Question

What is the formula for indicated mean effective pressure?

(a) Pi = \(\frac{(Area \, of \, indicator \, diagram)}{Length \, of \, indicator \, diagram  \, * \,  spring \, scale \, index} \)

(b) Pi = \(\frac{(Length\, of \, indicator \, diagram \, * \, spring\, scale \,index)}{Area\, of \,indicator \, diagram} \)

(c) Pi = \(\frac{Length \, of \, indicator \, diagram}{Area \,of \,indicator\, diagram \, * \, spring \, scale \, index} \)

(d) Pi = \(\frac{Spring \, scale \, index}{Area \, of \, indicator \, diagram \, * \, Length \, of \, indicator \, diagram} \)

The question was asked in final exam.

My doubt is from I.C Engine in chapter Internal Combustion Engine of Farm Machinery

Answer 1

Right choice is (a) Pi = \(\frac{(Area \, of \, indicator \, diagram)}{Length \, of \, indicator \, diagram  \, * \,  spring \, scale \, index} \)

For explanation I would say: Indicated mean effective pressure is the algebraic sum of the mean pressures acting on the piston during each stroke over one complete cycle. It is measured through indicator diagram drawn with the help of an engine indicator.