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Technical Paper

Optical Diagnostics of Spray Characteristics and Soot Volume Fractions of n-Butanol, n-Octanol, Diesel, and Hydrotreated Vegetable Oil Blends in a Constant Volume Combustion Chamber

2019-01-15
2019-01-0019
The effects of using n-butanol, n-octanol, fossil Diesel, hydrotreated vegetable oil (HVO), and blends of these fuels on spray penetration, flame and soot characteristics were investigated in a high-pressure high-temperature constant volume combustion chamber designed to mimic a heavy duty Diesel engine. Backlight illumination was used to capture liquid and vapor phase spray images with a high-speed camera. The flame lift-off length (LOL) and ignition delay were determined by analyzing OH* chemiluminescence images. Laser extinction diagnostics were used to measure the spatially and temporally resolved soot volume fraction. The spray experiments were performed by injecting fuels under non-combusting (623 K) and combusting (823 K) conditions at a fixed ambient air density of 26 kg/m3. A Scania 0.19 mm single straight hole injector and Scania XPI common rail fuel supply system were used to produce injection pressures of 120 MPa and 180 MPa.
Journal Article

Water Injection Benefits in a 3-Cylinder Downsized SI-Engine

2019-01-15
2019-01-0034
With progressing electrification of automotive powertrains and demands to meet increasingly stringent emission regulations, a combination of an electric motor and downsized turbocharged spark-ignited engine has been recognized as a viable solution. The SI engine must be optimized, and preferentially downsized, to reduce tailpipe CO2 and other emissions. However, drives to increase BMEP (Brake Mean Effective Pressure) and compression ratio/thermal efficiency increase propensities of knocking (auto-ignition of residual unburnt charge before the propagating flame reaches it) in downsized engines. Currently, knock is mitigated by retarding the ignition timing, but this has several limitations. Another option identified in the last decade (following trials of similar technology in aircraft combustion engines) is water injection, which suppresses knocking largely by reducing local in-cylinder mixture temperatures due to its latent heat of vaporization.
Technical Paper

A Method to Evaluate the Compression Ratio in IC Engines with Porous Thermal Barrier Coatings

2018-09-10
2018-01-1778
The compression ratio is an important engine design parameter. It determines to a large extend engine properties like the achievable efficiency, the heat losses from the combustion chamber and the exhaust losses. The same properties are affected by insulation of the combustion chamber. It is therefore especially important to know the compression ratio when doing experiments with thermal barrier coatings (TBC). In case of porous TBCs, the standard methods to measure the compression ratio can give wrong results. When measuring the compression ratio by volume, using a liquid, it is uncertain if the liquid fills the total porous volume of the coating. And for a thermodynamic compression ratio estimation, a model for the heat losses is needed, which is not available when doing experiments with insulation. The subject of this paper is the evaluation of an alternative method to assess the compression ratio.
Technical Paper

Combustion Characteristics for Partially Premixed and Conventional Combustion of Butanol and Octanol Isomers in a Light Duty Diesel Engine

2017-10-08
2017-01-2322
Reducing emissions and improving efficiency are major goals of modern internal combustion engine research. The use of biomass-derived fuels in Diesel engines is an effective way of reducing well-to-wheels (WTW) greenhouse gas (GHG) emissions. Moreover, partially premixed combustion (PPC) makes it possible to achieve very efficient combustion with low emissions of soot and NOx. The objective of this study was to investigate the effect of using alcohol/Diesel blends or neat alcohols on emissions and thermal efficiency during PPC. Four alcohols were evaluated: n-butanol, isobutanol, n-octanol, and 2-ethylhexanol. The alcohols were blended with fossil Diesel fuel to produce mixtures with low cetane numbers (26-36) suitable for PPC. The blends were then tested in a single cylinder light duty (LD) engine. To optimize combustion, the exhaust gas recirculation (EGR) level, lambda, and injection strategy were tuned.
Technical Paper

Transient Responses of Various Ammonia Formation Catalyst Configurations for Passive SCR in Lean-Burning Gasoline Engines under Various Real Engine Conditions.

2016-04-05
2016-01-0935
Passive selective catalyst reduction (SCR) systems can be used as aftertreatment systems for lean burn spark ignition (SI)-engines. Their operation is based on the interaction between the engine, an ammonia formation catalyst (AFC), and an SCR catalyst. Under rich conditions the AFC forms ammonia, which is stored in the SCR catalyst. Under lean conditions, the SCR catalyst reduces the engine out NOx using the stored NH3. This study compared the ammonia production and response times of a standard three way catalyst (TWC) and a Pd/Al2O3 catalyst under realistic engine operating conditions. In addition, the relationships between selected engine operating parameters and ammonia formation over a TWC were investigated, considering the influence of both the chosen load point and the engine settings.
Technical Paper

Comparison of Lab Versus Engine Tests In the Development of a Highly Efficient Ammonia Formation Catalyst for a Passive SCR System

2015-09-06
2015-24-2504
Commercial three way catalysts have limited capacity towards reducing NOx in the presence of excessive oxygen. This prevents lean-burn combustion concepts from meeting legislative emission standards. A solution towards decreasing NOx emissions in the presence of excess air is the use of a passive-SCR system. Under rich conditions ammonia is formed over an ammonia formation catalyst, the ammonia is stored in the SCR and in its turn reacts with the NOx under lean engine conditions. Here up-scaled Pt/Al2O3 and Pd/Al2O3 catalysts as well as a commercially Pd-Rh based three-way catalyst (TWC) are evaluated using both engine and further lab-scale tests. The purpose of these tests is to compare the ammonia production for the various catalysts under various lambda values and temperatures by means of engine and lab scale tests. The Pd/Al2O3 showed little sensitivity to temperature both under engine and lab scale experiments.
Technical Paper

Emission Reduction Technologies for the Future Low Emission Rail Diesel Engines: EGR vs SCR

2013-09-08
2013-24-0087
The EU emission standards for new rail Diesel engines are becoming even more stringent. EGR and SCR technologies can both be used to reduce NOx emissions; however, the use of EGR is usually accompanied by an increase in PM emissions and may require a DPF. On the other hand, the use of SCR requires on-board storage of urea. Thus, it is necessary to study these trade-offs in order to understand how these technologies can best be used in rail applications to meet new emission standards. The present study assesses the application of these technologies in Diesel railcars on a quantitative basis using one and three dimensional numerical simulation tools. In particular, the study considers a 560 kW railcar engine with the use of either EGR or SCR based solutions for NOx reduction. The NOx and PM emissions performances are evaluated over the C1 homologation cycle.
Technical Paper

Effects of Variable Inlet Valve Timing and Swirl Ratio on Combustion and Emissions in a Heavy Duty Diesel Engine

2012-09-10
2012-01-1719
In order to avoid the high CO and HC emissions associated with low temperature when using high levels of EGR, partially premixed combustion is an interesting possibility. One way to achieve this combustion mode is to increase the ignition delay by adjusting the inlet valve closing timing, and thus the effective compression ratio. The purpose of this study was to investigate experimentally the possibilities of using late and early inlet valve closure to reduce NOx emissions without increasing emissions of soot or unburned hydrocarbons, or fuel consumption. The effect of increasing the swirl number (from 0.2 to 2.5) was also investigated. The combustion timing (CA50) was kept constant by adjusting the start of injection and the possibilities of optimizing combustion using EGR and high injection pressures were investigated. Furthermore, the airflow was kept constant for a given EGR level.
Technical Paper

Numerical Analysis of Combustion and Emissions Formation in a Heavy Duty DME Engine

2012-04-16
2012-01-0156
When using dimethyl ether (DME) to fuel diesel engines at high load and speed, applying high amounts of exhaust gas recirculation (EGR) to limit NOX emissions, carbon monoxide (CO) emissions are generally high. To address this issue, the combustion and emission processes in such engines were analyzed with the three-dimensional CFD KIVA3V code. The combustion sub-mechanism (76 species and 375 reactions) was validated by comparing simulated ignition delays and flame velocities to reference data under diesel-like and atmospheric conditions, respectively. In addition, simulated and experimentally determined rate of heat release (RoHR) curves and emission data were compared for a heavy-duty single-cylinder DME engine (displaced volume, 2.02 liters) with DME-adapted piston and nozzle geometries. The simulated RoHR curves captured the main features of the experimentally measured curves, but deviated in the premixed (higher peak) and late combustion phases (too high).
Journal Article

Valve Profile Adaptation, Stratification, Boosting and 2-Stroke Strategies for Raising Loads of Gasoline HCCI Engines

2012-04-16
2012-01-1108
The development of high efficiency powertrains is a key objective for car manufacturers. One approach for improving the efficiency of gasoline engines is based on homogeneous charge compression ignition, HCCI, which provides higher efficiency than conventional strategies. However, HCCI is only currently viable at relatively low loads, primarily because at high loads it involves rapid combustion that generates pressure oscillations in the cylinder (ringing), and partly because it gives rise to relatively high NOX emissions. This paper describes studies aimed at increasing the viability of HCCI combustion at higher loads by using fully flexible valve trains, direct injection with charge stratification (SCCI), and intake air boosting. These approaches were complemented by using EGR to control NOX emissions by stoichiometric operation, which enables the use of a three-way catalyst.
Technical Paper

Effects of Varying Engine Settings on Combustion Parameters, Emissions, Soot and Temperature Distributions in Low Temperature Combustion of Fischer-Tropsch and Swedish Diesel Fuels

2009-11-02
2009-01-2787
It has been previously shown that engine-out soot emissions can be reduced by using Fischer-Tropsch (FT) fuels, due to their lack of aromatics, compared to conventional Diesel fuels. In this investigation the engine-out emissions and fuel consumption parameters of an FT fuel derived from natural gas were compared to those of Swedish low sulfur diesel (MK1) when used in Low Temperature Combustion mode in a single cylinder heavy-duty diesel engine. The effects of varying Needle Opening Pressure (NOP), Charge Air Pressure (CAP) and Exhaust Gas Recirculation (EGR) according to an experimental design on the measured variables were also assessed. CAP and EGR were found to be the most significant factors for the combustion and emission parameters of both fuels. Increases in CAP resulted in lower soot emissions due to enhanced charge mixing, however NOx emissions rose as CAP increased.
Technical Paper

Role of Late Soot Oxidation for Low Emission Combustion in a Diffusion-controlled, High-EGR, Heavy Duty Diesel Engine

2009-11-02
2009-01-2813
Soot formation and oxidation are complex and competing processes during diesel combustion. The balance between the two processes and their history determines engine-out soot values. Besides the efforts to lower soot formation with measures to influence the flame lift-off distance for example or to use HCCI-combustion, enhancement of late soot oxidation is of equal importance for low-λ diffusion-controlled low emissions combustion with EGR. The purpose of this study is to investigate soot oxidation in a heavy duty diesel engine by statistical analysis of engine data and in-cylinder endoscopic high speed photography together with CFD simulations with a main focus on large scale in-cylinder gas motion. Results from CFD simulations using a detailed soot model were used to reveal details about the soot oxidation.
Journal Article

Effects of High Injection Pressure, EGR and Charge Air Pressure on Combustion and Emissions in an HD Single Cylinder Diesel Engine

2009-11-02
2009-01-2815
When increasing EGR from low levels to a level that corresponds to low temperature combustion, soot emissions initially increase due to lower soot oxidation before decreasing to almost zero due to very low soot formation. At the EGR level where soot emissions start to increase, the NOx emissions are low, but not sufficiently low to comply with future emission standards and at the EGR level where low temperature combustion occurs CO and HC emissions are too high. The purpose of this study was to investigate the possibilities for shifting the so-called soot bump (where soot levels are increased) to higher EGR levels, or to reduce the magnitude of the soot bump using very high injection pressures (up to 240 MPa) while reducing the NOx emissions using EGR. The possibility of reducing the CO and HC emissions at high EGR levels due to the increased mixing caused by higher injection pressure was also investigated and the flame was visualized using an endoscope at chosen EGR values.
Technical Paper

A LIF-study of OH in the Negative Valve Overlap of a Spark-assisted HCCI Combustion Engine

2008-04-14
2008-01-0037
Future requirements for emission reduction from combustion engines in ground vehicles might be met by using the HCCI combustion concept. In this study, negative valve overlap (NVO) and low lift, short duration, camshaft profiles, were used to initiate HCCI combustion by increasing the internal exhaust gas recirculation (EGR) and thus retaining sufficient thermal energy for chemical reactions to occur when a pilot injection was introduced prior to TDC, during the NVO. One of the crucial parameters to control in HCCI combustion is the combustion phasing and one way of doing this is to vary the relative ratio of fuel injected in pilot and main injections. The combustion phasing is also influenced by the total amount of fuel supplied to the engine, the combustion phasing is thus affected when the load is changed. This study focuses on the reactions that occur in the highly diluted environment during the NVO when load and pilot to main ratio are changed.
Technical Paper

Performance of a Heavy Duty DME Diesel Engine - an Experimental Study

2007-10-30
2007-01-4167
Combustion characteristics of dimethyl ether, DME, have been investigated experimentally, in a heavy duty single cylinder engine equipped with an adapted common rail fuel injection system, and the effects of varying injection timing, rail pressure and exhaust gas recirculation on the combustion and emission parameters. The results show that DME combustion does not produce soot and with the use of exhaust gas recirculation NOX emissions can also be reduced to very low levels. However, high injection pressure and/or a DME adopted combustion system is required to improve the mixing process and thus reduce the combustion duration and carbon monoxide emissions.
Technical Paper

Optical study of HCCI Combustion using NVO and an SI Stratified Charge

2007-09-16
2007-24-0012
The effects of using an SI stratified charge in combination with HCCI combustion on combustion phasing, rate of heat release and emissions were investigated in engine experiments to identify ways to extend the operational range of HCCI combustion to lower loads. In the experiments an optical single-cylinder engine equipped with a piezo electric outward-opening injector and operated with negative valve overlap (NVO) and low lift, short duration, camshaft profiles, was used to initiate HCCI combustion by increasing the exhaust gas recirculation (EGR) and thus retaining sufficient thermal energy to reach auto-ignition temperatures. Two series of experiments with full factorial designs were performed, to investigate how the tested parameters (amounts of fuel injected in pilot injections and main injections, stratification injection timing and spark-assistance) influenced the combustion.
Technical Paper

Reduction of Soot Emissions from a Direct Injection Diesel Engine using Water-in-Diesel Emulsion and Microemulsion Fuels

2007-04-16
2007-01-1076
The emissions from a direct injection diesel engine measured according to the ECE R49 13-mode cycle and as a function of exhaust gas recirculation are compared for diesel fuel without water addition, and for water-in-diesel as emulsion and microemulsion. The effect of water addition on the soot emissions was remarkably strong for both the emulsion and microemulsion fuels. The average weighted soot emission values for the 13-mode cycle were 0.0024 and 0.0023 g/kWh for the two most interesting emulsion and microemulsion fuels tested, respectively; 5-fold lower than the US 2007 emission limit.
Technical Paper

Ion Current Sensing in an Optical HCCI Engine with Negative Valve Overlap

2007-01-23
2007-01-0009
Ion current sensors have high potential utility for obtaining feedback signals directly from the combustion chamber in internal combustion engines. This paper describes experiments performed in a single-cylinder optical engine operated in HCCI mode with negative valve overlap to explore this potential. A high-speed CCD camera was used to visualize the combustion progress in the cylinder, and the photographs obtained were compared with the ion current signals. The optical data indicate that the ions responsible for the chemiluminescence from the HCCI combustion have to be in contact with the sensing electrode for an ion current to start flowing through the measurement circuit. This also means that there will be an offset between the time at which 50% of the fuel mass has burned and 50% of the ion current peak value is reached, which is readily explained by the results presented in the paper.
Technical Paper

Experimental and Numerical Investigation of Split Injections at Low Load in an HDDI Diesel Engine Equipped with a Piezo Injector

2006-10-16
2006-01-3433
In order to investigate the effects of split injection on emission formation and engine performance, experiments were carried out using a heavy duty single cylinder diesel engine. Split injections with varied dwell time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the selected parameters, other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezo-electric injector. To interpret the observed phenomena, engine CFD simulations using the KIVA-3V code were also made. The results show that reductions in NOx emissions and brake specific fuel consumption were achieved for short dwell times whereas they both were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of single injections.
Technical Paper

Low Temperature Combustion in a Heavy Duty Diesel Engine Using High Levels of EGR

2006-04-03
2006-01-0075
The possibilities for extending the range of engine loads in which soot and NOx emissions can be minimised by using low temperature combustion in conjunction with high levels of EGR was investigated in a series of experiments with a single cylinder research engine. The results show that very low levels of both soot and NOx emissions can be achieved at engine loads up to 50 % by reducing the compression ratio to 14 and applying high levels of EGR (up to approximately 60 %). Unfortunately, the low temperature combustion is accompanied by increases in fuel consumption and emissions of both HC and CO. However, these drawbacks can be reduced by advancing the injection timing. The research engine was a 2 litre direct injected (DI), supercharged, heavy duty, single cylinder diesel engine with a geometry based on Volvo's 12 litre engine, and the amount of EGR was increased by adjusting the exhaust back pressure while keeping the charge air pressure constant.
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