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SAE International Journal of Engines
SAE International, Inc.
SAE International Journal of Engines

SAE International, Inc.

1946-3936

SAE International Journal of Engines/Journal SAE International Journal of EnginesEIESCI
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    The Application of Flame Image Velocimetry to After-injection Effects on Flow Fields in a Small Bore Diesel Engine

    Yang, JinxinRao, Lingzhede Silva, CharithaKook, Sanghoon...
    13页
    查看更多>>摘要：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 from100 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. The results show significant after-injection-induced flow structures as a group of vectors travelling back toward the center of the combustion chamber upon the jet impingement on the piston bowl wall and then jet-to-jet collision. Despite higher cyclic variations caused by the after-injection, increased bulk flow magnitude and turbulence intensity upon the after-injection event suggests locally enhanced mixing. Compared to the long-dwell after-injection, the close-coupled after-injection shows more significant turbulence enhancements.
      原文链接:
    • NSTL
    • Sae Int

    Misfire Behavior and Mitigations of Passive Pre-chambers at Low-Load Operation in an Optically Accessible Gasoline Engine

    Lee, Dong EunSwanson, ChristopherYu, XinQiao, Li...
    14页
    查看更多>>摘要：An experiment has been developed to investigate the passive pre-chamber jet ignition process in gasoline engine configurations and low-load operating conditions. The apparatus adopted a modified 4-cylinder 2.0L gasoline engine to enable single-cylinder operation. To reduce the complexity, the piston position was fixed at a predefined position relative to the top dead center (TDC) to simulate thermodynamic conditions at ignition and injection timings. High-speed Infrared (IR) imaging was applied to visualize the jet penetration and ignition process inside the main cylinder and to investigate the cyclic spatial variability. Two passive pre-chambers with different total nozzle areas and numbers of nozzles were used. In addition, the pre-chamber volume and pressure at ignition timing were varied to examine their effect on jet ignition performance. Misfire behavior was observed in the main chamber of all test cases, and the results suggested that the main cause is a high Residual Mass Fraction (RMF) in the pre-chamber affecting the subsequent cycle. A larger total nozzle area, smaller volume, higher pressure, and fuel-lean operation tended to mitigate the misfire behavior. For a test case with a spark pressure of 6 bar, a reduced cyclic variability in terms of coefficient of variation peak cylinder pressure (COVpmax) from 10.03% to 7.38% and combustion phasing variation from 81 crank angle degree (CAD) to 12 CAD were observed with increasing pre-chamber volume-to-area (WA) ratio from 59.37 m to 103.11 m, but slightly higher misfire frequency was observed, from 46.67% to 50.00%, suggesting an accurate combination of pre-chamber design parameters is needed to improve overall performance at low-load operation.
      原文链接:
    • NSTL
    • Sae Int

    Validation of Kinetic Mechanisms against Various Ignition Delay Data and the Development of Ignition Delay Correlations for Ethanol, Natural Gas, and Primary Reference Fuel Blends under Homogeneous Charge Compression Ignition Conditions

    Lawler, BenjaminZhou, Yingcong
    17页
    查看更多>>摘要：Homogeneous Charge Compression Ignition (HCCI) is a promising advanced combustion concept with high efficiencies and low emissions. Chemical kinetic mechanisms and ignition delay correlations (IDCs) are often applied to simulate HCCI combustion. However, a large number of mechanisms and correlations are not developed specifically for HCCI conditions, i.e., lean mixtures and usually with significant residual gas fractions (RGF). To address this issue, a two-part study is conducted. First, experimental ignition delay time (IDT) data from literature under typical HCCI conditions is collected. Then, thirteen widely applied mechanisms for ethanol, natural gas, and primary reference fuel (PRF) blends of isooctane and n-heptane are validated by running constant-volume simulations. Their performance and accuracy are evaluated. Second, the mechanism with the highest accuracy for each fuel is used to generate IDCs for HCCI conditions. For each fuel, simulations were performed to cover a wide range of pressure (5-SO bar), temperature (800-1400 K), equivalence ratio (0.15-0.8), and RGF (0-60%). The newly generated IDCs have better accuracies than the existing correlations not designed for HCCI conditions. In addition, extra terms are added to the IDC of each fuel for more universal application. A water term is added into the ethanol correlation since wet ethanol is a promising new fuel for HCCI and Thermal Stratified Compression Ignition (TSCI). The effect of ethane and propane is included in the natural gas correlation. A PRF correlation can predict the main ignition event for PRF 80-100 blends with a simple mathematical form. In summary, this study will be valuable for researchers to perform fast and accurate simulations of advanced combustion.
      原文链接:
    • NSTL
    • Sae Int

    Sensitivity Analysis of the Geometrical Dimensions of the Crankpin Bearing on the Tribological Property of an Engine

    Xu, ShaoyongVanliem NguyenWang, XiangjieZhou, Huaxiang...
    14页
    查看更多>>摘要：Under high-speed working conditions of an engine, the lubrication and tribological performance (LTP) of the crankpin bearing (CB) are strongly influenced by the oil film pressure (p) and asperity contact in the mixed lubrication regime (MLR) of CB, while these parameters mainly depend on the CB's geometrical dimensions including the bearing radius (r(b)), bearing width (B), surface roughness (sigma), gap between crankpin and bearing (c), and crankpin speed (omega). To analyze the sensitivity of the dynamic parameters of the r(b), B, sigma, c, and omega on the CB's LTP, a hybrid model of the piston-rod-crank dynamic and CB lubrication is proposed to establish the dynamic equations of the CB. An algorithm program written in MATLAB software is then applied to solve the dynamic equations. The effect of the dynamic parameters of the r(b), B, sigma, c, and omega on the CB's LTP is simulated and evaluated via the indexes of the p, asperity contact force, friction force, and friction coefficient. The research results show that all the parameters of r(b), B, sigma, c, and omega of the CB greatly affect the CB's LTP. To improve the CB's LTP, the r(b), B, and sigma should be slightly reduced whereas the c needs to be increased, especially, the values of 15 <= r(b) <= 20 mm,10 <= B <= 15mm, 2 <= sigma <= 4 mu m, and 15 <= c <= 20 mu m should be used to optimize the CB's LTP. Additionally, the engine speed should be maintained at 2000 rpm to improve the CB's LTP. The reduction of the geometric dimensions and the increase of the engine's power is being the development trend of the engine manufacturers; therefore, the research not only elucidates the influence of the CB parameters on the CB's LTP but also provides an optimal parameter range of the CB to further improve the LTP, fuel economy, and friction power loss, and durability of the engine.
      原文链接:
    • NSTL
    • Sae Int

    Investigation of Distribution and Structure of Surface Textures on Improving Tribological Properties of an Engine

    Jiao RenqiangHua, WenlinNguyen, Vanliem
    12页
    查看更多>>摘要：The elastic hydrodynamic lubrication (EHL) region of the crankpin bearing (CB) not only creates the high friction force due to the solid asperity contact but also reduces the CB's lubrication effectiveness. To improve the CB's tribological properties, the partial textures (PT) designed on the EHL region are proposed. Based on a new hydrodynamic approach combined between the CB's lubrication model and the slider-crank-mechanism (SCM) dynamics model, the distribution density of spherical dimples (SDs) and different structures of the SDs, circular-cylindrical dimples (CCDs), square-cylindrical dimples (SCDs), and wedge-shaped dimples (WSDs) are then simulated and assessed for their effectiveness on improving CB's tribological properties, respectively. The oil film pressure (p), friction force (F-f), and friction coefficient (mu) of the CB are selected as the evaluation indexes. Research results show that the SDs of the PT designed on the EHL region has better performance than the SDs of the full textures (FT) designed over the bearing surface. Additionally, under the same simulation conditions of the PT, the performance of the SDs on improving CB's tribological properties is also better than other textures of CCDs, SCDs, and WSDs. Particularly, the maximum values of both the p and F-f of the SDs with the distribution density of n' = 4 and m' = 6 are remarkably improved by {1.1% and 6.3%} compared to the FT with the distribution density of n = 12 and m = 6; and {14.5% and 15.0%} in comparison without textures on the bearing surface, respectively. Accordingly, the application of the SDs of PT on the beating surface is not only simple in the design process but also can improve better the tribological properties and enhance the durability of the CB in comparison with both the FT and without textures on the bearing surface, and this is the innovation of the article. In addition, the design process of PT on a part of the beating surface also can save cost, machining time, and economic efficiency better than the design process of FT on over the bearing surface.
      原文链接:
    • NSTL
    • Sae Int

    Full Load Investigation of CNG-Diesel Dual-Fuel Heavy-Duty Engine with Selective Catalytic Reduction on Engine Performance and Emissions for Its Potential Use

    Muralidharan, M.Srivastava, AjaySubramanian, M.
    19页
    查看更多>>摘要：The application of compressed natural gas (CNG) as fuel for compression ignition (CI) engines under dual-fuel (DF) mode operation is not attempted in countries like India for commercial purposes. A commercial heavy-duty turbocharged six-cylinder common-rail direct-injected diesel engine has been converted into a DF mode of operation using CNG and diesel for its potential usage and study on its performance along with Selective Catalytic Reduction (SCR). CNG is inducted through the intake manifold at varying energy substitution rates (ESR) with a flow rate of 0.67-1.54 kg/h while diesel fuel is controlled through the engine electronic control unit (ECU). For a maximum ESR of 10.2% with CNG, an increase in power by 8.9% and a 5.8% increase in torque were observed. While there was an increase in brake thermal efficiency (BTE), volumetric efficiency marginally decreased, therefore, to have higher brake power with a OF engine, a dedicated turbocharging system is necessary. The brake-specific energy (BSEC)/fuel consumption (BSFC) has marginally reduced by 1%, and optimum engine speed for better fuel economy was in the range of 1250-2250 rpm. The brake-specific carbon monoxide (BSCO) and carbon dioxide (BSCO2) emissions have considerably reduced while brake-specific non-methane hydrocarbon (BSNMHC), oxides of nitrogen (BSNOx), and methane (BSCH4) emission was marginally higher with CNG substitution; however, within Euro 4 emission norms. Unregulated emissions like ammonia (NH3), propane, and sulfur dioxide (SO2) have reduced while formaldehyde, acetylene, ethylene, and formic acid have marginally increased. SCR has been useful in reducing mass emissions out from the diesel engine and in conversion.
      原文链接:
    • NSTL
    • Sae Int

    Tooth Time-Based Engine Misfire Detection Index for Multicylinder Engines of Vehicles Not Affected by Various Deviations between Cylinders

    Han, Poonggyoo
    14页
    查看更多>>摘要：This article proposes a new misfire detection index, the Delta Gap slope, for a four-cylinder engine. However, the proposed index is not limited to four-cylinder engines. The Delta Gap slope uses the tooth time measured using the existing crankshaft position sensor; therefore, an additional sensor is not required, which makes it economical. The Delta Gap slope is defined as the difference between the gap slopes of the same cylinder for two adjacent cycles. Various factors that cause deviations in gap slopes between cylinders can be eliminated in the process of determining the difference between two gap slopes. Hence, in contrast with the existing engine roughness method, the Delta Gap slope has the advantage of not requiring compensation for deviations between the cylinders. The conventional gap slope method must use different sets of thresholds for each cylinder located at the same position on the sensor wheel, which results in multiple thresholds being applied. In contrast, the Delta Gap slope can use the same set of thresholds for all the cylinders as the deviations between the cylinders are eliminated. Although a set of thresholds is required for diagnosing the start and end of misfire, the values are characterized by the same absolute magnitude and opposite signs; this is another merit of the Delta Gap slope. It was found that the average misfire detection rate of the Delta Gap slope is 90.2% for all the test conditions of idle to 6,000 rpm and neutral to 100% load, and this increased to 93% and 98% between 1,500 rpm and 4,000 rpm. However, the misfire detection rate tends to decrease below the average value as the load approaches neutral and the engine speed exceeds 4,000 rpm.
      原文链接:
    • NSTL
    • Sae Int

    Numerical Assessment of Additive Manufacturing-Enabled Innovative Piston Bowl Design for a Light-Duty Diesel Engine Achieving Ultra-Low Engine-Out Soot Emissions

    Millo, FedericoPiano, AndreaBianco, AndreaPesce, Francesco Concetto...
    17页
    查看更多>>摘要：The design of diesel engine piston bowls plays a fundamental role in the optimization of the combustion process, to achieve ultra-low soot emissions. With this aim, an innovative piston bowl design for a 1.6-liter light-duty diesel engine was developed through a steel-based additive manufacturing (AM) technique, featuring both a sharp step and radial bumps in the inner bowl rim. The potential benefits of the proposed hybrid bowl were assessed through a validated three-dimensional computational fluid dynamics (3D-CFD) model, including a calibrated spray model and detailed chemistry. Firstly, the optimal spray targeting was identified for the novel hybrid bowl over different injector protrusions and two swirl ratio (SR) levels. Considering the optimal spray targeting, an analysis of the combustion process was carried out over different engine working points, both in terms of flame-wall interaction and soot formation. At rated power engine operating conditions, the hybrid bowl highlighted faster mixing-controlled combustion due to the reduced flame-to-flame interaction and the higher air entrainment into the flame front. At partial-load operating points, the hybrid bowl showed a remarkable soot reduction in comparison with the re-entrant bowl due to a more intense soot oxidation rate in the late combustion phase. Moreover, for the hybrid bowl, a robust Exhaust Gas Recirculation (EGR) tolerance was highlighted, leading to a flat soot-brake-specific oxides of nitrogen (BSNOx) trade-off. At constant BSNOx, a 70% soot reduction was achieved without any detrimental effect on fuel consumption, suggesting the high potential of the proposed innovative bowl for soot attenuation.
      原文链接:
    • NSTL
    • Sae Int

    History Effect on Particulate Emissions in a Gasoline Direct Injection Engine

    Etikyala, SreelekhaKoopmans, LucienDahlander, Petter
    11页
    查看更多>>摘要：Soot formation in internal combustion engines is a combination of complex phenomena. Understanding the formation mechanism that influences particulate emissions can help to make gasoline direct injection (GDI) engines comply with increasingly stringent emission standards. It is generally accepted that the deposition of liquid fuel wall films in the combustion chamber is a significant source of particulate formation in GDI engines. The injection timing, which can help avoid interaction between the pistons and fuel spray, has been identified as the parameter with the greatest influence. Traditionally, the start of injection (SOI) sweeps one can find in the literature are carried out by changing the timing one value at a time. To quantify the influence of SOI, variations in our study were carried out in a novel way using cycle-to-cycle parameter control. Instead of motoring or turning off the engine between different SOI variations, the motor was run continuously with combustion and SOI sweeps carried out online in a series of preprogrammed perfectly deterministic SOI sequences to provide evidence of so-called history effects on particulate number (PN). The variation in SOI produces a change in engine combustion and liquid fuel impingement, leading to a state that acts as a precursor for the next state. The different preprogrammed sequences provided excellent data repeatability between engine runs but very different results, depending on the order in which the SOI timings were set. In-cylinder combustion was visualized with an endoscope connected to a high-speed camera. Two SOI timings were chosen (based on piston deposit level data from stationary measurements) to investigate the history effect of preceding conditions on PN. The results show that the preceding engine states influence PN formation and emission that is established as history effect in the study. The history effect is pronounced and was most noticeable under impinging conditions such as early injection timings like -340 crank angle degrees (CAD). History effect was also found to depend on the duration and SOI of the preceding state. More importantly, the history effect depends on how SOI is varied, which in turn influences PN emissions. In the cycle-to-cycle variation of SOI, PN levels at relatively later injection timing of -250 CAD resulted in similarly high levels at an early injection timing of -340 CAD.
      原文链接:
    • NSTL
    • Sae Int