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Technical Paper

Combustion Characterization of Methanol in a Lean Burn Direct Injection Spark Ignition (DISI) Engine

2019-04-02
2019-01-0566
Lean operation is a promising approach to increase the engine efficiency. One of the main challenges for lean-burn technology is the combustion instability. Using a high laminar burning velocity fuel such as methanol might solve that problem. The potential of lean-burn limit extension with methanol was investigated through a comparison with conventional gasoline. In this work, a direct injection turbocharged SI engine was operated at wide open throttle (WOT), with the load controlled by a lean-burn strategy. The amount of fuel was decreased (or lambda increased) until the combustion became unstable. For methanol, the lambda limit was about 1.5, higher than the lambda limit for gasoline which was only about 1.2. The brake thermal efficiency for methanol increased as lambda increased and reached its peak at ~41% in a lambda range of 1.2-1.4. Then, the efficiency decreased as lambda increased.
Technical Paper

Hydrogen Embrittlement Susceptibility of Case Hardened Steel Fasteners

2018-04-03
2018-01-1240
This work establishes the relationship between core hardness, case hardness, and case depth on susceptibility to hydrogen embrittlement of case hardened steel fasteners. Such fasteners have a high surface hardness in order to create their own threads in a mating hole, and are commonly used to attach bracketry and sheet metal in automotive applications. While case hardened fasteners have been studied previously, there are currently no processing guidelines supported by quantitative data for fastener standards. Through sustained load embrittlement testing techniques, the susceptibility of case hardened steel tapping screws to internal and environmental hydrogen embrittlement is examined. Further characterization of the fastener samples through microhardness testing, microstructure review, and fracture surface examination allows the investigation of susceptibility thresholds. It is shown that core hardness is the primary consideration for susceptibility.
Technical Paper

Experimental Investigation and Modelling of the In-Cylinder Heat Transfer during Ringing Combustion in an HCCI Engine

2017-03-28
2017-01-0732
Homogeneous Charge Compression Ignition (HCCI) engines can achieve both a high thermal efficiency and near-zero emissions of NOx and soot. However, their maximum attainable load is limited by the occurrence of a ringing combustion. At high loads, the fast combustion rate gives rise to pressure oscillations in the combustion chamber accompanied by a ringing or knocking sound. In this work, it is investigated how these pressure oscillations affect the in-cylinder heat transfer and what the best approach is to model the heat transfer during ringing combustion. The heat transfer is measured with a thermopile heat flux sensor inside a CFR engine converted to HCCI operation. A variation of the mass fuel rate at different compression ratios is performed to measure the heat transfer during three different operating conditions: no, light and severe ringing. The occurrence of ringing increases both the peak heat flux and the total heat loss.
Technical Paper

Studying the Effect of the Flame Passage on the Convective Heat Transfer in a S.I. Engine

2017-03-28
2017-01-0515
Engine optimization requires a good understanding of the in-cylinder heat transfer since it affects the power output, engine efficiency and emissions of the engine. However little is known about the convective heat transfer inside the combustion chamber due to its complexity. To aid the understanding of the heat transfer phenomena in a Spark Ignition (SI) engine, accurate measurements of the local instantaneous heat flux are wanted. An improved understanding will lead to better heat transfer modelling, which will improve the accuracy of current simulation software. In this research, prototype thin film gauge (TFG) heat flux sensors are used to capture the transient in-cylinder heat flux within a Cooperative Fuel Research (CFR) engine. A two-zone temperature model is linked with the heat flux data. This allows the distinction between the convection coefficient in the unburned and burned zone.
Technical Paper

Combined Synchrotron X-Ray Diffraction and Digital Image Correlation Technique for Measurement of Austenite Transformation with Strain in TRIP-Assisted Steels

2016-04-05
2016-01-0419
The strain-induced diffusionless shear transformation of retained austenite to martensite during straining of transformation induced plasticity (TRIP) assisted steels increases strain hardening and delays necking and fracture leading to exceptional ductility and strength, which are attractive for automotive applications. A novel technique that provides the retained austenite volume fraction variation with strain with improved precision is presented. Digital images of the gauge section of tensile specimens were first recorded up to selected plastic strains with a stereo digital image correlation (DIC) system. The austenite volume fraction was measured by synchrotron X-ray diffraction from small squares cut from the gage section. Strain fields in the squares were then computed by localizing the strain measurement to the corresponding region of a given square during DIC post-processing of the images recorded during tensile testing.
Technical Paper

Demonstrating the Use of Thin Film Gauges for Heat Flux Measurements in ICEs: Measurements on an Inlet Valve in Motored Operation

2016-04-05
2016-01-0641
To optimize internal combustion engines (ICEs), a good understanding of engine operation is essential. The heat transfer from the working gases to the combustion chamber walls plays an important role, not only for the performance, but also for the emissions of the engine. Besides, thermal management of ICEs is becoming more and more important as an additional tool for optimizing efficiency and emission aftertreatment. In contrast little is known about the convective heat transfer inside the combustion chamber due to the complexity of the working processes. Heat transfer measurements inside the combustion chamber pose a challenge in instrumentation due to the harsh environment. Additionally, the heat loss in a spark ignition (SI) engine shows a high temporal and spatial variation. This poses certain requirements on the heat flux sensor. In this paper we examine the heat transfer in a production SI ICE through the use of Thin Film Gauge (TFG) heat flux sensors.
Journal Article

Carbon and Manganese Effects on Quenching and Partitioning Response of CMnSi-Steels

2015-04-14
2015-01-0530
Quenching and partitioning (Q&P) is a novel heat treatment to produce third generation advanced high-strength steels (AHSS). The influence of carbon on mechanical properties of Q&P treated CMnSi-steels was studied using 0.3C-1.5Mn-1.5Si and 0.4C-1.5Mn-1.5Si alloys. Full austenitization followed by two-step Q&P treatments were conducted using varying partitioning times and a fixed partitioning temperature of 400 °C. The results were compared to literature data for 0.2C-1.6Mn-1.6Si, 0.2-3Mn-1.6Si and 0.3-3Mn-1.6Si Q&P treated steels. The comparison showed that increasing the carbon content from 0.2 to 0.4 wt pct increased the ultimate tensile strength by 140 MPa per 0.1 wt pct C up to 1611 MPa without significantly decreasing ductility for the partitioning conditions used. Increased alloy carbon content did not substantially increase the retained austenite fractions. The best combinations of ultimate tensile strength and total elongation were obtained using short partitioning times.
Journal Article

Effects of Chemical Composition, Heat Treatment, and Microstructure in Splittable Forged Steel Connecting Rods

2015-04-14
2015-01-0522
Fracture split forged steel connecting rods are utilized in many new high performance automotive engines to increase durability. Higher strength levels are needed as the power density increases. Fracture splitting without plastic deformation is necessary for manufacturability. Metallurgical design is a key for achieving the required performance levels. Several medium carbon steels containing 0.07 wt pct P, 0.06 wt pct S and various amounts of Mn, Si, V, and N were produced by vacuum induction melting laboratory heats and hot working the cast ingots into plates. The plates were cooled at varying rates to simulate typical cooling methods after forging. Microstructures were generally ferrite and pearlite as evaluated by light optical and scanning electron microscopy. Mechanical properties were determined by standard tensile tests, high strain rate notched tensile tests, and Charpy V-notch impact tests to assess “splittability”.
Technical Paper

Assessment of Empirical Heat Transfer Models for a CFR Engine Operated in HCCI Mode

2015-04-14
2015-01-1750
Homogeneous charge compression ignition (HCCI) engines are a promising alternative to traditional spark- and compression-ignition engines, due to their high thermal efficiency and near-zero emissions of NOx and soot. Simulation software is an essential tool in the development and optimization of these engines. The heat transfer submodel used in simulation software has a large influence on the accuracy of the simulation results, due to its significant effect on the combustion. In this work several empirical heat transfer models are assessed on their ability to accurately predict the heat flux in a CFR engine during HCCI operation. Models are investigated that are developed for traditional spark- and compression-ignition engines such as those from Annand [1], Woschni [2] and Hohenberg [3] and also models developed for HCCI engines such as those from Chang et al. [4] and Hensel et al. [5].
Journal Article

Calibration of a TFG Sensor for Heat Flux Measurements in a S.I. Engine

2015-04-14
2015-01-1645
In the development of internal combustion engines, measurements of the heat transfer to the cylinder walls play an important role. These measurements are necessary to provide data for building a model of the heat transfer, which can be used to further develop simulation tools for engine optimization. This research will focus on the Thin Film Gauge (TFG) heat flux sensor. This sensor consists of a platinum RTD (Resistance Temperature Detector) on an insulating Macor® (ceramic) substrate. The sensor has a high frequency response (up to 100 kHz) and is small and robust. These properties make the TFG sensor adequate for measurements in the combustion chamber of an internal combustion engine. To use this sensor, its thermal properties - namely the temperature sensitivity coefficient and the thermal product - must be correctly calibrated. First, different calibration setups with a different temperature range are used to calibrate the temperature sensitivity coefficient of the TFG sensor.
Technical Paper

On the Work-hardening Description of Low Carbon Steel Sheets by a Microstructure Based Model

2014-09-30
2014-36-0179
The work-hardening of three common automotive low carbon steel sheets is described in terms of two different types of microstructure based models. The first model employed is the classical Kocks-Mecking model. On the other hand, the second model incorporates the effect of the density evolution of non-redundant dislocations, also known as Geometrically Necessary Dislocations (GND), into the Kocks-Mecking hardening law. Each of both models was coupled to a Taylor-type crystal plasticity framework in order to follow the dislocation density evolution over all slip systems. One of the microstructural parameters employed on the calibration of the second model is the density of GND, parameter which was experimentally acquired from crystal orientation maps by EBSD (Electron Backscatter Diffraction) on the tensile samples.
Technical Paper

Effects of Constituent Properties on Performance Improvement of a Quenching and Partitioning Steel

2014-04-01
2014-01-0812
In this paper, a two-dimensional microstructure-based finite element modeling method is adopted to investigate the effects of material parameters of the constituent phases on the macroscopic tensile behavior of Q&P steel and to perform a computational material design approach for performance improvement. For this purpose, a model Q&P steel is first produced and various experiments are then performed to characterize the model steel. Actual microstructure-based model is generated based on the information from EBSD, SEM and nano-indentation test, and the material properties for the constituent phases in the model are determined based on the initial constituent properties from HEXRD test and the subsequent calibration of model predictions to tensile test results. The influence of various material parameters of the constituents on the macroscopic behavior is then investigated.
Technical Paper

Evaluation of Some Important Boundary Conditions for Spray Measurements in a Constant Volume Combustion Chamber

2013-04-08
2013-01-1610
Fuel atomization and combustion at engine-like conditions are complicated and sensitive processes which make it hard to perform quantitative experiments with high precision and reproducibility. A better understanding of the processes can be obtained by controlling the boundary conditions. Variable parameters with an important influence on the sprays include fuel temperature, chamber temperature, injection pressure, gas velocity. Controlling all these parameters in an experimental setup is not evident since a lot of them fluctuate with time or interact with each other. Constant volume combustion chambers, using the pre-combustion method, have already shown to be a useful experimental tool for this kind of research purposes. The obtained quantitative results can in a next step be used to evaluate either multi-dimensional or simplified lower dimensional models.
Technical Paper

Development and Validation of a Knock Prediction Model for Methanol-Fuelled SI Engines

2013-04-08
2013-01-1312
Knock is one of the main factors limiting the efficiency of spark-ignition engines. The introduction of alternative fuels with elevated knock resistance could help to mitigate knock concerns. Alcohols are prime candidate fuels and a model that can accurately predict their autoignition behavior under varying engine operating conditions would be of great value to engine designers. The current work aims to develop such a model for neat methanol. First, an autoignition delay time correlation is developed based on chemical kinetics calculations. Subsequently, this correlation is used in a knock integral model that is implemented in a two-zone engine code. The predictive performance of the resulting model is validated through comparison against experimental measurements on a CFR engine for a range of compression ratios, loads, ignition timings and equivalence ratios.
Journal Article

Characterization of Advanced High Strength Steel Sheets in View of the Numerical Prediction of Sidewall Curl

2013-01-21
2012-01-2326
In this study, a procedure for characterizing advanced high strength steel sheets is presented in view of determining the material parameters for constitutive models that can be used for accurate prediction of springback and sidewall curl. The mechanical properties of DP980 and TRIP780 sheets were obtained experimentally, and their cyclic tension-compression behaviour was modeled with the Chaboche nonlinear kinematic hardening model and the Yoshida-Uemori two-surface plasticity model that are implemented in LS-DYNA. The unloading moduli were determined from monotonic tension tests at various prestrain levels. An inverse approach based on linear and quadratic response surfaces created by Sequential Strategy with Domain Reduction (SRSM) methodology using LS-OPT software was used and investigated to identify specific material parameters in each constitutive model.
Technical Paper

Spray Parameter Comparison between Diesel and Vegetable Oils for Non-Evaporating Conditions

2012-04-16
2012-01-0461
The internal combustion engine with compression ignition is still the most important power plant for heavy duty transport, railway transport, marine applications and generator sets. Fuel cost and emission regulations drive manufacturers to switch to alternative fuels. The understanding and prediction of these fuels in the spray and combustion process will be very important for these issues. In the past, lot of research was done for conventional diesel fuel by optically analyzing both spray and combustion. However comparison between different groups is difficult since qualitative results and accuracies are depending in the used definitions and methods. The goal of present research is to verify the behavior pure oils compared to more standard fuels while paying lot of attention to the interpretation of the measurement results.
Technical Paper

Comparison of Hole Expansion Properties of Quench & Partitioned, Quench & Tempered and Austempered Steels

2012-04-16
2012-01-0530
Quenching & Partitioning (Q&P) is receiving increased attention as a novel Advanced High Strength Steel (AHSS) processing route as promising tensile properties of the “third generation” have been reported. The current contribution reports hole expansion ratios (HER) of Q&P steels and compares the values with HERs obtained for “conventional” AHSS processing routes such as austempering and Quench & Tempering (Q&T). Intercritically annealed C-Mn-Al-Si-P and fully austenitized C-Mn-Si microstructures were studied. Optimum combinations of tensile strength and HER were obtained for fully austenitized C-Mn-Si Q&P samples. Higher HER values were obtained for Q&P than for Q&T steels for similar tempering/partitioning temperatures. Austempering following intercritical annealing results in higher HER than Q&P at similar tensile strength levels. In contrast, Q&P following full austenitization results in higher hole expansion than austempering even at higher strength levels.
Journal Article

Hydrogen Embrittlement of Commercially Produced Advanced High Strength Sheet Steels

2010-04-12
2010-01-0447
The susceptibility of Advanced High Strength Steels (AHSS) to hydrogen embrittlement (HE) was evaluated on selected high strength sheet steels (DP 600, TRIP 780, TRIP 980, TWIP-Al, TWIP, and Martensitic M220) and the results were compared to data on a lower strength (300 MPa tensile strength) low carbon steel. Tensile samples were cathodically charged and then immediately tensile tested to failure to analyze the mechanical properties of the as-charged steel. The effects of hydrogen on deformation and fracture behavior were evaluated through analysis of tensile properties, necking geometry, and SEM images of fracture surfaces and metallographic samples of deformed tensile specimens. The two fully austenitic TWIP steels were resistant to hydrogen effects in the laboratory charged tensile samples.
Journal Article

Expanding the Experimental Capabilities of the Ignition Quality Tester for Autoigniting Fuels

2010-04-12
2010-01-0741
This paper reports the development of new fuel ignition quality and combustion experiments performed using the Ignition Quality Tester (IQT). Prior SAE papers (961182, 971636, 1999-01-3591, and 2001-01-3527) documented the development of the IQT constant volume combustion chamber experimental apparatus to measure ignition qualities of diesel-type fuels. The ASTM International test method D6890 was developed around the IQT device to allow the rapid determination of derived cetane number (DCN). Interest in chemical kinetic models for the ignition of diesel and biodiesel model compounds is increasing to support the development of advanced engines and fuels. However, rigorous experimental validation of these kinetic models has been limited for a variety of reasons. Shock tubes and rapid compression machines are typically limited to premixed gas-phase studies, for example.
Technical Paper

Predicting the Radius of a Sheet Bent Around Drawbeads

2009-04-20
2009-01-1395
Drawbeads in production stamping dies often have insufficient penetration of the male bead into the female cavity. With insufficient penetration, the actual bending radii of the sheet metal are larger than the geometrical radii of the drawbead. The actual bending radii in the sheet directly affect the force that restrains sheet movement. To predict the restraining stress due to a drawbead, it is necessary to know the actual bending radii in the sheet as it passes though the drawbead. Data from a previous study are used to develop empirical regression equations for predicting measured radii of the sheet that is bent around the radii in a drawbead. A physical model for the evolution of the sheet radii as the drawbead closes is proposed. This model is consistent with the empirical equations and the mechanics of the sheet bending process.
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