 200mm and 80mm respectively. Those dimensions were determined following the dimensions for a diesel engine in lightweight commercial vehicle with the bore size of 100mm and the crankshaft main bearing diameter of 60mm. We chose 112 of measuring points on the structure surfaces and performed a series of impact tests, for the following cases: (a) When the cylinder head and the bed-plate were fastened to the cylinder block by two sets of four ISO M10 tap-bolts, each with the lengths ℓ1 =117mm and ℓ2 =97mm. (b) When the cylinder head and the bed-plate were fastened to the cylinder block together by a set of four ISO M10 through-bolts of grip length ℓ3 =380mm.

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, with bore sizes of 100mm. Each engine model consists of a cylinder head, a cylinder block and a bedplate. Each has the same size of 150mm × 150mm, with different heights of 100mm, 200mm and 80mm, respectively. By choosing 112 measuring points on the structure surfaces, we performed a series of impact tests for the following cases, (a) The cylinder head and the bedplate were fastened to the cylinder block by two sets of ISO M10 Tap-bolts, each with the lengths l1=117mm and l2=97mm. (b) The cylinder head and the bedplate were fastened to the cylinder block together by a set of ISO M10 Through-bolts of grip length l3=380mm.

Newly designed laboratory measurement system, which reproduces particle number size distributions of both nuclei and accumulation mode particles in exhaust emissions, was developed. It enables continuous measurement of nano particle emissions in the size range between 5 and 1000 nm. Evaluations of particle number size distributions were conducted for diesel vehicles with a variety of emission aftertreatment devices and for gasoline vehicles with different combustion systems. For diesel vehicles, Diesel Oxidation Catalyst (DOC), urea-Selective Catalytic Reduction (urea-SCR) system and catalyzed Diesel Particulate Filter (DPF) were evaluated. For gasoline vehicles, Lean-burn Direct Injection Spark Ignition (DISI), Stoichiometric DISI and Multi Point Injection (MPI) were evaluated. Japanese latest transient test cycles were used for the evaluation: JE05 mode driving cycle for heavy duty vehicles and JC08 mode driving cycle for light duty vehicles.

Three dimensional computational model has been developed to predict the macroscopic behavior of the fuel spray in D. I. diesel engines. The model was based on the KIVA-II code with modification of some submodels that it can deal with the observed phenomena such as liquid column near the nozzle tip and spray impingement on a wall. Firstly, this model was verified by comparing the prediction with the experimental results in a constant volume vessel. Secondly with application to a D.I. diesel engine, the detailed behavior of the spray in a combustion chamber was revealed. Moreover, the engine performance under different spray angles were discussed with the prediction of this model.

Single cylinder engine testing was carried out to clearly understand the test results of multi-cylinder engines reported by the Diesel WG in JCAP (Japan Clean Air Program) (1), (2), (3) and (4). In this tests, engine specifications such as fuel injection pressure, nozzle hole diameter, turbo-charging pressure, EGR rate, and fuel properties such as 1-, 2-, 3-ring aromatics content, n-,i-paraffins content, and T90 were parametrically changed and their influence on the emissions were studied. PM emission generally increased in each engine condition with increased aromatic contents and T90. In particular, multi ring aromatics brought about large increases in PM regardless of the engine conditions. The influence of fuel properties on NOx emission is smaller than the influence on PM emission. Some other fuels that have various side chain structures of 1-ring aromatics, normal paraffins only and various naphthene contents were also investigated.

The dynamic behaviors of power-plant have much effect on interior noises and vibrations of passenger cars, especially, in the frequency range below 1000 Hz. So it is very important to estimate the vibrations of power-plant at the design stage. To predict the dynamic behaviors of power-plant including the rotating elastic crankshaft system, the time domain dynamic simulation methods have been applied, however such analyses require much time and resource of computer. In this report, the exciting forces to the cylinder block are derived in the frequency domain from both the dynamic stiffness of bearing oil films and the dynamic displacements of crankshaft journals, so that the computation time is reduced considerably. To estimate the displacements of the crankshaft journals, the vibrations of an engine crankshaft system including crank journal oil films under firing conditions are calculated using the dynamic stiffness matrix method in the frequency domain.

Further improvement in fuel consumption is needed for diesel engines to address regulatory requirement particularly for heavy duty diesel in Japan enforced in 2015, in addition to the compliance to the regulatory requirements for exhaust emission, which seems to be more stringent in future. The authors have participated in the project of “Comprehensive Technological Development of Innovative, Next-Generation, Low-Pollution Vehicles” organized by New Energy and Industrial Technology Development Organization (NEDO), and innovative devices such as multi stage boosting system, ultra high-pressure fuel injection system and variable valve actuation (camless) system had been developed in this project from a standpoint of simultaneous improvement of fuel consumption and exhaust emission. In camless system, intake and exhaust valves are driven by hydraulic pressure. So, fully flexible setting of opening and closure timings and lift of the intake and exhaust valves is possible.

Study of DME diesel engines was conducted to improve fuel consumption and emissions of its. Additionally, DME trucks were built for the promotion and the road tests of these trucks were executed on EFV21 project. In this paper, results of diesel engine tests and DME truck driving tests are presented. As for DME diesel engines, the performance of a DME turbocharged diesel engine with LPL-EGR was evaluated and the influence of the compression ratio was also explored. As for DME trucks, a 100,000km road test was conducted on a DME light duty truck. After the road test, the engine was disassembled for investigation. Furthermore, two DME medium duty trucks have been developed and are now the undergoing practical road testing in each area of two transportation companies in Japan.