Questions 7 to 12 refer to the following

A spark ignition petrol engine is modeled using the Otto Cycle as an Air Standard Cycle

approximation. The Air standard Otto cycle has a compression ratio of 16, and the pressure is

increased by a multiple of 2.3 during the constant-volume heat-addition process. At the beginning

of the compression process, the air in the cylinder is at 99 kPa and 32 "C.

Assume that air is an ideal gas with constant specific heats Cv=718 J/kgK and C₂ = 1005 J/kgK,

and specific gas constant R-287 J/kgK and the ratio of specific heats k = 1.4.

QUESTION 7

Sketch both a P-V and a T-S state diagram for the cycle, with corresponding numbers indication

the initial and final state of each thermodynamic process.

QUESTION 8

Calculate the air pressure and temperature at the end of the compression stroke.

QUESTION 9

Calculate the amount of heat transferred to the air in the heating process, and the amount of heat

rejected in the cooling process.

QUESTION 10

Calculate the boundary work input for the compression process and the boundary work output for

the expansion process.

QUESTION 11

Calculate the overall thermal efficiency of the Otto cycle, then compare this to the Carnot cycle

efficiency calculated for the same temperature limits, giving the primary reasons for the difference

between the two efficiency values.

QUESTION 12

Explain the relationship between the fuel flow rate into the engine, and the calculated heat input

into the Otto cycle.