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An attempt to reduce the HC emission of a two-stroke engine was carried out. A simple homogeneous charge combustion created with a Direct Fuel Injection (DFI) system was applied to a Personal Water Craft (PWC) engine. 1/4 HC emission of the base carbureted engine was obtained in International Council of Marine Industry Association (ICOMIA) driving mode due to the exclusion of fuel short-circuiting. Then stratified charge combustion was introduced. A numerical simulation of air and spray motion was performed and mixture formation was optimized. The low load misfiring was completely overcome and finally, less than 1/8 HC emission was achieved.

The IAPAC Direct fuel Injection (DI) system, developed by IFP, has already well proven its capability to reduce pollutants emissions and fuel consumption of 2-stroke engines. This crankcase Compressed Air Assisted Fuel Injection Process allowing the introduction of the fuel separately from the scavenging air, minimizes the fuel short-circuiting. In earlier works, results of the implementation of the IAPAC system on cylinder displacement from 125 cc to 400 cc have been presented in various papers. These first prototypes were all using a camshaft to drive the IAPAC DI poppet valve, which was considered as a limitation for applying this system to small displacement 2-stroke engines. The new SCIP™ system is no more using a camshaft neither driveshaft, or any electric power supply to drive the DI air assisted injection valve.

An experimental investigation was carried out to highlight the impact of different catalytic exhaust systems of a typical European two-stroke engine for small scooters on exhaust emissions and on engine performances. In particular different chemical compositions of the active coating materials and different precious metal loads were tested, and several geometries of the monolith in the exhaust system were analyzed. The influence of different carburetor settings on the efficiency of the catalyst and on engine performance was also evaluated. Finally, durability tests were performed, by monitoring the efficiency of the catalyst during a 12000 km aging test.

A project was conducted by Southwest Research Institute on behalf of the California Air Resources Board and the South Coast Air Quality Management District to demonstrate the technical feasibility of utilizing closed-loop three-way catalyst technology in off-road equipment applications. Five representative engines were selected, and baseline emission-tested using both gasoline and LPG. Emission reduction systems, employing three-way catalyst technology with electronic fuel control, were designed and installed on two of the engines. The engines were then installed in a fork lift and a pump system, and limited durability testing was performed. Results showed that low emission levels, easily meeting CARB's newly adopted large spark-ignited engine emission standards, could be achieved.

The motorcycle Industry is one of the advantageous industries with developing potentialities in China. Depending on chassis dynamometer test results from more than 100 motorcycles a motorcycle emission data–base was set up. By using this motorcycle emission data–base the status overview of Chinese motorcycle emissions is given. Unleaded gasoline will be used throughout china in 2000, which creates essential prerequisite for application of catalytic converter technique. Catalytic control of motorcycle emissions requires that the catalytic converter must be carefully integrated into the exhaust system. Optimal matching between catalytic converter position and engine performance was achieved through engine tests. Evaluation of catalytic converters was made through chassis dynamometer tests. Emission results from motorcycle with the optimum catalytic converter can meet the present Europe motorcycle limitations (The so called motorcycle EURO–1 were taken into force in June 17th 1999[1])

The rocker arm has a function to lead the cam shaft rotation to the valve operation. There are cases when damages are caused due to abnormal wear at the sliding part, causing certain problems. Authors classified the wear phenomenon, and realized a systematic analysis on the possible cause of the damage. As a result, it was revealed that the damage was of two types, and to prevent the hard wear, it is effective to apply shot peening before plating. The prototype rocker arm was test under various lubricating conditions, thus actually confirming that the occurrence of wear was largely reduced.

The basic Semi-Direct-Injection System (SDIS) which is already in production for PWC and applied to small 2-wheeler engines features a low-pressure fuel injection system injecting through the rear scavenge port window in the cylinder symmetry plane onto the piston crown. The patented new SDIS Mk.II System [1] injects through an (additional) scavenge port window that is positioned above the scavenge ports and is controlled by a window in the piston skirt. This new arrangement allows longer injection duration and also other injector positions and directions. A CFD simulation by AVL's FIRE-CFD-code with moving piston and exhaust gas dynamics compares the different injector positions and directions for WOT and rated speed and for a part throttle low speed case. The SDIS Mk.II injection system consists of mass-produced automotive parts thus giving a low cost approach for present 2-stroke engines requiring only moderate engine modifications.

In general, welding of high-pressure die casting (DC) parts has been difficult due to gases trapped in the castings. This is a result of the high-speed turbulent flow condition of the DC process. These gases are liberated during welding and produce porosity in the weld joint. The Author had found the range where an enough welding quality was obtained without great drop in castability to the middle of the laminar flow and turbulent flow. This range has been defined as the transition zone. Moreover high strength Al-Mg-Ni alloy was developed by non-heat-treatment. The Transition Flow Filling Method(TFFM) has been developed, that can not only reduce the amount of trapped gases but also is applicable to standard high pressure die casting equipment. With this method, high quality DC parts can be produced that are weldable, strong and have high toughness.

This paper presents the results of an exploratory study examining the production of particulate matter (PM) by 2-wheel vehicles and the impact of catalytic aftertreatment on these emissions. Information is presented demonstrating the efficacy of catalytic aftertreatment for significantly reducing not only hydrocarbons (HC) and carbon monoxide (CO), but also PM emissions from motorcycles equipped with small 2-stroke engines. The generation of PM by 5 test vehicles during realistic driving conditions is discussed and the impact of catalyst performance characteristics on the reduction of these releases is examined. Vehicle based test data, obtained with a mini-dilution tunnel, clearly demonstrates the benefits to the environment achievable through the use of catalytic aftertreatment.

The use of catalytic aftertreatment to reduce harmful gases in the exhaust streams of 2-wheel vehicles powered by small engines is becoming widespread as increasingly restrictive emissions standards are enacted. The primary exhaust gas pollutants are carbon monoxide (CO) and hydrocarbons (HC) for vehicles equipped with 2-stroke engines and CO for those using 4-stroke power plants. Because the exhaust streams of these small engines also contain significant concentrations of oxygen, catalytic aftertreatment is a very effective approach for oxidizing these contaminants to carbon dioxide and water. In order to assure the maximum long term benefits of catalytic aftertreatment, it is necessary to understand not only the factors responsible for high initial activity, but also the mechanisms by which a catalyst's performance is negatively impacted.

The first part of the paper gives an overview of the environmental conditions with which a future two stroke powered vehicle must comply and explains the reasons for which a direct gasoline injection into the combustion chamber offers a potential solution. The paper continues with a description of the fuel/air mixture injection used in the F.A.S.T. concept and gives a detailed overview of the layout of the 125 cc engine to which it is applied. The structure of its electronic engine management system, mandatory for the necessary control precision, is presented. Hereafter is made a short introduction to the visualization and numerical computation tools used for the engine design optimization. The paper concludes with a detailed presentation and discussion of the experimental results obtained with the engine operated, either in steady state and transient conditions on an engine test rig, and mounted in a classic small dimension two-wheel vehicle submitted to road tests.

In order to see the effect of injection timing and directions on the performance of a DI gas engine, an experimental engine was prepared, and firing tests were carried out. Also a laser induced fluorescence method was used to see in-cylinder fuel distribution. As the result, following conclusions were obtained. 1) NO2 could be used as a tracer substance to visualize in-cylinder gaseous fuel distribution. 2) Injection timing had large influence on the fuel distribution and the performance of the DI engine. 3) In-cylinder fuel distribution and operation stability of the DI engine was also affected by injection directions.

The influence of injection timing on the performance of a manifold injection gas engine was investigated with the results of firing tests. Also the in-cylinder fuel distribution of the engine was measured by a tracer LIF method and used to understand the results of the firing tests. These results showed that the in-cylinder fuel distribution of the engine in the direction of a cylinder axis was changed by the variations of injection timing.

The development and preliminary results of a low cost electronic fuel injection (EFI) system for one and two cylinder 4-cycle gasoline engines is described. The feasibility of reducing system cost by minimizing the number of sensors is explored. The objective is to use only the following signals to determine the operational state of the engine: Magneto Voltage Signal (Speed/Load) Engine Temperature Lambda Exhaust Gas Oxygen (Optional) Another objective in the on-going development is to maintain the performance enhancements that EFI offers over carbureted engines: cold starting, fuel economy, and reduced emissions. Special focus is applied to the creation and analysis of a load signal that is related to the torque produced by the engine. Constrained by certain conditions, the load signal is related to the air charge entering the cylinder. The load signal, along with the engine speed signal, provides a basis for a fueling look-up table.

The application of low cost stratified scavenging systems to the two-stroke engine is described. Previous results from multi-stream systems tested at The Queen's University of Belfast are reviewed and results from single- and double-entry air-head engines are presented. The most promising results relate to a 270cm3 single cylinder cross-scavenged engine with the single-entry air-head system. Effective trapping was obtained by injecting fuel into the crankcase and inducing air through an inlet at the top of the transfer ducts. The results showed significant improvements over the standard homogeneous scavenged engine. The brake specific fuel consumption was reduced by up to 22% and the brake specific hydrocarbons by up to 55%.

This paper describes a stratified scavenging system of two–stroke cycle engine, developed to reduce HC (hydrocarbon) emission caused by short–circuiting mixture at scavenging process. The fact, the maximum short–circuiting of fuel–air mixture occurs at the timing soon after the scavenging port open, led us to the idea of stratified scavenging, that is, first stage of scavenging by air without fuel, then second stage by air–fuel mixture. The stratified scavenging system consists of long passages from crankcase to scavenging ports, and the supplemental air intake system directly to the scavenging port. The newly developed stratified scavenging two–stroke cycle engine cuts HC emission to about 1/4 of conventional two–stroke, and can meet the CARB Tier 2 emission regulation.

Stratified scavenging has been applied to two-stroke engines to improve fuel consumption and reduce exhaust emissions. To evaluation how this is achieved a stratified scavenging process was simulated using a three-gas single-cycle scavenging apparatus. The experiment simulated the fuel stream entering the rear transfer port of a five port cylinder and air streams entering the remaining ports. The scavenging efficiency and fuel trapping are calculated after the cycle by examining the cylinder contents. The design of the apparatus is particularly suited to investigating cylinder design changes during the prototype stage of engine development. A simulation of the stratified scavenging experiment using the Computational Fluid dynamics (CFD) code VECTIS, showed good correlation with measured results. The simulation provides a real insight into the cylinder flow behaviour of the separate fuel and air streams entering the cylinder.

The advantages of high power to density ratio and low manufacturing costs of a two-stroke engine compared to a four-stroke unit make it currently the most widely used engine type for 50cc displacement 2-wheelers. This dominance is threatened by increasingly severe exhaust emissions legislation, forcing manufactures to develop their two-stroke engines to comply with the legislation. This paper describes a simple solution to reduce these harmful emissions in a cost effective manner, for a scooter application. The method of stratified scavenging is achieved by delivering the fuel into the rear transfer passage from a remote mechanical fuel metering device, operated by intake manifold pressure. Air only is delivered into the cylinder from the remaining transfer passages which are directed towards the rear transfer port, thus impeding the fuel from reaching the exhaust during the scavenging process.

A waterjet propulsor has come to be used more popularly for high speed watercrafts such as personal watercrafts. The most difficult problem for designing the waterjet system is that a tradeoff is required to properly determine the best parameters for the waterjet pump and subsequently the best overall propulsion system. This paper presents the design method and performance improvement of the waterjet propulsor used for personal watercrafts. The authors have clarified the performance of the individual component in the waterjet propulsor and improved the component efficiency empirically, and established the method to estimate the thrust and power characteristics of the propulsor on board from the component test results and other design parameters, which enables the optimization of the waterjet system.

The uniform lean gasoline-air mixture was provided to the diesel engine and was ignited by the direct diesel fuel injection. In this study, the internal EGR is add to this ignition method in order to activate the fuel in the mixture before the ignition. It is confirmed that the lean mixture of air-fuel ratio between 150 and 40 could be ignited and burned by this ignition method when the back pressure of 80 [kPa] is added, and the burning period is shorted by internal EGR. However, as the back pressure increases, NOx concentration is increased by the high temperature residual gas.