(6dw) Experiment on the Performance of Natural Gas/Methanol Dual-Fuel Engine

Research Interests: Performance
of Natural Gas/Methanol Dual-fuel Engine

Teaching Interests: Power Engineering and Engineering Thermophysics

Experiment
on The Performance of Natural Gas/Methanol Dual-fuel Engine

Q Zhang, Z Chen, K Zeng

Institute of the Internal Combustion Engine, Xi¡¯an Jiaotong University, Xi¡¯an, Shaanxi 710049, China

Natural gas is widely used as an alternative energy for
internal combustion engines because of its advantages in reducing emissions. However, under lean and light load conditions,
relatively low laminar flame speed of natural gas also causes large cyclic
fluctuations and combustion instability. Natural gas/methanol
dual-fuel engine can well solve those shortcomings since methanol has several advantages
such as bigger octane number, higher latent heat of vaporization as well as higher
laminar flame speed. Thus, using methanol as fuel additives for natural gas
engines is of great significance for accelerating the combustion speed,
reducing emissions and improving the thermal efficiency. However, the performance test on the methanol/methane
dual fuel engine is still limited.

The internal combustion engine, used in this experiment,
was a 6-cylinder natural gas engine. Natural gas is injected from
10 nozzles into the intake manifold premixer at an
injection pressure of 8 bar. A set of methanol supply
system is added to the original natural gas engine. Methanol fuel rail
maintains injection pressure of 5 bar. Six methanol nozzles are installed near
the intake manifold of each cylinder. The ECU of the dual fuel engine collects
crankshaft signals, camshaft signals, intake air temperature and pressure signals,
water temperature and oil temperature signals, as well as accelerator pedal
signals. Through the calculation of ECU, the opening degree of the throttle
valve, the injection pulse width of the natural gas and the injection timing,
the injection pulse width of the methanol and the injection timing, as well as
the ignition advance angle are finally obtained. These parameters are very
important for the control of dual fuel engines. We studied the relationship
between the power performance, combustion and emission performance and the
methanol substitution rate, under different air-fuel ratios. The effects of different methanol injection angles on the
power performance, combustion and emissions performance are studied. Besides, the
effects of different alcohol fuels, such as methanol, ethanol and propanol,
were also investigated.

Experiment results show that the addition of methanol
increases the pressure in cylinder and advances the phase at which the highest
pressure occurs, which means that the moment of combustion occurs earlier. Apart
from that, with the increasing of methanol substitution rate, unburned
hydrocarbon emissions decrease while the emissions of nitrogen oxides increase.
But the change in carbon monoxide emissions are not obvious. If methanol is injected at the
intake valve opening time, it is directly injected into cylinder. Thus,
methanol can easily form delamination in the cylinder. Since the natural gas is
pre-mixed with the air before the throttle and then enters cylinder, it is more
evenly distributed within the cylinder. If methanol is injected at the time of
intake valve closing, methanol will enter the cylinder in the next cycle, so
the mixture of methanol and natural gas/air can be uniformly mixed.