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Technical Paper

Analysis of the Effects of Certain Alcohol and Furan-Based Biofuels on Controlled Auto Ignition

2012-04-16
2012-01-1135
For gasoline engines controlled autoignition provides the vision of enabling the fuel consumption benefit of stratified lean combustion systems without the drawback of additional NOx aftertreatment. In this study the potential of certain biofuels on this combustion system was assessed by single-cylinder engine investigations using the exhaust strategy "combustion chamber recirculation" (CCR). For the engine testing sweeps in the internal EGR rate with different injection strategies as well as load sweeps were performed. Of particular interest was to reveal fuel differences in the achievable maximal load as well as in the NOx emission behavior. Additionally, experiments with a shock tube and a rapid compression machine were conducted in order to determine the ignition delay times of the tested biofuels concerning controlled autoignition-relevant conditions.
Technical Paper

Analysis of the Emission Conversion Performance of Gasoline Particulate Filters Over Lifetime

2019-09-09
2019-24-0156
Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Especially for coated GPF applications, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. The paper presents key-findings for the different GPF application variants. In the first part, experimental GPF ash loading results are presented. Ash accumulates as thin wall layers and short plugs, but does not penetrate into the wall. However, it suppresses deep bed filtration of soot, initially decreasing the soot-loaded backpressure. For the emission calibration, the non-linear backpressure development complicates the soot load monitoring, eventually leading to compromises between high safety against soot overloading and a low number of active regenerations.
Technical Paper

Balancing of Engine Oil Components in a DI Diesel Engine with Exhaust Gas Aftertreatment

2007-07-23
2007-01-1923
The influence of oil related emissions became more important in the past due to reduced engine-out emissions of combustion engines. Additionally the efficiency of exhaust gas after treatment components is influenced by oil derived components. A balancing of relevant engine oil components (Ca, Mg, Zn, P, S, Mo, B, Fe, Al, Cu) is presented in this paper. The oil components deposited in the combustion chamber, in the exhaust system as well as in the aftertreatment devices were determined and quantified. Therefore a completely cleaned DI Diesel engine with oxidation catalyst, Diesel particulate filter (DPF) and NOx adsorber catalyst (LNT) was operated in different operating conditions for 500 h in a development test cell. The operation included lean/rich cycling for NOx trap regeneration. After finishing the 500 h test procedure the engine was completely disassembled and all deposits were analyzed.
Technical Paper

Catalyst Aging Method for Future Emissions Standard Requirements

2010-04-12
2010-01-1272
This paper describes an alternative catalyst aging process using a hot gas test stand for thermal aging. The solution presented is characterized by a burner technology that is combined with a combustion enhancement, which allows stoichiometric and rich operating conditions to simulate engine exhaust gases. The resulting efficiency was increased and the operation limits were broadened, compared to combustion engines that are typically used for catalyst aging. The primary modification that enabled this achievement was the recirculation of exhaust gas downstream from catalyst back to the burner. The burner allows the running simplified dynamic durability cycles, which are the standard bench cycle that is defined by the legislation as alternative aging procedure and the fuel shut-off simulation cycle ZDAKW. The hot gas test stand approach has been compared to the conventional engine test bench method.
Technical Paper

Characterization of Oxygenated-Fuel Combustion by Quantitative Multiscalar SRS/LIF Measurements in a Diesel-Like Jet

2018-09-28
2018-01-5037
Due to experimental challenges, combustion of diesel-like jets has rarely been characterized by laser-based quantitative multiscalar measurements. In this work, recently developed laser diagnostics for combustion temperature and the concentrations of CO, O2, and NO are applied to a diesel-like jet, using a highly oxygenated fuel. The diagnostic is based on spontaneous Raman scattering (SRS) and laser-induced fluorescence (LIF) methods. Line imaging yields multiscalar profiles across the jet cross section. Measurements turn out to be particularly accurate, because near-stoichiometric combustion occurs in the central region of the jet. Thereby, experimental cross-influences by light attenuation and interfering emissions are greatly reduced compared to the combustion of conventional, sooting diesel fuel jets. This is achieved by fuel oxygenation and enhanced premixing.
Technical Paper

Cold Start Emission Reduction by Barrier Discharge

2000-10-16
2000-01-2891
Dielectric barrier discharge (DBD) offers the advantage to excite and dissociate molecules in the exhaust gas stream. Those dissociated and excited species are oxidizing or reducing harmful exhaust gas components. The advantage of a plasma chemical system in comparison to a catalytic measure for exhaust gas treatment is the instantaneous activity at ambient temperature from the starting of the engine. The investigations reviewed in this paper are dealing with the plasma chemical oxidation of hydrocarbons in the exhaust gas stream during cold start conditions. The article concerns the design and development of a plasma-system in order to decrease the hydrocarbon emissions from engine start till catalyst light off. Vehicle results in the New European Driving Cycle show a hydrocarbon conversion of more than 42% in the first 11 seconds from engine start. In this period nearly all types of hydrocarbon were reduced.
Journal Article

Cylinder Pressure Based Fuel Path Control for Non-Conventional Combustion Modes

2015-09-06
2015-24-2508
Model-based control strategies along with an adapted calibration process become more important in the overall vehicle development process. The main drivers for this development trend are increasing numbers of vehicle variants and more complex engine hardware, which is required to fulfill the more and more stringent emission legislation and fuel consumption norms. Upcoming fundamental changes in the homologation process with EU 6c, covering an extended range of different operational and ambient conditions, are suspected to intensify this trend. One main reason for the increased calibration effort is the use of various complex aftertreatment technologies amongst different vehicle applications, requiring numerous combustion modes. The different combustion modes range from heating strategies for active Diesel Particulate Filter (DPF) regeneration or early SCR light-off and rich combustion modes to purge the NOx storage catalyst (NSC) up to partially premixed combustion modes.
Journal Article

Impact of Biomass-Derived Fuels on Soot Oxidation and DPF Regeneration Behavior

2013-04-08
2013-01-1551
To comply with the new regulations on particulate matter emissions, the manufacturers of light-duty as well as heavy-duty vehicles more commonly use diesel particulate filters (DPF). The regeneration of DPF depends to a significant extent on the properties of the soot stored. Within the Cluster of Excellence "Tailor-Made Fuels from Biomass (TMFB)" at RWTH Aachen University, the Institute for Combustion Engines carried out a detailed investigation program to explore the potential of future biofuel candidates for optimized combustion systems. The experiments for particulate measurements and analysis were conducted on a EURO 6-compliant High Efficiency Diesel Combustion System (HECS) with petroleum-based diesel fuel as reference and a today's commercial biofuel (i.e., FAME) as well as a potential future biomass-derived fuel candidate (i.e., 2-MTHF/DBE). Thermo gravimetric analyzer (TGA) was used in this study to evaluate the oxidative reactivity of the soot.
Technical Paper

Injection Rate Shaping Investigations on a Small – Bore DI Diesel Engine

2009-04-20
2009-01-0850
So far, the effect of injection rate shaping on the diesel combustion in small-bore DI diesel engines has not been extensively investigated, especially at high part load conditions with high EGR rates. The benefit of injection rate shaping is already verified for heavy duty engines at high load conditions with and without EGR. For this investigation, single cylinder engine investigations were conducted at the VKA / RWTH Aachen University. In order to meet the future NOx legislation limits like US-Tier2Bin5 it is crucial to reduce NOx especially at the high load points of the certification cycles, as FTP75 or US06. For the single cylinder investigations two part load points were chosen, which have relevance for the mentioned certification cycles. The experimental work focuses on different rate shapes as rectangular (Common-Rail type), ramp and boot shape at high EGR rates.
Technical Paper

Internal and External Measures for Catalyst Light-Off Support

2015-09-06
2015-24-2501
Within a project of the Research Association for Combustion Engines e.V., different measures for rising the temperature of exhaust gas aftertreatment components of both a passenger car and an industrial/commercial vehicle engine were investigated on a test bench as well as in simulation. With the passenger car diesel engine and different catalyst configurations, the potential of internal and external heating measures was evaluated. The configuration consisting of a NOx storage catalyst (NSC) and a diesel particulate filter (DPF) illustrates the potential of an electrically heated NSC. The exhaust aftertreatment system consisting of a diesel oxidation catalyst (DOC) and a DPF shows in simulation how variable valve timing in combination with electric heated DOC can be used to increase the exhaust gas temperature and thus fulfill the EU6 emission limits.
Technical Paper

Simulation and Optical Analysis of Oil Dilution in Diesel Regeneration Operation

2011-08-30
2011-01-1844
High levels of exhaust temperature or rich mixtures are necessary for the regeneration of today's diesel particulate filters or NOx catalysts. Therefore, late main injection or post injection is an effective strategy but leads to the well-known problem of lubricating oil dilution depending on the geometry, rail pressure and injection strategy. In this paper a method is developed to simulate fuel entrainment into the lubricating oil wall film in the diesel combustion chamber to predict oil dilution in an early design stage prior to hardware availability for durability testing. The simulation method integrates a newly developed droplet-film interaction model and is compared to results of an optical single-cylinder diesel engine and a similar thermodynamic single-cylinder test engine. Phenomena of diesel post injection like igniting early post injection or split post injections with short energizing times are considered in this paper.
Journal Article

Thermal Shock Protection for Diesel Particulate Filters

2011-12-15
2011-01-2429
During a thermal regeneration of a Diesel particulate filter (DPF) the temperature inside the DPF may raise above critical thresholds in an uncontrolled way (thermal shock). Especially driving conditions with a comparable low exhaust gas mass flow and high oxygen content like idle speed may create a thermal shock. This paper presents a concept for an ECU software structure to prevent the DPF from reaching improper temperatures and the methodology in order to calibrate this ECU structure. The concept deals in general with a closed-loop control of the exhaust gas air-fuel-ratio during the critical engine operation phases. Those critical operation phases are identified at the engine test bench during “Drop-to-Idle” and “Drop-to-Overrun” experiments. The experiments show that those phases are critical having on the one hand a low exhaust gas mass flow and on the other hand a high oxygen percentage in the exhaust gas.
Technical Paper

Type Analysis of EGR-Strategies for Controlled Auto Ignition (CAI) by Using Numerical Simulations and Optical Measurements

2006-04-03
2006-01-0630
The main assignment of Controlled Auto Ignition (CAI) operation range expansion is to reduce the burn rate or combustion noise at high load and to minimize misfire at low load. The potential of two principal EGR strategies is well known to initiate CAI in a wide range of operation map by using a variable train system: the Exhaust Port Recirculation (EPR) for higher part load and the Combustion Chamber Recirculation (CCR - also called Negative Valve Overlap) for lower part load. However the detailed comparison of the ignition phenomena with each EGR strategy has not been fully studied yet. In this paper, EPR and CCR were compared with same operational condition (engine speed and load). For the analysis, flame luminescence and Raman scattering method for optical measurement and STAR-CD (CD-adapco) for numerical simulation are used.
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