Question

What is the scavenging efficiency for the perfect mixing if the delivery ratio is 1.5?

(a) 80.73%

(b) 81.73%

(c) 82.73%

(d) 84.73%

I had been asked this question in an interview.

I'm obligated to ask this question of 2 Stroke Engines in division Internal Combustion Engines of Automobile Engineering

Answer 1

Correct choice is (b) 81.73%

To explain I would say: Delivery ratio = R = 1.7 and scavenging efficiency = ηsc. The relation between the R and ηsc is ηsc = 1 – e^-R  = 1 – e^-1.7 = 1 – 0.1826 = 0.8173 = 81.73%. In perfect mixing, the incoming fresh charge mixes completely and instantaneously with the cylinder contents. A portion which is mixed gets passed out at a rate equal to that of charge entering the cylinder.