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This specification has been declared "CANCELLED" by the Aerospace Materials Division, SAE as of January 1990.

A new rotary type carburetor was developed for a gasoline engine. It has a rotor which feeds fuel into an engine proportionally to the inlet air flowrate. Comparing with a conventional venturi type carburetor it was simple in design with less parts. The rotary type carburetor was tested on an engine dynamometer for the various engine operating conditions. During acceleration and deceleration, the rotary type carburetor could not supply the fuel adequately, resulted in unstable engine operation. Under steady running conditions the rotary type carburetor was superior to venturi type in power and fuel economy. It was concluded from the experimental study that the rotary type carburetor is more suitable for the steady running gasoline engines especially at high speeds.

A theoretical analysis of the stoichiometry of the mixture produced in a main fuel system of the engine carburetor is presented. The analysis made it possible to develop a computer code which was applied to the particular Weber type carburetor from a small, two-cylinder car engine. The operation of the carburetor in the regimes of the steady and unsteady flow, including the influence of back flows, was investigated. It is concluded that the air pressure pulsations and, in particular, the existence of the back flows cause the significant enrichment of the mixture produced in the carburetor.

Nowadays design and production of carburetor can not make the mixture of carburetor fit in with the ideal value of A/F ratio on all running conditions,the method of using micro-processor control A/F ratio can solve this problem.In this paper,the self-tuning and adaptive control method was used to realize the optimal control for A/F ratio.Based on the open-loop control,this method was combined with the close-loop control. The adaptive control method of using difference of slope change at the lowest specific fuel consumption point on fuel adjustment curve has wide adaptive ability.It is superior to the open-loop control,and does not need to use expensive exhaust gas oxygen sensor and other detect sensors compared with other close-loop control.The method that uses the rate of speed change to add air perturbation as feed-back singal is easy to use practically.

In this study, accordingly, methanol fuel was supplied in suction pipe with carburetor and with electronically-controlled fuel injector (EFI), which located in front of the suction valve, to clear experimentally the influence of various factors, such as the methanol-gasoline ratio (M/F), the difference in fuel feed system, the number of times of injection [ni], the injection timing (θinj), the engine speed (N), the volumetric efficiency (η v), the suction pipe wall temperature (tw), the water content in fuel (yw) etc., on the engine performance (the output and the thermal efficiency), the exhaust characteristics (NOx, CO, UBF and HCHO concentrations) and combustion variation as well as obtaining a guideline to establish the optimum condition. The authors will be report about the results of above-mentioned.

Increasing emphasis on natural gas as a clean, economical, and abundant fuel, encourages the search for the optimum approach to management of fuel, air and combustion to achieve the best results in power, fuel economy and low exhaust emissions. Electronic injection of fuel directly into the throttle body, intake ports or directly into the cylinder offers important advantages over carburetion or mixing valves. This is particularly true in the case of installations in which the gas supply is available at several atmospheres pressure above maximum intake manifold pressure. The use of choked-flow pulse- width-modulated electronic injectors offers precision control over the engine operating range with a wide variety of options for both stoichiometric and lean bum applications. A complete system utilizing commercially available components together with the application, calibration and engine mapping techniques is described.

This SAE Recommended Practice covers all carburetors and throttle bodies used on permanently installed gasoline marine engines.

This work presents an approach for developing a control algorithm for fuel delivery at cold start based on C.F.Aquino's fuel film dynamic model [1]. The control algorithm presented takes into account the fuel delivery both in the fuel film form and in the form of droplets and vapor, that allows setting the limits on the fuel supply calculation in order to achieve good startability (without spark plug wetting) and low CO and HC emission. An algorithm was developed as a computer program and tested in calculation experiments. Although the empirical parameters of mathematical fuel delivery model were determined on a carburetor engine, this control algorithm is also applicable to engines with fuel injection due to similarity of the physical nature of mixture preparation.

Detergent additives in motor gasoline have come a long way since they were first developed and introduced commercially in 1954 by the Standard Oil Company of California (now Chevron). Limits on vehicle emissions to the atmosphere and mandated fleet fuel economy have made effective deposit control additives essential in modern automotive gasolines. This paper will describe how it all started. The problem that inspired this development was called carburetor gumming. Taxicab fleets and other cars engaged in stop and go service developed symptoms of rich, rough idling that required frequent idle mixture adjustment and eventually cleaning of the carburetor. Engine blowby ingested at idle from the oil fill cap and draft tube was determined to be a major source of the problem. A quick test using a laboratory engine equipped with a glass carburetor throttle body and the blowby piped into the air intake simulated thousands of miles driving in two hours.

This paper deals with an investigation of the scavenging and power performances of a two-stroke cycle gasoline engine having poppet valves in the cylinder head but no cylinder ports. In a previous experiment, a model test apparatus was used to carry out the experimental analysis of scavenging performance. We found as a result of this analysis that better scavenging efficiency could be obtained by improving the flow pattern of scavenging gas in the cylinder by means of scavenging valves with shroud than by perfect diffusion scavenging. The present experimental study using a real engine was conducted according to this finding. The basic engine is a four-stroke motorcycle engine, one cylinder, 250 cm3, twin-cam, four-valve. The engine was modified into a two-stroke cycle engine by altering the camshafts so as to have twice the engine speed of the four-stroke cycle engine, and the valve timings were adjusted by a pin that connected the camshaft and sprocket.

The effect of the presence of liquid fuel in the intake manifold on unburned hydrocarbon (HC) emissions of a spark-ignited, carbureted, air-cooled V-twin engine was studied. To isolate liquid fuel effects due to the poor atomization and vaporization of the fuel when using a carburetor, a specially conditioned homogeneous, pre-vaporized mixture system was developed. The homogeneous mixture system (HMS) consisted of an air assisted fuel injection system located approximately 1 meter upstream of the intake valves. The results from carburetor and HMS are compared. To verify the existence of liquid fuel in the manifold, and to obtain an estimate of its mass, a carburetor-mounted liquid fuel injection (CMLFI) system was also implemented. The conditions tested were 10% and 25% load at 1750 RPM, and 25%, 50%, and 100% at 3060 RPM. The results of the comparison show that the liquid fuel in the intake manifold does not have a statistically significant influence on the averaged HC emissions.

A commercial CFD package was used to develop a three-dimensional, fully turbulent model of the compressible flow across a complex-geometry venturi, such as those typically found in small engine carburetors. The results of the CFD simulations were used to understand the effect of the different obstacles in the flow on the overall discharge coefficient and the static pressure at the tip of the fuel tube. It was found that the obstacles located at the converging nozzle of the venturi do not cause significant pressure losses, while those obstacles that create wakes in the flow, such as the fuel tube and throttle plate, are responsible for most of the pressure losses. This result indicated that an overall discharge coefficient can be used to correct the mass flow rate, while a localized correction factor can be determined from three-dimensional CFD simulations in order to calculate the static pressure at locations of interest within the venturi.

Although each carburetor design is slightly different, it is possible to define some basic elements that can be used as building blocks to describe many carburetor designs. All carburetors designs use small metering orifices to constrain fuel and air flow through different circuits. This paper presents the CFD analysis of fuel flow across small metering orifices typically found in small engine carburetors. The analysis was divided into three parts: first, CFD simulations of liquid flow in square-edged orifices were performed. These simulations indicated the appropriate turbulent model and numerical parameters to be used in the study of orifices with more complex geometries. Second, inlet and outlet chamfers were added to the square-edged orifices, which allowed for understanding their effect on the characteristics of the flow. Finally, the simulations were performed on geometries that represented metering orifices found in real carburetors.

This paper presents a theoretical analysis of the fuel and air flows within the idle circuit found in simple carburetors. The idle circuit is modeled numerically using a dynamic model that considers the resistances of the flow paths as well as the inertia of the fuel. The modeling methodology is flexible, in that the organization and techniques can be applied to any configuration and geometry. The numerical model calculates the fuel flow response of carburetor idle/transition circuits to pressure variations associated with air flow through the venturi and around the throttle plate. The model is implemented for a typical small engine carburetor and the nominal results are presented for this specific design.