Numerical Analysis of Biogas Composition Effects on Combustion Parameters and Emissions in Biogas Fueled HCCI Engines for Power Generation

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Iván D. Bedoya ◽  
Samveg Saxena ◽  
Francisco J. Cadavid ◽  
Robert W. Dibble
Keyword(s):  
Numerical Analysis ◽  
Power Output ◽  
Numerical Results ◽  
Combustion Stability ◽  
Absolute Pressure ◽  
Nox Emissions ◽  
Model Simulations ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Hcci Engines

This study investigates the effects of biogas composition on combustion stability for a purely biogas fueled homogeneous charge compression ignition (HCCI) engine. Biogas is one of the most promising renewable fuels for combined heat and power systems driven by internal combustion engines. However, the high content of CO2 in biogas composition leads to low thermal efficiencies in spark ignited and dual fuel compression ignited engines. The study is divided into two parts: First experimental results on a biogas-fueled HCCI engine are used to illustrate the effects of intake conditions on combustion stability, and second a simulation methodology is used to investigate how biogas composition impacts combustion stability at constant intake conditions. Experimental analysis of a four cylinder, 1.9 L Volkswagen TDI diesel engine shows that biogas-HCCI combustion exhibits high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%), and ultralow NOx emissions below the US2010 limit (0.27 g/kWh). An inlet absolute pressure of 2 bar and inlet temperature of 473 K (200 °C) were required for allowing HCCI combustion with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis. However, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations at low equivalence ratios and large changes in ringing intensity at high equivalence ratios. Numerical analysis of biogas-HCCI combustion is carried out with a sequential methodology that includes one-zone model simulations, computational fluid dynamics (CFD) analysis, and 12-zones model simulations. Numerical results for varied biogas composition show that at high load limit, higher contents of CH4 in biogas composition allow advanced combustion and increased burning rates of the biogas air mixture. Higher contents of CO2 in biogas composition allow lowered ringing intensities with moderate decrease in the indicated efficiency and power output. NOx emissions are not highly affected by biogas composition, while CO and unburned hydrocarbons (HC) emissions tend to increase with higher contents of CO2. According with the numerical results, biogas composition is an effective strategy to control the onset of combustion and combustion phasing of HCCI engines running biogas, allowing more stabilized combustion at low equivalence ratios and safe operation at high equivalence ratios. The main advantages of using biogas-fueled HCCI engines in CHP systems are the low sensitivity of power output and indicated efficiency to biogas composition, as well as the ultralow NOx emissions achieved for all tested compositions.

Numerical Analysis of Biogas Composition Effects on Combustion Parameters and Emissions in Biogas Fueled HCCI Engines for Power Generation

2011 ◽  
Author(s):  
Iva´n D. Bedoya ◽  
Samveg Saxena ◽  
Francisco J. Cadavid ◽  
Robert W. Dibble
Keyword(s):  
Numerical Model ◽  
Power Output ◽  
Internal Combustion Engines ◽  
Numerical Results ◽  
Experimental Results ◽  
Combustion Stability ◽  
Absolute Pressure ◽  
Nox Emissions ◽  
Hcci Engine ◽  
Hcci Engines

This study investigates the effects of biogas composition on combustion stability for a purely biogas fueled HCCI engine. Biogas is one of the most promising renewable fuels for Combined Heat and Power systems driven by internal combustion engines. However, the high content of CO2 in biogas composition leads to low thermal efficiencies in spark ignited and dual fuel compression ignited engines. The study is divided into two parts: first experimental results on a biogas-fueled HCCI engine are used to validate a numerical model, and second the model is used to investigate how biogas composition impacts combustion stability. In the first part of the study, experimental analysis of a 4 cylinder, 1.9 L Volkswagen TDI Diesel engine running with biogas in HCCI mode has shown high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and ultra-low NOx emissions below the US2010 limit (0.27 g/kWh). An inlet absolute pressure of 2 bar and inlet temperature of 473 K (200°C) were required for allowing HCCI combustion with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis. However, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations at low equivalence ratios and large changes in ringing intensity at high equivalence ratios. A numerical model is validated against these experimental results. In the second part of the study, the numerical results for varied biogas composition show that at high load limit, higher contents of CH4 in biogas composition allow advanced combustion and increased burning rates of the biogas air mixture. Higher contents of CO2 in biogas composition allow lowered ringing intensities with moderate decrease in the indicated efficiency and power output. NOx emissions are not highly affected by biogas composition, while CO and HC emissions tend to increase with higher contents of CO2. According with the numerical results, biogas composition is an effective strategy to control the onset of combustion and combustion phasing of HCCI engines running biogas, allowing more stabilized combustion at low equivalence ratios and safe operation at high equivalence ratios. The main advantages of using biogas fueled HCCI engines in CHP systems are the low sensitivity of power output and indicated efficiency to biogas composition, as well as the ultra low NOx emissions achieved for all tested compositions.

Exploring Strategies for Reducing High Intake Temperature Requirements and Allowing Optimal Operational Conditions in a Biogas Fueled HCCI Engine for Power Generation

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Iván D. Bedoya ◽  
Samveg Saxena ◽  
Francisco J. Cadavid ◽  
Robert W. Dibble
Keyword(s):  
Power Generation ◽  
Power Output ◽  
Numerical Results ◽  
Inlet Temperature ◽  
Zone Model ◽  
Nox Emissions ◽  
Efficient Operation ◽  
Operational Conditions ◽  
Hcci Engines ◽  
Temperature Requirements

This paper evaluates strategies for reducing the intake temperature requirement for igniting biogas in homogeneous charge compression ignition (HCCI) engines. The HCCI combustion is a promising technology for stationary power generation using renewable fuels in combustion engines. Combustion of biogas in HCCI engines allows high thermal efficiency similar to diesel engines, with low net CO2 and low NOx emissions. However, in order to ensure the occurrence of autoignition in purely biogas fueled HCCI engines, a high inlet temperature is needed. This paper presents experimental and numerical results. First, the experimental analysis on a 4 cylinder, 1.9 L Volkswagen TDI diesel engine running with biogas in the HCCI mode shows high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and NOx emissions below the 2010 US limit (0.27 g/kWh). Stable HCCI operation is experimentally demonstrated with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis, inlet pressures of 2–2.2 bar (absolute), and inlet temperatures of 200–210 °C for equivalence ratios between 0.19–0.29. At lower equivalence ratios, slight changes in the inlet pressure and temperature caused large changes in cycle-to-cycle variations, while at higher equivalence ratios these same small pressure and temperature variations caused large changes to the ringing intensity. Second, numerical simulations have been carried out to evaluate the effectiveness of high boost pressures and high compression ratios for reducing the inlet temperature requirements while attaining safe operation and high power output. The one zone model in Chemkin was used to evaluate the ignition timing and peak cylinder pressures with variations in temperatures at intake valve close (IVC) from 373 to 473 K. In-cylinder temperature profiles between IVC and ignition were computed using Fluent 6.3 and fed into the multizone model in Chemkin to study combustion parameters. According to the numerical results, the use of both higher boost pressures and higher compression ratios permit lower inlet temperatures within the safe limits experimentally observed and allow higher power output. However, the range of inlet temperatures allowing safe and efficient operation using these strategies is very narrow, and precise inlet temperature control is needed to ensure the best results.

Exploring Strategies for Reducing High Intake Temperature Requirements and Allowing Optimal Operational Conditions in a Biogas Fueled HCCI Engine for Power Generation

2011 ◽  
Author(s):  
Iva´n D. Bedoya ◽  
Samveg Saxena ◽  
Francisco J. Cadavid ◽  
Robert W. Dibble
Keyword(s):  
Power Generation ◽  
Power Output ◽  
Numerical Results ◽  
Inlet Temperature ◽  
Zone Model ◽  
Nox Emissions ◽  
Efficient Operation ◽  
Operational Conditions ◽  
Hcci Engines ◽  
Temperature Requirements

This paper evaluates strategies for reducing the intake temperature requirement for igniting biogas in HCCI engines. HCCI combustion is a promising technology for stationary power generation using renewable fuels in combustion engines. Combustion of biogas in HCCI engines allows high thermal efficiency similar to Diesel engines, with low net CO2 and low NOx emissions. However, in order to ensure the occurrence of autoignition in purely biogas fueled HCCI engines, a high inlet temperature is needed. This paper presents experimental and numerical results. First, experimental analysis on a 4 cylinder, 1.9 L Volkswagen TDI Diesel engine running with biogas in HCCI mode shows high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and NOx emissions below the 2010 US limit (0.27g/kWh). Stable HCCI operation is experimentally demonstrated with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis, inlet pressures of 2–2.2 bar (absolute) and inlet temperatures of 200–210°C for equivalence ratios between 0.19–0.29. At lower equivalence ratios, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations while at higher equivalence ratios these same small pressure and temperature variations caused large changes to ringing intensity. Second, numerical simulations have been carried out to evaluate the effectiveness of high boost pressures and high compression ratios for reducing the inlet temperature requirements while attaining safe operation and high power output. The one zone model in Chemkin was used to evaluate the ignition timing and peak cylinder pressures with variations in temperatures at IVC from 373 to 473 K. In-cylinder temperature profiles between IVC and ignition were computed using Fluent 6.3 and fed into the multi-zone model in Chemkin to study combustion parameters. According to the numerical results, the use of both higher boost pressures and higher compression ratios permit lower inlet temperatures within the safe limits experimentally observed and allow higher power output. However, the range of inlet temperatures allowing safe and efficient operation using these strategies is very narrow, and precise inlet temperature control is needed to ensure the best results.

A Control-Oriented Two Zone Thermo-Kinetic Model of a Single Cylinder HCCI Engine

2008 ◽  
Author(s):  
Varun Tandra ◽  
Nilabh Srivastava
Keyword(s):  
Kinetic Model ◽  
Compression Ignition Engine ◽  
Control Laws ◽  
Combustion Dynamics ◽  
Single Cylinder ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Homogeneous Composition ◽  
Start Of Combustion

Over the past two decades, homogeneous charge compression ignition engine technology (HCCI) has aroused a great deal of interest in the automotive sector owing to its ability to generate ultra-low exhaust emissions and to be fuel-flexible. The current work proposes a control-oriented two-zone thermo-kinetic model of such a single cylinder HCCI engine. Earlier control laws were derived by using single zone mathematical models of HCCI combustion; however, these models fail to accurately capture the combustion dynamics of an HCCI engine owing to the assumption of homogeneous composition and temperature in the cylinder. Certain multi-zone models of HCCI engines emphasizing the shortcomings of these single zone models have also been reported in literature. However, such models are far too complex and unwieldy for the development of fast and efficient controllers for HCCI engines. The present work outlines the modeling approach of a single-cylinder two-zone HCCI engine by incorporating the first law of thermodynamics and the temperature and concentration inhomogeneities. The results showed good conformity to those obtained from literature-based multi-zone models. A comparative analysis between the single zone and two-zone models, in the context of predicting cylinder pressures, exhaust gas temperatures, emission concentrations, and start of combustion (SOC), is also discussed.

A Two Zone Model of a Single Cylinder HCCI Engine for Control Applications

2008 ◽  
Author(s):  
Varun Tandra ◽  
Nilabh Srivastava
Keyword(s):  
Zone Model ◽  
Ignition Timing ◽  
Control Laws ◽  
Single Cylinder ◽  
First Law Of Thermodynamics ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Computationally Intensive ◽  
Peak Pressures

This paper presents a first step towards developing a physics-based two-zone model of a single cylinder HCCI engine. Previously control laws were derived by using single zone mathematical models of HCCI combustion; although certain multi-zone models were reported, they were found too complex and unwieldy for the development of fast and efficient controllers for HCCI engines. The present work outlines the modeling approach of a single-cylinder two-zone HCCI engine by incorporating the first law of thermodynamics and temperature and concentration inhomogeneities within the cylinder in order to better predict peak pressures and combustion timings. The results showed good conformity when compared with the computationally intensive multi-zone models. A comparative analysis between the single zone and two-zone models, in the context of predicting cylinder pressures, temperatures, ignition timing is also discussed. Moreover, the effect of external parameters such as speed, and EGR were also evaluated.

A Computational Study of HCCI Engine With External Mixture Formation Technique

2014 ◽  
Author(s):  
T. Karthikeya Sharma ◽  
G. Amba Prasad Rao ◽  
Madhu Murthy Kotha
Keyword(s):  
Computational Study ◽  
Nox Emissions ◽  
Mixture Formation ◽  
Gasoline Engines ◽  
Hcci Engine ◽  
Velocity Magnitude ◽  
Hcci Combustion ◽  
Numerical Studies ◽  
Diesel Injection ◽  
Formation Technique

HCCI combustion is gaining increased attention amongst the research community to make it viable in both diesel and gasoline engines. Of late, technique of External mixture formation is being adopted to avoid the problems associated with the early injection and late injections of the direct injected diesel HCCI engine. This paper reports the numerical studies on the effect of External mixture formation using three-zone extended coherent flame (ECFM-3Z) CFD model of the STAR - CD package. Firstly, the results obtained through package were validated with the results available in the literature. Trade-off between HC, CO and NOx was clearly observed through simulation. The simulation results revealed decrease in in-cylinder pressures and NOx emissions with increase in EGR concentration. There is an under prediction of NOx emissions when compared with the experimental results. However, a significant reduction in NOx emissions was observed with external mixture formation, usage compared to direct diesel injection. In case of HC and CO emissions increasing trend was observed with increase in EGR concentration. Increase in HC and CO emissions was observed with external mixture formation when compared with a direct diesel injection. Also, reduction in turbulent kinetic energy and velocity magnitude levels were observed with increase in EGR concentration. Improved piston work is resulted at lower EGR concentrations. Studies revealed that for a given combustion bowl geometry, It is concluded that external mixture formation technique could be adopted to achieve HCCI combustion.

Effects of Charge Preheating Methods on the Combustion Phasing Limitations of an HCCI Engine With Negative Valve Overlap

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Laura Manofsky Olesky ◽  
Jiri Vavra ◽  
Dennis Assanis ◽  
Aristotelis Babajimopoulos
Keyword(s):  
Combustion Stability ◽  
Residual Fraction ◽  
Nox Emissions ◽  
Indicated Mean Effective Pressure ◽  
Hcci Combustion ◽  
Final Study ◽  
Temperature Constant ◽  
Gas Dilution ◽  
Negative Valve Overlap ◽  
Valve Overlap

Homogeneous charge compression ignition (HCCI) has the potential to reduce both fuel consumption and NOx emissions compared to normal spark-ignited (SI) combustion. For a relatively low compression ratio engine, high unburned temperatures are needed to initiate HCCI combustion, which is achieved with large amounts of internal residual or by heating the intake charge. The amount of residual in the combustion chamber is controlled by a recompression valve strategy, which relies on negative valve overlap (NVO) to trap residual gases in the cylinder. A single-cylinder research engine with fully-flexible valve actuation is used to explore the limits of HCCI combustion phasing at a load of ∼3 bar gross indicated mean effective pressure (IMEPg). This is done by performing two individual sweeps of (a) internal residual fraction (via NVO) and (b) intake air temperature to control combustion phasing. It is found that increasing both of these variables advances the phasing of HCCI combustion, which leads to increased NOx emissions and a higher ringing intensity. On the other hand, a reduction in these variables leads to greater emissions of CO and HC, as well as a decrease in combustion stability. A direct comparison of the two sweeps suggests that the points with elevated intake temperatures are more prone to ringing as combustion is advanced and less prone to instability and misfire as combustion is retarded. This behavior can be explained by compositional differences (air versus residual gas dilution) which lead to variations in burn rate and peak temperature. As a final study, two additional NVO sweeps are performed while holding intake temperature constant at 30 °C and 90 °C. Again, it is seen that for higher intake temperatures, combustion is more susceptible to ringing at advanced timings and more resistant to instability/misfire at retarded timings.

Detailed Chemical Kinetic Simulation of Natural Gas HCCI Combustion: Gas Composition Effects and Investigation of Control Strategies

2000 ◽  
Vol 123 (2) ◽  
pp. 433-439 ◽  
Author(s):  
D. Flowers ◽  
S. Aceves ◽  
C. K. Westbrook ◽  
J. R. Smith ◽  
R. Dibble
Keyword(s):  
Natural Gas ◽  
Control Strategies ◽  
Chemical Kinetic ◽  
Gas Composition ◽  
Gas Combustion ◽  
Combustion Gas ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Natural Gas Combustion

This paper uses the HCT (hydrodynamics, chemistry and transport) chemical kinetics code to analyze natural gas combustion in an HCCI engine. The HCT code has been modified to better represent the conditions existing inside an engine, including a wall heat transfer correlation. Combustion control and low power output per displacement remain as two of the biggest challenges to obtaining satisfactory performance out of an HCCI engine, and these challenges are addressed in this paper. The paper considers the effect of natural gas composition on HCCI combustion, and then explores three control strategies for HCCI engines: DME (dimethyl ether) addition, intake heating and hot EGR addition. The results show that HCCI combustion is sensitive to natural gas composition, and an active control may be required to compensate for possible changes in composition. Each control strategy has been evaluated for its influence on the performance of an HCCI engine.

Effects of Intake Temperature on the Combustion Characteristics of HCCI Engine Fueled with n-Butanol

2014 ◽  
Vol 700 ◽  
pp. 651-654 ◽  
Author(s):  
Gang Li ◽  
Chun Hua Zhang ◽  
Ye Chong Shen ◽  
Ya Chong Shen ◽  
Jia Wang Zhou
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Pressure Rise ◽  
Combustion Characteristics ◽  
Combustion Stability ◽  
Maximum Heat ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
P Rate

In order to study the influence of intake temperature on the combustion characteristics of HCCI engine fueled with n-butanol, the 2nd cylinder of a water-cooled, naturally aspirated and double-cylinders diesel engine was converted into HCCI combustion mode. The cylinder pressure (P), rate of pressure rise (dp/dφ), heat release rate (dQ/dφ) and cycle-to-cycle variations (CCV) were compared and analyzed by bench tests under the conditions with different intake temperatures at engine speed of 1000r/min, excess air coefficient of 2.5. The experiment results show that the peak pressure (Pmax), the peak rate of pressure rise and maximum heat release rate tend to rise and the peak arrives in advance with the increase of intake temperature. As the intake temperature rises, the coefficient of variation for Pmaxreduces and combustion stability increases.

A Multi-Cylinder HCCI Engine Model for Control

2004 ◽  
Author(s):  
Jason S. Souder ◽  
Parag Mehresh ◽  
J. Karl Hedrick ◽  
Robert W. Dibble
Keyword(s):  
Design Process ◽  
Control Design ◽  
The Other ◽  
Variable Valve Timing ◽  
Valve Timing ◽  
Coupling Effects ◽  
Hcci Engine ◽  
Engine Model ◽  
Hcci Engines ◽  
Variable Valve

Homogeneous charge compression ignition (HCCI) engines are a promising engine technology due to their low emissions and high efficiencies. Controlling the combustion timing is one of the significant challenges to practical HCCI engine implementations. In a spark-ignited engine, the combustion timing is controlled by the spark timing. In a Diesel engine, the timing of the direct fuel injection controls the combustion timing. HCCI engines lack such direct in-cylinder mechanisms. Many actuation methods for affecting the combustion timing have been proposed. These include intake air heating, variable valve timing, variable compression ratios, and exhaust throttling. On a multi-cylinder engine, the combustion timing may have to be adjusted on each cylinder independently. However, the cylinders are coupled through the intake and exhaust manifolds. For some of the proposed actuation methods, affecting the combustion timing on one cylinder influences the combustion timing of the other cylinders. In order to implement one of these actuation methods on a multi-cylinder engine, the engine controller must account for the cylinder-to-cylinder coupling effects. A multi-cylinder HCCI engine model for use in the control design process is presented. The model is comprehensive enough to capture the cylinder-to-cylinder coupling effects, yet simple enough for the rapid simulations required by the control design process. Although the model could be used for controller synthesis, the model is most useful as a starting point for generating a reduced-order model, or as a plant model for evaluating potential controllers. Specifically, the model includes the dynamics for affecting the combustion timing through exhaust throttling. The model is readily applicable to many of the other actuation methods, such as variable valve timing. Experimental results validating the model are also presented.

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