1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Diesel engine

  1. May 30, 2015 #1
    What is the relation between p max and mean effective pressure inside the cylinder
  2. jcsd
  3. May 30, 2015 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF Mohamed!

    The relationship between pressure (ie. the pressure inside the cylinder between piston and end of cylinder) and volume (volume of the cylinder between the piston and end of cylinder) can be determined from the PV diagram for the diesel cycle.

    If by "p max" you mean the maximum pressure attained, that is easily determined from the highest point in the PV diagram (i.e. 2-3).

  4. Jun 5, 2015 #3
    Heres an old equation including (brake) mean effective pressure (P):
    (P would appear to be akin to average pressure)
    BHP = ( P*L*A*N ) / 33,000
    P = bmep in psi
    L = piston stroke in feet
    A = area of piston in sq ins
    N = number of power strokes per minute

    Basically, its the work done in 1 minute / the official work done by 1 BHP
    ( 1 BHP = 33,000 lbsforce - ( feet / min ) )

    If you had the crank BHP, you could derive the value for P if you know the remaining figures, so:
    P = ( 33,000 * BHP ) / ( L*A*N )

    Its a handy value to know if you need to calculate the power potential of another engine by assuming the bmep to be similar or the same.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook