Showing papers on "Compression ratio published in 1997"

Experimental investigation on varying the compression ratio of si engine working under different ethanol–gasoline fuel blends

Abstract: Using different ethanol–gasoline fuel blends, a VARICOMP engine was used to study the effect of varying the compression ratio on SI engine performance. The performance tests were carried out using different percentages of ethanol in gasoline fuel, up to 40%, under variable compression ratio conditions. The results show that the engine indicated power improves with the percentage addition of the ethanol in the fuel blend. The maximum improvement occurs at 10% ethanol–90% gasoline fuel blend. © 1997 by John Wiley & Sons, Ltd.

Apparatus and method for hybrid compression of raster data

Abstract: From a raster page, patches of connected pixels of the same color are identified. Patches of at least a predetermined size, typically corresponding to text or line art objects, are subjected to a lossless compression. Patches below the predetermined size, typically corresponding to image or photo objects, are substantially subjected to a lossy compression. The patch predetermined size controls the mix of lossless and lossy compression procedures. Optimum compression is achieved by maximizing the lossless compression while attaining a targeted compression ratio. Various features include efficient recognition and encoding of patches, refined treatment of the boundaries between the lossless- and the lossy-compressed pixels, adaptive compression ratio control, and fail-safe compression provisions.

Method and apparatus for performing data compression

Abstract: A method and apparatus are disclosed for performing data compression on raw uncompressed data. The method develops a semi-adaptive modeler that sub-divides the length of an input data file into blocks of fixed size. The blocks are then sub-divided into sub-blocks in which the frequencies of the symbols are mapped to occupy the whole frequency space. The modeler is then used to develop a reduced complexity implementation of arithmetic coding, whereby, the time consuming divide operation used in computing the symbols' true probabilities is replaced by a simple shift operation. The reduced complexity arithmetic coder is referred to as approximate arithmetic coder. The modeler and the approximate arithmetic coder are then used in a multi-step data compression system that employs a ZL coder. The multi-step method results in high efficiency data compression systems that are ideal for real time operations and are better suited for network communications or data storage systems. The method overcomes many of the difficulties found in the prior art and generally achieves better compression ratios.

Development of a natural gas spark ignition engine for optimum performance

Abstract: A 4 litre displacement, six cylinder, fuel injected petrol engine was modified to natural gas (NG) fuelling. Experimental investigation was carried out with various mixture controls and compression ratios over a wide range of operating conditions. As a strategy for combustion chamber shape modification, the compression ratio was raised with simultaneous enhancement of in-cylinder turbulence through squish motion. A fast burning chamber for the combustion of lean mixtures of natural gas and air was developed. Brake thermal efficiency in excess of 40 per cent and brake torque in excess of the peak base torque with petrol were achieved. The research provides the foundation for the implementation of NG cars that will emit only about 65 per cent of the carbon dioxide (CO2) of their petrol engine counterparts, with the prospect of extending the limited range of NG cars by up to one-third and producing low hydrocarbon (HC) and nitrogen oxide (NOx) emissions.

Apparatus and method for controlling homogeneous charge compression ignition combustion in diesel engines

Abstract: A closed-loop control system controls the timing and amount of water injected into a combustion chamber of a homogeneous charge compression ignition diesel engine to regulate the start of combustion during the compression stroke or early in the expansion stroke of each combustion cycle. A sensor is used to detect the start of combustion and deliver a signal to an engine control unit to adjust water injection timing and quantity, on a cycle-by-cycle basis, to obtain the desired start of combustion during each compression stroke of the engine. The present invention effectively overcomes the problem of repeatable and accurate control of the start of combustion in diesel engines operating in a homogeneous charge compression ignition mode.

System and method for multirecord compression in a relational database

Abstract: The invention is a system and method for database compression which creates partial indexing into compressed sub table blocks of databases. Table rows with the same or related indexing parameters are grouped as "sub-table blocks" and are stored as compressed binary objects, with the indexing fields stored in the same row, external to the binary block. The binary object expands to multiple database rows when accessed via the sub table block interface, thus forming a hierarchical, pre-joined database organization. Mechanisms are provided for creating, accessing, and manipulating the data blocks, and a date-based versioning mechanism. The compression employed is the known Vdelta package, which operates at a byte level to provide a useful compromise between speed and compression efficiency, even for relative short compression blocks. In realistic tests, the I/O time gained through compression results in a time saving which exceeds the processing penalty. The overall compression ratio is data dependent, but in a realistic test it averages about 4.

Multi-cylinder four stroke direct injection spark ignition engine

Abstract: An engine is started by identifying a combustion chamber having a predetermined volume of air therein and being in a position past top dead center, injecting fuel into the combustion chamber, thereby providing a combustible mixture, and, igniting the mixture.

Method and apparatus for compression and decompression of still and motion video data based on adaptive pixel-by-pixel processing and adaptive variable length coding

Abstract: A method and apparatus for pixel-by-pixel motion and/or still video data compression and decompression. Each pixel may be encoded as static, new, or direcionally estimated. Directionally estimated pixels are encoded with a value corresponding to a direction in a reduced set of substantially unique directions, wherein each direction may correspond to one or a combination of pixels. Directionally estimated pixels are further encoded using an adaptive variable length code (VLC), while static pixels and new pixels are encoded using run-lenth (RL) coding and delta coding techniques, respectively. Performance parameters, such as compression ratio, quality, etc., may be monitored to dynamically and adaptively update compression thresholds. Pixel processing may be performed in a plurality of directions to improve performance.

Cylinder pressure based air-fuel ratio and engine control

Abstract: A system and method for controlling an air-fuel ratio of an internal combustion engine using a ratio of cylinder pressures measured within at least one cylinder The air-fuel ratio control system includes an electronic control module (ECM) which computes a measured cylinder pressure ratio of the cylinder pressure measured at a predetermined crank angle before top dead center and the cylinder pressure measured at a predetermined crank angle after top dead center The measured cylinder pressure ratio is compared with an optimal cylinder pressure ratio Based upon the results of this comparison, the ECM then determines an adjusted air-fuel ratio which would modify the measured pressure ratio to equal the optimal pressure ratio This system controls the air-fuel ratio by measuring the quality of combustion without the need to measure the amount of air or fuel actually delivered to the engine The measured pressure ratio corresponds to an excess air ratio of the internal combustion engine at those operating conditions, wherein a measured excess air ratio of the engine may be obtained from the computed pressure ratio The measured excess air ratio may be compared with an optimal excess air ratio for the specific engine operating conditions currently being sensed, wherein the ECM then determines the adjusted air-fuel ratio which would modify the measured excess air ratio to equal the stored optimal excess air ratio

Apparatus for controlling the air-fuel ratio in an internal combustion engine

Abstract: An apparatus for controlling the air-fuel ratio in an internal combustion engine, which quickly responds to a deviation between the actual air-fuel ratio and the target air-fuel ratio in the engine and results in immediate purification of the exhaust gas discharged from the engine.

Resolution-variable adaptive picture compression

Abstract: A resolution-variable adaptive picture compression method and the apparatus therefor varies the resolution of the currently compressed picture while adjusting its frame structure which is compressed according to the picture's condition, to thereby enhance picture quality with respect to the compression ratio.

Air-fuel ratio control system having function of after-start lean-burn control for internal combustion engines

Abstract: There is provided an air-fuel ratio control system for an internal combustion engine installed on an automotive vehicle. The control system controls the air-fuel ratio of a mixture supplied to the engine to a value leaner than a stoichiometric air-fuel ratio immediately after the start of the engine. Operating conditions of the engine and/or operating conditions of the automotive vehicle is detected. Starting of the vehicle is predicted based on the detected operating conditions of the engine and/or the detected operating conditions of the automotive vehicle. The air-fuel ratio of the mixture supplied to the engine is changed to a richer value than the leaner value when the starting of the vehicle is predicted.

Method and apparatus for data compression

Abstract: A method and apparatus for compression of data using a technique for quantization and encoding referred to as Mapping through Interval Refinement (MIR). The method uses the size of the original data set together with a target compression ratio to determine the size of a compressed representative of the original data. The data elements after de-correlation are effectively sorted in decreasing order of significance and then written to an output data set using an efficient encoding method which incrementally refines the precision of elements already output. The output process continues until the target compressed file size is reached. Decompression of the compressed data is accomplished by reading in the sorted elements and restoring them to their locations in the data set, and to the precisions saved in the compression process. The method and apparatus employing it are applicable to time series data as well as multi-dimensional data such as color contone images used in the graphic arts electronic pre-press field.

Temperature control system for emission device coupled to direct injection engines

Abstract: A direct injection spark ignition engine is disclosed in which fuel is injected during a compression stroke of each combustion chamber for stratified mode operation. Additional fuel is injected into each combustion chamber during its exhaust stroke while operating in the stratified mode to provide an exotherm for heating the NOx trap in response to a low temperature indication. When total fuel injected into the combustion chamber exceeds a predetermined value, engine operation is switched from the stratified to the homogeneous mode.

Bubble detection and recovery in a liquid pumping system

Abstract: A serial, dual piston high pressure fluid pumping system that overcomes the difficulties of gas in the fluid stream without the need for added mechanical valves or fluid paths. A bubble detection and recovery mechanism monitors compression and decompression volumes of the serially configured dual pump head pump, and the overall system delivery pressure. Bubble detection is effected by sensing a ratio of compression to decompression volume and determining if the ratio exceeds an empirical threshold that suggests the ratio of gas-to-liquid content of eluent or fluid in the system is beyond the pump's ability to accurately meter a solvent mixture. The magnitude of the ratio of compression to decompression volume indicates that either the intake stroke has a bubble or that the eluent has a higher-than-normal gas content. Once a bubble has been detected, recovery is effected by forcing the pump into a very high stroke volume with the compression and decompression stroke limits constrained to obtain the largest delivery stroke compression ratio that will expel a bubble or solvent that has detrimental quantities of gas.

3D-DCT quantization as a compression technique for video sequences

Abstract: The paper proposes a novel method to generate quantization values for 3D-DCT coefficients. Such quantization values are important as they would affect significantly the extent of the compression achieved by any 3D-DCT based video compression scheme. It was found that the distribution of the dominant AC coefficients spread along the major axes of the 3D-DCT cube. The coefficient distribution can be modeled by dividing the cube into two regions, one for most of the significant coefficients and the other for the high frequency coefficients which can be discarded. The quantization values are computed by using an exponential function. The same function is also used to determine a scan order of the 3D-DCT coefficients, which is better than a three dimensional zig-zag scan method in general. Experimental results show that the proposed method can produce good visual quality videos and can achieve an attractive compression ratio of 16:1 by quantization alone.

Hybrid supercharged engine

Abstract: A hybrid supercharged engine which comprises a turbo-charger TC having a maximum capacity at a higher speed than a maximum torque rotational speed of the engine, and a positive displacement supercharger SC installed in series with the turbo-charger TC, the SC being controlled to have a constant air charging amount irrespective of an engine speed for two-stage supercharging. The hybrid supercharged engine can provide a BMEP two or more times that of a TC supercharged engine as well as a low BSFC. Further, supercharging is effected mainly by the SC at low speeds to increase an air charging amount supplied to the engine for acceleration of the TC, so that generation of turbo lag can be suppressed to thereby display a performance at a steady running even at the time of rapid accelerating from low speeds. Also, the SC effectively functions at start-up to increase a compression pressure and temperature of the engine to facilitate start-up of a high-ratio output engine which inevitably has a low compression ratio. Accordingly, it is possible to make an engine small-sized, lightweight and inexpensive and to reduce NOx emissions without sacrifice in reliability of the engine.

Internal combustion engine with constant-volume independent combustion chamber

Abstract: Procedure and devices relating to a cyclical internal combustion engine with a constant-volume independent combustion chamber in which, for each working cylinder or element, combustion chamber (1), combustion chamber (2) and expansion chamber (4) are made up of three separate, entirely independent parts. The cycle of the compression chamber is advanced in relation to that of the expansion chamber, in order to allow for lengthy combustion periods. The compressed carbonized mixture is introduced into combustion chamber (2) once its flap (6) has opened, shutting off a conduit (5) between the compression chamber and the expansion chamber; once flap (6) is closed, combustion takes place in the constant-volume independent chamber, which is isolated for an extended period. When the volume of expansion chamber (4) is at its lowest level, flap (8) is opened, shutting off conduit (7) between the combustion chamber and the expansion chamber, and the gases burned under high pressure expand, pushing back piston (15) and creating the working cycle. All engine applications are concerned.

Active driveline damping

Abstract: Internal combustion engine torque control for damping undesirable engine speed variation measures the variation as a high frequency engine speed variation at a known engine operating angle and, for each cylinder combustion event while the variation is present, calculates a phase-compensated desired torque change to dampen the engine speed variation by projecting the engine speed variation phase at the known engine operating angle to the phase at a next combustion event, and to calculate an opposing cylinder output torque change to dampen the engine speed variation phase at that next combustion event. The torque change is then carried out through ignition timing variation at the combustion event or through variation in the amount of fuel delivered for ignition at the combustion event.

Modeling of homogeneous charge compression ignition (HCCI) of methane

Abstract: The operation of piston engines on a compression ignition cycle using a lean, homogeneous charge has many potential attractive features. These include the potential for extremely low NO{sub x} and particulate emissions while maintaining high thermal efficiency and not requiring the expensive high pressure injection system of the typical modem diesel engine. Using the HCT chemical kinetics code to simulate autoignition of methane-air mixtures, we have explored the ignition timing, burn duration, NO{sub x} production, indicated efficiency and power output of an engine with a compression ratio of 15:1 at 1200 and 2400 rpm. HCT was modified to include the effects of heat transfer. This study used a single control volume reaction zone that varies as a function of crank angle. The ignition process is controlled by varying the intake equivalence ratio and varying the residual gas trapping (RGT). RGT is internal exhaust gas recirculation which recycles both heat and combustion product species. It is accomplished by varying the timing of the exhaust valve closure. Inlet manifold temperature was held constant at 330 Kelvins. Results show that there is a narrow range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated more » efficiency above 50% and NO{sub x} levels below 100 ppm. « less

Scroll gas compressor having asymmetric bypass holes

Abstract: It is an object of the present invention to improve the efficiency of a scroll gas compressor by operating a bypass at a proper compression ratio. To achieve the object, the present invention is constituted so that at least one pair of bypass holes whose one ends are opened in a compression chamber currently performing compression nearby a discharge vent and whose other ends communicate with a discharge chamber are asymmetrically arranged on a panel board. This structure makes it possible to improve the efficiency of the compressor by operating the bypass at an optimum compression ratio even if a difference is observed between pressure rises of a pair of symmetric compressed spaces under the compression process.

Homogeneous charge compression ignition engine with optimal combustion control

Abstract: An improved HCCI engine and control scheme is provided which produces stable HCCI combustion while optimally minimizing emissions and maximizing efficiency. In the present invention, the fuel/air mixture is thoroughly mixed to form a very lean homogeneous mixture, or is mixed in a manner to form a desired air/fuel stratification, to ensure relatively even, low flame temperatures which result in extremely low NOx emissions. The control system senses the start of combustion, the combustion rate and/or the combustion duration and, based on the sensed condition, actively controls the temperature, pressure, equivalence ratio and autoignition properties to continuously maintain optimum combustion.

Apparatus and method for controlling combustion in internal combustion engines

Abstract: An engine that selects the combustion mode from a number of combustion modes. The engine includes a fuel supplying device that supplies fuel directly into its cylinders. A detecting device detects the operating condition of the engine. A computing device computes the actual engine load based on the detected operating conditions. An apparatus for controlling combustion controls the fuel supplying device by selecting the combustion mode in accordance with the actual engine load.

A very fast algorithm for RAM compression

Abstract: Compressed virtual memory systems have been suggested, and in some cases implemented, to improve the effectiveness of use of physical RAM. However, most proposals and/or implementations are based on adaptive compression algorithms which achieve good compression ratios, but are slow compared to a local disk. Hence, they can only give some advantage with very slow (e.g. network-mounted) swap devices. In this paper we show that in many cases memory pages contain highly compressible data, with a very large amount of zero-valued elements. This suggests the replacement of slow, adaptive compression algorithms with very fast ones based on static Huffman codes.We present one such algorithm which, paired with a careful layout of the data, is able to compress 4KB pages at 40MB/s even when implemented in software on an inexpensive Pentium 100 system. We also show that the algorithm can achieve interesting compression ratios despite its simplicity.Since the compression/decompression speed of our algorithms exceeds disk bandwidth, its use in a compressed VM system can lead to both memory savings and speed improvements in servicing page faults. In this paper we discuss some possible applications of the algorithm in a compressed VM system.

Controller of in-cylinder injection spark ignition internal combustion engine

Abstract: A control apparatus for a cylinder-injection spark-ignition internal combustion engine switches control mode in accordance with an engine operating state between compression stroke injection mode control, in which fuel is injected during the compression stroke to achieve stratified combustion, and suction stroke injection mode control, in which fuel is injected during the suction stroke to achieve uniform mixture combustion. Where regular gasoline lower in octane number than premium gasoline is used, a target mean effective pressure (Pe), which is set in accordance with throttle opening (θth), is subjected to octane number-based correction to thereby compensate for an engine output change at the mode switching, whereby a torque shock at the time of mode switching is prevented.

Still image recording apparatus which selectively compresses single image information at a first compression ratio and a second compression ratio and to decompress the compressed single image information for display before main storage

Abstract: A still image recording apparatus for compressing and storing image information comprises a compression unit for compressing the same image information at a plurality of different compression ratios, and a memory for storing the image data compressed by the compression unit at the different compression ratios, collectively. It further comprises a selector for setting a combination of compression ratios to the compression unit. The selector selects the combination of compression ratios based on a degree of complexity of the input image information.