Search Results

Abstract The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage.

Abstract Fluid mechanical design of the cylinder charge motion is an important part of an engine development. In the present contribution an intake port geometry is proposed that can be used as a test case for intake port flow simulations. The objective is to fill the gap between generic test cases, such as the backward facing step or the sudden expansion, and simulations of proprietary intake ports, which are barely accessible in the community. For the intake geometry measurement data was generated on a flow-through test bench and a wall-modeled LES-simulation using a hybrid RANS/LES approach for near-wall regions was conducted. The objective is to generate and analyze a reference flow case. Since mesh convergence studies are too costly for scale resolving approaches only one simulation was done, but on a very fine and mostly block-structured numerical mesh to achieve minimal numerical dissipation.

Abstract This study focused on using adsorbents to suppress engine oil deterioration as a result of the influence of biodiesel. Engine oil performance is affected by the use of biodiesel that results in short period of oil drain interval. Neat base oil, 80% blended with biodiesel, was 20% thermo oxidatively aged. Magnesium aluminum hydroxycarbonate and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-buty-4-hydroxybenzyl)benzene were applied, and the formation of oligomers in the base oil-RME mixture was monitored. The adsorbents intercept the precursors of the aging procedure and, therefore, interfere with the aging process. The analysis with FTIR showed less to no formation of oligomers. About 90% reduction in the total acid number was observed, with about 90% reduction in viscosity increment. The adsorbents, therefore, have an enhanced influence on the oxidative stability of biodiesel and its blends.

Abstract This article presents surrogate mixtures that simulate the physical and chemical properties in the auto-ignition of hydrotreated vegetable oil (HVO). Experimental investigation was conducted in the Ignition Quality Tester (IQT) to validate the auto-ignition properties with respect to those of the target fuel. The surrogate development approach is assisted by artificial neural network (ANN) embedded in MATLAB optimization function. Aspen HYSYS is used to calculate the key physical and chemical properties of hundreds of mixtures of representative components, mainly alkanes—the dominant components of HVO, to train the learning algorithm. Binary and ternary mixtures are developed and validated in the IQT. The target properties include the derived cetane number (DCN), density, viscosity, surface tension, molecular weight, and volatility represented by the distillation curve. The developed surrogates match the target fuel in terms of ignition delay and DCN within 6% error range.

Abstract A numerical study using large-eddy simulations (LES) to reproduce and understand sources of cycle-to-cycle variation (CCV) in spark-initiated internal combustion engines (ICEs) is presented. Two relevantly different spark-ignition (SI) units, that is, a homogeneous-charge slow-speed single-cylinder research unit (the transparent combustion chamber (TCC)-III, Engine 1) and a stratified-charge high-revving speed gasoline direct injection (GDI) (Engine 2) one, are analyzed in fired operations. Multiple-cycle simulations are carried out for both engines and LES results well reproduce the experimentally measured combustion CCV. A correlation study is carried out, emphasizing the decisive influence of the early flame period variability (1% of mass fraction burnt (MFB1)) on the entire combustion event in both ICEs. The focus is moved onto the early flame characteristics, and the crucial task to determine the dominant causes of its variability (if any) is undertaken.

Abstract In urban roads the engine speed and the load vary suddenly and frequently, resulting in increased exhaust emissions. In such operations, the effect of air injection technique to access the transient response of the engine is of great interest. The effectiveness of air injection technique in improving the transient response under speed transient is investigated in detail [1]; however, it is not evaluated for the load transients. Load step demand of the engine is another important event that limits the transient response of the turbocharger. In the present study, response of a heavy-duty turbocharged diesel engine is investigated for different load conditions. Three cases of load transients are considered: constant load, load magnitude variation, and load scheduling. Air injection technique is simulated and after optimization of injection pressure based on orifice diameter, its effect on the transient response is presented.

Abstract Accurate exhaust gas temperature (EGT) measurements are vital in the design and development process of internal combustion engines (ICEs). The unsteady ICE exhaust flow and thermal inertia of commonly used sheathed thermocouples and resistance thermometers require high bandwidth EGT pulse measurements for accurate cycle-resolved and mean EGTs. The EGT pulse measurement challenge is typically addressed using exposed thin-wire resistance thermometers or thermocouples. The sensor robustness to response tradeoff limits ICE tests to short durations over a few exhaust conditions. Larger diameter multiwire thermocouples using response compensation potentially overcomes the tradeoff. However, the literature commonly adopts weaker slack wire designs despite indications of coated weld taut wires being robust.

Abstract Diesel engines include systems for cooling, lubrication, and fuel injection and contain a variety of components. A malfunction in any of the engine systems or the presence of any faulty element influences engine performance and deteriorates its components. This research is concerned with the untimely appearance of vital cracks in the liners of a turbocharged heavy-duty Diesel engine. To find the root causes for premature failure, rigorous examinations through visual observations, material characterization, and metallographic investigations are performed. These include Scanning Electron Microscope (SEM) and Energy-Dispersive Spectroscopy (EDS), fracture mechanics analysis, and performance examination, which are also followed by Finite Element Moldings. To find the proper remedy to resolve the problem, drawing a precise and reliable picture of the engine’s operating conditions is required.

Abstract Increasing thermal and fuel efficiency in Internal Combustion Engines (ICEs) requires thorough investigations on the combustion process and its thermodynamics. The first law of thermodynamics expresses the balance of the energy, while the second law specifies the maximum achievable work. In this article, Low-Temperature Combustion (LTC) strategies, including Homogeneous Charge Compression Ignition (HCCI), Reactivity Controlled Compression Ignition (RCCI), Partially Premixed Combustion (PPC), and Direct Dual-Fuel Stratification (DDFS) were analyzed by the first and second law approaches, and they were compared with ideal-diesel cycle and Conventional Diesel Combustion (CDC). HCCI and RCCI had the highest exergy efficiency of 50.8% and 49.2%, respectively, compared to other cases, and exergy destruction in these cases was the lowest (25.3% and 27.5%, respectively).

Abstract Environmental protection and the depletion of nonrenewable energy sources necessitate the search for the replacement of, among others, diesel fuel (Df) in diesel engines with renewable fuel without major structural changes. For this reason, vegetable oils are of interest as a possible fuel for this type of engine. Unfortunately, the physicochemical properties of vegetable oils differ significantly from Df. In addition to the boiling and freezing points, these properties include viscosity, density, and surface tension as well as wetting properties. For this reason, an attempt was made to modify these properties by adding n-hexane (Hex) and ethanol (Et) to canola oil (Co). The viscosity, density, surface tension, and wetting properties of Hex and Et are significantly different from those for Co.

Abstract The frequency of video-capturing collision events from surveillance systems are increasing in reconstruction analyses. The video that has been provided to the investigator may not always include a clear perspective of the relevant area of interest. For example, surveillance video of an incident may have captured a pre- or post-incident perspective that, while failing to capture the precise moment when the pedestrian was struck by a vehicle, still contains valuable information that can be used to assist in reconstructing the incident. When surveillance video is received, a quick and efficient technique to place the subject object or objects into a three-dimensional environment with a known rate of error would add value to the investigation.

Abstract Neutron diffraction is a powerful tool for noninvasive and nondestructive characterization of materials and can be applied even in large devices such as internal combustion engines thanks to neutrons’ exceptional ability to penetrate many materials. While proof-of-concept experiments have shown the ability to measure spatially and temporally resolved lattice strains in a small aluminum engine on a timescale of minutes over a limited spatial region, extending this capability to timescales on the order of a crank angle degree over the full volume of the combustion chamber requires careful design and optimization of the engine structure to minimize attenuation of the incident and diffracted neutrons to maximize count rates.

Abstract To assess the effect of the presence of carbon dioxide (CO2) in natural gases on the knock resistance of fuel, the knock behavior of a lean-burn, high-speed medium Brake Mean Effective Pressure (BMEP) Combined Heat and Power (CHP) engine fueled with CH4 + 8 mole% C3H8 mixtures. The engine experiments are supplemented with ignition measurements and simulations of ignition and cylinder processes for various fuel compositions. The engine results show that increasing the fraction of CO2 results in an increase in knock resistance. The analysis of simulations of cylinder processes shows that for binary mixtures (CH4/CO2) and ternary mixtures (CH4/C3H8/CO2) the increase in knock resistance with increasing CO2 fraction is caused by the reduction in peak pressure/temperature, which consequently increases the autoignition delay time of the mixture.

Abstract The article describes the results achieved in developing a new diesel combustion system for passenger car application that, while capable of high power density, delivers excellent fuel economy through a combination of mechanical and thermodynamic efficiencies improvement. The project stemmed from the idea that, by leveraging the high fuel injection pressure of last generation common rail systems, it is possible to reduce the engine peak firing pressure (pfp) with great benefits on reciprocating and rotating components’ light-weighting and friction for high-speed light-duty engines, while keeping the power density at competitive levels. To this aim, an advanced injection system concept capable of injection pressure greater than 2500 bar was coupled to a prototype engine featuring newly developed combustion system. Then, the matching among these features has been thoroughly experimentally examined.

Abstract Combustion engines and liquid fuels are likely to continue playing a central role in freight transportation with renewable fuels reducing carbon emissions. Ethanol and methanol are future renewable fuels with a knock resistance that make them suitable for heavy-duty (HD) spark ignition (SI) engines. This simulation work focuses on the potential for improving the efficiency of an ethanol- and methanol-fueled HD SI engine using early intake valve closing Miller valve timing. With Miller valve timing, the expansion ratio and thermodynamic efficiency can be increased while maintaining the same effective compression ratio. However, Miller timing requires increased boost pressure to retain the same trapped air mass and also suffers from reduced in-cylinder turbulence.

Abstract Different aftertreatment systems consisting of a combination of selective catalytic reduction (SCR) and SCR catalyst on a diesel particulate filter (DPF) (SCR-F) are being developed to meet future oxides of nitrogen (NOx) emissions standards being set by the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). One such system consisting of a SCRF® with a downstream SCR was used in this research to determine the system NOx reduction performance using experimental data from a 2013 Cummins 6.7L ISB diesel engine and model data. The contribution of the three SCR reactions on NOx reduction performance in the SCR-F and the SCR was determined based on the modeling work. The performance of a SCR was simulated with a one-dimensional (1D) SCR model. A NO2/NOx ratio of 0.5 was found to be optimum for maximizing the NOx reduction and minimizing NH3 slip for the SCR for a given value of ammonia-to-NOx ratio (ANR).

Abstract The present study evaluates the effect of engine speed, exhaust gas recirculation (EGR), and compression ratio on conventional diesel combustion (CDC) and two isobaric combustion cases, by utilizing multiple injection strategies. The experiments were conducted in a Volvo D13C500 single-cylinder, heavy-duty engine, fuelled with standard European Union (EU) diesel fuel. The engine was operated at three different speeds of 1200, 1500, and 1800 revolutions per minute (rpm). For each engine speed and combustion cases, the EGR rate was varied from 0% to 40%. The low-pressure isobaric combustion (IsoL) and high-pressure isobaric combustion (IsoH) were maintained at peak cylinder pressure (PCP) of 50 and 68 bar, respectively, which was representative of the peak motoring pressure (PMP) and PCP of CDC. This was possible by adjusting the intake air pressure to 1.7 and 2.3 bar—absolute for IsoL and IsoH, respectively, at 1200 rpm.

Abstract The causes of failure due to cracking in the resistance spot welding of the advanced high-strength steels dual-phase 590 (DP590) were investigated using scanning electron microscopy (SEM), optical microscopy, and the tensile-shear test. The results showed that by increasing the current amount, the formation of the melting zone occurred in the heat-affected zone, leading to the cracking in this area, reducing the tensile strength and decreasing the mechanical properties; the initiation and growth of cracking and failure in this region also happened. In the heat-affected zone, by increasing the current amount with the softening phenomenon, the recrystallized coarse grains also occurred, eventually resulting in the loss of mechanical properties. The results of the tensile-shear test also indicated that by increasing the current up to 12 kA, the strength was raised, but the ductility was reduced.

Abstract This study implements Flame Image Velocimetry (FIV), a diagnostic technique based on post-processing of high-speed soot luminosity images, to show the in-flame flow field development impacted by after-injection in a single-cylinder, small-bore optical diesel engine. Two after-injection cases with different dwell times between the main injection and after-injection, namely, close-coupled and long-dwell, as well as a main-injection-only case are compared regarding flow fields, flow vector magnitude, and turbulence intensity distribution. For each case, high-speed soot luminosity movies from 100 individual combustion cycles are recorded at a high frame rate of 45 kHz for FIV processing. The Reynolds decomposition using a spatial filtering method is applied to the obtained flow vectors so that bulk flow structures and turbulence intensity distributions can be discussed.

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