Hierarchical and comparative kinetic modeling of laminar flame speeds of hydrocarbon and oxygenated fuels

Alcohol combustion chemistry

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.

Use of higher alcohol biofuels in diesel engines: A review

An experimental and chemical kinetic modeling study of 1,3-butadiene combustion: Ignition delay time and laminar flame speed measurements

The fundamental combustion and emissions properties of advanced biofuels are reviewed, and their impact on engine performance is discussed, in order to guide the selection of optimal conversion routes for obtaining desired fuel combustion properties. Advanced biofuels from second- and third-generation feedstocks can result in significantly reduced life-cycle greenhouse-gas emissions, compared to traditional fossil fuels or first-generation biofuels from food-based feedstocks. These advanced biofuels include alcohols, biodiesel, or synthetic hydrocarbons obtained either from hydrotreatment of oxygenated biofuels or from Fischer–Tropsch synthesis. The engine performance and exhaust pollutant emissions of advanced biofuels are linked to their fundamental combustion properties, which can be modeled using combustion chemical-kinetic mechanisms and surrogate fuel blends. In general, first-generation or advanced biofuels perform well in existing combustion engines, either as blend additives with petro-fuels or as pure “drop-in” replacements. Generally, oxygenated biofuels produce lower intrinsic nitric-oxide and soot emissions than hydrocarbon fuels in fundamental experiments, but engine-test results can be complicated by multiple factors. In order to reduce engine emissions and improve fuel efficiency, several novel technologies, including engines and fuel cells, are being developed. The future fuel requirements for a selection of such novel power-generation technologies, along with their potential performance improvements over existing technologies, are discussed. The trend in the biofuels and transportation industries appears to be moving towards drop-in fuels that require little changes in vehicle or fueling infrastructure, but this comes at a cost of reduced life-cycle efficiencies for the overall alternative-fuel production and utilization system. In the future, fuel-flexible, high-efficiency, and ultra-low-emissions heat-engine and fuel-cell technologies promise to enable consumers to switch to the lowest-cost and cleanest fuel available in their market at any given time. This would also enable society as a whole to maximize its global level of transportation activity, while maintaining urban air quality, within an energy- and carbon-constrained world.

A review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines

Experimental and modeling study on ignition delays of lean mixtures of methane, hydrogen, oxygen, and argon at elevated pressures

Effect of n-pentanol addition on the combustion, performance and emission characteristics of a direct-injection diesel engine

Experimental and modeling study on auto-ignition characteristics of methane/hydrogen blends under engine relevant pressure

High temperature ignition delay times of C5 primary alcohols

Experimental and numerical investigation on diluted DME flames: Thermal and chemical kinetic effects on laminar flame speeds

Liangjie Wei

Papers

Experimental and modeling study on ignition delays of lean mixtures of methane, hydrogen, oxygen, and argon at elevated pressures

Effect of n-pentanol addition on the combustion, performance and emission characteristics of a direct-injection diesel engine

Experimental and modeling study on auto-ignition characteristics of methane/hydrogen blends under engine relevant pressure

High temperature ignition delay times of C5 primary alcohols

Experimental and numerical investigation on diluted DME flames: Thermal and chemical kinetic effects on laminar flame speeds