Showing papers on "Spark-ignition engine published in 1988"

Fiber-optic instrumented spark plug for measuring early flame development in spark ignition engines

Abstract: An optical probe for measuring the motion and rate of growth of the early flame kernel in spark ignition engines is described. The probe consists of a standard spark plug with eight optical fibers installed in a ring at the base of the threaded region of the plug. The fibers collect the light emitted from the flame as it crosses the field of view of the fibers, and transmit the light to photomultiplier tubes. The time from ignition until detection of the flame is used to compute the average flame velocity in the direction of each fiber relative to the spark location. The real-time data acquisition system permits statistical analysis of cycle-by-cycle variations in the combustion rate.

Flow Field Effects on Flame Kernel Formation in a Spark-Ignition Engine

Abstract: The effects of mixture turbulence and mean flow velocity on flame kernel formation in a spark-ignition engine were investigated using a disc-shaped optically accessible side chamber. Three-dimensional flow predictions and LDA measurements were performed to get a better understanding of the flow field in this combustion chamber. Thinwire electrodes were located at a peripheral and a central position introduced into the combustion chamber via the glass windows. High-speed schlieren films at 40 kHz were taken from two orthogonal directions to visualize in detail the formation and development of the flame kernel. The purpose was to gain a better understanding of the interaction of turbulence and flame during the first milliseconds after spark breakdown of a transistorized coil ignition system and a capacitor discharge ignition system.

An Analytical Study on Knocking Heat Release and its Control in a Spark Ignition Engine

Abstract: In this study the relationship between the timing for the onset of autoignition and the amount of mixture fraction burned by autoignition and the resulting knock intensity is investigated using a combination of high-speed laser shadowgraphy and thermodynamic calculations. The experimental procedure is applied to examine the effect of a squish combustion chamber on suppressing knock. The results indicate that, when autoignition occurs in the squish area, an amount of mixture burned by autoignition is small, resulting in lower knock intensity

Cycle-Resolved Two-Dimensional Flame Visualization in a Spark-Ignition Engine

Abstract: A cycle-resolved two-dimensional flame visualization technique using Mie-scattering from submicron sized smoke particles added to the homogeneous charge mixture of a spark-ignition engine has been developed. This diagnostic technique was applied to a square piston engine with four windows. Pulsed laser sheets were generated by a copper vapor laser at a frequencies of 6 kHz. The light scattered by the smoke particles was collected by a drum camera on high sensitivity photographic film.

Properties, Performance and Emissions of Medium Concentration Methanol-Gasoline Blends in a Single-Cylinder, Spark-Ignition Engine

Abstract: Experiments were carried out in a spark-ignited, single-cylinder, variable compression ratio, Waukesha RDH engine with primarily commercial grade unleaded gasoline, commercial grade methanol, M30, M50 and M70 methanol-gasoline blends to compare efficiency, performance and emissions characteristics. The fuels were compared at their knock-limited compression ratios and MBT spark-timing. In addition, fuel properties, such as research and motor octane qualities, volatility, heating values and cloud points of methanol-gasoline blends were determined

The Use of Dimethyl Ether as a Starting Aid for Methanol-Fueled SI Engines at Low Temperatures

Abstract: Methanol-fueled SI engines have proven to be difficult to start at ambient temperatures below approximately 10/sup 0/C. The use of dimethyl ether (DME) is proposed to improve the cold starting performance of methanol-fueled SI engines. Tests to evaluate this idea were carried out with a modified single-cylinder CFR research engine having a compression ratio of 12:1. The engine was fueled with combinations of gaseous dimethyl ether and liquid methanol having DME mass fractions of 30%, 40%, 60% and 70%. For comparison, tests were also carried out with 100% methanol and with winter grade premium unleaded gasoline. Overall stoichiometric mixtures were used in all tests.

Two-Component Laser Velocimeter Measurements in a Spark Ignition Engine

Abstract: Simultaneous two-component laser Doppler velocimeter measurements for homogeneous charge combustion in a spark ignition engine are used to calculate ensemble-averaged turbulence stresses Cyclic variation hias in the data is reduced by conditional sampling 011 the flame arrival time at the probe volume Results are presented for engine speeds of 300 600 and 1200 rpm The lower speed is believed to be transitional because the general character of the fluid motion is found to he unique For the two higher engine speeds the following conclusions can he made: (1) The precombustion turbulence is highly anisotropic with the component parallel to the piston surface nearly double the component in the direction of piston motion; (2) both the norrnul and shear turbulence stresses scale with mean piston speed; (3) combustion does not have an appreciable effect on either the preflame or postflame normal turbulence stresses hut compression in front of the flame docs appear to reduce the degree of correl

Photography of Combustion During Knocking Cycles in Disc and Compact Chambers

Abstract: Combustion during normal and knocking cycles has been observed in a single cylinder, spark ignition engine. Photographs of combustion in a disc chamber showed that autoignition of the end gas was the cause of knock. It was concluded that knock resulted from rapid entrainment and burning of reactants by the normal spark ignited flame

The effect of swirl on combustion in a pancake chamber spark ignition engine

Abstract: This experimental investigation is an initial step in separating the influences of swirl and inducted kinetic energy on combustion in a homogeneous charge engine. By rotation of the intake port about the axis of the intake valve, the swirl ratio was varied from zero to 2.8 while maintaining constant intake port flow, and hence constant inducted kinetic energy. Combustion data were obtained at a low speed, light load operating point (1500 RPM/60 psi IMEP) with MBT spark timing. The effects of the increase in swirl were a 25% decrease in ignition delay, a 10% decrease in combustion duration, and a significant improvement in combustion stability. Estimates were made on the effect of swirl on turbulence intensity (10% increase) and integral length scale (10% decrease). Both the increase in swirl and the use of a near-central spark plug location improved the lean operability. This enabled the ISFC to be reduced by more than 11% compared with the case of peripheral spark plug and zero swirl at equal combustion stability. In this comparison, the reduced ISFC via lean operation was accompanied by a decrease in ISNO/sub x/ from > 16 to 0.4 and an increase in ISHC from < 1.9 to 6.8more » gm/IHP-HR.« less

Adaptive control system for an internal combustion engine

Abstract: An adaptive control system for a four cylinder spark ignition engine includes a memory (35) containing basic values and a memory (38) containing correction values for the spark advance angle. From these values basic and correction values are calculated and added in a summer (37). The output of summer (37) is supplied to one input of a summer (41), the output of which is supplied to the input of a dwell control device (17). In order to apply positive and negative perturbations to the spark advance angle, the output of a perturbation generator (40) is applied to the other input of summer (41). Values of the actual slope of engine speed with respect to spark advance are calculated in slope calculating device (46), the output of which is supplied to the negative input of a summer (49). Target slope values, calculated from values stored in a memory (45), are supplied to the positive input of summer (49). The values in memory (45) are equal to, or less than, zero. The output from summer (49) is supplied to an updating device (47) which updates the correction values stored in memory (38). Each perturbation cycle comprises three engine fires. A positive perturbation is applied to the spark advance angle for the first fire and negative perturbations are applied for the remaining two fires. By using this perturbation cycle, synchronization between the engine and perturbation cycles is avoided while maintaining the perturbation frequency above the resonance frequency of the vehicle driveline under normal driving conditions.

Fuel composition containing an additive for reducing valve seat recession

Abstract: A fuel composition for use in internal combustion engines which composition comprises (A) a major amount of a fuel suitable for use in an internal combustion engine, preferably either a lead free or low-lead fuel for use in a spark ignition engine and (B) a minor amount of a composition comprising a metal salt in the form of a particulate dispersion. Examples of suitable metal salts include potassium borate, sodium borate, potassium carbonate and potassium bicarbonate.

The effect of swirl on combustion in a pancake chamber spark ignition engine: the case of constant inducted kinetic energy

Abstract: This experimental investigation is an initial step in separating the influences of swirl and inducted kinetic energy on combustion in a homogeneous charge engine. By rotation of the intake port about the axis of the intake valve, the swirl ratio was varied from zero to 2.8 while maintaining constant intake port flow, and hence constant inducted kinetic energy

Performance of a Spark Ignition Engine Fueled by Natural Gas Using Oxygen Enriched Air

Abstract: The purpose of this paper is to outline the effects of oxygen enrichment on the performance of a spark ignited single cylinder Ricardo research engine fueled with natural gas. Substituting gasoline with natural gas, under stoichiometric conditions, brings bout a decrease in power output of a dedicated gasoline engine. This reduction in power is quantified in this paper for both fuels under stoichiometric conditions as well as for different fueling rates, for natural gas.

Method and device for influencing the CO content of the exhaust gas of a spark ignition engine

Abstract: The invention relates to a method and device for influencing the CO content of the exhaust gas of a spark ignition engine with carburettor. The blow-by gases coming from the crankcase are led into the clean air chamber (13) of an air filter connected upstream of the carburettor only at partial load and full load. When idling the blow-by gases are passed through an activated charcoal filter and then filtered together with the untreated air by the air filter element (12). At partial load and full load the activated charcoal filter (22) is cleaned by a secondary air flow parallel to the air flow in the air intake pipe (11) to the filter element (12). At partial load and full load, a secondary air flow is passed by way of a valve (24) through the activated charcoal filter (22) in order to clean this in this operating state. This method and the device permit an improved CO adjustment and a lower CO content of the exhaust gas.

Effect of a spark aider fuel additive on the misfire characteristics of a spark ignition engine

Abstract: Certain fuel additives known as “spark-aiders” are known to increase early flame development rates and reduce cyclic variation in spark-ignition engines and to lead to improvements in driveability characteristics in vehicles. In this work we report the effects of such an additive—a potassium compound —on the misfire characteristics of a single cylinder engine running on iso-octane. During the tests we monitored average early flame travel time and cyclic variation using a laser-based technique for flame speed measurement and also the current-voltage characteristics of the spark. We also studied the implications of changing the strength of the spark electrically by changing the supply voltage lo the coil. The additive leads to an extension of the lean limit and the reduction in the misfire frequency when the engine operates in the misfire mode; average early flame travel time and cyclic variations as well as the spark glow voltage arc reduced and spark duration is extended. Similar results are obta...

LDA Measurement of Turbulent Flow in a Motored and Firing Spark-Ignition Engine with a Horizontal Prechamber

Abstract: To make clear the influence of a torch jet flow on the combustion process, a laser Doppler anemometer (LDA) is used to measure the mean velocity and turbulence intensity in a spark ignition engine with an unscavenged prechamber connected to a main chamber by a torch nozzle of different area sizes. The test engine is operated at a constant speed of 16.7 rps (1000 rpm), a constant volumetric efficiency of 80 +- 2% and MBT for each torch nozzle ara under firing as well as motored conditions. The LDA system is a dual beam forward scatter type, and its signals are acquired quickly and stored in a memory through a frequency tracking system.

Mixture strength measurements in the combustion chamber of SI engine via Rayleigh scattering.

Abstract: The laser Rayleigh scattering technique was applied for the space resolved measurements of vapor concentration in the concentration in the combustion chamber of a multipoint injection spark ignition engine for automotive use. The mixture formation during the intake stroke was simulated by the timed or continuous injection of freon 113 (liquid) or freon 12 (gas) into the steady flow of dust-free dry air through an intake port. The vapor concentration in the transparent combustion cylinder was determined from the intensity of scattered light which had been calibrated beforehand. The results showed that the present optical system was found to be successful in determining the local vapor concentrations for both liquid and gaseous fuel injections. It was also evident that the highly heterogeneous field of vapor concentration was established in the combustion cylinder. The vapor concentration profile was largely affected by the place for fuel injection and the intake valve lift.

Control device and method for a spark ignition engine starting from the statistical distribution of an angular deviation

Abstract: The present invention relates to a method and a device for controlling at least one parameter at least partially governing the function of a controlled spark-ignition internal combustion engine, this technique employing detection of the passage of the flame front in the combustion chamber. The method according to the invention is characterised in that, from the distribution or histogram from several of these phase difference angles corresponding to a predetermined number of cycles n, a control variable is worked out for the operation of the engine and that the parameter governing the operation of the engine is modified so that the control variable assumes a predetermined value. Application to four-stroke controlled spark-ignition engine.

Abnormal Combustion in a Two-Stroke Spark Ignited Methanol Engine

Abstract: Methanol (90% methanol + 10% gasoline) when used as a fuel in a 2-stroke spark ignition (SI) engine gave rise to abnormal combustion even at a low compression ratio. The regime of engine operation in which abnormal combustion occurs was identified and the effects of engine parameters such as mixture strength, compression ratio, ignition timing, combustion chamber geometry etc. were studied. Analysis of pressure-time histories of engine cycles when abnormal combustion occurred revealed that abnormal combustion at higher loads is similar to knocking in four-stroke engines. At light loads the nature of abnormal combustion was different. The CFR octane rating of methanol does not correlate with actual anit-knock quality in two-stroke engine combustion. Comparison with primary reference fuels indicated that the two-stroke engine has a very high severity. The hot residual gases seem to have a major role on onset of abnormal combustion.

Combustion chamber with a domed auxiliary chamber for a spark-ignition engine

Abstract: The present invention relates the technology to enhance the mixing performance of air-fuel mixture in a combustion chamber with a domed precombustion chamber for a spark-ignition engine, and aims to attain the enhanced mixing performance owing to the forcible generation of a multiplicity of small swirls by forcing the air-fuel mixture to flow into the main combustion chamber centripetally from the inside of the cylinder and then to turns three times in a step-like state with being accelerated on the way into the precombustion chamber through the connecting channel at the compression stroke. The main combustion chamber is formed by hollowing the center side portion of the piston head. The piston head is further provided with the connecting channel formed on the annular bank around the main combustion chamber so as to be faced onto by the domed precombustion chamber in the cylinder head and to be stepped up higher than the bottom of the main combustion chamber.

Visualization studies of combustion process in a spark ignition engine with a horizontal prechamber.

Abstract: To understand the combustion process in a spark ignition engine with an unscavenged horizontal prechamber, the flame propagation in both the pre- and main chamber is simultaneously visualized by a high speed camera changing the torch nozzle area, while keeping the engine speed of N≅1000rpm, the volumetric efficiency of ηv≅80% and the air-fuel ratio of A/F≅15 constant. Then an image-processing camera is used to assign the brightness of flame photograph into 16 steps of false color, and the signals of brightness are stored in floppy disk of computer through an image memory (or slot card). Such image-processed flame patterns are projected on the T.V. display and possible to be taken photograph by a still- or 8mm camera.Accordingly, it is seen that the patterns of flame propagation in the main chamber are remarkably affected by torch nozzle area and the ratio of burned portion to main chamber area (combustion area fraction) is also similar to the engine output (BMEP). Furthermore the time history of averaged brightness distribution on the center line of the main chamber is found to be in reasonable agreement with the time history of combustion gas temperature on the same line measured by an infrared pyrometer.

Combustion system for internal combustion engine and combustor used therefor

Abstract: A combustor and a combustion system for internal combustion engines. A funnel-shaped cone (9) having an opening (13) at the top portion thereof is provided in a combustion chamber (5) so as to be spaced from an igniter. An inflammable gaseous mixture is introduced into the combustion chamber (5), and it flows to the opening (13) through the cone (9). The gaseous mixture is ignited by the igniter at the opening (13), and a flame produced is radiated outside into the chamber (5) along the outer surface (22) of the cone (9). Thus, the combustion is controlled so that the most effective explosion and combustion occur automatically. If the cone (9) is provided at the tip of the igniter, i.e. a spark plug (6), the above-mentioned operation can be applied to an already manufactured spark ignition engine. In a fluidized internal combustion engine, the cone is provided in a combustion chamber, and the initial combustion is carried out on the outer surface of the cone, the secondary combustion being carried out in the interior of the cone.

LNG (liquefied natural gas) as a fuel and refrigerant for diesel powered shrimp boats

Abstract: A 3406-B Caterpillar and a 4.236 Perkins have been converted from their standard diesel configuration to dual-fuel engines. These engines operate using an aspirated charge of natural gas and a pilot charge of diesel fuel. The pilot is injected for combustion initiation, performing the same task as a spark plug in a spark ignition engine. Natural gas supplies 80% of the total heat addition at full load for both engines. The diesel fuel provides ignition, performs the function of idling the engine, and acts as a coolant for the injector tips. The diesel pilot setting remains constant throughout the operating range and provides a regular repeatable idle for the engine during no-load operation. A shrimp boat is being used to evaluate the dual-fuel system. The vessel normally carries 16000 1 of diesel fuel giving it a trip length of 14-21 days. To operate on natural gas with similar trip length requires liquification and cryogenic storage at -163/sup 0/C. This type of storage provides the necessary energy density needed for on board fuel storage. A 22 m shrimp boat will carry approximately 17000 1 of LNG in insulated tanks. Urethane insulation is used as both an insulator against heat leak andmore » as a partial tank support structure.« less

Method for improving the exhaust performance of spark ignition engines

Abstract: In a method for improving the exhaust performance of spark ignition engines, the output signal of a lambda probe, arranged in the exhaust port of the spark ignition engine, being fed to a regulator and the output voltage of the regulator forming a control variable for regulating the fuel-air ratio, after a transition from idling to partial load, the control variable is kept constant at a predetermined value for a first predetermined period. Thereafter the control variable is adjusted towards an increase of the air-fuel ratio for a second predetermined period, irrespective of the output signal of the lambda probe, whereupon the control is resumed.