Experimental Study of Methane Fuel Oxycombustion in a Spark-Ignited Engine

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Andrew Van Blarigan ◽  
Darko Kozarac ◽  
Reinhard Seiser ◽  
Robert Cattolica ◽  
Jyh-Yuan Chen ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Conversion Efficiency ◽  
Compression Ratio ◽  
Peak Performance ◽  
Working Fluid ◽  
Fuel Conversion ◽  
Specific Heats ◽  
Spark Timing ◽  
Performance Conditions ◽  
Gas Recirculation

An experimental investigation of methane fuel oxycombustion in a variable compression ratio, spark-ignited piston engine has been carried out. Compression ratio, spark-timing, and oxygen concentration sweeps were performed to determine peak performance conditions for operation with both wet and dry exhaust gas recirculation (EGR). Results illustrate that when operating under oxycombustion conditions an optimum oxygen concentration exists at which fuel-conversion efficiency is maximized. Maximum conversion efficiency was achieved with approximately 29% oxygen by volume in the intake for wet EGR, and approximately 32.5% oxygen by volume in the intake for dry EGR. All test conditions, including air, were able to operate at the engine's maximum compression ratio of 17 to 1 without significant knock limitations. Peak fuel-conversion efficiency under oxycombustion conditions was significantly reduced relative to methane-in-air operation, with wet EGR achieving 23.6%, dry EGR achieving 24.2% and methane-in-air achieving 31.4%. The reduced fuel-conversion efficiency of oxycombustion conditions relative to air was primarily due to the reduced ratio of specific heats of the EGR working fluids relative to nitrogen (air) working fluid.

scholarly journals Controlled End Gas Auto Ignition With Exhaust Gas Recirculation on a Stoichiometric, Spark Ignited, Natural Gas Engine

2020 ◽  
Author(s):  
Scott Bayliff ◽  
Bret Windom ◽  
Anthony Marchese ◽  
Greg Hampson ◽  
Jeffrey Carlson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Compression Ratio ◽  
High Efficiency ◽  
Exhaust Gas Recirculation ◽  
Peak Performance ◽  
Stable Operation ◽  
Exhaust Gas ◽  
Ignition Timing ◽  
Auto Ignition ◽  
Gas Recirculation

Abstract The goal of this study is to address fundamental limitations to achieving diesel-like efficiencies in heavy duty on-highway natural gas (NG) engines. Engine knock and misfire are barriers to pathways leading to higher efficiency engines. This study explores enabling technologies for development of high efficiency stoichiometric, spark ignited, natural gas engines. These include design strategies for fast and stable combustion and higher dilution tolerance. Additionally, advanced control methodologies are implemented to maintain stable operation between knock and misfire limits. To implement controlled end-gas autoignition (C-EGAI) strategies a Combustion Intensity Metric (CIM) is used for ignition control with the use of a Woodward large engine control module (LECM). Tests were conducted using a single cylinder, variable compression ratio, cooperative fuel research (CFR) engine with baseline conditions of 900 RPM, engine load of 800 kPa indicated mean effective pressure (IMEP), and stoichiometric air/fuel ratio. Exhaust gas recirculation (EGR) tests were performed using a custom EGR system that simulates a high pressure EGR loop and can provide a range of EGR rates from 0 to 40%. The experimental measurements included the variance of EGR rate, compression ratio, engine speed, IMEP, and CIM. These five variables were optimized through a Modified BoxBenken design Surface Response Method (RSM), with brake efficiency as the merit function. A positive linear correlation between CIM and f-EGAI was identified. Consequently, CIM was used as the feedback control parameter for C-EGAI. As such, implementation of C-EGAI effectively allowed for the utilization of high EGR rates and CRs, controlling combustion between a narrower gap between knock and lean limits. The change from fixed to parametric ignition timing with CIM targeted select values of f-EGAI with an average coefficient of variance (COV) of peak pressure of 5.4. The RSM efficiency optimization concluded with operational conditions of 1080 RPM, 1150 kPa IMEP, 10.55:1 compression ratio, and 17.8% EGR rate with a brake efficiency of 21.3%. At this optimized point of peak performance, a f-EGAI for C-EGAI was observed at 34.1% heat release due to auto ignition, a knock onset crank angle value of 10.3° aTDC and ignition timing of −24.7° aTDC. This work has demonstrated that combustion at a fixed f-EGAI can be maintained through advanced ignition control of CIM without experiencing heavy knocking events.

Engine-Control Impact on Energy Balances for Two-Stroke Engines for 10–25 kg Remotely Piloted Aircraft

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Joseph K. Ausserer ◽  
Marc D. Polanka ◽  
Paul J. Litke ◽  
Jacob A. Baranski
Keyword(s):  
Conversion Efficiency ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Rapid Expansion ◽  
Combustion Stability ◽  
Fuel Conversion ◽  
Absolute Increase ◽  
Spark Timing ◽  
Remotely Piloted Aircraft ◽  
Energy Pathways

The rapid expansion of the market for remotely piloted aircraft (RPA) includes a particular interest in 10–25 kg vehicles for monitoring, surveillance, and reconnaissance. Power-plant options for these aircraft are often 10–100 cm3 internal combustion engines (ICEs). The present study builds on a previous study of loss pathways for small, two-stroke engines by quantifying the trade space among energy pathways, combustion stability, and engine controls. The same energy pathways are considered in both studies—brake power, heat transfer from the cylinder, short circuiting, sensible exhaust enthalpy, and incomplete combustion. The engine controls considered in the present study are speed, equivalence ratio, combustion phasing (ignition timing), cooling-air flow rate, and throttle. Several options are identified for improving commercial-off-the-shelf (COTS)-engine efficiency and performance for small, RPA. Shifting from typical operation at an equivalence ratio of 1.1–1.2 to lean operation at an equivalence ratio of 0.8–0.9 results in a 4% (absolute) increase in fuel-conversion efficiency at the expense of a 10% decrease in power. The stock, linear timing maps are excessively retarded below 3000 rpm, and replacing them with custom spark timing improves ease of engine start. Finally, in comparison with conventional-size engines, the fuel-conversion efficiency of the small, two-stroke ICEs improves at throttled conditions by as much as 4–6% (absolute) due primarily to decreased short-circuiting. When no additional short-circuiting mitigation techniques are employed, running a larger engine at partial throttle may lead to an overall weight savings on longer missions. A case study shows that at 6000 rpm, the 3W-55i engine at partial throttle will yield an overall weight saving compared to the 3W-28i engine at wide-open throttle (WOT) for missions exceeding 2.5 h (at a savings of ∼5 g/min).

Design, Actuation, Experimental Setup and Testing of a 4-Cylinder Gasoline Spark Ignited Variable Compression Ratio Engine

2020 ◽  
Author(s):  
Tyler Miller ◽  
Joel Duncan ◽  
William Hensley ◽  
John Beard ◽  
Jeremy Worm ◽  
...  
Keyword(s):  
Conversion Efficiency ◽  
Compression Ratio ◽  
Fuel Mixture ◽  
Relative Increase ◽  
Concept Design ◽  
Linkage Mechanism ◽  
Fuel Conversion ◽  
Indicated Mean Effective Pressure ◽  
Base Engine ◽  
Engine Testing

Abstract The thermal efficiency of an Otto cycle engine is directly related to the compression ratio (CR). However, in a spark-ignited engine, the CR is often restricted by full load knock, thus limiting part load efficiency. A proof of concept design and experimental study has been conducted on a 4-cylinder naturally aspirated spark-ignited (SI) engine whereby a four-bar linkage mechanism has been implemented to vary the CR. The base engine selected was a production 2.0L GM-LNF SI 4-cylinder engine with a stock CR of 9.2:1 and with a bore and stroke of 86mm and 86mm, respectively. The engine was modified to allow the centerline axis of rotation of the crankshaft to translate in an arc about a fixed point. With the use of the four-bar mechanism, and larger dome volume pistons, a range of 8:1 to 11.5:1 CR was achieved. The prototype VCR engine was tested and analyzed at three different CR’s at a fixed load of 600 kPa net indicated mean effective pressure gross (IMEPGROSS) at an engine speed of 1000 revolutions per minute (RPM). At this condition, a sweep of combustion phasing was conducted. with a stoichiometric air to fuel mixture for each case. The CR’s selected for engine testing were 8.7:1, 10.2:1, and 11.1:1. The processed data includes averaged cycle analysis of each of the test conditions including combustion phasing, combustion duration, and cycle variation. The combustion data was also analyzed to determine overall heat release, indicated gross, net, pumping mean effective pressures, and indicated fuel conversion efficiency for each of the CR’s. The studies show an indicated fuel conversion efficiency of 31.2% for the 8.7:1 CR. As the CR was increased to 10.2:1 and 11.1:1 the relative increase in efficiency was 7.1% and 9.7% respectively at MBT combustion phasing.

Ignition delays in diesel combustion and intake gas conditions

2017 ◽  
Vol 19 (8) ◽  
pp. 805-812 ◽  
Author(s):  
Hideyuki Ogawa ◽  
Akihiro Morita ◽  
Katsushi Futagami ◽  
Gen Shibata
Keyword(s):  
Oxygen Concentration ◽  
Compression Ratio ◽  
Ignition Delay ◽  
Cetane Number ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Diesel Combustion ◽  
Gas Temperature ◽  
Gas Recirculation ◽  
Oxygen Concentrations

Ignition delays in diesel combustion under several intake gas conditions, including different oxygen concentrations changed with exhaust gas recirculation quantities and different intake gas temperatures, were measured for four cetane numbers and three compression ratios in a single-cylinder, naturally aspirated, direct injection diesel engine (bore: 110 mm, stroke: 106 mm, and stroke volume: 1007 cm3). The engine has a common rail fuel injection system which can be set to optional injection timings and has an injector with a needle lift sensor to accurately estimate the injection timing. The intake oxygen concentrations were set by the quantity of exhaust gas recirculation gas, and the intake gas temperatures were changed with a water-cooled exhaust gas recirculation cooler and an electric heater in the intake pipe. Three compression ratios, 16.7, 18.0, and 21.3, were established with three pistons of different cavity volumes. Four fuels with different cetane numbers, 32 (CN32), 45 (CN45), 57 (CN57), and 78 (CN78), consisting of normal and isoparaffins, were examined for the three compression ratios, and the influence of exhaust gas recirculation and intake gas temperature is discussed for 12 combinations of compression ratios and cetane numbers. The results showed that the ignition delay increases linearly with the 1.67 power of the decrease in the intake oxygen concentration changed with cooled exhaust gas recirculation at the same cetane number and the same compression ratio. The ignition delay increases linearly with lowering intake gas temperatures, and the degree of increase in the ignition delay is more significant with lower cetane number fuels and lower compression ratios. Under practical conditions with the intake oxygen concentration between 21% and 11% and the intake gas temperature between 40°C and 100°C, the changes in ignition delays with the intake oxygen concentration are more significant than the changes with intake gas temperature. The ignition delay increases linearly with lowering compression ratios, and the degree of increase in the ignition delay with reductions in the compression ratio is larger in the cases with lower intake oxygen concentrations and lower cetane number fuels. The ignition delays at the higher compression ratios are significantly shorter than with the lower compression ratios in the case of the same in-cylinder gas temperature at top dead center due to higher in-cylinder gas pressures. The degree of increase in the ignition delay with lower cetane numbers is more significant at lower intake oxygen concentrations and lower compression ratios, and the ignition delay decreases linearly with the 0.25 power of the increase in cetane numbers.

Experimental Study of Methane Fuel Oxycombustion in an SI Engine

2012 ◽  
Author(s):  
Andrew Van Blarigan ◽  
Darko Kozarac ◽  
Reinhard Seiser ◽  
Robert Cattolica ◽  
Jyh-Yuan Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Compression Ratio ◽  
Thermal Efficiency ◽  
Combustion Efficiency ◽  
Working Fluid ◽  
Si Engine ◽  
Lower Efficiency ◽  
Working Fluids ◽  
Spark Timing

An experimental investigation of the thermal efficiency, combustion efficiency, and CoV IMEP, of methane fuel oxycombustion in an SI engine has been carried out. Compression ratio, spark-timing, and oxygen concentration were all varied. A variable compression ratio SI engine was operated on both wet and dry EGR working fluids, with results illustrating that the efficiency of the engine operating with a large amount of EGR was significantly reduced relative to methane-in-air operation over all oxygen concentrations and compression ratios. The maximum thermal efficiency of wet EGR, dry EGR, and air was found to be 23.6%, 24.2%, and 31.4%, respectively, corresponding to oxygen volume fractions of 29.3%, 32.7% and 21%. Combustion efficiency was above 98% for wet EGR and approximately 96% for dry EGR. CoV IMEP was low for both cases. The much lower efficiency of both EGR cases relative to air is primarily a result of the reduced specific-heat ratio of the EGR working fluids relative to air working fluid.

Investigating anode off-gas under spark-ignition combustion for SOFC-ICE hybrid systems

2021 ◽  
pp. 146808742110169
Author(s):  
Zhongnan Ran ◽  
Jon Longtin ◽  
Dimitris Assanis
Keyword(s):  
Hybrid Systems ◽  
Conversion Efficiency ◽  
Combustion Engine ◽  
Spark Ignition ◽  
Combustion Efficiency ◽  
Experimental Investigations ◽  
Fuel Conversion ◽  
Generation Plant ◽  
Complementary Role ◽  
Power Generation Plant

Solid oxide fuel cell – internal combustion engine (SOFC-ICE) hybrid systems are an attractive solution for electricity generation. The system can achieve up to 70% theoretical electric power conversion efficiency through energy cascading enabled by utilizing the anode off-gas from the SOFC as the fuel source for the ICE. Experimental investigations were conducted with a single cylinder Cooperative Fuel Research (CFR) engine by altering fuel-air equivalence ratio (ϕ), and compression ratio (CR) to study the engine load, combustion characteristics, and emissions levels of dry SOFC anode off-gas consisting of 33.9% H2, 15.6% CO, and 50.5% CO2. The combustion efficiency of the anode off-gas was directly evaluated by measuring the engine-out CO emissions. The highest net-indicated fuel conversion efficiency of 31.3% occurred at ϕ  = 0.90 and CR = 13:1. These results demonstrate that the anode off-gas can be successfully oxidized using a spark ignition combustion mode. The fuel conversion efficiency of the anode tail gas is expected to further increase in a more modern engine architecture that can achieve increased burn rates in comparison to the CFR engine. NOx emissions from the combustion of anode off-gas were minimal as the cylinder peak temperatures never exceeded 1800 K. This experimental study ultimately demonstrates the viability of an ICE to operate using an anode off-gas, thus creating a complementary role for an ICE to be paired with a SOFC in a hybrid power generation plant.

Optimization of a Novel Combined Power/Refrigeration Thermodynamic Cycle

Solar Energy ◽  
2002 ◽  
Author(s):  
Shaoguang Lu ◽  
D. Yogi Goswami
Keyword(s):  
Waste Heat ◽  
Thermodynamic Cycle ◽  
Cycle Performance ◽  
Working Fluid ◽  
Second Law ◽  
Optimum Conditions ◽  
Ambient Temperatures ◽  
Reduced Gradient ◽  
Generalized Reduced Gradient ◽  
Performance Conditions

A novel combined power/refrigeration thermodynamic cycle is optimized for thermal performance in this paper. The cycle uses ammonia-water binary mixture as a working fluid and can be driven by various heat sources, such as solar, geothermal and low temperature waste heat. It could produce power as well as refrigeration with power output as a primary goal. The optimization program, which is based on the Generalized Reduced Gradient (GRG) algorithm, can be used to optimize for different objective functions. Examples that maximize second law efficiency, work output and refrigeration output are presented, showing the cycle may be optimized for any desired performance parameter. In addition, cycle performance over a range of ambient temperatures was investigated. It was found that for a source temperature of 360K, which is in the range of flat plate solar collectors, both power and refrigeration outputs are achieved under optimum conditions. All performance parameters, including first and second law efficiencies, power and refrigeration output decrease as the ambient temperature goes up. On the other hand, for a source of 440K, optimum conditions do not provide any refrigeration. However, refrigeration can be obtained even for this temperature under non-optimum performance conditions.

Development of Coal Partial Gasification and Combustion System

2004 ◽  
Author(s):  
Yaoxin Liu ◽  
Libin Yang ◽  
Mengxiang Fang ◽  
Guanyi Chen ◽  
Zhongyang Luo ◽  
...  
Keyword(s):  
Conversion Efficiency ◽  
Pilot Plant ◽  
Sulfur Removal ◽  
Test Facility ◽  
Molar Ratio ◽  
Fuel Conversion ◽  
Heating Value ◽  
Pilot Plant Test ◽  
Plant Test ◽  
Partial Gasification

A new system using combined coal gasification and combustion has been developed for clean and high efficient utilization of coal. Following are the processes. The coal is first partially gasified and the produced fuel gas is then used for industrial purpose or as a fuel for a gas turbine. The char residue from the gasifier is burned in a circulating fluidized bed combustor to generate steam for power generation. For having the experimental investigation, a 1MW pilot plant test facility has been erected. Experiments on coal partial gasification with air, and recycle gas have been made on the 1 MW pilot plant test facility. The results show that, with air as gasification agent, the system can produce 4–5MJ/Nm3 low heating value dry gas and fuel conversion efficiency attains 50–70% in the gasifier, and residue 20–40% converted in the combustor and total conversion efficiency in the system is over 90%. In the gasifier, the carbon conversion efficiency increases with the bed temperature and the air blown temperature. CaCO3 has an effective effect for sulfur removal in the gasifier. The sulfur removal efficiency attains 85% with Ca/S molar ratio 2.5. The system can produce 12–14MJ/Nm3 middle heating value day gas by using high temperature circulation solid as heat carrier and recycle gas or steam as gasification media, but the fuel conversion efficiency only attain 30–40% in the gasifier and most of fuel energy is converted in the combustor. CaCO3 has an obvious effect on tar cracking and H2S removal. The sulfur removal efficiency attains 80% with Ca/S molar ratio 2.5.

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