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Technical Paper

Technologies for Reducing Cold-Start Emissions of V6 ULEVs

New technologies are needed to reduce cold-start emissions in order to meet the more stringent regulations that will go into effect in Europe (EC2000 or EC2005) and in California (ULEV), especially for larger engines such as 6- and 8-cylinder units. One new technology in this regard is the electrically heated catalyst (EHC). However, the use of EHCs alone is not sufficient to achieve the necessary reduction in emissions. This paper discusses techniques for effectively combining the elements of an EHC system, including the introduction of secondary air into the exhaust, improved control of the air/fuel ratio, and an electric power supply method for EHCs. It is shown that it is more effective to promote exothermic reactions in the exhaust manifold than at the EHC. A suitable method for this purpose is to introduce secondary air into the exhaust near the exhaust valves.
Technical Paper

Investigation of the Dilution Process for Measurement of Particulate Matter from Spark-Ignition Engines

Measurements of particulate matter (PM) from spark ignition (SI) engine exhaust using dilution tunnels will become more prevalent as emission standards are tightened. Hence, a study of the dilution process was undertaken in order to understand how various dilution related parameters affect the accuracy with which PM sizes and concentrations can be determined. A SI and a compression ignition (CI) engine were separately used to examine parameters of the dilution process; the present work discusses the results in the context of SI exhaust dilution. A Scanning Mobility Particle Sizer (SMPS) was used to measure the size distribution, number density, and volume fraction of PM. Temperature measurements in the exhaust pipe and dilution tunnel reveal the degree of mixing between exhaust and dilution air, the effect of flowrate on heat transfer from undiluted and diluted exhaust to the environment, and the minimum permissible dilution ratio for a maximum sample temperature of 52°C.
Technical Paper

Development of a High-Performance TiA1 Exhaust Valve

A new high-performance and lightweight TiA1 intermetallic compound exhaust valve has been developed. The TiA1 valve can improve power output and fuel economy by contributing higher engine speeds and a reduction in valvetrain friction. It was achieved by developing a Ti-33.5A1-0.5Si-1Nb-0.5Cr (mass%) intermetallic compound, a precision casting method for TiA1 that provides a low-cost, high-quality process, and a plasma carburizing technique for assuring good wear resistance on the valve stem end, stem and face.
Technical Paper

Effect of Engine Operating Parameters on Hydrocarbon Oxidation in the Exhaust Port and Runner of a Spark-Ignited Engine

The effect of engine operating parameters (speed, spark timing, and fuel-air equivalence ratio [Φ]) on hydrocarbon (HC) oxidation within the cylinder and exhaust system is examined using propane or isooctane fuel. Quench gas (CO2) is introduced at two locations in the exhaust system (exhaust valve or port exit) to stop the oxidation process. Increasing the speed from 1500 to 2500 RPM at MBT spark timing decreases the total, cylinder-exit HC emissions by ∼50% while oxidation in the exhaust system remains at 40% for both fuels. For propane fuel at 1500 rpm, increasing Φ from 0.9 (fuel lean) to 1.1 (fuel rich) reduces oxidation in the exhaust system from 42% to 26%; at 2500 RPM, exhaust system oxidation decreases from 40% to approximately 0% for Φ = 0.9 and 1.1, respectively. Retarded spark increases oxidation in the cylinder and exhaust system for both fuels. Decreases in total HC emissions are accompanied by increased olefinic content and atmospheric reactivity.
Technical Paper

The Development of a High Speed Steel Based Sintered Material for High Performance Exhaust Valve Seat Inserts

The demands on valve seat insert materials, in terms of providing greater wear-resistance at higher temperatures, enhanced machinability and using non-environmentally hazardous materials at a reasonably low cost have intensified in recent years. Due therefore to these strong demands in the market, research was made into the possibility of producing a new valve seat insert material. As a result a high speed steel based new improved material was developed, which satisfies the necessary required demands and the evaluation trials, using actual gasoline engine endurance tests, were found to be very successful.
Technical Paper

Analysis of Thermal Fatigue Resistance of Engine Exhaust Parts

The thermal fatigue resistance of engine exhaust system parts has conventionally been evaluated in thermal fatigue tests conducted with a restrained specimen. However, the test results have not always been consistent with data obtained in engine endurance tests. Two new evaluation methods have been developed to overcome this problem. One is a method of predicting thermal fatigue life on the basis of nonlinear elastic and plastic thermal analyses performed with a finite element model and the ABAQUS program. The other is a method of evaluating exhaust system parts using an exhaust system simulator. This paper describes the concepts underlying the two methods and their relative advantages.
Technical Paper

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

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.
Technical Paper

Study of the Generation mechanism for Abnormal Exhaust Noise

Based on experimental analysis, the generation mechanism of abnormal exhaust noise which is characterized by an intermittent high frequency aetallic sound, is clarified by bench testing of a FWD vehicle. The noise is caused by large amplitude pressure waves (finite amplitude waves) in the exhaust pipe. They are amplified due to interference between reflected waves and subsequent waves from the engine, and are finally transformed into shock waves in the propagation process along the exhaust pipe, resulting in abnormal exhaust noise. By theoretical analysis of finite amplitude waves, the wave profile in the propagation process and the transition distance to the shock wave can be solved analytically where the assumptions of mass, momentum, and energy conservation are valid, until the moment of shock wave formation. The transition distance is a key parameter in analyzing the growth and existence of shock waves.
Technical Paper

Time Resolved Measurements of Exhaust Composition and Flow Rate in a Wankel Engine

Measurements were made of exhaust histories of the following species: unburned hydrocarbons (HC), carbon monoxide, carbon dioxide, oxygen, and nitric oxide (NO). The measurements show that the exhaust flow can be divided into two distinct phases: a leading gas low in HC and high in NO followed by a trailing gas high in HC and low in NO. Calculations of time resolved equivalence ratio throughout the exhaust process show no evidence of a stratified combustion. The exhaust mass flow rate is time resolved by forcing the flow to be locally quasi-steady at an orifice placed in the exhaust pipe. The results with the quasi-steady assumption are shown to be consistent with the measurements. Predictions are made of time resolved mass flow rate which compare favorably to the experimental data base. The composition and flow histories provide sufficient information to calculate the time resolved flow rates of the individual species measured.
Technical Paper

A Portable Fast Response Air-Fuel Ratio Meter Using an Extended Range Oxygen Sensor

The method for measuring air-fuel ratio is generally based on analysis of the exhaust gas components and its calculations. A new instrument has been developed which uses this method, but it attaches an oxygen sensor for exhaust gas analysis to the exhaust pipe and calculates the air-fuel ratio directly from the sensor output using a microprocessor. The response time of this instrument is 100 milliseconds and because it does not require an exhaust gas sampling system its weight is only 2.5 kg. This paper describes the operation theory, construction and characteristics of this instrument, as well as the results of air-fuel ratio of measurements on engines and vehicles using this instrument in a transient state.
Technical Paper

New PM Valve Seat Insert Materials for High Performance Engines

Internal combustion engines experience severe valve train wear and the reduction of valve seat and seat insert wear has been a long-standing issue. In this work, worn valve seats and inserts were examined to obtain a fundamental understanding of the wear mechanisms and the results were applied in developing new valve seat insert materials. The new exhaust valve insert material for gasoline engines is a sintered alloy steel containing Co-base hard particles, with lead infiltrated only for inserts used in unleaded gasoline engines. The new intake valve insert material for gasoline engines is a high-Mo sintered steel, obtained through transient liquid phase sintering and with copper precipitated uniformly. This material can be used for both leaded and unleaded gasoline engines. Valve and valve seat insert wear has long been an issue of concern to engine designers and manufacturers.
Technical Paper

Modeling the Spark Ignition Engine Warm-Up Process to Predict Component Temperatures and Hydrocarbon Emissions

In order to understand better the operation of spark-ignition engines during the warm-up period, a computer model had been developed which simulates the thermal processes of the engine. This model is based on lumped thermal capacitance methods for the major engine components, as well as the exhaust system. Coolant and oil flows, and their respective heat transfer rates are modeled, as well as friction heat generation relations. Piston-liner heat transfer is calculated based on a thermal resistance method, which includes the effects of piston and ring material and design, oil film thickness, and piston-liner crevice. Piston/liner crevice changes are calculated based on thermal expansion rates and are used in conjunction with a crevice-region unburned hydrocarbon model to predict the contribution to emissions from this source.
Technical Paper

A Unique Dual-Mode Muffler

The techniques harmonizing the contradiction which consists of exhaust noise reduction and engine power increase, have been required for the exhaust muffler. This techniques rapidly improved by means of the clarification due to the acoustic theories and the flow analyses. Recently, according to the passenger car tendency toward high grade and high performance, demands for low noise and high power exhaust systems are increasing year by year. The “Dual Mode Muffler” system (abbreviated, below, DMM) mounted on Nissan Cedric, Grolia and Cima series, installed in 1987, is achieved the consistent of the quietness and the engine power performance. This system is the first control type exhaust system for the 4 wheel car. On previous paper, the analyses of acoustic characteristics on DMM were mainly shown. The analyses of exhaust pressure characteristics are also an important theory along with the acoustic in the development of the exhaust system.
Technical Paper

Lab Study of Urea Deposit Formation and Chemical Transformation Process of Diesel Aftertreatment System

Diesel exhaust fluid, DEF, (32.5 wt.% urea aqueous solution) is widely used as the NH3 source for selective catalytic reduction (SCR) of NOx in diesel aftertreatment systems. The transformation of sprayed liquid phase DEF droplets to gas phase NH3 is a complex physical and chemical process. Briefly, it experiences water vaporization, urea thermolysis/decomposition and hydrolysis. Depending on the DEF doser, decomposition reaction tube (DRT) design and operating conditions, incomplete decomposition of injected urea could lead to solid urea deposit formation in the diesel aftertreatment system. The formed deposits could lead to engine back pressure increase and DeNOx performance deterioration etc. The formed urea deposits could be further transformed to chemically more stable substances upon exposure to hot exhaust gas, therefore it is critical to understand this transformation process.
Technical Paper

Aerodynamics Development for a New EV Hatchback Considering Crosswind Sensitivity

An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model.
Technical Paper


THIS paper reports the latest investigation of the relative merits of loop scavenging versus through scavenging. The authors hope that the conditions of the work permitted an objective evaluation of the two types of engines. The results of the study may be summarized as follows: 1. With symmetrical timing, neither cylinder shows significant advantage in trapping efficiency. 2. With symmetrical timing, the best ratio of exhaust-port to inlet-port effective area seems to be about 0.6. 3. Unsymmetrical timing is an effective method of improving trapping efficiency. 4. The value of net indicated fuel economy shows no significant difference between the two cylinders. The authors point out that because the areas were equal it is unlikely that the optimum port design of each type was used in comparing the cylinders. If optimum porting had been used, the two types might have shown more difference.
Technical Paper

Small Engine - Concept Emission Vehicles

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.
Technical Paper

Time-Resolved Measurements of Hydrocarbon Mass Flowrate in the Exhaust of a Spark-Ignition Engine

Experimental measurements of the instantaneous exhaust gas temperature, mass flowrate, and hydrocarbon concentration have been made in the exhaust of a single cylinder research engine. The temperature measurements were accomplished using an infrared optical technique and observing the radiation of the exhaust gas at the 4.4 μm band of CO2. Instantaneous exhaust gas mass flowrates were monitored by placing a restriction in the exhaust manifold and measuring the instantaneous pressures across the restriction. Time-resolved hydrocarbon concentrations were measured using a fast-acting sampling valve with an open time of 2 ms. From these measurements, the hydrocarbon mass flowrate is calculated as a function of crank angle.
Technical Paper

Economical Matching of the Thermal Reactor to Small Engine-Low Emission Concept Vehicles

The Inter-Industry Emission Control (IIEC) Program included the thermal reactor as one of the effective ways of oxidizing HC and CO in the exhaust system. However, this was accompanied by very substantial fuel economy penalties, especially in the case of small engine-low emission concept vehicles. Starting with a new concept aimed at obtaining the HC/CO oxidizing trigger temperature in the thermal reactor by modifying engine settings, the authors arrived at an economical technique of matching the thermal reactor to the engine.
Technical Paper

Modeling Study of Metal Fiber Diesel Particulate Filter Performance

Sintered metal fiber (SMF) diesel particulate filters (DPF) has more than one order of magnitude lower pressure drop compared to a granular or reaction-born DPF of the same (clean) filtration efficiency. To better understand the filtration process and optimize the filter performance, metal fiber filter models are developed in this study. The major previous theoretical models for clean fibrous filter are summarized and compared with experimental data. Furthermore, a metal fiber DPF soot loading model, using similar concept developed in high efficiency particulate air (HEPA) filter modeling, is built to simulate filter soot loading performance. Compared with experimental results, the soot loading model has relatively good predictions of filter pressure drop and filtration efficiency.