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Experimental and Numerical Assessment of Active Pre-chamber Ignition in Heavy Duty Natural Gas Stationary Engine

Lund University-Changle Li, Pablo Garcia Valladolid, Per Tunestal
Istituto Motori CNR-Carlo Beatrice
  • Technical Paper
  • 2020-01-0819
To be published on 2020-04-14 by SAE International in United States
Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on heavy duty engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of two pre-chambers with different nozzle orifice diameters, in a stationary heavy-duty engine for power generation, operating at different loads, equivalence ratios and spark timings. The engine was originally a 6-cylinder compression ignition engine which is here employed as a single cylinder engine and then suitably modified to host the pre-chamber (with its natural gas injection system and spark plug) with a new bowl piston to decrease compression ratio. A…
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Influence of Multiple Injection Strategies on Performance and Emissions for Methanol PPC operation in a Heavy-Duty CI Engine

Lund University-Amir Aziz, Martin Tuner
ISAE-ENSMA-Clarisse Pinto Dos Santos
  • Technical Paper
  • 2020-01-0556
To be published on 2020-04-14 by SAE International in United States
There is growing global interest in using renewable alcohols to reduce the greenhouse gases and the reliance on conventional fossil fuels. Recent studies show that methanol combined with Partially Premixed Combustion (PPC) provides clear performance and emission benefits compared to conventional diesel diffusion combustion. Nonetheless, a narrow operating window with simultaneously low NOx and HC emissions can be stated as the main PPC drawback in light load conditions when a single injection strategy is used. Thus, the present experimental study has been carried out to investigate the influence of multiple injection strategies on the performance and emissions with methanol fuel in partially premixed combustion. Specifically, the main objective is to improve the NOx-HC trade-off, as well as the gross indicated efficiency (GIE) compared to single injection strategy results. The work was performed with a single-cylinder heavy-duty engine, operated at 4 bar gross indicated mean effective pressure (IMEPg), and an engine speed of 1200 rpm. Double and triple injections were implemented with varying dwells, injection timings, and fuel mass proportions. The experimental results were analyzed with…
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Optical characterization of the combustion process inside a large-bore dual-fuel two-stroke marine engine by using multiple high-speed cameras

Lund University-Mattias Richter
Lund Univ-Alexios Matamis
  • Technical Paper
  • 2020-01-0788
To be published on 2020-04-14 by SAE International in United States
Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and…
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The transition from HCCI to PPC: Investigation of different injection timing on ignition and combustion characteristics in an optical PPC engine

Lund University-Miao Zhang, Saeed Derafshzan, Leilei Xu, Xue-Song Bai, Mattias Richter, Marcus Lundgren
  • Technical Paper
  • 2020-01-0559
To be published on 2020-04-14 by SAE International in United States
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the fully mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It is also a combination of auto-ignition mode, a fuel-rich premixed mode, and a diffusion combustion mode. To achieve high efficiency and low soot emission, the in-cylinder mixture process and combustion behavior of PPC are still to be further explored using laser diagnostic. In this paper, combined combustion deriving from three stages (HCCI stage, transition stage, PPC stage) was achieved by using double injection strategies changing from -220° to -8° after top dead centre (ATDC) in an optical heavy-duty CI engine. To analyze how the double injection effect the transition performance from HCCI to CI, spray development was recorded by Mie-scatter and natural luminosity of combustion was captured by a high-speed camera. The result shows double injection reshapes the transition trend of gross efficiency, ignition location, and combustion propagation compares to single injection. The cases in PPC region has the highest gross efficiency. With fuel injected into piston…
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Impact of multiple injection strategies on efficiency and combustion characteristics in an optical PPC engine

Lund University-Miao Zhang, Leilei Xu, Saeed Derafshzan, Xue-Song Bai, Mattias Richter, Marcus Lundgren
  • Technical Paper
  • 2020-01-1131
To be published on 2020-04-14 by SAE International in United States
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the fully mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It is also a combination of auto-ignition mode, a fuel-rich premixed mode, and a diffusion combustion mode. To achieve high efficiency and low soot emission, the in-cylinder mixture process and combustion behavior of PPC are still to be further explored using laser diagnostic. In this paper, a combined combustion deriving from three stages (HCCI stage, transition stage, PPC stage) was achieved by using multiple injection strategies changing from -220° to -8° after top dead center (ATDC) in an optical heavy-duty CI engine. To analyze the interaction between different combustion modes from HCCI, PPC, and CI, the natural luminosity of combustion was captured by high speed camera. The result shows that piston bowl and cylinder wall play an important role on mixture process in the transition stage and PPC stage. Besides, the interaction between different combustion modes result in different ignition behavior, combustion propagation and gross indicated efficiency.
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Numerical Optimization of Compression Ratio for a PPC Engine running on Methanol

Lund University-Erik Svensson, Sebastian Verhelst
  • Technical Paper
  • 2019-01-2168
Published 2019-12-19 by SAE International in United States
Partially premixed combustion (PPC) has shown to produce high gross indicated efficiencies while yielding lower pollutant emissions, such as oxides of nitrogen and soot, than conventional diesel combustion. Gasoline fuels with a research octane number (RON) of 60-70 have been proposed as optimal for PPC as they balance the trade-off between ensuring good combustion stability at low engine loads and avoiding excessive peak pressure rise rates at high loads. However, measures have to be taken when optimizing the engine operating parameters to avoid soot emissions. In contrast, methanol has a much lower propensity for soot formation. However, due to a higher RON of methanol the required intake temperature is higher for the same engine compression ratio to ensure auto-ignition at an appropriate timing. Increasing the compression ratio allows a lower intake temperature and improves combustion stability as well as engine brake efficiency. Nevertheless, a higher compression ratio generally increases in-cylinder heat losses and peak pressure. These effects were investigated in a simulation study, which combined 0-D and 1-D models, of a multi-cylinder heavy-duty Scania D13…
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Large Eddy Simulation of an Ignition Front in a Heavy Duty Partially Premixed Combustion Engine

Lund University-Christian Ibron, Hesameddin Fatehi, Mehdi Jangi, Xue-Song Bai
Published 2019-09-09 by SAE International in United States
In partially premixed combustion engines high octane number fuels are injected into the cylinder during the late part of the compression cycle, giving the fuel and oxidizer enough time to mix into a desirable stratified mixture. If ignited by auto-ignition such a gas composition can react in a combustion mode dominated by ignition wave propagation. 3D-CFD modeling of such a combustion mode is challenging as the rate of fuel consumption can be dependent on both mixing history and turbulence acting on the reaction wave. This paper presents a large eddy simulation (LES) study of the effects of stratification in scalar concentration (enthalpy and reactant mass fraction) due to large scale turbulence on the propagation of reaction waves in PPC combustion engines. The studied case is a closed cycle simulation of a single cylinder of a Scania D13 engine running PRF81 (81% iso-octane and 19% n-heptane). Two injection timings are investigated; start of injection at -17 CAD aTDC and -30 CAD aTDC. One-equation transported turbulence sub-grid closure is used for the unresolved momentum and scalar fluxes…
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Influence of Injection Strategies on Engine Efficiency for a Methanol PPC Engine

Lund University-Erik Svensson, Martin Tuner, Sebastian Verhelst
Published 2019-09-09 by SAE International in United States
Partially premixed combustion (PPC) is one of several advanced combustion concepts for the conventional diesel engine. PPC uses a separation between end of fuel injection and start of combustion, also called ignition dwell, to increase the mixing of fuel and oxidizer. This has been shown to be beneficial for simultaneously reducing harmful emissions and fuel consumption. The ignition dwell can be increased by means of exhaust gas recirculation or lower intake temperature. However, the most effective means is to use a fuel with high research octane number (RON). Methanol has a RON of 109 and a recent study found that methanol can be used effectively in PPC mode, with multiple injections, to yield high brake efficiency. However, the early start of injection (SOI) timings in this study were noted as a potential issue due to increased combustion sensitivity. Therefore, the present study attempts to quantify the changes in engine performance for different injection strategies. Simulations were performed on a heavy-duty multi-cylinder compression ignition engine fueled with methanol. Two operating conditions with different engine load were…
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Literature Review on Dual-Fuel Combustion Modelling

Lund University-Menno Merts, Sebastian Verhelst
Published 2019-09-09 by SAE International in United States
In the search for low greenhouse gas propulsion, the dual fuel engine provides a solution to use low carbon fuel at diesel-like high efficiency. Also a lower emission of NOx and particles can be achieved by replacing a substantial part of the diesel fuel by for example natural gas. Limitations can be found in excessively high heat release rate (combustion-knock), and high methane emissions. These limitations are strongly influenced by operating parameters and properties of the used (bio)-gas. To find the dominant relations between fuel properties, operating parameters and the heat release rate and methane emissions, a combustion model is beneficial. Such a model can be used for optimizing the process, or can even be used in real time control. As precursor for such a model, the current state of art of dual fuel combustion modelling is investigated in this work.The focus is on high speed dual fuel engines for heavy duty and marine applications, with a varying gas/diesel ratio. Modelling is limited to the closed part of the 4-stroke engine cycle. A methodology part…
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Learning Based Model Predictive Control of Combustion Timing in Multi-Cylinder Partially Premixed Combustion Engine

Lund University-Xiufei Li, Lianhao Yin, Per Tunestal, Rolf Johansson
  • Technical Paper
  • 2019-24-0016
Published 2019-09-09 by SAE International in United States
Partially Premixed Combustion (PPC) has shown to be a promising advanced combustion mode for future engines in terms of efficiency and emission levels. The combustion timing should be suitably phased to realize high efficiency. However, a simple constant model based predictive controller is not sufficient for controlling the combustion during transient operation. This article proposed one learning based model predictive control (LBMPC) approach to achieve controllability and feasibility. A learning model was developed to capture combustion variation. Since PPC engines could have unacceptably high pressure-rise rates at different operation points, triple injection is applied as a solvent, with the use of two pilot fuel injections. The LBMPC controller utilizes the main injection timing to manage the combustion timing. The cylinder pressure is used as the combustion feedback. The method is validated in a multi-cylinder heavy-duty PPC engine for transient control.
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