Showing papers on "Compression ratio published in 1999"

Premixed charge compression ignition engine with optimal combustion control

Abstract: A premixed charge compression ignition engine, and a control system, is provided which effectively initiates combustion by compression ignition and maintains stable combustion while achieving extremely low nitrous oxide emissions, good overall efficiency and acceptable combustion noise and cylinder pressures. The present engine and control system effectively controls the combustion history, that is, the time at which combustion occurs, the rate of combustion, the duration of combustion and/or the completeness of combustion, by controlling the operation of certain control variables providing temperature control, pressure control, control of the mixture's autoignition properties and equivalence ratio control. The combustion control system provides active feedback control of the combustion event and includes a sensor, e.g. pressure sensor, for detecting an engine operating condition indicative of the combustion history, e.g. the start of combustion, and generating an associated engine operating condition signal. A processor receives the signal and generates control signals based on the engine operating condition signal for controlling various engine components to control the temperature, pressure, equivalence ratio and/or autoignition properties so as to variably control the combustion history of future combustion events to achieve stable, low emission combustion in each cylinder and combustion balancing between the cylinders.

A numerical study of a free piston ic engine operating on homogeneous charge compression ignition combustion

Abstract: A free piston, internal combustion (IC) engine, operating at high compression ratio (~30:1) and low equivalence ratio (φ~0.35), and utilizing homogeneous charge compression ignition combustion, has been proposed by Sandia National Laboratories as a means of significantly improving the IC engine’s cycle thermal efficiency and exhaust emissions. A zero-dimensional, thermodynamic model with detailed chemical kinetics, and empirical scavenging, heat transfer, and friction component models has been used to analyze the steady-state operating characteristics of this engine. The cycle simulations using hydrogen as the fuel, have indicated the critical factors affecting the engine’s performance, and suggest the limits of improvement possible relative to conventional IC engine technologies.

A Compression Algorithm for DNA Sequences and Its Applications in Genome Comparison.

Abstract: We present a lossless compression algorithm, GenCompress, for genetic sequences, based on searching for approximate repeats Our algorithm achieves the best compression ratios for benchmark DNA sequences Significantly better compression results show that the approximate repeats are one of the main hidden regularities in DNA sequences We then describe a theory of measuring the relatedness between two DNA sequences Using our algorithm, we present strong experimental support for this theory, and demonstrate its application in comparing genomes and constructing evolutionary trees

Cylinder pressure based optimization control for compression ignition engines

Abstract: The performance of a compression ignition internal combustion engine is improved by optimizing a cylinder pressure-dependent parameter on a full time, full range basis using in-cylinder pressure measurements to determine the actual value of the parameter to be optimized. The basic procedure is to determine the desired or optimum value of the parameter, determine the actual value of the parameter or a related parameter, and then adjusting an engine operating characteristic such as air/fuel ratio to maintain the controlled parameter at its optimum value. The preferred parameter is a cylinder pressure ratio (CPR) obtained by dividing first and second values of cylinder pressure, and sensed at different points in a thermodynamic cycle, by one another. The sensed values are preferably a first value Po, obtained during the compression stroke, and a second value Pa, obtained after combustion is complete. Direct in-cylinder pressure measurements can also be used for other purposes such as knock detection, determination of maximum cylinder pressure (MCP), and engine controls dependent thereon.

Combustion control device for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To prevent generation of knocking by performing spark ignition combustion at a low compression ratio side of a switching region and performing self ignition combustion at a high compression ratio side, at the time of switching combustion, in a device in which the self ignition combustion is performed with a high compression ratio at the time of low load operation and the spark ignition combustion is performed with a low compression ratio at the time of high load operation. SOLUTION: At the time of high load operation, an opening timing of an intake valve 6 is set earlier than a top dead center, a closing timing of an exhaust valve 7 is set later than the top dead center, and the intake and exhaust valves 6, 7 are overlapped with each other. Simultaneously, the closing timing of the intake valve 6 is set later than a bottom dead center to set to a low compression ratio, and spark ignition operation is carried out. On the other hand, at the time of low load operation a closing timing of an exhaust valve is set earlier than the top dead center an opening timing of the intake valve 6 is set later than the top dead center, a minas over lapping is set, and self ignition operation is carried out while aiming at inside EGR. In an intermediate compression ratio cycle at the switching region between self ignition and spark ignition combustion, spark ignition combustion is performed at a low compression ratio side of a switching region, self ignition combustion is performed at a high compression ratio side so as to suppress generation of knocking. COPYRIGHT: (C)2000,JPO

Compression Ratio Effect on Methane HCCI Combustion

Abstract: The authors have used the HCT (hydrodynamics, chemistry, and transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, burn duration, NO{sub X}production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. intake pressure) with 14:1, 16:1 and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation, which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either two-stroke or four-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50 percent andmore » NO{sub X}levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.« less

Mean-shape vector quantizer for ECG signal compression

Abstract: A direct waveform mean-shape vector quantization (MSVQ) is proposed here as an alternative for electrocardiographic (ECG) signal compression. In this method, the mean values for short ECG signal segments are quantized as scalars and compression of the single-lead ECG by average beat substraction and residual differencing their waveshapes coded through a vector quantizer. An entropy encoder is applied to both, mean and vector codes, to further increase compression without degrading the quality of the reconstructed signals. In this paper, the fundamentals of MSVQ are discussed, along with various parameters specifications such as duration of signal segments, the wordlength of the mean-value quantization and the size of the vector codebook. The method is assessed through percent-residual-difference measures on reconstructed signals, whereas its computational complexity is analyzed considering its real-time implementation. As a result, MSVQ has been found to be an efficient compression method, leading to high compression ratios (CRs) while maintaining a low level of waveform distortion and, consequently, preserving the main clinically interesting features of the ECG signals. CRs in excess of 39 have been achieved, yielding low data rates of about 140 bps. This compression factor makes this technique especially attractive in the area of ambulatory monitoring.

Study of combustion characteristics of a compression ignition engine fuelled with dimethyl ether

Abstract: This paper presents the combustion characteristics of a light-duty direct-injection diesel engine operating on dimethyl ether (DME). The indicated pressure diagrams and injector needle lifts are recorded and the combustion characteristics are demonstrated and compared with those of an engine operated on diesel fuel. The experimental and calculated results show that the DME engine has a longer delay of injection and duration of injection, a lower maximum cylinder pressure and rate of pressure rise, as well as a shorter ignition delay compared with those of a diesel engine. The DME engine has a low mechanical load and combustion noise, a fast rate of diffusion combustion and a shorter combustion duration than that of a diesel engine. It has the ideal pattern of compression ignition engine heat release.

Runlength compression techniques for FPGA configurations

Abstract: The time it takes to reconfigure FPGAs can be a significant overhead for reconfigurable computing. In this paper we develop new compression algorithms for FPGA configurations that can significantly reduce this overhead. By using runlength and other compression techniques, files can be compressed by a factor of 3.6 times. Bus transfer and decompression hardware are also discussed. This results in a single compression methodology which achieves higher compression ratios than existing algorithms in an off-line version, as well as a somewhat lower quality compression approach which is suitable for on-line use in dynamic circuit generation and other mapping-time critical situations.

Fuel injection control system for direct injection-spark ignition engine

Abstract: A fuel injection control system for a direct injection-spark ignition engine determines an injection pulse width corresponding to a given quantity of fuel with which an injector is kept open, controls the injector to spray a given quantity of fuel in a compression stroke while the engine operates in a zone of lower engine loads specified for lean stratified charge combustion so that the fuel is stratified around an ignition plug to cause lean stratified charge combustion so as thereby to provide an air-fuel ratio greater than a stoichiometric air-fuel ratio, executes fuel injection feedback control to control a quantity of fuel injection based on an air-fuel ratio detected by an oxygen sensor, causes the injector to spray a given quantity of fuel through a plurality of intake stroke split injection in a specified engine operating zone in which the fuel injection feedback control is performed to maintain at least a stoichiometric air-fuel ratio while the engine operates with lower loads, learns a fuel injection quantity characteristic of the injector with respect to injection pulse width for each intake stroke split injection based on a value controlled by the fuel injection feedback control during execution of the intake stroke split injection to determine a leaning correction value, and makes the learning correction value reflect on the control of the quantity of fuel in a minute injection zone specified within the specified engine operating zone for the lean stratified charge combustion.

Engine combustion control device

Abstract: An engine combustion control device which provides, for improvement in an engine fuel efficiency and an emission control, an optimum combustion by detecting a combustion pressure in a cylinder and controlling an exhaust reflux rate, an ignition timing and a fuel injection timing or an intake-stroke fuel injection rate, which comprises a cylinder pressure detection means for detecting a cylinder inner pressure produced by an engine combustion and a means for calculating a heat release rate of a cylinder with respect to a crankshaft angle based on an output from the cylinder pressure detection means, and which controls fuel-related controlled variables such as an ignition timing, a fuel injection timing and an EGR controlled variable so that a cylinder combustion condition pattern determined by the heat release rate calculation means agrees with a preset waveform pattern.

Control system and control method for diesel engine

Abstract: A control system for a compression ignition type diesel engine includes an operating state detecting unit for detecting the operating state of the diesel engine. A combustion mode selecting unit selects, in correspondence with the output of the operating state detecting unit, a first combustion mode, wherein fuel injection is carried out in the first half of the compression stroke, or a second combustion mode, wherein fuel injection is carried out at around compression top dead center. An effective compression ratio varying unit varies the effective compression ratio of the diesel engine and a control unit controls the effective compression ratio varying unit to lower the effective compression ratio when the first combustion mode is selected by the combustion mode selecting unit compared to when the second combustion mode is selected. When the first combustion mode is selected by the combustion mode selecting unit, by fuel injection being carried out in the first half of the compression stroke and the effective compression ratio being lowered so that compression ignition occurs at around compression top dead center, a uniform highly diffuse premix combustion can be realized. When the second combustion mode is selected by the combustion mode selecting unit, by fuel injection being carried out at compression top dead center and ignition occurring at around compression top dead center substantially simultaneously with fuel injection, without the effective compression ratio being lowered, diffusion combustion is realized.

Intelligent method for computer file compression

Abstract: The present invention relates to an easy-to-use intelligent method for compressing computer files. In this method, a computer file containing different information types, such as text, image and sound, is automatically compressed by a computer, using suitable lossy or lossless codes. Both appropriate compression ratio and compression quality can be obtained. The present invention also relates to a method for decompressing a compressed file.

Method for operating a four-stroke internal combustion engine

Abstract: The present invention relates to a method for operating a four-stroke internal combustion engine in which a homogeneous and lean air-fuel mixture is burnt by compression ignition. According to this method, a controllable inlet member is used for modifying the fuel-air ratio in the combustion chamber. In order to obtain an adaptation to the modified combustion cycles which is as quick as possible, each combustion sequence is measured while the shutting moment of the combustion-chamber inlet member is adjusted for the next cycle according to a signal resulting from the corresponding measurement.

Intake control device for engine

Abstract: PROBLEM TO BE SOLVED: To improve fuel consumption and exhaust emission by increasing maximum torque when low octane number fuel is used, in an engine with a high compression ratio. SOLUTION: When high octane fuel is used, valve timing (closing timing of an intake valve) is controlled, so as to sufficiently increase air quantity and a compression ratio as in a conventional way, since a knocking limit is large and to control ignition timing shown at point A. When regular fuel is used, maximum torque can be increased and also an exhaust temperature is decreased by controlling valve timing (closing timing of the intake valve) so as to decreased air quantity and the compression ratio and control ignition timing shown at point B which is advanced as compared with the conventional ignition timing, and thereby also on rich control of an air-fuel mixture ratio becomes unnecessary and fuel consumption and exhaust emission are improved. COPYRIGHT: (C)2001,JPO

Engine control system and control method

Abstract: PROBLEM TO BE SOLVED: To reconcile ignitability and torque controllability by sequentially performing a first injection for controlling the initial combustion speed before ignition and performing a second injection for controlling engine torque to increase the engine torque and enlarge a second injection ratio in a cylinder injection engine having a compression ignition mode. SOLUTION: By a controller 12, a fuel injection quantity is calculated according to a target engine torque and an engine rotating speed, and an intake compression injection ration (first and second injection ratio) is decided to control the intake injection and compression injection from a fuel injection valve 1. When the torque fluctuation is an allowable value or more, the intake injection ratio is increased to promote the generation of a radical. When knocking is caused, the intake injection ratio is decreased, and variable valves 40, 41 are controlled through a variable valve driving circuit 30 to reach a target EGR, thereby controlling the internal EGR. External EGR is used for a portion unsatisfied by the internal EGR.

Client preferences for compression threshold in single-channel wide dynamic range compression hearing aids.

Abstract: Objective Compression in hearing aids can be applied with low compression ratios over a wide range of input levels, but reverts to linear amplification below the compression threshold (CT). In this study, we aimed to determine which of two CTs was preferred by subjects as they used their hearing aids in their own environments, and whether they would prefer to have no low ratio compression at all. Design Subjects were fitted with a multimemory hearing aid incorporating input controlled compression with a 2:1 compression ratio and output controlled compression limiting. The two memories contained identical programs except that they differed in CT. Sixteen mild to moderately sensorineurally hearing-impaired subjects compared low (approximately 40 dB SPL) and moderate (approximately 65 dB SPL) CTs over 2 mo of field trials using hand held remote controls to switch between the alternatives. In a third month's trial, the preferred option (which also included output controlled compression limiting) was compared with compression limiting alone. Results The higher CT was preferred by 14 of the subjects. The combination of input compression and output compression limiting was preferred to compression limiting alone by 14 of the subjects. Conclusions Several real world advantages of frequency independent 2:1 compression with a CT of about 65 dB SPL were demonstrated over linear amplification. Extending the compression to much lower input levels appears to carry more disadvantages than advantages, at least for clients with mild and moderate hearing losses, when fitted with single-channel compression aids with a 2:1 compression ratio.

Turbocharged gas-combustion engine equipped with motor generator

Abstract: Disclosed a gas-combustion engine burning fuel of natural gas, which is provided with a turbocharger(15) having a motor generator(18) and operated on the Miller cycle that may control adequately actual compression ratios by regulating the timing for opening and closing intake valves(11). The gas-combustion engine has intake-valve lift controllers(30) for altering the timing for opening and closing intake valves(11) at intake ports(7,9) to thereby vary actual compression ratios. The intake-valve lift controllers(30) each, when the temperatures of the intake air and/or the combustion chamber walls are below a design temperature preselected, control the timing for closure of the associated intake valve(11) so as to block the associated intake port(7,9) near the bottom dead center of the compression phase. In contrast, when the temperature of the combustion chamber walls is above the design temperature preselected, the intake-valve lift controllers(30) each delay the timing for closure of the intake valve(11) at the intake port(7,9) so as to permit a part of the intake air to flow backwards to the intake port(7,9). In a design of two intake valves (11) being provided per each combustion chamber(1,2), the intake-valve lift controllers(30) may operate so as to alter the duration for opening any one of the two intake valves. A controller unit(50) regulates the timings for opening and closure of the intake valves (11), in response to combustion chamber wall temperatures, boosting pressures, engine power and fuel flow rates supplied into the sub-combustion chambers(2), operating conditions of a motor generator(18) in a turbocharger(15) and the intake-valve lift controllers (30).

The Wavelet Stream – Progressive Transmission of Compressed Light Field Data

Abstract: In this paper we describe the compression of light field data using 4D nonstandard wavelet decomposition. For progressive transmission, storage, and rendering of the compressed light field data the new wavelet stream data structure is introduced. The wavelet coefficients are ordered in decreasing importance, encoding the position of the non discarded coefficients using significance maps. Compared to the vector quantization compression method, the wavelet stream achieves up to 3 times higher compression ratios while producing the same error during reconstruction of the light field data. Despite of the high compression of the data, reasonable frame rates during light field rendering are achieved. CR Categories: I.3.6 [Computer Graphics]: Methodology and Techniques—Graphics data structures and data types E.4 [Coding and Information Theory]: Data compaction and compression

Fast compression and transmission of seismic data

Abstract: Apparatus and method for performing fast compression and decompression of seismic data. An adaptive transform (124) with selectable mathematical basis is applied to an initial data set to obtain a set of transformed coefficients, the transform factorizing an effective symmetric or non-symmetric biorthogonal filter of size (u, v) into a number m of elementary (3, 1) biorthogonal filters which are applied to the data set in selected directions without requiring transposition of the data set. The coefficients are encoded (126) using non-uniform scalar quantization and run-length coding followed by adaptive coding of resulting threshold coefficients. The transform and encoding steps are repeated (128) using a new mathematical basis for each iteration to obtain a compressed data set at a desired compression rate. Exact compression ratios can be obtained (158), allowing evaluation of the data in the compressed domain as well as transparent, on-the-fly decompression at computer network data transfer rates.

Throttle control system for a stratified charge internal combustion engine

Abstract: An engine control scheme determines the appropriate and desired magnitude of scavenging air flow for a two stroke engine as a function of both load and engine speed. The desired air flow is determined, as a function of engine load and engine speed, to achieve an optimal magnitude of emissions within the exhaust stream and to also optimize a reverse thrust capabilities of the marine propulsion system.

Feedback control for hybrid compression

Abstract: A closed loop feedback system adaptively controls the compression ratio in a Raster Image Processor. The image content is analyzed in real time, and rasterized bitmap is compressed to a sufficient degree to fit into the available frame buffer. This compression may be done by a variety of algorithms depending on image content. The compression ratio is adjusted on the fly by changing the method of compression, more aggressive or selective quantizing of the image, or by a decimation of parts of the image. The algorithms show will execute very efficiently on a Texas Instruments TMS320C82 multiprocessing DSP. Several methods of implementation on the TMS320C82 are shown.

Internal combustion engine with adjustable compression ratio and knock control

Abstract: A reciprocating internal combustion engine includes a variable compression ratio system for adjusting the compression ratio of an engine in a first compression range located about a first predetermined compression ratio in the event that the engine is operating at a first predetermined load range, with the variable compression ratio adding a fixed clearance volume to the volume of the combustion chamber in the event that the engine is operating in a knocking condition beyond the range of the first compression range.

Constant bitrate algorithm for block based image compression

Abstract: A method of compressing image data to achieve a desired compression ratio corresponding to a desired file size. A target compression ratio (the ratio of uncompressed image data to compressed image data) is specified. A subset of the image data is selected. A first quantization parameter is selected, the subset of the image data is compressed using that quantization parameter, and the resulting compression ratio is calculated. A second quantization parameter is then selected, the subset of the image data is compressed using the second quantization parameter, and the resulting compression ratio is calculated. A target quantization parameter corresponding to the target compression ratio is calculated by interpolating between the first quantization parameter and the second quantization parameter and the corresponding compression ratios. The target quantization parameter is applied to the entire set of image data to compress the image data at approximately the target compression ratio. As a result, the size of the file containing the compressed data is approximately the same as the target file size. The present invention allows rate control in less computation time than it takes to compress the image; the time to estimate the target quantization parameter can be done in less computation time than needed to compress the full image.

Fuel control unit and fuel injection control method for multi-cylinder engine

Abstract: A fuel control unit and a fuel injection control method for a multi-cylinder engine adjust the pulse width of asynchronous injection so as to set the air-fuel ratio of a fuel-air mixture in a first cylinder to 17 or more but under 21 if it is determined according to an engine speed (Ne) that an engine is in an idling mode and if it is determined according to the opening of a throttle valve that a condition for starting the acceleration of the engine has been satisfied. The foregoing first cylinder is the cylinder in which compression pressure increases first following the determination described above.

Starting device for direct cylinder injection type internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To provide a starting device for a direct cylinder injection type internal combustion engine capable of promptly completing starting, and preventing problems caused by self-ignition or rapid combustion in advance by certainly conducting normal spark ignition at the time of starting. SOLUTION: Piston positions of a compression stroke cylinder and an suction stroke cylinder of a stopped internal combustion engine are detected, and a fuel injection amount and injection timing is determined in spark ignition area (point A) so as to avoid a self-ignition area, on the basis of a map corresponding to the piston positions. Fuel injection and ignition are conducted to the compression stroke cylinder and the suction stroke cylinder to promptly causing explosion for the first time, and spark ignition is normally materialized by injecting fuel based on the determine fuel injection amount and injection timing.

Method of controlling the process of combustion in an internal combustion engine, and engine with means for varying the effective compression ratio of the cylinders

Abstract: Four-stroke internal combustion engine with variable geometric compression ratio, electrically operated inlet valves and means for supplying a homogeneous fuel/air mixture to the engine cylinders. The inlet valves (9) and the compression ratio are controlled by a control unit (15), so that the fuel/air mixture, within a lower engine rpm range, is compressed to self-ignition.

Variable rate power disturbance signal compression using embedded zerotree wavelet transform coding

Abstract: The embedded zerotree wavelet transform (EZWT) coding scheme is utilized to compress transient power disturbance signals The results of the compression and the reconstruction by this coding scheme are presented and compared with previous work A principal adventure of this coding scheme lies in the fact that it provides for variable compression ratios