What does mean effective pressure (MEP) indicate in engine performance analysis?

Explanation:

Mean Effective Pressure (MEP) in Engine Performance Analysis

• The Mean Effective Pressure (MEP) is a critical parameter in engine performance analysis. It represents the average pressure acting on the piston during the entire engine cycle, which would produce the measured work output if it were applied uniformly. MEP is not an actual physical pressure but a theoretical concept used to evaluate the performance and efficiency of internal combustion engines.
• In simpler terms, MEP provides a way to compare the work output of engines irrespective of their size, speed, or displacement. This parameter is especially useful for engineers and designers to assess and optimize engine designs.

\(mep = \frac{{{W_{net}}}}{{{V_s}}}\)

For Otto cycle:

\({W_{net}} = {Q_1} - {Q_2} = m{C_v}\left[ {\left( {{T_3} - {T_2}} \right) - \left( {{T_4} - {T_1}} \right)} \right]\)

\({V_s} = {V_1} - {V_2} = {V_1}\left( {1 - \frac{{{V_2}}}{{{V_1}}}} \right) = {V_1}\left( {1 - \frac{1}{r}} \right)\)

\({V_s} = {V_1}\left( {\frac{{r - 1}}{r}} \right) = \frac{{mR{T_1}}}{{{P_1}}}\left( {\frac{{r - 1}}{r}} \right) = \frac{{m{C_v}\left( {r - 1} \right){T_1}}}{{{P_1}}}\left( {\frac{{r - 1}}{r}} \right)\)

\(mep = \frac{{{W_{net}}}}{{{V_s}}} = \frac{{m{C_v}\left[ {\left( {{T_3} - {T_2}} \right) - \left( {{T_4} - {T_1}} \right)} \right]}}{{\frac{{m{C_v}\left( {\gamma - 1} \right){T_1}}}{{{P_1}}}\left( {\frac{{r - 1}}{r}} \right)}}\)