Direct-injection Methanol Engine Research Articles

Effects of injection and spark timings on combustion, performance and emissions (regulated and unregulated) characteristics in a direct injection methanol engine

Methanol is a promising low-carbon fuel for internal combustion engines. Increasing the compression ratio combined with direct injection (DI) is an important technology to realize methanol's potential for carbon reduction. In this work, experimental investigations into the effects of injection timing and spark timing (ST) on combustion, performance, and emissions characteristics were carried out on a high compression ratio DI SI methanol engine. The experiments were performed at two intake pressure of 65 kPa and 87 kPa and a constant engine speed of 1500 rpm. The ignition delay and burn duration were slightly reduced with retarding SOI. However, the volumetric efficiency and combustion efficiency decreased rapidly with retarding SOI. The trade-off relation between the effect of SOI on NO and CO emissions was notable. However, methanol and formaldehyde emissions increased simultaneously with retarding SOI. ST retarding could mitigate the NO and CO emissions at the expense of deterioration in heat release rate, thermal efficiency, methanol and formaldehyde emissions. Overall, the combustion stability was good with all SOIs and STs but the combustion efficiency and emissions deteriorated with retarding SOI. A range of −270 to −240 °CA aTDC would be optimal for SOI to obtain good performance.

Characteristics of Evaporating Spray for Direct Injection Methanol Engine: Comparison between Methanol and Diesel Spray

In the context of global efforts to pursue carbon neutrality, the research on the application technology of methanol fuel in internal combustion engines has ushered in a new peak. In order to provide a theoretical basis for the development of direct injection methanol engines, the spray characteristics of methanol with high-pressure direct injection were studied. Based on the visualization experimental device of constant volume vessels, the diffused background-illumination extinction imaging (DBI) and schlieren methods were applied to examine the distinctions in the evaporating spray properties between methanol and diesel under different injection pressures and ambient temperature conditions. Furthermore, aiming to maximize the potential of methanol fuel in compression ignition engines, under the premise that the alternative fuel can obtain the same total fuel energy as diesel, two different injection strategies of methanol were proposed and evaluated through the coordination of the nozzle hole diameter, injection pressure and injection duration. It reveals that it is easier for methanol spray to evaporate because of the lower boiling point, which results in a shorter spray tip penetration and wider spray angle compared with those of diesel, especially under the middle-level ambient temperature (600 K) condition. These deviations are also observed under different injection pressure conditions. However, affected by the lower energy density, the strategies of injecting the same fuel energy of methanol with that of diesel prolong the methanol spray tip penetration, enlarge its spray area and sacrifice the methanol evaporation performance. It is necessary for the geometrical design of the combustion chamber to coordinate with the hole diameter and injection pressure selection to deal with the huge distinctions in the spray characteristics between methanol and diesel fuel.

Numerical study of twin-spark plug arrangement effects on flame, combustion and emissions of a medium compression ratio direct-injection methanol engine

The effects of twin-spark plug arrangement on flame, combustion and emissions of a medium compression ratio direct injection methanol engine were numerically investigated. Computational results showed that at approximately A (ratio of distance of twin-spark plug and cylinder diameter) = 0.65, the burning and exothermic were the most reasonable compared to other twin-spark plug locations. A = 1.00 was the worst twin-spark plug arrangement. The maximum in-cylinder pressure and the maximum in-cylinder temperature were decreased with increasing A. Ignition delay were increased with increasing A. The A = 0.65 had the shortest combustion duration and the maximum heat release rate. The maximum in-cylinder pressure of A = 1.00 was approximately 57.5% lower than A = 0.25. The ignition delay of A = 1.00 was approximately 2.4 times longer than A = 0.25. The combustion duration of A = 0.67 was approximately 12% and 52.2% lower than A = 0.25 and A = 1.00, respectively. Unburned methanol and soot were increased gradually with increasing A, and at the A > 0.75, the unburned methanol and soot emissions were increased rapidly as increasing A. The unburned methanol of A = 1.00 was approximately 4.6 times higher than A = 0.25. The variations in emitted NOX emissions showed opposite tendencies with the variations in unburned methanol and soot emissions. The optimum arrangement of the twin-spark plug for application of actual engine was approximately A = 0.65.

Comparative study on combustion and emissions between methanol port-injection engine and methanol direct-injection engine with H2-enriched port-injection under lean-burn conditions

Lean-burn is an effective way to improve thermal efficiency and reduce emissions of spark-ignition (SI) engines. A hydrogen (H2) enrichment combustion strategy can extend the lean-burn limits of SI engines. Two engines equipped with hydrogen and methanol dual-port injection (HPI + MPI) and hydrogen port injection plus methanol direct injection (HPI + MDI) were used to evaluate the lean-burn capability of SI engines. The lean-burn characteristics of homogeneous and stratified combustion modes were compared. The results showed that H2 addition was more conducive to extending the lean-burn limit of the direct-injection methanol engine and achieving high indicated mean effective pressure (IMEP) than the port-injection methanol engine. HPI + MDI engines with 6% H2 addition effectively extended the lean-burn limit to an excess air ratio of 2.2. H2 addition compensated for the power drop caused by the decrease in volumetric efficiency and speed up combustion under lean-burn conditions. H2 addition could also realize stable combustion under super lean-burn conditions for HPI + MDI engines. The BSHC and BSCO emissions of HPI + MPI engines were lower than those of HPI + MDI engines, but the BSNOX and soot emissions were higher. H2 addition decreases BSCO2 emissions at the same excess air ratio for both the HPI + MPI and HPI + MDI engines.

401 燃料の衝突・分散(OSKA)方式を用いた直接噴射式メタノール機関の性能向上に関する研究 : 最適燃料噴射開弁圧の検討(OS4-1 環境に対応するエンジンシステムI,オーガナイズドセッション:4 環境に対応するエンジンシステム)

401 燃料の衝突・分散(OSKA)方式を用いた直接噴射式メタノール機関の性能向上に関する研究 : 最適燃料噴射開弁圧の検討(OS4-1 環境に対応するエンジンシステムI,オーガナイズドセッション:4 環境に対応するエンジンシステム)

Engine Performance and Combustion Characteristics in a Direct-Injection Methanol Engine with Supercharging.

Effects of supercharging on a engine performance and exhaust emissions in a spark-assisted direct injection methanol engine were investigated under heavy load conditions. The test results indicated that the supercharging has the effects of improving thermal efficiency, CO and NOx emissions. The combustion analyses showed that the supercharging suppress a rapid combustion of stratified mixture which include fuel spray drop, and makes contributions to promote premixture with rapid fuel spray evaporating and fuel-air mixing. As a result, supercharging increased heat release during the premixed combustion. In addition, increasing of premixed combustion with the supercharging reduced the deterioration of brake thermal efficiency during the EGR under heavy load conditions. The supercharging with EGR can significantly reduce the NOx emissions while keeping the high thermal efficiency as direct injection diesel engines.

Study of glow plug assisted direct injection methanol engine with a three-dimensional diffusing spray (NICS-MH) ? The effect of glow plug location and squish area to engine performance and exhaust emissions Kazumasa Urushihara, Kyoko Okamoto (Nippon Institute of Technology Graduate School), Masaru Ogura (Nippon Institute of Technology)

Study of glow plug assisted direct injection methanol engine with a three-dimensional diffusing spray (NICS-MH) ? The effect of glow plug location and squish area to engine performance and exhaust emissions Kazumasa Urushihara, Kyoko Okamoto (Nippon Institute of Technology Graduate School), Masaru Ogura (Nippon Institute of Technology)

Effects of EGR on Combustion and Exhaust Gas in a Direct-Injection Methanol Engine.

An EGR was applied in a spark-assisted, direct-injection (DI) neat methanol engine. An experimental study has been carried out to analyze effects of EGR that influence brake thermal efficiency and NOx emission. The EGR on the DI methanol engine alters charge, in particular by decreasing the concentration of oxygen and increasing the concentration of unburned methanol with high charge temperature. The results of qualitative analyses show that methanol vaporization suppresses heat-release at the initial combustion stage, therefore inducing the high heat-release rates characteristics of following stages such as premixed combustion. The unburned methanol in charge was useful for the flame development during spark discharge in lower oxygen atmosphere. It was found that the brake thermal efficiency of the methanol engine with the EGR was improved almost the same as that of diesel engines at low load. NOx emissions were lower at low load by lowering the combustion temperature in the cylinders.

Combustion control of direct injection methanol engine using a combination of charge heating and exhaust gas recirculation

The feasibility of a highly efficient, low-NOx spark-assisted direct injection methanol engine has been investigated using a combination of charge heating and EGR under light load conditions. The results show that, as the charge temperature is increased, rapid premixed combustion initiated by spark ignition occurs and self-ignition of subsequent fuel spray is induced. Thus the combustion progresses rapidly in a stable state, improving the brake thermal efficiency. It was found that the oxygen concentration in the charge can be reduced by conducting EGR at high rate under high charge temperature, so that effective NOx reduction is possible.