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International concerns over small engine efficiency and emissions characteristics have lead to several efforts to develop improved internal combustion engine cycles, including investigation of Homogeneous Charge Compression Ignition (HCCI) and Premixed Charge Compression Ignition (PCCI) modifications to classic combustion cycles. Kashmerick Engine Systems LLC. has proposed a K6 cycle that moves the combustion process to an external continuous-combustion chamber to decrease the rate of combustion and allow optimization of the combustion chamber and piston-cylinder as a compression and expansion device separately to improve efficiency and reduce emissions. This paper describes 0-dimension modeling of both an air-standard dual-cycle model and an air-standard K6 cycle model in Engineering Equation Solver (EES) to compare the ideal performance of the two cycles.

The purpose of this research is to develop a prediction technique that can be used in the development of port fuel-injection (hereinafter called PFI) gasoline engines, especially for general purpose small utility engines. Utility engines have two contradictory desirable aspects: compactness and high-power at wide open throttle. Therefore, applying the port fuel injector to utility engines presents a unique intractableness that is different from application to automobiles or motorcycles. At the condition of wide open throttle, a large amount of fuel is required to output high power, and injected fuel is deposited as a wall film on the intake port wall. Despite the fuel rich condition, emissions are required to be kept under a certain level. Thus, it is significant to understand the wall film phenomenon and control film thickness in the intake ports.

A modified Brayton cycle is incorporated into a continuous combustion engine system. This 6-stroke engine system is described and illustrated with pressure-volume diagrams. Potential advantages over the traditional 4-stroke Otto cycle are reviewed in the areas of emissions, flexible-fuel use, energy conversion efficiency, and noise. A detailed 1-D air standard thermodynamic model of the K6 cycle is generated and used to investigate the potential efficiency of this cycle and analyzed from partial throttle to wide-open throttle power output. The affects of compression ratio and expansion variations on efficiency are evaluated. The power output and power density are estimated. Key assumptions in the analysis of the thermodynamic model are discussed. Comparisons are made to a similar level of analysis of an Otto cycle 4-stroke engine. A utility engine simulating this cycle operating on compressed air is described.

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.

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.