Question

What is the ideal efficiency of the diesel engine having a cylinder with bore 250 mm, stroke 375 mm and a clearance volume of 1500 cc, with fuel cut-off occurring at 5% of the stroke. Assume $\gamma$ = 1.4 for air.

• A. 60.52%
• B. 37.50%
• C. 27.12%
• D. 50.52%

Answer 1

The correct option is A 60.52%

$V_a=\frac{\pi }{4}{d}^{2}L=\frac{\pi }{4}\times {25}^2\times 37.5=18407.8cc$

$r=1+\frac{V_s}{V_c}=1+\frac{18407.8}{1500}=13.27$

$\eta =1-\frac{1}{r^{\gamma -1}}\frac{r_c^{\gamma }-1}{\gamma (r_c-1)}$

$r_c=\frac{V_3}{V_2}$

Cut- off colume = $V_3-V_2=0.05V_s=0.05\times 12.27V_c$

$V_2=V_c$

$V_3=1.6135V_c$

$r_c=\frac{V_3}{V_2}=1.6135$

$\eta =1-\frac{1}{{13.24}^{0.4}}\times \frac{{1.6135}^{1.4}-1}{1.4\times (1.6135-1)}$

$=0.6052=60.52\%$