| Effects of Varying Equivalence Ratios on the Combustion Efficiency Characteristic of a Dual-fuel Compression Ignition Engine by Changing Intake Pressures and Exhaust Gas Recirculation Rates
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| Jeong-Woo Lee 1, Sanghyun Chu 2, Jaegu Kang 2, Kyoungdoug Min 2 |
1Chungnam National University
2Seoul National University |
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| ABSTRACT |
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In general, a leaner mixture condition improves combustion effi ciency in compression ignition (CI) combustion using diesel.
However, in the case of leaner air–fuel mixture conditions, it disturbs fl ame propagation in spark ignition combustion
using gasoline, i.e., low reactivity fuel, causing a decrease in combustion effi ciency. Since dual-fuel combustion in a CI
engine typically involves the use of high- and low-reactivity fuels together, the diff ering reactivity conditions in the cylinder
become as important as the local equivalence ratio in the cylinder. Thus, there is a need to verify the eff ect of a leaner mixture
condition on combustion effi ciency in dual-fuel CI combustion. For this reason, this study experimentally evaluates the
eff ects of varying equivalence ratios on the combustion effi ciency of gasoline/diesel dual-fueled CI combustion in a 0.4-L
single-cylinder engine under low-speed (1500 rpm) and low-load (total LHV 570 J/str) conditions. To vary the equivalence
ratios, intake pressures and exhaust gas recirculation (EGR) rates were, respectively, changed under the part-load condition.
The results emphasize that as the equivalence ratio becomes leaner by increasing the intake pressure, combustion effi ciency
worsens due to the low reactivity properties and certain fl ame propagation modes of gasoline combustion. On the contrary,
increasing the EGR rate did not signifi cantly infl uence combustion effi ciency, but it eff ectively helped reduce nitrogen oxide
(NOx) emissions. Based on these results, it is concluded that optimizing dual-fuel CI combustion to suppress NOx emissions
is better achieved using EGR, rather than creating a leaner mixture condition.
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| Key Words:
Combustion loss · Dual-fuel combustion · Equivalence ratio · Exhaust gas recirculation (EGR) · Intake pressure · Reactivity
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Corresponding Author.
Kyoungdoug Min , Email. 
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