Search Results

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.

The goal of this research is to determine the feasibility of a catalytic compression-ignition engine running on aqueous ethanol fuel. A naturally aspirated, three-cylinder, direct-injection diesel engine manufactured by Yanmar has been modified to operate as a homogeneous-charge, compression-ignition engine. This involved removing the fuel injectors, replacing them with catalytic elements located inside a small pre-chamber, and installing a pulse width modulated fuel injection system. The fuel is 35% water and 65% ethanol by volume. The catalytic igniters allow the engine to operate continuously at various load levels corresponding to a broad range of air/fuel ratios. To adjust ignition timing and monitor in-cylinder combustion, the engine has been instrumented with a piezoelectric pressure transducer and a crankshaft encoder. Pressure traces are quite repeatable from cycle to cycle and resemble combustion patterns in typical Otto cycle engines.

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads are experimentally investigated using a four-stroke, four-cylinder, indirect injection, water-cooled marine diesel engine operating at two engine speeds. The aim of this study is to develop the EGR control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions. And a novel diesel soot-removal device with a cylinder-type scrubber for the experiment system is specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. It is found that NOx emissions decrease markedly, especially at higher loads, while soot emissions increase owing to the drop of intake and exhaust oxygen concentrations, and the rise of equivalence ratio as the EGR rate is elevated.

Vehicle structural resonance modes are classified generally into rigid and flexible (non–rigid) body modes. During motorcycle testing and development for design validation, it is often useful to understand these modes of vibration. Understanding rigid and flexible body modes helps to improve the ride and handling performance. Understanding the flexible body modes helps to isolate noise, vibration, and harshness (NVH) problems. It can also help to find the root causes of structural durability failures. Flexible body modes can also be annoying or unsafe to the operator. For example, handlebar vibrations may cause numbness in the hands or arms. Flexible body modes also can contribute to motorcycle dynamic instability modes such as the weave instability. Similarly, the rider's ability to see approaching traffic from the rear may be reduced if mirrors are vibrating due to a flexible body mode in the handlebars, frame, or front fork.

When a motorcycle runs with hands free riding, the change of the handle deflection angle is interlocked with the vehicle body (frame) bank angle, which is operated by the rider lean angle and caused by the disturbance of road surface. In this report, the motion of the rider who maintains the upright stability of a motorcycle in hands free and hold grips running at low speeds was studied from the experiment with measuring the vehicle frame bank angle, the rider's lean angle and the handle deflection angle, and the rider's feeling evaluation concerning the stability.

The Emission Regulations for Motorcycles in Japan was put into effect in October 1998 with the goal of reducing the total hydrocarbon emissions from motorcycles in the country to around 50% of the present amount. These regulations initiated a need to develop emission-converting catalysts, having the three characteristics written below, for two-stroke engines that historically have produced more hydrocarbons than four-stroke engines: 1 High performance of hydrocarbon conversion 2 High light-off performance 3 High thermal stability under high temperature Among a number of catalytic adjustment methods, the loading method of precious metals and the washcoat preparing method were modified to realize mass production of high-performance, low-cost catalysts.

The development history of a 30cc 2-stroke engine power unit in the covered rear wheel for retrofit into standard bicycle chassis. The rear wheel acts as cooling fan for the air cooled long stroke engine with catalyst exhaust system, autochoke carburetor, autolube oil pump, electric start and inertia start, single speed automatic transmission and 7 speed hub final drive. The space in the rear wheel contains intake air filter, exhaust system, fuel tank, oil tank and engine with drive train, the complete engine being only 94mm wide. The complete covered power unit is nearly undetectable as the rear wheel covers resemble road racing bicycles. There is very low stationary and pass-by noise (64 db[A]), no exhaust gas opacity or smell, very low vibration level and very good fuel economy up to 133 km/l.

ATAC (Active Thermo-Atmosphere Combustion) is autoignition combustion in two stroke engines, which occurs by diluting trapped Fuel-Air mixture with residual gas to maintain a high temperature at low load operation. In this study, two-stroke ATAC engine testing was carried out to obtain fundamental knowledge for controlling the autoignition and combustion characteristics in this premixed charge compression-ignition combustion engine. The influences of delivery ratio, equivalence ratio and enginespeed (i.e. compression speed) on autoignition timing, autoignition temperature and combustion duration were investigated. It was found that the ATAC autoignition temperature and combustion duration did not depend on the delivery ratio and equivalence ratio, but were determined by the individual fuel characteristics. Increasing the compression speed reduced the ATAC autoignition temperature a little.

In two-stroke S.I. engines, direct fuel injection prevents fuel short-circuiting from the exhaust port, however it does not solve per se combustion problems at light loads due to excessive ratio of residual-to-fresh gas. These problems can be solved by ATAC (Active Thermo Atmosphere Combustion), since residual-gas thermal energy is used to prime the combustion of fresh gas. Experimental results of a small two-stroke S.I. engine with medium-pressure air-assisted fuel injection, operating on ATAC at light loads are shown and prove the possibility to combine the two solutions.

A hybrid system combining a 4-stroke, 50cc-gasoline-engine with an electric motor was developed, and the maximum vehicle speed achieved by the electric motor is 30 km/h. Either an electric motor or engine is selected as the power source according to the running condition, and it is switched automatically. A parallel hybrid system, the Modulated Hybrid System (MHS), was adopted. Therefore, the energy source of the electric motor can be charged by an external or an internal power source. The switch mechanism of the driving power source is simple by using a one-way-clutch. The driving force, the vehicle speed, and the remaining battery energy are the parameters for switching control of the driving power sources. In order to achieve smooth switching and quick responses, the electric motor output is controlled by the feedback of the driving torque.