Experimental Investigation of Hydrogen Addition in the Intake Air of Compressed Engines Running on Biodiesel Blend

This study investigates experimentally the effects
of hydrogen addition in the intake manifold of a diesel generator
operating with a 7% biodiesel-diesel oil blend (B7). An experimental
apparatus setup was used to conduct performance and emissions tests
in a single cylinder, air cooled diesel engine. This setup consisted
of a generator set connected to a wirewound resistor load bank that
was used to vary engine load. In addition, a flowmeter was used to
determine hydrogen volumetric flowrate and a digital anemometer
coupled with an air box to measure air flowrate. Furthermore, a
digital precision electronic scale was used to measure engine fuel
consumption and a gas analyzer was used to determine exhaust
gas composition and exhaust gas temperature. A thermopar was
installed near the exhaust collection to measure cylinder temperature.
In-cylinder pressure was measured using an AVL Indumicro data
acquisition system with a piezoelectric pressure sensor. An AVL
optical encoder was installed in the crankshaft and synchronized
with in-cylinder pressure in real time. The experimental procedure
consisted of injecting hydrogen into the engine intake manifold
at different mass concentrations of 2,6,8 and 10% of total fuel
mass (B7 + hydrogen), which represented energy fractions of 5,15,
20 and 24% of total fuel energy respectively. Due to hydrogen
addition, the total amount of fuel energy introduced increased
and the generators fuel injection governor prevented any increases
of engine speed. Several conclusions can be stated from the test
results. A reduction in specific fuel consumption as a function
of hydrogen concentration increase was noted. Likewise, carbon
dioxide emissions (CO2), carbon monoxide (CO) and unburned
hydrocarbons (HC) decreased as hydrogen concentration increased.
On the other hand, nitrogen oxides emissions (NOx) increased due
to average temperatures inside the cylinder being higher. There
was also an increase in peak cylinder pressure and heat release
rate inside the cylinder, since the fuel ignition delay was smaller
due to hydrogen content increase. All this indicates that hydrogen
promotes faster combustion and higher heat release rates and can
be an important additive to all kind of fuels used in diesel generators.