Predicting Ignition and Combustion of a Pilot Ignited Natural Gas Jet Using Numerical Simulation Based on Detailed Chemistry

2017 ◽  
Author(s):  
Michael Jud ◽  
Georg Fink ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Direct Injection ◽  
Dual Fuel ◽  
Pressure Curve ◽  
Detailed Chemistry ◽  
Dual Fuel Combustion ◽  
Good Agreement

In this paper, a multidimensional computational fluid dynamics (CFD) model coupled with detailed chemistry calculations was used to analyze dual-fuel combustion based on high pressure direct injection of natural gas. The main focus was to analyze the capability of predicting pressure curve and heat release rate (HRR) for different injection strategies. Zero-dimensional homogeneous constant volume reactor calculations were used to select a reaction mechanism for the temperature range below 800 K. As the best-performing mechanism, the Chalmers mechanism was chosen. To validate the numerical model, the setup was first split into a single gas injection and a single Diesel injection. They were validated individually using shadowgraphs obtained from a Rapid Compression Expansion Machine (RCEM). Diesel ignition timing and position in the combustion chamber were close to experimental results. Gas direct injection showed good agreement with regard to penetration and mixing. In the dual-fuel setup, the injection timing of natural gas was varied to create a first case with mainly diffusive combustion and a second case with mainly premixed combustion of natural gas. For both setups good agreement with pressure curve and heat release rate were achieved. A qualitative comparison of shadowgraphs with the density field highlights the important points to predict dual-fuel combustion.

Ability of the Methane Number Index of a Fuel to Predict Rapid Combustion in Heavy Duty Dual Fuel Engines for North American Locomotives

2015 ◽  
Author(s):  
Daniel G. Van Alstine ◽  
David T. Montgomery ◽  
Timothy J. Callahan ◽  
Radu C. Florea
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Rapid Combustion ◽  
Dual Fuel Engines ◽  
Dual Fuel Combustion ◽  
Methane Number

Low natural gas prices have made the fuel an attractive alternative to diesel and other common fuels, particularly in applications that consume large quantities of fuel. The North American rail industry is examining the use of locomotives powered by dual fuel engines to realize savings in fuel costs. These dual fuel engines can substitute a large portion of the diesel fuel with natural gas that is premixed with the intake air. Engine knock in traditional premixed spark-ignited combustion is undesirable but well characterized by the Methane Number index, which quantifies the propensity of a gaseous fuel to autoignite after a period of time at high temperature. Originally developed for spark-ignited engines, the ability of the methane number index to predict a fuel’s “knock” behavior in dual fuel combustion is not as fully understood. The objective of this effort is to evaluate the ability of an existing methane number algorithm to predict rapid combustion in a dual fuel engine. Sets of specialized natural gas fuel blends that, according to the MWM methane number algorithm, should have similar knock characteristics are tested in a dual fuel engine and induced to experience rapid combustion. Test results and CFD analysis reveal that rapid or aggressive combustion rates happen late in the dual fuel combustion event with this engine hardware configuration. The transition from normal combustion to late rapid combustion is characterized by changes in the heat release rate profiles. In this study, the transition is also represented by a shift in the crank angle location of the combustion’s peak heat release rate. For fuels of similar methane number that should exhibit similar knock behavior, these transitions occur at significantly different relative air-fuel ratios, demonstrating that the existing MWM methane number algorithm, while excellent for spark-ignited engines, does not fully predict the propensity for rapid combustion to occur in a dual fuel engine within the scope of this study. This indicates that physical and chemical phenomena present in rapid or aggressive dual fuel combustion processes may differ from those in knocking spark-ignited combustion. In its current form a methane number algorithm can be used to conservatively rate dual fuel engines. It is possible that derivation of a new reactivity index that better predicts rapid combustion behavior of the gaseous fuel in dual fuel combustion would allow ratings to be less conservative.

scholarly journals An experimental study of the dual-fuel performance of a small compression ignition diesel engine operating with three gaseous fuels

2007 ◽  
Vol 221 (8) ◽  
pp. 943-956 ◽  
Author(s):  
J Stewart ◽  
A Clarke ◽  
R Chen
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
High Speed ◽  
Direct Injection ◽  
Specific Energy Consumption ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Gaseous Fuels ◽  
Ci Engine

A dual-fuel engine is a compression ignition (CI) engine where the primary gaseous fuel source is premixed with air as it enters the combustion chamber. This homogenous mixture is ignited by a small quantity of diesel, the ‘pilot’, that is injected towards the end of the compression stroke. In the present study, a direct-injection CI engine, was fuelled with three different gaseous fuels: methane, propane, and butane. The engine performance at various gaseous concentrations was recorded at 1500 r/min and quarter, half, and three-quarters relative to full a load of 18.7 kW. In order to investigate the combustion performance, a novel three-zone heat release rate analysis was applied to the data. The resulting heat release rate data are used to aid understanding of the performance characteristics of the engine in dual-fuel mode. Data are presented for the heat release rates, effects of engine load and speed, brake specific energy consumption of the engine, and combustion phasing of the three different primary gaseous fuels. Methane permitted the maximum energy substitution, relative to diesel, and yielded the most significant reductions in CO2. However, propane also had significant reductions in CO2 but had an increased diffusional combustion stage which may lend itself to the modern high-speed direct-injection engine.

scholarly journals Heat release rate and emissions regimes of stratified pilot-ignited direct-injection natural gas combustion

2021 ◽  
pp. 146808742110469
Author(s):  
Jeremy Rochussen ◽  
Gordon McTaggart-Cowan ◽  
Patrick Kirchen
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Internal Combustion Engines ◽  
Direct Injection ◽  
Injection Timing ◽  
Heavy Duty ◽  
Wide Range ◽  
The Impact

Natural gas (NG) is an attractive fuel for heavy-duty internal combustion engines because of its potential for reduced CO2, particulate, and NOX emissions and lower cost of ownership. Pilot-ignited direct-injected NG (PIDING) combustion uses a small pilot injection of diesel to ignite a main direct injection of NG. Recent studies have demonstrated that increased NG premixing is a viable strategy to increase PIDING indicated efficiency and further reduce particulate and CO emissions while maintaining low CH4 emissions. However, it is unclear how the combustion strategies relate to one another, or where they fit within the continuum of NG stratification. The objective of this work is to present a systematic evaluation of pilot combustion, NG combustion, and emissions behavior of stratified-premixed PIDING combustion modes that span from fully-premixed to non-premixed conditions. A sweep of the relative injection timing, [Formula: see text], of NG and pilot diesel was performed in a heavy-duty PIDING engine with [Formula: see text] = 140–220 bar, [Formula: see text] = 0.47–0.71, and a constant NG energy fraction of 94%. Apparent heat release rate and emissions analyses identified interactions between the pilot fuel and NG, and qualitatively characterized the impact of NG stratification on combustion and emissions. Changes in the [Formula: see text] resulted in six distinct PIDING combustion regimes, for all considered injection pressures and equivalence ratios: (i) RIT-insensitive premixed, (ii) stratified-premixed (early-cycle injection), (iii) NG jet impingement transition, (iv) stratified-premixed (late-cycle injection), (v) variable premixed fraction, and (vi) minimally-premixed. Parametric definitions for the bounds of each regime of combustion were valid for the wide range of [Formula: see text] and [Formula: see text] investigated, and are expected to be relevant for other PIDING engines, as previously identified regimes agree with those identified here. This conceptual framework encompasses and validates the findings of previous stratified PIDING investigations, including optimal ranges of operation that provide significantly increased efficiency and lower emissions of incomplete combustion products.

scholarly journals A Three-Zone Heat-Release Rate Model for Dual-Fuel Combustion

2010 ◽  
Vol 224 (11) ◽  
pp. 2423-2434 ◽  
Author(s):  
J Stewart ◽  
A Clarke
Keyword(s):  
Heat Release ◽  
Reaction Zone ◽  
Heat Release Rate ◽  
Release Rate ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Gaseous Fuel ◽  
Dual Fuel ◽  
Pilot Fuel ◽  
Dual Fuel Combustion

Dual-fuel engines are modified compression ignition engines, where the primary source of fuel is a gaseous fuel, and ignition is provided by a ‘pilot’ injection of a reduced quantity of diesel. The generally accepted understanding of the dual-fuel engine describes its combustion process as proceeding in three stages. Initially, around half of the pilot will burn and entrain some gaseous fuel into an overall fuel-rich process. Subsequently, the remaining pilot fuel burns and entrains an increasing amount of the primary fuel into its reaction zone. In the final stage, a flame propagation process engulfs the remaining gaseous fuel. In this article, a three-zone model for the analysis of heat-release rate during the dual-fuel combustion process will be derived. This model will be tested against data obtained for diesel combustion and then applied to experimental data from a dual-fuel test program. It will be shown that there is little evidence to support the generally accepted description of the dual-fuel combustion process in a direct injection engine. The conclusion of this work is that dual-fuel combustion may be better considered as a diesel combustion process, where the gaseous fuel modifies the reaction zone surrounding each igniting droplet of the pilot fuel.

scholarly journals The classification of gasoline/diesel dual-fuel combustion based on the heat release rate shapes and its application in a light-duty single-cylinder engine

2018 ◽  
Vol 20 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Jeongwoo Lee ◽  
Sanghyun Chu ◽  
Jaegu Kang ◽  
Kyoungdoug Min ◽  
Hyunsung Jung ◽  
...  
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Thermal Efficiency ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Dual Fuel Combustion ◽  
Compression Ignition Combustion

In this research, there are two major sections for analysis: the characteristics of gasoline and diesel dual-fuel combustion and their application to operating load extension with high thermal efficiency and low emissions. All the experiments were completed using a single-cylinder compression ignition engine with 395 cc displacement. In the first section, the dual-fuel combustion modes were classified into three cases by their heat release rate shapes. Staying at 1500 r/min with a total value of 580 J of low heat for each cycle condition, the diesel injection timing was varied from before top dead center with a 6–46 °crank angle with 70% of gasoline fraction based on the low heating value. Among the modes were two suitable dual-fuel combustion modes for a premixed compression ignition. The first suitable mode shows multiple peaks in the heat release rate (mode 2) and the second suitable mode shows a single peak with a “bell-shaped” heat release rate (mode 3). These two dual-fuel combustion types showed a high gross indicated thermal efficiency of up to 46%. Based on the results in the first section, the practical application of dual-fuel premixed compression ignition combustion was investigated considering a high thermal efficiency and a high-load condition. At a 1500 r/min/gross indicated mean effective pressure of 6.5 bar, 48% of the gross indicated thermal efficiency was obtained by using dual-fuel premixed compression ignition combustion mode 3. This mode was typical of a “reactivity controlled compression ignition,” while the nitrogen oxides and the particulate matter emissions satisfied the EURO-6 regulation (0.21 g/kW h and 2.8 mg/m3, respectively). In addition, a high thermal efficiency (45%) with low maximum pressure rise rate, NOx (nitrogen oxides), and particulate matter emissions was obtained at 2000 r/min/gross indicated mean effective pressure 14 bar condition by the adjustment of dual-fuel premixed compression ignition combustion mode 2. As a result, this research contributes to the understanding and practical application of dual-fuel combustion for a light-duty compression ignition engine.

Fundamental Study of Diesel-Piloted Natural Gas Direct Injection Under Different Operating Conditions

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Direct Injection ◽  
Combustion Process ◽  
Operating Conditions ◽  
Gas Jet ◽  
Ignition And Combustion

Natural gas as an alternative fuel in engine applications substantially reduces both pollutant and greenhouse gas emissions. High pressure dual fuel (HPDF) direct injection of natural gas and diesel pilot has the potential to minimize methane slip from gas engines and increase the fuel flexibility, while retaining the high efficiency of a diesel engine. Speed and load variations as well as various strategies for emission reduction entail a wide range of different operating conditions. The influence of these operating conditions on the ignition and combustion process is investigated on a rapid compression expansion machine (RCEM). By combining simultaneous shadowgraphy (SG) and OH* imaging with heat release rate analysis, an improved understanding of the ignition and combustion process is established. At high temperatures and pressures, the reduced pilot ignition delay and lift-off length minimize the effect of natural gas jet entrainment on pilot mixture formation. A simple geometrical constraint was found to reflect the susceptibility for misfiring. At the same time, natural gas ignition is delayed by the early pilot ignition close to the injector tip. The shape of heat release is only marginally affected by the operating conditions and mainly determined by the degree of premixing at the time of gas jet ignition. Luminescence from the sooting natural gas flame is generally only detected after the flame extends across the whole gas jet at peak heat release rate. Termination of gas injection at this time was confirmed to effectively suppress soot formation, while a strongly sooting pilot seems to intensify soot formation within the natural gas jet.

Fundamental Study of Diesel-Piloted Natural Gas Direct Injection Under Different Operating Conditions

2018 ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Direct Injection ◽  
Combustion Process ◽  
Operating Conditions ◽  
Gas Jet ◽  
Ignition And Combustion

Natural gas as an alternative fuel in engine applications substantially reduces both pollutant and greenhouse gas emissions. High pressure dual fuel direct injection of natural gas and Diesel pilot has the potential to minimize methane slip from gas engines and increase the fuel flexibility, while retaining the high efficiency of a Diesel engine. Speed and load variations as well as various strategies for emission reduction entail a wide range of different operating conditions. The influence of these operating conditions on the ignition and combustion process is investigated on a rapid compression expansion machine. By combining simultaneous Shadowgraphy and OH* imaging with heat release rate analysis, an improved understanding of the ignition and combustion process is established. At high temperatures and pressures the reduced pilot ignition delay and lift-off length minimize the effect of natural gas jet entrainment on pilot mixture formation. A simple geometrical constraint was found to reflect the susceptibility for misfiring. At the same time natural gas ignition is delayed by the early pilot ignition close to the injector tip. The shape of heat release is only marginally affected by the operating conditions and mainly determined by the degree of premixing at the time of gas jet ignition. Luminescence from the sooting natural gas flame is generally only detected after the flame extends across the whole gas jet at peak heat release rate. Termination of gas injection at this time was confirmed to effectively suppress soot formation, while a strongly sooting pilot seems to intensify soot formation within the natural gas jet.

scholarly journals Effect of Premixed n-Butanol Ratio on the Initial Stage of Combustion in a Light-Duty Butanol/Diesel Dual-Fuel Engine

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4295
Author(s):  
Wei Tian ◽  
Hongchuan Zhang ◽  
Lenian Wang ◽  
Zhiqiang Han ◽  
Wenbin Yu
Keyword(s):  
Heat Release ◽  
Flame Propagation ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fuel Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Light Duty ◽  
Dual Fuel Combustion ◽  
Initial Heat

The impact of premixed n-butanol mixture on the heat release rate was investigated based on a modified light-duty diesel engine. The results show that reactivity stratification is formed in the cylinder through n-butanol port fuel injection (PFI) and diesel direct injection (DI). The initial heat release rate of the diesel/butanol dual-fuel combustion is restrained due to the low ignitability of butanol and the high volatility. Because of the auto-ignition of diesel, premixed n-butanol undergoes a high-temperature reaction, which has an active influence on the heat releasing of diesel/butanol dual-fuel combustion. With the increase of the amount of premixed n-butanol injected, the heat release rate in the initial combustion period has a critical value. When the n-butanol injection quantity is less than 13 mg/cycle, the initial heat release rate of dual-fuel combustion is lower than the pure diesel combustion because the lean premixed n-butanol/air mixture limits the flame propagation. When the fuel injection rate of n-butanol is higher than 13 mg/cycle, the heat release rate is accelerated, leading to obvious flame propagation.

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