Question
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Calculate the stroke length (in feet) of an engine with the following parameters: 6 cylinders, has an indicated mean effective pressure (IMEP) of 1510 psi per cylinder, a bore of 3.8 inches, operating at 1270 rpm , and operates at 1900 horsepower. Round to 2 decimal places.

Ask by Stuart Reyes. in Canada
Dec 09,2024

Real Tutor Solution

Tutor-Verified Answer

Answer

The stroke length of the engine is approximately 0.04 feet.

Solution

To calculate the stroke length of the engine, we can use the following formula that relates the engine's power output, IMEP, engine speed, and displacement: \[ \text{Power} = \frac{IMEP \times \text{Displacement} \times \text{RPM}}{33,000} \] Where: - Power is in horsepower (hp) - IMEP is in psi - Displacement is in cubic inches (ci) - RPM is the engine speed in revolutions per minute - 33,000 is a conversion factor to convert from foot-pounds per minute to horsepower ### Step 1: Calculate the Displacement The displacement of a single cylinder can be calculated using the formula: \[ \text{Displacement per cylinder} = \frac{\pi}{4} \times \text{Bore}^2 \times \text{Stroke} \] The total displacement for all cylinders is: \[ \text{Total Displacement} = \text{Displacement per cylinder} \times \text{Number of cylinders} \] ### Step 2: Rearranging the Power Formula We can rearrange the power formula to solve for the total displacement: \[ \text{Total Displacement} = \frac{\text{Power} \times 33,000}{IMEP \times \text{RPM}} \] ### Step 3: Plugging in the Values Given: - Power = 1900 hp - IMEP = 1510 psi - RPM = 1270 - Number of cylinders = 6 - Bore = 3.8 inches Calculating the total displacement: \[ \text{Total Displacement} = \frac{1900 \times 33,000}{1510 \times 1270} \] Calculating the numerator: \[ 1900 \times 33,000 = 62,700,000 \] Calculating the denominator: \[ 1510 \times 1270 = 1,915,700 \] Now, calculating the total displacement: \[ \text{Total Displacement} = \frac{62,700,000}{1,915,700} \approx 32.69 \text{ cubic inches} \] ### Step 4: Calculate Displacement per Cylinder Now, we divide the total displacement by the number of cylinders: \[ \text{Displacement per cylinder} = \frac{32.69}{6} \approx 5.45 \text{ cubic inches} \] ### Step 5: Calculate Stroke Length Now we can use the displacement per cylinder to find the stroke length. Rearranging the displacement formula gives us: \[ \text{Stroke} = \frac{4 \times \text{Displacement per cylinder}}{\pi \times \text{Bore}^2} \] Substituting the values: \[ \text{Stroke} = \frac{4 \times 5.45}{\pi \times (3.8)^2} \] Calculating the denominator: \[ \pi \times (3.8)^2 \approx 3.14159 \times 14.44 \approx 45.39 \] Now calculating the stroke: \[ \text{Stroke} = \frac{21.8}{45.39} \approx 0.48 \text{ inches} \] ### Step 6: Convert Stroke Length to Feet To convert inches to feet, we divide by 12: \[ \text{Stroke in feet} = \frac{0.48}{12} \approx 0.04 \text{ feet} \] ### Final Result The stroke length of the engine is approximately: \[ \text{Stroke Length} \approx 0.04 \text{ feet} \] Thus, the final answer rounded to two decimal places is: \[ \text{Stroke Length} \approx 0.04 \text{ feet} \]

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The Deep Dive

To find the stroke length of the engine, we can use the formula for horsepower (\(HP\)) in terms of the dimensions and performance of the engine: \[ HP = \frac{(IMEP \times A \times L \times N)}{33,000} \] where: - \(HP\) is the horsepower (1900 HP) - \(IMEP\) is the indicated mean effective pressure (1510 psi) - \(A\) is the area of the piston (in square inches) - \(L\) is the stroke length (in inches) - \(N\) is the engine speed (number of power strokes per minute) Since this is a 6-cylinder engine, each cylinder works in a two-stroke cycle for every crankshaft rotation, meaning effective power strokes per minute for a four-stroke engine is half the RPM. Let's find the area \(A\) first: \[ A = \pi \left(\frac{B}{2}\right)^2 \] where \(B\) is the bore in inches. Given: - Bore \(B\) = 3.8 inches Thus, \[ A = \pi \left(\frac{3.8}{2}\right)^2 \approx 11.34 \text{ in}^2 \] ### Effective Power Strokes For a 6-cylinder engine at 1270 RPM: 1. Each cylinder produces a power stroke once every two revolutions (for a four-stroke engine). 2. Thus total effective strokes (assuming a four-stroke engine) = \[ N = 1270 \times \frac{6}{2} = 3810 \text{ strokes/min} \] ### Rearranging the Horsepower Formula We need to express stroke length \(L\): \[ L = \frac{HP \times 33,000}{IMEP \times A \times N} \] Plugging in the numbers: - \(HP = 1900\) - \(IMEP = 1510\) - \(A \approx 11.34\) - \(N = 3810\) Giving, \[ L = \frac{1900 \times 33,000}{1510 \times 11.34 \times 3810} \] Calculating: \[ L = \frac{62700000}{1510 \times 11.34 \times 3810} \approx 3.77 \text{ inches} \] To convert to feet: \[ L \approx \frac{3.77}{12} \approx 0.31 \text{ feet} \] So, the stroke length of the engine is approximately **0.31 feet** when rounded to two decimal places.

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