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Technical Paper

1D Model for Correcting the Rate of Injection Signal Based on Geometry and Temperature Influence

2017-03-28
2017-01-0819
The fuel consumption and emissions of diesel engines is strongly influenced by the injection rate pattern, which influences the in-cylinder mixing and combustion process. Knowing the exact injection rate is mandatory for an optimal diesel combustion development. The short injection time of no more than some milliseconds prevents a direct flow rate measurement. However, the injection rate is deduced from the pressure change caused by injecting into a fuel reservoir or pipe. In an ideal case, the pressure increase in a fuel pipe correlates with the flow rate. Unfortunately, real measurement devices show measurement inaccuracies and errors, caused by non-ideal geometrical shapes as well as variable fuel temperature and fuel properties along the measurement pipe. To analyze the thermal effect onto the measurement results, an available rate measurement device is extended with a flexible heating system as well as multiple pressure and temperature sensors.
Technical Paper

50,000 Mile Vehicle Road Test of Three-Way and NOx Reduction Catalyst Systems

1978-02-01
780608
The performance of three way and NOx catalysts was evaluated on vehicles utilizing non-feedback fuel control and electronic feedback fuel control. The vehicles accumulated 80,450 km (50,000 miles) using fuels representing the extremes in hydrogen-carbon ratio available for commercial use. Feedback carburetion compared to non-feedback carburetion improved highway fuel economy by about 0.4 km/l (1 mpg) and reduced deterioration of NOx with mileage accumulation. NOx emissions were higher with the low H/C fuel in the three way catalyst system; feedback reduced the fuel effect on NOx in these cars by improving conversion efficiency with the low H/C fuel. Feedback had no measureable effect on HC and CO catalyst efficiency. Hydrocarbon emissions were lower with the low H/C fuel in all cars. Unleaded gasoline octane improver, MMT, at 0.015g Mn/l (0.06 g/gal) increased tailpipe hydrocarbon emissions by 0.05 g/km (0.08 g/mile).
Technical Paper

A CFD Validation Study for Automotive Aerodynamics

2000-03-06
2000-01-0129
A study was conducted using Ford's nine standard CFD calibration models as described in SAE paper 940323. The models are identical from the B-pillar forward but have different back end configurations. These models were created for the purpose of evaluating the effect of back end geometry variations on aerodynamic lift and drag. Detailed experimental data is available for each model in the form of surface pressure data, surface flow visualization, and wake flow field measurements in addition to aerodynamic lift and drag values. This data is extremely useful in analyzing the accuracy of the numerical simulations. The objective of this study was to determine the capability of a digital physics based commercial CFD code, PowerFLOW ® to accurately simulate the physics of the flow field around the car-like benchmark shapes.
Technical Paper

A Comparison of Four Methods for Determining the Octane Index and K on a Modern Engine with Upstream, Port or Direct Injection

2017-03-28
2017-01-0666
Combustion in modern spark-ignition (SI) engines is increasingly knock-limited with the wide adoption of downsizing and turbocharging technologies. Fuel autoignition conditions are different in these engines compared to the standard Research Octane Number (RON) and Motor Octane Numbers (MON) tests. The Octane Index, OI = RON - K(RON-MON), has been proposed as a means to characterize the actual fuel anti-knock performance in modern engines. The K-factor, by definition equal to 0 and 1 for the RON and MON tests respectively, is intended to characterize the deviation of modern engine operation from these standard octane tests. Accurate knowledge of K is of central importance to the OI model; however, a single method for determining K has not been well accepted in the literature.
Technical Paper

A Computational Investigation of the Effects of Swirl Ratio and Injection Pressure on Mixture Preparation and Wall Heat Transfer in a Light-Duty Diesel Engine

2013-04-08
2013-01-1105
In a recent study, quantitative measurements were presented of in-cylinder spatial distributions of mixture equivalence ratio in a single-cylinder light-duty optical diesel engine, operated with a non-reactive mixture at conditions similar to an early injection low-temperature combustion mode. In the experiments a planar laser-induced fluorescence (PLIF) methodology was used to obtain local mixture equivalence ratio values based on a diesel fuel surrogate (75% n-heptane, 25% iso-octane), with a small fraction of toluene as fluorescing tracer (0.5% by mass). Significant changes in the mixture's structure and composition at the walls were observed due to increased charge motion at high swirl and injection pressure levels. This suggested a non-negligible impact on wall heat transfer and, ultimately, on efficiency and engine-out emissions.
Technical Paper

A Fuel Vapor Model (FVSMOD) for Evaporative Emissions System Design and Analysis

1998-10-19
982644
A fuel vapor system model (FVSMOD) has been developed to simulate vehicle evaporative emission control system behavior. The fuel system components incorporated into the model include the fuel tank and pump, filler cap, liquid supply and return lines, fuel rail, vent valves, vent line, carbon canister and purge line. The system is modeled as a vented system of liquid fuel and vapor in equilibrium, subject to a thermal environment characterized by underhood and underbody temperatures and heat transfer parameters assumed known or determined by calibration with experimental liquid temperature data. The vapor/liquid equilibrium is calculated by simple empirical equations which take into account the weathering of the fuel, while the canister is modeled as a 1-dimensional unsteady absorptive and diffusive bed. Both fuel and canister submodels have been described in previous publications. This paper presents the system equations along with validation against experimental data.
Technical Paper

A Method of Predicting Brake Specific Fuel Consumption Maps

1999-03-01
1999-01-0556
A method of predicting brake specific fuel consumption characteristics from limited specifications of engine design has been investigated. For spark ignition engines operating on homogeneous mixtures, indicated specific fuel consumption based on gross indicated power is related to compression ratio and spark timing relative to optimum values. The influence of burn rate is approximately accounted for by the differences in spark timings required to correctly phase combustion. Data from engines of contemporary design shows that indicated specific fuel consumption can be defined as a generic function of relative spark timing, mixture air/fuel ratio and exhaust gas recirculation rate. The additional information required to generate brake specific performance maps is cylinder volumetric efficiency, rubbing friction, auxiliary loads, and exhaust back pressure characteristics.
Technical Paper

A New Analysis Method for Accurate Accounting of IC Engine Pumping Work and Indicated Work

2004-03-08
2004-01-1262
In order to improve fuel economy, engine manufacturers are investigating various technologies that reduce pumping work in spark ignition engines. Current cylinder pressure analysis methods do not allow valid comparison of pumping work reduction strategies. Existing methods neglect valve timing effects which occur during the expansion and compression strokes, but are actually part of the gas exchange process. These additional pumping work contributions become more significant when evaluating non-standard valve timing concepts. This paper outlines a new analysis method for calculating the pumping work and indicated work of a 4-stroke internal combustion engine. Corrections to PMEP and IMEP are introduced which allow the valid comparison of pumping work and indicated efficiency between engines with different pumping work reduction strategies.
Technical Paper

A Testbed for the Mars Returned Sample Handling Facility

2001-07-09
2001-01-2412
Samples of Mars surface material will return to Earth in 2014. Prior to curation and distribution to the scientific community the returned samples will be isolated in a special facility until their biological safety has been assessed following protocols established by NASA’s Planetary Protection Office. The primary requirements for the pre-release handling of the Martian samples include protecting the samples from the Earth and protecting the Earth from the sample. A testbed will be established to support the design of such a facility and to test the planetary protection protocols. One design option that is being compared to the conventional Biological Safety Level 4 facility is a double walled differential pressure chamber with airlocks and automated equipment for analyzing samples and transferring them from one instrument to another.
Technical Paper

Adaptive Algorithm for Engine Air – Fuel Ratio Control with Dual Fuel Injection Systems

2017-03-28
2017-01-0588
Dual fuel injection systems, like PFI+DI (port fuel injection + direct injection system) are being increasingly used in gasoline engine applications to increase the engine performance, fuel efficiency and reduce emissions. At a given engine operating condition, the air/fuel error is a function of the fraction of fuel injected by each of the fuel systems. If the fraction of fuel from each of the fuel system is changed at a given operating condition, the fuel system error will change as well making it challenging to learn the fuel system errors. This paper aims at describing the adaptive fueling control algorithm to estimate the fuel error contribution from each individual fuel system. Considering the fuel injection system slope errors to be the significant cause for air-fuel errors, a model structure was developed to calculate the fuel system adaptive correction factor as a function of changing fraction of fueling between the fuel systems.
Technical Paper

Adaptive EGR Cooler Pressure Drop Estimation

2008-04-14
2008-01-0624
The pre EGR valve pressure is an important measurement for the Diesel engine air handling system. It is commonly used for the EGR flow calculation during engine transient operation. Due to the erosive exhaust gas, an EGR pressure sensor will eventually have gold corrosion resulting in drive-ability issues. Therefore, a software replacement for the EGR pressure sensor is desirable. However, when the EGR valve is on the cold side of the EGR cooler, the accuracy of the EGR pressure estimation deteriorates because of the variability of the pressure drop across the EGR cooler due to EGR cooler fouling. In this paper, an adaptive scheme is developed to improve the accuracy of pre EGR valve pressure estimation in the presence of EGR cooler fouling for diesel engines. The pressure drop across the EGR cooler is shown to be proportional to the velocity pressure of the EGR flow through the cooler.
Technical Paper

Adaptive Temperature Control for Diesel Particulate Filter Regeneration

2013-04-08
2013-01-0517
The regeneration process of a Diesel Particulate Filter (DPF) consists of an increase in the engine exhaust gas temperature by using post injections and/or exhaust fuel injection during a period of time in order to burn previously trapped soot. The DPF regeneration is usually performed during a real drive cycle, with continuously changing driving conditions. The quantity of post injection/exhaust fuel to use for regeneration is calculated using a combination of an open loop term based on engine speed, load and exhaust gas flow and a closed loop term based on an exhaust gas temperature target and the feedback from a number of sensors. Due to the nature of the system and the slow response of the closed loop term for correcting large deviations, the authority of the fuel calculation is strongly biased to the open loop. However, the open loop fuel calculation might not be accurate enough to provide adequate temperature tracking due to several disturbances in the system.
Technical Paper

Advanced Predictive Diesel Combustion Simulation Using Turbulence Model and Stochastic Reactor Model

2017-03-28
2017-01-0516
Today numerical models are a major part of the diesel engine development. They are applied during several stages of the development process to perform extensive parameter studies and to investigate flow and combustion phenomena in detail. The models are divided by complexity and computational costs since one has to decide what the best choice for the task is. 0D models are suitable for problems with large parameter spaces and multiple operating points, e.g. engine map simulation and parameter sweeps. Therefore, it is necessary to incorporate physical models to improve the predictive capability of these models. This work focuses on turbulence and mixing modeling within a 0D direct injection stochastic reactor model. The model is based on a probability density function approach and incorporates submodels for direct fuel injection, vaporization, heat transfer, turbulent mixing and detailed chemistry.
Journal Article

Advancements and Opportunities for On-Board 700 Bar Compressed Hydrogen Tanks in the Progression Towards the Commercialization of Fuel Cell Vehicles

2017-03-28
2017-01-1183
Fuel cell vehicles are entering the automotive market with significant potential benefits to reduce harmful greenhouse emissions, facilitate energy security, and increase vehicle efficiency while providing customer expected driving range and fill times when compared to conventional vehicles. One of the challenges for successful commercialization of fuel cell vehicles is transitioning the on-board fuel system from liquid gasoline to compressed hydrogen gas. Storing high pressurized hydrogen requires a specialized structural pressure vessel, significantly different in function, size, and construction from a gasoline container. In comparison to a gasoline tank at near ambient pressures, OEMs have aligned to a nominal working pressure of 700 bar for hydrogen tanks in order to achieve the customer expected driving range of 300 miles.
Technical Paper

Air Charge Estimation in Camless Engines

2001-03-05
2001-01-0581
An electromechanically driven valve train offers unprecedented flexibility to optimize engine operation for each speed load point individually. One of the main benefits is the increased fuel economy resulting from unthrottled operation. The absence of a restriction at the entrance of the intake manifold leads to wave propagation in the intake system and makes a direct measurement of air flow with a hot wire air meter unreliable. To deliver the right amount of fuel for a desired air-fuel ratio, we therefore need an open loop estimate of the air flow based on measureable or commanded signals or quantities. This paper investigates various expressions for air charge in camless engines based on quasi-static assumptions for heat transfer and pressure.
Technical Paper

Air Charge and Residual Gas Fraction Estimation for a Spark-Ignition Engine Using In-Cylinder Pressure

2017-03-28
2017-01-0527
An accurate estimation of cycle-by-cycle in-cylinder mass and the composition of the cylinder charge is required for spark-ignition engine transient control strategies to obtain required torque, Air-Fuel-Ratio (AFR) and meet engine pollution regulations. Mass Air Flow (MAF) and Manifold Absolute Pressure (MAP) sensors have been utilized in different control strategies to achieve these targets; however, these sensors have response delay in transients. As an alternative to air flow metering, in-cylinder pressure sensors can be utilized to directly measure cylinder pressure, based on which, the amount of air charge can be estimated without the requirement to model the dynamics of the manifold.
Technical Paper

Air-Fuel Ratio Dependence of Random and Deterministic Cyclic Variability in a Spark-Ignited Engine

1999-10-25
1999-01-3513
One important design goal for spark-ignited engines is to minimize cyclic variability. A small amount of cyclic variability (slow burns) can produce undesirable engine vibrations. A larger amount of cyclic variability (incomplete burns) leads to increased hydrocarbon consumption/emissions. Recent studies have reported deterministic patterns in cyclic variability under extremely lean (misfiring) operating conditions. The present work is directed toward more realistic non-misfiring conditions. Production engine test results suggest that deterministic patterns in cyclic variability are the consequence of incomplete combustion, hence control algorithms based on the occurrence of these patterns are not expected to be of significant practical value.
Technical Paper

Alternative to Phthalate Plasticizer for PVC/NBR Formulation Used in Automotive Fuel System with Biodiesel

2017-03-28
2017-01-0482
Phthalates have been extensively used in rubbers formulation as plasticizer additive for PVC and NBR promoting processing parameters or for cost reduction. The most commonly used plasticizer in PVC compounds was di-2-ethylhexyl phthalate (DEHP) currently not recommend due toxicity. DEHP is listed as prohibited to the Global Automotive Declarable Substance List (GADSL). Phthalates alternatives are already available but the compatibility in automotive fuel system with biodiesel was not extensively understood. This aspect is important since plasticizer may migrate and change rubber properties. Tri-2-ethylhexyl trimellitate (TOTM) and di-2-ethylhexyl terephthalate (DEHT) were selected in this work as alternative additives to a rubber formulation since is not listed to GADSL and have good potential as plasticizer.
Technical Paper

An Adaptive Delay-Compensated PID Air Fuel Ratio Controller

2007-04-16
2007-01-1342
In this work, a discrete,time-based, delay-compensated, adaptive PID control algorithm for air fuel ratio control in an SI engine is presented. The controller operates using feedback from a wide-ranging Universal Exhaust Gas Oxygen (UEGO) sensor situated in the exhaust manifold. Time delay compensation is used to address the difficulties traditionally associated with the relatively long and time-varying time delay in the gas transport process and UEGO sensor response. The delay compensation is performed by computing a correction to the current control move based on the current delay and the corresponding values of the past control moves. The current delay is determined from the measured engine speed and load using a two dimensional map. In order to achieve good servo operation during target changes without compromising regulator performance a two degree of freedom controller design has been developed by adding a pre-filter to the air fuel ratio target.
Technical Paper

An Artificial UEGO Sensor for Engine Cold Start - Methodology, Design, and Performance

2000-03-06
2000-01-0541
The AFR control accuracy in the cold start is crucial to lowering emissions from IC-engine vehicles. An artificial UEGO “sensor” for estimating the real-time AFR during the engine cold start has been developed on the basis of a fuel-perturbation algorithm at Ford Scientific Research Labs. The AFR values calculated by the artificial UEGO sensor have been used in the closed-loop fuel control. Considering that the engine cold start AFR is an uncertain, non-linear problem, some other techniques for optimizing the input stimulation signal and the output-filtering model are integrated together with the fuel perturbation. This artificial sensor was realized and its performance was tested on a Ford vehicle for EPA75 cold 505 test. The assessment of the artificial sensor was quite different in comparison with that of a real UEGO sensor.
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