Throttle valve was also adjusted for each speed using another step
motor and by means of same parallel port. Two computers collected all
the data from experiments as indicated in figure 1.
For each run, the engine was started on pure LPG and then switched
to the test water to arrange fuel mass ratio. All tests were performed at
constant load and variable engine speed and MBT (Maximum brake
torque) ignition timing. At each operating condition, the dynamometer
load, speed, exhaust gas temperature, fuel and water flow rates were
recorded after allowing sufficient time for the engine to stabilize. The
experiments for each case were replicated in a test point until the
difference between two measurement values falls within 5% error.
Averaging was performed to minimize the effects of variations than this
error level. Calibration check of the devices was made two times that
were before and after each successive test.
The engine test system is made up of several different transducers
and data acquisition system. The error due to data acquisition system
used in this study is on the order of 0.02% for 12 bit system and is
considered negligible when compared to the other sources of error.
The errors in the measurements of the basic quantities and estimated