different initial loads, ranging from 11% to 88% of the full load with
an 11% increment. At each test point, the period of operation was
maintained for about 4 min long, and experimental data was the
weighted average of the data stream. All experiments were
performed at a constant engine speed of 1400 r/min throughout
the test, as 1400 r/min was the speed at which the maximum
torque was achieved. Peak pressure rise rate (PPRR) of 1.5 MPa/
CA and peak cylinder pressure (PCP) of 15 MPa were set
separately as the upper limits of roar combustion and engine
knock, which are the tolerable limits for the engine designed. Limit
of PPRR is controlled due to engine noises, and limit of PCP is
controlled due to mechanical stress. Misfire bound was defined
as misfire cycles occurred on combustion analyzer. If the engine
output torque stopped increasing while fumigated methanol was
still added on, we considered that the DMDF combustion had
reached its partial burn limit because that the excess methanol
was emitted into the exhaust pipe. Based on the engine load and
the mass consumption rates of diesel and methanol, the BTE and
MSP can be calculated by using Eqs. (1) and (2) respectively [17].
Brake thermal efficiency (BTE):
different initial loads, ranging from 11% to 88% of the full load withan 11% increment. At each test point, the period of operation wasmaintained for about 4 min long, and experimental data was theweighted average of the data stream. All experiments wereperformed at a constant engine speed of 1400 r/min throughoutthe test, as 1400 r/min was the speed at which the maximumtorque was achieved. Peak pressure rise rate (PPRR) of 1.5 MPa/CA and peak cylinder pressure (PCP) of 15 MPa were setseparately as the upper limits of roar combustion and engineknock, which are the tolerable limits for the engine designed. Limitof PPRR is controlled due to engine noises, and limit of PCP iscontrolled due to mechanical stress. Misfire bound was definedas misfire cycles occurred on combustion analyzer. If the engineoutput torque stopped increasing while fumigated methanol wasstill added on, we considered that the DMDF combustion hadreached its partial burn limit because that the excess methanolwas emitted into the exhaust pipe. Based on the engine load andthe mass consumption rates of diesel and methanol, the BTE andMSP can be calculated by using Eqs. (1) and (2) respectively [17].Brake thermal efficiency (BTE):
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