Browse Topic: Ignition timing

Items (796)

Enhancements in Hydrogen Low Pressure Injection on Small Two-Stroke Engines

2024-32-004704/18/2025

The use of small 2-stroke crankcase scavenged engines running on hydrogen is very attractive for low power rates, when low cost and compact dimensions are the fundamental design constraints. However, achieving optimal performance with hydrogen fuel presents challenges, including uneven air-fuel mixtures, fuel losses, and crankcase backfiring. This research focuses on a small 50cc 2-stroke loop-scavenged engine equipped with a patented Low-Pressure Direct Injection (LPDI) system, modified for hydrogen use. Experimental results demonstrate performance comparable to the gasoline counterpart, but further optimizations are needed. Consequently, CFD-3D simulations are employed to analyses the injection process and guide engine development. The numerical analysis focuses on a fixed operating condition: 6000 rpm, Wide Open Throttle (WOT), with a slightly lean mixture and injection pressure fixed at 5 bar. A numerical model of the entire engine is set up with the primary objective of improving

Caprioli, Stefano, Schoegl, Oliver, Oswald, Roland, Kirchberger, Roland, Mattarelli, Enrico, Rinaldini, Carlo Alberto

Studying the Lean Burn Operation in Two-Wheelers to Increase Fuel Efficiency and Investigate the Use of Lean NOx Trap Catalyst (LNT) for Lean Burn System

2024-32-005804/18/2025

This study offers an overview of the impact of lean burn technology in two-wheeler vehicles, specifically concentrating on enhancing the fuel economy and addressing the challenges associated with its adoption. Lean burn systems, characterized by a fuel-air mixture with a higher air content than stoichiometric ratio. The study focuses on technology which meets stringent emission standards while enabling the optimization of fuel efficiency. The lean burn system employs strategies to optimize air-fuel ratio using electronic fuel injection, ignition timing control, and advanced engine control algorithms like - updated torque modulation control algorithm for drivability, lambda control algorithm for rich and lean switch and NOx modelling algorithm for LNT catalyst efficiency tracking. The challenges related to lean burn systems, includes issues related to combustion stability, nitrogen oxide (NOx) emissions, and their impact on drivability, is summarized in the study. Mitigation strategies

Somasundaram, Karthikeyan, Sivaji, Purushothaman, John Derin, C, Vishal, Karwa, Manoj Kumar, S, Maynal, Rajesh

Model-Based Calibration of ECU for Small Motorcycles

2024-32-002404/18/2025

To deal with the emission regulations it is necessary to produce ECU control maps that maintain balance of emissions of HC, NOX, CO, engine power output and fuel consumption during the motorcycle development. We have recently introduced the Model-Based Calibration (hereafter as MBC) for calibration of ECU control maps for small motorcycles, which share a big chunk of the market. When introducing we aimed at such a method that can simulate stable temperature conditions necessary for the measurement in order to make it applicable to air-cooled engines predominantly used in small motorcycles. To decrease performance difference between the prototype and the mass-production, the newly developed method allows rewriting of control parameters such as the ignition timing using the mass-production ECU. The fully automated data acquisition along with the application of MBC permits continuous test operations even in nighttime and on holidays. Moreover, the MBC flow was made such a manner that

Fujiwara, Hirofumi, Maruyama, Atsushi, Kasai, Yoshiyuki

Experimental Study of Piston temperature profile with respect to varying engine parameters – Using Telemetry Method

2024-26-034101/16/2024

As emissions standards become more stringent, OEMs are pushing engines to run on leaner fuel mixtures, which puts increased thermal stress on components, particularly pistons, causing them to operate at higher temperatures. This requires more robust design and rigorous testing of components. Telemetry methods offer accurate and real-time feedback, allowing designers to test components at various operating conditions, providing more flexibility than other traditional methods. Piston temperature measurement is a critical aspect of engine development because it directly affects engine performance and durability. Among the various techniques available for this purpose, telemetry methods have gained considerable attention in recent years. This method involves integrating temperature sensors and transmitter on the piston, which transmit temperature data wirelessly to a receiver outside the engine. In this paper, we evaluate the impact of coolant temperatures, valve timing, ignition timing

Pandey, Ram Krishan, KUMAR, ATUL, Jangra, Sumit

Research on Injection Characteristics of Marine Ammonia Fuel Injector under Wide Temperature Range

2023-01-701710/30/2023

Ammonia fuel is typically characterized by low viscosity, low flash point, and non-flammability. This means that fuel characteristics and operational requirements significantly deviate from those of conventional fuels, requiring a significant technical upgrade to the existing fuel supply and injection systems. This research involves a numerical analysis of ammonia utilization in high-pressure direct injection. Considering the non-isothermal compressibility of the fuel flow process, the fluid properties in the model are specifically defined based on the physical properties of the ammonia fuel. The injection performance of ammonia fuel was studied, including comparing the injection performance of ammonia fuel with conventional diesel fuel under typical operating conditions in the injector, and exploring the injection characteristics of ammonia fuel injector under a wide fuel temperature range. The results of ammonia injection indicate that the response characteristics of liquid ammonia

Li, Meisi, Fan, Liyun, Wei, Yunpeng, Mao, Yuntao

Pre-investigations on Reactive and Partially-Dry Exhaust Gas Recirculation for a Naturally Aspirated Gas Engine

2023-01-121206/26/2023

Given its ability to be combined with the three-way catalyst, the stoichiometric operation is significantly more attractive than the lean-burn process, when considering the increasingly severe NOx limit for cogeneration gas engines. However, the high temperature of the stoichiometric combustion results in increased wall heat losses, restricted combustion phasings (owing to knock tendency) and thus efficiency penalties. To lower the temperature of the stoichiometric combustion and thus improve the engine efficiency, exhaust gas recirculation (EGR) is one of the most effective means. Nevertheless, the dilution with EGR has much lower tolerance level than with excess air, which leads to a consequent drop in the thermal efficiency. In this regard, reducing the water vapor concentration in the recirculated exhaust gas and increasing the EGR reactivity are two potential measures that may extend the mixture dilution limit and result in engine efficiency benefits. Here, the reactive exhaust

Beltaifa, Youssef, Kettner, Maurice, Eilts, Peter, Ruchel, Bosse, Fröstl, Sebastian

Combustion Stability Investigation of Ethanol Blends (E5, E10) in a Twin-cylinder CI Engine

2022-01-061203/29/2022

Ethanol can be easily derived from waste agricultural resources such as plant biomass and forest residue, ease of production increases its possibility of usage locally in agricultural engine and transport vehicles. To explore the combustion stability, combustion behavior and emissions parameters of ethanol in existing CI engine, a laboratory experiment was carried out, using CRDI Diesel engine at three different loading condition (no-load, 20 Nm and 40 Nm) with three different test fuel (D100, E05 and E10). The maximum in-cylinder pressure and HRR were increased with ethanol addition into diesel. Ethanol’s higher heat of vaporization promotes cooling effects that prolong ignition time. Inherent oxygen and lower viscosity of ethanol improve the combustion phenomena, which results in the lower cycle to cycle variation and lower Coefficient of variation (COV) for in-cylinder pressure. Combustion stability was increased with the addition of ethanol. E05 is showing the lowest COV value (1-3

Sahu, Tomesh, Kshatri, Ravindra, Kumar, Atul, Shukla, Pravesh Chandra

Effect of Chemical Structure of Substituted Phenol Fuel Additives on Ignition Delay of a Toluene Reference Fuel

2022-01-062303/29/2022

Chemical structure, equivalence ratio, temperature, pressure, and dilution are prominent properties of fuel-oxidizer mixtures that affect combustion. In Internal Combustion engines, these properties are critical to consider as increasing engine performance requirements drive the need for high octane number fuels in Spark Ignition engines. One method of increasing a fuel’s octane number is by using octane-enhancing additives. Aromatics have long been used in gasoline for their octane-enhancing properties, therefore this study focuses on how the addition of aromatics at 2% by volume affects the ignition characteristics of a Toluene Reference Fuel. Simulations have found that substituted phenols may be promising octane-enhancing additives, and that the location of each methyl group on the aromatic ring may have a significant affect during combustion. This research measures the Ignition Delay Time, using a Rapid Compression Machine; and the Laminar Flame Speed, using a Constant Volume

Trombley, Grace, Wadkar, Chaitanya, Duva, Berk Can, Toulson, Elisa

Development of Multiple Injection Strategy for Gasoline Compression Ignition High Performance and Low Emissions in a Light Duty Engine

2022-01-055203/29/2022

Increasing regulatory demand to reduce CO2 emissions has led to a focus on the development of novel combustion modes such as gasoline compression ignition (GCI). It has been shown by others that GCI can improve the overall engine efficiency while achieving soot and NOx emissions targets. In comparison with diesel fuel, gasoline has a higher volatility and has more resistance to autoignition, therefore, it has a longer ignition delay time which facilitates better mixing of the air-fuel charge before ignition. In this study, a GCI combustion system has been tested using a Hyundai 2.2L engine as part of a US Department of Energy funded project. For this purpose, a multiple injection strategy was developed to improve the pressure rise rates and soot emission levels for the same engine out NOx emissions. The effect of start of injection timing and fuel quantity split between injections are reported for double and triple-injection strategies with impact on cylinder pressure and heat release

Zyada, Antowan, Zoldak, Philip, Naber, Jeffrey

Engine-Out Measurements and In-Cylinder Imaging of Cold-Start Particulate and Gaseous Emissions in a Single-Cylinder DISI Engine

2022-01-052203/29/2022

Strategies to mitigate cold-start emissions are critical to meet stringent standards for particulate and regulated gaseous emissions from direct injection spark ignition (DISI) engines. The objective of the current work was to establish an experimental protocol for cold-start studies and to identify the in-cylinder phenomena important during engine warming in terms of engine power and stability and engine-out particulates, NOx, and unburned hydrocarbon emissions. Metal-engine experiments were conducted at T = 20 oC to quantify the sensitivity of the performance of a single-cylinder engine to timing of a strategy using two injection events per power cycle and late spark ignition. The results showed strong sensitivity to the timing of the second injection event and weak sensitivity to the timing of the first injection. Complementary high-speed imaging experiments were conducted with the same engine where the fuel spray and combustion characteristics were visualized during cold-start

Gutierrez, Luis G., Wooldridge, Margaret S., Petersen, Benjamin R., Wooldridge, Steven T.

Prediction of ECN spray-A characteristics using machine learning

2022-01-059803/29/2022

Flame lift-off length (FLOL), ignition delay time (IDT), liquid length (LL), and Soot are essential parameters defining spray combustion characteristics. They help in understanding the combustion dynamics and validating the spray and combustion models for numerical simulations. However, obtaining extensive data from experiments is both a costlier and time-consuming task. Machine learning (ML) models have advanced to the point where they could create efficient models that could be used as surrogates for experiments. In this study, five different ML algorithms have been trained using the experimental dataset available through the engine combustion network (ECN) community. A novel genetic algorithm-based hyperparameter optimization code has been used to optimize the models to improve prediction accuracy. The model performances were compared, and the better model was chosen as an experimental surrogate to predict FLOL, IDT, LL, and Soot.

Mohan, Balaji, Badra, Jihad

Describing the Auto-Ignition Quality in Small, Air Cooled, Two Stroke Engines

2022-32-006301/09/2022

Auto-ignition quality is one of the most important properties in gasoline. Auto-ignition quality is today described by the Motor Octane Number (MON) and the Research Octane Number (RON). For modern, light duty, gasoline engines it has been quite well established that RON is the most accurate number. However, no study has been performed on hand held forest and garden products, such as chainsaws. Is the auto-ignition quality best described in the same way for these engines as for light duty engines? In this paper, a matrix of six different fuels with different combinations of MON and RON values were tested on a Husqvarna 550 XP Mark II, a modern air cooled, sequential stratified scavenging 2-stroke chainsaw engine. Ignition timing sweeps were performed and knock limited spark advance (KLSA) were calculated. Then the data has been analyzed with a multi-variate analysis of KLSA against both MON and RON to try to determine how MON and RON should be combined to best describe the anti-knock

Risberg, Per, Elm, Thomas, Bergman, Mikael, Hellquist, Fredrik, Karvo, Anna, Tripathi, Rupali

Effects of Ignition Timing and Fuel Chemical Composition on Autoignition Behavior and Knocking Characteristics under Lean Conditions

2022-32-007001/09/2022

This study focused on autoignition behavior and knocking characteristics. Using an optically accessible engine, autoignition behavior was observed over the entire bore area, and the relationship between autoignition behavior and knocking characteristics was clarified on the basis of visualized combustion images and frequency analysis of the in-cylinder pressure waveform. In addition, chemical kinetic simulations were used to investigate the effects of different fuel chemical compositions on combustion and autoignition characteristics under equivalent octane ratings. The results showed that the rate of autoignition development has a significant effect on knocking intensity. In addition, the ρ1,0 mode is the dominant vibration mode caused by knocking, regardless of the location of autoignition. It can be inferred that strong knocking is caused by multiple vibration modes. Furthermore, chemical kinetic simulation results and experimental data show that different fuel chemical compositions

Shirane, Kaede, Kimura, Toshiki, Nakamura, Sota, Furusyo, Karin, Iijima, Akira

Extension of the Lean Limit of Gasoline Engines Under Part Load by Using Hot Surface Assisted Spark Ignition (HSASI)

2022-32-005101/09/2022

Charge dilution by lean-burn is one way to increase the efficiency of spark ignition engines while reducing NOx emissions. This work focuses on increasing the flammability of lean mixtures inside a passive pre-chamber spark plug by elevating its temperature with the help of a controllable hot surface integrated into the pre-chamber. Thus, an extension of the lean limit under part load is aimed for. A pre-chamber spark plug prototype with an integrated, controllable glow plug was developed, called Hot Surface Assisted Spark Ignition (HSASI). Experimental investigations were conducted on a single-cylinder engine at the Karlsruhe University of Applied Sciences. Operating modes with an active glow plug (HSASI) and a non-active glow plug were compared. The lean limit for both operation modes were determined under part load. NOx, CO and THC emissions were measured for different air-fuel equivalence ratios λ. The lean limit is extended by more than 0.1 in λ at low loads with HSASI operation

Holzberger, Sascha, Kettner, Maurice, Kirchberger, Roland

Combustion Performance of Methane Fermentation Gas with Hydrogen Addition under Various Ignition Timings

2022-32-004301/09/2022

Hydrogen (H2) addition is widely used for natural gas combustion to improve the engine efficiency. However, less attention was paid on the various ignition timings for the maximum brake torque (MBT) and brake thermal efficiency (BTE). In order to check the ignition timing effect, experiments were performed in a spark ignition engine with engine speed fixed on 1500 revolutions per minute (rpm). Firstly, CH4 was only used for combustion with excess air ratio (λ) changing from 0.8 to 1.4. Then, co-combustion of 50 vol% CH4 and 50 vol% CO2 was checked to simulate methane fermentation gas. Finally, H2 was added with volume percentage varying from 5% to 20%. Among these discussions, torque, brake mean effective pressure (BMEP), BTE and cylinder pressure were evaluated. Based on the results, high efficiency can be achieved by advancing the ignition timing with H2 addition at λ=1.4. However, with H2 addition, the ignition timing should be retarded to obtain higher BTE. At the lean-burn

Luo, Hongliang, Jin, Yu, An, Yanzhao, Matsumura, Yukihiko, Ichikawa, Takayuki, Kim, Wookyung, Nakashimada, Yutaka, Nishida, Keiya

Tooth Time-Based Engine Misfire Detection Index for Multicylinder Engines of Vehicles Not Affected by Various Deviations between Cylinders

03-15-03-002109/28/2021

This article proposes a new misfire detection index, the ΔGap slope, for a four-cylinder engine. However, the proposed index is not limited to four-cylinder engines. The ΔGap slope uses the tooth time measured using the existing crankshaft position sensor; therefore, an additional sensor is not required, which makes it economical. The ΔGap slope is defined as the difference between the gap slopes of the same cylinder for two adjacent cycles. Various factors that cause deviations in gap slopes between cylinders can be eliminated in the process of determining the difference between two gap slopes. Hence, in contrast with the existing engine roughness method, the ΔGap slope has the advantage of not requiring compensation for deviations between the cylinders. The conventional gap slope method must use different sets of thresholds for each cylinder located at the same position on the sensor wheel, which results in multiple thresholds being applied. In contrast, the ΔGap slope can use the

Auto-ignition and Anti-Knock Evaluation of Dicyclopentadiene-PRF and TPRF Blends

2021-01-116009/21/2021

The increasing demand for high-octane fuels is pushing the combustion research towards investigating new potential fuels and octane boosters. In addition to their high-octane, those additives should be environmentally friendly. In this study, the anti-knock properties of Dicyclopentadiene (DCPD) as an additive to primary reference fuels (PRF) and toluene primary reference fuels (TPRF) have been investigated. The Research octane number (RON) and Motor octane number (MON) were measured using Cooperative Fuels Research (CFR) engine for four different fuel blends; PRF 60 + 10% DCPD, PRF 60 + 20% DCPD, PRF 70 + 10% DCPD and TPRF 70 + 10% DCPD. In addition, homogenous charge compression ignition (HCCI) was also performed using the CFR engine to show the effect of DCPD on suppressing low temperature chemistry of reference fuels. Moreover, the ignition delay times of these mixtures were measured in the rapid compression machine (RCM) at 20 bar and stoichiometric mixtures over a temperature

Al-Khodaier, Mohannad

Experimental Investigation of Cyclic Variation of Heat Release Dynamics of HCCI Combustion Engine

2021-01-117009/21/2021

Homogenous charge compression ignition (HCCI) combustion emerged as a potential technique for reducing automotive pollution. Controlling the combustion timing at different engine operating conditions is one of the major challenges for the commercial application of HCCI combustion engines. To control HCCI ignition timing, it is often necessary to know the characteristics of HCCI cyclic variations. In this study, cyclic combustion variations in an HCCI engine are analyzed. Combustion stability and cycle-to-cycle variations of HCCI combustion parameters were investigated on a modified four-stroke diesel engine. The experiments were conducted by varying intake air temperatures and relative air-fuel ratios at constant engine speed. In the steady-state engine operating condition, in-cylinder pressure signals of 2000 consecutive engine combustion cycles are acquired for each test condition. From this large volume of experimental data collected, cyclic variations of various combustion

Singh, Ajay, Maurya, Rakesh Kumar

Evaporation Characteristics of Fuels for Low-Temperature Combustion Engine Application

2021-01-121009/21/2021

The research on reducing emissions from automotive engines through modifications in the combustion mode and the fuel type is gaining momentum because of increasing contribution to the global warming potential by the transport sector. The combustion and emission formation in the advanced low-temperature combustion (LTC) engine strategies are highly sensitive to the fuel molecular composition and its properties. As the ignition timing in LTC is primarily controlled by the fuel chemical kinetics, tailoring of fuel properties is required to address the limitations in-terms of lack of ignition timing control and a narrow operating load range. Utilizing fuel blends and additives such as nanoparticles are one of the promising approaches to achieve targeted fuel property. An improved understanding of fundamental processes including fuel evaporation is required owing to its role in fuel-air mixing and emission formation in LTC. In the present work, evaporation rate characteristics of blends of

Gupta, Saurabh Kumar, Krishnasamy, Anand

Effects of Oxidation Upon Long-term Storage of Karanja Biodiesel on the Combustion and Emission Characteristics of a Heavy-Duty Truck Diesel Engine

2021-01-120009/21/2021

The presence of unsaturated methyl esters in biodiesel makes it susceptible to oxidation and fuel quality degradation upon long-term storage. In the present work, the effects of oxidation of Karanja biodiesel upon long-term storage on the combustion and emission characteristics of a heavy-duty truck diesel engine are studied. The Karanja biodiesel is stored for one year in a 200 litres steel barrel at room conditions to mimic commercial storage conditions. The results obtained show that compared to diesel, the start of injection of fresh and aged biodiesels are advanced by ~2-degree crank angle, and the ignition delay time is reduced. Aged biodiesel showed a slightly smaller ignition delay compares to fresh biodiesel. The fuel injection and combustion characteristics of fresh and aged biodiesels were similar at all the load conditions. Both fresh and aged biodiesels produced higher oxides of nitrogen (NOx) and lower smoke emissions compared to diesel. The exhaust emission

C K, Suraj, Krishnasamy, Anand

Impact of CO2 dilution on ignition delay times of full blend gasolines in a rapid compression machine

2021-01-119909/21/2021

Autoignition delay times of two full blend gasoline fuels (high and low RON) were explored in a rapid compression machine. CO2 dilution by mass was introduced at 0%, 15% and 30% levels with the O2:N2 mole ratio fixed at 1:3.76 emulating exhaust gas recirculation (EGR) substitution in spark ignition (SI) engines. Experiments were conducted over the temperature range of 650K-900K and at 10bar and 20 bar compressed pressure conditions for equivalence ratios of (Φ =) 0.6-1.3. The full blend fuels were admitted directly into the combustion chamber for mixture preparation using the direct test chamber (DTC) approach. CO2 addition retarded the autoignition times for the fuels studied here. The retarding effect of the CO2 dilution was more pronounced in the NTC region when compared to the lower and higher temperature range. The effect of dilution was more pronounced for the higher RON fuel in comparison to the lower RON fuel. With CO2 dilution, ignition delay times of the low RON fuel matched

Chinnathambi, Prasanna, Wadkar, Chaitanya, Gudiyella, Soumya, Estefanous, Fadi, Toulson, Elisa

Validation of Kinetic Mechanisms against Various Ignition Delay Data and the Development of Ignition Delay Correlations for Ethanol, Natural Gas, and Primary Reference Fuel Blends under Homogeneous Charge Compression Ignition Conditions

03-15-03-001709/21/2021

Homogeneous Charge Compression Ignition (HCCI) is a promising advanced combustion concept with high efficiencies and low emissions. Chemical kinetic mechanisms and ignition delay correlations (IDCs) are often applied to simulate HCCI combustion. However, a large number of mechanisms and correlations are not developed specifically for HCCI conditions, i.e., lean mixtures and usually with significant residual gas fractions (RGF). To address this issue, a two-part study is conducted. First, experimental ignition delay time (IDT) data from literature under typical HCCI conditions is collected. Then, thirteen widely applied mechanisms for ethanol, natural gas, and primary reference fuel (PRF) blends of isooctane and n-heptane are validated by running constant-volume simulations. Their performance and accuracy are evaluated. Second, the mechanism with the highest accuracy for each fuel is used to generate IDCs for HCCI conditions. For each fuel, simulations were performed to cover a wide

Zhou, Yingcong, Lawler, Benjamin

The Effect of Spark-Plug Heat Dispersal Range and Exhaust Valve Opening Timing on Cold-Start Emissions and Cycle-to-Cycle Variability

2021-01-118009/21/2021

The partnership for advancing combustion engines (PACE) is a US Department of Energy consortium involving multiple national laboratories and includes a goal of addressing key efficiency and emission barriers in light-duty engines fueled with a market-representative E10 gasoline. A major pillar of the initiative is the generation of detailed experimental data and modeling capabilities to understand and predict cold-start behavior. Cold-start, as defined by the time between first engine crank and three-way catalyst light-off, is responsible for a large percentage of NOx, unburned hydrocarbon and particulate matter emissions in light-duty engines. Minimizing emissions during cold-start is a trade-off between achieving faster light-off of the three-way catalyst and engine out emissions during that period. In this study, gaseous and soot emissions were measured at a distance representative of the three-way catalyst position downstream of the engine at a 2 bar net indicated mean effective

Jatana, Gurneesh S., Dal Forno Chuahy, Flavio, Szybist, James

Misfire Behavior and Mitigations of Passive Pre-chambers at Low-Load Operation in an Optically Accessible Gasoline Engine

03-15-03-001609/14/2021

An experiment has been developed to investigate the passive pre-chamber jet ignition process in gasoline engine configurations and low-load operating conditions. The apparatus adopted a modified 4-cylinder 2.0L gasoline engine to enable single-cylinder operation. To reduce the complexity, the piston position was fixed at a predefined position relative to the top dead center (TDC) to simulate thermodynamic conditions at ignition and injection timings. High-speed Infrared (IR) imaging was applied to visualize the jet penetration and ignition process inside the main cylinder and to investigate the cyclic spatial variability. Two passive pre-chambers with different total nozzle areas and numbers of nozzles were used. In addition, the pre-chamber volume and pressure at ignition timing were varied to examine their effect on jet ignition performance. Misfire behavior was observed in the main chamber of all test cases, and the results suggested that the main cause is a high Residual Mass

Lee, Dong Eun, Swanson, Christopher, Yu, Xin, Qiao, Li

021 - Development of a 0D Model Starting from Different RANS CFD Tumble Flow Fields in Order to Predict the Turbulence Evolution at Ignition Timing

SAE-PP-0015001/25/2021

aster combustion and lower cycle-to-cycle variability are mandatory tasks for naturally aspirated engines to reduce emission levels and to increase engine efficiency. The promotion of a stable and coherent tumble structure is considered as one of the best way to promote the in-cylinder turbulence and therefore the combustion velocity. During the compression stroke the tumble vortex is deformed, accelerated and its breakdown in smaller eddies leads to the turbulence enhancement process. The prediction of the final level of turbulence for a particular engine operating point is crucial during the engine design process because it represents a practical comparative means for different engine solutions. The tumble ratio parameter value represents a first step toward the evaluation of the turbulence level at ignition time, but it has an intrinsic limit. The tumble ratio parameter represents the value of the angular velocity of a single macro vortex, while the flow-field is often characterized

Mutagaana, Festo

Advanced Combustion Modelling of High BMEP Engines under Water Injection Conditions with Chemical Correlations Generated with Detailed Kinetics and Machine Learning Algorithms

2020-01-200809/15/2020

Water injection is becoming a technology of increasing interest for SI engines development to comply with current and prospective regulations. To perform a rapid optimization of the main parameters involved by the water injection process, it is necessary to have reliable CFD methodologies capable of capturing the most important phenomena. In the present work, a methodology for the CFD simulation of combustion cycles of SI GDI turbocharged engines under water injection operation is proposed. The ECFM-3Z model adopted for combustion and knock simulations takes advantages by the adoption of correlations for the laminar flame speed, flame thickness and ignition delay times prediction obtained by a detailed chemistry calculation. The latter uses machine learning algorithms to reduce the time to generate the full database while still maintaining an even distribution along the variables of interest. The results demonstrate the applicability of the proposed methodology, capable of capturing

Pulga, Leonardo, Falfari, Stefania, Bianchi, Gian Marco, Ricci, Matteo, Forte, Claudio

Ignition Delay Model Parameterization Using Single-Cylinder Engines Data

2020-01-200509/15/2020

The confluence of increasing fuel economy requirements and increased use of ethanol as a gasoline blend component has led to various studies into the efficiency and performance benefits of higher octane numbers and high ethanol content fuels in modern engines. As part of a comprehensive study of the autoignition of different fuels in both the CFR octane rating engine and a modern, direct injection, turbocharged spark-ignited engine, a series of fuel blends were prepared with varying composition, octane numbers and ethanol blend levels. The paper reports on the third part of this study where cylinder pressures were recorded for fuels under knocking conditions in both a single-cylinder research engine (SCE), utilizing a GM LHU head and piston, as well as the CFR engines used for octane ratings. In the SCE, spark timing and air-fuel ratios were adjusted to achieve a consistent level of knock based on peak-to-peak values of the filtered cylinder pressures, over a range of engine speeds and

Kyler, CeCe, Swarts, Andre

Closed Loop Control of the Combustion Phase in SI Engines Using Alternative Fuels

2020-01-208809/15/2020

Combustion engines using alternative and/or renewable fuels are vital to reduce emission of greenhouse gases. The property of such fuels may vary significantly. The heat release rate of bio and natural gas varies of natural reasons, which is known to cause problems when used in internal combustion engines. Hydrogen is an attractive renewable fuel that has a high potential to reduce greenhouse gas emission. Bio and natural gas can be mixed with hydrogen and the content may vary depending on the availability, e.g., depending on the production from solar and wind power. Variations in the fuel property reduces the engine efficiency, unless the combustion phase is estimated and the ignition (combustion) timing is adapted to compensate for the varying fuel property. Hereby the drivability can be improved, and the fuel consumption decreased significantly, reducing the total cost of ownership and emission of greenhouse gases. However, there is not yet any widespread industrially available

A Novel Design of Engine Misfire Detection System Suitable for Small Capacity S.I. Engine for Two Wheeled Vehicle

2020-01-026704/14/2020

As per the OBD II regulations, it is essential to detect and monitor the misfire event in an I.C. engine. Misfiring of an I.C. engine affects the quality of combustion and degrades the performance of catalyst convertor which can lead to an increase of emissions. Misfire event can be categorized as partial or complete, based on amount of combustion occurred during that particular engine cycle. Most of the production engine for non-two wheeler vehicle identifies misfire by monitoring angular acceleration of the engine crank-shaft. However, single cylinder engine with lower capacity (less than 300 cubic centimeter) provides challenges to identify misfire due to low mechanical inertia of the I.C. engine using the same approach. The problem of misfire identification for this category of I.C. engine turn out to be more challenging due to presence of various load disturbances on the powertrain. Ion current sensing is one of the alternate method to detect misfire, which received good attention

Bagade, Monika Jayprakash, Das, Himadri Bhushan, Raveendranath Sr, Arjun, Jabez Dhinagar, S

Effect of Changing Compression Ratio on Ignition Delay Times of Iso-Octane in a Rapid Compression Machine

2020-01-033804/14/2020

Previous studies have shown that several facility dependent factors can influence ignition delay times measured in a rapid compression machine. Compression ratio variation represents one such aspect of many facility-to facility differences in RCMs, and can have a major impact on measured ignition delay times due to changes in surface-area-to-volume ratio, initial conditions and compression duration even when the same compressed conditions are maintained. In this study, iso-octane, which exhibits two stage ignition delay and has a pronounced negative temperature coefficient (NTC) region, is used to investigate the effects of changing compression ratio on ignition delay. Resulting trends are also compared to previous results obtained with ethanol, which has very different combustion properties. Experiments were carried out for rich mixtures (ϕ = 1.3) of iso-octane and air over a compressed temperature range of 675-900 K at 20 bar compressed pressure. Two compression ratios are considered

Wadkar, Chaitanya, Chinnathambi, Prasanna, Toulson, Elisa

Potential Analysis and Virtual Development of SI Engines Operated with Synthetic Fuel DMC+

04/14/2020

On the way to emission-free mobility, future fuels must be CO2 neutral. To achieve this, synthetic fuels are being developed. In order to better assess the effects of the new fuels on the engine process, simulation models are being developed that reproduce the chemical and physical properties of these fuels. In this paper, the fuel DMC+ is examined. DMC+ (a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) mainly, characterized by the lack of C-C Bonds and high oxygen content) offers advantages with regard to evaporation heat, demand of oxygen and knock resistance. Furthermore, its combustion is almost particle free. With the aid of modern 0D/1D simulation methods, an assessment of the potential of DMC+ can be made. It is shown that the simulative conversion of a state-of-the-art gasoline engine to DMC+ fuel offers advantages in terms of efficiency in many operating points even if the engine design is not altered. This is mainly due to the higher knock resistance and the

Wagner, Cornelius, Grill, Michael, Keskin, Mahir-Tim, Bargende, Michael, Cai, Liming, Pitsch, Heinz

Effect of Fuel and Lubricant on Engine Vibration

04/14/2020

Vibration problems in internal combustion engines produce premature wear on the internal components of the engine, which contributes both to reduce the lifespan of the engine itself as well as cause discomfort to the occupants of the vehicle. Thus, since it is impossible to totally eliminate vibrations from engines, it is important to understand the sources of vibration production and control them to acceptable levels. The general objective of this paper is to measure the vibration in the areas that undergo greater efforts due to the processes of combustion and mechanical forces. These areas are the fixed bearings located to the extremes of the crankshaft. The specified objective of this study is to correlate these levels of crankshaft engine vibration relative to the fuel used, ethanol and gasoline, and assess the influence of lubricant oils on the vibration levels as a function of the viscosity of the lubricant. The results demonstrated that the vibration intensity of the engine

Santana, Claudio Marcio, Mautone, Jose, Gutierrez, Juan, Almeida Junior, Hélder

Studying Ignition Delay Time of Lubricant Oil Mixed with Alcohols, Water and Toluene in IQT and CVCC

2020-01-142204/14/2020

The auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible sources of pre-ignition. Researchers are continually finding new ways to form advanced lubricant oil by changing its composition and varying different oil additives to prevent the occurrence of this event. This study investigates additives for lubricants to suppress its auto-ignition tendency. Three sets of mixtures were prepared. The first set of mixtures were prepared by adding different alcohols namely ethanol, and methanol to the commercial lubricant oil (SAE 15W-40) in ratio of 1 - 5 % by vol The second set of mixtures were prepared by mixing SAE 15W-40 with aforementioned alcohols (1 % vol.) and H2O (1 % vol.). Lastly, the third set of mixtures were prepared by adding toluene to SAE 15W-40 in (1 % - 5% by vol.). Two experimental setups were used in the current work. An Ignition Quality Tester (IQT) was used to investigate the mixtures’ ignition delay time (IDT) following standard ASTM

Maharjan, Sumit, Elbaz, Ayman, Mitsudharmadi, Hatsari, Roberts, William

Knock, Auto-Ignition and Pre-Ignition Tendency of Fuels for Advanced Combustion Engines (FACE) with Ethanol Blends and Similar RON

2020-01-061304/14/2020

Researchers have known about a higher pre-ignition frequency of alcohol fuels for several decades now. Several studies, assessing the effect of ethanol addition on stochastic pre-ignition, have shown contradicting observations. Researchers at FEV observed an increase in pre-ignition frequency with an increase in ethanol concentration, however the pre-ignition events at high ethanol content did not lead to super-knock. Most of the studies have used varying ethanol fraction in a common base-fuel, thereby varying the auto-ignition tendency of the blend. In the current study, the effect of ethanol addition on FACE (Fuels for Advanced Combustion Engines) gasolines is assessed. Five different FACE gasolines (FACE A, C, I, J and G) were used for the study. Ignition delay time of varying ethanol fractions in FACE gasolines was measured in an Ignition Quality Tester (IQT), following ASTM 6890. The measurements showed that 13% ethanol (v/v) is needed for FACE A and C, while 27% ethanol (v/v) is

Singh, Eshan, Dibble, Robert

Characteristics of Auto-Ignition for Lubricants and Lubricant/Gasoline Based on an Innovative Single Droplet Test System

2020-01-142804/14/2020

Due to the advantages of low weight, low emissions and good fuel economy, downsized turbocharged gasoline direct injection (GDI) engines are widely-applied nowadays. However, Low-Speed Pre-Ignition (LSPI) phenomenon observed in these engines restricts their improvement of performance. Some researchers have shown that auto-ignition of lubricant in the combustion chamber has a great effect on the LSPI frequency. To study the auto-ignition characteristics of lubricant, an innovative single droplet auto-ignition test system for lubricant and its mixture is designed and developed, with better accuracy and effectiveness. The experiments are carried out by hanging lubricant droplets on the thermocouple node under active thermo-atmosphere provided by a small “Dibble burner”. The auto-ignition process of lubricant droplets is recorded by a high-speed camera. Influences of different base oil types, viscosities, calcium contents, initial droplet diameters, co-flow speeds, new oil, used oil and

Yu, Yang, Pan, Kaifeng, Deng, Jun, Hu, Zongjie, Xie, Wei, Wu, Zhijun, Li, Liguang

Experimental Investigation of the Influence of Ignition System Parameters on Combustion in a Rapid Compression-Expansion Machine

2020-01-112204/14/2020

Lean burn combustion concepts with high mean effective pressures are being pursued for large gas engines in order to meet future stringent emission limits while maintaining high engine efficiencies. Since severe boundary conditions for the ignition process are encountered with these combustion concepts, the processes of spark ignition and flame initiation are important topics of applied research, which aims to avoid misfiring and to keep cycle-to-cycle combustion variability within reasonable limits. This paper focuses on the fundamental investigation of early flame kernel development using different ignition system settings. The investigations are carried out on a rapid compression-expansion machine in which the spark ignition process can be observed under engine-like pressure and excess air ratio conditions while low flow velocities are maintained. The schlieren setup for high-speed optical investigations of the area of the spark plug electrodes is described and a suitable post

Kiesling, Constantin, Pirker, Gerhard, Tilz, Anton, Oppl, Thomas, Nickl, Andreas, Wimmer, Andreas, Meyer, Georg

Investigation of the Impacts of Spark Plug Orientation on Combustion Stability under Lean SI Operation

2020-01-112104/14/2020

The increasingly stringent restrictions on vehicle emissions and fuel consumption are driving the development of gasoline engines towards lean combustion. Increasing ignition energy has been considered an effective way to achieve lean operation conditions. To further improve the lean limit of engine combustion, the influence of the spark plug orientation on the combustion stability under lean operation should be explored. In this investigation, the original machine spark plug orientation, 90 degrees clockwise rotation, and 180 degrees clockwise rotation are studied to analyze the impact of spark plug orientation. The combustion experiment was carried out under the condition of low excess air ratio of the original machine and high excess air ratio with a 450 mA high energy ignition. It is found that changing the orientation of the spark plug had little effect on combustion at low excess air ratio; however, under high excess air ratio (ultra-lean operation), spark plug orientation had a

Gu, Qifan, Xu, Min, Ye, Chang, Hung, David, Li, Xuesong

Optical Diagnostics of Isooctane and n-Heptane Isobaric Combustion

2020-01-112604/14/2020

Isobaric combustion has demonstrated a great potential to reach high thermodynamic efficiency in the advanced Double Compression Expansion Engine (DCEE) concept. It appears as one of few viable choices for applications with high-pressure combustion. At these conditions, releasing heat at a constant pressure minimizes the peak in-cylinder pressure and, hence, mitigates excessive mechanical stress on the engine. This study focuses on the effect of fuels on the multiple-injection isobaric combustion. A single-cylinder heavy-duty engine was utilized to test and compare the isobaric combustion with pure isooctane and n-heptane fuels. The engine was equipped with an optical piston to allow a bottom-view of the combustion chamber. The interactions of multiple injections and the combustion behavior were studied using high-speed acquisition of chemiluminescence. The examined isobaric cases have a peak pressure of 70 bar. For cases with high soot luminosity, a short band-pass filter was used to

Al Ramadan, Abdullah S., Nyrenstedt, Gustav, Ben Houidi, Moez, Johansson, Bengt

Ignition System Nomenclature and Terminology

J139_202002 (Current)02/10/2020

To provide standard terminology and definitions with regard to ignition systems for spark-ignited internal combustion engines.

Ignition Standards Committee

A Study of Ignition Method for Gas Heat Pump Engine Using Low Temperature Plasma

2019-32-062201/24/2020

Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended by low temperature plasma ignition while a voltage drop during discharge, leading to the transition to arc discharge, was found. In this study, the structure of plug and power supply’s performance with steep voltage rising with time, dV/dt, are examined to investigate the effects on combustion performance. As a result, comparing three power sources of conventional, IES and steep dV/dt, steep dV/dt showed small cycle-to-cycle variation and shorter combustion period, leading to higher peak value of the rate of heat release and better indicated thermal efficiency by relatively 6% and 4% compared to CIC and IES, respectively.

Moriyoshi, Yasuo, Matsumoto, Osamu, Kuboyama, Tatsuya, Tsukamoto, Takahiro, Kinuzawa, Yoshiyuki, Maeshima, Hideaki

Analysis of Cycle-to-Cycle Variation in a Port Injection Gasoline Engine by Simultaneous Measurement of Time Resolved PIV and PLIF

2019-32-055201/24/2020

Cycle-to-cycle variation (CCV) of combustion in low load operation is a factor that may cause various problems in engine operation. Variable valve timing and variable ignition timing are commonly used as a means to reduce this variation. However, due to mountability and cost constraints, these methods are not feasible for use in motorcycle engines. Therefore, development of an engine with minimal CCV without utilizing complicated mechanisms or electronic control is required. CCV of combustion may be caused by fluctuations in in-cylinder flow, air-fuel mixture, temperature, residual gas and ignition energy. In this study, the relationship between CCV of combustion, in-cylinder flow fluctuation and air-fuel mixture fluctuation was the primary focus. In order to evaluate in-cylinder flow fluctuation, Time Resolved Particle Image Velocimetry (TR-PIV) technique was utilized. In addition, Planar Laser Induced Fluorescence (PLIF) technique was used to measure spatial distribution of the

HARAMIISHI, Santa, WATANABE, Takahiro, IIDA, Minoru, HOKIMOTO, Satoshi, KUBOYAMA, Tatsuya, MORIYOSHI, Yasuo

Temperature Calculation Methodology of Pre Chamber With Homogeneous Charge

2019-36-020301/13/2020

The methodology for temperature calculations of homogeneous prechamber must be analyzed from a one-dimensional analytical model so that it is possible to determine the temperature profiles during the filling and emptying of the gases, so that it can avoid abnormalities such as increase of Forces, deformation / breaking, performance limitations, increased probability of detonation, increase of NOX and increase in the probability of pre-ignition. The equations of conservation of energy and of the state of gases are used to base the calculations, following the hypothesis that the flow is transient, comprehensible and one-dimensional; The fluid in the control volume is in the gaseous state and the fuel is already injected into the gas phase following the ideal gas equation. A homogeneous mixture is considered to generate a poor mixture in the pre-chamber.

MACHADO, L.F.G, FERREIRA, TIAGO S., RODRIGUES FILHO, F. A., MOREIRA, T. A. A.

Ignition of Individual Droplets in a Reactive Fuel/Air Mixture behind Reflected Shock Waves

2019-01-216212/19/2019

Multiphase-induced ignition is frequently discussed as a trigger for early ignition in internal combustion engines. In this context, we investigated the ignition process of single lubricant-oil droplets and their interaction with the bulk air/fuel mixture in a high-pressure shock tube, mimicking oil-fuel interaction in turbocharged internal combustion engines at the end of the compression stroke. A fast micro-dispensing injector released single fuel or lubricant oil droplets with a diameter of 200±50 µm into shock-heated fuel/air mixtures consisting of PRF95 and synthetic air. The injector was flush-mounted in the sidewall of the shock tube. The droplets were released into the gas after the passage of the reflected shock waves at post-shock conditions of 2 MPa and 750-950 K. With a high-frame-rate color camera, the entire evolution of droplet injection and ignition was traced in space and time through a large sapphire window in the endwall of the shock tube. A high-repetition-rate

Niegemann, P., Fikri, M., Kaiser, S. A., Schulz, C.

Influence of ethanol blending on knocking in a lean burn SI engine

2019-01-215212/19/2019

Lean burn is one method for improving thermal efficiency in spark ignition (SI) engines. Suppression of knocking provides higher thermal efficiency, and ethanol blending is considered an effective way to suppress knocking due to its high octane and high latent heat of evaporation. We investigate the effect of ethanol blending on knocking in an SI engine under lean operating conditions. The Livengood-Wu (LW) integral was performed based on ignition delay duration estimated from a zero-dimensional detailed chemical reaction calculation with pressure and temperature histories. Knocking was suppressed and thermal efficiency increased with ethanol-gasoline blending fuel, even at 0.5 equivalence ratio. Decrease in unburned gas temperature by latent heat of evaporation had a comparable influence on knocking suppression, which was supported by LW integral analysis.

Kaneko, Kazuki, Yasutake, Yuki, Yokomori, Takeshi, Iida, Norimasa

Using RON Synergistic Effects to Formulate Fuels for Better Fuel Economy and Lower CO2 Emissions

2019-01-2155-TEST-REC12/19/2019

The knock resistance of gasoline is a key factor to decrease the specific fuel consumption and CO2 emissions of modern turbocharged spark ignition engines. For this purpose, high RON and octane sensitivity (S) are needed. This study shows a relevant synergistic effect on RON and S when formulating a fuel with isooctane, cyclopentane and aromatics, the mixtures reaching RON levels well beyond the ones of individual components. The same is observed when measuring their knock resistance on a boosted single cylinder engine. The mixtures were also characterized on a rapid compression machine at 700 K and 850 K, a shock tube at 1000 K, an instrumented and an adapted CFR engine. The components responsible for the synergistic effects are thus identified. Furthermore, the correlations plotted between these experiments results disclose our current understanding on the origin of these synergistic effects. This study concludes that this synergistic effect encourages formulating highly paraffinic

Dauphin, Roland, Obiols, Jerome, Serrano, David, Fenard, Yann, Comandini, Andrea, Starck, Laurie, Vanhove, Guillaume, Chaumeix, Nabiha

Fuel Flexibility Study of a Compression Ignition Engine at High Loads

2019-01-219312/19/2019

Engine experiments were performed on a single-cylinder heavy-duty engine at relatively high loads to investigate the regions where the combustion characteristics are unchanged regardless of the fuel octane number. Primary Reference Fuels (PRFs) and three different commercial fuels with RON values ranging from 0 to 100 were tested in this study. A sweep of net indicated mean effective pressure (IMEPNet) of 5 to 20 bar, absolute intake pressure of 1.5 to 2.8 bar, exhaust gas recirculation (EGR) of 0 to 40%, and fuel injection pressure of 700 to 1400 bar were performed to investigate the combustion characteristics, ignition delay time, combustion duration, efficiency, and emissions. At the highest load point (IMEPNet = 20 bar), all the fuels burn as in conventional diesel combustion. Despite the wide range of octane numbers, all fuels had similar ignition delay time, combustion duration, indicated efficiency, and emissions at 10 to 20 bar IMEPNet. It follows that CI mode is the only

AlRamadan, Abdullah S., Houidi, Moez Ben, Nyrenstedt, Gustav, Johansson, Bengt

Using RON Synergistic Effects to Formulate Fuels for Better Fuel Economy and Lower CO2 Emissions

12/19/2019

The knock resistance of gasoline is a key factor to decrease the specific fuel consumption and CO2 emissions of modern turbocharged spark ignition engines. For this purpose, high RON and octane sensitivity (S) are needed. This study shows a relevant synergistic effect on RON and S when formulating a fuel with isooctane, cyclopentane and aromatics, the mixtures reaching RON levels well beyond the ones of individual components. The same is observed when measuring their knock resistance on a boosted single cylinder engine. The mixtures were also characterized on a rapid compression machine at 700 K and 850 K, a shock tube at 1000 K, an instrumented and an adapted CFR engine. The components responsible for the synergistic effects are thus identified. Furthermore, the correlations plotted between these experiments results disclose our current understanding on the origin of these synergistic effects. This study concludes that this synergistic effect encourages formulating highly paraffinic

Dauphin, Roland, Obiols, Jerome, Serrano, David, Fenard, Yann, Comandini, Andrea, Starck, Laurie, Vanhove, Guillaume, Chaumeix, Nabiha

Development of an iso-Octane Skeletal Combustion Mechanism based on Primary Sensitive Reactions

2019-01-235012/19/2019

In this study, an iso-octane skeletal combustion mechanism was constructed based on the sensitivity and reaction path analysis of the most recent published detailed iso-octane combustion mechanism. The major reactions relevant to the fuel consumption were determined based on sensitivity analysis at 650, 750 and 850 K under pressure of 20 bar for stoichiometric iso-octane/air mixture. Additional reactions were added to balance the reaction species. In particular, two lumped octyl radicals were used to describe the H atom abstraction products of iso-octane due to their distinctly opposite sensitivities on the fuel reactivity. In addition, major reaction equations for the description of fuel molecule consumption were kept as the same as those in the detailed mechanism for the purpose of traceability. The reaction rate constants of most reactions were taken from the detailed mechanism, and were kept unchanged except for a few reactions, of which the reaction rate constants were slightly

MENG, Xiangzan, MENG, Yi

Numerical Optimization of Compression Ratio for a PPC Engine running on Methanol

2019-01-216812/19/2019

Partially premixed combustion (PPC) has shown to produce high gross indicated efficiencies while yielding lower pollutant emissions, such as oxides of nitrogen and soot, than conventional diesel combustion. Gasoline fuels with a research octane number (RON) of 60-70 have been proposed as optimal for PPC as they balance the trade-off between ensuring good combustion stability at low engine loads and avoiding excessive peak pressure rise rates at high loads. However, measures have to be taken when optimizing the engine operating parameters to avoid soot emissions. In contrast, methanol has a much lower propensity for soot formation. However, due to a higher RON of methanol the required intake temperature is higher for the same engine compression ratio to ensure auto-ignition at an appropriate timing. Increasing the compression ratio allows a lower intake temperature and improves combustion stability as well as engine brake efficiency. Nevertheless, a higher compression ratio generally

Svensson, Erik, Verhelst, Sebastian

SI Combustion Characteristics of Cyclopentane - Detailed Kinetic Mechanism

2019-01-230512/19/2019

Cyclopentane (C5H10) has been reported to exhibit large octane sensitivity (RON − MON) = 17. During the course of research for sustainable liquid fuels, fundamental SI combustion characteristics of cyclopentane have been investigated using the kinetic mechanism which has been newly developed based on the quantum chemical calculations for essential chemical species and reactions. It was found that the intramolecular isomerization reaction via six-membered ring transition states are significantly hindered by the cyclic carbon skeleton. As a result, the predicted ignition delay times at low temperature are longer than those for the acyclic hydrocarbons. The effect on the laminar flame propagation speed was found to be small.

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