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Technical Paper

Effects of Gas Flow and Mixture Properties on Engine-Out HC Emissions

1996-10-01
961952
The geometry and area of the notch in the swirl control valve installed in the intake port were varied to analyze the effects on HC emissions. A swirl control valve functions to promote the formation of a homogeneous mixture, enabling the amount of liquid fuel supplied to the cylinder to be reduced. For this reason, it is difficult to obtain an added effect through the combined use of a swirl control valve and an auxiliary-air type of injector for assisting fuel atomization. Tumble (vertical swirl) flow fields are effective in shortening the combustion period. This results in a higher exhaust gas temperature at an equivalent level of combustion stability. It was thought that swirl flow fields produce residual gas flow in the cylinder after the completion of the main combustion period. It is surmised that the residual gas flow functions to diffuse and promote after-burning of the unburned HC layer.
Technical Paper

Effects of Swirl/Tumble Motion on In-Cylinder Mixture Formation in a Lean-Burn Engine

1996-10-01
961994
Flow measurement by laser Doppler velocimetry and visualization of in-cylinder fuel vapor motion by laser induced fluorescence were performed for various types of intake systems that generated several different combinations of swirl and tumble ratios. The measured results indicate that certain swirl and tumble ratios are needed to achieve charge stratification in the cylinder. Performance tests were also carried out to determine the combustion characteristics of each intake system. Then, the features of combustion when the charge stratification was realized was analyzed.
Technical Paper

Prediction of Crank Pin Journal Temperature Based on the Oil Flow Rate

1998-05-04
981403
Improving the durability and reliability of crankshaft bearings has become an important issue for automotive engines recently because of conflicting demands for lower fuel consumption and higher power output. This study focused on the connecting rod big-end bearing which is subjected to harsher operating conditions on account of these requirements. It is known that the crank pin journal temperature is an indicator of big-end bearing seizure. Having a simple method for predicting the crank pin journal temperature with the required accuracy at the design stage is indispensable to efficient engine development. In this study, analyses were first conducted to determine the oil flow rate at the big-end bearing which is a major determinant of the crank pin journal temperature.
Technical Paper

Development of a High-Pressure Fueling System for a Direct-Injection Gasoline Engine

1998-05-04
981458
A direct-injection gasoline engine that uses a stratified charge combustion process was developed by Nissan and released in the Japanese market toward the end of 1997. This new engine is based on Nissan's VQ engine, which enjoys a good reputation for its quick throttle response and low fuel consumption, and has been developed to accomplish the objectives of reducing fuel consumption by stratified charge combustion and securing high power output. The fuel injectors are connected by an arrangement of lightweight, small-diameter fuel lines that distribute fuel to each injector under high pressure. This system was adopted in order to reconcile the use of an aerodynamic straight intake port with the desired fuel injection position. The use of a casting net injector, which uniformly distributes the fuel spray above the piston, makes it possible to accomplish stratified charge combustion with a shallow-bowl piston.
Technical Paper

Mixture Formation and Combustion Performance in a New Direct-Injection SI V-6 Engine

1998-05-04
981435
One advantage of a direct-injection S.I. engine is lower fuel consumption due to the use of lean stratified charge combustion. Another advantage is greater power output resulting from evaporation of the fuel in the cylinder. A critical factor in making the most of these advantages is to achieve optimum mixture formation for both stratified and homogeneous charge combustion. To achieve the optimum mixture, the new direct-injection S.I. V-6 engine adopts a piston with a shallow bowl, a valve that changes in-cylinder air motion between swirl and tumble by opening and closing one side of separated air intake port, an air intake port that has optimized inward and port angle to induces swirl in the piston bowl, and a CASTING NET injector that injects the hollow cone spray in a deflected pattern toward the spark plug.
Technical Paper

Turbulence and Cycle-by-Cycle Variation of Mean Velocity Generated by Swirl and Tumble Flow and Their Effects on Combustion

1995-02-01
950813
Combinations of swirl flow and tumble flow generated by 13 types of swirl control valve were tested by using both impulse steady flow rig and LDV. Comparison between the steady flow characteristics and the result of LDV measurement under motoring condition shows that tumble flow generates turbulence in combustion chamber more effectively than swirl flow does, and that swirling motion reduces the cycle by cycle variation of mean velocity in combustion chamber which tends to be generated by tumbling motion. Performance tests are also carried out under the condition of homogeneous charge. Tumble flow promotes the combustion speed more strongly than expected from its turbulence intensity measured by LDV. It is also shown that lean limit air fuel ratio does not have a strong relation with cycle variation of mean velocity but with turbulence intensity.
Technical Paper

Development of a New-Generation Lightweight 3-Liter V6 Nissan Engine

1994-03-01
940991
This paper presents a new-generation, lightweight, 3-liter V6 engine that has been developed for use in the next Nissan Maxima. The distinctive features of this new engine, VQ30DE, is its compact, lightweight design and excellent fuel economy. The basic construction of the engine is characterized by its 60-degree V6 configuration, chain-driven DOHC and high-pressure die cast aluminum cylinder block. A two-way cooling system was adopted with the aim of shortening the warm-up time of the cylinder liners. The new engine has been designed to comply with the tougher emission standards, the OBD-II requirements and California's new evaporative emission standard.
Technical Paper

Application of Predictive Noise and Vibration Analysis to the Development of a New-Generation Lightweight 3-Liter V6 Nissan Engine

1994-03-01
940993
The target performance of a new engine has to be obtained under various restrictions such as cost and weihgt. It is particularly important to predict the engine noise and vibration performance at an early stage. For this purpose the analytical methods have been developed, which include the prediction of the absolute noise and vibration level by inputting a given exciting force into the model. These methods were applied to the development of the new engine. As a result, the characteristics of an aluminum cylinder block were used effectively to achieve a new lightweight V6 engine with low noise and vibration levels.
Technical Paper

A Study on Engine Bearing Performance Focusing on the Viscosity-Pressure Characteristic of the Lubricant and Housing Stiffness

1996-05-01
961144
It is important to understand the influence of housing stiffness on bearing performance, particularly for the connecting rod bearings of automotive engines. It is known that the engine lubricant shows a piezoviscous characteristic whereby its viscosity changes under the influence of pressure. Engine bearings under a heavy load are apt to be influenced in this way. In this study, the effects of connecting rod stiffness and lubricant piezoviscosity on bearing performance were examined by elastohydrodynamic lubrication (EHL) analysis under conditions corresponding to the high-speed operation of an actual engine. The results indicated that under such heavy load conditions housing stiffness greatly affects friction loss because of lubricant piezoviscosity. It was also found that the piezoviscosity of the lubricant has a large effect on bearing performance, as does its viscosity under atmospheric pressure.
Technical Paper

Three-Dimensional Computation of the Effects of the Swirl Ratio in Direct-Injection Diesel Engines on NOx and Soot Emissions

1996-05-01
961125
Three-dimensional computation has been applied to analyze combustion and emission characteristics in direct-injection diesel engines. A computational code called TurboKIVA was used to investigate the effects of the swirl ratio, one of the fundamental factors related to combustion control, on combustion characteristics and NOx and soot emissions. The code was first modified to calculate soot formation and oxidation and the precise behavior of fuel drops on the combustion chamber wall. As a result of improving calculation accuracy, good agreement was obtained between the measured and predicted pressure, heat release rate and NOx and soot emissions. Using this modified version of TurboKIVA, the effects of the swirl ratio on NOx and soot emissions were investigated. The computational results showed that soot emissions were reduced with a higher swirl ratio. However, a further increase in the swirl ratio produced greater soot emissions.
Technical Paper

A Comparison of Gas Chromatography-Based Methods of Analyzing Hydrocarbon Species

1994-03-01
940740
Gas chromatographic methods for analyzing hydrocarbon species in vehicle exhaust emissions were compared in terms of their collection efficiency, detection limit, repeatability and number of species detected using cylinder gas and tailpipe emission samples. The main methods compared were a Tenax cold trap injection (TCT) method (C5-C12 HCs) and a cold trap injection (CTI) method (C2-C4 HCs; C5-C12 HCs). Our own direct (DIR) method was used to confirm the collection efficiencies. Both methods yielded good results, but the CTI method showed low collection efficiency for some C2-C4 HCs. Measurement of individual species is needed with this method for accurate analysis of tailpipe emissions. Both the CTI method and the TCT method combined with the DIR method for determining C2-C4 HCs yielded nearly the same ozone specific reactivity values for the NMHC species analyzed.
Technical Paper

Research on Crankshaft System Behavior Based on Coupled Crankshaft-Block Analysis

1997-10-01
972922
Achieving a multi-cylinder engine with excellent noise/vibration character sties and low friction at the main bearings requires an optimal design not only for the crankshaft construction but also for the bearing support system of the cylinder block. To accomplish that, it is necessary to understand crankshaft system behavior and the bearing load distribution for each of the main bearings. Crankshaft system behavior has traditionally been evaluated experimentally because of the difficulty in performing calculations to predict resonance behavior over the entire engine speed range. A coupled crankshaft-block analysis method has been developed to calculate crankshaft system behavior by treating vibration and lubrication in a systematic manner. This method has the feature that the coupled behavior of the crankshaft and the cylinder block is analyzed by means of main bearing lubrication calculations. This paper presents the results obtained with this method.
Technical Paper

Development of a New Compound Fuel and Fluorescent Tracer Combination for Use with Laser Induced Fluorescence

1995-10-01
952465
Laser induced fluorescence (LIF) is a useful method for visualizing the distribution of the air-fuel ratio in the combustion chamber. The way this method is applied mainly depends on the fluorescent tracer used, such as biacetyl, toluene, various aldehydes, fluoranthene or diethylketone, among others. Gasoline strongly absorbs light in the UV region, for example, at the 248-nm wavelength of broadband KrF excimer laser radiation. Therefore, when using this type of laser, iso-octane is employed as the fuel because it is transparent to 248-nm UV light. However, since the distillation curves of iso-octane and gasoline are different, it can be expected that their vaporization characteristics in the intake port and cylinder would also be different. The aim of this study was to find a better fuel for use with LIF at a broadband wavelength of 248 nm. Three tasks were undertaken in this study.
Technical Paper

An Automatic Parameter Matching for Engine Fuel Injection Control

1992-02-01
920239
An automatic matching method for engine control parameters is described which can aid efficient development of new engine control systems. In a spark-ignition engine, fuel is fed to a cylinder in proportion to the air mass induced in the cylinder. Air flow meter characteristics and fuel injector characteristics govern fuel control. The control parameters in the electronic controller should be tuned to the physical characteristics of the air flow meter and the fuel injectors during driving. Conventional development of the engine control system requires a lot of experiments for control parameter matching. The new matching method utilizes the deviation of feedback coefficients for stoichiometric combustion. The feedback coefficient reflects errors in control parameters of the air flow meter and fuel injectors. The relationship between the feedback coefficients and control parameters has been derived to provide a way to tune control parameters to their physical characteristics.
Technical Paper

Improvement of Engine Sound Quality Through a New Flywheel System Flexiby Mounted to the Crankshaft

1990-02-01
900391
Engines that not only produce less noise but also provide good sound quality have been in increasing demand recently. Discomforting noise can sometimes be heard, however, during acceleration as the engine reaches higher levels of power and speed. This paper presents the results of a study into the bending vibration of the crankshaft-flywheel system, which clarify the mechanism producing discomforting noise during acceleration. Based on that study, a flexible flywheel has been developed which effectively reduces crankshaft bending vibration that is closely related to the frequency range of the discomforting noise. As a result, acceleration sound quality is greatly improved.
Technical Paper

Improvement of Lambda Control Based on an Exhaust Emission Simulation Model that Takes into Account Fuel Transportation in the Intake Manifold

1990-02-01
900612
This paper presents an improved exhaust emission simulation model that takes into account fuel transportation behavior in order to obtain more precise air-fuel ratio control, which is needed to meet stringent exhaust emission standards. This simulation model is based on experimental formulas for air and fuel behavior in the intake manifold, especially during transient engine operation. Fuel behavior, including the effect of wall flow on the air-fuel ratio, is obtained analytically. Predictions are then made of the exhaust emissions from a car operated under official driving schedules. The new simulation model is a useful tool in the design and development of fuel supply control systems. An outline of the new model is presented first along with a comparison of the calculated and experimental results. The air-fuel ratio control strategy derived with this model is then described.
Technical Paper

Effects of NOx and Unburned Gasoline on Low Temperature Sludge Formation in Engine Oil

1991-02-01
910747
It is generally known that NOx reacts with unburned gasoline, olefins in particular, to form sludge precursors. In this study, the authors investigated the process by which NOx and unburned gasoline mix into the engine oil and analyzed the mechanism whereby stop and go driving accelerates sludge formation. It has been found that NOx detected in the engine oil as nitrite ions mixes into the oil in the crankcase. The NOx concentration in the engine oil increases rapidly when the crankcase gas temperature is nearly equal to the dew point of the water vapor in the crankcase. Unburned gasoline is mainly absorbed into the oil through the oil film on the cylinder walls and the oil in the ring grooves. During low-temperature engine operation in stop-go driving (i.e., when the vehicle is stopped), NOx and unburned gasoline are absorbed into the engine oil and, in high-temperature engine operation (i.e., when the vehicle is moving), NOx and unburned gasoline are released from the oil.
Technical Paper

Development of Four Cylinder SR Engine

1990-09-01
901714
The SR engine is a new medium-size, all aluminum (cylinder block, head, rocker cover and oil pan) in-line 4-cylinder gasoline powerplant developed as a replacement for CA engine in Nissan's compact passenger cars. The development aim set for this engine was to achieve excellent power output and ample torque in the middle-and high-speed ranges, as well as a clear, linear engine sound up to the red zone. These performance targets have been achieved through the use of the 4-valve-per-cylinder DOHC design featuring a Y-shaped valve rocker arm system. This system allows a straight intake port for high power output and a narrow valve angle for a compact combustion chamber. The result is ample torque output as well as good fuel economy.
Technical Paper

Development of Lightweight Connecting Rod Based on Fatigue Resistance Analysis of Microalloyed Steel

1990-02-01
900454
Application of microalloyed steel to automobile parts is becoming increasingly common in Japan. However, fatigue properties of actual automotive forged parts with slight notches on their surface have not been fully clarified. In this work, the fatigue properties of microalloyed steel were studied using test specimens and also actual automotive parts. The results indicated that microalloyed steel with an optimal microstructure showed higher notch fatigue resistance than quenched-tempered steel. The improvement of material technology and the application of microalloyed steel have not only served to bring product costs down, but have paved the way for part weight reductions. Lightweight connecting rods for the newly developed Nissan engines have been produced, contributing to improved engine performance.
Technical Paper

A New Nissan 3.0-liter V-6 Twin-cam Twin-turbo Engine with Dual Intake and Exhaust Systems

1990-02-01
900649
As a new generation sports car engine to lead the field in the 1990s, a 3.0 liter, 60°V, type 6 cylinder, 4 cam, 24 valve engine (VG30DETT) has been developed to achieve the utmost in high performance levels and reliability. it has been mounted on the new model 300ZX and announced in the North America and Japanese markets. The VG30DETT engine is based on the previous VG30DE engine (the engine mounted on the former model 300ZX designed for the market in Japan). The main components, the major driving and the lubrication systems including such parts as the crank shaft,con-rod, cylinder block, piston, exhaust manifold, and oil pan of the VG30DE were thoroughly reviewed and revised. The VG30DETT engine is the result of redesigning the structure of the engine itself and its parts and components to assure durability under, high-level performance requirements.
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