Effect Of Hydrogen On Combustion And Emission Of Direct Injection Methanol Engine

As the oil resource being consumed quickly and environmental problemsbecoming serious, all countries in the world should choose right path of automotivedevelopment based on their own technical infrastructure and resources. China’senergy structure provides a superexcellent opportunity for the development ofmethanol fuel which can be used as a transition one from traditional energy to newenergy. However, methanol engines have high unregulated emissions and difficultiesin cold start. Therefore, hydrogen, which is equipped with excellent combustioncharacteristic, can provide a new idea to improve combustion and emissionsperformance of methanol engine. Meanwhile the problems that exist in theapplication of methanol engine can be solved by adding hydrogen.Based on the latest methanol oxidation reaction mechanism where is combinedwith the NOXreaction mechanism, this paper explored the effect of hydrogen on themethanol oxidation reaction mechanism with the help of premix subroutine inChemkin which is large chemical reaction dynamics analysis software, and studiedeffect of hydrogen on main intermediate products and final products in the methanolpremixed laminar flame under the given initial conditions such as temperature,pressure. Then coupling the detailed mechanism with methanol engine3D modelthrough software AVL-FIRE, combustion and emission parameters have beenresearched in the methanol engine when adding hydrogen in different volume ratio.At last, the research is focused on how excess air coefficient and the ignition timeinfluence the combustion and emissions performance in methanol engine with theaddition of hydrogen after comparing the addition of0%hydrogen and5%hydrogen.Conclusions are as follows:1. In methanol premixed laminar flame, the addition of hydrogen can acceleratethe rate of methanol oxidation reaction, and the reaction rate increased with theincrement of adding hydrogen; Adding hydrogen results in the increase of H, O, andOH radicals which can accelerate the rate of chemical reaction in the flame; Whenadding less than of5%hydrogen, intermediate hydrogen plays a main role in thereaction, when blending ratio of hydrogen is more than5%, the reactants hydrogenplays a major role in the reaction; The maximum mole fraction of CH2O decreaseswith the increment of adding hydrogen, which shows that the addition of hydrogen can reduce CH2O effectively and has positive significance to the environment;Temperature has little effect on the formation of NO in the methanol-hydrogenpremixed laminar flame, the mole fraction of NO goes down with the increment ofadding hydrogen.2. The coupling calculation results show that with the increase of hydrogenproportion maximum heat release rate and highest temperature in cylinder increases;maximum cylinder pressure increases and its corresponding crank angle advances.As for emissions, CO, unburned methanol and formaldehyde decrease, NO increasewith the increase of hydrogen blending ratio.3. The combustion and emissions performance have been studied in methanolengine after comparing the addition of0%hydrogen and5%hydrogen. It turns outthat the change of combustion and emissions parameters in the methanol engine stillfollow the effect of hydrogen proportion on it when mixed5%hydrogen and0%hydrogen in different excess air coefficient. It also shows that maximum cylinderpressure and highest temperature in cylinder, whether mixed hydrogen or not,decreases with the increase of excess air coefficient. As for emissions, CO, unburnedmethanol and formaldehyde increase, while NO decrease with the increase of excessair coefficient.4. The combustion and emissions performance have been studied in methanolengine after comparing the addition of0%hydrogen and5%hydrogen. The resultsshow that the effect of hydrogen proportion on combustion and emissions in themethanol engine can still work when mixed5%hydrogen and0%hydrogen indifferent ignition time. It also reveals that maximum cylinder pressure and highesttemperature in cylinder, whether mixed hydrogen or not, decreases with the ignitiontime delays. As for emissions, CO, unburned methanol and formaldehyde go up, NOdecrease with the ignition time delays.