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Technical Paper

Modeling Coupled Processes of CO and Soot Formation and Oxidation for Conventional and HCCI Diesel Combustion

2007-04-16
2007-01-0162
The study of soot oxidation and CO formation in internal combustion engine applications is the subject of numerous recent investigations. Their modeling is particularly important for Diesel operating conditions. Models have been developed recently at IFP to account for the complicated kinetic processes involved in CO / soot production and oxidation. This paper presents the equations for CO formation and oxidation based on a reduced 6 step chemistry model coupled with the PSK reduced soot production and oxidation mechanism. The species are accounted for in the conservation equations. Model development is done on the framework of the ECFM3Z engine combustion model. The global CO/soot model is first validated in a constant volume high pressure cell against LII measurements. Model parameters are adjusted and kept constant for the remaining of the simulations. Then, engine simulations are used to validate the model behavior in conventional and HCCI Diesel conditions.
Technical Paper

Effects of Average Driving Cycle Speed on Lean-Burn Natural Gas Bus Emissions and Fuel Economy

2007-01-23
2007-01-0054
Although diesel engines still power most of the heavy-duty transit buses in the United States, many major cities are also operating fleets where a significant percentage of buses is powered by lean-burn natural gas engines. Emissions from these buses are often expressed in distance-specific units of grams per mile (g/mile) or grams per kilometer (g/km), but the driving cycle or route employed during emissions measurement has a strong influence on the reported results. A driving cycle that demands less energy per unit distance than others results in higher fuel economy and lower distance-specific oxides of nitrogen emissions. In addition to energy per unit distance, the degree to which the driving cycle is transient in nature can also affect emissions.
Technical Paper

EGR and Intake Boost for Managing HCCI Low-Temperature Heat Release over Wide Ranges of Engine Speed

2007-01-23
2007-01-0051
Reaching for higher loads and improving combustion-phasing control are important challenges for HCCI research. Although HCCI engines can operate with a variety of fuels, recent research has shown that fuels with two-stage autoignition have some significant advantages for overcoming these challenges. Because the amount of low-temperature heat release (LTHR) is proportional to the local equivalence ratio (ϕ), fuel stratification can be used to adjust the combustion phasing (CA50) and/or burn duration using various fuel-injection strategies. Two-stage ignition fuels also allow stable combustion even for extensive combustion-phasing retard, which reduces the knocking propensity. Finally, the LTHR reduces the required intake temperature, which increases the inducted charge mass for a given intake pressure, allowing higher fueling rates before knocking and NOx emissions become a problem. However, the amount of LTHR is normally highly dependent on the engine speed.
Technical Paper

Catalyzed Particulate Filters for Mobile Diesel Applications

2007-01-23
2007-01-0041
Catalyst coated silicon carbide filters were developed and applied for light-duty and heavy-duty diesel applications. This catalyst coating is suitable also for industrial applications and to be used on cordierite or sintered metal filters. Development activities yield solgel type coating for particulate filters with properties allowing very thin coating, containing metal oxides interacting with active sites, e.g. precious metals (Pt, Pd). A tailored catalyst composition was developed for the catalytic activity and durability in oxidation and soot regeneration reactions. The combination of thermal and catalytic particulate oxidation by oxygen and NO2 was investigated using different regeneration strategies in engine exhaust and laboratory conditions. The passive regeneration by NO2 initiated around 310°C with CPF only. One of the main targets was to lengthen the intervals between active regeneration phases by catalyzed particulate filters which enhance passive regeneration properties.
Technical Paper

Modeling of the Catalyzed Continuously Regenerating Diesel Particulate Filter (CCR-DPF) System: Model Development and Passive Regeneration Studies

2007-01-23
2007-01-0043
Particulate Matter (PM) emissions are of increasing importance, as diesel emissions legislation continues to tighten around the world. Diesel PM can be controlled using Diesel Particulate Filters (DPFs), which can effectively reduce the level of carbon (soot) emissions to ambient background levels. The Johnson Matthey Continuously Regenerating Trap (CRT®) [1], which will be referred to as the Continuously Regenerating DPF (CR-DPF) for the remainder of this paper, has been widely applied in Heavy Duty Diesel (HDD) applications, and has been proved to have outstanding field durability [2]. To widen the potential application of this system, addition of a platinum based catalyst to the DPF has been shown to lead to a higher PM removal rate under passive regeneration conditions, using the NOx contained in the exhaust gases.
Technical Paper

Advanced Diesel Particulate Filter Design for Lifetime Pressure Drop Solution in Light Duty Applications

2007-01-23
2007-01-0042
Highly efficient wall-flow diesel particulate filters (DPF) are the primary means of PM emissions control in light-duty diesel vehicles. The successful commercialization of DPF technology has allowed combining attractive characteristics (good fuel economy, high low-end torque characteristics) of a diesel engine with significant PM emissions reductions to meet the stringent legislation. The design for advanced filter systems is driven by the lifetime pressure drop requirements with the accumulation of non-combustible materials (ashes) over time in the filter. More compact filter designs can be achieved by using filters with the proprietary Asymmetric Cell Technology (ACT) providing a larger inlet channel volume and therefore a higher ash storage capacity in the same space envelope without compromising the filter bulk heat capacity and mechanical integrity.
Technical Paper

Challenges for the Future Diesel Engines Exhaust Gas Aftertreatment System

2007-01-23
2007-01-0040
The reduction of diesel emissions will remain a major challenge in the near future. Based on the expected emissions legislation for Europe and NAFTA, respectively, two main routes to approach this challenge are possible. Especially for the NAFTA market the use of a NOx emission control system is highly probable due to the established low limit for NOx emissions. From today's point of view only two systems - the NOx storage catalyst and the SCR catalyst system - have the potential to reach these limits. In Europe the expected Euro5 NOx limit can most likely be reached by engine measures only. Nevertheless both markets have the common understanding that besides the further improvement by internal engine measures the diesel oxidation catalyst (DOC) as well as the catalysed diesel particulate (DPF) filter will play an essential role in diesel emissions reduction.
Technical Paper

Comparative Study of Natural Gas Vehicles Commercial Catalysts in Monolithic Form

2007-01-23
2007-01-0039
With growing concern about air quality and increase of city population is renewed interest in transportation sector. The challenge for governments is to find and develop cost-effective ways to improve urban air quality without scarifying economy. Natural gas as vehicle fuel can reduce compared to conventional Diesel technology, particulate matter by as much as 99%, nitrous oxides (NOx) by as much as 85%, and carbon monoxide (CO) by more than 90%. Relative to gasoline, the global warming impact (GWI) for dedicated natural gas vehicles (NGVs) is generally more than 20 % lower. When non-regulated emissions are included on a well-to-wheel basis, NGVs still show advantages over gasoline and Diesel vehicles. Nowadays, there are more than 4.7 million NGVs in operation all around the world. It seems that the catalysts used in NGVs are close to Three-Way Catalysts (TWC) typically used for gasoline engines. However, there are very few studies about the impact of catalysis for NGVs.
Technical Paper

Evaluation of Medium Duty DME Truck Performance -Field Test Results and PM Characteristics-

2007-01-23
2007-01-0032
The performance of a medium duty DME truck was evaluated by field tests and engine bench tests. The DME vehicle was given a public license plate on October 2004, after which running tests were continued on public roads and a test course. The DME vehicle could run the whole distance, about 500 km, without refueling. The average diesel equivalent fuel consumption of the fully loaded DME truck was 5.75 km/l, running at 80 km/h on public highways. Remedying several malfunctions that occurred in the power-train subsystems enhanced the vehicle performance and operation. The DME vehicle accumulated 13,000 km as of August, 2006 with no observed durability trouble of the fuel injection pump. Disassembly and inspection of the fuel injectors after 7,700 km operation revealed a few differences in the nozzle tip and the needle compared to diesel fuel operation. However, the injectors were used again after cleanup.
Technical Paper

An Experimental Investigation of Fischer-Tropsch Fuels in a Light-Duty Diesel Engine

2007-01-23
2007-01-0030
Experiments were performed using a Light-Duty, single-cylinder, research engine in which the emissions, fuel consumption and combustion characteristics of two Fischer-Tropsch (F-T) Diesel fuels derived from natural gas and two conventional Diesel fuels (Swedish low sulfur Diesel and European EN 590 Diesel) were compared. Due to their low aromatic contents combustion with the F-T Diesel fuels resulted in lower soot emissions than combustion with the conventional Diesel fuels. The hydrocarbon emissions were also significantly lower with F-T fuel combustion. Moreover the F-T fuels tended to yield lower CO emissions than the conventional Diesel fuels. The low emissions from the F-T Diesel fuels, and the potential for producing such fuels from biomass, are powerful reason for future interest and research in this field.
Technical Paper

Investigation of the Combustion Characteristics of GTL Diesel Fuel in a Constant Volume Combustion Chamber

2007-01-23
2007-01-0031
The results of an optical investigation into the combustion characteristics of GTL (Gas-To-Liquids) diesel fuel are presented. The investigation was carried out using a high pressure, constant volume combustion chamber with optical access, fitted with a modern diesel injection system. Combustion images were captured under conditions which simulate those present in a diesel engine. A low sulphur diesel fuel meeting the European EN590 specification was used as a reference. Image capture and subsequent analysis was performed by means of an AVL Visioscope system which used the two-colour method to yield quantitative information regarding flame temperature and soot concentration. Conditions in the combustion chamber are preset by combusting a pre-charge to generate the necessary pressure, temperature, and residual gas fraction. This allowed the effect of varying oxygen concentration at the start of diesel combustion to be investigated.
Technical Paper

HSDI Diesel Engine Optimisation for GTL Diesel Fuel

2007-01-23
2007-01-0027
A Mercedes E320 CDI vehicle has been modified for more optimal operation on Gas-To-Liquids (GTL) diesel fuel, in order to demonstrate the extent of exhaust emission reductions which are enabled by the properties of this fuel. The engine hardware changes employed comprised the fitment of re-specified fuel injectors and the reduction of the compression ratio from 18:1 to 15:1, as well as a re-optimisation of the software calibration. The demonstration vehicle has achieved a NOx emission of less that 0.08 g/km in the NEDC test cycle, while all other regulated emissions still meet the Euro 4 limits, as well as those currently proposed for Euro 5. CO2 emissions and fuel consumption, were not degraded with the optimised engine. This was achieved whilst employing only cost-neutral engine modifications, and with the standard vehicle exhaust system (oxidation catalyst and diesel particulate filter) fitted.
Technical Paper

A Study of PM Emission Characteristics of Diesel Vehicle Fueled with GTL

2007-01-23
2007-01-0028
In this study, diesel exhaust emission characteristics were investigated as GTL (Gas To Liquid) fuel was applied to a heavy-duty diesel truck which had been developed to match a Japanese new long-term exhaust emission regulation (NOx < 2.0 g/kWh, PM < 0.027 g/kWh). The results in this study show that although the test vehicle has advanced technologies (e.g. high pressure fuel injection, oxidation catalyst, and urea-SCR aftertreatment system, etc.) which are applied to reduce diesel emissions, the neat GTL fuel has a great advantage to reduce particulate matter emissions and poly aromatic hydrocarbons. And regarding nano-size PM emissions, nuclei mode particles emitted during idling are significantly decreased by using the GTL fuel.
Technical Paper

A Diesel Engine Real time NOx Emission Simulation System Based on RTW and VxWorks

2007-01-23
2007-01-0025
Lower engine emission is an important target in the evaluation of the control strategy of ECU. So the hardware in the loop simulation system (HILSS) including emission model is necessary. In this paper, a NOx emission neural network (NN) model is constructed based on the reflection relationship between the NOx formation and some direct influence factors such as concentration of oxygen, combustion temperature, combustion period. Combined with a nonlinear dynamic diesel engine model based on the filling and emptying methods, the NOx emission NN model can reach the trade-off between simulation accuracy and computational overhead. A new HILS platform based on Matlab/RTW and VxWorks real time operating system is introduced in the paper. The graphic programming and automatic code generating methods also developed to accelerate the development of HILSS.
Technical Paper

Exterior Water Management Using a Custom Euler-Lagrange Simulation Approach

2007-04-16
2007-01-0101
The reduction of hardware vehicle models during development drives the necessity to transfer most hardware tests to VR Simulation. Exterior water management is one of the topics, where complex physics meet everyday situations. A vehicle contamination test conducted in a wind tunnel is selected to be transferred to numerical simulation. The method of choice is the Euler-Lagrange approach with modeled ‘liquid’ wall particles. A new wall film model has been developed in the present study to include the observed liquid properties in physical test. This model takes the local wetting conditions into account and constitutes a reformulation of the local force balance of the wall liquid. Also the wall film separation model has been refined and improved. With this new approach, the gas/liquid, liquid/solid and liquid/liquid interaction has been remodeled.
Technical Paper

Impact of Diesel/Biodiesel Blends on Emissions from a Diesel Vehicle Operated in Real Driving Conditions

2007-01-23
2007-01-0076
In this study exhaust emissions from a commercially available motor vehicle with neat diesel fuel and diesel/biodiesel blends have been investigated. The vehicle was a EURO IV class with a turbocharged direct injection engine (TDI) of 2.0 liter displacement. Methyl ester obtained from used frying oil was as the blendstock at proportions of 5, 20, and 50 % by volume. On-board emission measurements were conducted in real-world driving on a specific driving route infrastructure including altitude differentiation, humps, and various alternations on driving conditions, such as frequent accelerations and decelerations. The addition of biodiesel demonstrated a decrease in NOx, CO and smoke opacity emissions. CO2 emissions and fuel consumption showed an increase
Technical Paper

NOx Emissions Reduction in a Biodiesel Engine by Means of EGR Technology

2007-01-23
2007-01-0078
Biodiesel-fuelled engines produce less carbon monoxide, unburned hydrocarbon, and particulate emissions compared to conventional diesel fuel but higher NOx emissions - the greatest threat to the ozone layer. This behaviour is attributed to the higher content of oxygen of the biodiesel. A recognized technique for attaining lower NOx emission levels on Diesel engines is the exhaust gas recirculation (EGR). In order to evaluate if this technique is also valid for biodiesel blends, a review is made concerning the effect of EGR on emissions of diesel engines (one and two cylinders) running with different biodiesel blends and for different EGR rates. Data about conventional diesel are also shown for comparison purposes. Similar results were found in both cases (one and two cylinders) and conclusion can be drawn that NOx emissions decrease with the increasing of EGR rate. The degree of reduction in NOx at higher loads is also higher.
Technical Paper

Study of Emission and Combustion Characteristics of RME B100 Biodiesel from a Heavy Duty DI Diesel Engine

2007-01-23
2007-01-0074
A rapeseed methyl ester biodiesel RMEB100 was tested on a heavy duty DI diesel engine under steady state conditions. The combustion performance and exhaust emissions were measured and compared to a standard petroleum derived diesel fuel. The engine used was a 6 cylinder, turbocharged, intercooled Perkins Phaser Engine, with emission compliance of EURO 2, fitted with an oxidation catalyst. The exhaust samples were taken both upstream and downstream of the catalyst. Particulates were collected and analysed for VOF, carbon and ash. A MEXA7100 gas analysis system was used for legislated gas analysis such as CO, CO2, NOx and total hydrocarbons. A FTIR analysis system was deployed for gaseous hydrocarbon speciation, which is capable of speciating up to 65 species. The results showed a significant reduction in total particulate mass, particulate VOF, CO, THC and aldehydes when using RMEB100.
Technical Paper

A Study of Quantitative Impact on Emissions of High Proportion RME-Based Biodiesel Blends

2007-01-23
2007-01-0072
Previous work of the authors' group has shown that biodiesel fuels as a replacement for conventional diesel fuel in engine combustion can reduce PM level dramatically while lowering some other regulated emissions as well. It has shown that these fuels have the potential to increase the overall engine performance due to their lower sulphur and/or aromatics content compared with standard diesel fuels. This paper presents a study on a single cylinder naturally aspirated direct injection (DI) diesel engine, equipped with a pump-line-nozzle injection system, operating with varied biodiesel fuel blends (0%, 25%, and 50% of RME by volume) with ultra low sulphur diesel fuel (ULSD). The detailed analysis of the measurement data shows that the ignition delay and exhaust emissions are affected by the proportion of biodiesel due to the effect of different physical and chemical properties of the two fuels.
Technical Paper

Regulated and Unregulated Emissions Characteristics of a Diesel Vehicle Operating with Diesel/Biodiesel Blends

2007-01-23
2007-01-0071
In the present investigation, tests were carried out to evaluate exhaust emissions of a turbocharged indirect injection diesel engine fuelled with diesel - biodiesel blends. The vehicle was Euro III compliant, fuelled with a typical diesel fuel and used frying oil methyl ester blends at proportions of 2, 5, 10, and 20% respectively. Based on the New European Driving Cycle (NEDC), regulatred and unregulated exhaust emissions were determined over a chassis dynamometer. The use of biodiesel resulted into a significant decrease of HC emissions. NOx and CO emissions exhibited a decreasing trend with the addition of the biodiesel. On the contrary, higher levels of PM emissions were observed. For carbonyl compounds, emissions of acetaldehyde were significantly increased with formaldehyde showing a slight increasing trend.
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