Showing papers on "Compression ratio published in 1991"

Data compression: effect on diagnostic accuracy in digital chest radiography.

Abstract: High-resolution digital images make up very large data sets that are relatively slow to transmit and expensive to store. Data compression techniques are being developed to address this problem, but significant image deterioration can occur at high compression ratios. In this study, the authors evaluated a form of adaptive block cosine transform coding, a new compression technique that allows considerable compression of digital radiographs with minimal degradation of image quality. To determine the effect of data compression on diagnostic accuracy, observer tests were performed with 60 digitized chest radiographs (2,048 x 2,048 matrix, 1,024 shades of gray) containing subtle examples of pneumothorax, interstitial infiltrate, nodules, and bone lesions. Radiographs with no compression, with 25:1 compression, and with 50:1 compression ratios were presented in randomized order to 12 radiologists. The results suggest that, with this compression scheme, compression ratios as high as 25:1 may be acceptable for pr...

An Explanation for Observed Compression Ratios in Internal Combustion Engines

Abstract: In this paper comparisons of the compression ratios, efficiencies, and work of the ideal Otto and Diesel cycles are presented at conditions that yield maximum work per cycle. The compression ratios that maximize the work of the Diesel cycle are found always to be higher than those for the Otto cycle at the same operating conditions, although the thermal efficiencies are nearly identical. The compression ratios that maximize the work of the Otto and Diesel cycles compare well with the compression ratios employed in corresponding production engines.

An adaptive data compression system

Abstract: An adaptive data compression system comprises an encoder (2) which responds to input characters by producing output codewords according to a stored encoding map or table of characters and codewords, and adapting means (4, 5) which adapts the encoding map or table in accordance with the input characters so as to increase the compression ratio between the input characters and output codewords, characterised in that optimisation means (5) monitors the performance of the system and accordingly varies adaptation of the encoding map or table by the adapting means (4) so as to optimise performance of the system. Performance of the system is preferably monitored in terms of the computational loading of the processor and the compression ratio it achieves. A decoder (7) subsequently decodes the codewords by reference to a corresponding decoding map or table which is adapted (9, 10) in accordance with the output data from the decoder and in accordance with variations in the adaptation process in the encoder.

Variable displacement and compression ratio piston engine

Abstract: The present invention contemplates a mechanically simply constructed mechanism located internally of a piston engine for adjustably changing the stroke of a piston over a predetermined range in response to a variety of operating control parameters The adjustable stroke changing mechanism provides an optimum compression ratio at each change in piston stroke and over the entire range of piston stroke provided which may be varied from one piston engine to another of different performance characteristics without requiring a major change in design of the stroke changing mechanism The stroke changing mechanism includes a swing plate pivotally fixed to the engine block at one end and placed intermediate the piston connection rod and respective crankshaft pin at its other end, each of which are affixed to and translate within the swing plate as the piston is driven to reciprocate within a piston cylinder An adjustment link is pivotally connected to the engine block at one end and to the connecting rod at its other end and at the swing plate The adjustment link is hydraulically controlled and actuable to vary in length and thereby change the stroke, and concurrently the compression ratio of the piston

Cooling of an internal-combustion engine

Abstract: In order to cool an engine effectively, an engine oil temperature is detected by an oil temperature sensor. When the engine oil temperature is above a predetermined valve, the cooling fluid being introduced into the engine is divided into two streams. One stream is introduced into a cylinder head and the other stream is introduced into a cylinder block. The amount of cooling fluid being introduced into the cylinder block is controlled according to the engine oil temperature.

Tape controller with data compression and error correction sharing a common buffer

Abstract: A controller has a data compression unit and error correcting code unit which share a single common random access memory. The controller is connected between a host computer and a peripheral device such as a tape drive. A second order search for strings of data bytes is enabled or disabled to change the compression ratio, data throughput, and memory bandwidth constraints.

Method and apparatus for detecting combustion conditions in multicylinder internal combustion engine based upon engine speed evaluation

Abstract: A method and apparatus for detecting the quality of combustion in each cylinder of a multi-cylinder internal combustion engine is disclosed. The invention determines a combustion stroke of each cylinder by sensors and detects the rotational speed of the engine at least three times during each combustion stroke by a rotation speed calculation device. The detected rotational speeds are evaluated by an arithmetic calculation device to identify the variation in rotational speed of each piston during a combustion stroke whereby the quality of combustion is, thus, determined. In a feature of the invention fluctuations in rotational speed caused by reciprocating inertia (ωc) are calculated and eliminated from fluctuation in engine speed caused by combustion (ωg) so that the quality of combustion based only upon variation in detected speeds caused by combustion is derived.

Continuous external heat engine

Abstract: A thermal engine utilizing a positive displacement rotary expander and preferably a positive displacement rotary compressor in conjunction with an external substantially steady-state thermal source, such as a continuous fuel combustor, the external source heating a high pressure gas that is directed from the thermal source to the rotary expander wherein the gases expand driving a rotor in the positive displacement rotary engine before discharge. An additional embodiment of the thermal engine includes a modified epitrochoidal chamber configuration for the compression cycle and the expansion cycle to utilize the total internal volume for each compression pulse and expansion pulse for obtaining improved thermal efficiency in a manner similar to super long stroke reciprocal piston engines.

Dual compression and dual expansion internal combustion engine and method therefor

Abstract: The subject engine (8) includes a low pressure piston assembly reciprocally disposed in an operating chamber (22) defined in a housing (10). A pair of opposed high pressure piston assemblies (58) and (60) are directly mounted on a pair of geared together, counter rotating, crankshafts (52) and (54) and reciprocally disposed in bores (178) of the low pressure piston assembly. The disposition of the second and third piston assemblies (58) and (60) within their respective bores (178) defines a combustion chamber. An intake chamber (144) for compression of inducted air and an exhaust chamber (146) for expansion of exhaust gas are defined in the operating chamber (22) between the low pressure piston assembly and the housing (10).

Free piston engine control system

Abstract: A control system for a variable stroke free piston engine, sets the ignition timing as a function of measured piston velocity. This velocity proportional ignition system provides spark advance on a stroke by stroke basis as an aid to starting the engine. Ignition changes over to a piston position based system when the engine is running at steady state. Fuel injection occurs at either piston dead point or is set as a function of piston position. Fuel injection is suppressed during cycles were the ports are not uncovered. The control system can also regulate compression ratio based upon piston position or knock sensor data. The preferred control system includes a hybrid digital analog system which includes a microprocessor.

Adaptive learning control for engine intake air flow

Abstract: An adaptive learning control method is described for regulating the quantity of air inducted into a fuel injected internal combustion engine to achieve a desired air-fuel ratio, where the amount of fuel supplied to each engine cylinder is determined directly as a function of operator demand for engine output. The rotational speed of the engine is sensed, and indication are derived for the actual mass of air inducted into each engine cylinder and for a desired mass of air for each engine cylinder. For the region in which the engine is operating, open-loop and closed-loop values are determined for controlling engine air flow. A previously stored learning correction value corresponding to the engine operating region is obtained, and the quantity of air flowing to the engine is adjusted in accordance with the sum of the open-loop value, the closed-loop value, and the learning correction value. The learning correction value is periodically updated as a function of the difference between the indicated actual and desired mass of air for each engine cylinder, when the engine continuously operates in the region and a predetermined time has elapsed since the engine first began continuous operation in the region.

Classified block truncation coding-vector quantization: An edge sensitive image compression algorithm

Abstract: Block truncation coding-vector quantization (BTC-VQ) is an extremely simple non-adaptive block-based image compression technique. It has a relatively low compression ratio; however, the simplicity of the algorithm makes it an attractive option. Its main drawback is the fact that the reconstructed pictures suffer from ragged edges. In this paper we show that by allowing the algorithm to adapt to the local picture statistics and by paying particular attention to the nature and reproduction of edges in the picture we are able to substantially improve the visual picture quality and at the same time allow for a moderate increase in the compression ratio.

New asymptotic bounds and improvements on the Lempel-Ziv data compression algorithm

Abstract: New results, which follow from a data compression algorithm proposed by A. Lempel and J. Ziv (1977), are presented. The authors describe the original Lempel-Ziv algorithm, and present an improved Lempel-Ziv data compression algorithm. They state and prove some asymptotic bounds on the compression ratio that the improved algorithm achieves. For completeness, they describe the Lempel-Ziv-Welch data compression algorithm presented by T. A. Welch (1984). A software implementation for both the original and the improved Lempel-Ziv algorithms is given, and the algorithms are compared with each other as well as with the Lempel-Ziv-Welch algorithm. >

Internal combustion engine and method

Abstract: Disclosed are methods of and means for an improved internal combustion engine performance and of substantially reduced or eliminated pollutants. A relatively slow and long burning combustion is provided which produces an exhaust of high pressure which can be utilized to drive a turbocharger or cylinder or subsequent cylinders. Ideally, the compression ratio is reduced with respect to current internal combustion engines, and the maximum temperature in the power or combustion cylinder can be below the temperature at which NO x is formed. Preferably the pressure during combustion remains substantially constant and the air or air/fuel mixture is externally compressed 40 to 100% of its compression pressure in the combustion cylinder. This results in a controlled energy release tailored to a change in volume per unit of time which results in more torque and horsepower, less fuel consumption and drastically decreases pollution, both chemical and heat to the atmosphere. A number of preferred embodiments are disclosed.

Determining device for determining a failure in an engine cylinder

Abstract: A determining device for determining a failure in an engine cylinder of an internal combustion engine, comprising a variation detecting unit for sequentially detecting a variation in an engine speed between a first engine speed detected by an engine speed detecting unit during a combustion process at a first engine cylinder and a second engine speed detected by the engine speed detecting unit during a combustion process at a second engine cylinder immediately preceding the first engine cylinder with respect to an ignition sequence of all of the engine cylinders, a first determining unit for determining that a misfire has occurred when the variation in the engine speed detected by the variation detecting unit is larger than a predetermined first variation in the engine speed, a second determining unit for determining that a failure has occurred in an engine cylinder when a frequency at which the first determining unit determines that a misfire has occurred is larger than a predetermined frequency, and a value control unit for increasing at least one of the predetermined first variation in the engine speed and the predetermined frequency in accordance with an increase in the engine load detected by the engine load detecting unit.

Combustion engine with variable compression ratio

Abstract: An internal combustion engine (10) is designed with a cylinder section (11) which is pivoted on a crankcase section (13) to provide different compression ratios. The crankcase section (13) is provided with raised lateral walls (21, 22, 24, 25) with upper surfaces (82-85), which lie in the same plane and thereby allow simple assembly of a seal (34) between the cylinder section (11) and crankcase section (13). The lateral walls (21, 22, 24, 25) also enable auxiliary devices for the engine to be easily secured without having to allow for the mobility of the cylinder section (11) relative to the crankcase section (13).

Overheat detecting apparatus for engine

Abstract: A method and apparatus for detecting engine overheating and controlling engine ignition timing utilizes a single temperature sensor. The temperature sensor is positioned adjacent a cylinder head of an engine. A rate of engine temperature increase is calculated based on engine temperature information produced by the temperature sensor, and engine speed is regulated based on the calculated rate of engine temperature increase. Ignition timing is also controlled in response to the engine temperature information produced by the temperature sensor, and the engine speed is regulated to a predetermined speed value whenever the engine temperature exceeds a predetermined temperature value.

Design and evaluation of a fast-burn spark-ignition combustion system for gaseous fuels at high compression ratios

Abstract: The use of cogeneration has led to strong interest in converting diesel engines to spark-ignition operation on gaseous fuels. The two combustion-system options (open chamber and pre-combustion chamber) are reviewed, and the advantages of an open-chamber combustion system are presented. The design philosophy of a fast-burn high-compression-ratio lean-burn combustion system is discussed, and experimental results are presented from tests using natural gas and natural gas/carbon dioxide mixtures. Particular emphasis is placed on the combustion analysis and emissions performance, and considerable potential has been demonstrated for low specific emissions of nitrogen oxides. The combustion system has allowed the use of a 15:1 compression ratio with very low levels of cycle-by-cycle combustion variations. Comprehensive performance data are presented for equivalence ratios in the range of 0.5 to 1.2, for the engine operating at 1500 rev min-1 with a wide-open throttle.

Controlled variable compression ratio internal combustion engine

Abstract: An improved arrangement for controlling and adjusting the compression ratio of an internal combustion engine (10) during operation. A secondary cylinder (201) is formed in the engine cylinder head (102) and opens upon the combustion chamber (110) of the engine. A secondary piston (203) is positioned by a control device (503) within the secondary cylinder (201). The rear most position corresponding to the lowest compression ratio. The desired position of the secondary piston (203), that compression ratio which corresponds to maximum efficiency of the engine, is controlled by a logic unit (816) operating upon such inputs as the engine load as correlated to the input manifold pressure, the engine RPM and the present position of the secondary piston (203). The linkage of the control may utilize a servo motor or hydraulic driver to rotate a shaft (301). All secondary pistons (203) may be operated in unison or a control system may be provided for each cylinder (201). An involute surface (302) mounted on the shaft (301) pushes the spring (204) loaded secondary piston (203) into the secondary cylinder (201). A worm gear (602) on the shaft (301) may turn a threaded bolt (603) to position the secondary piston (203). Or, a worm gear (813) may engage a gear (814) formed on the involute (815) to directly position the involute surface (815).

Visualization and volumetric compression

Abstract: We performed volume compression on CT and MR data sets, each consisting of 256 X 256 X 64 or 32 images, using three-dimensional (3D) DCT followed by quantization, adaptive bit-allocation, and Huffman encoding. Cuberille based surface rendering and oblique angle slicing was performed on the reconstructed compression data using a multi-stream vector processor. For CT images 3D-DCT was found to be successful in exploiting the additional degree of voxel correlations between image frames, resulting in compression efficiency greater than 2D-DCT of individual images. During rendering operations, a substantial amount of thresholding, resampling, and filtering operations are performed on the data. At compression ratios in the range 6 - 15:1, 3D compression was not found to have any adverse visual impact on rendered output. Of these two methods, oblique angle slicing, which involves the fewest operations was found to be the most demanding of small compression errors. We conclude that 3D-DCT compression is a viable technique for efficiently reducing the size of data volumes which must be analyzed with various rendering methods.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Compression experiments with AVHRR data

Abstract: This paper describes several data compression approaches for producing browse data from AVHRR data, and evaluates these approaches qualitatively and quantitatively. They include a hierarchical data compression scheme based on progressively finer image segmentations, and various vector quantization approaches. They are evaluated in terms of compression ratio (or data rate), computational requirements, and the image and analysis errors introduced due to lossy compression. Analysis products evaluated for error include cloud coverage area and sea surface temperatures. >

The Effect of Piston Temperature on Hydrocarbon Emissions from a Spark-Ignited Direct-Injection Engine

Abstract: Light-load unburned hydrocarbon emissions were studied experimentally in a spark-ignited direct-injection engine burning gasoline where the piston temperature was varied The test engine was a single-cylinder Direct-Injection Stratified-Charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System At a single low load operating condition, the piston temperature was varied by 50 K by controlling the cooling water and oil temperature The effect of this change on unburned hydrocarbon emissions and heat release profiles was studied It was found that by carefully controlling the intake air temperature and pressure to maintain constant in- cylinder conditions at the time of injection, the change in piston temperature did not have a significant effect on the unburned hydrocarbon emissions from the engine It was concluded that fuel wetting of the piston surface is not a significant source of hydrocarbon emissions from engines of this type when burning gasoline (A) For the covering abstract of the conference see IRRD 852385

Otto-cycle engine

Abstract: An Otto-cycle engine in which the expansion ratio is set in the range 11:1 to 16:1. A combustion knock sensor detects the onset knocking and a valve actuating timing-adjusting device mounted on the cam shaft that drives the suction valve, delays the timing at which the suction valve is closed, via an actuator in response to the output signal from the sensor. Thus, the substantial compression ratio is adjusted.

Variable compression ratio piston

Abstract: A variable compression ratio device for an internal combustion engine includes a connecting rod having passages formed therein for communicating a hydraulic signal to the piston attached to the connecting rod, means for generating a hydraulic signal having a signal characteristic which is indicative of a desired compression ratio, and a variable compression height piston which is positionable in a plurality of compression heights, including fully retracted, fully extended, and at least one position therebetween, with the piston having an outer section slidably mounted on an inner section, and with the inner section being attached to the connecting rod, with the piston having means responsive to inertia and gas pressure forces and to the generated hydraulic signal for controlling the compression height.

Variable compression device for two cycle diesel engine

Abstract: A variable compression ratio mechanism for a two cycle diesel engine embodying auxiliary exhaust passages and auxiliary exhaust ports that communicate with the cylinder above the main exhaust ports and in which control valves are positioned for controlling the opening and closing of the auxiliary exhaust ports to change the effective compression ratio of the engine to minimize dead space between exhaust control valves and the auxiliary exhaust ports, the exhaust control valves are positioned in close proximity to the cylinder and comprise valve elements that operate in bores that are disposed substantially parallel to the cylinder bore. Both rotary and reciprocating type valves are disclosed and various mechanisms are disclosed for interlinking the control valves for simultaneous operation. In addition, the positioning of the auxiliary exhaust passages permits the formation of a cooling jacket between them that cools not only the auxiliary exhaust passages but also the control valves and the main exhaust passage. Embodiments are shown of adapting these principals to multiple cylinder engines and in which the main exhaust passages are formed in an acute angle to a plane containing the axes of the cylinder bores so as to permit a compact construction.

Compression release brake with variable ratio master and slave cylinder combination

Abstract: A method and apparatus for braking a multicylinder diesel engine. Some compressed gases are released from each engine cylinder near top dead center of each compression stroke on each cycle of the engine by forcing open the exhaust valve with a slave piston assembly of a two-stage master and slave cylinder combination. The slave piston assembly is moved by a master piston assembly which operatively engages an engine component which moves prior to top dead center of each compression stroke. The ratio of the area of the master piston assembly to the slave piston assembly is then increased and the exhaust valve is then opened to a preset fully cracked open position during a second stage of the master and slave cylinder combination. Loading on the engine component is reduced during the first stage and the rate of opening the exhaust valve is increased during the second stage when the force required to further open the exhaust valve has been reduced.

Failure diagnosis device for an engine which compares airfuel ratio and exhaust pressure with a predetermined value

Abstract: A failure diagnosis device for determining engine abnormalities by comparing the air-fuel ratio or the exhaust pressure of an engine with a predetermined value or by determining that the air fuel ratio or the exhaust pressure of the engine is different from the average air-fuel ratio or the average exhaust pressure by a predetermined amount. This comparison is made only when the engine is in a predetermined running condition in which either the air-fuel ratio or the exhaust pressure is stabilized for a predetermined period of time. When the air-fuel ratio or exhaust pressure is different from the average air-fuel ratio or from the average exhaust pressure by a predetermined value, engine abnormality can be detected for each cylinder or for each cylinder group.