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.

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.

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.

Numerical modeling of high velocity impact in sandwich panels with honeycomb core and composite skin including composite progressive damage model

2018 ◽  
Vol 22 (8) ◽  
pp. 2768-2795 ◽  
Author(s):  
Meysam Khodaei ◽  
Mojtaba Haghighi-Yazdi ◽  
Majid Safarabadi
Keyword(s):  
Numerical Model ◽  
Sandwich Panel ◽  
Material Model ◽  
Absorption Capacity ◽  
Numerical Results ◽  
Ballistic Impact ◽  
Experimental Results ◽  
Ballistic Limit ◽  
Honeycomb Core ◽  
Damage Initiation

In this paper, a numerical model is developed to simulate the ballistic impact of a projectile on a sandwich panel with honeycomb core and composite skin. To this end, a suitable material model for the aluminum honeycomb core is used taking the strain-rate dependent properties into account. To validate the ballistic impact of the projectile on the honeycomb core, numerical results are compared with the experimental results available in literature and ballistic limit velocities are predicted with good accuracy. Moreover, to achieve composite skin material model, a VUMAT subroutine including damage initiation based on Hashin’s seven failure criteria and damage evolution based on MLT approach modulus degradation is used. To validate the composite material model VUMAT subroutine, the ballistic limit velocities of the projectile impact on the composite laminates are predicted similar to the numerical results presented by other researchers. Next, the numerical model of the sandwich panel ballistic impact at different velocities is compared with the available experimental results in literature, and energy absorption capacity of the sandwich panel is predicted accurately. In addition, the numerical model simulated the sandwich panel damage mechanisms in different stages similar to empirical observations. Also, the composite skin damages are investigated based on different criteria damage contours.

Experimental Validation of a Dynamic Numerical Model for Timing Belt Drives Behavior Simulation

2000 ◽  
Author(s):  
Lionel Manin ◽  
Daniel Play ◽  
Patrick Soleilhac
Keyword(s):  
Numerical Model ◽  
Dynamic Behavior ◽  
Operation Time ◽  
Transmission Error ◽  
Numerical Results ◽  
Experimental Results ◽  
Medium Size ◽  
Behavior Simulation ◽  
Dynamic Transmission Error ◽  
Timing Belt

Abstract The behavior of timing belts used in automotive applications have to be defined and predicted at the preliminary design phases. Numerical simulations replace progressively experimental determinations that are time and money consuming. The object of the work was to qualify from experimental results a timing belt drive numerical model. The model simulates the dynamic behavior versus time of any kind of tooth belt power transmissions. The model architecture, originalities and capabilities have been already presented, and the purpose is now to compare in details numerical and experimental results. The experimental qualification has been carried out on a laboratory test bench with a medium size engine valve controlled distribution made of 3 pulleys and a tensioner. Tensions, camshaft torque, pulleys speeds and angular acylisms, dynamic transmission error between camshaft and crankshaft pulleys have been measured. Numerous tests have been made for different running conditions by changing : speed, angular acyclism, camshaft torque, setting tension. Several phenomena and influence of parameters have been identified, as the pulley eccentricity effect on camshaft torque, span tensions, and transmission error. Part of the experimental results are used as entries of the model : camshaft torque, crankshaft instantaneous speed, transmission error due to pulley eccentricities. Further, comparisons with the numerical results were made. Experimental and numerical results of tension, angular acyclism, dynamic transmission error, versus operation time are compared for the different tests performed. The agreement is good and shows that the model developed allows to simulate dynamic behavior of timing belt with high degree of confidence.

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.

A Physics-Based Modeling Approach of a Natural Gas HCCI Engine

2012 ◽  
Author(s):  
Marwa W. AbdelGawad ◽  
Reza Tafreshi ◽  
Reza Langari
Keyword(s):  
Internal Combustion Engines ◽  
Integral Model ◽  
Compression Ignition ◽  
Valve Closure ◽  
Nitric Oxides ◽  
Intake Valve ◽  
Ignition Timing ◽  
Hcci Engine ◽  
Main Challenge ◽  
Hcci Engines

Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies, in addition to low nitric oxides and particulate matter. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a “fusion” between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making the control of combustion timing difficult. To be able to control ignition timing, a physics-based model is developed to model the full HCCI engine cycle while taking into consideration cycle-to-cycle transitions. Exhaust Gas Recirculation is used to control combustion timing while the temperature at intake valve closure will serve as the parameter that represents the desired ignition timing. The Modified Knock Integral model defines the necessary relationship between ignition timing and temperature at intake valve closure. Validation of the developed model is performed by determining the ignition timing under varying conditions. Results are shown to be in accordance with data acquired from a single-cylinder model developed using a sophisticated engine simulation program, GT-Power.

Modeling Cylinder-to-Cylinder Coupling in Multi-Cylinder HCCI Engines Incorporating Reinduction

2007 ◽  
Author(s):  
Anup M. Kulkarni ◽  
Gayatri H. Adi ◽  
Gregory M. Shaver
Keyword(s):  
Internal Combustion Engines ◽  
Control Strategies ◽  
Combustion Products ◽  
Exhaust Manifold ◽  
Gas Temperature ◽  
Subtle Difference ◽  
Hcci Engine ◽  
Variable Valve Actuation ◽  
Hcci Engines ◽  
Valve Actuation

Residual-affected homogeneous charge compression ignition (HCCI) is a promising strategy for decreasing fuel consumption and NOx emissions in internal combustion engines. One practical approach for achieving residual-affected HCCI is by using variable valve actuation to reinduct previously exhausted combustion products. This process inherently couples neighboring engine cylinders as products exhausted by one cylinder may be reinducted by a neighboring one. In order to understand this coupling and its implication for controlling HCCI, this paper outlines a simple physics based model of a multi-cylinder HCCI engine using exhaust reinduction. It is based on a physics based model previously validated for a single cylinder, multi mode HCCI engine. The exhaust manifold model links exhaust gases from one cylinder to those of the other cylinders and also simulates the effect of exhaust reinduction from the previous cycle. Depending on the exhaust manifold geometry and orientation, the heat transfer in the manifold causes a difference in the temperature of the re-inducted product gas across the cylinders. The results show that a subtle difference in the re-inducted exhaust gas temperature results in a dramatic variation in combustion timing (approx. 3 degrees). This model provides a basis for understanding the steady state behavior and also for developing control strategies for multi-cylinder HCCI engines. The paper presents exhaust valve timing induced compression ratio modulation (via flexible valve actuation) as one of the approaches to mitigate the imbalance in combustion timing across cylinders.

Numerical Analysis of the Influence of the Padding-Plate on the Extended End-Plate Connection

2014 ◽  
Vol 578-579 ◽  
pp. 505-508
Author(s):  
Shao Qin Zhang ◽  
Lei Wu
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Numerical Simulations ◽  
Load Capacity ◽  
Numerical Results ◽  
Experimental Results ◽  
End Plate ◽  
Extended End Plate ◽  
Plate Connection

In the present paper, we investigate the effect of a padding-plate on the behavior of extended end-plate semi-rigid connections. The numerical simulations were carried out for a standard extended end-plate connection joint without padding-plate and two connection joints with 4mm and 6mm thick padding-plates. The existing experimental results verified the validity of the numerical model. The numerical results have shown that a thin padding-plate will more or less decline the carrying load capacity of the connection joint but greatly improve the connect ductility. Filling a thin padding-plate in the end-plate connection is feasible and brings the forewarning function.

scholarly journals Deformation of the Wave Field Interacting With Offshore Platforms: Comparison Between the Corresponding Results From a Numerical Model and a Wave Tank

2016 ◽  
Author(s):  
M. Hasanat Zaman ◽  
Ayhan Akinturk
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
National Research Council ◽  
Numerical Results ◽  
Experimental Results ◽  
Test Facility ◽  
Offshore Platforms ◽  
Offshore Structure ◽  
Alternating Direction ◽  
Tracking Devices

In the present research, a 3D dispersive numerical model has been developed and utilized to study the modification of the wave field in the presence of offshore structure. The Alternating Direction Implicit (ADI) algorithm has been employed for the solution of the governing equations. Relevant experiments are carried out in the Offshore Engineering Basin (OEB) of National Research Council (NRC) Canada. OEB is a 3D heavy duty 75m × 32m × 2.8m test facility equipped with modern data acquisition and tracking devices to record experimental data. Total 10 wave probes are deployed to measure the data at different locations in the Basin. Later the numerical results are compared with the experimental results. The comparisons of the numerical results show great agreement with the experimental results.

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