A six cylinder, single acting, four-stroke/cycle diesel engine has a bore of 10 1/2 inches, and a stroke of one foot, producing 75 HP per cylinder at 720 RPM. What is the mean effective pressure in the engine cylinders for the stated conditions?
• Indicated horsepower formula for a four-stroke diesel engine • Relationship between mean effective pressure (MEP), power, displacement per cycle, and RPM • Unit conversions for area (square inches to square feet) and pressure in psi
• How do you express power in terms of mean effective pressure, piston area, stroke, number of power strokes per minute, and number of cylinders? • For a four-stroke engine running at 720 RPM, how many power strokes per minute does each cylinder actually have? • After you solve for mean effective pressure, does the magnitude of your result seem physically reasonable compared to typical diesel cylinder pressures?
• Be sure to convert bore diameter to piston area correctly (using (A = \pi D^2/4)) • Remember that in a four-stroke engine, each cylinder has one power stroke every two revolutions • Confirm that you are using horsepower units consistently, including the factor 33,000 ft·lb/min when relating work per minute to HP
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