Search Results

Spray guided DISI, a next-generation DISI system, is now under development as a gasoline engine which will contribute to improving fuel consumption. The authors have carried out a study to improve fuel consumption and exhaust emissions resulting from a spray guided DISI system with a center injection structure, which is being developed as a system with superior combustion stability. The primary issue for the center injection structure is to reduce changes in the fuel spray characteristics resulting from carbon deposits near the injector nozzle holes. The secondary issue for this structure is to improve the mixture formation.

Oxygen storage performance is modeled with the goal of optimizing the performance of three-way catalysts and developing an on-board catalyst degradation diagnosis (OBD) system. Oxygen storage performance is closely correlated with catalyst performance and degradation, and thus can serve as an excellent indicator for accessing the performance of catalysts[1, 2, 3, 4, 5 and 6]. In experiments using actual exhaust gas, it was found that the rate of oxygen storage and discharge under actual operating conditions exhibited sufficiently fast chemical reactions and were dependent on the supply rate of reactant species. We also found that the higher the catalyst temperature, the greater the oxygen storage capacity. These experimental results were modeled in a general control system development tool environment.

The lean NOx trap catalyst is a flow through device used in the aftertreatment of lean-burn engine exhaust gas. A simple model capable of simulating catalyst performance would be extremely useful in the development of a viable control system for switching back and forth between lean and rich operation in order to use a lean NOx trap catalyst. Such a model would have to be simple and yield calculated results quickly if it is to serve the ultimate objective of implementing a practical engine control unit for lean-burn engines. The model developed in this work adopts a datamap search approach featuring a simple NOx storage reaction mechanism. More specifically, the model accurately simulates NOx that is not adsorbed under lean conditions (NOx leak) and NOx that is not purified under rich conditions (NOx slip). By projecting the impact of ageing on catalyst performance, the model can also estimate diminished NOx emission capacity and fuel economy.

In-cylinder direct fuel injection technology is effective in improving fuel consumption and reducing emissions for gasoline engines. A number of systems based on this technology are currently being developed, and one such system, the wall guided DISI, has already been put to commercial use. As the development of the DISI engines pushes forward, spray guided DISI has been proposed as a new possibility which can offer further improvements. The authors of this paper recognize the advantages of spray guided DISI in terms of fuel consumption and emissions reduction, and have conducted research for the purpose of creating an injector that is optimized for spray guided combustion. A spray guided DISI engine requires a fuel injection system that is little affected by changes in airflow, pressure, and temperature inside the cylinder. This requirement is satisfied by the recently-developed multiple hole injector.

A Spray Guided DISI (Direct Injection Spark Ignition) is being proposed as a next-generation DISI and is expected to reduce the fuel consumption and the emissions than a Wall Guided DISI that is currently in the mainstream. With the aim of developing a Spray Guided DISI, the evaluation technologies for the spray behavior and the combustion characteristics in a single cylinder transparent engine, the measurement technologies for the mixture formation by LIEF (Laser Induced Exciplex Fluorescence) method and using a Fast Response FID (Flame Ionization Detector), and the analysis technologies for the spray behavior and the mixture formation with CFD (Computational Fluid Dynamics) technology were established. Based on these evaluation techniques, the behavior of spray and mixture formation by a Swirl Injector and a Multi Hole Injector were evaluated.

In a gasoline-direct injection (DI) engine, the formation of the air-fuel mixture, which is governed by the fuel spray geometry, the air motion, and the interaction among the spray, air motion, and wall, directly influences the engine performance. The fuel injected into the cylinder involves air and evaporates to form the air-fuel mixture. The mixture is forced near a spark plug by the spray penetration, air motion, and/or wall reflection. In this paper, we investigated the spray wall impingement and the interaction between the spray, air motion, and wall using an experiment and a numerical simulation. A high-pressure swirl injector simulation model was developed and applied to calculate the spray characteristics and spray wall impingement. The simulation results of the spray shapes under atmospheric and pressurized ambient pressure agreed with the experimental results.

In this paper, an application of variable structure systems (VSS)(1) to electromagnetic-clutch (EMC) control for starting vehicles is studied. Using a conventional open-loop controller, there is the case that changes in EMC dynamics lead to undesirable vehicle vibration though it may be rare. First, to overcome the above problem, we developed a control strategy based on VSS. The VSS control is robust with respect to changes in EMC dynamics. Second, we discussed the chattering problem of this controller in application to actual vehicle control. Finally, we confirmed the validity of the proposed control strategy and the appropriateness of the conditions for reduced chattering derived by simulation. The validity of this control strategy was also confirmed experimentally.

We have developed an effective secondary air-injection system that reduces harmful substances such as HC and CO. The secondary air in this system is heated to 300°C and injected into the exhaust pipe. Though the temperature of the secondary air is relatively low, it can activate a three way catalyst more rapidly than conventional secondary air injection systems. Thus, in our system (a “Heated-Air-Injection System”) is expected to be very effective in reducing harmful substances in the cold transient phase of the US Federal Test Procedure. For designing the system and analyzing its performance, we developed a simulation model including the design parameters of the system, such as flow rate of heated air, heater power, and so on. Besides these design parameters, the model takes into account of heat transfer from exhaust gas to exhaust pipe, gas-conversion reactions in a three way catalyst, and heat transfer efficiency of the electric heater.

A fuel control method to reduce the harmful exhaust gas from SI engines is proposed. As is well known, both the amplitude and the frequency of the limit cycle in a conventional air-fuel ratio control system are determined uniquely by parameters in the system. And this limits our making full use of the oxygen storage effect of TWC. A simple model of TWC reaction revealed the relationship between maximum conversion efficiency and both the amplitude and the frequency in a air fuel control system. It also revealed that TWC conversion efficiency attained to maximum levels when both the amplitude and the frequency of the limit cycle are selected so as to make full use of the oxygen storage effect of TWC. In order to achieve this, it is necessary to vary both the amplitude and the frequency arbitrarily.