Showing papers on "Compression ratio published in 2009"

Effects of Different Type of Gasoline Fuels on Heavy Duty Partially Premixed Combustion

Abstract: The effects of fuel properties on the performance and emissions of an engine running in partially premixed combustion mode were investigated using nine test fuels developed in the gasoline boiling point range. The fuels covered a broad range of ignition quality and fuel chemistry.The fuels were characterized by performing a load sweep between 1 and 12 bar gross IMEP at 1000 and 1300 rpm. A heavy duty single cylinder engine from Scania was used for the experiments; the piston was not modified thus resulting in the standard compression ratio of 18:1.In order to properly run gasoline type of fuels in partially premixed combustion mode, an advanced combustion concept was developed. The concept involved using a lot of EGR, very high boost and an advanced injection strategy previously developed by the authors.By applying this concept all the fuels showed gross indicated efficiencies higher than 50% with a peak of 57% at 8 bar IMEP. NOx were mostly below 0.40 g/kWh only in few operative points 0.50 g/kWh was reached. At high load the soot levels were mostly a function of the octane number; with RON higher than 95 it was possible to be below 0.5 FSN while for the more reactive fuels a peak value of 3 FSN was reached at 13 bar IMEP.The pressure rise rate reached a peak of 19 bar/CAD with fuels which had a RON above 95, when the octane number decreased below 90 the pressure rise rate was always below 14 bar/CAD. (Less)

Combustion characterization in an internal combustion engine with ethanol - Gasoline blended fuels varying compression ratios and ignition timing

Abstract: Although ethanol possesses only two-thirds the energy density of gasoline, it has other properties that are beneficial to combustion in an internal combustion (IC) engine. These include a higher laminar flame speed and higher octane number relative to gasoline. The higher octane number of ethanol improves knock tolerance, and the faster flame speed provides potential benefits to the combustion process. Understanding these attributes will enable flexible fuel engines to benefit from some of the unique properties of ethanol. While data concerning the efficiency of ethanol fuels at varying compression ratios exist in the literature, there is a lack of fundamental combustion data to validate these results. As such, this work makes use of mass fraction burn (MFB) analysis to examine the differences between various blends of ethanol and gasoline, including the effect of the compression ratio relative to optimal combustion phasing, early and bulk burn rates, and combustion variability. Tests were carried out on ...

Combustion Characteristics of Diesohol Using Biodiesel as an Additive in a Direct Injection Compression Ignition Engine under Various Compression Ratios

Abstract: An experimental investigation is carried out to study the combustion characteristics of diesel−biodiesel−ethanol blends in a single-cylinder four stroke direct injection variable compression ratio engine under the compression ratios 15:1, 17:1, and 19:1. As the ethanol is immiscible with diesel, biodiesel (jatropha methyl ester) is used as an additive to prevent the phase separation of the diesel−ethanol blends. The addition of ethanol decreases the cetane number of the blend, whereas the biodiesel addition improves the cetane number of the resultant mixture. The combustion characteristics of the stable fuel blends (D85B10E5, D80B10E10, D75B10E15, D70B10E20, and D65B10E25) are studied and compared with neat diesel by conducting experiments on the computerized variable compression ratio engine test rig. A piezoelectric pressure sensor and a crank angle encoder are used to record the cylinder gas pressure and a crank angle, respectively, to determine the combustion parameters. It is observed that the cylind...

Physics-Based Modeling and Control of Residual-Affected HCCI Engines

Abstract: Homogeneous charge compression ignition (HCCI) is a novel combustion strategy for IC engines that exhibits dramatic decreases in fuel consumption and exhaust emissions. Originally conceived in 1979, the HCCI methodology has been revisited several times by industry but has yet to be implemented because the process is difficult to control. To help address these control challenges, the authors here outline the first generalizable, validated, and experimentally implemented physics-based control methodology for residual-affected HCCI engines. Specifically, the paper describes the formulation and validation of a two-input, two-state control-oriented system model of the residual-affected HCCI process occurring in a single engine cylinder. The combustion timing and peak pressure are the model states, while the inducted gas composition and effective compression ratio are the model inputs. The resulting model accurately captures the system dynamics and allows the simultaneous, coordinated control of both in-cylinder pressure and combustion timing. To demonstrate this, an H 2 optimal controller is synthesized from a linearized version of the model and used to dictate step changes in both combustion timing and peak pressure within about four to five engine cycles on an experimental test bed. The application of control also results in reductions in the standard deviation for both combustion timing and peak pressure. The approach therefore provides accurate mean tracking, as well as a reduction in cyclic dispersion. Another benefit of the simultaneous coordination of both control inputs is a reduction in the control effort required to elicit the desired response. Instead of using a peak pressure controller that must compensate for the effects of a combustion timing controller, and vice versa, the coordinated approach optimizes the use of both control inputs to regulate both outputs.

Low-Power Scan Operation in Test Compression Environment

Abstract: This paper presents a new and comprehensive low-power test scheme compatible with a test compression environment. The key contribution of this paper is a flexible test-application framework that achieves significant reductions in switching activity during all phases of scan test: loading, capture, and unloading. In particular, we introduce a new on-chip continuous-flow decompressor. Its synergistic use with a power-aware scan controller allows a significant reduction of toggling rates when feeding scan chains with decompressed test patterns. While the proposed solution requires minimal modifications of the existing design for test logic, experiments indicate that its use results in a low switching activity which reduces power consumption to or below a level of a functional mode. It resolves problems related to power dissipation, voltage drop, and increased temperature. Our approach integrates seamlessly with test logic synthesis flow, and it does not compromise compression ratios. It fits well into various design paradigms, including modular design flow where blocks come with individual decompressors and compactors.

Numerical investigation of soot reduction potentials with diesel homogeneous charge compression ignition combustion by an improved phenomenological soot model

Abstract: An improved phenomenological soot model coupled with a reduced n-heptane chemical mechanism was implemented into KIVA-3V code to describe soot formation and oxidation processes in diesel homogeneous charge compression ignition (HCCI) combustion. This model was first validated by the shock tube experiments with a rich n-heptane mixture over wide temperature and pressure ranges. The computational results demonstrate that the phenomenological soot model is capable of predicting the soot yield, particle diameter, and number density with satisfactory accuracy. Then the model was applied to investigate the influence of the orifice diameter and injection pressure on soot emissions in a constant-volume combustion vessel under typical diesel combustion conditions. The predictions showed qualitative agreement with the measurements on the soot volume fraction distribution. The results also indicate that the soot formation can almost be suppressed as the local equivalence ratio is kept lower than 2.0. Finally, the model was used to explore the potentials of soot reduction with HCCI combustion for diesel engines. The overall trend of soot with the variations in the start of injection timing was well reproduced by the model. With the help of an equivalence ratiotemperature map, it was found that nitrogen oxide emissions could be markedly reduced by applying a high exhaust gas recirculation rate and relative low compression ratio for diesel HCCI engines. However, the mixture preparation by using a multi-hole injector with early injection strategy remains a limitation for further reduction in soot emissions

Effect of the compression ratio on the performance and combustion of a natural-gas direct-injection engine

Abstract: An experimental study on the combustion and emissions of a natural-gas direct- injection spark ignition engine under different compression ratios was carried out. The results show that the compression ratio has a large influence on the engine performance, combustion, and emissions. The penetration distance of the natural-gas jet is decreased and relatively strong mixture stratification is formed as the compression ratio is increased, giving a fast burning rate and a high thermal efficiency, especially at low and medium engine loads. However, the brake thermal efficiency is increased with a compression ratio up to a limit of 12 at high engine loads. The maximum cylinder gas pressure is increased with increase in the compression ratio. The flame development duration is decreased with increase in the compression ratio and this behaviour becomes more obvious with increase in the compression ratio at low loads or for lean mixture combustion. This indicates that the compression ratio has a significant influence on the combustion duration at lean combustion. The exhaust hydrocarbon (HC) and carbon monoxide emissions decreased with increase in the compression ratio, while the exhaust nitrogen oxide emission is increased with increase in the compression ratio. The exhaust HC emission tends to increase at high compression ratios. Experiments showed that a compression ratio of 12 is a reasonable value for a compressed-natural-gas direct-injection engine to obtain a better thermal efficiency without a large penalty of emissions.

The performance and emissions of a variable compression ratio diesel engine fuelled with bio-diesel from cotton seed oil

Abstract: A methyl ester of cottonseed oil was prepared and blended with diesel in four different compositions varying from 5% to 20% in steps of 5%. Tests were conducted in a single cylinder variable compression ratio diesel engine at a constant speed of 1500 rpm. Highest brake thermal efficiency and lowest specific fuel consumption were observed for 5% biodiesel blend for compression ratio of 15 and 17 and 20% biodiesel blend for compression ratio of 19. The 20% biodiesel blend at a compression ratio of 17 had maximum nitric oxide emission as 205 ppm, while it was 155 ppm for diesel. Substantial reduction in Carbon monoxide emissions and smoke in the full range of compression ratio and loads was observed. Improved heat release characteristics were observed for the prepared biodiesels. The results reveal that the biodiesels can be used safely without any modification to the engine.

Depth map compression via compressed sensing

Abstract: We propose in this paper a new scheme based on compressed sensing to compress a depth map. We first subsample the entity in the frequency domain to take advantage of its compressibility. We then derive a reconstruction scheme to recover the original map from the subsamples using a non-linear conjugate gradient minimization scheme. We preserve the discontinuities of the depth map at the edges and ensure its smoothness elsewhere by incorporating the Total Variation constraint in the minimization. The results we obtained on various test depth maps show that the proposed method leads to lower error rate at high compression ratio when compared to standard image compression techniques like JPEG and JPEG 2000.

An experimental study of dieseline combustion in a direct injection engine

Abstract: The differences between modern diesel and gasoline engine configurations are now becoming smaller and smaller, and in fact will be even smaller in the near future. They will all use moderately high compression ratios and complex direct injection strategies. The HCCI combustion mode is likely to lead to the merging of gasoline and diesel engine technologies to handle the challenges they are facing, offering a number of opportunities for the development of the fuels, engine control and after-treatment. The authors' recent experimental research into the HCCI combustion quality of gasoline and diesel blend fuels has referred to the new combustion technology as 'Dieseline'. It is found that this kind of fuel blend provides some unexpected benefits to the expansion of the operating window and reduction of hydrocarbon emissions in HCCI engines, and these benefits include extended low misfire limit, increased engine stability, reduced peak cylinder pressures and reduced emissions within the whole HCCI operating window. It was shown that the lean limit of lambda can almost reach up to 2.0 when the engine is operated with moderate compression ratios. It is shown that the combustion of the blended fuel offers promise to the desired ignition quality, which reduces the dependence of HCCI on EGR trapping or intake heating for a wide range of CR. The HCCI operating region for the unheated NVO can be significantly extended into lower IMEP values and the audible knocking is restrained to the highest values of air fuel ratio at high load boundary for the highest mixture temperatures. Copyright ©2009 SAE International.

Compression based on deterministic vector clustering of incompatible test cubes

Abstract: The presented compression scheme is a novel solution that is based on deterministic vector clustering and encompasses three data reduction features in one on-chip decoding system. The approach preserves all benefits of continuous flow decompression and offers compression ratios of order 1000x with encoding efficiency much higher than 1.00.

Multi-camera tele-immersion system with real-time model driven data compression: A new model-based compression method for massive dynamic point data

Abstract: Vision-based full-body 3D reconstruction for tele-immersive applications generates large amount of data points, which have to be sent through the network in real time. In this paper, we introduce a skeleton-based compression method using motion estimation where kinematic parameters of the human body are extracted from the point cloud data in each frame. First we address the issues regarding the data capturing and transfer to a remote site for the tele-immersive collaboration. We compare the results of the existing compression methods and the proposed skeleton-based compression technique. We examine the robustness and efficiency of the algorithm through experimental results with our multi-camera tele-immersion system. The proposed skeleton-based method provides high and flexible compression ratios from 50:1 to 5000:1 with reasonable reconstruction quality (peak signal-to-noise ratio from 28 to 31 dB) while preserving real-time (10+ fps) processing.

Methods and Systems for Engine Control

Abstract: Methods and systems for controlling an engine are provided. In some examples, the engine has at least a cylinder and a compression device coupled to an intake of the engine, and the method includes, during engine re-start operation of an engine idle-stop condition, commencing combustion in the cylinder from a non-combusting condition, the combustion in a two-stroke combustion cycle of the cylinder. However, in some examples, at least partially electrically powered boosting operation may also be used to extend the two-stroke operation during a start.

Control apparatus for a cylinder direct-injection internal combustion engine

Abstract: A control apparatus is provided for a four stroke cylinder direct-injection internal combustion engine having a cylinder and a piston disposed within the cylinder. The control apparatus includes a variable compression ratio mechanism for variably controlling the engine compression ratio by changing the top dead center position of the piston and a fuel injection device for injecting fuel directly into the cylinder. When the actual compression ratio of the engine is higher than a target compression ratio, the variable compression ratio mechanism reduces the compression ratio, and in accordance with the reduction in the compression ratio, the fuel injecting device injects an intake fuel injection amount in the intake stroke and a compression fuel injection amount in the compression stroke, and the timing for starting the fuel injection in the compression stroke is retarded.

Heat pump drying machine

Abstract: An heat pump drying machine has a normal dry mode (e.g., compression ratio is equal to or greater than 3) for operating a compressor at a predetermined dry operation frequency and an energy saving dry mode (e.g., compression ratio is equal to or greater than 2.3 and is less than 3) for operating the compressor at an energy saving operation frequency that is lower than the dry operation frequency. A control device is provided to control an operation frequency of the compressor 5 so that the two dry operation modes are switched to each other. The control device can execute the control for increasing the operation frequency of the compressor to the dry operation frequency during the operation of the energy saving dry mode.