Search Results

Abstract In view of the combustion efficiency and emission performance, various new clean combustion modes put forward higher requirements for the performance of the fuel injection system, and the cavitating two-phase flow characteristics in the injector nozzle have a significant impact on the spray atomization and combustion performance. This article comprehensively discusses and summarizes the factors that affect cavitation and the effectiveness of cavitation, and presents the research status and existent problems under each factor. Among them, viscosity factors are a hot research topic that researchers are passionate about, and physical properties factors still have the value of further in-depth research. However, the importance of material surface factors ranks last since the nozzle material was determined. Establishing a more comprehensive cavitation–atomization model considering various factors is the focus of research on cavitation phenomena.

Abstract The transportation industry is currently in a transition toward the use of zero-emission vehicles; however, reaching it will take a considerable amount of time. In the meantime, a diesel powertrain will remain the workhorse for most heavy-duty transportation. In order to reduce the engine’s environmental impact, biofuels, such as biodiesel, are used as drop-in fuels or fuel blends. The use of drop-in fuels may create challenges for the fuel system since sticky deposits can precipitate and cause injector malfunctioning or premature fuel filter plugging. It has been concluded in the past that these deposits have been caused by soft particles. In this article, soft particles created through the degradation of biodiesel and their effect on filters are studied. The article aims to analyze fuel filters and investigate the materials responsible for soft particle separation. The study includes three pre filters and three main filters that are commercially available truck filters.

Abstract With the increased use of low ignition quality fuels in advanced compression ignition engines, the extended ignition delay and two-stage ignition behavior shown on the measured in-cylinder pressure profile raise a question about at what point of the pressure trace should be identified as the start of combustion (SOC). Previous studies used numerous methods, but a systematic evaluation is lacking, particularly for low ignition quality fuels used in a small-bore engine. The present study bridges this gap by performing high-speed imaging of OH* chemiluminescence in a small-bore optical compression ignition engine, against which various methods of ignition delay calculation are assessed for a correct representation of the start of high-temperature reaction—i.e., the actual SOC.

Abstract This article serves as a proof-of-concept and feasibility analysis regarding a variable compression ratio (VCR) engine design utilizing an exhaust valve opening during the compression stroke to vary the compression ratio instead of the traditional method of changing the cylinder or piston geometry patented by Ford, Mercedes-Benz, Nissan, Peugeot, Gomecsys, et al. [1]. In this concept, an additional exhaust valve opening was used to reduce the virtual compression ratio of the engine, without geometric changes. A computational fluid dynamic model in ANSYS Forte was used to simulate a single-cylinder, cold flow, four-stroke, direct injection engine cycle. In this model, the engine was simulated at a compression ratio of 10:1. Then, the model was modified to a compression ratio of 17:1. Then, an additional valve opening at the end of the compression stroke was added to the 17:1 high compression model.

Abstract Numerical simulation represents a fundamental tool to support the development process of new propulsion systems. In the field of large-bore dual-fuel (DF) engines, the engine simulation by means of fast running numerical models is nowadays essential to reduce the huge effort for testing activities and speed up the development of more efficient and low-emissions propulsion systems. However, the simulation of the DF combustion by means of a zero-dimensional/one-dimensional (0D/1D) approach is particularly challenging due to the combustion process evolution from spray autoignition to turbulent flame propagation and the complex interaction between the two fuels. In this regard, in this activity a 0D/1D multi-zone DF combustion model was developed for the simulation of the combustion process in large-bore DF engines.

Abstract A modelling tool has been developed for the prediction of fuel effects on the performance and exhaust emissions of a heavy-duty diesel engine. Recurrent neural network models with duty-cycle, engine control, and fuel property parameters as inputs were trained with transient test data from a 15-liter heavy-duty diesel engine equipped with a common-rail fuel injection system and a variable geometry turbocharger. The test fuels were formulated by blending market diesel fuels, refinery components, and biodiesel to provide variations in preselected fuel properties, namely, hydrogen-to-carbon (H/C) ratio, oxygen-to-carbon (O/C) ratio, derived cetane number (CN), viscosity, and mid- and end-point distillation parameters. Care was taken to ensure that the correlation between these fuel properties in the test fuel matrix was minimized to avoid confounding model input variables.

Abstract Optical combustion phenomena investigation is a common tool for passenger car and automotive engines. Large-bore engines for stationary and mobile applications, on the other hand, have a lower optical examination density. This is mainly due to the technically more complex design of the optical accesses that have to provide a larger field of view and withstand high mechanical and thermal loads. Nevertheless, an optical investigation of in-cylinder phenomena in large-bore engines is essential to optimize efficient and environmentally friendly combustion processes using new sustainable e-fuels. To realize a simple optical access with maximum observability of the combustion chamber, a fisheye optic for the direct integration into internal combustion engines was developed and used for in-cylinder Mie-scattering investigations of diesel and Oxymethylene Ether (OME3-5) pilot fuel spray of natural gas dual-fuel combustion processes in a MAN 35/44DF single-cylinder research engine.

Abstract Gasoline compression ignition (GCI) is a promising combustion technology that can help the commercial transportation sector achieve operational flexibility and meet upcoming criteria pollutant regulations. However, high-pressure fuel injection systems (>1000 bar) are needed to enable GCI and fully realize its benefits compared to conventional diesel combustion. This work is a continuation of previous durability studies that identified three key technical risks after running gasoline-like fuel through a heavy-duty, common rail injection system: (i) cavitation damage to the inlet check valve of the high-pressure pump, (ii) loss of injector fueling capacity, (iii) cavitation erosion of the injector nozzle holes. Upgraded hardware solutions were tested on a consistent 400- to 800-hour NATO durability cycle with the same gasoline-like fuel as previous studies. The upgraded pump showed no signs of abnormal wear or cavitation damage to the inlet check valve.

Abstract Interactions between fuel sprays and stepped-lip diesel piston bowls can produce turbulent flow structures that improve efficiency and emissions, but the underlying mechanisms are not well understood. Recent experimental and simulation efforts provide evidence that increased efficiency and reduced smoke emissions coincide with the formation of long-lived, energetic vortices during the mixing-controlled portion of the combustion event. These vortices are believed to promote fuel-air mixing, increase heat-release rates, and improve air utilization, but they become weaker as main injection timing is advanced nearer to the top dead center (TDC). Further efficiency and emissions benefits may be realized if vortex formation can be strengthened for near-TDC injections. This work presents a simulation-based analysis of turbulent flow evolution within a stepped-lip combustion chamber.

Abstract Electric heavy-duty tractor-trailers (EHDTT) offer an important option to reduce greenhouse gases (GHG) for the transportation sector. However, to increase the range of the EHDTT, this effort investigates critical vehicle design features that demonstrate a gain in overall freight efficiency of the vehicle. Specifically, factors affecting aerodynamics, rolling resistance, and gross vehicle weight are essential to arrive at practical input parameters for a comprehensive numerical model of the EHDTT, developed by the authors in a subsequent paper. For example, drag reduction devices like skirts, deturbulators, vortex generators, covers, and other commercially available apparatuses result in an aggregated coefficient of drag of 0.367. Furthermore, a mixed utilization of single-wide tires and dual tires allows for an optimized trade-off between low rolling resistance tires, traction, and durability.

Abstract Recently, electric heavy-duty tractor-trailers (EHDTTs) have assumed significance as they present an immediate solution to decarbonize the transportation sector. Hence, to illustrate the economic viability of electrifying the freight industry, a detailed numerical model to estimate the battery capacity for an EHDTT is proposed for a route between Washington, DC, to Knoxville, TN. This model incorporates the effects of the terrain, climate, vehicular forces, auxiliary loads, and payload in order to select the appropriate motor and optimize the battery capacity. Additionally, current and near-future battery chemistries are simulated in the model. Along with equations describing vehicular forces based on Newton’s second law of motion, the model utilizes the Hausmann and Depcik correlation to estimate the losses caused by the capacity offset of the batteries. Here, a Newton-Raphson iterative scheme determines the minimum battery capacity for the required state of charge.

Abstract Early single-injection premixed charge compression ignition (PCCI) strategies in compression ignition engines have been widely studied as a promising solution to meet the ever-increasing stringent emissions regulations. Although their application to diesel engines may provide several upsides (such as a massive and simultaneous reduction of NOx and soot engine-out emissions), especially at low to medium loads, several drawbacks, including an excessive amount of engine-out carbon monoxide (CO) and unburned hydrocarbons (HC) as well as intense combustion noise (CN), usually reveal to be major constraints. As a matter of fact, PCCI combustion systems are not yet consolidated enough for practical applications, although intensive research has been carried out to overcome its common limitations. Indeed, further research is still required.

Abstract Homogeneous charge compression ignition (HCCI) is a potential contender to replace conventional diesel combustion due to higher thermal efficiency along with near-zero oxides of nitrogen (NOx) and soot emissions. Commercial adaptation of HCCI strategy in automotive engines demands addressing problems associated with narrow operating load range and higher unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. This article intends to address these problems through fuel modifications. A production light-duty diesel engine used for agricultural water pumping applications is modified to run in the HCCI mode through suitable modifications in the intake system. To improve external mixture preparation with low volatile diesel fuel, a high-pressure fuel injection system and a fuel vaporizer are utilized in the intake manifold.

Abstract Due to their high strength and good flexibility, wire ropes are widely used in various intense applications. A wire rope will present complex wave mechanics, especially under impact conditions. In this article, wire ropes (steel core rope and hemp core rope alternately twisted) were used to study the wave dynamic response of steel wire ropes with preload shock. The transmission law of wire rope shock waves was obtained through actual measurements. The results showed that the compression wave and shear wave were generated and propagated along the rope after impact. The conduction of shear waves had significant reflection characteristics, and the reflected waves overlapped with each other. The conduction velocity of the impact shear wave of the steel core wire rope increased with increasing pretension. The peak tension caused by impact decayed exponentially.

Abstract CNG is at present retaining a growing interest as a factual alternative to traditional fuels for SI engines, thanks to its high potentials in reducing the engine-out emissions. Increasing thrust into the exploitation of NG in the transport field is in fact produced by the even more stringent emission regulations that are being introduced into the worldwide scenario. Moreover, the transport sector accounts for the 27% of the overall energy consumptions and up to the 13% in terms of global emissions. The present paper aims at deeply investigating into the potentials of a heavy-duty engine running on CNG and equipped with two different injection systems, an advanced single point (SP) one and a prototype multi-point (MP) one. The considered 7.8-liter engine was designed and produced to implement a SP strategy and hence modified to run with a dedicated MP system.

Abstract In modern diesel fuel a proportion of biodiesel is blended with petro-diesel to reduce environmental impacts. However, it can adversely affect the operation of nonwoven coalescing filter media when separating emulsified water from diesel fuel. This can be due to factors such as increasing water content in the fuel, a reduction in interfacial tension (IFT) between the water and diesel, the formation of more stable emulsions, and the generation of smaller water droplets. Standard water/diesel separation test methods such as SAE J1488 and ISO 16332 use monoolein, a universal surface-active agent, to simulate the effects of biodiesel on the fuel properties as part of water separation efficiency studies. However, the extent to which diesel/monoolein and diesel/biodiesel blends are comparable needs to be elucidated if the underlying mechanisms affecting coalescence of very small water droplets in diesel fuel with a low IFT are to be understood.

Abstract The development of a future hydrogen energy economy will require the development of several hydrogen market and industry segments including a hydrogen-based commercial freight transportation ecosystem. For a sustainable freight transportation ecosystem, the supporting fueling infrastructure and the associated vehicle powertrains making use of hydrogen fuel will need to be co-established. This article introduces the OR-AGENT (Optimal Regional Architecture Generation for Electrified National Transportation) tool developed at the Oak Ridge National Laboratory, which has been used to optimize the hydrogen refueling infrastructure requirements on the I-75 corridor for heavy-duty (HD) fuel cell electric commercial vehicles (FCEV).

Abstract Late-cycle soot oxidation in heavy-duty (HD) diesel engine low-swirl combustion was investigated using single-cylinder engine and spray chamber experiments together with engine combustion simulations. The in-cylinder flow during interactions between adjacent flames (flame-flame events) was shown to have a large impact on late-cycle combustion. To modify the flame-flame flow, a new piston bowl shape with a protrusion (wave) was designed to guide the near-wall flow. This design significantly reduced soot emissions and increased engine thermodynamic efficiency. The wave’s main effect was to enhance late-cycle mixing, as demonstrated by an increase in the apparent rate of heat release after the termination of fuel injection. Combustion simulations showed that the increased mixing is driven by enhanced flow re-circulation, which produces a radial mixing zone (RMZ).

Abstract Previous studies have shown that injector aging adversely affects the diesel engine spray formation and combustion. It has also been shown that the oxygenated fuel additive tripropylene glycol monomethyl ether (TPGME) can lower soot emissions. In this study, the effects of injector aging and TPGME on the late-cycle oxidation of soot were investigated using laser diagnostic techniques in a light-duty optical diesel engine at two load conditions. The engine was equipped with a quartz piston with the same complex piston geometry as a production engine. Planar laser-induced incandescence (LII) was used to obtain semiquantitative in-cylinder two-dimensional (2D) soot volume fraction (fv ) distributions using extinction measurements. The soot oxidation rate was estimated from the decay rate of the in-cylinder soot concentration for differently aged injectors and for cases with and without TPGME in the fuel.

Abstract Driving schedule of every vehicle involves transient operation in the form of changing engine speed and load conditions, which are relatively unchanged during steady-state conditions. As well, the results from transient conditions are more likely to reflect the reality. So, the current research article is focused on analyzing the biofuel-like lemon peel oil (LPO) behavior under real-world transient conditions with fuel injection parameter MAP developed from steady-state experiments. At first, engine parameters and response MAPs are developed by using a response surface methodology (RSM)-based multi-objective optimization technique. Then, the vehicle model has been developed by incorporating real-world transient operating conditions. Finally, the developed injection parameters and response MAPs are embedded in the vehicle model to analyze the biofuel behavior under transient operating conditions.