Search Results

Two oxygenated fuels were evaluated on a single-cylinder diesel engine and compared to three hydrocarbon diesel fuels. The oxygenated fuels included canola biodiesel (canola methyl esters, CME) and CME blended with dibutyl succinate (DBS), both of which are or have the potential to be bio-derived. DBS was added to improve the cold flow properties, but also reduced the cetane number and net heating value of the resulting blend. A 60-40 blend of the two (60% vol CME and 40% vol DBS) provided desirable cold flow benefits while staying above the U.S. minimum cetane number requirement. Contrary to prior vehicle test results and numerous literature reports, single-cylinder engine testing of both CME and the 60-40 blend showed no statistically discernable change in NOx emissions relative to diesel fuel, but only when constant intake oxygen was maintained.

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.

With concerns over increasing worldwide demand for gasoline and greenhouse gases, many automotive companies are increasing their product lineup of vehicles to include flex-fuel vehicles that are capable of operating on fuel blends ranging from 100% gasoline up to a blend of 15% gasoline/85% ethanol (E85). For the purpose of this paper, data was obtained that will enable an evaluation relating to the effect the use of E85 fuel has on exhaust system surface temperatures compared to that of regular unleaded gasoline while the vehicle undergoes a typical drive cycle. Three vehicles from three different automotive manufacturers were tested. The surface of the exhaust systems was instrumented with thermocouples at specific locations to monitor temperatures from the manifold to the catalytic converter outlet. The exhaust system surface temperatures were recorded during an operation cycle that included steady vehicle speed operation; cold start and idle and wide open throttle conditions.

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.

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.

There is keen interest in understanding the origins of engine-out unburned hydrocarbons emitted during SI engine cold start. This is especially true for the first few firing cycles, which can contribute disproportionately to the total emissions measured over standard drive cycles such as the US Federal Test Procedure (FTP). This study reports on the development of a novel methodology for capturing and quantifying unburned hydrocarbon emissions (HC), CO, and CO2 on a cycle-by-cycle basis during an engine cold start. The method was demonstrated by applying it to a 4 cylinder 2 liter GTDI (Gasoline Turbocharged Direct Injection) engine for cold start conditions at an ambient temperature of 22°C. For this technique, the entirety of the engine exhaust gas was captured for a predetermined number of firing cycles.

Instrumentation of an exhaust system to measure surface temperature at multiple locations usually involves welding independent thermocouples to the surface of the system. This report describes a new type of thermocouple fabricated to measure temperature at a point or temperature difference between points on a metallic object utilizing the metal as one component of the new thermocouple. AISI 316 stainless steel is used in the current study to represent automotive exhaust pipe. The other component of the thermocouple is Nickel-Chromium (Chromel, Chromega), one of the two metals used in type K thermocouples, which are generally used for exhaust temperature measurements during emission tests. Use of the new thermocouple is contingent upon an accurate calibration of its response to changes in temperature.

The aldehyde emissions of 1.6L and 5.0L flexible fuel vehicles (FFV) have been measured, with and without a catalyst, on a range of fuels. The “zero mile” catalyzed emission levels of formaldehyde when operating on M85 (85% methanol and 15% gasoline) are in the 5-15 mg/mi range, but as mileage accumulates they tend to be in the 30-50 mg/mi range. The feedgas levels are high and appear to correlate with engine displacement. The formaldehyde and methanol emissions are higher when operating on M100, compared to M85, but the non-oxygenated hydrocarbon emissions are about the same for both fuels, which suggests that the use of M85 may actually provide more air quality benefit than M100. High mileage control of aldehydes to the level of gasoline vehicles does not appear possible with current technology.

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.

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.

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.

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.

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.

In a continuing effort to include real-world emissions in regulatory testing, the USEPA has included air conditioning operation as part of the Supplemental Federal Test Procedure (SFTP). Known as the SC03, these tests require automobile manufacturers to construct and maintain expensive environmental chambers. However, the regulations make allowances for a simulation test, if one can be shown to demonstrate correlation with the SFTP results. We present the results from an experiment on a 1998 Ford sedan, which simulates the heat load of a full environmental chamber. Moreover, the test procedure is simpler and more cost effective. The process essentially involves heating the condenser of the air conditioning system by using the heat of the engine, rather than heating the entire vehicle. The results indicate that if the head pressure is used as a feedback signal to the radiator fan, the load generated by a full environmental chamber can be duplicated.

The equipment for collecting dilute exhaust samples involves the use of bag materials (i.e., Tedlar®) that emit hydrocarbons that contaminate samples. This study identifies a list of materials and treatments to produce bags that reduce contamination. Based on the average emission rates, baked Tedlar®, Capran® treated with alumina deposition, supercritical CO2 extracted Kynar® and supercritical CO2 extracted Teflon NXT are capable of achieving the target hydrocarbon emission rate of less than 15 ppbC per 30 minutes. CO2 permeation tests were also performed. Tedlar, Capran, Kynar and Teflon NXT showed comparable average permeation rates. Based on the criteria of HC emission performance, changes in measured CO2 concentration, ease of sealing, and ease of surface treatment, none of the four materials could be distinguished from one another.

A 22 hour engine test was developed to evaluate the effects of fuels, lubricants, and valvetrain dynamics on the wear of OHC 2.3L engine camshafts and finger followers. Procedures include a break-in to improve test repeatability and a test sequence to allow single-shift operation. A surface analyzer capable of measuring cam lobe wear profiles to micro-inch accuracy provided a quantitative wear comparison. A pure mineral oil, as expected, resulted in higher camshaft wear than using a fully formulated SF lubricant. Cam and follower wear increased significantly when ethanol replaced gasoline as fuel. The combination of ethanol, mineral oil and heavy duty valve springs was selected to increase test severity for hardware discrimination. The average wear of the intake lobes was greater than the exhausts. Kinematic analysis and visual inspection of the valve train mechanism revealed differences in the relative motion and contact stress pattern.

This paper provides an overview of the effects of blending ethanol with gasoline for use in spark ignition engines. The overview is written from the perspective of considering a future ethanol-gasoline blend for use in vehicles that have been designed to accommodate such a fuel. Therefore discussion of the effects of ethanol-gasoline blends on older legacy vehicles is not included. As background, highlights of future emissions regulations are discussed. The effects on fuel properties of blending ethanol and gasoline are described. The substantial increase in knock resistance and full load performance associated with the addition of ethanol to gasoline is illustrated with example data. Aspects of fuel efficiency enabled by increased ethanol content are reviewed, including downsizing and downspeeding opportunities, increased compression ratio, fundamental effects associated with ethanol combustion, and reduced enrichment requirement at high speed/high load conditions.

Low Temperature Combustion (LTC) engines are promising to improve powertrain fuel economy and reduce NOx and soot emissions by improving the in-cylinder combustion process. However, the narrow operating range of LTC engines limits the use of these engines in conventional powertrains. The engine’s limited operating range can be improved by taking advantage of electrification in the powertrain. In this study, a multi-mode LTC-SI engine is integrated with a parallel hybrid electric configuration, where the engine operation modes include Homogeneous Charge Compression Ignition (HCCI), Reactivity Controlled Compression Ignition (RCCI), and conventional Spark Ignition (SI). The powertrain controller is designed to enable switching among different modes, with minimum fuel penalty for transient engine operations.

A normalized analytical vehicle fuel consumption model is developed based on an input/output description of engine fuel consumption and transmission losses. Engine properties and fuel consumption are expressed in mean effective pressure (mep) units, while vehicle road load, acceleration and grade are expressed in acceleration units. The engine model concentrates on the low rpm operation. The fuel mep is approximately independent of speed and is a linear function of load, as long as the engine is not knock limited. A linear, two-constant engine model then covers the speed/load range of interest. The model constants are a function of well-known engine properties. Examples are discussed for naturally aspirated and turbocharged SI engines and for Diesel engines. A similar model is developed for the transmission where the offset reflects the spin and pump losses, and the slope is the gear efficiency.

This work presents an application of two sub-models relative to chemical-kinetics-based turbulent pre-mixed combustion modeling approach on the simulation of burn rate and emissions of spark ignition engines. In present paper, the justification of turbulent pre-mixed combustion modeling directly based on chemical kinetics plus a turbulence model is given briefly. Two sub-models relative to this kind of pre-mixed combustion modeling approach are described generally, including a practical PRF (primary reference fuel) chemical kinetic mechanism which can correctly capture the laminar flame speed under a wide range of Ford SI (spark ignition) engines/operating conditions, and an advanced spark plug ignition model which has been developed by Ford recently.