› › The Setup And Experimental Results Of Direct Water Injection In A Spark Ignited Natural Gas Engine At Varying Compression Ratios

THE SETUP AND EXPERIMENTAL RESULTS OF DIRECT WATER INJECTION IN A SPARK IGNITED NATURAL GAS ENGINE AT VARYING COMPRESSION RATIOS

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File Size : 35,46 MB

Release : 2013

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Abstract : A production Kohler 8.5RES residential stand-by generator set (Genset) was selected as the platform for this study due to its availability, simplicity, and price point. The Genset consists of a spark ignited (SI) two cylinder vee style internal combustion engine (ICE) capable of running natural gas or propane fuel with a 8.5 kW generator connected directly to the engines crankshaft. This allows for electrical load to be applied to the generator which in turn loads the engine without the use of a conventional dynamometer. A water cooled fully adjustable electric resistive load bank allows for easy adjustment to the desired load point. The electrical power generated was measured to determine the ICE output power and calculate the fuel energy to electrical energy conversion efficiency. To allow for control of the engine while testing it was modified from its original carbureted form to a port fuel injected (PFI) configuration and the original fixed spark timing system was removed and replaced with a coil ignition system. An electronic throttle body (ETB) was fitted to allow adjustment to the incoming air flow. The cylinder heads were modified to allow for a production direct inject (DI) fuel injector which used to deliver water to the combustion chamber and an in cylinder pressure transducer for analysis of various combustion parameters. The genset and test cell were instrumented with low speed and high speed dataacquisition (DAQ) systems to monitor and capture data at the chosen operatingconditions. The high speed data captured by the DAQ was used in conjunction with anear real-time combustion analysis program which calculated and logged combustionparameters and allowed for optimization of spark timing at each test point. Low speed data including fuel consumption, air mass flow rat, water consumption, and electrical power generated along with other engine parameters were monitored and logged as well. The ICE was tested at three different compression ratios (CRs) by changing the pistons and then by removing material from the cylinder head to decrease the clearance volume. The CR that came from the engine supplier was the first to be tested, second a CR in the range of 10:1-11:1 was targeted, and the range of the third CR was 14:1-15:1. The exact values of the CRs tested were calculated once the modifications were complete and volume measurements could be made. The first CR tested was 8.5:1 which is what the engine comes with from the supplier, the second 10.75:1 after changing pistons, and the third 14.3:1 after removing material from the cylinder head. Baseline data was collected at the 8.5:1 CR using the factory the fuel and ignition system to be used for comparison. Once the fuel, spark, and ETB modifications were complete tests were conducted by varying the load from 0 kW to the maximum attainable load at each test condition in 1 kW increments while targeting a relative air-fuel ratio (lambda, λ) of 1.0 and a speed of 3600 rpm. Using the combustion analysis software the gross indicated mean effective pressure (IMEP) was maximized for each test by varying spark timing. Water was injected into the combustion chamber at water to fuel ratios (WFRs) of 0.38, 1.0, and 1.5 by mass. These WFRs were chosen by the sponsor; the lowest possible WFR was to be tested as well as the 1.0 and 1.5 ratios. The lowest value of 0.38 was determined by testing the mass flow rate of the water injectors at decreasing durations. It was found that at WFRs lower than 0.38 the mass of water injected varied due to the injector's response properties. The start of injection (SOI) for water was swept from 180 degrees before top dead center (℗ʻBTDC) to 40 ℗ʻBTDC on the compression stroke in 20℗ʻ increments at each load condition tested. Before water injection tests began, each load point was tested and optimized to obtain baselines to be used for comparison against the water injection results for each CR tested. For each test performed an analysis was conducted to determine the effects of water injection of net fuel conversion efficiency, coefficient of variation (COV) of IMEP, and heat release rate which are discussed in greater detail later in this paper. Fuel conversion efficiency was used to determine if the water increased or decreased the conversion from fuel energy to mechanical work and quantified how it was impacted. The stability of combustion was determined by using the IMEP coefficient of variance which is common practice in ICE analysis to see how the water effected the variance in IMEP from cycle to cycle. Lastly heat release data was used to determine if the burn rate and ignition delay was impacted with the presence of water. From this data trends were identified and conclusions drawn regarding the overall impact water injection has on combustion.



Water Injection and Its Impact on Knock Mitigation in Spark Ignited Engines

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Page : pages

File Size : 11,64 MB

Release : 2020

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Abstract : One of the limiting factors influencing the improvement of engine efficiency in gasoline engines is engine knock. Several techniques including reduced compression ratio, cooled exhaust gas recirculation, using high premium fuels, late intake valve closing have been used to mitigate knock at different operating regimes. Water due to its higher latent heat of vaporization compared to gasoline fuel has been used to reduce the charge temperature and mitigate knock. When water is injected into the intake manifold or into the cylinder, it evaporates by exchanging energy from the surrounding mixture resulting in charge cooling. This allows the engine to be run with advanced spark timing without engine knock resulting in better engine performance. With this motive, the impact of water injection on the combustion characteristics of gasoline direct injection engine was investigated. The research was conducted in three parts. First, an analytical model was developed using the principles of thermodynamics to determine the impact of direct water injection on the cycle efficiency. An ideal thermodynamic cycle with constant volume heat addition was considered for the analysis consisting of air, fuel and water mixture. State properties of the mixture were determined at different points in the thermodynamic cycle and efficiency was calculated. This established a baseline on the amount of water that can be injected into the cylinder and its impact on the overall cycle efficiency. This was followed by spray studies on a spray and combustion vessel that were conducted at engine conditions by varying the ambient conditions to determine the vaporization of water and water methanol sprays. This study gives a comparison of the amount of water that can be vaporized from the thermodynamic model. Experimental studies were conducted on a single cylinder engine with a compression ratio of 10.9:1. Baseline tests without water injection were run using gasoline fuel blended with 10% Ethanol (E10) (Anti-Knock Index = 87.0) injected directly into the cylinder. Impact of water injection was studied by injecting water and blends of water and methanol in the intake manifold at different water fuel ratios within controlled knock limit. Furthermore, injection mechanism was changed to direct water injection and tests were conducted at the same conditions to compare the effect of water injection mechanism on the combustion and knock performance.



Exploration of Combustion Strategies for High-efficiency, Extreme-compression Engines

Author : Mr. Matthew Neil Svrcek

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Page : pages

File Size : 15,3 MB

Release : 2011

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Increasing the compression ratio of an internal combustion engine to 100:1 or greater could potentially enable efficiencies greater than 60%. Understanding and managing the combustion process is a critical component to achieving this in practice. This thesis explores strategies for combustion at extreme compression ratios. First, the setup of a free-piston device capable of operating at 100:1 compression ratio is described. Initial performance results are reported for air-only experiments. Diesel-style combustion was the first approach taken, as it provides facile ignition phasing. Results are reported from initial lean Diesel combustion experiments at compression ratios ranging from 30 to 100:1. Indicated efficiency peaked at 60% for these experiments. To further understand Diesel-style combustion at extreme compression ratios, a study of Diesel sprays in the extreme compression apparatus was performed. The setup of a combined schlieren and direct luminosity imaging system with full-bore optical access is described. Spray penetration, dispersion, liquid length, and ignition delay are reported for combusting and non-combusting sprays. Compression ratios for these experiments ranged from 30 to 100:1. Spray behavior followed expected trends as a function of primary variables such as gas density. However, rapidly varying gas density from the free-piston profile impacts the spray penetration. Furthermore, at the highest compression ratios in-cylinder fluid motion dramatically affects the spray behavior, enabled by the low ratio of fuel to gas density. Systems added to the extreme compression apparatus to measure gaseous and particulate emissions are described. Emissions measurements from Diesel-style combustion of isooctane at 35:1 compression ratio are reported, to provide a reference case at conditions similar to conventional engines. Emissions were similar to those from production Diesel engines, with the exception that soot, HC, and CO increased more rapidly with equivalence ratio in the present study. Results from experiments with Diesel combustion up to 100:1 compression ratio are also reported. The combustion efficiency was 99% up to 100:1 compression ratio, and HC, CO and soot emissions were low. Emissions of NOx were 5 times higher at 100:1 than at 35:1, and would require aftertreatment. Stoichiometric, premixed-charge combustion enables the use of a three-way catalyst and produces low soot levels. Using this approach at extreme compression ratios requires delaying autoignition until the minimum volume is reached. Options for control of autoignition are discussed, and gas cooling is identified as the most effective. Pre-refrigeration, intercooling, and evaporation of a liquid are modeled and shown to effectively achieve the desired ignition timing at 100:1 compression ratio, without impacting the overall engine efficiency. Experimental results are reported for premixed methane-air combustion with intercooling control of autoignition, for 0.96 to 1.04 equivalence ratio and 35 to 90:1 effective compression ratio. The gas cooling requirement for autoignition control was higher than predicted by the models, but still within practical reach. The indicated efficiency peaked at 57%. Emissions levels from these experiments were similar to stoichiometric spark-ignited natural gas engines reported in the literature, and indicate that a three-way catalyst could be successfully used even at extreme compression ratios. Results are also reported for water injection control of autoignition. Autoignition was successfully controlled up to 60:1 effective compression ratio, but the mass of water required was an order of magnitude higher than predicted. This is shown to result from practical limitations of the current water injector setup.



Automotive Spark-Ignited Direct-Injection Gasoline Engines

Author : F. Zhao

Publisher : Elsevier

Page : 129 pages

File Size : 33,52 MB

Release : 2000-02-08

Category : Technology & Engineering

ISBN : 008055279X

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The process of fuel injection, spray atomization and vaporization, charge cooling, mixture preparation and the control of in-cylinder air motion are all being actively researched and this work is reviewed in detail and analyzed. The new technologies such as high-pressure, common-rail, gasoline injection systems and swirl-atomizing gasoline fuel injections are discussed in detail, as these technologies, along with computer control capabilities, have enabled the current new examination of an old objective; the direct-injection, stratified-charge (DISC), gasoline engine. The prior work on DISC engines that is relevant to current GDI engine development is also reviewed and discussed. The fuel economy and emission data for actual engine configurations have been obtained and assembled for all of the available GDI literature, and are reviewed and discussed in detail. The types of GDI engines are arranged in four classifications of decreasing complexity, and the advantages and disadvantages of each class are noted and explained. Emphasis is placed upon consensus trends and conclusions that are evident when taken as a whole; thus the GDI researcher is informed regarding the degree to which engine volumetric efficiency and compression ratio can be increased under optimized conditions, and as to the extent to which unburned hydrocarbon (UBHC), NOx and particulate emissions can be minimized for specific combustion strategies. The critical area of GDI fuel injector deposits and the associated effect on spray geometry and engine performance degradation are reviewed, and important system guidelines for minimizing deposition rates and deposit effects are presented. The capabilities and limitations of emission control techniques and after treatment hardware are reviewed in depth, and a compilation and discussion of areas of consensus on attaining European, Japanese and North American emission standards presented. All known research, prototype and production GDI engines worldwide are reviewed as to performance, emissions and fuel economy advantages, and for areas requiring further development. The engine schematics, control diagrams and specifications are compiled, and the emission control strategies are illustrated and discussed. The influence of lean-NOx catalysts on the development of late-injection, stratified-charge GDI engines is reviewed, and the relative merits of lean-burn, homogeneous, direct-injection engines as an option requiring less control complexity are analyzed.



AN EXPERIMENTAL STUDY ON THE IMPACT OF WATER INJECTION ON THE PERFORMANCE AND EMISSIONS OF A NATURAL GAS - DIESEL PILOT ENGINE

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File Size : 11,6 MB

Release : 2022

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Abstract : Natural gas has been gaining popularity as an alternative fuel due to its high availability, low CO2 emissions, and low cost. In this experimental study, water injection's impact on medium and heavy-duty engine operation fueled by natural gas and pilot diesel injection for ignition was studied under stochiometric operation for use with a three-way catalytic converter to meet criteria emissions for off-road power generation. To retain high efficiencies, a high compression ratio of 17.3:1 was used. Maintaining stoichiometric operation with a high compression ratio leads to combustion knock, pre-ignition, and high NOx formation. Conventionally, cooled EGR can be used to reduce NOx, but results in increased soot and does not eliminate combustion knock and pre-ignition. As an alternative to EGR this work utilized port injected water to provide on demand charge cooling, successfully reducing both NOx and soot while enabling high-load operation. A combination of both high and low speeds and loads were tested to study the impact of water injection on the emissions and performance of the natural gas, diesel-pilot engine. Additionally, water injections impact on diesel only operation was tested to provide comparison metrics and aid in a better understanding of the mechanisms at work when injecting water in an internal combustion engine. At full load, 16.8 bar BMEP, it was found that a water to fuel ratio of 0.5:1 was sufficient to enabling the knock free operation without significant increase in combustion duration or instability where operating at this load without water resulted in pre-ignition. Increasing the water to fuel ratio to 1:1 enabled a 21 bar BMEP load. At 12.5 bar BMEP, the NOx emission was reduced from 13.5 g/kwh to 7.2 g/kwh with a water to fuel mass ratio of 1.5:1. In addition to solving the high NOx and pre-ignition problem, a water to fuel ratio of 2.5:1 at 16.8 bar BMEP also decreased the soot content in the exhaust by a factor of 3.5 with only a small penalty in efficiency, decreasing break thermal efficiency from 41 to 40%.



IMPACT OF NATURAL GAS DIRECT INJECTION ON THERMAL EFFICINECY IN A SPARK IGNITION ENGINE

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Page : pages

File Size : 13,78 MB

Release : 2017

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Abstract : Interest in natural gas as an internal combustion engine fuel has been renewed due to its increasing domestic availability and stable price relative to other petroleum fuel sources. Natural gas, comprised mainly of methane, allows for up to a 25% reduction in engine out CO2 emissions due to a more favorable hydrogen-to-carbon ratio, relative to traditional petroleum sources. Traditional methods of injecting natural gas can lead to poor part-load performance, as well as a power density loss at full load due to air displacement in the intake manifold. Natural gas direct injection, which allows the fuel to be injected directly into the cylinder, leads to an improvement in the in-cylinder charge motion due to the momentum of the gaseous injection event. While research performed with natural gas typically occurs at full load, the current research project focused on a part-load condition as this was most representative of real world driving conditions, becoming increasingly relevant for a downsized boosted application. The goal of this research was to further the understanding of natural gas direct injection and its resulting effect on the thermal efficiency of a GDI engine at a part-load condition. Key objectives were to measure and quantify the effects of injection location, injection timing, and exhaust gas recirculation on the thermal efficiency of the engine. A single-cylinder research engine was equipped for natural gas direct injection at Argonne National Laboratory, with detailed tests and analysis being performed. Experimental results show that the injection location played a crucial role in the mixture formation process; injecting along the tumble motion led to a greater thermal efficiency than injecting directly towards the piston due to improved mixing. The start of injection had a strong impact on the thermal efficiency, which agreed well with literature. While injecting after intake valve closure led to increased mixture flame speeds, there was a decrease in thermal efficiency due to decreased mixing time leading to increased stratification. An advanced start of injection timing led to the highest thermal efficiency, as this provided the best tradeoff between mixing time and resulting heat losses. In addition, the injection location and timing directly influenced the dilution tolerance. Injecting along the tumble motion produced the highest dilution tolerance due to the gaseous injection event amplifying the tumble motion, improving in-cylinder mixing.



Potential of Water Injection for Gasoline Engines by Means of a 3D-CFD Virtual Test Bench

Author : Antonino Vacca

Publisher : Springer Nature

Page : 202 pages

File Size : 31,86 MB

Release : 2020-12-15

Category : Technology & Engineering

ISBN : 3658327553

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Water injection is one of the most promising technologies to improve the engine combustion efficiency, by mitigating knock occurrences and controlling exhaust gas temperature before turbine. As result, the engine can operate at stoichiometric conditions over the whole engine map, even during the more power-demanding RDE cycles. Antonino Vacca presents a methodology to study and optimize the effect of water injection for gasoline engines by investigating different engine layouts and injection strategies through the set-up of a 3D-CFD virtual test bench. He investigates indirect and direct water injection strategies to increase the engine knock limit and to reduce exhaust gas temperature for several operating points.



Study of Ignition and Emissions in a Direct Injected, Compression Ignition Natural Gas Engine

Author : Ivan Gogolev

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Page : 0 pages

File Size : 24,21 MB

Release : 2016

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Natural gas direct injection and glow plug ignition assist technologies were implemented in a single-cylinder, optically-accessible engine. Initial experiments studied the effects of injector and glow plug shield geometry on ignition quality. Injector and shield geometric effects were found to be significant, with only two of 20 tested geometric combinations resulting in reproducible combustion. Further experiments explored the effects of equivalence ratio and intake pressure on ignition delay, engine performance, and exhaust emissions. Combustion was found to proceed in a stratified-premixed mode at lower equivalence ratios, and a free-mixing mode at the higher equivalence ratios. Both combustion modes resulted in high NOx emissions. Stratified-premixed combustion produced higher hydrocarbon emissions, and lower levels of particulate matter and carbon monoxide, when compared to free-mixing combustion. Higher intake pressure was found to reduce all emissions levels. This effect was largely attributed to better charge mixing achieved from pressure-driven increase in engine swirl momentum.





End-zone Water Injection as a Means of Suppressing Knock in a Spark-ignition Engine

Author : Rinaldo J. Brun

Publisher :

Page : 20 pages

File Size : 30,67 MB

Release : 1944

Category : Aerodynamics

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Summary: An investigation has been made of the effectiveness of water injection into the combustion end zone of a spark-ignition engine cylinder for the suppression of knock. Pressure-time recoreds obtained show that injection of water at 60° B.T.C. on the compression stroke at a water-fuel ratio of 0.3 rendered M-3 fuel as good as S-3 fuel from an antiknock consideration. The optimum crank angle for injection of water into the end zone was found to be critical. As the injection angle was increased beyond the optimum, the quantity of water required to suppress knock increased to 3.6 water-fuel ratio at 132° B.T.C. The water quantity could not be increased beyond 3.6 water-fuel ration because of injection-pump limitations; however, a further increase in the injection angle up to the earliest angle obtainable, which was 20° A.T.C. on the intake stroke, continuously increased the knock intensity. The engine operating conditions of the tests did not simulate those encountered in flight, especially with regard to the operating speed of 570 rpm. For this reason the results should only be regarded as of theoretical importance until further investigation has been made.