scholarly journals Assessment of CO2 and NOx Emissions in Intercooled Pulsed Detonation Turbofan Engines

2018 ◽  
Author(s):  
Carlos Xisto ◽  
Olivier Petit ◽  
Tomas Grönstedt ◽  
Anders Lundbladh
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Simulation Tool ◽  
Trade Off ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Pulsed Detonation ◽  
Detonation Combustion ◽  
Aero Engine

In the present paper, the synergistic combination of inter-cooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors, operating with jet-A fuel, is developed and integrated within Chalmers University’s gas turbine simulation tool GESTPAN. The model is constructed using CFD data obtained for different combustor inlet pressure, temperature and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.

scholarly journals Assessment of CO2 and NOx Emissions in Intercooled Pulsed Detonation Turbofan Engines

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Carlos Xisto ◽  
Olivier Petit ◽  
Tomas Grönstedt ◽  
Anders Lundbladh
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Simulation Tool ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Pulsed Detonation ◽  
Detonation Combustion ◽  
Aero Engine ◽  
Computational Fluid Dynamics Cfd

In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption (SFC) and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors (PDCs), operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using computational fluid dynamics (CFD) data obtained for different combustor inlet pressure, temperature, and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.

An Intercooled Recuperative Aero Engine for Regional Jets

2014 ◽  
Author(s):  
Maximilian Kormann ◽  
Reinhold Schaber
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Thermodynamic Efficiency ◽  
Parameter Study ◽  
Nox Emissions ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Aero Engine ◽  
Aero Engines ◽  
Regional Jets

Flying requires a high power density in the propulsion system. Currently only turbofan engines can provide the required power at a low system mass. To counter a potential negative impact of aircraft emissions on global climate, the agreement Flightpath 50, created by European research establishments and industries, has set the target to reduce overall CO2 emissions from the year 2000 to 2050 by 75 %. In contrast, the air traffic volume has been growing constantly since the 1980s and will be growing further. Hence the fuel burn of aero engines has to be reduced to reach the Flightpath 50 target. High-end component technology has nearly exhausted full potential in the improvement of conventional turbofan engines. Further significant progress can only be achieved by new engine concepts. The geared turbofan has proven the feasibility of this approach. The introduction of a gear allows the IPC and LPT to run at more suitable speeds with the consequence of a lower stage count compared to conventional turbofans. According to Pratt&Whitney this will reduce the fuel burn by ”15–16% versus today’s best engines” [1]. As a next step towards Flightpath 50 MTU Aero Engines AG envisioned the Intercooled Recuperative Aero Engine (IRA) for long-haul application. This concept increases the thermodynamic efficiency of the core engine by utilizing two heat exchangers: an intercooler reduces the work which is necessary for the compression. A recuperator transfers heat of the exhaust gas to the compressed gas entering the burner. In long-haul aircraft the increased engine mass due to the heat exchangers has a lower influence on the fuel burn. To broaden the research, this paper investigates the application of the IRA for regional jets. An extensive predesign parameter study was performed to find the optimal IRA configuration for regional jets. Not only has fuel consumption been taken into consideration, additionally the influence of the increased weight of the IRA has been included. In optimum, the fuel burn on a regional mission according to this study could be reduced in the order of 1–2%. However, the overall pressure ratio is much lower compared to modern turbofan engines, which leads to relatively low NOx emissions. It allows the introduction of Lean Premixed Prevaporized (LPP) burner technology, promising an additional significant reduction in NOx emissions compared to modern turbofan engines. Compared to a longhaul application the heat exchangers are not a scaled version but the result of a cycle optimization considering the available space. The paper also gives an outlook for an innovative three dimensional heat exchanger. The novel heat exchanger arrangement promises a better integration into the annulus at turbine exit and less aerodynamical pressure losses due to 3D-effects.

First and Second Law Analysis of Intercooled Turbofan Engine

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Xin Zhao ◽  
Oskar Thulin ◽  
Tomas Grönstedt
Keyword(s):  
High Pressure ◽  
Conceptual Design ◽  
Exergy Analysis ◽  
Second Law ◽  
Turbofan Engine ◽  
Blade Height ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Aero Engine ◽  
Last Stage

Although the benefits of intercooling for aero-engine applications have been realized and discussed in many publications, quantitative details are still relatively limited. In order to strengthen the understanding of aero-engine intercooling, detailed performance data on optimized intercooled (IC) turbofan engines are provided. Analysis is conducted using an exergy breakdown, i.e., quantifying the losses into a common currency by applying a combined use of the first and second law of thermodynamics. Optimal IC geared turbofan engines for a long range mission are established with computational fluid dynamics (CFD) based two-pass cross flow tubular intercooler correlations. By means of a separate variable nozzle, the amount of intercooler coolant air can be optimized to different flight conditions. Exergy analysis is used to assess how irreversibility is varying over the flight mission, allowing for a more clear explanation and interpretation of the benefits. The optimal IC geared turbofan engine provides a 4.5% fuel burn benefit over a non-IC geared reference engine. The optimum is constrained by the last stage compressor blade height. To further explore the potential of intercooling the constraint limiting the axial compressor last stage blade height is relaxed by introducing an axial radial high pressure compressor (HPC). The axial–radial high pressure ratio (PR) configuration allows for an ultrahigh overall PR (OPR). With an optimal top-of-climb (TOC) OPR of 140, the configuration provides a 5.3% fuel burn benefit over the geared reference engine. The irreversibilities of the intercooler are broken down into its components to analyze the difference between the ultrahigh OPR axial–radial configuration and the purely axial configuration. An intercooler conceptual design method is used to predict pressure loss heat transfer and weight for the different OPRs. Exergy analysis combined with results from the intercooler and engine conceptual design are used to support the conclusion that the optimal PR split exponent stays relatively independent of the overall engine PR.

Characteristic Time Model Correlation of NOx Emissions From Lean Premixed Combustors

1995 ◽  
Author(s):  
Donald M. Newburry ◽  
Arthur M. Mellor
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Characteristic Time ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Time Model ◽  
New Model ◽  
Gas Turbine Combustors ◽  
Ratio Data ◽  
Lean Premixed

The semi–empirical characteristic time model (CTM) has been used previously to correlate and predict emissions data from conventional diffusion flame, gas turbine combustors. The form of the model equation was derived for NOx emissions from laboratory flameholders and then extended to conventional gas turbine combustors. The model relates emissions to the characteristic times of distinct combustion subprocesses, with empirically determined model constants. In this paper, a new model is developed for lean premixed (LP) NOx emissions from a perforated plate flameholder combustor burning propane fuel. Several modifications to the diffusion flame CTM were required, including a new activation energy and a more complicated dependence on combustor pressure. Appropriate model constants were determined from the data, and the correlation results are reasonable. An attempt was made to validate the new model with LP NOx data for a different but geometrically similar flameholder operating at lower pressures. The predictions are good for the low equivalence ratio data. However, a systematic error in the reported equivalence ratios may be adversely affecting the predictions of the higher equivalence ratio data through the calculated adiabatic flame temperature.

Implication of Different Fuel Injector Configurations for Hydrogen Fuelled Micromix Combustors

2011 ◽  
Author(s):  
Bhupendra Khandelwal ◽  
Yingchun Li ◽  
Priyadarshini Murthy ◽  
Vishal Sethi ◽  
Riti Singh
Keyword(s):  
Gas Turbine ◽  
Thermal Energy ◽  
Combustion Zone ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustors ◽  
The Impact

A design of a hydrogen fuelled micromix concept based combustor is proposed in this paper. The proposed micromix concept based combustor yields improved mixing, which leads to wider flammability range of the hydrogen-air flames compared to conventional kerosene and micromix concept based combustors. This improved mixing allows the combustion zone to operate at a much lower equivalence ratio than the conventional kerosene based and micromix concept based combustors considered in this study. Furthermore, when burning hydrogen the thermal energy radiated to the surroundings is lower (as the result of using lower equivalence ratio) than that of kerosene, consequently resulting in an increased liner life and lower cooling requirement. The aim of this paper is to highlight the impact of using hydrogen as a fuel in gas turbine combustors. It is perceived that this new micromix concept based combustor would also help in achieving low emissions and better performance. Possibilities for lowering NOx emissions when using hydrogen as a fuel in new designs of micromix combustor are also discussed.

Numerical Study on the Reduction of NOx Emissions From Pulse Detonation Combustion

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Neda Djordjevic ◽  
Niclas Hanraths ◽  
Joshua Gray ◽  
Phillip Berndt ◽  
Jonas Moeck
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Emissions Reduction ◽  
Nox Emissions ◽  
Primary Methods ◽  
Detonation Cell ◽  
Pulse Detonation ◽  
Detonation Combustion

A change in the combustion concept of gas turbines from conventional isobaric to constant volume combustion, such as in pulse detonation combustion (PDC), promises a significant increase in gas turbine efficiency. Current research focuses on the realization of reliable PDC operation and its challenging integration into a gas turbine. The topic of pollutant emissions from such systems has so far received very little attention. Few rare studies indicate that the extreme combustion conditions in PDC systems can lead to high emissions of nitrogen oxides (NOx). Therefore, it is essential already at this stage of development to begin working on primary measures for NOx emissions reduction if commercialization is to be feasible. The present study evaluates the potential of different primary methods for reducing NOx emissions produced during PDC of hydrogen. The considered primary methods involve utilization of lean combustion mixtures or its dilution by steam injection or exhaust gas recirculation. The influence of such measures on the detonability of the combustion mixture has been evaluated based on detonation cell sizes modeled with detailed chemistry. For the mixtures and operating conditions featuring promising detonability, NOx formation in the detonation wave has been simulated by solving the one-dimensional (1D) reacting Euler equations. The study enables an insight into the potential and limitations of considered measures for NOx emissions reduction and lays the groundwork for optimized operation of PDC systems.

Turbo Fans With Very High Bypass Ratio but Acceptable Dimensions

2008 ◽  
Author(s):  
Uwe L. H. Schmidt-Eisenlohr ◽  
Oliver E. Kosing
Keyword(s):  
Noise Level ◽  
Nox Emissions ◽  
Commercial Aircraft ◽  
Innovative Design ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Environmental Goals ◽  
Design Options ◽  
Bypass Ratio ◽  
Very High

Turbofan engines for commercial aircraft will have to improve substantially in fuel burn, noise level and NOx emissions to fulfil the ACARE 2020 environmental goals. No doubt very high bypass ratios (VHBR) will be necessary to achieve the ambitious noise reduction targets. But weight and drag of the nacelle cannot increase further and under wing installation must always be feasible. Several innovative design options such as counter rotating turbo components, air breathing nacelle, and off axis core are presented and discussed in the paper which could help to overcome the increasing dimensions of the fan and the nacelle with increasing bypass ratio.

Assessment of a Gas Turbine NOx Reduction Potential Based on a Spatiotemporal Unmixedness Parameter

2013 ◽  
Author(s):  
Stefan Dederichs ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Christian Beck ◽  
Werner Krebs ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Flame Front ◽  
Gas Turbine ◽  
Equivalence Ratio ◽  
Reduction Potential ◽  
Nox Emissions ◽  
Reaction Progress ◽  
One Dimensional ◽  
Mixing Quality

The paper presents a one-dimensional approach to assess the reduction potential of NOx emissions for lean premixed gas turbine combustion systems. NOx emissions from these systems are known to be mainly caused by high temperatures; not only from an averaged perspective but especially related to poor mixing quality of fuel and air. The method separates the NOx chemistry in the flame front zone and the post flame zone (slow reaction). A one-dimensional treatment enables the use of detailed chemistry. A look up table parameterized by reaction progress and equivalence ratio is used to improve the computational efficiency. The influence of mixing quality is taken into account by a probability density function of the fuel element based equivalence ratio, which itself translates into a temperature distribution. Hence, the NOx source terms are a function of reaction progress and equivalence ratio. The reaction progress is considered by means of the two-zone approach. Based on unsteady CFD data, the evolution of the probability density function with residence time has been analyzed. Two types of definitions of an unmixedness quantity are considered. One definition accounts for spatial as well as temporal fluctuations and the other is based on the mean spatial distribution. They are determined at the location of the flame front. The paper presents a comparison of the modeled results with experimental data. A validation and application have shown very good quantitative and qualitative agreement with the measurements. The comparison of the unmixedness definitions has proven the necessity of unsteady simulations. A general emissions - unmixedness correlation can be derived for a given combustion system.

NOx-Formation and CO-Burnout in Water Injected, Premixed Natural Gas Flames at Typical Gas Turbine Combustor Residence Times

2017 ◽  
Author(s):  
Stephan Lellek ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Water Droplet ◽  
Equivalence Ratio ◽  
Water Injection ◽  
Power Production ◽  
Nox Emissions ◽  
Residence Times ◽  
Gas Turbine Combustor ◽  
Reaction Progress ◽  
Progress Variable

With the transition of the power production markets towards renewable energy sources an increased demand for flexible, fossil based power production systems arises. Steep load gradients and a high range of flexibility make gas turbines a core technology in this ongoing change. In order to further increase this flexibility research on power augmentation of premixed gas turbine combustors is conducted at the Lehrstuhl für Thermodynamik, TU München. Water injection in gas turbine combustors allows for the simultaneous control of NOx emissions as well as the increase of the power output of the engine and has therefore been transferred to a premixed combustor at lab scale. So far stable operation of the system has been obtained for water-to-fuel ratios up to 2.25 at constant adiabatic flame temperatures. This paper focuses on the effects of water injection on pollutant formation in premixed gas turbine flames. In order to guarantee for high practical relevance experimental measurements are conducted at typical preheating temperatures and common gas turbine combustor residence times of about 20 ms. Spatially resolved and global species measurements are performed in an atmospheric single burner test rig for typical adiabatic flame temperatures between 1740 and 2086 K. Global measurements of NOx and CO emissions are shown for a wide range of equivalence ratios and variable water-to-fuel ratios. Cantera calculations are used to identify non-equilibrium processes in the measured data. To get a close insight into the emission formation processes in water injected flames local concentration measurements are used to calculate distributions of the reaction progress variable. Finally, to clarify the influence of spray quality on the composition of the exhaust gas a variation of the water droplet diameters is done. For rising water content at constant adiabatic flame temperature the NOx emissions can be held constant, whereas CO concentrations increase. On the contrary, both values decrease for measurements at constant equivalence ratio and reduced flame temperatures. Further analysis of the data shows the close dependency of CO concentration on the equivalence ratio, however, due to the water addition a shift of the CO curves can be detected. In the local measurements changes in the distribution of the reaction progress variable and an increase of the flame length were detected for water injected flames along with changes of the maximum as well as the averaged CO values. Finally, a strong influence of water droplet size on NOx and CO formation is shown for constant operating conditions.

NOx-Formation and CO-Burnout in Water-Injected, Premixed Natural Gas Flames at Typical Gas Turbine Combustor Residence Times

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Stephan Lellek ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Water Droplet ◽  
Equivalence Ratio ◽  
Water Injection ◽  
Power Production ◽  
Nox Emissions ◽  
Residence Times ◽  
Gas Turbine Combustor ◽  
Reaction Progress ◽  
Progress Variable

With the transition of the power production markets toward renewable energy sources, an increased demand for flexible, fossil-based power production systems arises. Steep load gradients and a high range of flexibility make gas turbines a core technology in this ongoing change. In order to further increase this flexibility research on power augmentation of premixed gas turbine combustors is conducted at the Lehrstuhl für Thermodynamik, TU München. Water injection in gas turbine combustors allows for the simultaneous control of NOx emissions as well as the increase of the power output of the engine and has therefore been transferred to a premixed combustor at lab scale. So far stable operation of the system has been obtained for water-to-fuel ratios up to 2.25 at constant adiabatic flame temperatures. This paper focuses on the effects of water injection on pollutant formation in premixed gas turbine flames. In order to guarantee for high practical relevance, experimental measurements are conducted at typical preheating temperatures and common gas turbine combustor residence times of about 20 ms. Spatially resolved and global species measurements are performed in an atmospheric single burner test rig for typical adiabatic flame temperatures between 1740 and 2086 K. Global measurements of NOx and CO emissions are shown for a wide range of equivalence ratios and variable water-to-fuel ratios. Cantera calculations are used to identify nonequilibrium processes in the measured data. To get a close insight into the emission formation processes in water-injected flames, local concentration measurements are used to calculate distributions of the reaction progress variable. Finally, to clarify the influence of spray quality on the composition of the exhaust gas, a variation of the water droplet diameters is done. For rising water content at constant adiabatic flame temperature, the NOx emissions can be held constant, whereas CO concentrations increase. On the contrary, both values decrease for measurements at constant equivalence ratio and reduced flame temperatures. Further analysis of the data shows the close dependency of CO concentration on the equivalence ratio; however, due to the water addition, a shift of the CO curves can be detected. In the local measurements, changes in the distribution of the reaction progress variable and an increase of the flame length were detected for water-injected flames along with changes of the maximum as well as the averaged CO values. Finally, a strong influence of water droplet size on NOx and CO formation is shown for constant operating conditions.

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