The compression ratio of a spark-ignition engine is 8 to 1, the indicated engine efficiency is 80%, and the mechanical efficiency is 76% when 20% excess air is used. Determine the brake thermal efficiency.
Added by Juan Miguel E.
Step 1
First, we need to find the indicated thermal efficiency. Indicated thermal efficiency (ITE) is the product of the indicated engine efficiency and the ideal air-standard efficiency (Otto cycle efficiency). The Otto cycle efficiency can be calculated using the Show more…
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A spark-ignition engine has a compression ratio of 8 an isentropic compression efficiency of 85 percent, and an isentropic expansion efficiency of 95 percent. At the beginning of the compression, the air in the cylinder is at 13 psia and $60^{\circ} \mathrm{F} .$ The maximum gas temperature is found to be $2300^{\circ} \mathrm{F}$ by measurement. Determine the heat supplied per unit mass, the thermal efficiency, and the mean effective pressure of this engine when modeled with the Otto cycle. Use constant specific heats at room temperature.
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A spark-ignition engine has a compression ratio of 8, an isentropic compression efficiency of 85 percent, and an isentropic expansion efficiency of 95 percent. At the beginning of the compression, the air in the cylinder is at 13 psia and 60°F. The maximum gas temperature is found to be 2300°F by measurement. Determine the heat supplied per unit mass, the thermal efficiency, and the mean effective pressure of this engine when modeled with the Otto cycle. Use constant specific heats at room temperature.
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