Search Results

Chassis dynamometer testing of two 60 foot articulated transit busses, one conventional and one hybrid, was conducted at the National Renewable Energy Laboratory's, ReFUEL facility. Both test vehicles were 2004 New Flyer busses powered by Caterpillar C9 8.8L engines, with the hybrid vehicle incorporating a GM-Allison advanced hybrid electric drivetrain. Both vehicles also incorporated an oxidizing diesel particulate filter. The fuel economy and emissions benefits of the hybrid vehicle were evaluated over four driving cycles; Central Business District (CBD), Orange County (OCTA), Manhattan (MAN) and a custom test cycle developed from in-use data of the King County Metro (KCM) fleet operation. The hybrid vehicle demonstrated the highest improvement in fuel economy (mpg basis) over the low speed, heavy stop-and-go driving conditions of the Manhattan test cycle (74.6%) followed by the OCTA (50.6%), CBD (48.3%) and KCM (30.3%).

Thermoplastics and composites are increasingly becoming popular among automotive design engineers because of their high specific stiffness and flexibility in manufacturing. While plastics like composites are orthotropic, unfilled thermoplastics like ABS Cycolac may be considered isotropic as they show little variation in properties between the flow direction and the direction transverse to the flow. However, this assumption is not enough to treat the latter as metals in finite element analysis. Metals like mild steel, offer considerable ductility, while thermoplastics show limited ductility and begin to fracture with several cracks appearing on the surface. Therefore, in the case of such plastics, it is important to consider the degradation of material properties in nonlinear finite element analysis using Damage Mechanics material law.

Two-point restrained and unrestrained 50 percentile male dummy tests were conducted on the Hyge Sled in a typical package configuration at 56 and 48 km/h respectively, with corrugated paper knee bolster simulations located close and far from the dummy's knees. The effect of bolster location on the various dummy measurements were compiled and trends were evaluated. Comparisons also were made between the performance of the Hybrid II and Hybrid III dummies. The Ford “Chest Load Distribution Transducer” also was used to infer changes in loading patterns on the lower rib cage as bolster spacing was varied. Bolster location affected many of the dummy measurements for the restrained tests and indicated the possible desirability for even further dummy measurement capability than used in this test program. Bolster location effects were masked in the unrestrained dummy tests by extreme dummy kinematics.

This study presents an efficient method for forensic engineers to determine the expected forward knee and hip displacements of automobile occupants who are restrained by seat belts during frontal impacts. The amount of knee displacement sustained by an occupant in a vehicular collision must be determined in order to assess seat belt usage and benefit. The results of this study may be referenced to model the lower body motion of vehicle occupants in frontal impacts for a range of impact severities. Previous research has empirically determined hip and limited knee displacements for subjects restrained in frontal impacts of specific severities; however, these research results have not been directly compared to produce a simple and practical model that is applicable for a range of collision severities.

Late model passenger cars and light trucks incorporate occupant protection systems with airbags and knee restraints. Knee restraints have been designed principally to meet the unbelted portions of FMVSS 208 that require femur load limits of 10-kN to be met in barrier crashes up to 30 mph, +/- 30 degrees utilizing the 50% male Anthropomorphic Test Device (ATD). In addition, knee restraints provide additional lower-torso restraint for belt-restrained occupants in higher-severity crashes. An analysis of frontal crashes in the University of Michigan Crash Injury Research and Engineering Network (UM CIREN) database was performed to determine the influence of vehicle, crash and occupant parameters on knee, thigh, and hip injuries. The data sample consists of drivers and right front passengers involved in frontal crashes who sustained significant injuries (Abbreviated Injury Scale [AIS] ≥ 3 or two or more AIS ≥ 2) to any body region.

The turning point in the process of nonlinear aging is a key feature to identify the nonlinear aging behavior of lithium-ion batteries. In order to identify the knee-point online, this paper studies the capacity “diving” phenomenon of the battery during the experiment and the regulation of the appearance of the turning point during the nonlinear aging process. Then, a knee-point identification method based on constant voltage charging capacity is proposed, and the linear and nonlinear stages of battery decay are redefined. Based on the change of constant voltage charging capacity in the constant current and constant voltage charging strategy, the method defines the aging process in which the constant voltage charging capacity remains invariant as the linear decay stage of the battery, and the aging process in which the constant voltage charging capacity rises rapidly as the nonlinear decay stage.

Equations predicting cord length per hose pitch, weight per unit hose length, and percent inner-liner coverage for plain stitch knitted automotive heater hoses are presented. These equations help hose manufacturers to determine the reinforcement cost for knitted hoses. A spreadsheet using these derived equations plus a hose burst equation from the literature also offers insight into key cord physical properties for knitted hoses. Cord loop tenacity (loop break strength) falls out as a key element in controlling knitted hose burst pressure.

Ceramic fibers with high specific surface area and adequate high-temperature strength are commercially available for filtration of diesel particulates and in-situ hot regeneration. The manufacturing of a deep bed filtration medium, using such brittle fibers, became possible after a special knitting technique was developed which forms the loops with minimum friction and pretension. Within this structure, the fibers are very little constrained and expose their active surface almost completely. Hence, high filtration efficiencies in the range of 95% could be demonstrated with favorable back-pressure characteristics. Blow-off phenomena were never observed. Endurance testing on engines, with full-flow burner regeneration, proved the high robustness to mechanical and thermo-mechanical loading. This is one of the particular advantages of the new concept.

Using advanced computer controlled knitting techniques pioneered by Courtaulds, 3-D fibre preforms suitable for Structural Reaction Injection Moulding (S.R.I.M.) can be produced in an automated and highly reproducible manner. Development of these techniques over the last two years has allowed glass, aramid and carbon fibres to be processed successfully. The technique is very versatile and a wide variety of 3-D shapes is possible. For example, a flanged ‘T’-junction preform in glass fibre has been evaluated as a concept component in a Courtaulds S.R.I.M. research programme. Specific preforms have been developed for applications in the automotive, aerospace and general engineering industries. The advantages of these knitted 3-D preforms are reproducibility, high production rates, fibre continuity throughout the structure, zero waste and the ability to mix fibres easily.

Knitted vinyl is produced by slitting calendered polyvinyl chloride film and knitting the resulting “threads” into a material having physical properties characteristic of vinyl upholstery combined with the styling flexibility of textiles. The porosity of the product makes it the most breathable type of supported polyvinyl chloride yet introduced.

A reduction of engine knock intensity is demonstrated by incorporation of a stepped piston top to provide an abrupt increase in flame front area in an ASTM-CFR octane rating engine. The conclusions are based on several different types of knock measurements. Three different piston designs were tested. Decreases in the knock intensity, the magnitude of the pressure oscillations following knock, of up to 40% were realized. The statistical nature of knock is shown to be somewhat different from a normal distribution. The data have more scatter, particularly toward the high side of the mean value.

Knock is an abnormal phenomenon with in-cylinder pressure oscillations, which must be avoided to protect the engine from damage and to avoid excessive noise. Conventional control algorithms delay the combustion with the spark to avoid high knocking rates but reduce the thermal efficiency and restricts the performance of a spark ignition engine. The detection and characterization of low-knocking cycles might be used for improving knock control algorithms, however, it is a challenging task, as normal combustion also excite the different resonance modes and might be confused with knock. Most of the methods found in literature for knock detection use 0-Dimensional indicators, regardless of the angular evolution of the pressure oscillations. In this paper, the in-cylinder pressure oscillations evolution during the piston stroke is analyzed by using various time-frequency transformations.

A general definition and an index for the assessment of different engine knock behavior have been developed. The knock onset locations have been determined by piezoresistive pressure actuators and optical fiber probes in full load engine operation mode. The thermodynamic conditions at the knock onset locations have been quantified by CFD-calculations. Therefore the local fuel concentration, mixture temperature and residual gas concentration have been considered. These calculated thermodynamic conditions were further used to calculate the necessary volume of an exothermal center for the generation of the maximal measured pressure amplitudes.

Experiments were performed to identify the knock trends of lean hydrocarbon-air mixtures, and such mixtures enhanced with hydrogen (H2) and carbon monoxide (CO). These enhanced mixtures simulated 15% and 30% of the engine's gasoline being reformed in a plasmatron fuel reformer [1]. Knock trends were determined by measuring the octane number (ON) of the primary reference fuel (mixture of isooctane and n-heptane) supplied to the engine that just produced audible knock. Experimental results show that leaner operation does not decrease the knock tendency of an engine under conditions where a fixed output torque is maintained; rather it slightly increases the octane requirement. The knock tendency does decrease with lean operation when the intake pressure is held constant, but engine torque is then reduced.

Utilizing the desirable feature of hydrogen, this study demonstrates the improvement of engine performance and exhaust emissions due to the mixing of hydrogen into natural-gas fuel in a spark-ignition engine at the wide-open throttle (WOT) condition. Both hydrogen and natural-gas fuels were injected into the intake port only in the suction flow, which could make the operation under a wide range of conditions without backfire even at a hydrogen fuel. Based on the measured processes of combustion, the knock characteristics were discussed with special attention to the extremely high burning velocity of hydrogen. At a higher compression ratio, the thermal efficiency in the stoichiometric condition was improved, nevertheless a precise control of ignition timing was required to suppress a hard knock. From the experimental results of engine performance in a variety of parameters, optimal use of hydrogen was exhibited for different engine loads.

A rapid compression/expansion machine (RCEM) based on a single-cylinder engine was developed to understand the fundamental phenomenon of knock during spark-ignition (SI) combustion. In order to cause auto-ignition in the end-gas mixture during the flame-propagation process, and also to visualize the processes, the original head of the engine was replaced with a specially designed combustion chamber. The effects of spark timing, compression ratio and equivalence ratio on knock intensity were systematically investigated using the RCEM with n-butane fuel. In addition, the possibility of knock control by the injection of hydrogen into the end-gas region is also discussed. The experimental results indicate that a higher compression ratio, spark-ignition timing at -10 °ATDC and a stoichiometric equivalence ratio cause heavy knock. However, the knock intensity is drastically decreased with hydrogen injection.

The knock characteristics of natural gas (NG), 89 octane unleaded gasoline, 2,2-dimethyl butane (22DMB), and methyl tert-butyl ether (MTBE) in stoichiometric and lean fuel-air mixtures were studied in a production 4-cylinder automotive engine. The Intake Temperature at the Knock Limit (ITKL) was found to be very different for each fuel but in every case the ITKL of lean mixtures was much higher than that of a stoichiometric mixture. Gasoline and 22DMB exhibited a much greater increase in ITKL than MTBE and NG at lean conditions. Surprisingly, for lean mixtures 22DMB exhibited values of ITKL that were much higher than MTBE and almost as high as those of NG. These results are compared with a detailed numerical model of autoignition chemistry. Good agreement between model and experiment is found for all modelled conditions.

In modern turbocharged downsized GDI engines the achievement of maximum thermal efficiency is precluded by the occurrence of knock. In-cylinder pressure sensors give the best performance in terms of abnormal combustion detection, but they are affected by long term reliability issues and still constitute a considerable part of the entire engine management system cost. To overcome these problems, knock control strategies based on engine block vibrations or ionization current signals have been developed and are widely used in production control units. Furthermore, previous works have shown that engine sound emissions can be real-time processed to provide the engine management system with control-related information such as turbocharger rotational speed and knock intensity, demonstrating the possibility of using a multi-function device to replace several sensors.

The different demands with respect to electronic knock control in the USA, Japan and Europe are compared. Available systems to suit the special European requirements of turbocharged and naturally aspirated engines are presented in detail. The influence of the new European emission standards currently under discussion and their effect on the requirements of such systems are considered. Alternative approaches for future systems are discussed.

Today, knock control is part of standard automotive engine management systems. The structure-borne noise of the knock sensor signal is evaluated in the electronic control unit (ECU). In case of knocking combustions the ignition angle is first retarded and then subsequently advanced again. The small-sized combustion chamber of small two-wheeler engines, uncritical compression ratios and strong enrichment decrease the knock tendency. Nevertheless, knock control can effectuate higher performance, lower fuel consumption, compliance with lower legally demanded emission limits, and the possibility of using different fuel qualities. The Knock-Intensity-Detector 2 (KID2) and the Bosch knock control tool chain, based on many years of experience gained on automotive engines, provides an efficient calibration method that can also be used for two-wheeler engines. The raw signal of the structure-borne noise is used for signal analysis and simulation of different filter settings.