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  • 1. Andersson, Magnus
    et al.
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Noehre, Christof
    A Predictive Real Time NOx Model for Conventional and Partially Premixed Diesel Combustion2006In: SAE, Session: Diesel Engine Modeling, 2006Conference paper (Refereed)
    Abstract [en]

    A previously presented robust and fast diagnostic NOx model was modified into a predictive model. This was done by using simple yet physically-based models for fuel injection, ignition delay, premixed heat release rate and diffusion combustion heat release rate. The model can be used both for traditional high temperature combustion and for high-EGR low temperature combustion. It was possible to maintain a high accuracy and calculation speed of the NOx model itself. The root mean square of the relative model error is 16 % and the calculation speed is around one second on a PC. Combustion characteristics such as ignition delay, CA50 and the general shape of the heat release rate are well predicted by the combustion model. The model is aimed at real time NOx calculation and optimization in a vehicle on the road.

  • 2. Andersson, Magnus
    et al.
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Noehre, Christof
    A Real Time NOx Model for Conventional and Partially Premixed Diesel Combustion2006In: SAE, Session: Compression Ignition Combustion Processes (Part 3 of 3), 2006Conference paper (Refereed)
    Abstract [en]

    In this paper a fast NOx model is presented which can be used for engine optimization, aftertreatment control or virtual mapping. A cylinder pressure trace is required as input data. High calculation speed is obtained by using table interpolation to calculate equilibrium temperatures and species concentrations. Test data from a single-cylinder engine and from a complete six-cylinder engine have been used for calibration and validation of the model. The model produces results of good agreement with emission measurements using approximately 50 combustion product zones and a calculation time of one second per engine cycle. Different compression ratios, EGR rates, injection timing, inlet pressures etc. were used in the validation tests. The model calculates thermal (high-temperature) NOx formation by the two reactions of the original Zeldovich mechanism but by using a simple empirical compensation algorithm, the model can also be used for low-temperature NOx formation associated with high EGR rates and long ignition delay.

  • 3. Andersson, Magnus
    et al.
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Noehre, Christof
    Fast Physical NOx Prediction in Diesel Engines2006Conference paper (Refereed)
  • 4. Anton, N.
    et al.
    Genrup, M.
    Fredriksson, C.
    Larsson, P. -I
    Erlandsson-Christiansen, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Exhaust volume dependency of turbocharger turbine design for a heavy duty otto cycle engine2017In: Proceedings of the ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, GT 2017, ASME Press, 2017, Vol. 2C, article id V02CT44A015Conference paper (Refereed)
    Abstract [en]

    This study is considering turbocharger turbine performance at "on-engine" conditions with respect to turbine design variables and exhaust manifold volume. The highly unsteady nature of the internal combustion engine will result in a very wide range of turbine operation, far from steady flow conditions. As most turbomachinery design work is conducted at steady state, the influence of the chosen turbine design variables on the crank-angle-resolved turbine performance will be of prime interest. In order to achieve high turbocharger efficiency with the greatest benefits for the engine, the turbine will need high efficiency at the energetic exhaust pressure pulse peak. The starting point for this paper is a target full load power curve for a heavy duty Otto-cycle engine, which will dictate an initial compressor and turbine match. Three radial turbine designs are investigated, differing with respect to efficiency characteristics, using a common compressor stage. The influence of the chosen turbine design variables considering a main contributor to unsteadiness, exhaust manifold volume, is evaluated using 1D engine simulation software. A discussion is held in conjunction with this regarding the efficiency potential of each turbine design and limitations of turbine types.

  • 5. Bergin, Michael J.
    et al.
    Reitz, Rolf D.
    Oh, Sungmook
    Miles, Paul C.
    Hildingsson, Leif
    Hultqvist, Anders
    Lund Institute of Technology, Sweden.
    Fuel Injection and Mean Swirl Effects on Combustion and Soot Formation in Heavy Duty Diesel Engines2007In: SAE, Session: Compression Ignition Combustion Processes (Part 2of 2)., 2007Conference paper (Refereed)
    Abstract [en]

    High-speed video imaging in a swirl-supported (Rs = 1.7), direct-injection heavy-duty diesel engine operated with moderate-to-high EGR rates reveals a distinct correlation between the spatial distribution of luminous soot and mean flow vorticity in the horizontal plane. The temporal behavior of the experimental images, as well as the results of multi-dimensional numerical simulations, show that this soot-vorticity correlation is caused by the presence of a greater amount of soot on the windward side of the jet. The simulations indicate that while flow swirl can influence pre-ignition mixing processes as well as post-combustion soot oxidation processes, interactions between the swirl and the heat release can also influence mixing processes. Without swirl, combustion-generated gas flows influence mixing on both sides of the jet equally. In the presence of swirl, the heat release occurs on the leeward side of the fuel sprays. Asymmetric combustion-induced flows alter the vorticity on the leeward side of the jet and lead to better entrainment and fuel-air mixing during the period of peak heat release. This leads to lower local equivalence ratio and lower soot production rates with swirl.

  • 6. Bladh, Henrik
    et al.
    Hildingsson, Leif
    Gross, Volker
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Bengtsson, Per-Erik
    Quantitative soot measurements in an HSDI Diesel engine2006Conference paper (Refereed)
    Abstract [en]

    Quantitative in-cylinder measurements of soot volume fraction in a single-cylinder HSDI Diesel engine, based on a VOLVO D5, has been carried out using the laser-induced incandescence (LII) technique using laser excitation at 1064 nm and an ICCD camera with prompt gate detection. Quantitative data was obtained by relating the LII signal response from the engine to that from a calibration flame. The aim of this paper is twofold: to present quantitative data for relevant engine operating conditions and to discuss the issues related to quantification of the LII technique using the present approach. Two different operating condition schemes were investigated. In the first, the soot production for different amounts of EGR was investigated. The in-cylinder soot volume fraction levels were found to decrease with increasing EGR ratio in the tested EGR regime, which correlates well with engine-out soot emissions. In the second part of the investigation, the injection event was divided into one pilot injection and one main injection at a constant EGR ratio of 60%. The CAD position of the pilot injection was varied, while keeping the position of the main injection constant. Early pilot injection timings resulted in excessive fouling of the optical parts, thus limiting the accuracy of quantitative measurements. Still, the flow pattern of the soot within the cylinder is presented and discussed. The corrections needed to accurately estimate soot volume fractions in an optical engine by relating the integrated LII signal to that obtained in a calibration flame are discussed. Using a heat and mass transfer model for LII, the pressure and temperature effects on the absolute LII signals are investigated. Results show that the use of a short prompt gate (30 ns) is preferable in order to decrease systematic errors due to differences in the conditions between the engine and the calibration flame. Also the systematic errors introduced by potential particle aggregation are studied and discussed.

  • 7. Christensen, Magnus
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Demonstrating the Multi Fuel Capability of a Homogeneous Charge Compression Ignition Engine with Variable Compression Ratio1999Conference paper (Refereed)
  • 8. Christensen, Magnus
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    The Effect of Topland Geometry on Emissions of Unburned Hydrocarbons from a Homogeneous Charge Compression Ignition (HCCI) Engine2001Conference paper (Refereed)
  • 9. Christensen, Magnus
    et al.
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    The Effect of Combustion Chamber Geometry on HCCI Operation2002Conference paper (Refereed)
    Abstract [en]

    The effect of the combustion chamber geometry and the turbulence on Homogeneous Charge Compression Ignition (HCCI) operation has been experimentally investigated. A high turbulent square bowl in piston combustion chamber has been compared with a low turbulent disc combustion chamber.

    The results showed that the combustion chamber geometry plays large role for HCCI combustion. At the same operating conditions, the peak combustion rate for the square bowl combustion chamber was much lower compared to the disc combustion chamber. The combustion duration was in some cases almost a factor two longer for the square bowl combustion chamber. The lower combustion rate with the square bowl was due larger heat losses, lower combustion efficiency and higher turbulence.

  • 10. Hildingsson, Leif
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Miles, P.
    The effect of swirl and injection phasing on flow structures and mixing in an HSDI diesel engine2006Conference paper (Refereed)
  • 11. Hildingsson, Leif
    et al.
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Särner, Gustaf
    Richter, Mattias
    Aldén, Marcus
    Simultaneous Formaldehyde and Fuel-Tracer LIF Imaging in a High-Speed Diesel Engine With Optically Accessible Realistic Combustion Chamber2005Conference paper (Refereed)
    Abstract [en]

    Simultaneous laser-induced fluorescence (LIF) imaging of formaldehyde and a fuel-tracer have been performed in a high-speed diesel engine. N-heptane and isooctane were used as fuel and toluene was used as a tracer. This arrangement made it possible to make simultaneous measurements of toluene by exciting at 266 nm and detecting at 270-320 nm while exciting formaldehyde at 355 nm and detecting at 400-500 nm.

    The aim of this study is to investigate how traditional fuel tracer and natural-occurring formaldehyde formed in the cool chemistry are transported in the piston bowl. A range of ignition delays were created by running the engine with different amounts of EGR. During this sweep the area where the low-temperature reactions take place were studied.

    The measurements were performed in a 0.5-l, single-cylinder optical engine running under conditions simulating a cruise-point, i.e., about 2.2 bar imep. The ignition delay was elongated compared to the normal mapping and the engine-out emissions of soot and NOx were ultra-low.

    It was found that the spatial location of LTR's does not shift significantly for different EGR levels. The formaldehyde signal overlaps the fuel signal in most cases before the onset of the main heat release.

  • 12. Hult, Johan
    et al.
    Richter, Mattias
    Nygren, Jenny
    Aldén, Marcus
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Christensen, Magnus
    Johansson, Bengt
    Application of a High Speed Laser Diagnostic System for Single-Cycle Resolved Imaging in IC Engines2002In: Applied Optics, Vol. 41, no 24, p. 5002-5014Article in journal (Refereed)
  • 13.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Christensen, Magnus
    Johansson, Bengt
    The Application of Ceramic and Catalytic Coatings to Reduce the Unburned Hydrocarbon Emissions from a Homogeneous Charge Compression Ignition Engine2000Conference paper (Refereed)
  • 14.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Christensen, Magnus
    Johansson, Bengt
    The Heterogeneous Combustion Process in an HCCI Engine – Optical Characterization of Fluctuations and Length Scales2001Conference paper (Refereed)
  • 15.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Christensen, Magnus
    Johansson, Bengt
    Franke, Axel
    Richter, Mattias
    Aldén, Marcus
    A Study of the Homogeneous Charge Compression Ignition Combustion Process by Chemiluminescence Imaging1999Conference paper (Refereed)
    Abstract [en]

    An experimental study of the Homogeneous Charge Compression Ignition (HCCI) combustion process has been conducted by using chemiluminescence imaging. The major intent was to characterize the flame structure and its transient behavior. To achieve this, time resolved images of the naturally emitted light were taken. Emitted light was studied by recording its spectral content and applying different filters to isolate species like OH and CH.

    Imaging was enabled by a truck-sized engine modified for optical access. An intensified digital camera was used for the imaging. Some imaging was done using a streak-camera, capable of taking eight arbitrarily spaced pictures during a single cycle, thus visualizing the progress of the combustion process. All imaging was done with similar operating conditions and a mixture of n-heptane and iso-octane was used as fuel.

    Some 20 crank angles before Top Dead Center (TDC), cool flames were found to exist. They appear with a faint structure, evenly distributed throughout the combustion chamber. There was no luminosity recorded between the end of cool flames and the start of the main heat release. Around TDC the main heat release starts. Looking at a macro scale, we find that the charge starts to burn simultaneously at arbitrary points throughout the charge. Since the thermal boundary layer is colder than the bulk of the charge, the local heat release is delayed close to the walls. As a result, the total heat release is slowed down. Ensemble averaged 1 images show this wall boundary effect clearly when plotted against CAD. The peak intensity at the main combustion event is one order of magnitude greater than that of the cool flame and the structure is a lot more protruding.

    Since spontaneous emission imaging is a line-of-sight integration, the flame structure appears a bit smeared. The micro scale structure is very similar from one cycle to another, but there are large variations between cycles on the macro scale.

  • 16.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Christensen, Magnus
    Johansson, Bengt
    Nygren, Jenny
    Richter, Mattias
    Hult, Johan
    Aldén, Marcus
    The HCCI Combustion Process in a Single Cycle - High-Speed Fuel Tracer LIF and Chemiluminescence Imaging2002Conference paper (Refereed)
  • 17.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Engdar, Ulf
    Johansson, Bengt
    Klingmann, Jens
    Reacting Boundary Layers in a Homogeneous Charge Compression Ignition (HCCI) Engine2001Conference paper (Refereed)
  • 18.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Hildingsson, Leif
    Chartier, Clement
    Miles, Paul
    On Soot Reduction by Post Injection Under Dilute Low Temperature Diesel Combustion2006Conference paper (Refereed)
  • 19.
    Hultqvist, Anders
    et al.
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Christensen, Magnus
    Richter, Mattias
    Engström, Johan
    Franke, Axel
    Near Wall Combustion in a Homogenous Charge Compression Ignition (HCCI) Engine2000Conference paper (Refereed)
  • 20. Johansson, Bengt
    et al.
    Tunestal, Per
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Vressner, Andreas
    Fuel Effects on Ion Current in An Hcci Engine2005In: SAE, Session: Diagnostics in SI and DIesel Engines, SAE International , 2005Conference paper (Refereed)
    Abstract [en]

    An interest in measuring ion current in Homogeneous Charge Compression Ignition (HCCI) engines arises when one wants to use a cheaper probe for feedback of the combustion timing than expensive piezo electric pressure transducers. However the location of the ion current probe, in this case a spark plug, is of importance for both signal strength and the crank angle position where the signal is obtained. Different fuels will probably affect the ion current in both signal strength and timing and this is the main interest of this investigation. The measurements were performed on a Scania D12 engine in single cylinder operation and ion current was measured at 7 locations simultaneously. By arranging this setup there was a possibility to investigate if the ion current signals from the different spark plug locations would correlate with the fact that, for this particular engine, the combustion starts at the walls and propagates towards the centre of the combustion chamber. The fuels investigated were isooctane, n-heptane, PRF80, gasoline, diesel, ethanol and methanol. A special interest was how the ion current timing was affected by low temperature reactions, which were present with the n-heptane and diesel fuels as well as mixtures of isooctane and n-heptane, i.e. PRF80. The most interesting results were that ion current is both affected by the ion current probe location in the combustion chamber and the fuel used. Fuels with higher octane number seem to provoke ion current more easily, thus with LTR fuels as n-heptane and diesel ion current was only achieved at richer mixtures. The cycle to cycle variations of ion current increased with leaner mixtures. Ion current was also affected by combustion phasing and engine speed.

  • 21. Lemel, Mikael
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Vressner, Andreas
    Nordgren, Henrik
    Persson, Håkan
    Johansson, Bengt
    Quantification of the Formaldehyde Emissions From Different Hcci Engines Running on a Range of Fuels2005In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) (Part 3 of 6), 2005Conference paper (Refereed)
    Abstract [en]

    In this paper, the formaldehyde emissions from three different types of homogenous charge compression ignition (HCCI) engines are quantified for a range of fuels by means of Fourier Transform Infra Red (FTIR) spectroscopic analysis. The engines types are differentiated in the way the charge is prepared. The characterized engines are; the conventional port fuel injected one, a type that traps residuals by means of a Negative Valve Overlap (NVO) and finally a Direct Injected (DI) one. Fuels ranging from pure n-heptane to iso-octane via diesel, gasoline, PRF80, methanol and ethanol were characterized. Generally, the amount of formaldehyde found in the exhaust was decreasing with decreasing air/fuel ratio, advanced timing and increasing cycle temperature. It was found that increasing the source of formaldehyde i.e. the ratio of heat released in the cool-flame, brought on higher exhaust contents of formaldehyde. The application of a standard three-way catalyst completely removed formaldehyde from the exhaust stream.

  • 22.
    Mahendar, Senthil Krishnan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Erlandsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Adlercreutz, L.
    Challenges for Spark Ignition Engines in Heavy Duty Application: A Review2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    Spark Ignition (SI) engines operating on stoichiometric mixtures can employ a simple three-way catalyst as after-treatment to achieve low tailpipe emissions unlike diesel engines. This makes heavy duty (HD) SI engines an attractive proposition for low capital cost and potentially low noise engines, if the power density and efficiency requirement could be met. Specific torque at low speeds is limited in SI engines due to knock. In HD engines, the higher flame travel distances associated with higher bore diameters exacerbates knock due to increased residence time of the end gas. This report reviews the challenges in developing HD SI engines to meet current diesel power density. It also focuses on methods to mitigate them in order to achieve high thermal efficiency while running on stoichiometric condition. High octane renewable fuels are seen as a key enabler to achieve the performance level required in such applications. Apart from higher octane rating, the effect of higher latent heat of vaporization in liquid alcohol fuels was found to be beneficial in all operating conditions as it tended to reduce in-cylinder temperature and associated heat loss of the engine. Exhaust gas recirculation (EGR) was seen to be beneficial both at full load in limiting knock and part load conditions to decrease pumping losses. Increased in-cylinder turbulence was also seen to be beneficial in limiting knock as it reduces residence time of the end gas. Results and trends of combinations of these factors are discussed with respect to increasing engine specific torque and efficiency. The effect on emissions and part load conditions is included where results are available and gaps in knowledge are presented. 

  • 23. Miles, P.
    et al.
    Collin, R.
    Hildingsson, L.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Andersson, Ö.
    Combined measurements of flow structure, partially oxidized fuel and soot in a high-speed direct injection diesel engines2007In: Proceedings of the Combustion Institute, ISSN 1540-7489Article in journal (Refereed)
    Abstract [en]

    The evolution of bulk flow structures and their influence on the spatial distribution of heat release zones and of partially oxidized fuel and particulate matter (soot) is examined experimentally in a swirl-supported, direct-injection diesel engine. Vector fields describing the bulk flow structures are measured with particle image velocimetry (PIV), while complementary scalar field measurements of partially oxidized fuel and soot are obtained in the same vertical plane using broadband laser-induced fluorescence (LIF) and laser-induced incandescence (LII) techniques, respectively. The two-dimensional divergence of the mean velocity fields is also employed to provide information on the mean locations of heat release. Measurements are performed at a highly dilute, 12% O-2, operating condition characteristic of low-NO,, low-temperature diesel combustion systems. The spatial distributions of unburned fuel rapidly develop a structure characterized by two separate zones of high fuel concentration, an inner zone in the cylinder center and an outer zone in the squish volume. Single-cycle measurements show that this two-zone structure is present on an individual cycle basis, and is not an artifact of averaging distinct, single-zone distributions. For this engine build, the mean flow structures developed do not actively promote mixing of either zone, although bulk flow structures in the upper-central region of the cylinder vary significantly on a cycle-by-cycle basis. The measured spatial distributions of particulates indicate that particulates are formed primarily in the inner zone-and remain un-oxidized late in the cycle.

  • 24. Miles, Paul C.
    et al.
    Hildingsson, Leif
    Hultqvist, Anders
    Lund Institute of Technology, Sweden.
    The influence of fuel injection and heat release on bulk flow structures in a direct-injection, swirl-supported diesel engine2007In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 43, no 2-3Article in journal (Refereed)
    Abstract [en]

    Particle image velocimetry is applied to measure the vertical (r-z) plane flow structures in a light-duty direct-injection diesel engine with a realistic piston geometry. The measurements are corrected for optical distortions due to the curved piston bowl walls and the cylindrical liner. Mean flow fields are presented and contrasted for operation both with and without fuel injection and combustion. For operation with combustion, the two-dimensional divergence of the measured mean velocity fields is employed as a qualitative indicator of the locations of mean heat release. In agreement with numerical simulations, dual-vortex, vertical plane mean flow structures that may enhance mixing rates are formed approximately mid-way through the combustion event. Late in the cycle a toroidal vortex forms outside the bowl mouth. Imaging studies suggest that soot and partially oxidized fuel trapped within this vortex are slow to mix with surrounding fluid; moreover, the vortex impedes mixing of fluid exiting the bowl with air within the squish volume.

  • 25. Noehre, Christof
    et al.
    Andersson, Magnus
    Johansson, Bengt
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Characterization of partially premixed combustion2006In: SAE, Session: Diesel Engine Experiment (Part 2 of 3), 2006Conference paper (Refereed)
    Abstract [en]

    Partially Premixed Combustion (PPC) provides the potential of simultaneous reduction of NOx and soot for diesel engines. This work attempts to characterize the operating range and conditions required for PPC. The characterization is based on the evaluation of emission and in-cylinder measurement data of engine experiments. It is shown that the combination of low compression ratio, high EGR rate and engine operation close to stoichiometric conditions enables simultaneous NOx and soot reduction at loads of 8bar, 12bar, and 15bar IMEP gross. The departure from the conventional NOx-soot trade-off curve has to be paid with a decline in combustion efficiency and a rise in HC and CO emissions. It is shown that the low soot levels of PPC come along with long ignition delay and low combustion temperature. A further result of this work is that higher inlet pressure broadens the operating range of Partially Premixed Combustion.

  • 26. Nordgren, Henrik
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Start of injection strategies for HCCI-combustion2004In: SAE, Homogeneous Charge Compression Ignition (Part C&D), 2004Conference paper (Refereed)
    Abstract [en]

    Homogeneous Charge Compression Ignition (HCCI) has a great potential for low NOx emissions but problems with emissions of unburned hydrocarbons (HC). One way of reducing the HC is to use direct injection. The purpose of this paper is to present experimental data on the trade off between NOx and HC. Injection timing, injection pressure and nozzle configuration all effect homogeneity of the mixture and thus the NOx and HC emissions. The engine studied is a single cylinder version of a Scania D12 that represents a modern heavy-duty truck size engine. A common rail (CR) system has been used to control injection pressure and timing. The combustion using injectors with different nozzle hole diameters and spray angle, both colliding and non-colliding, has been studied. The NOx emission level changes with start of injection (SOI) and the levels are low for early injection timing, increasing with retarded SOI. Different injectors produce different NOx levels. Especially at late injection timing, at about -50°ATDC, there is a significant difference between injectors. The HC emissions also differ for different injection timing and injectors.

  • 27. Nygren, Jenny
    et al.
    Hult, Johan
    Richter, Mattias
    Aldén, Marcus
    Christensen, Magnus
    Hultqvist, Anders
    Lund Institute of Technology, Sweden.
    Johansson, Bengt
    Three-dimensional Laser Induced Fluorescence of Fuel Distributions in an HCCI Engine2002In: Proceedings of the Combustion Institute, ISSN 0082-0784, E-ISSN 1878-027X, Vol. 29Article in journal (Refereed)
    Abstract [en]

    Three-dimensional imaging of fuel tracer planar laser-induced fluorescence in a homogeneous charge compression ignition (HCCI) engine is presented. A high-speed multiple Nd: YAG laser and detection system, in combination with a scanning mirror, are used to collect eight images, with an equidistant separation of 0.5 mm. Three-dimensional isoconcentration surfaces calculated from the data are visualized. Three-dimensional imaging offers new opportunities to study different combustion events, specifically the topology of flame structures. For example, it is possible to distinguish if separate islands in a fluorescence image really are separate or if it is an effect from wrinkling in and out of the laser sheet. The PLIF images were also analyzed by identifying five intensity ranges corresponding to increasing degrees of reaction progress. The gradual fuel consumption and thus combustion was then analyzed by calculating the volumetric fraction of these intensity ranges for different crank angle positions. The occurrence of multiple isolated ignition spots and the observed gradual decrease in fuel concentration indicates that HCCI combustion relies on distributed reactions and not flame propagation.

  • 28. Olofsson, Jimmy
    et al.
    Seyfried, Hans
    Richter, Mattias
    Aldén, Marcus
    Vressner, Andreas
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Lombaert, Karine
    High-Speed Lif Imaging for Cycle-Resolved Formaldehyde Visualization in Hcci Combustion2005In: SAE, Session: Combustion and Flow Diagnostics, 2005Conference paper (Refereed)
    Abstract [en]

    High-speed laser diagnostics was utilized for single-cycle resolved studies of the formaldehyde distribution in the combustion chamber of an HCCI engine. A multi-YAG laser system consisting of four individual Q-switched, flash lamp-pumped Nd:YAG lasers has previously been developed in order to obtain laser pulses at 355 nm suitable for performing LIF measurements of the formaldehyde molecule. Bursts of up to eight pulses with very short time separation can be produced, allowing capturing of LIF image series with high temporal resolution. The system was used together with a high-speed framing camera employing eight intensified CCD modules, with a frame-rate matching the laser pulse repetition rate. The diagnostic system was used to study the combustion in a truck-size HCCI engine, running at 1200 rpm using n-heptane as fuel. By using laser pulses with time separations as short as 70 μs, cycle-resolved image sequences of the formaldehyde distribution were obtained. Thus, with this technique it is possible to follow the formaldehyde formation and consumption processes within a single cycle. The combustion evolution was studied in terms of the rate and spatial structure of formaldehyde formation and consumption for different engine operating conditions, e.g. different stoichiometries. Also, the impact on the rate of heat-release was investigated.

  • 29. Persson, Håkan
    et al.
    Hildingsson, Leif
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Ruebel, Jochen
    Investigation of Boundary Layer Behavior in Hcci Combustion Using Chemiluminescence Imaging2005In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) (Part 6 of 6), 2005Conference paper (Refereed)
    Abstract [en]

    A five-cylinder diesel engine, converted to a single cylinder operated optical engine is run in Homogeneous Charge Compression Ignition (HCCI) mode. A blend of iso-octane and n-heptane is used as fuel. An experimental study of the horizontal boundary layer between the main combustion and the non-reacting surface of the combustion chamber is conducted as a function of speed, load, swirl and injection strategy. The combustion behaviour is monitored by chemiluminescence measurements. For all cases an interval from -10 to 16 crank angles after top dead center (CAD ATDC) in steps of one CAD are studied. One image-intensified camera observes the boundary layer up close from the side through a quartz cylinder liner while a second camera has a more global view from below to see more large scale structure of the combustion. The averaged chemiluminescence intensity from the HCCI combustion is seen to scale well with the rate of heat release. A boundary layer is defined and studied in detail between the main combustion volume and the piston crown surface as a function of crank angle. The boundary layer is found to be in the range from 2 to 4 mm for all cases by the definition used; however, the location for the measurements becomes more and more important as combustion becomes more inhomogeneous. To get accurate calculations, the level of noise must also be considered and definitions of boundary layer thickness should not be made at to low chemiluminescence intensity.

  • 30. Persson, Håkan
    et al.
    Hildingsson, Leif
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Ruebel, Jochen
    Investigation of Boundary Layer Behavior in Hcci Combustion Using Chemiluminescence Imaging2005In: Journal of fuels and lubricants (SAE transact.), ISSN 0096-736X, Vol. 14, no 4, p. 1358-1369Article in journal (Refereed)
  • 31. Persson, Håkan
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Remón, Alfredo
    Investigation of the Early Flame Development in Spark Assisted HCCI Combustion Using High Speed Chemiluminescence Imaging2007In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) (Part 5 of 8) Optical Diagnostics, 2007Conference paper (Refereed)
    Abstract [en]

    Auto-ignition with SI-compression ratio can be achieved by replacing some of the fresh charge by hot residuals. In this work an engine is run with a negative valve overlap (NVO) trapping hot residuals. By increasing the NVO, thus raising the initial charge temperature it is possible to investigate the intermediate zone between SI and HCCI as the amount of residuals is increased. Recent research has shown the potential of using spark assistance to aid gasoline HCCI combustion at some operating conditions, and even extend the operating regime into regions where unsupported HCCI combustion is impossible. In this work the influence of the spark is studied in a single cylinder operated engine with optical access. Combustion is monitored by in-cylinder pressure and simultaneous high speed chemiluminescence imaging. It is seen that even for large NVO and thus high residual fractions it is a growing SI flame that interacts with, and governs the subsequent HCCI combustion. Using the spark timing it is possible to phase the combustion timing even when the major part of the released heat is from HCCI combustion. The flame expansion speed is decreases for higher NVO, but prevails also for high residual fractions. A higher spark advance is found to compensate for the slower flame expansion up to a point. The auto-ignition process is found to be stratified for both spark assisted HCCI as well as for pure HCCI. For pure HCCI the initial front spreading velocity is found to be in the same order of magnitude as for the expansion speed of the SI flame. Calculations to estimate the crank angle of auto-ignition are performed based on cylinder pressure information providing good statistics on how the proportion of SI to HCCI behaves for different operating conditions.

  • 32. Richter, Mattias
    et al.
    Franke, Axel
    Alden, Marcus
    Hultqvist, Anders
    Lund Institute of Technology, Sweden.
    Johansson, Bengt
    Optical Diagnostics Applied to a Naturally Aspirated Homogeneous Charge Compression Ignition Engine1999Conference paper (Refereed)
    Abstract [en]

    Basic optical properties have been investigated in order to characterize the HCCI-combustion process. Basic optical properties of a Homogeneous Charge Compression Ignition (HCCI) engine have been investigated in order to characterize the combustion process. The absorption of light propagating through the combustion chamber has been spectrally resolved for four different fuels. Significant differences between the fuels could be detected. Complementary information could be obtained by recording spontaneous emission of radiation during combustion. Raman point measurements were used to quantify cycle-to-cycle variations of the equivalence ratio. The homogeneity of the charge was monitored by the use of two-dimensional tracer LIF. That method was also utilized to investigate the flame development. The experiments were performed in a six-cylinder, truck-sized engine with one cylinder modified to allow for optical access. The results obtained are believed to be valuable in future applications of optical diagnostics in similar environments.

  • 33. Richter, Mattias
    et al.
    Franke, Axel
    Engström, Johan
    Hultqvist, Anders
    Lund Institute of Technology, Sweden.
    Johansson, Bengt
    Alden, Marcus
    The Influence of Charge Inhomgeneity on the HCCI Combustion Process2000Conference paper (Refereed)
  • 34. Seyfried, Hans
    et al.
    Olofsson, Jimmy
    Sjöholm, Johan
    Richter, Mattias
    Aldén, Marcus
    Vressner, Andreas
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    High-Speed PLIF Imaging for Investigation of Turbulence Effects on Heat Release Rates in HCCI Combustion2007In: Session: Homogeneous Charge Compression Ignition (HCCI) (Part 4 of 8) Combustion Modeling / Optical Diagnostics, 2007Conference paper (Refereed)
    Abstract [en]

    High-speed laser diagnostics was utilized for single-cycle resolved studies of the fuel distribution in the combustion chamber of a truck-size HCCI engine. A multi-YAG laser system consisting of four individual Nd:YAG lasers was used for planar laser-induced fluorescence (PLIF) imaging of the fuel distribution. The fundamental beam from the lasers at 1064 nm was frequency quadrupled in order to obtain laser pulses at 266 nm suitable for excitation of acetone that was used as fuel tracer. Bursts of up to eight pulses with very short time separation were produced, allowing PLIF images with high temporal resolution to be captured within one single cycle event. The system was used together with a high-speed framing camera employing eight ICCD modules, with a frame-rate matching the laser pulse repetition rate. The combustion evolution was studied in terms of spatial distribution and rate of fuel consumption for different engine hardware configurations as well as operating conditions e.g. different stoichiometries and combustion phasing. Two different piston crown geometry were used for altering the degree of turbulence in the combustion chamber. In addition to the optical investigations, the impact of turbulence effects was also studied by calculating the rate of heat-release and combustion phasing from the pressure trace.

  • 35. Särner, Gustaf
    et al.
    Richter, Mattias
    Aldén, Marcus
    Hildingsson, Leif
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Simultaneous PLIF Measurements for Visualization of Formaldehyde- and Fuel- Distributions in a DI HCCI Engine2005In: SAE, Session: Combustion Diagnostics, 2005Conference paper (Refereed)
    Abstract [en]

    Simultaneous laser induced fluorescence (LIF) imaging of formaldehyde and a fuel-tracer have been performed in a direct-injection HCCI engine. A mix of N-heptane and iso-octane was used as fuel and Toluene as fluorescent tracer. The experimental setup involves two pulsed Nd:YAG lasers and two ICCD cameras. Frequency quadrupled laser radiation at 266 nm from one of the Nd:YAG lasers was used for excitation of the fuel tracer. The resulting fluorescence was detected with one of the ICCD cameras in the spectral region 270-320 nm. The second laser system provided frequency tripled radiation at 355 nm for excitation of Formaldehyde. Detection in the range 395-500 nm was achieved with the second ICCD. The aim of the presented work is to investigate the applicability of utilizing formaldehyde as a naturally occurring fuel marker. Formaldehyde is formed in the low temperature reactions (LTR) prior to the main combustion and should thus be present were fuel is located until it is consumed. Measurements were performed when injecting fuel early and late in the compression stroke. Early injection timing results in a homogeneous charge at the time of auto-ignition, while late timing gives a more stratified charge. The crank angle position at which measurements were performed was altered to cover the entire combustion cycle. The measurement images show instantaneous distributions of toluene and formaldehyde respectively. Images from both early and late injection and at all crank angle degrees show good spatial resemblance between toluene signal area and formaldehyde signal area. The work presented in this paper show that formaldehyde is a feasible alternative to traditional fuel tracers for visualizing fuels featuring low temperature reactions in HCCI combustion.

  • 36. Vressner, Andreas
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Study on Combustion Chamber Geometry Effects in an HCCI Engine Using High-Speed Cycle-Resolved Chemiluminescence Imaging2007In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) (Part 4 of 8) Combustion Modeling / Optical Diagnostics, 2007Conference paper (Refereed)
    Abstract [en]

    The aim of this study is to see how geometry generated turbulence affects the Rate of Heat Release (ROHR) in an HCCI engine. HCCI combustion is limited in load due to high peak pressures and too fast combustion. If the speed of combustion can be decreased the load range can be extended. Therefore two different combustion chamber geometries were investigated, one with a disc shape and one with a square bowl in piston. The later one provokes squish-generated gas flow into the bowl causing turbulence. The disc shaped combustion chamber was used as a reference case. Combustion duration and ROHR were studied using heat release analysis. A Scania D12 Diesel engine, converted to port injected HCCI with ethanol was used for the experiments. An engine speed of 1200 rpm was applied throughout the tests. The effect of air/fuel ratio and combustion phasing was also studied. The behavior of the heat release was correlated with high speed chemiluminescence imaging for both combustion chamber geometries. Optical access was enabled from beneath by a quartz piston and a 45 degree mirror. It was found that the square bowl in piston generates higher turbulence levels resulting in half the ROHR and twice as long combustion duration as the disc shaped combustion chamber. By using a resolution of 3 images per CAD, the fast gas movements during the entire HCCI combustion process could be studied inside the bowl.

  • 37. Vressner, Andreas
    et al.
    Strandh, Petter
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Tunestål, Per
    Johansson, Bengt
    Multiple Point Ion Current Diagnostics in An Hcci Engine2004In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) Combustion (Part 3 & 4), 2004Conference paper (Refereed)
    Abstract [en]

    Interest in ion current sensing for HCCI combustion arises when a feedback signal from some sort of combustion sensor is needed in order to determine the state of the combustion process. A previous study has revealed that ion current sensors in the form of spark plugs can be used instead of expensive piezoelectric transducers for HCCI combustion sensing. Sufficiently high ion current levels were achieved when using relatively rich mixtures diluted with EGR. The study also shows that it is not the actual dilution per se but the actual air/fuel equivalence ratio which is important for the signal level. Conclusions were made that it is possible to obtain information on combustion timing and oscillating wave phenomena from the measurements. However, the study showed that the ion current is local compared to the pressure which is global in the combustion chamber. This observation triggered the present study where the aim is to investigate the ion current at different locations in the combustion chamber. The ion current was measured simultaneously at seven locations in the combustion chamber. In order to achieve this, 6 spark plugs were fitted circumferentially in a spacer placed between the cylinder block and the head. The seventh spark plug was placed in the cylinder head. Individual DC sources of 85 volts were applied across the spark plug gaps. The present study indicates that the combustion timing seems to be dependent on the wall temperature at the different spark plug locations. The largest difference in timing between different locations in the combustion chamber was 2 CAD. The ion current amplitude varies with different spark plug locations up to 1.5 μA. The signal strength increases with decreasing air/fuel ratio and is also affected by dilution.

  • 38. Weinrotter, Martin
    et al.
    Wintner, Ernst
    Iskra, Kurt
    Neger, Theo
    Olofsson, Jimmy
    Seyfried, Hans
    Aldén, Marcus
    Lackner, Max
    Winter, Franz
    Vressner, Andreas
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Johansson, Bengt
    Optical Diagnostics of Laser-Induced and Spark Plug-Assisted Hcci2005In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) Combustion (Part 6 & 7), 2005Conference paper (Refereed)
    Abstract [en]

    HCCI (Homogeneous Charge Compression Ignition), laser-assisted HCCI and spark plug-assisted HCCI combustion was studied experimentally in a modified single cylinder truck-size Scania D12 engine equipped with a quartz liner and quartz piston crown for optical access. The aim of this study was to find out how and to what extent the spark, generated to influence or even trigger the onset of ignition, influences the auto-ignition process or whether primarily normal compression-induced ignition remains prevailing. The beam of a Q-switched Nd:YAG laser (5 ns pulse duration, 25 mJ pulse energy) was focused into the centre of the cylinder to generate a plasma. For comparison, a conventional spark plug located centrally in the cylinder head was alternatively used to obtain sparks at a comparable location. No clear difference in the heat releases during combustion between the three different cases of ignition start could be seen for the fuel of 80/20 iso-octane/n-heptane used. However, with optical diagnostic methods, namely PLIF (Planar Laser-Induced Fluorescence), Schlieren photography and chemiluminescence imaging, differences in the combustion process could be evaluated.

  • 39. Winter, Franz
    et al.
    Hultqvist, Anders
    Lunds Tekniska Högskola, Värme- och kraftteknik.
    Kopecek, Herbert
    Wintner, Ernst
    Lackner, Max
    Laser-Stimulated Ignition in a Homogeneous Charge Compression Ignition Engine2004In: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) Combustion (Part 3 & 4), 2004Conference paper (Refereed)
    Abstract [en]

    A laser-induced spark was generated inside the combustion chamber of a reciprocating engine running in Homogeneous Charge Compression Ignition (HCCI) mode to investigate the influence of the plasma on combustion performance. For a fuel consisting of 90% natural gas and 10% isooctane, the advance of combustion due to the plasma was found to be strong up to air excess ratios of λ = 2.3 and to cease completely above λ = 2.7. Combustion timing was advanced with increasing advance of plasma timing to a certain extent. The laser was able to sustain HCCI combustion even at much lower inlet temperatures than normally required without plasma. Inlet temperature changes of more than 10°C could not eliminate laser stimulated HCCI combustion. A potential application of laser-stimulated ignition is as a means to actively control HCCI combustion timing.

  • 40. Yu, R. X.
    et al.
    Bai, Xue-Song
    Vressner, Andreas
    Hultqvist, Anders
    Lunds Tekniska Högskola, Sweden.
    Johansson, Bengt
    Olofsson, Jimmy
    Seyfried, Hans
    Sjöholm, J.
    Richter, Mattias
    Aldén, Marcus
    Effect of Turbulence on HCCI Combustion2007In: Session: Homogeneous Charge Compression Ignition (HCCI) (Part 4 of 8) Combustion Modeling / Optical Diagnostics, 2007Conference paper (Refereed)
    Abstract [en]

    This paper presents large eddy simulation (LES) and experimental studies of the combustion process of ethanol/air mixture in an experimental optical HCCI engine. The fuel is injected to the intake port manifolds to generate uniform fuel/air mixture in the cylinder. Two different piston shapes, one with a flat disc and one with a square bowl, were employed to generate different in-cylinder turbulence and temperature field prior to auto-ignition. The aim of this study was to scrutinize the effect of in-cylinder turbulence on the temperature field and on the combustion process. The fuel tracer, acetone, is measured using laser induced fluorescence (LIF) to characterize the reaction fronts, and chemiluminescence images were recorded using a high speed camera, with a 0.25 crank angle degree resolution, to further illustrate the combustion process. Pressure in the cylinder is recorded in the experiments. Spatial and temporal resolved LES was used to gain information on the turbulence mixing, heat transfer and combustion process. It was shown that gas temperature in the piston bowl is generally higher than that in the squish, leading to an earlier ignition in the bowl. Compared to the disc engine, the square bowl engine has a higher temperature inhomogeneity owing to the turbulence wall heat transfer. The experimentally observed higher combustion duration and slower pressure rise rate in the square bowl engine as compared to the disc engine can be explained by the higher temperature inhomogeneity in the square bowl engine.

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