Numerical Study on the Effect of Fuel Rich n-Heptane on In-Cylinder Fuel Reforming Characteristics in an HCCI Engine

The effect of in-cylinder fuel reforming on an n-heptane homogenous charge compression ignition engine has been studied. A dedicated cylinder without a complex control system is proposed for fuel enrichment reforming, which can provide part of the power for the engine. The effects of different reforming species on engine performance and chemical reaction have been simulated by a numerical study. By comparing the combustion characteristics of n-heptane with different equivalence ratios in the reformer cylinder, the optimal n-heptane equivalence ratio has been determined. The enrichment of n-heptane produces sufficient hydrogen (H2) and carbon monoxide (CO), while the hydrocarbon content of the reforming species was low. It was found that the addition of reforming species retards the combustion phase of n-heptane, thereby providing a means of controlling engine performance. In addition, the laminar flame speed and the adiabatic flame temperature of n-heptane increased by adding H2 and CO. Fuel reforming reduced the emission of ethylene, propyne, allene, propylene, butadiene, and nitrogen oxide, but it increased the emissions of acetylene and CO. Moreover, chemical, dilution, and thermodynamic effects of the reforming gas have been studied. The results showed that the chemical effect of the reforming species was less significant than the dilution and thermodynamic effects. These simulation results showed that in-cylinder fuel reforming can effectively improve engine performance and thereby reduce emissions.

Download Full-text

A Numerical Study on the Reactivity of Biogas/Reformed-Gas/Air and Methane/Reformed-Gas/Air Mixtures at Gas Turbine Relevant Conditions

Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems ◽

10.1115/gt2016-56655 ◽

2016 ◽

Cited By ~ 3

Author(s):

Pablo Diaz Gomez Maqueo ◽

Philippe Versailles ◽

Gilles Bourque ◽

Jeffrey M. Bergthorson

Keyword(s):

Gas Turbine ◽

Laminar Flame ◽

Numerical Study ◽

Flame Temperature ◽

Flame Speed ◽

Flame Stability ◽

Laminar Flame Speed ◽

Fuel Reforming ◽

Numerical Work ◽

Chemical Effects

This study investigates the increase in methane and biogas flame reactivity enabled by the addition of syngas produced through fuel reforming. To isolate thermodynamic and chemical effects on the reactivity of the mixture, the burner simulations are performed with a constant adiabatic flame temperature of 1800 K. Compositions and temperatures are calculated with the chemical equilibrium solver of CANTERA® and the reactivity of the mixture is quantified using the adiabatic, freely-propagating premixed flame, and perfectly-stirred reactors of the CHEMKIN-Pro® software package. The results show that the produced syngas has a content of up to 30 % H2 with a temperature up to 950 K. When added to the fuel, it increases the laminar flame speed while maintaining a burning temperature of 1800 K. Even when cooled to 300 K, the laminar flame speed increases up to 30 % from the baseline of pure biogas. Hence, a system can be developed that controls and improves biogas flame stability under low reactivity conditions by varying the fraction of added syngas to the mixture. This motivates future experimental work on reforming technologies coupled with gas turbine exhausts to validate this numerical work.

Download Full-text

Numerical Investigation of the Characteristics of the In-Cylinder Air Flow in a Compression-Ignition Engine for the Application of Emulsified Biofuels

Processes ◽

10.3390/pr8111517 ◽

2020 ◽

Vol 8 (11) ◽

pp. 1517

Author(s):

Mohd Fadzli Hamid ◽

Mohamad Yusof Idroas ◽

Mazlan Mohamed ◽

Shukriwani Sa'ad ◽

Teoh Yew Heng ◽

...

Keyword(s):

Fuel Injection ◽

Numerical Study ◽

Guide Vane ◽

Engine Performance ◽

3D Analysis ◽

Compression Ignition Engine ◽

Ansys Fluent ◽

Start Of Injection ◽

Crank Angle ◽

Start Of Combustion

This paper presents a numerical analysis of the application of emulsified biofuel (EB) to diesel engines. The study performs a numerical study of three different guide vane designs (GVD) that are incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. The GVD variables were used in three GVD models with different vane heights, that is, 0.2, 0.4 and 0.6 times the radius of the intake runner (R) and these were named 0.20R, 0.40R and 0.60R. The SCC piston and GVD model were designed using SolidWorks 2017, while ANSYS Fluent version 15 was used to perform cold flow engine 3D analysis. The results of the numerical study showed that 0.60R is the optimum guide vane height, as the turbulence kinetic energy (TKE), swirl ratio (Rs), tumble ratio (RT) and cross tumble ratio (RCT) in the fuel injection region improved from the crank angle before the start of injection (SOI) and start of combustion (SOC). This is essential to break up the heavier-fuel molecules of EB so that they mix with the surrounding air, which eventually improves the engine performance.

Download Full-text

Combustion Characteristics of Producer Gas in the Stationary Gas Engine

ASME 2011 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2011-60060 ◽

2011 ◽

Cited By ~ 1

Author(s):

Arnold M. Kim ◽

James A. Smith ◽

Jayson R. Wagler ◽

Darryl D. Baldwin

Keyword(s):

Performance Test ◽

Laminar Flame ◽

Model Development ◽

Flame Temperature ◽

Engine Performance ◽

Combustion Characteristics ◽

Gas Combustion ◽

Wide Range ◽

Test Engine ◽

Explosive Reaction

Three syngases were selected from customer sites and the engine performance test was conducted on a single cylinder test engine (SCTE) to explore the engine operating limits and investigate the combustion characteristics for the simulation model development. Syngas has a wide range of lambda between the misfire and the detonation compared to conventional natural gas. Combustion of syngas 1 having no CH4 showed unique characteristics which are different from syngas 3. It appears that even a small amount of CH4 in the fuel would be important to lower the rate of the main branching reaction of hydrogen and mitigate the explosive reaction of the hydrogen. Lean operating limit of the tested syngas was observed when LFS (Laminar Flame Speed) and AFT (Adiabatic Flame Temperature) become around 5∼7 cm/s and 1660 ∼ 1720°C.

Download Full-text

A Numerical Study on the Effect of Water Addition on NO Formation in Counterflow CH4/Air Premixed Flames

ASME 2005 Internal Combustion Engine Division Fall Technical Conference (ICEF2005) ◽

10.1115/icef2005-1299 ◽

2005 ◽

Author(s):

Hongsheng Guo ◽

Stuart W. Neill ◽

Gregory J. Smallwood

Keyword(s):

Numerical Study ◽

Temperature Drop ◽

Flame Temperature ◽

Premixed Flames ◽

Chemical Effect ◽

Water Addition ◽

Detailed Chemistry ◽

Effect Of Water ◽

No Formation ◽

The Rich

The effect of water addition on NO formation in counterflow CH4/air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to the flame temperature drop. Among a lean, a stoichiometric and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame, since the dominant NO formation mechanism varies. The addition of water also reduces the formation of NO in a flame because of chemical effect that increases the concentration of OH, while reduces the concentrations of O and H. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.

Download Full-text

Numerical Study of Hydrogen Addition Fuel on Soot Formation in Axisymmetric Laminar Methane/Air Diffusion Flames

E3S Web of Conferences ◽

10.1051/e3sconf/202019404054 ◽

2020 ◽

Vol 194 ◽

pp. 04054

Author(s):

Bencheng Zhu ◽

Yuhan Zhu ◽

Jiajia Wu ◽

Kun Lu ◽

Yang Wang ◽

...

Keyword(s):

Diffusion Flames ◽

Soot Formation ◽

Numerical Study ◽

Flame Temperature ◽

Surface Growth ◽

Chemical Effect ◽

Oh Radicals ◽

Phase Reaction ◽

Hydrogen Addition ◽

Air Diffusion

This article employs the CoFlame Code to investigate the effects of hydrogen addition to fuel on soot formation characteristics in laminar coflow methane/air diffusion flames at atmospheric pressure. Numerical calculations were carried out using a detailed C1-C2 gas phase reaction mechanism and a soot model consisting of two pyrene molecules colliding into a dimer as soot nucleation, hydrogen abstraction acetylene addition (HACA) and pyrene condensation as surface growth, and soot oxidation by O2, O and OH radicals. Calculations were conducted for five levels of hydrogen addition on volume basis. To quantify the chemical effect of hydrogen, additional calculations are performed for addition of inert pseudo-hydrogen (FH2). The addition of H2 or FH2 does not have a strong influence on flame temperature. The results confirm that hydrogen addition can inhibit soot formation in the methane/air diffusion flame by reducing both the nucleation and surface growth steps of soot formation process. The effect of FH2 addition on soot formation suppression is more remarkable than H2, indicating that the chemical effect of hydrogen added to methane prompts soot formation. The dilution effect of hydrogen addition on soot formation suppression is stronger than its chemical effect on soot formation enhancement the present findings are consistent with those of previous numerical studies.

Download Full-text

Engine Capability Prediction for SI Engine Fueled With Syngas

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2015-1043 ◽

2015 ◽

Author(s):

Hui Xu ◽

Leon A. LaPointe

Keyword(s):

Natural Gas ◽

Solid Waste ◽

Laminar Flame ◽

Combustion Engine ◽

Flame Temperature ◽

Engine Performance ◽

Nox Emissions ◽

Lean Burn ◽

Gaseous Fuels ◽

Combustion Duration

There are increasing interests in converting solid waste or lignocellulosic biomass into gaseous fuels and using reciprocating internal combustion engine to generate electricity. A widely used technique is gasification. Gasification is a process where the solid fuel and air are introduced to a partial oxidation environment, and generate combustible gaseous called synthesis gas or syngas. Converting solid waste into gaseous fuel can reduce landfill and create income for process owners. However it can be very challenging to use syngas on a gaseous fueled spark ignited engine, such as a natural gas (NG) engine. NG engines are typically developed with pipeline quality natural gas (PQNG). NG engines can operate at lean burn spark ignited (LBSI), or stoichiometric with EGR spark ignited (SESI) conditions. This work discusses the LBSI engine condition. NG engines can perform very differently when fueled with nonstandard gaseous fuels such as syngas without appropriate tuning. It is necessary to evaluate engine performance in terms of combustion duration, relative knock propensity and NOx emissions for such applications. Due to constraints in time and resources it is often not feasible to test such fuel blends in the laboratory. An analytical method is needed to predict engine performance in a timely manner. This study investigated the possibility of using syngas on a spark ignited engine developed with PQNG. Engine performance was predicted using in house developed models and PQNG as the reference fuel. Laminar flame speed (LFS), adiabatic flame temperature (AFT) and Autoignition interval (AI) are used to predict combustion duration, engine out NOx and engine knock propensity relative to NG at the target Lambda values. Single cylinder research engine data obtained under lean burn conditions fueled with PQNG was selected as the baseline. LFS, AFT and AI of syngas were computed at reference conditions. Lambda of operation was predicted for syngas to provide the same burn rate as NG at the reference Lambda value for NG. Analysis shows that, using syngas at the selected Lambda, the engine can have less engine out NOx emissions and less knock propensity relative to NG at the same speed and load. Modifications to fuel system components may be required to avoid engine derate.

Download Full-text

Numerical study of the laminar flame propagation in ethane-air mixtures

Open Chemistry ◽

10.2478/s11532-013-0387-0 ◽

2014 ◽

Vol 12 (3) ◽

pp. 391-402 ◽

Cited By ~ 5

Author(s):

Venera Giurcan ◽

Domnina Razus ◽

Maria Mitu ◽

Dumitru Oancea

Keyword(s):

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Laminar Flame ◽

Numerical Study ◽

Flame Temperature ◽

Chemical Species ◽

Main Reaction ◽

Flame Thickness ◽

Wide Range

AbstractThe structure of premixed free one-dimensional laminar ethane-air flames was investigated by means of numerical simulations performed with a detailed mechanism (GRI-Mech version 3.0) by means of COSILAB package. The work provides data on ethane-air mixtures with a wide range of concentrations ([C2H6] = 3.0–9.5 vol.%) at initial temperatures between 300 and 550 K and initial pressures between 1 and 10 bar. The simulations deliver the laminar burning velocities and the profiles of temperature, chemical species concentrations and heat release rate across the flame front. The predicted burning velocities match well the burning velocities measured in various conditions, reported in literature. The influence of initial concentration, pressure and temperature of ethane-air mixtures on maximum flame temperature, heat release rate, flame thickness and peak concentrations of main reaction intermediates is examined and discussed.

Download Full-text

A Numerical Study on the Effect of Water Addition on NO Formation in Counterflow CH4/Air Premixed Flames

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2432890 ◽

2008 ◽

Vol 130 (5) ◽

Cited By ~ 2

Author(s):

Hongsheng Guo ◽

W. Stuart Neill ◽

Gregory J. Smallwood

Keyword(s):

Numerical Study ◽

Temperature Drop ◽

Flame Temperature ◽

Premixed Flames ◽

Chemical Effect ◽

Water Addition ◽

Detailed Chemistry ◽

Effect Of Water ◽

No Formation ◽

The Rich

The effect of water addition on NO formation in counterflow CH4/air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to flame temperature drop. Among a lean, a stoichiometric, and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame. The addition of water also reduces the formation of NO in a flame because of the chemical effect. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.

Download Full-text

Experimental and Numerical Study on Oxygen Enhanced Methane Combustion in a Rapidly Mixed Tubular Flame Burner

Volume 6A: Energy ◽

10.1115/imece2015-50574 ◽

2015 ◽

Author(s):

Baolu Shi ◽

Jie Hu ◽

Satoru Ishizuka ◽

Junwei Li ◽

Ningfei Wang

Keyword(s):

Carbon Dioxide ◽

Mole Fraction ◽

High Speed ◽

Equivalence Ratio ◽

Laminar Flame ◽

Numerical Study ◽

Flame Temperature ◽

Injection Velocity ◽

Flame Burner ◽

Oxygen Mole Fraction

To promote energy and environment security through combustion efficiency improvement as well as CO2 capture and sequestration (CCS), in this study oxygen enhanced combustion of methane has been investigated by using an inherently safe technique of rapidly mixed tubular flame combustion. As a new type of flame, the tubular flame has excellent flame characteristics such as negligible heat loss, aerodynamic stability and thermodynamic stability. Various applications have been proposed and demonstrated for determining the flammability limits, stabilizing a flame in a high speed flow, and obtaining a uniform and large-area laminar flame to heat iron slab or to reduce steel sheet surface. Especially, by individually injecting the fuel and the oxidizer into a cylindrical burner through four tangential slits hence, hence without flame flashback, the rapidly mixed tubular flame burner has been applied to analyze the characteristics of oxygen enhanced methane flame. To make a fundamental investigation, methane oxygen combustion has been attempted under various oxygen mole fractions with nitrogen and carbon dioxide as the diluents respectively. At first, nitrogen was added to the oxygen stream, and the oxygen mole fraction in the oxidizer was increased from 0.21 to 1.0. A stable, laminar tubular flame can be obtained from lean to rich when the oxygen mole fraction is no more than 0.4. And the maximum adiabatic flame temperature reaches around 2700 K. To enhance the mixing of fuel and oxidizer, nitrogen was also added to the fuel inlet to increase the injection velocity of fuel stream. The results show that by assigning the nitrogen to both the fuel and oxygen inlets to approach the same injection velocity, the flames become more uniform and stable. However, the range of stable tubular flame in equivalence ratio remains almost the same. Secondly, instead of nitrogen, carbon dioxide was used to dilute the methane/oxygen flames. Thus, the NOX emissions introduced by nitrogen will be greatly reduced, in addition, the main exhaust will be carbon dioxide and steam, which is beneficial for CCS. When carbon dioxide was only added into the oxygen stream, a stable tubular flame was obtained from 0.9 to 1.2 in equivalence ratio at the oxygen mole fraction of 0.21. With an increase of oxygen mole fraction, the stable tubular flame range enlarges in equivalence ratio, and up to the oxygen mole fraction of 0.50, stable tubular combustion could be achieved from lean to rich. By adding carbon dioxide to both the fuel and oxygen inlets to approach the same injection velocity, the upper limit of stable tubular flame increases much. Up to the oxygen mole fraction of 0.86, the stable combustion can be achieved at the stoichiometry, which gives a flame temperature around 3000 K. To fully understand the flame characteristics above, the chemical effects of carbon dioxide are numerical analyzed in comparing with the nitrogen diluted flames using the CHEMKIN PREMIX code with the GRI kinetic mechanism.

Download Full-text