| Summary: | 碩士 === 國立雲林科技大學 === 機械工程技術研究所 === 83 === The goal of this study is to investigate combustion characte-
ristics of fuel-air mixture in diesel engine cylinder. Actual
analyses of these simulation results,i.e.,the cylinder pressure
,average gas temperature,and fuel heat release rate, etc.,are
essential fundamental information toward fully understanding
and good prediction of engine performance in advance. Also
experimental measurements of engine pressure,torque,and power
output, etc., are another extremely useful knowledge in engine
analysis. Both simulation and experimental results have been
compared in this research to study combustion characteristics
in dieselengine which can be used for improving engine
efficiency in the engine design company.
The YAMAHA ME200F (three cylinders, 1973 CC, direct-injection)
diesel engine in the laboratory and a zero-dimensional diesel
engine simulation program (DESP) are selected to perform this
research. The engine speed, load (equivalence ratio), and fuel
injection timing are varied to study their effects on air-fuel
mixing and combustion processes in the diesel engine. The
experiments are also conducted simultaneously to measure the
engine torques in various operating conditions through cautions
appropriate experimental procedures.
The results show that the ignition delay increases almost
linearly with engine speed increasing at constant load. The
most efficient engine operating speed for ME200F diesel engine
is found to be near 2000 rpm due to the corresponding maximum
brake mean effective pressure (BMEP) and the minimum specific
fuel consumption (SFC) occurrence at this speed. As the engine
load is increased, the ignition delay is shortened slightly due
to increaseed cylinder charge temperature and pressure at time
of injection. Increasing of engine load results in a reduction
of brake spefic fuel consumption(BSFC)but a increment in bmep.
The results also show that the engine brake power increases
slowly with engine speed at high engine speed condition,
especially at low engine load cases, this is primarily due to
the quick non-proportional increment of friction force between
engine moving parts at high speed. Another parametric study
shows that if fuel injection timing is advanced, the ignition
delay will be increased because the initial air temperature and
pressure are relatively low in cylinder. According to DESP
simulation results, the engine will operate with higher brake
power output and better BMEP and SFC values at injection timing
of 29 degree BTDC than the default value of 24 degree BTDC used
in the actual engine. Thus, it is suggested that the optimum
fuel injection timing for YAMAHA ME200F diesel engine should be
at 29 degree BTDC.
The experimental results show that the engine's maximum load
φ=0.3 and φ=0.5 occurs at 500 rpm and 1000 rpm, respectively.
On the opposite, its minimum load φ=0.3 occurs at high speed
3000 rpm. The comparison of engine's torque, power output, and
BSFC between DESP program simulation results and experimental
results is found very consistent in this study.
|
|---|
