Mixture Quality of a Vortex Generator Premixer and Alternative Premixer Designs in the Auto-Ignition Regime of Hydrogen Air Flames

2017 ◽  
Author(s):  
Stefan Bauer ◽  
Simon Bäßler ◽  
Balbina Hampel ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Current Knowledge ◽  
Flux Ratio ◽  
Vortex Generator ◽  
Inlet Temperature ◽  
Air Temperatures ◽  
Auto Ignition ◽  
Air Mixing ◽  
Thermodynamic Conditions

The application of vortex generator premixers (VGPs) is particularly challenging for highly reactive fuels in recuperated gas turbines, because high combustor inlet temperature leads to a potential risk of premature self-ignition and flame flashback. As current knowledge does not extend to the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is conducted at the Thermodynamics Institute of the Technical University of Munich. The study is particularly focused on highly reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. The present study is focuses on fuel-air mixing at the corresponding high air temperatures. A fuel-air mixing device is required to achieve sufficient mixing quality without excessive premixer length. Vortex generators are known to be effective in augmenting the distribution of fuel injected from the tube wall over the cross section of the tube. In the range of typical gas turbine combustor inlet temperatures, the performance of VGPs has already been investigated for methane as well as for hydrogen-methane blends. The limits of operating a VGP under auto-ignition relevant conditions were presented in a previous study. In this study, the VGP’s mixture quality under these conditions is experimentally investigated. For this purpose, the existing test rig has been modified to conduct high speed PIV and MixPIV measurements. Measurements at different positions inside and downstream of the injector have been performed. Two other mixer types in addition to the VGP are investigated to determine the influence of mixture quality on auto-ignition behavior in a future study and to validate MixPIV measurements. The influence of the momentum flux ratio on mixture quality is presented for the three mixer types. Comparison shows that the VGP exhibits significantly better mixture homogeneity at the mixer exit than do the two other mixer types.

Development and Evaluation of Silicon Nitride Components for Ceramic Gas Turbine

1998 ◽  
Author(s):  
Yasushi Hara ◽  
Katsura Matsubara ◽  
Ken-ichi Mizuno ◽  
Toru Shimamori ◽  
Hiro Yoshida
Keyword(s):  
Silicon Nitride ◽  
Gas Turbines ◽  
High Speed ◽  
Gas Flow ◽  
Impact Damage ◽  
Turbine Blades ◽  
Impact Testing ◽  
Particle Impact ◽  
Inlet Temperature ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1350 °C in accordance with the project goals, we developed two silicon nitride materials with further improved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. On applying these silicon nitride ceramics to CGT engine, we evaluated various properties of silicon nitride materials considering the environment in CGT engine. Particle impact testing is one of those evaluations. Materials used in CGT engine are exposed in high speed gas flow, and impact damage of these materials is considered to be a concern. We tested ST-1 in the particle impact test. In this test, we observed fracture modes, and estimated the critical impact velocity. This paper summarizes the development of silicon nitride components, and the result of evaluations of these silicon nitride materials.

Evaluation of Two Measurement Techniques to Quantify Fuel–Air Mixing of a Gas Turbine Premixer at Atmospheric Conditions

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Wessam Estefanos ◽  
Mahmoud Hamza ◽  
Umesh Bhayaraju ◽  
San-Mou Jeng
Keyword(s):  
Reynolds Number ◽  
Momentum Flux ◽  
High Speed ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Fuel Mass ◽  
Air Mixing

In the present study, two measurement techniques are adopted to evaluate the fuel–air mixing under atmospheric conditions using an industrial fuel–air premixer. These techniques are CO2 mixing and planar laser induced fluorescence (PLIF) in water. In these techniques, CO2 and fluorescent dye are injected as fuel simulants. CO2 measurements are used to validate PLIF in water. In the CO2 technique, CO2 concentrations are converted to fuel mass fractions, whereas in the PLIF technique, a modified post processing method is used to convert the LIF signal into fuel mass fraction. The experiments are conducted at the same Reynolds number and momentum flux ratio for two injection strategies. To study the effect of the flow aerodynamics on the mixing results, high-speed particle image velocimetry (PIV) measurements are conducted in water at the same Reynolds number. A comparison of fuel concentrations measured with the CO2 and PLIF techniques shows good quantitative agreement at all momentum flux ratios. However, deviations between the two techniques are observed at locations of high fuel concentration gradients. The unsteady mixing is evaluated using the PLIF technique with high temporal resolution. Analysis of PIV and PLIF data shows that unsteady mixing is lower at regions of high fluctuations in velocity. Moreover, it is found that there is high unsteady mixing at locations of high concentration gradient.

scholarly journals Emissions Performance of a Ramburner Sector of a Mach 5 Combined-Cycle Engine

1995 ◽  
Author(s):  
Donald J. Hautman
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Combustion Efficiency ◽  
Combined Cycle ◽  
Orifice Diameter ◽  
Inlet Temperature ◽  
Nitric Oxides ◽  
Air Mixing

A research program was conducted to acquire and analyze data from a ramburner sector operating at conditions typical for a methane-fueled ramburner in a Mach 5 Turboramjet propulsion system. A combined experimental and analytical approach was used to obtain and interpret a data base suitable for ramburner design. Non-reacting Mie scattering measurements documented the fuel-air mixing as a function of fuel-injection geometry and flow conditions. Computational fluid dynamics calculations were shown to agree reasonably well with measured jet penetrations, but overpredicted the rate of mixing. An equation to calculate the average equivalence ratio as a function of orifice diameter, orifice spacing, effective duct height, flameholder momentum flux ratio, vertical distance, and downstream distance was developed from the analyses of the non-reacting data. Concentrations of carbon dioxide, carbon monoxide, oxygen, unburned hydrocarbons, and nitric oxides were measured in a ramburner sector as a function of inlet temperature, inlet Mach number, air flow rate/area, equivalence ratio, and sampling probe location. Equations were developed that relate the combustion efficiency and the nitric oxides emission index to the reaction time and residence time.

scholarly journals Status of the Automotive Ceramic Gas Turbine Development Program: Year 2 Progress

1993 ◽  
Author(s):  
Takane Itoh ◽  
Hidetomo Kimura
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Development Program ◽  
Turbine Rotor ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Engine ◽  
Basic Engine ◽  
Second Year

A seven-year program, designated “Research & Development of Automotive Ceramic Gas Turbine Engine (CGT Program)”, was started in June 1990 with the object of demonstrating the advantageous potentials of ceramic gas turbines for automotive use. This CGT-Program is conducted by PEC with the support of MITI. The basic engine is a 100-kW, single-shaft engine having a turbine inlet temperature of a 1350°C and a rotor speed of 110,000 rpm. During the second year of the program, experimental evaluation of the various components was started, including a centrifugal compressor, a radial turbine rotor, a high speed rotor system and initial ceramic hot parts. Cold and hot spin testing of ceramic rotors from three different ceramic suppliers was also initiated.

Experimental and Numerical Investigation of Confined Jets in Hot Co-Flow

2014 ◽  
Author(s):  
G. Tautschnig ◽  
E.-M. Haner ◽  
C. Hirsch ◽  
T. Sattelmayer
Keyword(s):  
Gas Turbines ◽  
Momentum Flux ◽  
Measurement Techniques ◽  
Water Channel ◽  
Combustion Process ◽  
Computational Cost ◽  
Flux Ratio ◽  
Flow Measurements ◽  
Auto Ignition ◽  
Tabulated Chemistry

Sequential staged combustion with an expansion turbine between both stages is an efficient way of extending the low emission regime of gas turbines towards very low loads. The dominating combustion regime in the second stage is auto-ignition. A confined natural gas jet in hot vitiated co-flow is investigated to obtain deeper insights in the parameters effecting auto-ignition. A generic pressurized combustion experiment is presented. Optical measurement techniques are applied to determine lift-off height and air excess ratio of the flame in the ignition region. Oxygen content of the co-flow, momentum flux ratio and pressure are varied in the experiments. Cold flow measurements are used to analyze the mixing behavior for different momentum flux ratios. Tendencies observed in the experiments are successfully simulated by a numerical method wherein the flow-, mixture- and temperature-fields are acquired using a non-reacting Realizable k-ε RANS simulation in Fluent. Mixture-PDFs obtained from water-channel measurements are used to take mixture-fluctuations into account. In a post-processing step the combustion-process is calculated with unsteady flamelet equations evaluated in Matlab. By using a progress variable approach with tabulated chemistry only two partial differential equations need to be solved. Hence the computational cost is low. With this study a low-cost numerical model for auto-ignition is demonstrated and the effect of temperature gradients in the co-flow on self-ignition is highlighted.

Evaluation of Two Measurement Techniques to Quantify Fuel-Air Mixing of a Gas Turbine Pre-Mixer at Atmospheric Conditions

2015 ◽  
Author(s):  
Wessam Estefanos ◽  
Umesh Bhayaraju ◽  
Mahmoud Hamza ◽  
San-Mou Jeng
Keyword(s):  
Reynolds Number ◽  
Momentum Flux ◽  
High Speed ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Fuel Mass ◽  
Air Mixing

In the present study, two measurement techniques are adopted to evaluate the fuel-air mixing under atmospheric conditions using an industrial fuel-air pre-mixer. These techniques are CO2 mixing and Planar Laser Induced Fluorescence (PLIF) in water. In these techniques, CO2 and fluorescent dye are injected as fuel simulants. CO2 measurements are used to validate PLIF in water. In the CO2 technique, CO2 concentrations are converted to fuel mass fractions whereas, in the PLIF technique, a modified post processing method is used to convert the LIF signal into fuel mass fraction. The experiments are conducted at the same Reynolds number and momentum flux ratio for two injection strategies. To study the effect of the flow aerodynamics on the mixing results, high speed PIV measurements are conducted in water at the same Reynolds number. A comparison of fuel concentrations measured with the CO2 and PLIF techniques shows good quantitative agreement at all momentum flux ratios. However, deviations between the two techniques are observed at high fuel concentration gradients. The unsteady mixing is evaluated using PLIF technique with high temporal resolution. Analysis of PIV and PLIF data shows that unsteady mixing is lower at regions of high fluctuations in velocity. Moreover, it is found that there is high unsteady mixing at locations where there is high concentration gradient.

Development of an Improved Hybrid Burner: Initial Operating Experience in a Gas Turbine

1996 ◽  
Author(s):  
Bernd Prade ◽  
Holger Streb ◽  
Peter Berenbrink ◽  
Bernhard Schetter ◽  
Gottfried Pyka
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Operating Experience ◽  
Liquid Fuels ◽  
Inlet Temperature ◽  
Discharge Temperature ◽  
Auto Ignition ◽  
The Stability ◽  
Base Load

Hybrid burners have demonstrated proven reliability in the premixed combustion of both natural gas and liquid fuels. NOx emission levels below 10 ppmv (gas dry, 15% O2) have been achieved in gas turbine models V94.2, V84.2 and retrofitted predecessor gas turbines. With increasing turbine inlet temperature (increasing efficiency), the pressure ratio and compressor discharge temperature will rise and auto ignition will become more critical. Therefore the development of an improved hybrid burner was an obvious necessity. Compatibility of the new burner with existing gas turbines was a basic requirement. The new burner was tested in a 10 MW Gas Turbine equipped with a SIEMENS silo combustor and in a V64.3 GT in Dresden, Germany. The paper presents the development and results of on-site measurements of NOx and CO emissions. At base toad NOx emissions below 25 ppmv were obtained by the revised hybrid (HR) burner without any combustion driven oscillation (< 5 mbar) in the V64.3. Additionaly the stability of the premixed flame was improved, so that the operation range of premix mode could be increased by three percent of base load.

scholarly journals Thermo-Economic Optimization of a Solid Oxide Fuel Cell, Gas Turbine Hybrid System

2006 ◽  
Vol 4 (2) ◽  
pp. 123-129 ◽  
Author(s):  
N. Autissier ◽  
F. Palazzi ◽  
F. Marechal ◽  
J. van Herle ◽  
D. Favrat
Keyword(s):  
Fuel Cells ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
High Efficiency ◽  
Integrated System ◽  
Solid Oxide ◽  
Inlet Temperature ◽  
Optimization Approach ◽  
Oxide Fuel

Large scale power production benefits from the high efficiency of gas-steam combined cycles. In the lower power range, fuel cells are a good candidate to combine with gas turbines. Such systems can achieve efficiencies exceeding 60%. High-temperature solid oxide fuel cells (SOFC) offer good opportunities for this coupling. In this paper, a systematic method to select a design according to user specifications is presented. The most attractive configurations of this technology coupling are identified using a thermo-economic multi-objective optimization approach. The SOFC model includes detailed computation of losses of the electrodes and thermal management. The system is integrated using pinch based methods. A thermo-economic approach is then used to compute the integrated system performances, size, and cost. This allows to perform the optimization of the system with regard to two objectives: minimize the specific cost and maximize the efficiency. Optimization results prove the existence of designs with costs from 2400$∕kW for a 44% efficiency to 6700$∕kW for a 70% efficiency. Several design options are analyzed regarding, among others, fuel processing, pressure ratio, or turbine inlet temperature. The model of a pressurized SOFC–μGT hybrid cycle combines a state-of-the-art planar SOFC with a high-speed micro-gas turbine sustained by air bearings.

Numerical Analysis of the Conceptual Design of Arrayed-Vanes Premixer for Gas Turbine Combustors Burning High-Hydrogen Fuels

2013 ◽  
Author(s):  
Zongming Yu ◽  
Xinnan Wu ◽  
Feifan Wu ◽  
Yue Wang ◽  
Wenjun Kong ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Exit Plane ◽  
Flow Disturbance ◽  
Inlet Flow ◽  
High Hydrogen ◽  
Auto Ignition ◽  
Air Mixing ◽  
Hydrogen Fuels

Using high-hydrogen fuels in industrial gas turbines is an effective way to achieve near-zero carbon emission power generation. Lean premixed combustion can effectively reduce NOx emission. However, due to the strong flashback and auto-ignition tendencies during fuel-air mixing, it is a challenge to use lean premix combustion mode of high hydrogen fuels under gas turbine operation conditions. An innovative conceptual design of arrayed-vanes premixer was proposed to achieve safe and uniform mixing of fuel and air. Inside the arrayed-vanes premixer, a cascade of mixing vanes is arranged in the axial annular air flow passage. Fuel-air mixing and flow field stretch are improved and well controlled by the arrayed vanes. The conditions of auto-ignition and flame stabilization inside the vanes are unsatisfied. Meanwhile the upstream flow disturbance will be inhibited by the arrayed vanes, which benefits combustion stability. The arrayed-vanes premixer was designed and its flow field was numerically simulated under the operation condition of F class gas turbine combustors. The flow and fuel-air mixing behavior was analyzed and compared with a typical swirl-based premixer now widely used in DLN combustors of F class gas turbines. The results show that the non-uniformity index of fuel concentration distribution at the exit plane of the arrayed-vanes premixer is 50% lower than that of the swirl-based premixer. The responses of flow field at the exit plane to the inlet flow disturbance was calculated and compared for the two types of permixer. The inlet flow disturbance includes the velocity distortion and the oscillation of the pressure. The results show that the arrayed-vanes premixer absorbs and damps the inlet flow disturbance better than the swirl-based premixer. And it exhibits highly monochromatic characteristic through the acoustic signature analysis. Furthermore, the tendencies of auto-ignition and flashback were investigated by examining the flow field and the flammability of hydrogen. The results show that there is a low risk of auto-ignition or flashback due to the short residence time and the high discharge velocity. The present study indicates that the arrayed-vanes premixer achieves ultra uniform fuel-air mixing, good adaptability to inlet flow disturbance and anti auto-ignition and flash back, which is benefit to DLN combustor designed for high-hydrogen fuels. This design will be possibly used in DLN combustors after future developments.

scholarly journals Gas Turbine Performance Enhancement for Naval Ship Propulsion using Wave Rotors

2019 ◽  
Author(s):  
A Fatsis ◽  
A S N Al Balushi
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
High Performance ◽  
Performance Enhancement ◽  
Waste Heat ◽  
Specific Power ◽  
Inlet Temperature ◽  
Wave Rotor ◽  
Turbine Inlet

The propulsion demands of high speed naval vessels often rely on gas turbines fitted in small engine rooms, producing significant amounts of power achieving thus high performance requirements. Gas turbines can be used either to provide purely mechanical propulsion, or alternatively to generate electricity, which is subsequently used by electric drives to propel the ship. However, the thermal efficiencies of gas turbines are lower than those of Diesel engines of similar power, in addition to the fact that all gas turbines are less efficient as the ambient temperature rises, particularly for aero-derivative engines. In the context of improving the performance of existing marine gas turbines with minimum modifications to their baseline configuration, this article is proposing engine’s performance enhancement by integrating a pressure wave supercharger (or wave rotor), while keeping the compressor, combustion chamber and turbine entry temperature of the baseline engine unchanged. Thermodynamic cycle analysis for two-shaft gas turbine engines configurations with and without heat exchanger to recuperate the waste heat from the exhaust gases, typical for marine propulsion is performed for the baseline engines, as well as for the topped with four-port wave rotor engines, at design point conditions and their performances are compared accordingly. Important benefits are obtained for four-port wave rotor-topped engines in comparison to the self-standing baseline engines for the whole range of engine’s operation. It is found that the higher the turbine inlet temperature is, the more the benefit gain of the wave rotor topped engine is attained in terms of efficiency and specific power. It is also concluded that the integration of wave rotor particularly favours engines operating at low compressor pressure ratios and high turbine inlet temperatures. The effect of variation of the most important parameters on performance of the topped engine is investigated. It is concluded that wave rotor topping of marine gas turbines can lead to fuel savings and power increase.

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