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The paper presents an analytical two-dimensional model of two-phase turbulent jets with focus on fuel sprays in internal combustion engines. The developed model allows prediction of the fuel spray parameters including local fuel concentration and mixture velocity. The model proposed in this paper is based on the single-phase steady-state laminar axisymmetric jet flow field solution by Schlichting. This solution is amended to include transport of the discontinuous fuel phase in a stagnant air in the limit of a dilute fuel concentration. This two-phase jet flow model admits a closed form analytical solution for the fuel concentration distribution. This solution is then applied to turbulent jet flow as per the approach described by Schlichting and in other studies, and used to predict point-wise properties of fuel sprays in internal combustion engines. The results of model simulations are compared with the available experimental data.

This paper describes a model for the simulation of the joint operation of internal combustion engine (ICE) with methanol reformer when the ICE is fed by the methanol steam reforming (SRM) products and the energy of the exhaust gases is utilized to sustain endothermic SRM reactions. This approach enables ICE feeding by a gaseous fuel with very favorable properties, thus leading to increase in the overall energy efficiency of the vehicle and emissions reduction. Previous modeling attempts were focused either on the performance of ICE fueled with SRM products or on the reforming process simulation and reactor design. It is clear that the engine performance is affected by the composition of the reforming products and the reforming products are affected by the exhaust gas temperature, composition and flow rate.

Various potential alternative fuels for internal combustion engines are studied nowadays to reduce dependency on fossil fuel. Hydrogen-rich reformate produced onboard as a result of fuel reforming in an internal combustion engine with a high-pressure thermochemical recuperation is a promising alternative gaseous fuel. This paper reports on the effects of the reformate fuel injection method on energy efficiency and combustion characteristics of a single-cylinder spark ignition (SI) engine with a high compression ratio (16:1) at steady-state conditions. A comparison between port (PFI) and direct (DI) reformate injection is performed. Engine performance and combustion parameters are evaluated and analyzed. For both injection strategies, a similar relatively high indicated efficiency (50%) is observed. This is a joint result of waste heat recovery and hydrogen combustion benefits.

Although many works are published about the achieved advancements in the manufacturing of the catalytic converters (CC) system for vehicle engines and their testing under laboratory conditions, there is a lack in the published research about the mileages influence on their conversion efficiency (CE). Dependence of dual-brick CCs' CE in real-world driving conditions on vehicle mileage is studied for the first time. The CC tested are dismantled from the vehicles with mileage from 0 (new one) up to 150,000 km. The studied CC are evaluated at the engine test bench containing a dynamometer coupled with a spark ignition engine suitable for this type of CC system. Measurements of CC efficiency are performed at four different engine operation regimes: two loaded regimes and two non-load regimes - low and high speed idling. It is found that the oxidation of CO and HC at all four tested regimes took place almost totally in the first CC.

Many motor vehicles (fire-fighting cars and trucks, helicopters, airplanes, etc.) are used for conflagration extinguishing purposes. It is clear that their engines aspirate air containing combustion inhibitors, which are used for flame suppression, but until now there is no available information about the influence of this fact on engine performance. This paper presents results of an experimental study on the influence of combustion inhibitors, such as Halon 1301 (CF₃Br) and CO₂, contained in the ambient air, on the performance of compression ignition (CI) and spark ignition (SI) engines. Substantial differences in the response of CI and SI engines to the inhibitor presence in the aspirated air are revealed. Starting from relatively small concentrations of CF₃Br, an increase of the CI engine speed and a simultaneous decrease of the brake specific fuel consumption are observed. The speed rise may attain up to 80% of its initial value.

This paper provides an analysis of the effect of a flight altitude on knock occurrence in reciprocating SI turbocharged engines. It presents results of the computational study aimed at investigating reasons leading to knock occurrence and methods of alleviating the knock tendency of small aircraft engines. Turbochargers are frequently used to improve the performance of aviation platforms at high altitudes. Although a turbocharger provides the benefits of increased power, improved BSFC and a downsized engine, it can result in engine knock because of increasing the intake air temperature, due to a rise in the compression ratios as the air density drops. Aerial platforms experience environmental conditions that can change drastically in a matter of a few minutes. Therefore, it is important to be aware of the combined effects of altitude, initial ground temperature, humidity, flight velocity and fuel octane numbers on the emergence of knock following takeoff.

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.

A simple, relatively short and inexpensive screening test method has been developed for evaluation of available detergent/dispersant diesel fuel additives. The screening test is based on experiments of running a laboratory diesel engine in a pre-determined regime(load cycle). The engine is a single cylinder, 4-stroke DI, naturally aspirated and air cooled. It is coupled to a generator feeding electrical heaters as the load. The test rig is controlled electronically to enable fully automatic test bench operation, including start/stop, load change, emergency shut-down, etc. The experiments were performed by running the engine on a reference base fuel and then the same fuel with different detergent additives. The nozzle of the fuel injector was checked for clogging by air flow measurements, using the ISO-4010 test rig.

At present the market of Wankel engines is limited to some special applications. This fact explains absence of commercial software products specially developed for this engine simulation and prediction of its performance. Conversely, there are available and widely used software products for simulation of reciprocating-piston engines performance. Some attempts are known in using this software for prediction of Wankel engine performance. This paper details an approach used in these attempts. Main differences between both types of engines are summarized and principles of a virtual reciprocating-piston engine compilation are developed. A method of virtual blowing was developed for assessment of discharge coefficients for intake and exhaust ports. Comparison of simulation results with the measured performance of two UAV Wankel engines showed sufficient accuracy of the suggested approach.

This study considers one of the challenges that arise during conversion of gasoline SI engines to ‘heavy fuel’ feeding - worsening engine performance because of intensive fuel film formation on inner surfaces of the intake manifold. A main goal of this study was investigation of an interaction process of a single fuel drop and a fuel jet with the impingement surface. Ultrasonic (US) oscillation of the latter was applied to prevent fuel film formation. Diesel fuel was chosen for our experiments because it causes more problems of mixture formation in SI engines. In the series of experiments with a single drop, effects of the drop size, ultrasound performance and a type of the impingement surface on the drop behavior were studied using a high-speed photography. In experiments with a fuel jet the phenomena of fuel film formation and size distribution of the impinging and reflected droplets were studied using a high-speed photography and PDPA/LDV technique.

The paper describes the principles and benefits of a novel approach aimed at homogenous charge compression ignition (HCCI) engine control with simultaneous waste heat recovery (WHR) and onboard hydrogen production. This approach is called Reforming-Controlled Compression Ignition (RefCCI) and has unique advantages compared to known HCCI control methods. The suggested RefCCI concept is analyzed using a dedicated computational model that simulates joint operation of the engine and the reformer in their mutual relationship. A kinetic model for predicting the chemical kinetics was applied in the reformer part of the computational routine and a reduced mechanism was applied for the HCCI combustion simulation. A first law analysis was performed to assess the existence of sufficient available energy for the reforming process. The reforming-controlled fuel reactivity modification enhances combustion control at various operation regimes.

Utilizing heat of exhaust gases for on-board alcohol reforming process (thermo-chemical recuperation - TCR) is a promising way of increasing the internal combustion engine (ICE) efficiency and emissions mitigation. Knowledge of the laminar burning velocity of alcohol reforming products is necessary for simulating performance of internal combustion engines with TCR and for in-depth studies of the combustion process. Laminar burning velocities of H2, CO, CO2 and CH4 mixtures that simulate methanol and ethanol steam reforming products for various water-alcohol ratios are investigated in this work. The influence of flame cellularity on burning velocity is studied as well. The burning velocity is measured experimentally using a spherical closed combustion vessel. Measurements are taken by a pressure measurement method during the pressure-rise period and prior to it by a high-speed Schlieren photography.

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.

In recent years, rotary combustion engines have experienced renewed interest as alternative power sources in various applications, due to their multi-fuel capability, simplicity, and advantageous power-to-weight, and power-to-volume ratios. Further improvements to the engine's performance require a thorough examination of its inherent shortcomings. Most prominent are its incomplete, slow combustion and lower thermal efficiency, both of which are caused by the combustion chamber's high surface-to-volume ratio and unfavorable flattened shape. Considering the difficulties involved in performing experimental measurements on rotary combustion engines, numerical simulations have proven to be valuable tools for research and development. This study presents a validated three-dimensional RANS model that simulates the flow, reaction kinetics, and heat transfer in rotary combustion engines.