Search Results

High speed Schlieren cinematography along with flame contour analysis is used to study the early flame propagation, from spark to a 4 mm flame radius. This is done for lean propane–air mixtures, and up to 1500 RPM. For normal engine speeds, the flame is turbulent immediatly after initiation, with no laminar phase. The burnt kernel is first driven by the electric ignition source. After about 0.5 ms, the effect of engine speed (i.e. turbulence) is very strong, the kernel expansion rate increasing with engine speed. Increasing the equivalence ratio also increases the propagation speed. The rate of flame growth measured in the engine is shown to go through a minimum for a burnt kernel radius of about 2 mm which varies with the equivalence ratio. The minima of the flame velocity at this radius depend on mixture strength and turbulence level. The simultaneous recording of the pressure trace shows a correlation between the early flame behavior and the overall combustion speed.

A computer model is developed to predict engine performance and exhaust emissions in a spark-ignition engine. In the model, combustion phenomenon is analyzed by the turbulent combustion model which considers the effect of the turbulence and the combustion chamber on combustion. The gas exchange process is calculated by one dimensional isentropic flow through a nozzle. During combustion, 13 products are obtained by chemical equilibrium, and nitric oxide (NO) formation is calculated by the extended Zeldovich mechanism. The results of the computer model are compared with the experimental results. The calculated values for pressure and NO emission show good agreement “with the experimental data. The effects of the engine speed, spark timing, air fuel ratio, and EGR are studied by the model.

Recent reports of significant H2S emissions from single-bed three-way catalyst equipped vehicles have prompted vehicle and laboratory studies of the mechanism of H2S formation over three-way catalysts. Vehicle studies have shown the occurrence of short duration H2S emissions significantly higher than fuel sulfur inlet levels under certain transient conditions. These emissions cannot be explained by the previously reported steady-state conversion of SO2 to H2S. Laboratory flow reactor studies have identified a second mechanism for H2S formation involving the rapid reductive release of sulfur stored on the catalyst surface. This mechanism can account for H2S emission levels which can significantly exceed inlet fuel sulfur levels for short durations. Results are presented to define factors which affect H2S formation under these two mechanisms and to determine methods for controlling these emissions under vehicle operation.

Piston ring moving zone in the cylinder is one of the most critical lubrication regimes in diesel engines. This area is susceptible to combustion substances. In particular, abnormal wear is occasionally detected due to Exhaust Gas Recirculation (EGR) system equipment. In Japan, NOx emission requirements for passenger car diesels have become more stringent effective October 1, 1986. OEMs tend to apply EGR systems to reduce NOx in exhaust gas. In order to identify the phenomenon of abnormal cylinder wear of EGR equipped engine, engine bench tests were conducted under varied conditions in EGR equipment, cooling water temperature and fuel sulfur content. The test results suggest that wear caused at low temperature is mainly corrosive wear attributable to sulfuric acid formed by reaction with fuel sulfur and condensed water.

In order to obtain data about human head tolerance, the APR Laboratory of Biomechanics has developed a specific methodology for volunteer boxers. These ones are used because they expose themselves, in their normal body activities, to direct head impacts similar in nature to those experienced by vehicle occupants under crash conditions. This paper describes the specific experimental technique that permits association of the severity of the blows, measured in terms of physical parameters, to corresponding physiological effects, measured in medical terms.

An analysis of data provided by-vehicle manufacturers during the California emissions certification process has been performed for 1983-1987 model-year light-duty vehicles. The major change in emission control system design was a decrease in the use of secondary air injection which was used on 75% of 1983 vehicles, but only 50% of 1986 and 1987 vehicles. Exhaust gas recirculation was used on 90% of vehicles from 1983-1987. The sales-weighted certification emission levels of gasoline-powered light-duty vehicles were 0.23 g/mile HC, 3.1 g/mile CO, and 0.5 g/mile NOx in 1983. Levels of HC and CO were approximately constant at 0.20 g/mile and 2.7 g/mile, respectively, from 1984-1987 with NOx levels decreasing to 0.4 g/mile for 1987.

The relationship between H2S emissions from three-way catalysts and the storage of sulphur on the catalyst surface has been investigated. Thermodynamic data predict that sulphur storage primarily will occur on Al2O3 and CeO2 under lean and stoichiometric conditions, at up to 500°C. Rich transients could then induce the decomposition of the Ce-S-O and Al-S-O compounds, releasing sulphur into the gas phase. Experimental studies have supported this model. A mechanism has been proposed for the subsequent formation of H2S. The mechanism by which catalyst poisons attenuate H2S emissions from engine-aged catalysts also has been studied. The effect has been shown to be related to decreased storage of sulphur, caused by stable catalyst-poison species at the catalyst surface.

Diesel fuels have been tested in both a naturally aspirated and an externally supercharged single cylinder, air cooled KHD DI-diesel engine, to determine the influence of poor fuel quality on combustion and emissions. A thermodynamic analysis of the cylinder pressure was conducted and the emissions were measured both gaseous as well as the particle emission (by means of a dilution tunnel). Additionally, extensive cold start tests were conducted. Under steady state conditions the cetane number seems to be a good parameter which describes the ignition behavior of different fuels. At low load, a change in combustion and a high increase in CO, HC and particle emissions were found with decreasing cetane number. During cold starting and warming up, a clear deterioration of the emission and combustion characteristics was also observed with decreasing cetane number when basic fuels were used.

Kloeckner-Humboldt-Deutz AG (KHD) has developed a glow plug assisted heavy-duty methanol engine based on the standard production diesel engine F8L 413F. This type of engine is an air-cooled, 8-cylinder, V-type engine with a high swirl direct injection combustion system. The paper presents the development of a glow plug-based hot surface ignition system and the combustion system optimization work done to obtain high engine efficiency and low emission levels. Furthermore, it deals with the development of methanol specific engine components for the purpose of achieving a high reliability and long life. In the whole operational range the methanol engine exhibits an energy consumption nearly equal to its diesel counterpart, together with an excellent emission quality, capable of meeting the 1994 EPA emission standards for heavy-duty engines.

CYLINDER PRESSURE OSCILLATIONS in Diesel engines are known to arise with the beginning of combustion. They excite resonant oscillations in the cylinder's bulk load, which generally have been considered unimportant for combustion noise or thermodynamic effects. A new method of investigation has been developed by means of a proprietary computer program for the general analysis of acoustic signals (SIAN). Adapted to investigations of the cylinder-pressure signal it showed, that resonant oscillations dominate the entire high-frequency cylinder-pressure spectrum. These oscillations govern the annoying high frequent combustion noise as well as the combustion speed and, thus, the combustion process itself.

One of the most important noise sources of an internal combustion engine powered vehicle or equipment is the engine itself. Consequently, noise abatement measures should first be applied to the engine, where they could be more effective from the cost/benefit standpoint. This paper deals with the reduction of noise excitation and vibration transmission through optimization of the combustion process (injection timing, swirl, configuration, pilot injection …) and of the components design. To analyze the acoustical behavior of structures, FEM and Modal Analysis can be used. The results permit a ranking of the structures relative to other components, as far as their noise pattern is concerned, as well as identification of specially weak points, which can then be corrected.

Today's task of providing effective, state of the art tactical vehicles to all branches of our fighting forces is coupled with acute cost-awareness. Military decision makers, as well as their civilian suppliers, are emphasizing the procurement of standard commercial vehicles, or vehicles that do not require great R&D outlays. The term used to describe these acquisitions is NDI-Non-Developmental Items. This paper reviews current heavy duty transmission configurations, and shows modifications that may be necessary to meet military requirements.

This paper summarizes technical progress in a study of incipient fault detection in bus engines. The types of failures to which this method is applicable are those for which there is a gradual deterioration to failure over a relatively long time. In addition this method can also quickly isolate failed components. The fundamental basis of predicting such a fault is real time measurements of engine performance in the form of instantaneous brake torque and the nonuniformity in that torque. For our studies a number of buses were instrumented for real time performance measurements in simulated route operation. A data base was established for those measurements from which the statistical model for predicting failure has been developed. This paper explains the theory of the method, the instrumentation, the experimental results and the statistical model upon which failure prediction is based. The results of this study are applicable to an optimum strategy for maintenance scheduling.

Several years of studies and experimentation commencing in 1977 at the Canadian National Research Council, have culminated in the construction of a regenerative power train of the parallel hybrid type. This paper presents the results of fuel economy tests conducted with the power train as installed in a North American City Bus. Testing was carried out using the Arterial and City Business District phases of the ADB cycles, together with a 5 stop per mile, 30 mph (48 km/h) cycle. Interestingly, with an unmodified bus, the 30 mph cycle was found to require 19% more fuel than the cycle average of the Arterial and City Business District Phases. In comparison with the same bus operating without the benefit of the regeneration package, a reduction in fuel consumption of some 17% was obtained. Even better comparative results are expected of the same system when used in typical city driving situations.

A background review of soil compaction processes is presented and theoretical relationships among loads, pressures and soil moisture are discussed. Research directions and needs for the future are outlined. THE EFFECT OF SOIL COMPACTION, especially below normal tillage depths, is a major agricultural concern today. In general, heavy axle loads on moist soil is the primary cause of excessive compaction, But important questions remain: How heavy? How wet? Do low pressure high flotation tires help?

A Methanol catalyst test program has been conducted in two phases. The purpose of Phase I was to determine whether a base metal or lightly-loaded noble metal catalyst could reduce Methanol engine exhaust emissions with an efficiency comparable to conventional gasoline engine catalytic converters. The goal of Phase II was the reduction of aldehyde and unburned fuel emissions to very low levels by the use of noble metal catalysts with catalyst loadings higher than those in Phase I. Catalysts tested in Phase I were evaluated as three-way converters as well as under simulated oxidation catalyst conditions. Phase II catalysts were tested as three-way converters only. For Phase I, the most consistently efficient catalysts over the range of pollutants measured were platinum/rhodium configurations. None of the catalysts tested in Phase I were able to meet a NOx level of 1 gram per mile when operated in the oxidation mode.

The effects of compression ratio on the history of the fuel-burning process -was investigated in a single-cylinder direct-injection diesel engine. Two compression ratios of 21.4 and 18.5 were studied by using two wide and shallow bowls. The engine was operated at different speeds and overall air-fuel ratios, but with constant start-of-combustion timing at top dead center. The measured cylinder pressure was used to derive fuel-burning rate. At all conditions, the low-compression-ratio bowl had a larger mass of premixed-burned fuel and a higher peak specific fuel-burning rate. The fuel-burning rate in the diffusion-controlled phase of combustion decreased with decreasing compression ratio. The resulting combustion duration became longer at reduced compression ratio, and the difference could be as large as 14 crank-angle degrees.

The predictive capability of a phenomenological spray-combustion model was evaluated for diesel engine performance, combustion, and emissions. The data used for comparisons with the predictions resulted from tests on two single-cylinder research-type open-chamber diesel engines -- a 2.0-L per cylinder heavy-duty engine and a 0.52-L per cylinder light-duty engine. The data covered wide ranges of speed and overall air-fuel ratio. Such global performance quantities as indicated mean effective pressure and indicated thermal efficiency predicted by the model agreed with experimental results from both engines within 5%. Pressure-time and heat-release rate predictions agreed within 5-15%. However, further improvements are needed before the model can be used reliably for emissions predictions. Specifically, predictions of nitric oxide (NO) and non-volatile particulate (soot) were in poor agreement with the measurements, especially for the light-duty engine.

The rapid expansion of combustion products in a diesel cylinder generates high-frequency acoustic waves which cause errors in the computed heat-release signature. In this study, the effects of spline smoothing and digital filtering on the computed heat-release history were investigated. Experiments were performed on a heavy-duty single-cylinder diesel engine. In some cases the computed heat-release history was rendered unusable by the acoustic waves, which were centered at a frequency of 3.7 kHz for this engine, even after spline smoothing was applied to the pressure data. In contrast, a low-pass digital filter developed for this study was found to be very effective for removing acoustic noise from heat-release signatures without adversely affecting the computed indicated mean effective pressure.

Combustion zone (flame) propagation and flow velocities are measured using optical measurement techniques in a single-cylinder direct injected diesel engine. Combustion and, hence, flame propagation is detected by optical fibers and flow velocities have been measured by a new single-color, 2 dimensional Laser Doppler Velocimeter (LDV). Flame propagation and flow velocities could not be measured simultaneously. Consequently, pressure traces which were recorded during each measurement served as a criterion for selecting similar combustion cycles from flame and flow velocity measurements. The operational speed of the engine was 1100 rpm and the power cylinder was configured with a combustion bowl in the piston. For the purpose of the tests, the intake swirl number was either 1.8 or 4.2, the latter corresponding to the application of a shrouded inlet valve. It has been shown that variation of several significant engine parameters influences both combustion and fluid flow history.