Showing papers in "Jsae Review in 1997"

A study of DI diesel combustion under uniform higher-dispersed mixture formation

Abstract: A new concept of combustion system is proposed for the simultaneous reduction of NOx and soot. The injection system is constructed with a new injector driven by a piezo-actuator and mechanical feed pump. The image of combustion was taken by shadow graph method, and an image intensifier was used to detect very weak photic signals in combustion. The level of NOx is about 1/100 that of a conventional Dl diesel engine or lean burn gasoline engine. The mechanism of extremely low NOx and the ignition mechanism are discussed. This system is named the uniform bulky combustion system (UNIBUS). Presently, UNIBUS is only effective under lower load.

A study of the improvement effect of Miller-cycle on mean effective pressure limit for high-pressure supercharged gasoline engines

Abstract: A theoretical adiabatic combustion cycle model of the Miller-cycle was made in order to study its effect on increasing mean effective pressure. The model can evaluate the maximum cylinder pressure, exhaust gas temperature and knocking tendency, which cause reliability problems in high-pressure supercharged gasoline engines. The theoretical calculations with this model and experiments with an actual engine show good coincidence and indicate the advantage of the Miller-cycle, such as higher mean effective pressure, than the Otto-cycle with lower nominal compression ratio while maintaining the same reliability conditions.

Relationship between NOx and SM emissions from DI diesel engine with EGR

Abstract: An experimental study was conducted aimed at understanding the effect of EGR on engine performance and emission under a wide range of engine speed and load. The NOx reduction rate with EGR can be correlated well with O2 concentration in inlet gas over a wide range of injection pressure and timing. However, if the EGR temperature changed, the NOx reduction rate would have different behavior with O2 concentration. Also, smoke emission degeneration with EGR can be correlated with the global A/F ratios. Finally, combustion visualization was used to explain the mechanism of EGR.

A study of engine oil aeration

Abstract: The foaming and aeration properties of crankcase oils were investigated through the observation of foam behavior in the crankcase. Entrained air bubbles in the crankcase oil, that is oil aeration, increased as engine speed and oil temperature increased. This also depended on oil formulation. However, surface foam disappeared in high-speed conditions. It was found that the aeration performance of oils had an effect mainly on the connecting-rod bearing wear under high speed-high temperature engine operating conditions.

Aerodynamic influence of a passing vehicle on the stability of the other vehicles

Abstract: The aerodynamic influence of a passing vehicle on the motion stability of other vehicles is discussed. According to the results of wind tunnel tests and actual car tests, it is found that the interference phenomenon can be treated as a quasi-steady problem when relative speed is small. The influence of relative speed on vehicle motion stability is also examined. A small relative speed can affect the vehicle motion because of its long acting time.

Self-ignition and combustion stability in a methanol fueled low heat rejection ceramic ATAC engine - Analysis of cyclic variation at high wall temperatures and lean burn operation

Abstract: ATAC (Active Thermo-Atmosphere Combustion) is stable at its lean limit because it is bulk-like and non-propagating in nature and is initiated by self-ignition. A low heat rejection methanol-fueled engine was used to investigate the influence of making the fuel-air ratio leaner and increasing the combustion chamber wall temperature on cyclic variation of ATAC ignition and combustion. The cyclic variation of self-ignition timing, combustion duration, total heat release, and instantaneous wall heat flux was analyzed, from which correlations between self-ignition timing and combustion duration, self-ignition timing and total heat release, and combustion duration and total heat release were obtained.

Analysis of transverse vibration in engine timing belt

Abstract: The purpose of this study is to observe the generating mechanism and the reduction method of belt transverse vibration as a cause of timing belt noise. It is known that belt tension affects the transverse vibration. We have described the following two processes: First, the belt resonance frequency varies with the tension and the amplitude increases when the frequency equals the belt meshing frequency. Second, an excitation source exists in the belt tooth crest and bottom land, whose influence varies with the tension. Therefore, adjustment of pulley tooth height is confirmed to be effective for reducing the transverse vibration.

Combustion Improvement for Reducing Exhaust Emissions in IDI Diesel Engine

Abstract: Means for reducing PM from a swirl chamber type diesel engine were examined and the mechanisms of the PM reduction were investigated using both a multi-cylinder and an optically accessible single-cylinder engine. The following points were clarified. (1) At light load, suppression of initial injection rate reduces PM, because of both the change of ignition point to reduce SOF, and the retarded flowout of dense soot from the swirl chamber to reduce smoke. (2) Over medium load, the main cause of the exhaust smoke is hard spray-wall impingement which leads to both fuel adhesion on the wall and the stagnation of rich fuel-air mixture.

Effects of diesel fuel composition on SOF and PAH exhaust emissions

Abstract: Experiments were performed with a six cylinder test engine using both ordinary diesel fuel and synthetic diesel fuel, which has simple hydrocarbon components and no aromatics or sulfur content. SOF is extracted from the particulate sample, then GC and GC-MS analyses were carried out. By comparing the results obtained, the role of high boiling point components in diesel fuel on SOF emission was observed. Further, by adding an artificial sulfur-containing compound and pyrene, which is a four ring polynuclear-aromatic-hydrocarbon (PAH), into the synthetic fuel, the effect of PAH content in fuel on PAH emission in SOF and the increase of SOF with increased sulfur content in fuel, were observed.

Friction loss reduction by new lighter valve train system

Abstract: An aluminum tappet, an aluminum spring retainer, and a thin sintered adjusting shim were developed to produce a lighter valve train. By utilizing these parts, valve train inertia mass was reduced by 28%. Moreover, cam profile and valve spring specifications were redesigned fully to employ the reduced inertia mass for a reduced friction loss. The overall friction loss was reduced by 40%, and this friction loss was achieved in the roller rocker arm system.

Development of electric vehicles

Abstract: The Honda CUV-4 is an electric vehicle for fleet testing. Testing has been conducted in California since August 1994. This paper describes the specifications and structure of the CUV-4 as well as test results, such as the range and energy consumption in FUDS and real-world tests.

Vibration isolation analysis and semi-active control of vehicles with connected front and rear suspension dampers

Abstract: Although dampers and springs have been used for vehicle suspension for a long time, the dampers have been mostly installed independently. This paper deals with a vehicle model where the front and rear dampers are connected by capillary tubes. Expressions for the vibration transmissibility are derived by linearizing the equations of the mass flow through the capillary tubes on the assumption of small variations in volume and pressure of the damper chambers. Theoretical analysis shows that the connected damper system has a preview control effect on the rear ride quality but a low pitch damping without control. A quasi-sky-hook system is introduced for the semi-active control of the connected dampers to improve their performance. The computer simulation results demonstrate a good preview control effect and vibration suppression characteristics of the semi-active system.

Development of rear-end collision avoidance system

Abstract: RCAS (rear-end collision avoidance system) has been developed as a system of ASV (advanced safety vehicle). It is a driver assist system to avoid the rear-end collision by informing the distance headway. It also has automatic braking function in case of emergency and distance warning function to the trailing vehicle. This paper describes the outline of RCAS, techniques about the preceding vehicle recognition and collision potential hazard evaluation. And experimental results about distance headway warning and collision avoidance by automatic braking are reported.

A study on engine bearing performance using EHL analysis and experimental analysis

Abstract: In order to efficiently improve engine bearing durability, we investigated the feasibility of predicting the durability of actual engine bearings by means of hydrodynamic lubrication computations. This paper describes a method of predicting the amount of actual engine bearing wear based on the results of a numerical analysis (EHL analysis) which takes into account the pressure dependence of lubricant viscosity and the elastic deformation of the bearing housing. The wear shape predicted by this method serves as input data for the EHL analysis calculations. The results show that variations in bearing performance caused by wear are substantial. Analyses that incorporate wear shape data make it possible to examine durability under conditions that more closely approximate actual conditions.

Analysis of fuel and combustion behavior during cold starting of SI gasoline engine

Abstract: In order to reduce hydrocarbon emission from spark ignition engines, it is important not only to improve catalyst conversion efficiency but also to reduce directly engine-out hydrocarbon emissions during cold starting and warming-up processes. This paper quantitatively analyzes the fuel behavior during the cold starting process of a modern production engine. Using a specially designed analytical method, cycle-by-cycle behavior of required fuel amount for stable startability and engine-out hydrocarbon were observed. Further, using a specially designed analytical engine with intake and exhaust values driven by hydraulic control, the fuel amount of intake port and cylinder wall-wetting, burned fuel and engine-out hydrocarbon emissions at the first cycle were measured. The effect of fuel properties and fuel atomization were analyzed and characteristics of engine-out hydrocarbon emissions during this process were observed.

Development of expert systems for forging processes

Abstract: The authors have been working on the development of two expert systems for use in the Forging Department of their firm. The first is the previously developed “YOURS” automatic design system for forging dies, which can reduce the design costs and shorten the development time of new parts. The second system, which we call “FORDIA,” has been developed as a means of diagnosing the causes of forging defects. This system employs an AI technique (the “Bayesian Network”) and depicts both empirical knowledge and theoretical knowledge obtained by the FEM analyses.

Improvement in a droplet breakup model for numerical analysis of fuel sprays

Abstract: The Reitz's wave breakup model has been incorporated into the authors' GTT code and modified to improve the accuracy of the numerical prediction of spray behavior. By using this modified wave breakup model, the fuel sprays injected in quiescent or swirling gas and the sprays impinging on a wall were numerically analyzed and the calculated results were compared with experimental results. It was found that this droplet breakup model can better predict the droplet size distributions and the spray tip penetration in both low- and high-pressure ambient gases. The behavior of the sprays in both low- and high-speed swirling gases and that of the sprays impinging on a wall were also better predicted.

Application of a reciprocity technique for measurement of acoustic transfer functions to the prediction of road vehicle pass-by noise

Abstract: A technique based on the principle of acoustic reciprocity has been developed for measuring acoustic transfer functions of sound radiation from vibrating surfaces of the engine, power train, exhaust system and tires. In many realistic cases of sound radiation, reciprocal measurements of transfer functions are usually more convenient and mostly more accurate than the corresponding direct measurements. This paper explain the basic acoustic reciprocity and experimental setup and illustrate its benefits by application to measurements of transfer functions of sound radiation from the engine of a fully trimmed vehicle.

Three-dimensional computation of in-cylinder flow and combustion characteristics in diesel engines-Effect of wall impingement models of fuel droplet behavior on combustion characteristics

Abstract: A computer code called TurboKIVA was used to perform three-dimensional computations to investigate the effects of fuel spray formation on the combustion and emission characteristics of direct and indirect injection diesel engines. As the first step, the code was modified to facilitate quantitative prediction of soot emissions and to improve prediction accuracy. An investigation was then made of the effects of fuel droplet wall impingement models on combustion characteristics. The results showed that combustion performance was influenced by the models, making it important to select a suitable wall impingement model in predicting NO x and soot emissions based on the operating conditions of IDI diesel engines.

Bending energy absorption of extruded aluminum beams

Abstract: The bending collapse behavior of extruded aluminum and hybrid beams was studied theoretically and experimentally. Very good agreement was found between the theoretical results for extruded square section tubes with some partitions. For seam bending energy absorption, the hybrid beams achieved significant reduction of weight compared with traditional reinforced thin-walled steel beams. The strain rate dependence of different heat treated extruded aluminum was explained by the high speed tensile tests. Static and dynamic bending tests were carried out to investigate the influence of different materials, heat treatments and sections on bending energy absorption.

Thermal load in D.I. diesel engine under EGR operation— measurements of steady state temperature of combustion chamber wall surface and intake gas temperature

Abstract: The combustion temperature drops with exhaust gas recirculation (EGR), but the mean gas temperature in the combustion chamber may rise due to the rise of intake gas temperature and the drop of excess air ratio. For the verification of these effects, narrow J-type thermocouples were embedded in the piston and cylinder liner of an automobile D.I. diesel engine, and accurate measurements were conducted accordingly. In addition, the authors developed a measuring method of the intake gas temperature flowing between the intake valve and the seat to study the effect on the thermal loads on the combustion chamber wall.

Optimization in performance of Lysholm compressor

Abstract: The relationship between rotor parameters and performance of a high efficiency type supercharger (Lysholm compressor) was studied. It is necessary that Lysholm compressor satisfies both performance and mountability. Several methods to reduce driving loss, of Lysholm compressor under unloading condition were also introduced. Low built-in pressure ratio and by-pass system is effective.

An electronically controlled fuel injection system for new diesel engines

Abstract: The new system makes it possible to improve accuracy and provide more flexibility in the control of fuel injection volume and injection timing compared with conventionally-used mechanical control systems.