Activity 2

You have been asked to provide a report to evaluate the use of diesel, spark-ignition,

2-stroke or 4-stroke options for a new small power generator. Potential customers will

need an efficient, powerful engine that can provide a uniform torque output and is

cheap to operate. Some customers also need basic information on the different

engines and in particular the PV cycle used to describe their operation.

To help the design team your report needs to contain;

a) A section evaluating the relative performance and mechanical efficiency of 2-

stroke and 4-stroke engines

b) A review of the difference in operating cycles of spark-ignition and diesel

engines

(for this you should use the PV diagrams below as a points of reference and to

identify and compare the 4 stages).

Include a review of the efficiencies ideal heat engines operating on the Otto and

Diesel cycles.

P

2

TDC

OTTO CYCLE

1

BDC

-V

PA

B

Qin

DIESEL CYCLE

P₁

P₁

0 V₂V/₂

W

p: pressure

V: specific volume

out

isentropic

sentropic

Qa

V V