Catalytic Combustion Systems for Microscale Gas Turbine Engines

2005 ◽  
Vol 129 (1) ◽  
pp. 49-60 ◽  
Author(s):  
C. M. Spadaccini ◽  
J. Peck ◽  
I. A. Waitz
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Surface Area ◽  
Power Density ◽  
Mass Flow ◽  
Catalytic Combustion ◽  
Flow Reactor ◽  
Reaction Rates ◽  
Design Parameters ◽  
Heterogeneous Catalytic

As part of an ongoing effort to develop a microscale gas turbine engine for power generation and micropropulsion applications, this paper presents the design, modeling, and experimental assessment of a catalytic combustion system. Previous work has indicated that homogenous gas-phase microcombustors are severely limited by chemical reaction timescales. Storable hydrocarbon fuels, such as propane, have been shown to blow out well below the desired mass flow rate per unit volume. Heterogeneous catalytic combustion has been identified as a possible improvement. Surface catalysis can increase hydrocarbon-air reaction rates, improve ignition characteristics, and broaden stability limits. Several radial inflow combustors were micromachined from silicon wafers using deep reactive ion etching and aligned fusion wafer bonding. The 191mm3 combustion chambers were filled with platinum-coated foam materials of various porosity and surface area. For near stoichiometric propane-air mixtures, exit gas temperatures of 1100K were achieved at mass flow rates in excess of 0.35g∕s. This corresponds to a power density of ∼1200MW∕m3; an 8.5-fold increase over the maximum power density achieved for gas-phase propane-air combustion in a similar geometry. Low-order models, including time-scale analyses and a one-dimensional steady-state plug-flow reactor model, were developed to elucidate the underlying physics and to identify important design parameters. High power density catalytic microcombustors were found to be limited by the diffusion of fuel species to the active surface, while substrate porosity and surface area-to-volume ratio were the dominant design variables.

Catalytic Combustion Systems for Micro-Scale Gas Turbine Engines

2005 ◽  
Author(s):  
C. M. Spadaccini ◽  
J. Peck ◽  
I. A. Waitz
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Surface Area ◽  
Power Density ◽  
Mass Flow ◽  
Catalytic Combustion ◽  
Reaction Rates ◽  
Design Parameters ◽  
Micro Scale ◽  
Heterogeneous Catalytic

As part of an ongoing effort to develop a micro-scale gas turbine engine for power generation and micropropulsion applications, this paper presents the design, modeling, and experimental assessment of a catalytic combustion system. Previous work has indicated that homogenous gas-phase microcombustors are severely limited by chemical reaction time-scales. Storable hydrocarbon fuels, such as propane, have been shown to blowout well below the desired mass flow rate per unit volume. Heterogeneous catalytic combustion has been identified as a possible improvement. Surface catalysis can increase hydrocarbon-air reaction rates, improve ignition characteristics, and broaden stability limits. Several radial inflow combustors were micromachined from silicon wafers using Deep Reactive Ion Etching (DRIE) and aligned fusion wafer bonding. The 191 mm3 combustion chambers were filled with platinum coated foam materials of various porosity and surface area. For near stoichiometric propane-air mixtures, exit gas temperatures of 1100 K were achieved at mass flow rates in excess of 0.35 g/s. This corresponds to a power density of approximately 1200 MW/m3; an 8.5-fold increase over the maximum power density achieved for gas-phase propane-air combustion in a similar geometry. Low order models including time-scale analyses and a one-dimensional steady-state plug-flow reactor model, were developed to elucidate the underlying physics and to identify important design parameters. High power density catalytic microcombustors were found to be limited by the diffusion of fuel species to the active surface, while substrate porosity and surface area-to-volume ratio were the dominant design variables.

CFD Modeling of a Catalytic Flat Plate Fuel Reformer for Hydrogen Generation

2010 ◽  
Author(s):  
Kranthi K. Gadde ◽  
Panini K. Kolavennu ◽  
Susanta K. Das ◽  
K. J. Berry
Keyword(s):  
Flat Plate ◽  
Catalytic Combustion ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Design Parameters ◽  
Practical Implementation ◽  
Channel Height ◽  
Inlet Temperature ◽  
Two Dimensional

In this study, steam reforming of methane coupled with methane catalytic combustion in a catalytic plate reactor is studied using a two-dimensional mathematical model for co-current flow arrangement. A two-dimensional approach makes the model more realistic by increasing its capability to capture the effect of parameters such as catalyst thickness, reaction rates, inlet temperature and velocity, and channel height, and eliminates the uncertainties introduced by heat and mass transfer coefficients used in one-dimensional models. In our work, we simulate the entire flat plate reformer (both reforming side and combustion side) and carry out parametric studies related to channel height, inlet velocities, and catalyst layer thickness that can provide guidance for the practical implementation of such design. The operating conditions chosen make possible a comparison of the catalytic plate reactor and catalytic combustion analysis with the conventional steam reformer. The CFD results obtained in this study will be very helpful to understand the optimization of design parameters to build a first generation prototype.

scholarly journals Catalytic Combustion of Natural Gas Over Supported Platinum: Flow Reactor Experiments and Detailed Numerical Modeling

1996 ◽  
Author(s):  
Tami C. Bond ◽  
Ryan A. Noguchi ◽  
Chen-Pang Chou ◽  
Rajiv K. Mongia ◽  
Jyh-Yuan Chen ◽  
...  
Keyword(s):  
Numerical Model ◽  
Natural Gas ◽  
Gas Phase ◽  
Conversion Rate ◽  
Catalytic Combustion ◽  
Flow Reactor ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Fuel Conversion ◽  
Conversion Rates

The use of a noble-metal combustion catalyst such as platinum or palladium in a natural-gas fired turbine can lower NOx (nitrogen oxides, consisting of both NO and NO2) emissions for two reasons. First, most of the combustion occurs on the catalyst surface; surface production of NOx is low or nonexistent. Second, the catalyst permits low temperature combustion below the traditional lean limit, thus inhibiting NOx formation routes in the gas phase. Due to the complexity of the catalytic combustion process, the catalyst has traditionally been modeled as a “black box” that produces a desired amount of fuel conversion. While this approach has been useful for proof-of-concept studies, we expect practical applications to emerge from a greater understanding of the details of the catalytic combustion process. We have constructed a numerical model of catalytic combustion based on the well-accepted CHEMKIN chemical kinetics formalism for gas-phase and surface chemistry. To support the model development, we built a research combustor. We present measured and modeled axial profiles of temperature, fuel conversion, and pollutant emissions for natural-gas combustion over platinum catalysts supported on ceramic honeycomb monoliths. NOx emissions are below 1 ppm, and CO is observed at ppm levels. The data are taken at several lean equivalence ratios and flow rates. Fuel conversion rates occur in two regimes: a low, constant conversion rate and a higher conversion rate that increases linearly with equivalence ratio. The agreement of the numerical model with the measured data is good at temperatures below 900 K; above this temperature, fuel conversion is underpredicted by as much as a factor of two. The predicted surface ignition temperatures agree well with the measured values. Results from the numerical model indicate that the fractional conversion rate of fuel has a linear dependence on the fraction of available surface reaction sites.

Research on Mechanisms and Applications of Catalytic Combustion of Natural Gas

2010 ◽  
Author(s):  
Shihong Zhang ◽  
Ning Li
Keyword(s):  
Natural Gas ◽  
Gas Phase ◽  
Thermal Efficiency ◽  
Catalytic Combustion ◽  
Flow Reactor ◽  
Atmospheric Temperature ◽  
Pollutant Emissions ◽  
Gas Phase Oxidation ◽  
Temperature And Pressure ◽  
Unburned Fuel

This article discussed the thermal efficiency, stability, and pollutant emissions characteristics of the combustion of lean natural gas-air mixtures in Pd metal based honeycomb monoliths by means of experiments on a practical burner V. The chemistry at work in the monoliths was then investigated using fundamental experimental reactors, namely the stagnation point flow reactor or SPFR. It was found that catalytic combustion inhibited the extent of gas-phase oxidation and increased the surface temperature of homogeneous ignition. According to the applications of catalytic combustion in the condenser boiler, the data of catalytic combustion condenser boiler V were measured at atmospheric temperature and pressure. The study also showed that more than 100% of its thermal efficiency was found possible while preserving near zero pollutant emissions. For all the catalysts tested, flow rates, and mixture compositions of natural gas and air used here, no CO, unburned fuel nor NOx were detected as long as surface combustion was taking place.

Hybrid Catalytic Combustion for Stationary Gas Turbine: Concept and Small Scale Test Results

1987 ◽  
Author(s):  
Tomiaki Furuya ◽  
Terunobu Hayata ◽  
Susumu Yamanaka ◽  
Junji Koezuka ◽  
Toshiyuki Yoshine ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Gas Turbines ◽  
Catalytic Combustion ◽  
Small Scale ◽  
Inlet Temperature ◽  
Test Results ◽  
Turbine Inlet Temperature ◽  
Scale Test ◽  
Near Future

Catalytic combustion for gas turbine applications has been investigated. Its significant advantages in reducing combustor emissions, particularly nitrogen oxides (NOx), have been shown. One of the main problems in regard to developing a catalytic combustor is the durability of catalysts, because the catalysts deteriorate during high temperature operation, which is normal for current gas turbines and near future gas turbines. The hybrid catalytic combustion concept has advantages concerned with catalyst durability. This paper shows its concept and small scale test results. This hybrid catalytic combustion concept comprises the following steps; premix fuel and air for a catalyst-packed zone; operate catalysts at rather low temperatures, to prolong catalyst life; add fresh fuel into the stream at the catalyst-packed zone outlet, where gas phase combustion occurs completely without a catalyst; add dilution air into the stream at the gas phase combustion zone outlet with a by-pass valve. Experimental data and analyses indicated that this hybrid catalytic combustion has a potential of being applicable to current gas turbines (turbine inlet temperature is about 1100°C) and near future gas turbines (turbine inlet temperature is about 1300°C).

Modeling of a Catalytic Flat Plate Fuel Reformer for Hydrogen-Rich Reformate Fuel

2013 ◽  
Author(s):  
Susanta K. Das ◽  
Kranthi K. Gadde
Keyword(s):  
Flat Plate ◽  
Catalytic Combustion ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Design Parameters ◽  
Practical Implementation ◽  
Channel Height ◽  
Inlet Temperature ◽  
Optimized Design ◽  
Two Dimensional

In this study, using a two-dimensional computational fluid dynamics (CFD) model with co-current flow arrangement, steam reforming of methane coupled with methane catalytic combustion in a catalytic plate reactor is investigated. The two-dimensional approach makes the model more realistic by increasing its capability to capture the effect of design parameters such as catalyst thickness, reaction rates, inlet temperature and velocity, and channel height, and eliminates the uncertainties introduced by heat and mass transfer coefficients used in one-dimensional models. In our work, we simulate the entire flat plate reformer electro-kinetics and carry out parametric studies related to design matrices that can provide guidance for the practical implementation of such design. The operating conditions are chosen in such a way which makes possible a good comparison of the catalytic plate reactor and catalytic combustion analysis with the conventional steam reformer. The CFD results obtained in this study is very helpful to understand the optimized design parameters to build a first generation prototype.

GAS-PHASE CHEMISTRY OF MOLYBDENUM CLUSTERS

1996 ◽  
Vol 03 (01) ◽  
pp. 675-678 ◽  
Author(s):  
D.M. RAYNER ◽  
L. LIAN ◽  
S.A. MITCHELL ◽  
P.A. HACKETT
Keyword(s):  
Gas Phase ◽  
Flow Reactor ◽  
Molecular Nitrogen ◽  
Negative Temperature ◽  
Bound State ◽  
Reaction Rates ◽  
Laser Vaporization ◽  
Dissociative Chemisorption ◽  
Kinetic Measurements ◽  
Molybdenum Clusters

The kinetics of reactions of molybdenum clusters, Mo n, n=1–25, in the pressure range 0.4–4 Torr, and temperature range 270–380 K, have been investigated using a large-bore, He-buffered, fast-flow reactor equipped with a laser-vaporization source for the production of clusters. The reactor is designed to make kinetic measurements on neutral metal clusters in the gas phase under well-defined pressures and temperatures. We discuss a new version of the instrument in which LIF techniques, used previously to monitor atoms and dimers, are replaced by laser ionization, time-of-flight mass spectrometry (TOFMS) in order to monitor larger clusters. The new version of the reactor has been tested against known reactions of Ti atoms. Examples of the reactor’s performance are taken from studies performed on Mon cluster reactivity. In particular we summarize some results on the dissociative chemisorption of molecular nitrogen, where large cluster-size effects are found. In some cases a negative-temperature dependence of the kinetics indicates the involvement of a precursor bound state and leads to conclusions concerning the shape of the potential-energy surface and how subtle changes associated with the cluster’s geometric structure might profoundly alter reaction rates.

scholarly journals Rugae-like FeP nanocrystal assembly on a carbon cloth: an exceptionally efficient and stable cathode for hydrogen evolution

Nanoscale ◽  
2015 ◽  
Vol 7 (25) ◽  
pp. 10974-10981 ◽  
Author(s):  
Xiulin Yang ◽  
Ang-Yu Lu ◽  
Yihan Zhu ◽  
Shixiong Min ◽  
Mohamed Nejib Hedhili ◽  
...  
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Hydrogen Evolution ◽  
Hydrogen Generation ◽  
High Surface ◽  
High Surface Area ◽  
Catalytic Efficiency ◽  
Carbon Cloth ◽  
Nanocrystal Assembly

High surface area FeP nanosheets on a carbon cloth were prepared by gas phase phosphidation of electroplated FeOOH, which exhibit exceptionally high catalytic efficiency and stability for hydrogen generation.

scholarly journals Study of deactivation in mesocellular foam carbon (MCF-C) catalyst used in gas-phase dehydrogenation of ethanol

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yoottapong Klinthongchai ◽  
Seeroong Prichanont ◽  
Piyasan Praserthdam ◽  
Bunjerd Jongsomjit
Keyword(s):  
Catalytic Activity ◽  
Pore Size ◽  
Gas Phase ◽  
Surface Area ◽  
Active Sites ◽  
Operating Temperature ◽  
Coke Formation ◽  
Ethanol Conversion ◽  
Deactivation Of Catalyst ◽  
Dehydrogenation Of Ethanol

AbstractMesocellular foam carbon (MCF-C) is one the captivating materials for using in gas phase dehydrogenation of ethanol. Extraordinary, enlarge pore size, high surface area, high acidity, and spherical shape with interconnected pore for high diffusion. In contrary, the occurrence of the coke is a majority causes for inhibiting the active sites on catalyst surface. Thus, this study aims to investigate the occurrence of the coke to optimize the higher catalytic activity, and also to avoid the coke formation. The MCF-C was synthesized and investigated using various techniques. MCF-C was spent in gas-phase dehydrogenation of ethanol under mild conditions. The deactivation of catalyst was investigated toward different conditions. Effects of reaction condition including different reaction temperatures of 300, 350, and 400 °C on the deactivation behaviors were determined. The results indicated that the operating temperature at 400 °C significantly retained the lowest change of ethanol conversion, which favored in the higher temperature. After running reaction, the physical properties as pore size, surface area, and pore volume of spent catalysts were decreased owing to the coke formation, which possibly blocked the pore that directly affected to the difficult diffusion of reactant and caused to be lower in catalytic activity. Furthermore, a slight decrease in either acidity or basicity was observed owing to consumption of reactant at surface of catalyst or chemical change on surface caused by coke formation. Therefore, it can remarkably choose the suitable operating temperature to avoid deactivation of catalyst, and then optimize the ethanol conversion or yield of acetaldehyde.

scholarly journals Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 507
Author(s):  
Chrysovalantis C. Templis ◽  
Nikos G. Papayannakos
Keyword(s):  
Heat Transfer ◽  
Flow Reactor ◽  
Catalytic Converter ◽  
Reaction Rates ◽  
Cfd Model ◽  
Automotive Exhaust ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Mass And Heat Transfer

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

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