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Two-stroke engine keep-clean data is presented to demonstrate the deposit removal capabilities of a premium fuel additive. In this testing, the fuel additive was added as a top-treatment to a 50:1 blended fuel-oil mixture. Engine testing was conducted on an EchoTM SRM-265 (25.4 cc) string trimmer run under a standardized test cycle. Test measurements included piston deposits, ring deposits, and exhaust port blockage. In addition, a more complete data set was analyzed and several variables were investigated including: different base gasoline fuels, ethanol level (E0 and E10), additive dose (none, low, and high), and fuel stabilizer dose (none and high). Post-test inspection of engine parts using fuel additives showed a high level of clean surfaces, which maintained the engine at its original performance.

High unburned hydrocarbon emissions and poor fuel consumption arise in a carburetted two-stroke engine because of its scavenging process. Time resolved hydrocarbon concentration at the exhaust port has shown a definite trend in concentration of unburned hydrocarbon with respect to crank angle. This paper discusses an exhaust gas recirculation system designed to trap fraction of the exhaust gas that is rich in short circuited fresh charge. In this design, the differential pressure between the crankcase and the exit at the exhaust port is communicated with each other at the appropriate time through passages in the piston and the cylinder block. The design is thus capable of selectively trapping and recirculating fraction of the exhaust gas rich in short circuited fresh charge back into the cylinder for combustion.

This paper deals with the investigation, redesign, and development of a 2-stroke cycle internal combustion engine whereby a reduced oil-to-fuel ratio can be obtained with use of a reasonable selection of fuels and lubricants. This objective has been accomplished by mechanical redesign of the fuel induction system, combustion chamber, and cylinder casting. The redesign has resulted in improved overall engine performance characteristics with retention of long life characteristics, while at the same time enhancing development of a further reduction in the fuel-oil ratio.

This is an assessment of current two-stroke automotive engine technology, implementation policy, vision, goals, and engine development and commercialization strategy. It includes a historical review of key two-stroke Otto cycle engine developments, a summary of the specifications for the new: Suburu Super 2-stroke, Toyota S-2 gasoline engine, Orbital two-stroke, General Motors GMCDS2 two-stroke engine and Industrial Technology Research Institute (ITRI) two-stroke engine test technology in Taiwan. Although two-stroke engine technology has been under development since the end of the 19th century, currently the only mass produced vehicles powered by two-stroke cycle engines are the Trabant and Wartburg, with 594 cc two cylinder and 993 cc three cylinder engines, respectively, essentially unchanged in cylinder configuration and porting since 1931.

This is an assessment of current two-stroke automotive engine technology, implementation policy, vision, goals, and engine development and commercialization strategy. It includes a historical review of key two-stroke Otto cycle and Diesel cycle engine developments, a summary of the specifica-ions for the new: Toyota S-2 gasoline and S-2 Diesel engines, Suburu Super 2-stroke, Orbital two-stroke engine series, and Industrial Technology Research Institute (ITRI) two-stroke technology in Taiwan. Although two-stroke engine technology has been under development since the end of the 19th century, currently the only mass produced vehicles powered by two-stroke cycle engines are the Trabant and Wartburg, with 594 cc two cylinder and 993 cc three cylinder engines, respectively, essentially unchanged in cylinder configuration and porting since 1931.

COST, WEIGTH AND POWER OUTPUT, render it unlikely that 2-stroke engines for chain saws and related applications can be superseded by any other propulsion system in the near future. In order to remain competitive in the future, 2-stroke engines - and thus cylinders and pistons - must be designed that they are able to achieve the largest possible power output from the lowest possible overall volume, with an adequate operational reliability and at competitive prices. Special attention must be paid to exhaust gas emission and noise, particularly in view of future legislation. This paper reports on new results obtained when increasing the power output of 2-stroke chain saw engines, and describes the prospects for an increase in operational reliability.

The behaviour of fluid flow in piston-ported crankcase-scavenged two-stroke engines is evaluated. Two complementary models of charge renovation are developed: The first model, named the “geometric submodel”, relates the equivalency bases between real designs and sketches of the ducts for the flowing fluid. The other one, named the “analytic submodel”, employs the unidimensional flow theory to study the characteristics variables in the reference sections of the ducts. An instantaneous Admission Coefficient concept is established and plotted versus crantangle. A Global Admission Coefficient is calculated and its variation versus rpm is obtained. The models are used to determinate the optimum engine geometry for a given Admission Coefficient.

The Indian emissions legislation introduced in April 2000 for 2-wheelers has resulted in the widespread use of exhaust catalysts on 2-stroke powered vehicles. There has been debate over the effectiveness of this emissions solution compared to alternatives such as the 4-stroke engine. This paper describes a durability programme using 2-stroke scooters fitted with exhaust catalysts and driven on Indian roads. The emissions were monitored at regular intervals over 30,000 km. These vehicles were found to comply with the India 2000 emissions limits throughout the 30,000 km. The emissions performance of these catalysts were then compared over the Indian Driving Cycle (IDC) on a common vehicle, and by using a newly developed light-off test, to engine bench aged catalysts. All the catalysts were subsequently analysed for thermal deterioration and for concentration of chemical impurities in order to compare the chemical and physical effects of the different types of ageing.

Direct fuel injection is becoming mandatory for two-stroke S.I. engines, since it allows using only air in the scavenging process, preventing fuel loss from the exhaust port. However, also combustion irregularity at light loads is a problem of these engines, due to excessive presence of residual gas in the charge. For its solution, additional strategies must be adopted. The two most suitable ones are charge stratification and ATAC (Active Thermo Atmosphere Combustion), which makes use of residual gas energy to ignite fresh gas, turning the effect of residual gas from negative to positive. In previous papers, the possibility of combining ATAC with different injection systems was proved. This paper provides further insight on ATAC combined with liquid high-pressure direct injection and shows the studies and the first experimental results relative to charge stratification.

Among all the reciprocating internal combustion engines, gasoline two-strokes can reach the highest specific power, making this technology a natural enabler of downsizing and/or down-speeding. In addition, multi-cylinder 2-stroke engines may be an ideal match for electrical superchargers, providing very efficient power units. The paper explores through CFD-1d simulations and empirical hypotheses the potential of a 3-cylinder, 1.0 liter, GDI 2-stroke turbocharged engine featuring a patented rotary valve for the optimization of the scavenging process, the latter being of the loop type (piston-controlled ports). The lubrication system is the same of a 4-stroke engine (no crankcase pumps). The supercharging system is made up of a turbocharger and an electric compressor, serially connected. The power of the electric compressor is limited to 2 kW, in order to comply with standard automotive 12 V electric systems.

The current position of the two-stroke cycle aircraft engine is described with respect to competitive type powerplants, including a brief historical background and information on some of the latest designs. The two-cycle case is substantiated with arguments and data showing why it should still be considered for the lower power ranges.

A mono-cylinder engine was built, because of its costs and the semplicity of designing, as flexible prototype. A scavenging system with four ports, two by two simmetrical, was chosen to respect the modern theory of scavenging optimization. The scavenging flow was supplied by a carter-pump; it has been used as first experimental solution. The prototype has been entirely realised and the following experimental measurements have been carried out: the pressure in combustion chamber, in carter pump, in pipes and injection system, as well as the fundamental parameters of engine functioning.

A model engine with disintegrated working cycle was build. Its operation is not autonomous; compression of the working air is performed separately outside the engine by the compressed-air line supply. Pre-compressed charge together with the injected fuel is introduced in the combustion chamber. The model engine makes possible to determine indicated performance characteristics and its emission capability. Effective measured engine characteristics are of course not comparable with those obtained by an practical engine. The model presented is a two-stroke cycle engine. Exhaust emission picture of the presented engine is comparable with the emission of a modern four-stroke engine.

Laser excitation wavelengths for two-line planar laser-induced fluorescence (PLIF) of 3-pentanone have been optimized for simultaneous imaging of temperature and composition under engine-relevant conditions. Validation of the diagnostic was performed in a motored optical IC engine seeded homogeneously with 3-pentanone. PLIF measurements of the uniform mixture during the compression stroke were used to measure the average temperature and to access the random uncertainty in the measurements. To determine the accuracy of the temperature measurements, experimental average temperatures were compared to values computed assuming isentropic compression and to the output of a tuned 1-D engine simulation. The comparison indicated that the absolute accuracy of the temperature measurements is better than ±5%. Probability density functions (PDFs) calculated from the single-shot images were used to estimate the precision of the measurements.

Numerous turbofan power-loss events have occurred in high altitude locations in the presence of ice crystals. It is theorized that ice crystals enter the engine core, partially melt in the compressor and then accrete onto stator blade surfaces. This may lead to engine rollback, or shed induced blade damage, surge and/or flameout. The first generation of ice crystal icing predictive models use a single flow field where there is no accretion to calculate particle trajectories and accretion growth rates. Recent work completed at the University of Oxford has created an algorithm to automatically detect the edge of accretion from experimental video data. Using these accretion profiles, numerical simulations were carried out at discrete points in time using a manual meshing process.

The aim of this article is to show the effects of the omission of the active cycles in the one-cylinder two-stroke engine on the vibration characteristics of the two-wheeled vehicles. The vibration characteristics are expressed by the accelerations of the selected points of the basic structure of the vehicle, through which the rider is in direct contact with. An attempt is described showing how to achieve this aim with the aid of a special mathematical model of the motorcycle plane vibrations, excited by the unbalanced mass forces, mass moments and other forces and moments which accompany the motion of the motorcycle over a horizontal straight road. Given are the results of the laboratory conduced research on the possibilities of the omission of the active cycles in the small two-stroke engines, which can be achieved by an electronically controlled fuel injection.

In this paper, a new two-zone flamelet model is suggested. In the combustion model, each cell is divided by the flame front to two zones: unburned zone and burned zone. The unburned zone consists of air, fuel vapour and residual gases, whilst the burned zone contains combustion products. The unburned zone is further divided into two regions: segregate region and fully mixed region. The combustion is decoupled as two sequential events: mixing and burning. The turbulent mixing is governed by the large eddy structure, taking the effect of fuel drop spacing into consideration. The turbulent burning rate is further decomposed into three terms: laminar burning velocity for combustion chemistry, turbulence enhanced burning rate and flame strain factor for flame quenching. The turbulent burning rate is evaluated based on fractal geometry and basic dimensional analysis of turbulent flame.

Typically, the combustion analysis for S.I. engines is limited to the determination of the apparent heat release from in-cylinder pressure measurements, effectively using a single zone approach with constant properties determined at some average temperature. In this paper, we follow an approach consistent with the engine modeling approach (i.e., reverse modeling) to extract heat release rate from combustion pressure data. The experimental data used here solely consists of quantities measured in a typical engine dynamometer tests, namely the crank-angle resolved cylinder pressure, as well as global measurements of the A/F ratio, engine speed, load, EGR, air mass flow rate and temperature and exhaust emissions. We then perform a two-zone, crank-angle resolved analysis of the pressure data using variable composition and properties.

A quasi-dimensional, two-zone combustion model was developed for calculating the formation of nitrogen oxides in direct-injection diesel engines. The model was verified by means of measurements obtained with two direct-injection, four-stroke, single-cylinder diesel engines, one of which had a total displacement of 3.96 liters and the other 5.95 liters. The combustion model was used to analyze the thermal dynamics and reaction kinetics of the procedures involved in well-known methods for the engine-internal minimization of nitrogen oxides.

In this paper, we present a two-zone thermodynamic model that allows us to predict the time dependent in-cylinder conditions (P, T) in a high-speed medium BMEP engine fueled with different gas compositions. The details of this model rely on the observation that the measured combustion phasing correlates strongly with the (computed) laminar burning velocity under the conditions existing in the cylinder. To account for turbulence effects, a model parameter is introduced in the burning rate model. Calculations show that for Dutch Natural Gas (DNG)/ethane/propane mixtures a single model parameter, independent of the gas composition, is sufficient to predict the pressure profiles accurately. In contrast, the model parameter for DNG/H2 mixtures shows a dependence on the hydrogen content in the fuel. Adjustment of the model parameter resulted in successful prediction of the effect of hydrogen on the combustion phasing.