A 4-cylinder, 4-stroke automobile engine has a 4.5 in bore and a 7 in stroke. Th

Question

A 4-cylinder, 4-stroke automobile engine has a 4.5 in bore and a 7 in stroke. The air in the inlet manifold is at 13 psia, 70 oF. The engine is operating at 1710 RPM.

a.) What is the specific volume of the air in the inlet manifold? _____ ft^3/lbm

b.)What is the total engine displacement volume? _____ in^3

c.) What is the volume flow rate through the inlet valves? _____ ft^3/s

d.) What is the mass flow rate through the engine? _____ lbm/s

Please show work! I'm having trouble converting units and program will not accept my answers. Thanks

Explanation / Answer

For air, gas constant R = 1716 ft-lb/slug-R

a) P = 13 psia = 13 lb/in^2 = 13*32.2 lbf/in^2 = 13*32.2 / (1/12)^2 lbf/ft^2 = 13*32.2*12^2 lbf/ft^2

spcific volume v = RT/P = 1716*(70+460)/(13*32.2*12^2) = 15.088 ft^3/lb

b) Total dispalcement volume = n*(/4*d^2*L) = 4*(3.14/4*4.5^2*7) = 445.095 in^3

c) Volume flow rate = 445.095*(N/2/60) = 445.095*(1710/2/60) = 6342.604 in^3/s = 6342.604/12^3 ft^3/s = 3.6705 ft^3/s

d) Mass flow rate = vol flow rate*density = 3.6705*(1/15.088) = 0.2433 lb/s

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