Search Results

Battery Electric Vehicles and Extended Range Electric Vehicles, like the Chevrolet Volt, can use electrical energy from the Grid to meet the majority of a driver�s transportation needs. This has the positive societal effects of displace petroleum consumption and associated pollutants from combustion on a well to wheels basis, as well as reduced energy costs for the driver. CO2 may also be lower, but this depends upon the nature of the grid energy generation. There is a mix of sources � coal-fired, gas -fired, nuclear or renewables, like hydro, solar, wind or biomass for grid electrical energy. This mix changes by region, and also on the weather and time of day. By monitoring the grid mix and communicating it to drivers (or to their vehicles) in real-time, electrically driven vehicles may be recharged to take advantage of the lowest CO2, and potentially lower cost charging opportunities.

Axial cooling fans are commonly used in electric vehicles to cool batteries with high heating load. One drawback of the cooling fans is the high aeroacoustic noise level resulting from the fan blades and the obstacles facing the airflow. To create a comfortable cabin environment in the vehicle, and to reduce exterior noise emission, a low-noise installation design of the axial fan is required. The purpose of the study is to investigate efficient computational aeroacoustics (CAA) simulation processes to assist the cooling-fan installation design. In this paper we report the current progress of the investigation, where the narrow-band components of the fan noise is focused on. Two methods are used to compute the noise source. In the first method the source is computed from the flow field obtained using the unsteady Reynolds-averaged Navier-Stokes equations (unsteady RANS, or URANS) model.

To characterize the effects of renewable fuels on particulate emissions from GDI engines, engine experiments were conducted using EN228-compliant gasoline fuel blends containing no oxygenates, 10% ethanol (EtOH), or 22% ethyl tert-butyl ether (ETBE). The experiments were conducted in a single cylinder GDI engine using a 6-hole fuel injector operated at 200 bar injection pressure. Both PN in raw exhaust and solid PN (SPN) were measured at two load points and various start of injection (SOI) timings. Raw PN and SPN results were classified into various size ranges, corresponding to current and future legislations. At early SOI timings, where particulate formation is dominated by diffusion flames on the piston due to liquid film, the oxygenated blends yielded dramatically higher PN and SPN emissions than reference gasoline because of fuel effects.

Emissions of nitrogen oxides (NOx) from heavy-duty diesel engines are subject to more stringent environmental legislation. Selective catalytic reduction (SCR) over metal ion-exchanged zeolites is in this connection an efficient method to reduce NOx. Understanding durability of the SCR catalyst is crucial for correct design of the aftertreatment system. In the present paper, thermal and chemical ageing of Fe-BEA as NH3-SCR catalyst is studied. Experimental results of hydrothermal ageing, and chemical ageing due to phosphorous and potassium exposure are presented. The catalyst is characterized by flow reactor experiments, nitrogen physisorption, DRIFTS, XRD, and XPS. Based on the experimental results, a multisite kinetic model is developed to describe the activity of the fresh Fe-BEA catalyst.

The potential of 48V Mild Hybrid is promising in meeting the present and future CO2 legislations. There are various system layouts for 48V hybrid system including P0, P1, P2. In this paper, P2 architecture is used to investigate the effects of water injection benefits in a mild hybrid system. Electrification of the conventional powertrain uses the benefits of an electric drive in the low load-low speed region where the conventional SI engine is least efficient and as the load demand increases the IC Engine is used in its more efficient operating region. Engine downsizing and forced induction trend is popular in the hybrid system architecture. However, the engine efficiency is limited by combustion knocking at higher loads thus ignition retard is used to avoid knocking and fuel enrichment becomes must to operate the engine at MBT (Maximum Brake Torque) timing; in turn neutralizing the benefits of fuel savings by electrification.

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.

This investigation includes a comparison of two Fischer Tropsch (FT) fuels derived from natural gas and a Rapeseed Methyl Ester (RME) fuel with Swedish low sulfur Diesel in terms of emissions levels, fuel consumption and combustion parameters. The engine used in the study was an AVL single cylinder heavy-duty engine, equipped with a cylinder head of a Volvo D12 engine. Two loads (25% and 100%) were investigated at a constant engine speed of 1200 rpm. The engine was calibrated to operate in different levels of EGR and with variable injections timings. A design of experiments was constructed to investigate the effects of these variables, and to identify optimal settings. The results showed that the soot emissions yielded by FT and RME fuels are up to 40 and 80 percent lower than those yielded by the Swedish Diesel. In addition the FT fuel gave slightly lower, and the RME significant higher NOx emissions than the Swedish Diesel.

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.

An idea of reducing the amplitude of higher order harmonic frequencies from PWM switching pattern is presented and analyzed in this paper. For experimental studies a flexi-ble curve shaping circuit was developed and implemented for achieving and controlling smooth transitions in a DC/DC PWM controlled converter for a 12 V system. A comparison between trapezoidal and sinusoidal transitions is made and it is found that a sinusoidal transition gives better EMI performance without increasing the switching losses. In order to further reduce the EMI, a strategy of controlling the output voltage transitions in a MOSFET by “pre-charging” its gate is derived and investigated. The developed practical circuit is tested with sinusoidal reference for a purely resistive load and an R-L load. Frequency responses obtained from simulations and measurements are compared and discussed.

The effect of ammoniac deoxidizing agent (Urea) on the reduction of NOx produced in the Diesel engine was investigated numerically. Urea desolved in water was directly injected into the engine cylinder during the expansion stroke. The NOx deoxidizing process was described using a simplified chemical kinetic model coupled with the comprehensive kinetics of Diesel oil surrogate combustion. If the technology of DWI (Direct Water Injection) with the later injection timing is supposed to be used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NOx are forming. Numerical simulations for the Isotta Fraschini DI Diesel engine are carried out using the KIVA-3V code, modified to account for the “co-fuel” injection and reaction with combustion products. The results showed that the amount of NOx could be substantially reduced up to 80% with the injection timing and the fraction of Urea in the solution optimized.

In order to acquire knowledge about temperature vs. equivalence ratio, T-ϕ, conditions in which emissions are formed and destroyed, T-ϕ parametric maps were constructed for: 1 Soot and soot precursors (C2H2) 2 Nitrogen oxides (NO and NO2) 3 Unburnt intermediates (CH2O, H2 and CO) 4 Important radicals (HO2 and OH) Each map was obtained by plotting data from a large number of simulations for various T-ϕ combinations in a zero-dimensional, 0D, closed Perfectly Stirred Reactor, PSR. Initially, the influences of elapsed reaction time, pressure and EGR level were examined, varying one parameter at a time. Then, since both the elapsed time and pressure change in an engine cycle, the maps were constructed according to engine pressure traces obtained from Computational Fluid Dynamics, CFD, simulations. Since the pressure is changing in elapsed time intervals the maps are called transient.

This paper describes a process membership protocol for distributed real-time systems that use both time-triggered and event-triggered message passing for communication between its processing nodes (ECUs). TTCAN and FlexRay are examples of communication networks that support such systems. The membership protocol supports redundancy management in architectures where distributed applications such as braking, stability control, and collision mitigation share a common set of processing nodes. We assume that each such application consists of several processes executing on different nodes and that each node executes processes belonging to different applications. The protocol allows a group of co-operating processes to establish a consistent view of each other's operational status, i.e. whether they function correctly or not.

In order to meet future emissions legislation for Diesel engines and reduce their CO2 emissions it is necessary to improve diesel combustion by reducing the emissions it generates, while maintaining high efficiency and low fuel consumption. Advanced injection strategies offer possible ways to improve the trade-offs between NOx, PM and fuel consumption. In particular, use of high EGR levels (⥸ 40%) together with multiple injection strategies provides possibilities to reduce both engine-out NOx and soot emissions. Comparisons of optical engine measurements with CFD simulations enable detailed analysis of such combustion concepts. Thus, CFD simulations are important aids to understanding combustion phenomena, but the models used need to be able to model cases with advanced injection strategies.

Optical studies of combusting diesel sprays were done on three different alternative liquid fuels and compared to Swedish environmental class 1 diesel fuel (MK1). The alternative fuels were Rapeseed Oil Methyl Ester (RME), Palm Oil Methyl Ester (PME) and Fischer-Tropsch (FT) fuel. The studies were carried out in the Chalmers High Pressure High Temperature spray rig under conditions similar to those prevailing in a direct-injected diesel engine prior to injection. High speed shadowgraphs were acquired to measure the penetration of the continuous liquid phase, droplets and ligaments, and vapor penetration. Flame temperatures and relative soot concentrations were measured by emission based, line-of-sight, optical methods. A comparison between previous engine tests and spray rig experiments was conducted in order to provide a deeper explanation of the combustion phenomena in the engine tests.

In the study reported here the combustion and emission characteristics of a heavy duty six-cylinder diesel engine fuelled with dimethyl ether (DME) of chemical grade and DME with small and varying amounts of methanol and/or water were experimentally investigated. In addition, the size distribution of emitted particles and selected unregulated emissions were sampled. Methanol and water additions had a very limited effect on emissions, but affected the combustion processes in a way that accentuated the premixed combustion and thus caused more energy to be released early in the cycle. At high load, however, the effect was reversed, due to the lack of distinct premixed combustion. The results confirm that DME combustion does not generate any accumulation mode particles. The particles that are detected are smaller than the soot size range and do not occur in greater numbers than those from a diesel engine in the corresponding size range.

The expansion of current driving cycles for emission regulations to higher load operation in the near future (such as the US06 supplement to the FTP-75 driving cycle) requires attention to low emission combustion concepts in medium to high load regimes. One possibility to reduce NO emissions is to increase the EGR rate. The combustion-temperature reducing effects of high EGR rates can significantly reduce NO formation, to the point where engine-out NOx emissions approach zero levels. However, engine-out soot and CO emissions typically increase at high EGR levels, due to the reduced soot and CO oxidation rates at reduced combustion temperatures and oxygen concentrations. The work presented in this paper focuses on different strategies to reduce soot and CO emissions associated with EGR rates of up to 50%, at which NO formation is largely avoided, but combustion temperatures are not low enough to consider the process as Low-Temperature Combustion (LTC).

The CFD model, based on the LANL KIVA-3 computer code, modified to account for the multi-step dimethyl ether, DME/air, oxidation chemistry, was developed and used to study the neat DME combustion dynamics in a constant volume at Diesel-like conditions and in the Volvo AH10A245DI Diesel engine. Constant volume simulations confirm high ignition quality of neat DME in air. The results of engine modeling illustrate that the injection schedule used for Diesel fuel is not optimal for DME. Surprisingly, the positive gain and peak pressure levels comparable with those for Diesel fuel were obtained using an early (∼ -20 ATDC) injection through a nozzle of a larger diameter at reduced injection pressures and velocities (∼150m/s) preventing too rapid spray atomization. At these conditions, combustion heat release has a specific two-stage character with a peak value placed behind the TDC.

This paper depicts the main topics of the experimental investigation on alcohol engine development field, aiming at the engineering targets for the emission levels. The first part of this study was focused on engine design optimization for running on ethanol mixed with poly-ethylene glycol (PEG) as ignition improver. It was shown that some design changes in compression ratio, turbine casing, injector nozzle configuration and exhaust pressure governor (EPG) activation, lead to a better engine thermodynamics and its thermochemistry. The second objective of this study was the investigation of engine performance and emission levels, when the ignition improver diethyl ether (DEE) would be generated on board via catalytically dehydration of ethanol, and used directly as soluble mixture or separately fumigated.

Mathematical models of a torque sensor equipped crankshaft in a light-duty diesel engine are identified, validated, and compared. The models are based on in-cylinder pressure and crankshaft torque data collected from a 5-cylinder common-rail diesel engine running at multiple operating points. The work is motivated by the need of a crankshaft model in a closed-loop combustion control system based on crankshaft torque measurements. In such a system a crankshaft model is used in order to separate the measured crankshaft torque into cylinder individual torque contributions. A method for this is described and used for IMEP estimation. Not surprisingly, the results indicate that higher order models are able to estimate crankshaft torque more accurately than lower order models, even if the differences are small. For IMEP estimation using the cylinder separation method however, these differences have large effects on accuracy.

DME was tested in a heavy duty diesel engine and in an optically accessible high-temperature and pressure spray chamber in order to investigate and understand the effect of nozzle parameters on emissions, combustion and fuel spray concentration. The engine study clearly showed that smaller nozzle orifices were advantageous from combustion, efficiency and emissions considerations. Heat release analysis and fuel concentration images indicate that smaller orifices result in higher mixing rate between fuel and air due to reductions in the turbulence length scale, which reduce both the magnitude of fuel-rich regions and the steepness of fuel gradients in the spray, which enable more fuel to burn and thereby shorten the combustion duration.