Zhiyu Han

Bio: Zhiyu Han is an academic researcher from Hunan University. The author has contributed to research in topics: Diesel engine & Exhaust gas recirculation. The author has an hindex of 3, co-authored 4 publications receiving 162 citations. Previous affiliations of Zhiyu Han include Industrial Technology Research Institute.

Numerical study on the nitrogen oxide emissions of biodiesel–diesel blends in a light-duty diesel engine:

Abstract: The nitrogen oxide emissions characteristics of biodiesel–diesel blends in a light-duty diesel engine operating at a moderate load are investigated using KIVA coupled with chemical kinetics. Pure diesel, 20 vol % biodiesel–80 vol % diesel and 50 vol % biodiesel–50 vol % diesel are investigated. A reduced mechanism concerning methyl butanoate and n-heptane is applied in the combustion model. The characteristics of the combustion and nitrogen oxide emissions for different fuels are compared. The effects of the injection timing and the exhaust gas recirculation rate on the nitrogen oxide emissions are of particular interest. The results show that 50 vol % biodiesel–50 vol % diesel has the shortest ignition delay, the longest spray penetration and the lowest fuel-to-oxygen equivalence ratio at the spray tip under the same initial conditions, which results in the highest nitrogen oxide emissions. As the injection timing is retarded, the nitrogen oxide emissions of blended fuels gradually decrease. The nitrogen...

A Study on Biodiesel NOx Emission Control With the Reduced Chemical Kinetics Model

Abstract: In this paper, the effects of the start of injection (SOI) timing and EGR rate on the nitrogen oxide (NOx) emissions of biodiesel-powered diesel engine are studied with computational fluid dynamics (CFD) coupling with a chemical kinetics model. A surrogate biodiesel mechanism consisting of two fuel components is employed as the combustion model of soybean biodiesel. The in-cylinder combustion processes of the cases with four injection timings and three exhaust gas recirculation (EGR) rates are simulated. The simulation results show that the NOx emissions of biodiesel combustion can be effectively improved by SOI retardation or increasing EGR rate. The calculated NOx emissions of the cases with default EGR rate are reduced by 20.3% and 32.9% when the injection timings are delayed by 2-degree and 4-degree crank angle, respectively. The calculated NOx emissions of the cases with 24.0% and 28.0% EGR are reduced by 38.4% and 62.8%, respectively, compared to that of the case with default SOI and 19.2% EGR. But higher EGR rate deteriorates the soot emission. When EGR rate is 28.0% and SOI is advanced by 2-degree, the NOx emission is reduced by 55.1% and soot emission is controlled as that of the case with 24% EGR and default SOI.Copyright © 2013 by ASME

Use of higher alcohol biofuels in diesel engines: A review

Abstract: Biofuels have grabbed the attention of engine researchers ever since the oil-crisis and escalating costs of petro-chemicals cropped up in the ׳70s. Ethanol and methanol were the most widely researched alcohols in IC engines. However, the last decade has witnessed significant amount of research in higher alcohols due to the development of modern fermentation processes using engineered micro-organisms that improved yield. Higher alcohols are attractive second/third generation biofuels that can be produced from sugary, starchy and ligno-cellulosic biomass feedstocks using sustainable pathways. The present work reviews the current literature concerning the effects of using higher alcohols ranging from 3-carbon propanol to 20-carbon phytol on combustion, performance and emission characteristics of a wide range of diesel engines under various test conditions. The literature is abound with evidence that higher alcohols reduce carcinogenic particulate emissions that are prevalent in diesel engines. NOx emissions either increased or decreased based on the domination of either cetane number or heat of evaporation. Brake specific fuel consumption (BSFC) of the engine usually suffered due to low energy content of alcohols. A notable feature is that the combination of higher alcohols (like butanol or pentanol), high exhaust gas recirculation (EGR) rates and late injection timing enabled low temperature combustion (LTC) in diesel engines that can simultaneously reduce smoke and NOx emissions with improved engine efficiency. It can be concluded that higher alcohols reduce smoke emissions with their fuel-borne oxygen; enhance air/fuel mixing by offering long ignition delay and eventually replace fossil diesel (partially or wholly) to enable a clean and efficient combustion in compression-ignition engines. The chief thrust areas include developing mutant strains with higher yield, higher tolerance to toxic inhibition and low-cost substrates for fermentation. Further work is required in stipulating optimum blend-fuel characteristics and ensuring the long-term durability of the engines using these fuels.