SI-Engine

Expt. 4 Spark Ignition Engine

Apparatus Used:
(1) Tachometer
(2) Mercury Thermometer
(3) beaker

Procedure:
1
2
3
4
5
6
7

8

9

10
11
12
13

Make sure that all windows in the room are opened
Put two electric fans near the exhaust manifold to avoid any health
hazards
Put a water on the water storage
Connect the battery to the battery clamp having a correct polarity
Put a gasoline on the fuel container
Start the engine and run it for few minutes to reach a steady state
condition.
Once the engine reaches a steady state condition, set the desired
engine speed (rpm) and start the timer for a specific volume that will
be consumed. Do this measurement in no load condition
After this process, take out 1 spark plug connection of the engine ( so
called cylinder cut-off) and record the new engine speed and set the
time taken for consuming a known volume of fuel.
Then return back the take out 1 sparkplug connection, and remove
another 1 sparkplug connection in other cylinder. ( Do this in vice versa
until you reaches in cylinder 4)
Do this measurement again in load condition.
Repeat step 7, 8 and 9.
Also measure the temperature of the exhaust gas in every new speed
acquired
The power developed by the engine is measured.

14 Graph the torque and power against rpm, break efficiency against
brake power and other relations
15 Basic measurements: Engines are power producing systems. In order
to determine their capacities and suitability for applications, it is
necessary to measure their levels of performance in meeting various
requirements. The important parameters considered for the
measurement of performance of the engine are:
a Measurement of Speed: A digital tachometer can be used to
measure the speed of the shaft.
b Measurement of Fuel Consumption: In this the time taken
for a known volume of fuel consumption is measured and the
fuel consumption rate can be calculated. The fuel consumption
rate can be calculated as, Fuel Consumption (kg/hr) =
Volume*specific gravity of fuel/1000 * time
c Measurement of Brake Power: It involves the determination
of torque and power developed at the engine output shaft. The
torque is measured by the hydraulic dynamometer. The
hydraulic dynamometer is run by the chain sprocket
arrangement provided between the engine output shaft and
dynamometer’s sprocket. The brake power can be calculated
using , Brake power = 2πTN
d Specific Fuel Consumption: Is the amount of the fuel
consumed per unit of power developed per hour. It is a clear
indication of the efficiency with which the engine develops
power from the fuel. SFC = (fuel consumed in kg/kw.hr) / (power
developed).