Search Results

1. On page 111, the authors have described a method to assess driver distraction. In this method, participants maintained a white square size on a forward display by using a game gas pedal of like in car-following situation. The size of the white square is determined by calculating the distance to a virtual lead vehicle. The formulas to correct are used to explain variation of acceleration of the virtual lead vehicle. The authors inadvertently incorporated old formulas they had used previously. In the experiments discussed in the article, the corrected formulas were used. Therefore, there is no change in the results. The following from the article:

In this work a detailed model to simulate the transient behavior of catalytic converters is presented. The model is able to predict the unsteady and reacting flows in the exhaust ducts, by solving the system of conservation equations of mass, momentum, energy and transport of reacting chemical species. The en-gine and the intake system have not been included in the simulation, imposing the measured values of mass flow, gas temperature and chemical composition as a boundary condition at the inlet of the exhaust system. A detailed analysis of the diffusion stage triggering is proposed along with simplifications of the physics, finalized to the reduction of the calculation time. Submodels for water condensation and its following evaporation on the monolith surface have been taken into account as well as oxygen storage promoted by ceria oxides.

A thorough understanding of vehicle exhaust aftertreatment system performance requires time-resolved emissions measurements that accurately follow driving transients, and that are correctly time-aligned with exhaust temperature and flow measurements. The transient response of conventional gas analyzers is characterized by both a time delay and an attenuation of high-frequency signal components. The distortion that this imposes on transient emissions measurements causes significant errors in instantaneous calculations of aftertreatment system efficiency, and thus in modal mass analysis. This creates difficulties in mathematical modeling of emissions system performance and in optimization of powertrain control strategies, leading to suboptimal aftertreatment system designs. A mathematical method is presented which improves the response time of emissions measurements. This begins with development of a model of gas transport and mixing within the sampling and measurement system.

The investigation of the flow through the metering section of hydraulic components plays a fundamental role in the design and optimization processes. In this paper the flow through a closed center directional control valve for load -sensing application is studied by means of a multidimensional CFD approach. In the analysis, an open source fluid-dynamics code is used and both cavitation and turbulence are accounted for in the modeling. A cavitation model based on a barotropic equation of state and homogeneous equilibrium assumption, including gas absorption and dissolution in the liquid medium, is adopted and coupled to a two equation turbulence approach. Both direct and inverse flows through the metering section of the control valve are investigated, and the differences in terms of fluid - dynamics behavior are addressed In particular, the discharge coefficient, the recirculating regions, the flow acceleration angle and the pressure and velocity fields are investigated and compared.

Researchers at the Powertrain Control Research Laboratory (PCRL) at the University of Wisconsin-Madison have developed a transient test system for single-cylinder engines that accurately replicates the dynamics of a multi-cylinder engine. The overall system can perform very rapid transients in excess of 10,000 rpm/second, and also replicates the rotational dynamics, intake gas dynamics, and heat transfer dynamics of a multi-cylinder engine. Testing results using this system accurately represent what would be found in the multi-cylinder engine counterpart. Therefore, engine developments can be refined to a much greater degree at lower cost, and these changes directly incorporated in the multi-cylinder engine with minimal modification. More importantly, various standardized emission tests such as the cold-start, FTP or ETC, can be run on this single-cylinder engine.

The study measured Mass Air Flow, (MAF), Manifold Absolute Pressure, (MAP), and emissions of NO and soot during fourteen transients of speed and load, representative of the Extra Urban Drive Cycle (EUDC). The tests were conducted on a typical passenger car/light-duty truck powertrain (a turbocharged common-rail diesel engine, of in-line 4-cylinder configuration). The objective was to compare NO and soot with corresponding steady-state emission results and propose an engine measurement methodology that will potentially quantify deviation (i.e. deterioration with respect to steady state optimum) in emissions of NO and soot during transients. Comparison between steady state, quasi-steady-states (defined later in the paper) and transients indicated that discrete quasi-steady-state engine operation, can be used for accurate prediction of transient emissions of NO and soot.

An experimental study was performed to develop a more fundamental understanding of the effects of secondary air injection (SAI) on exhaust gas emissions and catalyst light-off characteristics during cold start of a modern SI engine. The effects of engine operating parameters and various secondary air injection strategies such as spark retardation, fuel enrichment, secondary air injection location and air flow rate were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAI. Time-resolved HC, CO and CO₂ concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to time-resolved mass emissions by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAI.

Existing gasoline DI injection equipment has been modified to generate single hole pulsed gas jets. Injection experiments have been performed at combinations of 3 different pressure ratios (2 of which supercritical) respectively 3 different hole geometries (i.e. length to diameter ratios). Injection was into a pressure chamber with optical access. Injection pressures and injector hole geometry were selected to be representative of current and near-future DI natural gas engines. Each injector hole design has been characterized by measuring its discharge coefficient for different Re-levels. Transient jets produced by these injectors have been visualized using planar laser sheet Mie scattering (PLMS). For this the injected gas was seeded with small oil droplets. The corresponding flow field was measured using particle image velocimetry (PIV) laser diagnostics.

This paper demonstrates that the implementation of Flash Gas Bypass method can improve the performance of conventional direct expansion R134a mobile air-conditioning system with a microchannel evaporator. This method uses flash gas tank after expansion valve to separate and bypass flash refrigerant vapor around the evaporator, and feed the evaporator with only liquid refrigerant. Pressure drop is reduced and refrigerant distribution is significantly improved, resulting in higher evaporator effectiveness and evaporation pressure. Both lower pressure drop and lifted evaporation pressure allows the compressor to work with lower pressure ratio, saving required compressor work. An experimental comparison of the direct expansion system shows that Flash Gas Bypass method increases the cooling capacity and COP at the same time by up to 16% and 11%, respectively.

Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion has been studied widely in the past decade. However, in HCCI engines using negative valve overlap (NVO), there is still uncertainty as to whether the effect of pilot injection during NVO on the start of combustion is primarily due to heat release of the pilot fuel during NVO or whether it is due to pilot fuel reformation. This paper presents data taken on a 4-cylinder gasoline direct injection, spark ignition/HCCI engine with a dual cam system, capable of recompressing residual gas. Engine in-cylinder samples are extracted at various points during the engine cycle through a high-speed sampling system and directly analysed with a gas chromatograph and flame ionisation detector. Engine parameter sweeps are performed for different pilot injection timings and quantities at a medium load point.

This study was conducted to investigate the influence of low-temperature reactions on the Homogeneous Charge Compression Ignition (HCCI) combustion process. Specifically, an investigation was made of the effect of the residual gas condition on low-temperature reactions, autoignition and the subsequent state of combustion following ignition. Light emission and absorption spectroscopic measurements were made in the combustion chamber in order to investigate low-temperature reactions in detail. In addition, chemical kinetic simulations were performed to validate the experimental results and to analyze the elemental reaction process. The results made clear the formation behavior of the chemical species produced during low-temperature HCCI reactions.

Real gas effects are studied during the compression stroke of a diesel engine. Several different real gas models are compared to the ideal gas law and to the experimental pressure history. Comparisons are done with both 1-D and CFD simulations, and reasons and answers are found out for the observed differences between simulations and experimental data. The engine compression ratio was measured for accurate model predictions. In addition, a 300bar extreme pressure case is also analyzed with the real gas model since an engine capable for this performance level is currently being built at the Aalto University School of Science and Technology. Real gas effects are even more important in these extreme conditions than in normal operating pressures. Finally, it is shown that the predicted pressure history during an engine compression stroke by a real gas model is more accurately predicted than by the ideal gas law.

This paper deals with experimental study of in-cylinder tumble flows in a single-cylinder, four-stroke, two-valve internal combustion engine using a pentroof-offset-bowl piston under non-reacting conditions with four intake manifold orientations at an engine speed of 1000 rev/min., during suction and compression strokes using particle image velocimetry. Two-dimensional in-cylinder tumble flow measurements and analysis are carried out in combustion space on a vertical plane passing through cylinder axis. Ensemble average velocity vectors are used to analyze the tumble flows. Tumble ratio (TR) and average turbulent kinetic energy (TKE) are evaluated and used to characterize the tumble flows. From analysis of results, it is found that at end of compression stroke, 90° intake manifold orientation shows an improvement in TR and TKE compared other intake manifold orientations considered.

Mechanisms of NH₃ generation using LNT-like catalysts have been studied in a bench reactor over a wide range of temperatures, flow rates, reformer catalyst types and synthetic exhaust-gas compositions. The experiments showed that the on board production of sufficient quantities of ammonia on board for SCR operation appeared feasible, and the results identified the range of conditions for the efficient generation of ammonia. In addition, the effects of reformer catalysts using the water-gas-shift reaction as an in-situ source of the required hydrogen for the reactions are also illustrated. Computations of the NH₃ and NOx kinetics have also been carried out and are presented. Design and impregnation of the SCR catalyst in proximity to the ammonia source is the next logical step. A heated synthetic-exhaust gas flow bench was used for the experiments under carefully controlled simulated exhaust compositions.

Fuel injection during negative valve overlap offers a promising method of controlling HCCI combustion, but sorting out the thermal and chemical effects of NVO fueling requires knowledge of temperatures throughout the cycle. Computing bulk temperatures throughout closed portions of the cycle is relatively straightforward using an equation of state, once a temperature at one crank angle is established. Unfortunately, computing charge temperatures at intake valve closing for NVO operation is complicated by a large, unknown fraction of residual gases at unknown temperature. To address the problem, we model blowdown and recompression during exhaust valve opening and closing events, allowing us to estimate in-cylinder charge temperatures based on exhaust-port measurements. This algorithm permits subsequent calculation of crank-angle-resolved bulk temperatures and residual gas fraction over a wide range of NVO operation.

This paper examines the interaction of bulk flow and jet-induced fuel convection in an optically accessible hydrogen-fueled engine with direct injection. Planar laser-induced fluorescence (PLIF) of gaseous acetone as a fuel tracer was performed to obtain quantitative images of the hydrogen mole-fraction in the operating engine. With the engine motored, fuel was injected into inert bulk gas from a centrally located injector during the compression stroke. The injector had a single-hole nozzle with the jet angled at 50 degrees with respect to the vertical injector axis. Two parameters were varied in the experiments, injector orientation and tumble intensity, and for each of these, the injection timing was varied. Image series of the mean fuel mole-fraction between injection and near-TDC crank angles capture the mixture-formation process for each configuration and injection timing.

In this study an attempt to understand and demonstrate the effects of various washcoat technologies under active and passive regeneration conditions was performed. Six different formulations, on 1.0" D. x 3.0" L. SiC wall flow filters at the laboratory level were used at various test conditions, including variable NO₂/NO ratios and O₂ concentrations. Samples were regenerated using active and passive conditions to evaluate regeneration rates and the potential impact of regeneration at the vehicle level. Results were applied to vehicle operating conditions to determine passive functionality and potential benefits. Active regenerations at 2% O₂ and 5% O₂ showed no significant difference in time to complete regeneration and soot burn rates. Active regenerations performed at 1% O₂ and 5% O₂ concentration showed that the regeneration temperature was shifted by approximately 50°C.

Diesel engines with relatively good fuel economy are known as an effective means of reducing CO₂ emissions. It is expected that diesel engines will continue to expand as efforts to slow global warming are intensified. Diesel particulate and NOx reduction system (DPNR), which was first developed in 2003 for introduction in the Japanese and European markets, shows high purification performance which can meet more stringent regulations in the future. However, it is poisoned by sulfur components in exhaust gas derived from fuel and lubricant. We then developed the sulfur trap DPNR with a sulfur trap catalyst that traps sulfur components in the exhaust gas. High purification performance could be achieved with a small amount of platinum group metal (PGM) due to prevention of sulfur poisoning and thermal deterioration.

Using a 1D simulation that transforms the 3D shape of intake-exhaust systems into one dimension and calculates the thermodynamics and fluid gas dynamics of internal combustion engines, a prediction technology of the output power and intake-exhaust noise for small- displacement single-cylinder motorcycles was established. Output power can be calculated accurately for various engines with different displacements and cooling systems by adjusting the boundary conditions in the calculation model. The intake-exhaust noise can be calculated accurately by clarifying some important points for accuracy when transforming the 3D shapes of the intake-exhaust system into the 1D model and by reflecting them in the calculation model. As for mufflers that have complicated internal structures, the calculation of exhaust-noise cannot be made with sufficient accuracy because 1D simulation does not calculate spatial flow behavior. But, improvement of accuracy is expected using a 1D-3D coupled simulation.

Fouling phenomenon is a key issue for EGR cooler operation. In spite of the fact that soot deposition is imposed by the characteristics of the exhaust gases flow, the design of the EGR cooler has a significant impact for effect on the engine. New combustion modes corresponding to new engine developments and combination of EGR system with other post-treatment devices make that fouling conditions for future generations of EGR coolers can be significantly different from previous applications from Euro 3 to Euro 5. An investigation has been performed in order to characterize the response of different EGR coolers designs for different conditions of the exhaust gases. As for the design, the technology selected has been tube-and-fin heat exchanger, which is a high performance technology that fits Euro 6 customer specifications. The variations in design have been made through modifications in fin characteristics, both in configuration and geometric dimensions.