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Fuel metering system and controlling fuel-air mixture of spark ignition engines have been the major goals for the researcher. Management in mixture quality and fuel economy have resulted in changing carburetor systems to injection systems. Start of fuel injection position and injection duration play important role in engine performance. In the current work a single cylinder research engine with capability of adjusting spark timing and controlling gasoline injection start position and duration was utilized. Compression ratio, engine speed and injection start position were adjusted to 8, 1800 rpm and breathing top dead center (BTDC), respectively. Injection duration and spark timing were controlled so that to achieve maximum output torque at equivalence ratio of 0.90. Fixing them, the start of injection was only changed in the range of -180 to 180°CA relative to BTDC with a 30°CA increment. For each case, cylinder pressure of 500 successive cycles were recorded and stored. The obtained results showed that the dispersion of indicated mean effective pressure (imep) data of the cases with injection position start after BTDC were higher than those of the cases with injection position start before BTDC. Also, the average values of imep and peak pressure and their coefficient of variation changed with varying fuel injection start position; and for the cases of high dispersion in imep data, the average values of imep and isfc appeared to be high and low respectively.

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The importance of pollutant control and shortage of fossil fuel reservoirs have caused the development of injector systems and researches on optimum fuel consumption of internal combustion engines. The main purpose of this work is to study the effect of fuel injection start angle on engine performance features such as indicated power, exhaust emissions (CO and HC), ignition delay and fast burn length in a single cylinder port injection SI engine using gasoline and natural gas individually as fuel. Injection period, ignition timing, engine speed and throttle plate position were fixed and start angle of injection (SOI) was varied. The obtained results show that higher indicated power and lower CO emission are achieved when SOI is adjusted so that the injecting fuel and flowing air are entering simultaneously into the cylinder; however, higher unburned HC emission is resulted at the condition. Heat release rate analysis was used to evaluate ignition delay and fast burn length. The results show that the lowest ignition delay happens when the SOI is adjusted so that the part of injected fuel at the late intake stroke is higher; and the fast burn length is decreased as both injecting fuel and flowing air are entering into the cylinder during the injection period.

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In this paper with a comprehensive approach, energy, exergy, economic and environmental (4E) analyses of an organic Rankine cycle (ORC) have been performed to produce combined heat and power (CHP) based on solar energy. In order to a plenary survey, after thermodynamic modeling of the ORC, study of flat plate and parabolic through solar collectors (FPC and PTC) and gas-fired boiler as the energy supplier equipments in the independent or combination models; as well as in the open or circulated state of the heat source flow have done. In the open heat source flow state, the outlet flow of heat source at 80 ° C temperature is used in order to provide required heat in different sectors; however, in the circulated flow state, the amount of required primary energy is less than the open heat source flow state. Also, the use of photovoltaic panels to provide the pumping power of cycle is studied. The calculations show that the cost of produced power for this study schale in Iran, from lowest to highest are related to the use of gas-fired boiler, parabolic trough solar collector, photovoltaic panels and flat plate solar collectors respectively. Also, because of the efficient use of energy resources in the combined heat and power generation (open heat source flow) compared to power generation (circulated heat source flow), the energy and exergy efficiencies are increased 8.61% and 8.11% respectively; although the open heat source flow system compared to circulated flow system need to higher investment cost.

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Blowby phenomenon of fuel-air mixture from cylinder-piston crevices, which occurs due to difference of in-cylinder and connected crevice pressures, influences engine performance. In the current work, experimental data of gasoline fuelled motoring condition at equivalence ratio of 0.9 were collected from a single cylinder research engine using skip spark technique. A relatively simple non-thermodynamic polytropic-base model was introduced and orifice-volume theory was coupled it; and gas flow through crevices was studied. From positive points of the model, it can be implied that the model predicts cyclic blowby without performing complex heat transfer and thermodynamic calculations. A verified thermodynamic simulation model including blowby sub-model was used to validate the polytropic-base model. Cylinder pressure evaluated by the thermodynamic model had good agreement with the measured pressure in the gasoline fuelled motoring condition at the equivalence ratio. First, in the polytropic-base model, output cylinder pressure of the thermodynamic simulation model was defined instead of experimental cylinder pressure and its blowby was evaluated. Then entering experimental cylinder pressure at equivalence ratio of 0.9 to the current model, cylinder mass and blowby to crevices were evaluated and compared with the predictions of the thermodynamic model. A very good agreement was observed between the obtained results and the results of the thermodynamic model. The new model showed maximum 6.88% cylinder mass lost around peak pressure position decreasing to 0.45% along the late expansion stage.

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