scholarly journals Numerical investigation on low calorific syngas combustion in the opposed-piston engine

2017 ◽  
Vol 169 (2) ◽  
pp. 53-63
Author(s):  
Rafał PYSZCZEK ◽  
Paweł MAZURO ◽  
Agnieszka JACH ◽  
Andrzej TEODORCZYK
Keyword(s):  
Compression Ratio ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Calorific Value ◽  
Mechanical Efficiency ◽  
Piston Engine ◽  
Engine Operation ◽  
Excessive Heat ◽  
Gaseous Fuels ◽  
Auto Ignition

The aim of this study was to investigate a possibility of using gaseous fuels of a low calorific value as a fuel for internal combustion engines. Such fuels can come from organic matter decomposition (biogas), oil production (flare gas) or gasification of materials containing carbon (syngas). The utilization of syngas in the barrel type Opposed-Piston (OP) engine arrangement is of particular interest for the authors. A robust design, high mechanical efficiency and relatively easy incorporation of Variable Compression Ratio (VCR) makes the OP engine an ideal candidate for running on a low calorific fuel of various compostion. Furthermore, the possibility of online compression ratio adjustment allows for engine the operation in Controlled Auto-Ignition (CAI) mode for high efficiency and low emission. In order to investigate engine operation on low calorific gaseous fuel authors performed 3D CFD numerical simulations of scavenging and combustion processes in the 2-stroke barrel type Opposed-Piston engine with use of the AVL Fire solver. Firstly, engine operation on natural gas with ignition from diesel pilot was analysed as a reference. Then, combustion of syngas in two different modes was investigated – with ignition from diesel pilot and with Controlled Auto-Ignition. Final engine operating points were specified and corresponding emissions were calculated and compared. Results suggest that engine operation on syngas might be limited due to misfire of diesel pilot or excessive heat releas which might lead to knock. A solution proposed by authors for syngas is CAI combustion which can be controlled with application of VCR and with adjustment of air excess ratio. Based on preformed simulations it was shown that low calorific syngas can be used as a fuel for power generation in the Opposed-Piston engine which is currently under development at Warsaw University of Technology.

Characteristics of Auto-Ignition in Internal Combustion Engines Operated With Gaseous Fuels of Variable Methane Number

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
German Amador ◽  
Jorge Duarte Forero ◽  
Adriana Rincon ◽  
Armando Fontalvo ◽  
Antonio Bula ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Internal Combustion Engines ◽  
Coal Gasification ◽  
Error Function ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Methane Number

This paper explores the feasibility of using Syngas with low methane number as fuel for commercial turbocharged internal combustion engines. The effect of methane number (MN), compression ratio (CR), and intake pressure on auto-ignition tendency in spark ignition internal combustion engines was determined. A nondimensional model of the engine was performed by using kinetics mechanisms of 98 chemical species in order to simulate the combustion of the gaseous fuels produced from different thermochemical processes. An error function, which combines the Livengood–Wu with ignition delay time correlation, to estimate the knock occurrence crank angle (KOCA) was proposed. The results showed that the KOCA decreases significantly as the MN increases. Results also showed that Syngas obtained from coal gasification is not a suitable fuel for engines because auto-ignition takes place near the beginning of the combustion phase, but it could be used in internal combustion engines with reactivity controlled compression ignition (RCCI) technology. For the case of high compression ratio and a high inlet pressure at the engine's manifold, fuels with high MN are suitable for the operating conditions proposed.

A Theoretical Study on Performance and Combustion Characteristics of HCCI Engine Operation With Diesel Surrogate Fuels: n-Heptane, Dimethyl Ether

2008 ◽  
Author(s):  
Seyed Navid Shahangian ◽  
Mojtaba Keshavarz ◽  
Ghasem Javadirad ◽  
Nader Bagheri ◽  
Seyed Ali Jazayeri
Keyword(s):  
Dimethyl Ether ◽  
Diesel Fuel ◽  
Alternative Fuels ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Main Stage ◽  
Engine Operation ◽  
Hcci Engine ◽  
Second Stage ◽  
Hcci Engines

HCCI engines have low emission and high efficiency values compared to the conventional internal combustion engines. These engines can operate on most alternative fuels such as dimethyl ether (DME), which has been tested as a possible diesel fuel for its simultaneously reduced NOx and PM emissions. HCCI combustion of both DME and n-heptane fuels display a distinct two-stage ignition reaction with the first stage taking place at fairly low temperatures and the second stage taking place at high temperatures. The second stage is responsible for the main stage of the heat release process. In this study, a single-zone, zero-dimensional, thermo-kinetic combustion model has been developed. MATLAB software is used to predict engine performance characteristics of HCCI engines using two types of diesel fuel: Dimethyl ether and N-heptane. The effects of intake temperature and pressure, fuel loading and addition of EGR gases on auto-ignition characteristics, optimum combustion phasing, and performance of the HCCI engines are considered in this study. Simultaneous effects of these variables for finding the most appropriate regime of HCCI engine operation, considering knock and misfire boundaries, are also investigated.

Transient Control of a Hydraulic Free Piston Engine

2013 ◽  
Author(s):  
Ke Li ◽  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
High Efficiency ◽  
Combustion Engine ◽  
Tracking Error ◽  
Control Signal ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Engine Operation ◽  
Free Piston Engine ◽  
Transient Period

The free piston engine (FPE) is a type of internal combustion engine (ICE) with no crankshaft, so that its piston motion is no longer constrained by mechanical linkages. The FPE has a high potential in terms of energy saving given its simple structure, high modularity and high efficiency. One of the technical barriers that prevents the wide spread of the FPE technology, is the lack of precise piston motion control. Previously, a robust repetitive controller is designed and implemented to form a virtual crankshaft that would provide a precise and stable engine operation. The experimental data of engine motoring tests with virtual crankshaft demonstrates the effectiveness of the controller. However, the presence of a transient period after a single combustion event prevents the engine from continuous firing. This paper presents a modified control scheme, which utilizes a reference and control signal shifting technique to modify the tracking error and the control signal to reduce the transient period.

scholarly journals Combustion and Emission Characteristics of a Diesel Engine Operating with Varying Equivalence Ratio and Compression Ratio - A CFD Simulation

2020 ◽  
Vol 01 (03) ◽  
pp. 101-110
Author(s):  
Kazi Mostafijur Rahman ◽  
Zobair Ahmed
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Cfd Simulation ◽  
Combustion Engine ◽  
Computational Cost ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Engine Operation

The performance of diesel engine highly depends on atomization, vaporization and mixing of fuel with air. These factors are strongly influenced by various parameters e.g. injection pressure, injection timing, compression ratio, equivalence ratio, cylinder geometry, in cylinder air motion etc. In this study, a diesel engine has been investigated by employing a commercial CFD software (ANSYS Forte, version 18.1) especially developed for internal combustion engines (ICE) modeling; focusing primarily on the effects of equivalence ratio and compression ratio on combustion and emission characteristics. RNG k-ε model was employed as the turbulence model for analyzing the physical phenomena involved in the change of kinetic energy. In order to reduce the computational cost and time, a sector mesh of 45o angle with periodic boundary conditions applied at the periodic faces of the sector, is considered instead of using the whole engine geometry. Simulations are performed for a range of equivalence ratio varying from 0.6 to 1.2 and for three compression ratios namely, 15:1, 18:1 and 21:1. Results show that, improvement in combustion characteristics with higher compression ratio could be achieved for both lean and rich mixtures. Peak in-cylinder pressure and peak heat release nearer to TDC are achieved for compression ratio of 18:1 that could results in more engine torque. For compression ratio beyond 16:1, effects of fuel concentration on ignition delay is more pronounced. At lower compression ratio, in-cylinder temperature is not sufficiently high for atomization, vaporization, mixing of fuel with air, and preflame reactions to occur immediately after the fuel injection. NOx emission in diesel engine increases due to higher pressure and temperature inside the cylinder associated with relatively higher compression ratio. Rich mixture leads to more CO and unburnt hydrocarbon emission compared to lean mixture as result of incomplete combustion. Engine operation with too high compression ratio is detrimental as emission is a major concern.

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.

Modeling the Performance of a Turbo-Charged S.I. Natural Gas Engine With Cooled EGR

2006 ◽  
Author(s):  
Hailin Li ◽  
Ghazi A. Karim
Keyword(s):  
Natural Gas ◽  
Predictive Model ◽  
Engine Performance ◽  
Kinetic Scheme ◽  
Engine Operation ◽  
Natural Gas Engine ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Wide Range

A variety of gaseous fuels and wide range of cooled EGR could be used in turbocharged S.I. gas engines. This makes experimental investigation of knocking behavior both unwieldy and uneconomical. Accordingly, it would be attractive to develop suitable effective predictive model that can be used to improve understanding the role of various design and operating parameters and achieve a more optimized turbo-charged engine operation. A two-zone predictive model developed mainly for naturally aspirated S.I. engine applications of natural gas and validated earlier, was extended to consider applications employing turbochargers, after-coolers and cooled EGR. A suitably detailed kinetic scheme involving 155 reaction steps and 39 species for the oxidation of natural gas is employed to examine the pre-ignition reactions of the unburned natural gas-air mixtures that can lead to knock before being fully consumed by the propagating flame. The model predicts the onset of knock and its intensity once end gas auto-ignition occurs and considers the effects of turbo-charging and cooled EGR on the total energy to be released through auto-ignition and its effect on the intensity of the resulting knock. The consequences of changes in the effectiveness of after- and EGR-coolers when fitted, lean operation and reductions in the compression ratio on engine performance parameters, especially the incidence of knock were examined. The benefits, limitations and possible penalties of the application of fuel lean operation combined with cooled EGR are also examined and discussed.

CFD simulation-based predesign of an advanced gas-diesel combustion concept

2021 ◽  
pp. 146808742110350
Author(s):  
Hubert Winter ◽  
Kevin Aßmus ◽  
Christoph Redtenbacher ◽  
Dimitar Dimitrov ◽  
Andreas Wimmer
Keyword(s):  
High Speed ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Diesel Combustion ◽  
Virtual Design ◽  
Engine Operation ◽  
Low Emission ◽  
Methane Slip

The greenhouse gas saving potential of using gaseous fuels with high methane content (e.g. natural gas) in internal combustion engines instead of conventional liquid fossil fuels (e.g. petrol, diesel) is considerable due to the comparatively low emission of carbon dioxide resulting from the low C/H ratio of methane. However, to fully exploit this potential, it is of utmost importance to keep methane slip at a very low level. In contrast to mixture aspirated gas engines and diesel-gas engines, the gas-diesel combustion concept avoids methane slip nearly completely since the gaseous fuel is directly injected into the combustion chamber at the end of the high-pressure phase of the engine cycle, resulting in mixing-controlled combustion with low emission of unburned hydrocarbons. An advanced high-speed large engine concept based on the gas-diesel combustion process was developed. An effective and reliable virtual design methodology was applied during the development of the concept. The methodology comprehensively combines 3D CFD and 1D simulation tools in the combustion concept predesign phase with experiments on a single-cylinder research engine in the concept validation phase. A major challenge in the virtual design of this dual fuel combustion process is the large number of degrees of freedom that result in particular from the use of a fully flexible combined gas/diesel injector. This paper describes in detail the role of 3D CFD simulation in this approach, which allows precise prediction of the optimal geometries and operating strategies for high-efficiency and low-emission engine operation.

scholarly journals The Effects of Ultra-Low Viscosity Engine Oil on Mechanical Efficiency and Fuel Economy

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2320
Author(s):  
Yanyan Zhang ◽  
Ziyuan Ma ◽  
Yan Feng ◽  
Ziyu Diao ◽  
Zhentao Liu
Keyword(s):  
Internal Combustion Engines ◽  
High Efficiency ◽  
Load Capacity ◽  
Mechanical Efficiency ◽  
Friction Loss ◽  
Engine Oil ◽  
Lubrication Regimes ◽  
Low Viscosity ◽  
Hydraulic Friction ◽  
New Generation

The development of a sustainable powertrain requires improved thermal efficiency. Reducing frictional power losses through the use of ultra-low viscosity oil is one of the most effective and economical ways. To assess the potential for efficiency enhancement in a new generation of future engines using low-viscosity oils, a technical analysis was conducted based on numerical simulation and theoretical analysis. This study proposes a numerical method coupling the whole multi-dynamics model and lubrication model under mixed lubrication regimes. Then, load distribution was calculated numerically and verified experimentally. Finally, this paper compares the bearing load and frictional energy loss of the main bearings when using The Society of Automotive Engineers (SAE) 15W40 and SAE 0W20 oil. The results indicate that the application of ultralow-viscosity lubricant can reduce the hydraulic friction loss up to 24%, but the asperity friction loss would increase due to the reduction in load capacity. As a result, the design of a new generation of high efficiency internal combustion engines requires careful calculation and design to balance the trade-off relations between hydraulic friction and asperity friction.

NOx Emissions Characterization During Transient Spark Assisted Compression Ignition (SACI) Engine Operation

2013 ◽  
Author(s):  
Weiyang Lin ◽  
Jeff Sterniak ◽  
Stanislav V. Bohac
Keyword(s):  
Flame Propagation ◽  
High Efficiency ◽  
Time Lag ◽  
Time Lags ◽  
Nox Emissions ◽  
Compression Ignition ◽  
Ic Engine ◽  
Engine Operation ◽  
Auto Ignition ◽  
Operating Points

In the quest for high efficiency IC engine operation, spark assisted compression ignition (SACI) can fill the gap between homogeneous charge compression ignition (HCCI) operation at low load and spark ignited (SI) operation at high load. SACI combustion utilizes a combination of flame propagation and auto-ignition to achieve ignition when unburned temperatures are too low for reliable auto-ignition and the mixture is too dilute for flame propagation with sufficient speed. Stoichiometric SACI combustion with cooled external exhaust gas recirculation (EGR) offers improved thermal efficiency compared to stoichiometric SI operation. It also reduces combustion temperatures and therefore NOx emissions, while still allowing for the use of a three-way catalyst (TWC). This study investigates NOx spikes that can occur during transitions between different SACI operating points as a result of system time lags or mixture deviation from stoichiometry. Load transitions at various stoichiometric SACI operating points are investigated and NOx emissions before and after the TWC are reported. Significant engine-out NOx spikes are observed. A 1200 ppm NOx spike occurs during a load increase from 3 to 6 bar BMEP at 1800 rpm in 2 cycles (0.13 seconds), which is representative of a faster load change in the FTP-75 drive cycle. Observed NOx spikes are attributed to a time lag in external EGR during the transitions. NOx emissions after the TWC are reduced to below 50 ppm, indicating that NOx emissions during these transients can be handled effectively by a TWC.

scholarly journals Performance and Brake Specific Fuel Cost of Constant Speed Diesel Engine for Acetylene As Alternative Fuel

2019 ◽  
Vol 9 (2) ◽  
pp. 1003-1008
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Internal Combustion Engines ◽  
Edible Oils ◽  
Alternative Fuel ◽  
Constant Speed ◽  
Emission Analysis ◽  
Gaseous Fuels ◽  
Mode Of Operation ◽  
The Cost

Historical growth for development of power to fulfil the demands, together provides a challenge for depletion of fossil fuels. The internal combustion engines have a major share used to develop power. To fulfil the increasing demands, many researchers worked on diesel engine with biodiesel blends derived from edible and non-edible oils as an alternative fuel. Some researcher’s experimented gaseous fuels along with diesel also in which diesel will be primary fuel and gaseous fuels like acetylene will be secondary fuel. Increased rates of pollutants again required more focus in modification of engine sub-assemblies. The present study carried out to find the cost effectiveness while the constant speed diesel engine supplied 2 liter per minute flow rate of acetylene at different compression ratios. It realized that the brake specific fuel consumption and required cost to operate the engine, in case of duel fuel mode operation will be less for the compression ratio of 17. It was also noted that for idling or low load the operation of engine will be costly with duel fuel mode of operation and for maximum load the cost of operation will be barely same as the operation on only diesel. The results from performance analysis states that in duel fuel mode of operation by decreasing compression ratio to 17, no change in power out with decreased sound pressure. Also from emission analysis decreased CO2 , HC emission found than only diesel operation.

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