Question

A 3.6-liter, V6 SI engine is designed to have a maximum speed of 7000 RPM. There are two intake valves per cylinder, and valve lift equals one-fourth valve diameter. Bore and stroke are related as S = 1.06 B. Design temperature of the air-fuel mixture entering the cylinders is 60°C. Calculat!(: (a) Ideal theoretical valve diameter. [em] . (b) Maximum flow velocity through intake valve. [mIsec] (c) Do the valve diameters and bore size seem compatible?

Answer 1

To develop this problem, it will be necessary to apply geometric and energy relationships to calculate the velocities of the fluids as well as the dimensions of the Valve. We will start by calculating the volume displacement and rewrite this equation based on the Bore and Stroke. Later we will calculate the average speed of the piston and finally we will make the calculations of the required dimensions. Calculate displacement volume,

$V_d = \frac{3.6L}{6}$

$V_d = 0.6L (\frac{10^{-3}m^3}{1L})$

$V_d = 0.0006m^3$

Write the expression for displacement volume,

$V_d = \frac{\pi}{4}B^2S$

$0.0006 = \frac{\pi}{4}B^2(1.06B)$

The Bore will be,

$B = 0.0897m$

$B = 8.97cm$

The Stroke will be,

$S = 1.06B$

$S = 1.06*8.97cm$

$S = 0.095m$

$S = 9.5m$

Then the sonic velocity under this conditions will be,

$c = \sqrt{kRT}$

$c = \sqrt{1.4(287)(273+60)}$

$c = 366m/s$

Calculate the avarage piston speed at maximum speed

$(U_p)_{max} = 2SN$

$(U_p)_{max} = 2 (0.095m/stoke)(\frac{7000}{60}rev/s)$

$(U_p)_{max} = 22.17m/s$

Calculate total intake valve area using the following relation

$A = 1.3B^2 (\frac{U_p{max}}{c_1})$

$A = (1.3)(8.97)(\frac{22.17}{366})$

$A = 6.34cm^2$

Calculate area of the one valve,

$A_1 = \frac{A}{2}$

$A_1 = \frac{6.34}{2}$

$A_1 = 3.17cm^2$

PART A) Calculate the ideal thermotical valve diameter,

$A_i = \frac{\pi}{4} d_v^2$

$3.17 = \frac{\pi}{4}d_v^2$

$d_v = 2.01cm$

PART B) Calculate maximum flow velocity through intake

$V_{max} = c$

$V_{max} = 366m/s$

PART C) Comparing both dimension not are equal.