Search Results

A computer model was built and a theoretical analysis was performed to predict the behavior of a system containing Homogenous charge compression ignition (HCCI) engine and a methanol reformer. The reformer utilizes the waste heat of the exhaust gases to sustain the two subsequent processes: dehydration of methanol to dimethyl ether (DME) and water, and methanol steam reforming (SRM) where methanol and water react to mainly hydrogen, CO and CO2. Eventually, a gaseous mixture of DME, H2, CO, CO2, water (reused) and some other species is created in these processes. This mixture is used for the engine feeding. By adding water to the methanol and fixing the vaporized fuel's temperature, it is possible to manage the kinetics of chemical processes, and thus to control the products’ composition. This allows controlling the HCCI combustion.

The goal of the present work was to analyze the performance of a spark ignition engine fueled by ethanol steam reforming products. The highest reformer-ICE system efficiency and the lowest CO emissions were achieved with the ethanol steam reforming products obtained at reaction temperature of 1000K and water/ethanol ratio of 1.8. Fueling the SI engine with reformate gas made it possible to achieve the reformer-ICE system efficiency of 40% for the engine fed by SRE products compared with 34% for gasoline and 36% for ethanol. CO emissions were reduced by 3.5 and 10 times compared with ethanol and gasoline, respectively. NO emissions were decreased by about 4 times compared with the gasoline-fed engine.

A comparative theoretical analysis of the spark ignition (SI) engine performance is performed for the cases of feeding it by the reforming products of two different alcohols: ethanol and methanol. Energy efficiency of the steam reforming process, optimal reactor temperature and obtainable compositions of the reforming products are showed and analyzed for the considered two fuel types. Three compositions of the reforming products: ethanol steam reforming (SRE), methanol steam reforming (SRM) and products of the low-temperature ethanol reforming are considered as gaseous fuels in the engine performance simulations. Change in the fuel burning velocity as a function of fuel composition and air excess factor is taken into account in a modeling of the heat release process.

The dynamics of the gaseous jet is a major factor affecting the particulate matter and gaseous pollutants formation in the combustion of hydrogen or a hydrogen-rich reformate. Mitigation of particulate matter formation is essential for the sustainability of a novel high-efficiency propulsion cycle with High-Pressure Thermochemical Recuperation which has been developing in the Technion. The latter suffers from elevated particle emissions compared to hydrocarbon fuels combustion in a wide range of operating regimes. An intensified lubricant involvement in the combustion process was found to be the source of the elevated particle formation in a non-premixed reformate and hydrogen combustion. The reported research further analyzes and compares using analytical, empirical, and experimental tools the gaseous impinging underexpanded jet evolution and propagation with a focus on the lubricant vapor entrainment mechanisms from a heated cylinder wall surface into the combustion chamber bulk.

This study investigates the particle engine emission characteristics including particle-bound metals for different lubricants used in a direct injection (DI) engine fed with the hydrogen-rich reformate containing 75% mol. H2 and 25% mol. CO2. The particle number concentration, size distribution and content of trace metals in the emitted particles are measured, analyzed, and compared for the baseline gasoline-fed engine and the reformate-fed engine. The results show that for all tested lubricants the particle number and mass emission from the reformate-fueled engine are significantly higher than from the baseline gasoline-fed counterpart. Also, an ICP analysis performed on PM demonstrated that the content of trace elements from the lubricant are higher for the reformate fuel. This indicates that an excessive lubricant involvement in combustion is the reason of these findings.

In this paper we describe conversion of the gen-set gasoline-fed carburetor single-cylinder SI engine to the direct-injection version operating with the gaseous hydrogen-rich methanol reforming products, and present the first experimental results. It was found that engine feeding by methanol steam reforming products has a great potential of pollutant emissions mitigation as compared with gasoline. NOx concentrations in the exhaust gas were reduced by a factor of 7 as a result of the lean combustion and lowering in-cylinder temperatures. Particle mass emissions were mitigated to zero-impact levels. Harmful emissions of the target pollutants THC, CO and the GHG gas CO2 were reduced by a factor of 6, 25 and 1.5, respectively.