Showing papers on "Compression ratio published in 2002"

Compression Ratio Influence on Maximum Load of a Natural Gas Fueled HCCI Engine

Abstract: This paper discusses the compression ratio influence on maximum load of a Natural Gas HCCI engine. A modified Volvo TD100 truck engine is controlled in a closed-loop fashion by enriching the Natural Gas mixture with Hydrogen. The first section of the paper illustrates and discusses the potential of using hydrogen enrichment of natural gas to control combustion timing. Cylinder pressure is used as the feedback and the 50 percent burn angle is the controlled parameter. Full-cycle simulation is compared to some of the experimental data and then used to enhance some of the experimental observations dealing with ignition timing, thermal boundary conditions, emissions and how they affect engine stability and performance. High load issues common to HCCI are discussed in light of the inherent performance and emissions tradeoff and the disappearance of feasible operating space at high engine loads. The problems of tighter limits for combustion timing, unstable operational points and physical constraints at high loads are discussed and illustrated by experimental results. Finally, the influence on operational limits, i.e., emissions peak pressure rise and peak cylinder pressure, from compression ratio at high load are discussed. (Less)

HCCI Combustion Phasing in a Multi Cylinder Engine Using Variable Compression Ratio

Abstract: Combustion phasing in a Homogeneous Charge Compression Ignition (HCCI) engine can be achieved by affecting the time history of pressure and temperature in the cylinder. The most common way has been to control the inlet air temperature and thereby the temperature in the cylinder at the end of the compression stroke. However this is a slow parameter to control, especially cycle to cycle. A multi- cylinder engine using Variable Compression Ratio (VCR) for controlling the compression temperature and consequently the combustion phasing is used in the experiments. Operating range in terms of speed and load is investigated in naturally aspirated mode. Trade-off between inlet air temperature and Compression Ratio (CR) is evaluated. Primary reference fuels, isooctane/n-heptane, are used during the tests. High-speed HCCI operation up to 5000 rpm is possible with a fuel corresponding to RON 60. The effect of octane number with and without exhaust cam phasing is also investigated. Brake thermal efficiency of 33% at a maximum load of 4.4 bar BMEP for 2000 rpm is achieved. (Less)

Improving Compression Ratio, Area Overhead, and Test Application Time for System-on-a-Chip Test Data Compression/Decompression

Abstract: This paper proposes a new test data compression/decompression method for systems-on-a-chip. Themethod is based on analyzing the factors that influencetest parameters: compression ratio, area overhead and testapplication time. To improve compression ratio, the newmethod is based on a Variable-length Input Huffman Coding(VIHC), which fully exploits the type and length of the patterns,as well as a novel mapping and reordering algorithmproposed in a pre-processing step. The new VIHC algorithmis combined with a novel parallel on-chip decoder that simultaneouslyleads to low test application time and low areaoverhead. It is shown that, unlike three previous approaches[2, 3, 10] which reduce some test parameters at the expenseof the others, the proposed method is capable of improvingall the three parameters simultaneously. For example, theproposed method leads to similar or better compression ratiowhen compared to frequency directed run-length coding[2], however with lower area overhead and test applicationtime. Similarly, there is comparable or lower area overheadand test application time with respect to Golomb coding [3],with improvements in compression ratio. Finally, there issimilar or improved test application time when comparedto selective coding [10], with reductions in compression ratioand significantly lower area overhead. An experimentalcomparison on benchmark circuits validates the proposedmethod.

The Effects of Diesel-Ethanol Blends on Diesel Engine Performance

Abstract: The performance of a variable compression ratio compression ignition engine operating on ethanol-diesel fuel blends has been evaluated experimentally. We aimed to determine the optimum percentage of ethanol and the compression ratio of the engine that give the best performance and efficiency at the same time. The engine was operated with ethanol-diesel fuel blends having 2, 4, and 6% ethanol on a volume basis as well as on diesel fuel alone. The experiments were performed for the compression ratios of 19, 21, and 23. Experimental results indicate that the addition of 4% ethanol to diesel fuel increases power output and efficiency of the engine while it decreases specific fuel consumption for various compression ratios. The best efficiency was attained at the compression ratio of 21 with an increment ratio over 3.5%.

An Analytic Model for Cylinder Pressure in a Four Stroke SI Engine

Abstract: An analytic model for cylinder pressures in spark ignited engines is developed and validated. The main result is a model expressed in closed form that describe the in-cylinder pressure development of an SI engine. The method is based on a parameterization of the ideal Otto cycle and takes variations in spark advance and air-to-fuel ratio into account. The model consists of a set of tuning parameters that all have a physical meaning. Experimental validation on two engines show that it is possible to describe the in-cylinder pressure of a spark ignited combustion engine operating close to stoichiometric conditions, as a function of crank angle, manifold pressure, manifold temperature and spark timing.

Extended frequency-directed run-length code with improved application to system-on-a-chip test data compression

Abstract: One of the major challenges in testing a system-on-a-chip (SOC) is dealing with the large test data size. To reduce the volume of test data, several test data compression techniques have been proposed. The frequency-directed run-length (FDR) code is a variable-to-variable run length code based on encoding runs of 0's. In this work, we demonstrate that higher test data compression can be achieved based on encoding both runs of 0's and 1's. We propose an extension to the FDR code and demonstrate by experimental results its effectiveness in achieving higher compression ratio.

Control system and method for an internal combustion engine

Abstract: A control system for an internal combustion engine is provided which comprises a compression ratio control mechanism and a control unit for controlling the compression ratio control mechanism. The control unit including an acceleration parameter obtaining section for obtaining an acceleration parameter corresponding to a change of an engine speed, an acceleration determining section for determining whether the engine is in a slow or fast acceleration state on the basis of the acceleration parameter, and a control section for controlling at least one of a compression ratio change speed at which the engine compression ratio during engine acceleration is changed and a compression ratio change start time at which a change of the engine compression ratio during engine acceleration is started, on the basis of whether the engine is in a slow or fast acceleration state. A control method is also provided.

Controller of compression-ignition engine

Abstract: A control system for a compression injection engine can prevent deterioration in exhaust purification at the time of the switching of combustion between spark ignition and compression ignition, at the time of said spark ignition combustion and said compression injection combustion, and can diagnose any deterioration of an NO x detector and a three way catalyst. The control system includes a catalytic converter installed within an exhaust passage of the compression ignition engine for compressing and igniting a pre-mixture of a fuel and air, an air/fuel ratio detector for detecting an air/fuel ratio at upstream side of said catalytic converter, and an NOx detector for detecting NOx at downstream side of said catalytic converter.

Improved engine management

Abstract: An engine management system (20) for an internal combustion engine comprises an in-cylinder pressure sensor (26) in each engine cylinder (24). Data from the pressure sensors (26) is processed cycle by cycle and closed loop control is implemented to control, for example, spark timing for a cycle based on the in-cylinder pressure data from the previous cycle.

Control apparatus and method for vehicle having internal combustion engine and continuously variable transmission, and control apparatus and method for internal combustion engine

Abstract: A control apparatus is provided for a vehicle including an internal combustion engine and a continuously variable transmission capable of controlling an output speed of the engine. A controller of the control apparatus determines a first operating point at which a total fuel consumption amount is minimized as an optimal operating point, such that the total fuel consumption amount is obtained by adding an amount of a fuel consumed by an exhaust purifying device disposed in an exhaust system to an amount of a fuel consumed by the engine for generating a required output. The controller then controls an engine load and also controls a speed ratio of the transmission so that the engine operates at the optimal operating point.

Piston-Liner Crevice Geometry Effect on HCCI Combustion by Multi-Zone Analysis

Abstract: A multi-zone model has been developed that accurately predicts HCCI combustion and emissions. The multizone methodology is based on the observation that turbulence does not play a direct role on HCCI combustion. Instead, chemical kinetics dominates the process, with hotter zones reacting first, and then colder zones reacting in rapid succession. Here, the multi-zone model has been applied to analyze the effect of piston crevice geometry on HCCI combustion and emissions. Three different pistons of varying crevice size were analyzed. Crevice sizes were 0.26, 1.3 and 2.1 mm, while a constant compression ratio was maintained (17:1). The results show that the multi-zone model can predict pressure traces and heat release rates with good accuracy. Combustion efficiency is also predicted with good accuracy for all cases, with a maximum difference of 5% between experimental and numerical results. Carbon monoxide emissions are underpredicted, but the results are better than those obtained in previous publications. The improvement is attributed to the use of a 40-zone model, while previous publications used a 10-zone model. Hydrocarbon emissions are well predicted. For cylinders with wide crevices (1.3 and 2.1 mm), HC emissions do not decrease monotonically as the relative air/fuel ratio ({lambda}) increases. Instead, maximum HC more » emissions are obtained for an intermediate value of {lambda}. The model predicts this relative air/fuel ratio for maximum HC emissions with very good accuracy. The results show that the multi-zone model can successfully predict the effect of crevice geometry on HCCI combustion, and therefore it has applicability to the design of HCCI engines with optimum characteristics for high efficiency, low emissions and low peak cylinder pressure. « less

Fuel injector having dual mode capabilities and engine using same

Abstract: A solitary fuel injector for a diesel engine that is capable of injecting fuel for a homogeneous charge compression ignition injection event, a conventional injection event. The solitary fuel injector also has a mixed mode that includes a homogeneous charge compression ignition injection and a conventional injection in a single compression stroke for the engine.

Code compression algorithms and architectures for embedded systems

Abstract: Code compression is proposed as a solution to the code size problem for embedded systems. Data compression techniques are used to compress programs to reduce memory size. The compressed programs are then decompressed on-the-fly during execution. However, decompression overhead may induce performance deterioration; therefore, fast decompression schemes and decompression architecture designs are very important when designing a good code compression scheme. In this dissertation, we provide a suite of code compression techniques as well as decompression architecture designs for embedded systems. The FV2CC (Fixed-to-Variable Code Compression) uses fixed-to-variable coding schemes based on a reduced precision arithmetic coding. Multi-bit parallel decompression architecture designs for FV2CC are presented. The V2FCC (Variable-to-Fixed Code Compression) uses variable-to-fixed coding schemes based on Tunstall coding and arithmetic coding algorithms. The techniques are suitable for both RISC architectures and VLIW architectures. However, since code compression for VLIW architectures are not well studied as RISC architectures, we mainly apply the techniques on VLIW architectures. Code density is not the only design goal for embedded system. In this dissertation, we also propose a profile-driven code compression methodology. By using execution profiling, we can achieve instruction bus power reduction via instruction re-encoding, or selectively compress infrequently used instructions such that the performance of a processor is not compromised too much due to the decompression overhead. In summary, the contributions of this dissertation include code compression algorithms and decompression architecture designs which balance the compression ratio and decompression overhead, instruction bus encoding techniques that reduce the bus power consumption, and a profile-driven code compression methodology that balances the compression ratio and processor performance. We use VLIW architectures as the target embedded architectures, however, the techniques are general and suitable for RISC architectures as well. (Abstract shortened by UMI.)

Medical image compression by sampling DCT coefficients

Abstract: Advanced medical imaging requires storage of large quantities of digitized clinical data. Due to the constrained bandwidth and storage capacity, however, a medical image must be compressed before transmission and storage. Among the existing compression schemes, transform coding is one of the most effective strategies. Image data in the spatial domain is transformed into the spectral domain after the transformation to attain more compression gains. Based on the quantization strategy, coefficients of low amplitude in the transformed domain are discarded and significant coefficients are preserved to increase the compression ratio without inducing salient distortion. We use an adaptive sampling algorithm by calculating the difference area between correct points and predicted points to decide the significant coefficients. Recording or transmitting the significant coefficients instead of the whole coefficients achieves the goal of compression. On the decoder side, a linear equation is employed to reconstruct the coefficients between two sequent significant coefficients. Simulations are carried out to different medical images, which include sonogram, angiogram, computed tomography, and X-ray images.

The Development of a Dual Injection Hydrogen Fueled Engine With High Power and High Efficiency

Abstract: To achieve high power and high efficiency in a hydrogen fueled engine for all load conditions, the dual injection hydrogen fueled engine that can derive the advantage of both high efficiency from external mixture hydrogen engine and high power from direct cylinder injection hydrogen engine was introduced. For verifying the feasibility of the above engine, the high pressure hydrogen injector of ball valve type actuated by a solenoid was developed. A systematic experimental study was conducted by using a modified single cylinder dual injection hydrogen fueled engine which was equipped with both an intake injector and a high pressure in-cylinder injector. The results showed that (1) the developed high pressure hydrogen injector with a solenoid actuator had good gas-tightness and fine control performance, (2) the transient injection region, in which injection methods are changed from external fuel injection to direct-cylinder injection, ranged from 59 to 74 percent of the load, and (3) the dual injection hydrogen fueled engine had the maximum torque of direct-cylinder fuel injection and the maximum efficiency of external fuel mixture hydrogen engines.Copyright © 2002 by ASME

Code compression for VLIW processors using variable-to-fixed coding

Abstract: Memory has been one of the most restricted resources in the embedded computing system domain. Code compression has been proposed as a solution to this problem. Previous work used fixed-to variable coding algorithms that translate fixed-length bit sequences into variable-length bit sequences. In this paper, we propose code compression schemes that use variable-to-fixed (V2F) length coding. We also propose an instruction bus encoding scheme, which can effectively reduce the bus power consumption. Though the code compression algorithm can be applied to any embedded processor, it favors VLIW architectures because VLIW architectures require a high-bandwidth instruction pre-fetch mechanism to supply multiple operations per cycle. Experiments show that the compression ratios using memoryless V2F coding for IA-64 and TMS320C6x are around 72.7% and 82.5% respectively. Markov V2F coding can achieve better compression ratio up to 56% and 70% for IA-64 and TMS320C6x respectively. A greedy algorithm for codeword assignment can reduce the bus power consumption and the reduction depends on the probability model used.

Internal combustion engine combustion diagnosis/control apparatus and combustion diagnosis/control method

Abstract: A combustion diagnosis/control apparatus capable of performing smooth engine operation by adjusting a combustion state upon generation of knocking, misfire, and flame extinguishing, and rapidly detecting an abnormal state of the in-cylinder pressure, thereby performing diagnosis/control of an internal combustion engine without stopping operation of the engine. The apparatus includes means for calculating a maximum pressure ratio Pp/Po of the in-cylinder maximum pressure Pp based on an in-cylinder pressure detection value from an in-cylinder pressure detector detecting a pressure in a combustion chamber against a compression pressure Po at one or more points in the compression stroke, means for comparing the maximum pressure ratio Pp/Po with a pressure ratio gradually set by the diagnosis category (hereinafter, referred to as a threshold pressure ratio), and means (step) for performing diagnosis of the combustion state such as the in-cylinder pressure state in the combustion chamber by evaluating the comparison output for every one or more operation cycles.

High compression ratio, hydrogen enhanced gasoline engine system

Abstract: A hydrogen enhanced gasoline engine system using high compression ratio is optimized to minimize NOx emissions, exhaust aftertreatment catalyst requirements, hydrogen requirements, engine efficiency and cost. In one mode of operation the engine is operated very lean at lower levels of power. A control system is used to increase equivalence ratio at increased torque or power requirements while avoiding the knock that would be produced by high compression ratio operation. Accordingly reduced hydrogen requirements at high power can significantly reduce the cost and size of onboard hydrogen generator technology. Increased in-cylinder turbulence and stratified hydrogen injection can be used to minimize hydrogen requirements for operation at a given equivalence ratio value. In another embodiment, hydrogen enhanced exhaust gas recirculation (EGR) at all power levels is used.

Combustion control system for spark ignition internal combustion engine with variable piston stroke characteristic mechanism and variable valve operating mechanism

Abstract: A combustion control system for a spark-ignition internal combustion engine includes a variable piston stroke characteristic mechanism changing a compression ratio of the engine, sensors detecting engine operating conditions, i.e., engine speed and engine load, and at least one of a variable lift and working-angle control mechanism simultaneously continuously changing an intake-valve lift and an intake-valve working angle and a variable phase control mechanism changing an angular phase at a central angle corresponding to a maximum valve lift point of the intake valve. Also provided is a control unit that controls the variable piston stroke characteristic mechanism, and at least one of the variable lift and working-angle control mechanism and the variable phase control mechanism, depending on the engine operating conditions.

Control device of internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To enable both the steep rise of the exhaust temperature and operability in a cold state, and to enhance the early temperature rise of a catalyst. SOLUTION: The device is equipped with a variable valve mechanism to carry out variable control of the opening/closing timing of the intake valve, and a variable compression ratio mechanism to carry out variable control of the compression ratio e. The variable valve mechanism consists of a lift/ operating angle variable mechanism capable of continuously controlling to enlarge and reduce the lift/operating angle of the intake valve and a phase variable mechanism to change a lift angle Φ. At the time of high idling after starting from cold state, the compression ratio e is maintained low, an expansion ratio is reduced, and the exhaust temperature is raised by delaying the ignition timing remarkably from the MBT point. Simultaneously, the operating angle of the intake valve is reduced, and the opening timing of the intake valve is delayed from the top dead center. The combustion deterioration due to the expansion ratio decrease is avoided and a large delay of ignition timing is attained by an increase of flow rate due to the development of negative pressure inside a cylinder, securing actual compression ratio or the like. COPYRIGHT: (C)2004,JPO

Friction effect on the characteristic performance of Diesel engines

Abstract: An irreversible model for an air standard Diesel engine is presented in this paper. This model takes into account the finite-time evolution of the cycle's compression and power strokes and it considers global losses lumped in a friction-like term. The relations between the power output and the compression ratio, as well as between the thermal efficiency and the compression ratio are derived. The maximum power output with the corresponding efficiency, and the maximum efficiency with the corresponding power output are calculated versus compression ratio. Copyright © 2002 John Wiley & Sons, Ltd.

Method and system for the efficient communication of data with and between remote computing devices

Abstract: A method and system for communicating between remote devices is provided. In one aspect, the method provides a compression engine available to a first device with previously communicated information. The compression engine then uses the previously communicated information and the information to be compressed to achieve improved compression ratios. After receiving the compressed information, the receiving device may provide the previously communicated information to a decompression engine, thereby enabling the received, compressed information to be effectively decompressed. With each communication of current device information, the previously communicated information may be updated with the current device information. As a failsafe for corrupt transmissions, out of date previously communicated information, etc., the receiving device may evaluate the integrity of the decompressed information and request a retransmission of the information using alternative compression techniques.

Engine control system of internal combustion engine with variable compression ratio mechanism and exhaust-gas recirculation control system

Abstract: A combustion control system for a spark-ignition internal combustion engine includes a variable piston stroke characteristic mechanism changing a compression ratio of the engine, sensors detecting engine operating conditions, i.e., engine speed and engine load, and at least one of a variable lift and working angle control mechanism simultaneously continuously changing an intake-valve lift and an intake-valve working angle and a variable phase control mechanism changing an angular phase at a central angle corresponding to a maximum valve lift point of the intake valve. Also provided is a control unit that controls the variable piston stroke characteristic mechanism, and at least one of the variable lift and working angle control mechanism and the variable phase control mechanism, depending on the engine operating conditions.