Development and Use of a Segregated-Solver for Detailed Modeling of End-Gas Detonation in a Lean-Burn Spark-Ignited Engine

2010 ◽  
Author(s):  
Scott B. Fiveland ◽  
Shriram Vijayaraghavan ◽  
Shaoping Shi ◽  
Steven W. Richardson ◽  
Michael H. McMillian ◽  
...  
Keyword(s):  
Flame Front ◽  
Engine Performance ◽  
Combustion Noise ◽  
Lean Burn ◽  
Modeling Tools ◽  
Gas Detonation ◽  
Detailed Chemistry ◽  
Auto Ignition ◽  
Spark Timing ◽  
Thermodynamic Conditions

End-gas detonation occurs in a spark-ignited engine when the advancing flame front compresses the end-gas mixture to its autoignition temperature. The rapid energy release results in shock waves which are undesirable due to resulting combustion noise and boundary layer breakdown leading to reduced engine performance and incipient engine damage. In a spark-ignited engine, end-gas knock can result from improper combinations of compression ratio, spark timing or inlet thermodynamic conditions (i.e. manifold temperature, pressure, and equivalence ratio). These variables exhibit very complex interactions, which require costly high dimensional experimental designs for proper evaluation. As a result, detailed modeling tools are needed to predict the onset of the end-gas detonation regime for engine design applications. Developing a solver to predict the end-gas detonation of gases ahead of the flame front in an operating engine is not trivial. In theory, the model would need to simultaneously resolve both the detailed fluid mechanics as well as describe the fuel decomposition using detailed chemistry. Calculations for this type can take weeks or months depending on the number of dimensions that are resolved. Since hundreds of computations may be necessary to optimize a given configuration, it is necessary to be able to not only compute the onset of auto-ignition and other parameters accurately, but efficiently. The objective of this work was to develop an efficient methodology that could be utilized to effectively predict detonation in an internal combustion spark-ignited engine. This paper presents the computational methodology, a review of the combustion tool capability, and a comparison to experiments. The work clearly demonstrates the existence of inhomogeneities in the temperature field and discusses their impact on the prediction of end-gas knock.

Evaluation of a Lean-Burn Natural Gas Engine Operating on Variable Methane Number Fuel

2011 ◽  
Author(s):  
Cory J. Kreutzer ◽  
Daniel B. Olsen ◽  
Robin J. Bremmer
Keyword(s):  
Natural Gas ◽  
High Efficiency ◽  
Engine Performance ◽  
Combustion Stability ◽  
Lean Burn ◽  
Natural Gas Engines ◽  
Spark Timing ◽  
Gas Compression ◽  
Fuel Blending ◽  
Methane Number

Wellhead gas from which pipeline natural gas originates has significant variability in composition due to natural variations in deposits. Gas quality is influenced by relative concentrations of both inert and hydrocarbon species. Gas compression engines utilizing wellhead gas as a fuel source often require significant installation time and adjustment of stock configuration due to fuel compositions that vary with time and location. Lean burn natural gas engines are chosen as wellhead compression engines for high efficiency and low emissions while minimizing the effect of variable gas composition. Ideal engine conditions are maintained by operating within the knock and misfire limits of the engine. Additional data is needed to find engine operational limitations. In this work, experimental data was collected on a Cummins GTA8.3SLB engine operating on variable methane number fuel under closed-loop equivalence ratio control. A fuel blending system was used to vary methane number to simulate wellhead compositions. NOx and CO emissions were found to increase with decreasing methane number while combustion stability remained constant. In addition, the effects of carbon dioxide and nitrogen diluents in the fuel were investigated. When diluents were present in the fuel, engine performance could be maintained by spark timing advance.

Optical Investigation of the Effects of Ethanol/Gasoline Blends on Spark-Assisted HCCI

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Mohammad Fatouraie ◽  
Margaret Wooldridge
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Engine Performance ◽  
Optical Investigation ◽  
Release Rates ◽  
High Speed Imaging ◽  
Engine Operation ◽  
Auto Ignition ◽  
Spark Timing ◽  
Combustion Properties

Spark assist (SA) has been demonstrated to extend the operating limits of homogeneous charge compression ignition (HCCI) modes of engine operation. This experimental investigation focuses on the effects of 100% indolene and 70% indolene/30% ethanol blends on the ignition and combustion properties during SA HCCI operation. The spark assist effects are compared to baseline HCCI operation for each blend by varying spark timing at different fuel/air equivalence ratios ranging from Φ = 0.4–0.5. High speed imaging is used to understand connections between spark initiated flame propagation and heat release rates. Ethanol generally improves engine performance with higher net indicated mean effective pressure (IMEPn) and higher stability compared to 100% indolene. SA advances phasing within a range of ∼5 crank angle degrees (CAD) at lower engine speeds (700 rpm) and ∼11 CAD at higher engine speeds (1200 rpm). SA does not affect heat release rates until immediately (within ∼5 CAD) prior to auto-ignition. Unlike previous SA HCCI studies of indolene fuel in the same engine, flames were not observed for all SA conditions.

scholarly journals Improving Fuel Economy and Engine Performance through Gasoline Fuel Octane Rating

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3499 ◽  
Author(s):  
José Rodríguez-Fernández ◽  
Ángel Ramos ◽  
Javier Barba ◽  
Dolores Cárdenas ◽  
Jesús Delgado
Keyword(s):  
Fuel Economy ◽  
Octane Number ◽  
High Performance ◽  
Engine Performance ◽  
Design Stage ◽  
Boost Pressure ◽  
Ambient Conditions ◽  
Auto Ignition ◽  
Spark Timing ◽  
Octane Rating

The octane number is a measure of the resistance of gasoline fuels to auto-ignition. Therefore, high octane numbers reduce the engine knocking risk, leading to higher compression threshold and, consequently, higher engine efficiencies. This allows higher compression ratios to be considered during the engine design stage. Current spark-ignited (SI) engines use knock sensors to protect the engine from knocking, usually adapting the operation parameters (boost pressure, spark timing, lambda). Moreover, some engines can move the settings towards optimized parameters if knock is not detected, leading to higher performance and fuel economy. In this work, three gasolines with different octane ratings (95, 98 and 100 RON (research octane number)) were fueled in a high-performance vehicle. Tests were performed in a chassis dyno at controlled ambient conditions, including a driving sequence composed of full-load accelerations and two steady-state modes. Vehicle power significantly increased with the octane rating of the fuel, thus decreasing the time needed for acceleration. Moreover, the specific fuel consumption decreased as the octane rating increased, proving that the fuel can take an active part in reducing greenhouse gas emissions. The boost pressure, which increased with the octane number, was identified as the main factor, whereas the ignition advance was the second relevant factor.

Addition of Exhaust Gas Recirculation Onto a Large-Bore, Two-Stroke Natural Gas Engine, and its Effects on Fuel Consumption, Emissions, and Combustion

2016 ◽  
Author(s):  
Derek Johnson ◽  
Marc Besch ◽  
Nathaniel Fowler ◽  
Robert Heltzel ◽  
April Covington
Keyword(s):  
Natural Gas ◽  
Fuel Efficiency ◽  
Thermal Inertia ◽  
Engine Performance ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Lean Burn ◽  
Spark Plug ◽  
Spark Timing ◽  
Gas Recirculation

The focus of this research was to examine the effects of adding exhaust gas recirculation (EGR) on a large bore 2-stroke, lean-burn natural gas (2SLB) engine in its stock configuration, using a previously determined optimal spark plug. EGR has been a common emissions reduction technology used for on-road gasoline, natural gas, and diesel fueled vehicles. EGR — both cooled and uncooled — is found in nearly all on-road and many off-road engines. The optimal spark plug was found in other research and it was tested with various rates of EGR. The test platform was a 1971 Cameron AJAX-E42 single-cylinder engine — common to the natural gas industry. The engine had a bore and stroke of 8.5 × 10 inches, respectively. The engine displacement was 567 cubic inches with a trapped compression ratio of 6:1. The engine was modified to include electronic spark plug timing capabilities along with a mass flow controller to ensure accurate fuel delivery. Each EGR configuration was examined at spark timings of 14, 11, and 8 CAD BTDC. Tests were conducted using an air-cooled, eddy-current power absorber at an engine speed of 525 RPM and load of 400 1b.-ft. of torque. Due to its large thermal inertia, the engine was operated for three hours prior to data collection to ensure representative and operation. In-cylinder pressure data were collected using a piezoelectric pressure transducer at increments of 0.25 CAD. Various levels of EGR and spark timing conditions were evaluated against engine performance including both regulated and unregulated exhaust emissions. Volumetric EGR rates of 2.5% showed reduced NOx emissions and improved fuel efficiency while rates of 5% did not yield NOx reductions.

Investigating realistic anode off-gas combustion in SOFC/ICE hybrid systems: mini review and experimental evaluation

2021 ◽  
pp. 146808742110583
Author(s):  
Ioannis Nikiforakis ◽  
Zhongnan Ran ◽  
Michael Sprengel ◽  
John Brackett ◽  
Guy Babbit ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
Engine Performance ◽  
High Energy ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Case Scenario ◽  
Gas Combustion ◽  
Thermodynamic Conditions ◽  
Decentralized Energy

Solid oxide fuel cells (SOFCs) have been deployed in hybrid decentralized energy systems, in which they are directly coupled to internal combustion engines (ICEs). Prior research indicated that the anode tailgas exiting the SOFC stack should be additionally exploited due to its high energy value, with typical ICE operation favoring hybridization due to matching thermodynamic conditions during operation. Consequently, extensive research has been performed, in which engines are positioned downstream the SOFC subsystem, operating in several modes of combustion, with the most prevalent being homogeneous compression ignition (HCCI) and spark ignition (SI). Experiments were performed in a 3-cylinder ICE operating in the latter modus operandi, where the anode tailgas was assimilated by mixing syngas (H2: 33.9%, CO: 15.6%, CO2: 50.5%) with three different water vapor flowrates in the engine’s intake. While increased vapor content significantly undermined engine performance, brake thermal efficiency (BTE) surpassed 34% in the best case scenario, which outperformed the majority of engines operating under similar operating conditions, as determined from the conducted literature review. Nevertheless, the best performing application was identified operating under HCCI, in which diesel reformates assimilating SOFC anode tailgas, fueled a heavy duty ICE (17:1), and gross indicated thermal efficiency ([Formula: see text]) of 48.8% was achieved, with the same engine exhibiting identical performance when operating in reactivity-controlled compression ignition (RCCI). Overall, emissions in terms of NOx and CO were minimal, especially in SI engines, while unburned hydrocarbons (UHC) were non-existent due to the absence of hydrocarbons in the assessed reformates.

Numerical study of auto-ignition propagation modes in toluene reference fuel–air mixtures: Toward a better understanding of abnormal combustion in spark-ignition engines

2018 ◽  
Vol 20 (7) ◽  
pp. 734-745 ◽  
Author(s):  
Anthony Robert ◽  
Jean-Marc Zaccardi ◽  
Cécilia Dul ◽  
Ahmed Guerouani ◽  
Jordan Rudloff
Keyword(s):  
Numerical Study ◽  
Hot Spot ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Spark Ignition ◽  
Propagation Mode ◽  
Spark Ignition Engines ◽  
Gasoline Engines ◽  
Auto Ignition ◽  
Thermodynamic Conditions

Two main abnormal combustions are observed in spark-ignition engines: knock and low-speed pre-ignition. Controlling these abnormal processes requires understanding how auto-ignition is triggered at the “hot spot” but also how it propagates inside the combustion chamber. The original theory regarding the auto-ignition propagation modes was defined by Zeldovich and developed by Bradley who highlighted different modes by considering various hot spot characteristics and thermodynamic conditions around the hot spot. Two dimensionless parameters ( ε, ξ) were then defined to classify these modes and a so-called detonation peninsula was obtained for H2–CO–air mixtures. Similar simulations as those performed by Bradley et al. are undertaken to check the relevancy of the original detonation peninsula when considering realistic fuels used in modern gasoline engines. First, chemical kinetics calculations in homogeneous reactor are performed to determine the auto-ignition delay time τi, and the excitation time τe of E10–air mixtures in various conditions. These calculations are performed for a Research Octane Number (RON 95) toluene reference fuel surrogate with 42.8% isooctane, 13.7% n-heptane, 43.5% toluene, and using the Lawrence Livermore National Laboratory (LLNL) kinetic mechanism considering 1388 species and 5935 reactions. Results point out that H2–CO–air mixtures are much more reactive than E10–air mixtures featuring much lower excitation times τe. The resulting maximal hot spot reactivity ε is thus limited which also restrains the use of the detonation peninsula for the analysis of practical occurrences of auto-ignition in gasoline engines. The tabulated ( τi, τe) values are then used to perform one-dimensional Large Eddy Simulations (LES) of auto-ignition propagation considering different hot spots and thermodynamic conditions around them. The detailed analysis of the coupling conditions between the reaction and pressure waves shows thus that the different propagation modes can appear with gasoline, and that the original detonation peninsula can be reproduced, confirming for the first time that the propagation mode can be well defined by the two non-dimensional parameters for more realistic fuels.

scholarly journals Comparison of the Emissions, Noise, and Fuel Consumption Comparison of Direct and Indirect Piezoelectric and Solenoid Injectors in a Low-Compression-Ratio Diesel Engine

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4023 ◽  
Author(s):  
Stefano d’Ambrosio ◽  
Alessandro Ferrari ◽  
Alessandro Mancarella ◽  
Salvatore Mancò ◽  
Antonio Mittica
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Compression Ratio ◽  
Fuel Injection ◽  
Engine Performance ◽  
Combustion Noise ◽  
Driving System ◽  
Performance And Emissions ◽  
Direct Acting ◽  
Engine Performance And Emissions

An experimental investigation has been carried out to compare the performance and emissions of a low-compression-ratio Euro 5 diesel engine featuring high EGR rates, equipped with different injector technologies, i.e., solenoid, indirect-acting, and direct-acting piezoelectric. The comparisons, performed with reference to a state-of-the-art double fuel injection calibration, i.e., pilot-Main (pM), are presented in terms of engine-out exhaust emissions, combustion noise (CN), and fuel consumption, at low–medium engine speeds and loads. The differences in engine performance and emissions of the solenoidal, indirect-acting, and direct-acting piezoelectric injector setups have been found on the basis of experimental results to mainly depend on the specific features of their hydraulic circuits rather than on the considered injector driving system.

scholarly journals Predicting Cycle-to-Cycle Variation With Concurrent Cycles in a Gasoline Direct Injected Engine With Large Eddy Simulations

2018 ◽  
Author(s):  
Daniel Probst ◽  
Sameera Wijeyakulasuriya ◽  
Eric Pomraning ◽  
Janardhan Kodavasal ◽  
Riccardo Scarcelli ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Engine Performance ◽  
Turnaround Time ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Cycle Variation ◽  
Spark Timing ◽  
Large Eddy ◽  
Operating Points

High cycle-to-cycle variation (CCV) is detrimental to engine performance, as it leads to poor combustion and high noise and vibration. In this work, CCV in a gasoline engine is studied using large eddy simulation (LES). The engine chosen as the basis of this work is a single-cylinder gasoline direct injection (GDI) research engine. Two stoichiometric part-load engine operating points (6 BMEP, 2000 RPM) were evaluated: a non-dilute (0% EGR) case and a dilute (18% EGR) case. The experimental data for both operating conditions had 500 cycles. The measured CCV in IMEP was 1.40% for the non-dilute case and 7.78% for the dilute case. To estimate CCV from simulation, perturbed concurrent cycles of engine simulations were compared to consecutively obtained engine cycles. The motivation behind this is that running consecutive cycles to estimate CCV is quite time-consuming. For example, running 100 consecutive cycles requires 2–3 months (on a typical cluster), however, by running concurrently one can potentially run all 100 cycles at the same time and reduce the overall turnaround time for 100 cycles to the time taken for a single cycle (2 days). The goal of this paper is to statistically determine if concurrent cycles, with a perturbation applied to each individual cycle at the start, can be representative of consecutively obtained cycles and accurately estimate CCV. 100 cycles were run for each case to obtain statistically valid results. The concurrent cycles began at different timings before the combustion event, with the motivation to identify the closest time before spark to minimize the run time. Only a single combustion cycle was run for each concurrent case. The calculated standard deviation of peak pressure and coefficient of variance (COV) of indicated mean effective pressure (IMEP) were compared between the consecutive and concurrent methods to quantify CCV. It was found that the concurrent method could be used to predict CCV with either a velocity or numerical perturbation. A large and small velocity perturbation were compared and both produced correct predictions, implying that the type of perturbation is not important to yield a valid realization. Starting the simulation too close to the combustion event, at intake valve close (IVC) or at spark timing, under-predicted the CCV. When concurrent simulations were initiated during or before the intake even, at start of injection (SOI) or earlier, distinct and valid realizations were obtained to accurately predict CCV for both operating points. By simulating CCV with concurrent cycles, the required wall clock time can be reduced from 2–3 months to 1–2 days. Additionally, the required core-hours can be reduced up to 41%, since only a portion of each cycle needs to be simulated.

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