Numerical Simulation of Hydrogen Fuel Used with Compression – Ignition IC Engine
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Date
2025-02-19
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Abstract
Internal combustion engines presently power the majority of applications because
of their dependability, power production, and fuel efficiency. With the ability to
blaze cleaner gaseous fuel at a thermal efficiency exceeding that of a diesel-only
engine but with significantly lower emissions, alternative, zero-carbon fuels (such
as hydrogen) are currently attracting attention. Tragically, IC engines cause
economic and ecological harm by emitting high levels of pollutants and
greenhouse gases.
Using numerical modeling and simulation, this thesis aims to improve the
fundamental knowledge of the best way to use hydrogen in internal combustion
engines that use diesel-hydrogen dual-fuel and premixed fuel combustion (PFC)
technologies, in which a specific percentage of the original diesel fuel is replaced
with hydrogen.
In order to simulate hydrogen-enhanced n-heptane combustion, this thesis
designs, executes, and evaluates the computational tools required for premixed
fuel, dual fuel direct injection in the cylinder, and hydrogen swallowed into the
engine's intake air. A three-dimensional cylinder sector was used for the
combustion modeling using ANSYS FLUENT, and the engine speed was varied
between 1500 and 2000 revolutions per minute (rpm). The simulation duration
ranged from 570° to 833° crank angles. The n-heptane and H2 interaction stages
and the CO and NOx generation processes were incorporated into a reaction
mechanism. It comprises 165 reactions and 40 species.
According to the simulation results it is found that boosting the hydrogen mixing
significantly improves the heat release rate, brake thermal efficiency, and peak
cylinder pressure, all contributing to improved performance. In the case of
premixed fuel combustion at 1500 rpm, cylinder pressure rises by 8.2% to 24%,
thermal efficiency improves by 7.1% to 21.3%, CO emissions decrease by 16.2%
to 38.7%, and CO2 emissions are reduced by 32.3% to 45.1% when 10% to 20%
of H2 is premixed with the fuel, respectively. Similarly, at 2000 rpm, the cylinder
pressure increased by 3.9% to 14.5%, thermal efficiency improved by 10.4% to
27.6%, CO emissions decreased by 31.8% to 45%, and CO2 emissions were
lowered by 17.6% to 22.3% when 10% to 20% of H2 was premixed with fuel,
respectively.
Regarding to the case of diesel-hydrogen dual-fuel combustion. At 1500 rpm,
mixing 10% to 20% of H2 with the fuel results in an 14.8% to 29.3% increase in
cylinder pressure, a 12.4% to 23.2% improvement in thermal efficiency, a 28.9%
to 59.2% decrease in CO emissions, and a 6.3% to 18.3% reduction in CO2
emissions. Comparably, at 2000 rpm, when 10% to 20% of H2 was mixed with
fuel, the cylinder pressure rose by 4.1% to 15.9%, thermal efficiency climbed by
23.7% to 37%, CO emissions dropped by 57.1% to 64.2%, and CO2 emissions
came down by 25.1% to 39.1%.
Finally, hydrogen injection via the air intake manifold (AIM) to the engine will
be discussed. At 1500 rpm, adding 10% to 20% of H2 through the air intake
manifold increases cylinder pressure by 23.3% to 36.9%, improves thermal
efficiency by 13.3% to 23.2%, reduces CO emissions by 19.6% to 49.1%, and
reduces CO2 emissions by 42.8% to 57.1%. At 2000 rpm, the introduction of 10%
to 20% H2 through the air intake manifold resulted in a cylinder pressure increase
of 3.5% to 15.4%, a thermal efficiency enhancement of 32.2% to 56.3%, a
reduction in CO emissions by 45.3% to 61.8%, and a decrease in CO2 emissions
by 35.5% to 66.3%. Furthermore, due to enhanced combustion, there has been a
slight increase in NOx emissions.