Search Results

The National Transportation Safety Board examined the effect of not using an age-appropriate restraint system and the effect of not using a restraint system properly on injury severity. The Safety Board found that improperly restrained children in an age-appropriate restraint system sustained a greater proportion of moderate or worse (AIS 2-6) injuries than properly restrained children who were in the wrong restraint for their size. This was true particularly for infants and small children who were likely to be in a child restraint system. The study underscores the importance of proper use of restraint systems and makes recommendations for improvements in restraint system designs for children.

A light duty truck Renault Trafic with a naturally aspirated 2.5 l engine was equipped with ceramic DPFs of different sizes, installed at different positions along the exhaust line of the vehicle. The filters were operated on diesel fuel doped with a cerium based additive at concentration of 100 ppm in the fuel. Tests were carried out on chassis dynamometer using the urban part of the new European driving cycle and the full new European Driving cycle. Comparisons are made between the different sizes and positioning as regards both back-pressure build-up and catalytic regeneration behavior. The results show that filter regeneration was always possible at continuous low speed driving, at relatively high filter back-pressure levels (i.e. high particulate accumulation in the filter), with an effect on fuel consumption.

Friction materials with three different formulations containing different solid lubricants were investigated to study the role of lubricants on the friction performance. The three friction materials contained 10 vol.% graphite, 7 vol.% graphite + 3 vol.% Sb2S3, and 7 vol.% graphite + 3 vol.% MoS2, respectively, with the same amount of other ingredients. Results of this work showed that each formulation had advantages and disadvantages. The friction materials containing two lubricants (graphite + MoS2 or Sb2S3) showed better resistance to fading and improved friction stability than the friction material containing only graphite. However, the friction materials with two lubricants showed disadvantages on anti-fading, wear resistance, and DTV generation.

Current vehicle wiring harness design is foundationally affected by several key requirements. One of these, the need for a single or small number of co-located circuit protection centers, dictates the topology that most vehicles in production today use. By relaxing this requirement through the use of relatively new semiconductor devices, a fundamentally different wiring topology can be realized, one that has superior weight characteristics and a less wire intensive topology. This paper will discuss the requirements on the semiconductor devices necessary to fulfill this requirement and the market implications of the overall approach.

A study was conducted to examine the effect of solidification time and solution treatment time on the tensile properties of a 319-type aluminum alloy. Tensile samples with solidification times ranging from 0.3 to 35.5 minutes were solution-treated at 495 C for 8 hours and for 240 hours. All samples were then water-quenched and aged at 260 C for 4 hours. The tensile results show that solidification time and solution treatment time can have significant effects on the tensile properties. In general, as the solidification time increased, the ultimate strength, yield strength, and ductility decreased; increasing the solution-treatment time from 8 to 240 hours improved only the tensile strengths. The amount of Cu available in solid solution to precipitate during aging is found to be a key factor. Additionally, coarse microstructures require very long (and commercially-impractical) solution-treatment times to significantly improve the tensile strengths.

A study was conducted to determine how the mechanical properties of an A356-T6 Aluminum alloy are affected by solidification time. Solidification time has been found to have a large effect on the microstructure, especially in terms of the size of the SDAS as well as the size and distribution of porosity. Solidification time also has a large effect on the ultimate tensile strength, ductility, and fatigue properties of A356-T6 Al. Comparisons between porosity-containing (“As-Cast) and porosity-free (“As-Cast + HIP”) samples revealed that the presence of porosity had a dramatic effect on fatigue life; tensile properties remained unaffected.

The effect of four “fuel economy” additives on engine performance has been evaluated in both laboratory and field engines. The additives included a colloidal graphite, a colloidal molybdenum disulphide and two oil soluble molybdenum compounds. The purpose of the program was to evaluate the additives with regard to engine wear and deposits and not fuel economy. Engine performance debits were encountered for all four additives, ranging from engine failures to high piston ring wear and groove fill and oil filter blockage. Similarities between the field and laboratory engines were observed for piston groove deposits and ring wear.

Possible mechanisms for smoke formation in the diesel engine are discussed. Emphasis is placed on the effects of some engine and fuel factors on carbon formation during the course of combustion, including cetane number, fuel volatility, air charge temperature, and after-injection. The tests were made with a single-cylinder, open chamber research engine, with three fuels, covering a wide range of inlet air temperatures and pressures. There is evidence that smoke intensity increased with increase in the cetaine number of the fuels with inlet air temperatures near atmospheric. Increase in the air charge temperature caused an increase in smoke intensity for volatile fuels and had an opposite effect on less volatile fuels for the open chamber engine used. The smoke intensity was found to increase dramatically with after-injection, with all other parameters kept constant. The concept that flame cooling is the main cause for smoke formation is examined.

We are currently faced with the possibility of operating millions of passenger cars and trucks on gasolines free of lead whereas they were designed to operate with leaded gasoline. The studies discussed in this paper illustrate the potential engine damage in the form of exhaust-valve seat wear that could result from such a move. This work shows that the inclusion of phosphorus in zero-lead gasoline is not a complete solution to the exhaust-valve seat wear problem, but that as little as 0.5 gm of lead per gallon in gasoline can provide complete exhaust-valve seat wear protection under relatively severe conditions of speed and load. Comparison of photomicrographs of exhaust valves and exhaust valve seats run with zero-lead and 0.5 gm leaded gasolines permits speculation on the mechanism responsible for exhaust valve seat wear in engines fueled with zero-lead gasoline.

Laboratory and field tests were conducted to determine how changes in some gasoline compositional factors might affect atmospheric visibility and soiling caused by exhaust particulate matter emitted from late model automobiles. In the laboratory tests, measurements of light scattering, soiling index, and mass emission rates of air-suspendible particles were made on diluted exhaust from cars driven on a programmed chassis dynamometer. These tests showed that light scattering, and also soiling, were increased by increasing the aromatic content, removing lead antiknocks, or increasing the combined amounts of sulfur and phosphorus in gasoline. Field tests in a turnpike tunnel used two 4-car fleets operating on leaded and unleaded premium gasoline of high and average aromatic content. The air in the tunnel sampled during the tests with the cars using the unleaded gasolines soiled the filters 57% more than the air sampled during the tests with the cars using the leaded gasolines.

This paper presents a computational investigation of the effect of space velocity on the dynamic performance of an automotive catalytic converter. The objective is to develop a better fundamental understanding of the converter's performance under actual driving conditions. The study employs a single-channel based, one-dimensional, non-adiabatic model. The transient effects are considered by modulating the air-fuel ratio and compositions of the exhaust gases entering the catalyst. The results elucidate the role of space velocity in determining the catalyst behavior under transient conditions. At high space velocities, the catalyst performance is relatively more influenced by imposed transients.

The present paper aims to investigate the influence of spark ignition on CAI combustion based on internal EGR strategy. Controlled Auto-ignition (CAI) combustion is facilitated in a Ricardo single cylinder engine with a pair of special camshafts, which valve lift and cam profile are modified to trap enough hot residuals. Operation regions and other detailed combustion characteristics of the CAI engine operation are analyzed and compared between pure CAI mode and the CAI mode with assisted spark ignition. The results show that spark ignition can play an important role in controlling CAI combustion ignition in low load boundary region. The low temperature chemical reaction process is shortened and the auto ignition timing is advanced due to the spark discharge. Meantime, lower fuel consumption and cycle-to-cycle variations can be achieved.

Measurements are presented showing the effect of swirl level and spark location on burn duration in a homogeneous-charge engine. Laser shadowgraph photographs of the flame structure were used to help interpret the observed results. As expected, without swirl the burn duration was a direct function of flame travel distance, such that central ignition was optimal. When swirl was introduced, off-axis ignition was aided by flame-holder effects that enhanced the flame speed in the circumferential direction. However, only for the highest swirl level studied (swirl number = 8.3) was the burn rate increased by moving the ignition point toward the cylinder wall. For lower swirl levels, central ignition was still preferable.

An experimental study of the effect of spark power on the growth rate of spark-ignited flame kernels was conducted in a turbulent flow system at 1 atm, 300 K conditions. All measurements were made with premixed, propane-air at a fuel/air equivalence ratio of 0.93, with 0%, 8% or 14% dilution. Two flow conditions were studied: a low turbulence intensity case with a mean velocity of 1.25 m/sec and a turbulence intensity of 0.33 m/sec, and a high turbulence intensity case with a mean velocity of 1.04 m/sec and a turbulence intensity of 0.88 m/sec. The growth of the spark-ignited flame kernel was recorded over a time interval from 83 μsec to 20 msec following the start of ignition using high speed laser shadowgraphy.

Using spark retard during a cold-start is a very effective means of achieving fast catalyst light-off. In addition to obtaining faster catalyst light-off, retarding the spark also results in lower engine-out HC emissions. The objective of this research was to understand the reasons for the decrease in HC emissions with spark retard. In order to make the results as unambiguous as possible, the experiments were performed on a dynamometer at constant speed and load conditions using pre-vaporized, premixed gasoline. A zero-dimensional ring-pack crevice flow model was used to determine the mass flows into and out of the piston crevice during the engine cycle. The analysis showed that with spark retard a large fraction of the unburned fuel from the ring-pack re-entered the cylinder before the end of flame propagation, and was consumed by the flame when it extinguished on the cylinder wall.

The performance of zeolite based, catalyzed hydrocarbon (HC) traps were evaluated with different inlet HC species and warm up profiles. Five different settings of cold–start spark timing were used each on separate FTP75 vehicle emission tests with constant neutral engine idle speed and fueling schedule. A test vehicle aftertreatment system that consisted of two converter assemblies, close-coupled and underbody, was modified by exchanging the bricks in the latter assembly with HC traps. With increasing spark retard from 9° BTDC to −17° BTDC, exhaust temperature increased, engine–out non–methane hydrocarbon (NMHC) emissions decreased, the concentration of large chain (C6+) HC species decreased and the small chain (C2–3) HC species increased. Lab flow reactor experiments showed that HC traps do not effectively manage small chain HC species with efficient adsorption or retention to conversion.

The partnership for advancing combustion engines (PACE) is a US Department of Energy consortium involving multiple national laboratories and includes a goal of addressing key efficiency and emission barriers in light-duty engines fueled with a market-representative E10 gasoline. A major pillar of the initiative is the generation of detailed experimental data and modeling capabilities to understand and predict cold-start behavior. Cold-start, as defined by the time between first engine crank and three-way catalyst light-off, is responsible for a large percentage of NOx, unburned hydrocarbon and particulate matter emissions in light-duty engines. Minimizing emissions during cold-start is a trade-off between achieving faster light-off of the three-way catalyst and engine out emissions during that period.

Tests were conducted on a variety of commercially available spark plugs to determine the influence of igniter design on initial kernel formation and overall performance. Flame kernel formation was investigated using high-speed schlieren visualization. The flame growth rate was quantified using the area of the burned gas region. The results showed that kernel growth rate was heavily influenced by electrode geometry and configuration. The igniters were also tested in a bomb calorimeter to determine the levels of supplied and delivered energy. The typical ratio of supplied to delivered energy was 20% and igniters with a higher internal resistance delivered more energy and had faster kernel formation rates. The exception was plugs with large amounts of conductive mass near the electrodes, which had very slow kernel formation rates despite relatively high delivered energy levels.

This research focused on the effects of split injection on fuel spray behavior in a diesel environment. It was done in a special designed engine-fed combustion chamber (swirl ratio of 5) with full field optical access through a quartz window. The simulated engine combustion chamber used a special backwards spraying injector (105°). The electronically controlled injector could control the size and position of it's two injections. Both injections were through the same nozzle and it produced very rapid injections (1.5 ms) with a maximum injection pressure of 130 MPa. Experimental data included: rate of injection, injector pressure, spray plume images, tip penetration, liquid and vapor fuel distributions, combustion pressure, and rate of pressure rise. From 105° forward scatter images, tip penetration was observed to be very rapid and reached a plateau at 25 mm.

This research focused on the effects of split injection on combustion in a diesel environment. It was done in a specially designed engine-fed combustion chamber (swirl ratio of 5) with full field optical access through a quartz window. The simulated engine combustion chamber used a special backwards spraying injector (105°). The electronically controlled injector could control the size and position of it's, two injections. Both injections were through the same nozzle and it produced very rapid injections (1.5 ms) with a maximum injection pressure of 130 MPa. Experimental data included: rate of injection, injector pressure, combustion chamber dumping (NO & NOx concentrations), flame temperature, KL factor (soot concentration) combustion pressure, and rate of pressure rise. Injection rates indicate that the UCORS injection system creates very rapid injections with the ability to produce controllable split injections.