Effect of Spark Timing on Performance and Emissions of a Small Spark Ignition Engine with Dual Ethanol Fuel Injection

Abstract

Ethanol as a renewable fuel has been used widely in vehicles. Dual fuel injection is one of the new techniques in development for increasing the engine's thermal efficiency and reducing the pollutant emissions. This study reports experimental investigation to the dual ethanol fuel injection with a focus on the effect of spark timing on the engine performance at different volumetric ratios of ethanol directly injected to ethanol port injected. Experiments were conducted on a single cylinder 250cc spark ignition engine at two engine loads and 3500 RPM. The spark timing was varied from 15 to 42 CAD bTDC at the light load and from 15 to 32 CAD bTDC at the medium load, while the volumetric ratio of direct injection (DI%) was varied from 0% to 100%. Experimental results showed that DI100%, the best indicated mean effective pressure (IMEP) and thermal efficiency occurred at around 30 CAD bTDC at the light load and 23 CAD bTDC at the medium load, which were the minimum spark advance for the best torque (MBT). At MBT spark timing, the IMEP at DI56% and light engine load was 8.28% greater than that at 15 CAD bTDC which was the original spark timing set by the manufacturer, and the combustion duration (CA10-90%) was 41.8% shorter. These results were attributed to the improved combustion phase associated with the increased combustion pressure and temperature when the spark timing was advanced. However, the indicated specific hydrocarbon and carbon monoxide emissions increased with advanced spark timing and increased DI ratio. These could be caused by local rich mixture formed by fuel impinged to the chamber walls and the ethanol's cooling effect associated with the direct injection. On the other hand, because of the charge cooling effect of DI, the indicated specific nitric oxide emission decreased with increased DI ratio. At MBT timing and light load, the indicated specific nitric oxide emission decreased by 37.53% at DI56% and 67.39% at DI100% compared to port injection only.

Comparative Assessment of Spray Behavior, Combustion and Engine Performance of ABE-Biodiesel/Diesel as Fuel in DI Diesel Engine

“…All neat biodiesel and ABE-biodiesel/diesel blends presented lower CO emissions at all engine speeds due to the high oxygen content (Figure 13). This result agrees with previous work [34][35][36][37]. Moreover, the oxygen content of ABE-Bd blend was higher than biodiesel resulting in a significant reduction in CO emissions compared to neat biodiesel and ABE-diesel blends.…”

“…ABE-biodiesel blends increased the UHC emissions due to the high oxygen atom (biodiesel and ABE), which altered the electronic structure. Almost all the C-H bonds of the ABE-Bd blend are less active for reaction compared to hydrocarbon fuels (fossil fuels), which means more time is required to complete the reaction and increases UHC emissions [36,37]. UHC emissions were reduced by 13% when ABE was added to diesel.…”

Effects of direct injection timing associated with spark timing on a small spark ignition engine equipped with ethanol dual-injection

“…The fuel heating value was fixed at around 420 J/cycle at light load and 610 J/cycle at medium load. The spark timing was swept from 19 to 25 CAD bTDC (denoted by ST'XX' 173 hereafter) at light load and from ST28 to ST34 at medium load, as they were the spark timings to produce the maximum output power [37]. At each spark timing, DI timing was varied from 330 CAD bTDC to 240 CAD bTDC (denoted by DIT'XXX' hereafter) before the intake valve was closed (early DI timing), and from DIT120 to DIT60 after the intake valve closed (late DI timing).…”

“…Figure 11 (a) shows that the ISNO decreases with retarded spark timing in the light and medium load conditions. This could be attributed to the smaller gas temperature due to the phase change of combustion when spark timing is retarded [37].…”

Performance of Combustion and Emissions Characteristics of Ethanol Dual Injection Spark Ignition Engine

“…In this work, the MBT window for this DualEI engine was experimentally determined at four sparks and DI timings, which are more likely to produce the maximum output power with the best combustion quality [30]. The DI timings (DIT) were set directly after the exhaust valve closed, which were DIT240, DIT270, DIT300, and DIT330.…”