Question

1. Figure Q1 shows the variation of equivalence ratio, $\phi$ with load (where the load is expressed as percentage of maximum brake torque) for a conventional spark-ignition engine at a fixed engine speed. Also shown here is the variation of total fmep (summation of losses due to pumping, mechanical rubbing and accessory loads). 1.2 Total fmep Equivalence ratio 0.6 0.8 1.0 0 Load (%) Figure Q1 100 Using similar format, sketch a proportioned qualitative graph to present the $(imep)_{gross}$ and bmep variations with load. Indicate clearly the fmep on the sketch, as well as the locations of important points such as when the value is maximum or zero where appropriate. Provide a brief justification for the shape of the curves you sketch. [15 marks]

          1.
Figure Q1 shows the variation of equivalence ratio, $\phi$ with load (where the load is expressed
as percentage of maximum brake torque) for a conventional spark-ignition engine at a
fixed engine speed. Also shown here is the variation of total fmep (summation of losses
due to pumping, mechanical rubbing and accessory loads).
1.2
Total fmep
Equivalence ratio
0.6
0.8
1.0
0
Load (%)
Figure Q1
100
Using similar format, sketch a proportioned qualitative graph to present the $(imep)_{gross}$ and
bmep variations with load. Indicate clearly the fmep on the sketch, as well as the locations
of important points such as when the value is maximum or zero where appropriate. Provide
a brief justification for the shape of the curves you sketch.
[15 marks]

1.
Figure Q1 shows the variation of equivalence ratio, ϕ with load (where the load is expressed
as percentage of maximum brake torque) for a conventional spark-ignition engine at a
fixed engine speed. Also shown here is the variation of total fmep (summation of losses
due to pumping, mechanical rubbing and accessory loads).
1.2
Total fmep
Equivalence ratio
0.6
0.8
1.0
0
Load (%)
Figure Q1
100
Using similar format, sketch a proportioned qualitative graph to present the (imep)gross and
bmep variations with load. Indicate clearly the fmep on the sketch, as well as the locations
of important points such as when the value is maximum or zero where appropriate. Provide
a brief justification for the shape of the curves you sketch.
[15 marks]

Added by Derrick A.

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