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  • 1.
    Cronhjort, Andreas
    KTH.
    Droplet Velocities in a Sliced Diesel Spray2001Conference paper (Refereed)
    Abstract [en]

    This paper gives a summary of particle image velocimetry (PIV) measurements performed in a sliced diesel spray. The slicing of the spray was necessary to achieve good image quality in the more dense regions of the spray. The images were double exposed to allow auto-correlation based velocimetry. The exposure time of each exposure was 100 ns, as that was the shortest possible exposure with the camera used. The illumination was achieved with a flashlight located at the opposite side of the spray, consequently the droplets were visible as dark shadows. The long exposure time limited the possibilities to measure high velocities, and therefore the velocities in the very rapidly moving spray core could not be measured, as the images were smeared out in the direction of the velocity. The resulting velocities were compared to velocities in the corresponding unsliced spray in the points where both sprays gave velocity data. The results were also compared with computer simulations. Some disagreements were found, and possible reasons for these are discussed.

  • 2.
    Cronhjort, Andreas
    Scania CV AB.
    Optical Studies in a Direct Injected Diesel Engine2005Conference paper (Other academic)
    Abstract [en]

    A heavy-duty diesel engine with optical access through an extended piston has been used to study diesel spray combustion. Conventional photography using a solid-state camera was adopted to image the flames. The images were parameterized using image processing software. Due to extended crevices and reduced stiffness as compared to the original engine, the effective compression ratio was slightly lower in the optical cylinder. To compensate for the lowered compression ratio, the inlet pressure as well as the inlet temperature were increased. As top dead center conditions regarding gas density and temperature were desired to be maintained, this approach resulted in an increased overall air to fuel ratio. However, despite these drawbacks, the engine allows for spray combustion studies under realistic diesel engine conditions regarding pressure and temperature. The inlet pressure was kept at 400 kPa absolute and the temperature was 325 K. To predict the air mass in the cylinder as accurately as possible, the exhaust back pressure was always kept equal to the inlet pressure. To minimize the thermal load on the piston, fuel was injected only when an image was to be exposed. This was also beneficial when estimating the air mass in the cylinder, as the temperature of the rest gas was quite low. A nozzle with eight orifices fitted to a common-rail injector was used to generate the sprays. The rail pressures used were 160 MPa and 220 MPa, the injected amount of fuel was varied between 80 mg and 240 mg.

  • 3.
    Cronhjort, Andreas
    KTH, Superseded Departments (pre-2005), Machine Design. Scania CV AB.
    Spray Visualization Using a Mechanical Slicing Device2000Conference paper (Refereed)
    Abstract [en]

    This paper describes a concept for gaining photographic access, at a high magnification level, to quite dense regions in liquid sprays, aiming primarily at photographic investigations of the spray and studies of the trailing edge with its associated large droplets. The slicing of the spray is achieved with two sharp edges, which cut out a thin sheet of the spray. The sheet of droplets is visualized with conventional shadow photography. The images acquired with the slicer are compared with images acquired without it, and even though some ligaments are identified as originating from the edges of the slit, the method is still considered as being beneficial, as the quality of the images is significantly enhanced.

  • 4.
    Cronhjort, Andreas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. Scania CV AB.
    Dahlén, Lars
    Diesel Flame Studies in an Optical Engine2004Conference paper (Refereed)
    Abstract [en]

    A diesel engine with optical access through an extended piston has been developed. It is based on a heavy duty truck engine and the purpose is to generate calibration data for computer simulation of spray combustion, hereby facilitating reliable combustion prediction using Computational Fluid Dynamics (CFD). Conventional photography using a solid-state camera was adopted to image the combustion. As the upper surface of the glass window in the piston is flat, the compression ratio of the engine is reduced to 12:1, in order to avoid that the spray plumes hit the glass surface. To compensate for the lowered compression ratio, the inlet pressure as well as the inlet temperature were increased. As top dead center conditions regarding gas density and temperature are desired to be maintained, this approach results in an increased overall air-to-fuel ratio. Additionally, the cylinder pressure decay due to the piston movement becomes slower than it should be at the present engine speed. However, despite these drawbacks, the engine allows for spray combustion studies under realistic diesel engine conditions regarding pressure and temperature. In the preliminary study the inlet pressure was 400 kPa absolute and the temperature was 450 K, resulting in a compression pressure of about 8.6 MPa at top dead center when the engine runs at 1200 rpm. To predict the air mass in the cylinder as accurately as possible, the exhaust back pressure is always kept equal to the inlet pressure. To minimize the thermal load on the piston, fuel is injected only during cycles when an image is exposed. This is also beneficial when estimating the air mass in the cylinder, as the temperature of the rest gas from the preceding cycle is quite low. In the preliminary study a nozzle with eight orifices fitted to a common-rail injector was used to generate the sprays. The orifice diameter was 190 µm. The rail pressure was 160 MPa and the injected amount of fuel was 80 mg. The resulting combustion was dominated by diffusion flames.

  • 5.
    Cronhjort, Andreas
    et al.
    KTH.
    Konstanzer, Dennis
    Scania (CFD).
    Analysis of a Diesel Spray Using a Mechanical Slicing Device2001Conference paper (Refereed)
    Abstract [en]

    This paper gives a summary of image velocimetry measurements performed in a sliced diesel spray. The slicing of the spray was necessary to achieve sufficient image quality in the more dense regions of the spray. The images were double exposed to allow auto-correlation based velocimetry. The illumination was achieved with a xenon flashlight behind the spray and consequently the droplets were visible as dark shadows. Images were acquired from different points downstream from the nozzle, and a number of different radii were employed at every position. In the images the smaller droplets seem to be spherical, while the larger ones are distorted due to high weber numbers. Computer simulations indicate that large droplets may reach high weber numbers when passing through the slit, and that some of these large droplets break up.

  • 6.
    Cronhjort, Andreas
    et al.
    Scania CV AB.
    Wåhlin, Fredrik
    Scania CV AB.
    Segmentation Algorithm for Diesel Spray Image Analysis2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 32, p. 5971-5980Article in journal (Refereed)
    Abstract [en]

    An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.

  • 7. Desantes, José
    et al.
    Arrègle, Jean
    López, Javier
    Cronhjort, Andreas
    Scania CVAB, Advanced Combustion. Engine Development, SE - 151 87 Södertälje, Sweden.
    Scaling Laws for Free Turbulent Gas Jets and Diesel-Like Sprays2006In: Atomization and sprays, ISSN 1044-5110, E-ISSN 1936-2684, Vol. 16, no 4, p. 443-474Article in journal (Refereed)
    Abstract [en]

    Scaling laws for free turbulent gas jets and diesel-like sprays are deduced and experimentally validated. The analysis is based on basic conservation equations and experimental evidence. As a new contribution, the effect of the Schmidt number on the scaling laws is analyzed and included, which leads to a more general set of normalized parameters. By analyzing the scaling laws, it is possible to obtain a clear comprehension of gas-jet or diesel-spray behavior, as well as an understanding of the relationship between input and output parameters. Two new parameters are introduced that characterize mass and momentum transfer in the radial direction of the gas jet or diesel spray, thus providing valuable information about the mixing process.

  • 8.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013In: SAE World Congress 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered.  In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency.

    In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 9.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013In: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, no 2, p. 739-750Article in journal (Refereed)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered. In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency. In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 10.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Divided Exhaust Period on Heavy-Duty Diesel Engines2012Conference paper (Refereed)
    Abstract [en]

    Divided Exhaust Period (DEP) has previously been studied on SI engines while results fromHD diesels are scarcer. In this paper the DEP concept has been numerically simulated on two HD dieselengines; one without EGR and one with high rates of short route EGR. The aim is to reduce fuelconsumption, residual gas content and to improve boost control, while current EGR rates are maintained.

    The central idea of the DEP concept is to let the initial high energy blow-down pulse feed theturbocharger, but bypass the turbine during the latter part of the exhaust stroke when back pressuredominates the pumping work. The exhaust flow from the cylinder is divided between two exhaust manifoldsof which one is connected to the turbine, and one bypasses the turbine. The flow split betweenthe manifolds is controlled with a variable valve train system.

    Results show a reduction of pumping losses for both engine configurations. In the non-EGRcase, the DEP concept offers the possibility to control the mass flow and pressure ratio over the turbine.This allows the turbocharger to operate in a high efficiency mode for a wide range of engine loadpoints. For the EGR case, there is less freedom in control of turbine mass flow, since the blow-downphase is used for both turbine work and EGR flow. Therefore the fuel consumption benefit is reduced.

    The conclusion of this paper is that the simulations of the DEP concept show improvements toengine performance and efficiency. In the case of high EGR rates it is shown that the EGR flow shouldnot be deducted from the blow-down phase.

  • 11.
    Holmberg, Ted
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Amplitude Influence on Pulsating Exhaust Flow Energy Utilization2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow. The operating points are defined by engine speed and boost pressure. From these values the isentropic turbine work is calculated and with the measured compressor work the mean turbine efficiency is estimated. The results show that more energy has to be provided to the turbine at larger exhaust manifold volumes to maintain a constant boost pressure, indicating that the efficiency of the turbine decreases. 

  • 12.
    Holmberg, Ted
    et al.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio. This trend was not replicated for the other single valve case B1, as pressure ratio only had a small influence on the flow coefficient. For the twin valve case A2, the pressure ratio influence was confined to the lower range of valve lifts as the limiting factor was the exhaust port outlet at higher valve lifts. The flow coefficient for the twin valve case B2 increased with pressure ratio in the mid-range of valve lifts.

  • 13.
    Kerres, Bertrand
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Nair, Vineeth
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Analysis of the Turbocharger Compressor Surge Margin Using a Hurst-Exponent-based Criterion2016In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 9, no 3Article in journal (Refereed)
    Abstract [en]

    Turbocharger compressors are limited in their operating range at low mass flows by compressor surge, thus restricting internal combustion engine operation at low engine speeds and high mean effective pressures. Since the exact location of the surge line in the compressor map depends on the whole gas exchange system, a safety margin towards surge must be provided. Accurate early surge detection could reduce this margin. During surge, the compressor outlet pressure fluctuates periodically. The Hurst exponent of the compressor outlet pressure is applied in this paper as an indicator to evaluate how close to the surge limit the compressor operates. It is a measure of the time-series memory that approaches zero for anti-persistence of the time series. That is, a Hurst exponent close to zero means a high statistical preference that a high value is followed by a low value, as during surge. Maps of a passenger-car sized turbocharger compressor with inlet geometries that result in different surge lines are measured on a cold gas stand. It is demonstrated that the Hurst exponent in fact decreases as the compressor moves towards surge, and that a constant value of the Hurst exponent can be used as a threshold for stable operation. Transient pressure signals of the compressor entering surge are analyzed in order to evaluate the time lag until surge can be detected using the Hurst exponent. Two surge cycles are usually needed to detect unstable operation. However, since the amplitude of these oscillations is relatively small for the first cycles, detection is possible before the oscillations grow into deep surge.

  • 14.
    Puttige, Anjan Rao
    et al.
    KTH.
    Hamberg, Robin
    KTH.
    Linschoten, Paul
    KTH.
    Reddy, G.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    Surge Detection Using Knock Sensors in a Heavy Duty Diesel Engine2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017Article in journal (Refereed)
    Abstract [en]

    Improving turbocharger performance to increase engine efficiency has the potential to help meet current and upcoming exhaust legislation. One limiting factor is compressor surge, an air flow instability phenomenon capable of causing severe vibration and noise. To avoid surge, the turbocharger is operated with a safety margin (surge margin) which, as well as avoiding surge in steady state operation, unfortunately also lowers engine performance. This paper investigates the possibility of detecting compressor surge with a conventional engine knock sensor. It further recommends a surge detection algorithm based on their signals during transient engine operation. Three knock sensors were mounted on the turbocharger and placed along the axes of three dimensions of movement. The engine was operated in load steps starting from steady state. The steady state points of operation covered the vital parts of the engine speed and load range. The collected data was analysed with the objective of extracting information of a surging or non-surging compressor. In the charging system studied, the knock sensors detected a profound frequency peak between 5.0 Hz to 7.0 Hz. Another surge related frequency component of about 25 kHz was also observed, dependent on the turbocharger speed. Two surge detection algorithms were evaluated, one based on short time Fourier transform (STFT) and one based on the correlation integral (CI). These algorithms where then validated against temperature measurements at the compressor inlet and visual observation of oscillations of the air inlet piping. The surge detection algorithms were compared for accuracy and repeatability. The accuracy of the methods was found to be 73 % and 71 % respectively when compared to the temperature rise in the compressor inlet.

  • 15.
    Rantanen, Pekka
    et al.
    Helsinki University of Technology.
    Valkonen, Antti
    Helsinki University of Technology.
    Cronhjort, Andreas
    KTH. Scania CV AB.
    Measurements of a Diesel Spray with a Normal Size Nozzle and a Large Scale Model1998Conference paper (Refereed)
    Abstract [en]

    Advantages of the large scale modeling of diesel sprays based on dimensional analysis were studied. Measurements of the spray tip penetration, opening angle, droplet size and velocity in a diesel spray have been made with a small nozzle and a large scale model of the same nozzle. Measurements were made with image analysis, diffraction drop size analyzer and laser Doppler anemometer. Results show that scaling might give us new possibilities to research diesel sprays.

  • 16.
    Rantanen, Pekka
    et al.
    Helsinki University of Technology.
    Valkonen, Antti
    Helsinki University of Technology.
    Cronhjort, Andreas
    KTH. Scania CV AB.
    Measurements of a Diesel Spray with a Normal Size Nozzle and a Large-Scale Model1999In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 20, p. 545-551Article in journal (Refereed)
    Abstract [en]

    Advantages of the large-scale modeling of diesel sprays based on dimensional analysis were studied. Measurements of the spray tip penetration, spray angle, droplet size and velocity in a diesel spray have been made with a small nozzle and a large-scale model of the same nozzle. Measurements were made with image analysis, diffraction drop size analyzer and laser Doppler anemometer. Results show that scaling might give us new possibilities to research diesel sprays.

  • 17.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Fuel Sprays for Premixed Compression Ignited Combustion: Characteristics of Impinging Sprays2004In: SAE 2004 World Congress & Exhibition Technical Papers: Diesel Fuel Injection & Sprays (Part 3 & 4), 2004, Vol. 01-1776, p. 2004-01-1776-Conference paper (Refereed)
    Abstract [en]

    For homogeneous charge compression ignition (HCCI) engines with direct-injected fuel (also called PCI, Pre-mixed Compression Ignition), it is important to achieve a lean and homogeneous mixture before ignition. For this purpose, impinging diesel sprays have proven to be useful. In this study, an evaluation of the overall air/fuel ratio of such sprays was made in a test rig. The test rig consists of a pressurized vessel with optical access and a Common Rail (CR) fuel injection system. The investigation was made for impinging spray nozzles with different impingement angles and orifice diameters. Three gas back pressures and three injection pressures were evaluated. The evaluation was based on images of the fuel sprays taken in the test rig. The fuel spray images were automatically processed using in-house developed software. The results of the investigation points out some important factors to obtain a lean spray, (a high air/fuel ratio). The investigation also points out some factors that give a low spray penetration for a certain injected mass of fuel.

  • 18.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Impinging Diesel Sprays2008In: Atomization and sprays, ISSN 1044-5110, E-ISSN 1936-2684, Vol. 18, no 2, p. 97-127Article in journal (Refereed)
    Abstract [en]

    Diesel fuel sprays from a common-rail injector have been optically investigated with respect to their macroscale characteristics. The tested nozzle designs were of standard plain orifice type, as well as the impinging-spray type, in which two orifices intersect at a specific angle at the exit. Testing was conducted using a pressurized vessel at room temperature. The impinging sprays were found to be low penetrating and widely dispersed compared to the nonimpinging sprays. The shape of the impinging sprays was as one homogeneous spray with no trace of individual sprays. It was found that impinging diesel sprays can be predicted in a manner similar to standard nonimpinging sprays, using a dimensionless penetration correlation. The cone angle of the impinging sprays increases with the impingement angle, and in contrast to nonimpinging sprays, appears insensitive to ambient density. The results indicate that the impinging spray has a larger spray volume at lower ambient densities. However, at higher ambient densities, the volume of the nonimpinging sprays is larger.

  • 19.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Olofsson, Ulf
    KTH, Superseded Departments (pre-2005), Machine Design.
    Ångström, Hans-Erik
    KTH, Superseded Departments (pre-2005), Machine Design.
    Effect of Injection Pressure and Engine Speed on Air/Fuel Mixing and Emissions in a Pre-Mixed Compression Ignited (PCI) Engine using Diesel Fuel2004In: 2004 Powertrain & Fluid Systems Conference & Exhibition Technical Papers, 2004, Vol. 01-2989, p. 2004-01-2989-Conference paper (Refereed)
    Abstract [en]

    PCI combustion of diesel fuel was accomplished in a direct-injected heavy-duty single-cylinder research engine. An impinging spray nozzle combined with a shallow bowl piston design offered a short air/fuel mixing time. Low HC and CO emissions were observed compared to fully premixed operation using n-heptane. A method for evaluating the air/fuel mixing process has been established by quantifying the in-cylinder air/fuel heterogeneity with the NOx emission. The results indicate that high injection pressure and engine speed are favorable for a fast mixing process. The injection pressure had a small impact on HC and CO emissions, while the engine speed had a larger impact. There were no correlation between air/fuel mixing time and HC and CO emissions.

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