Adiabatic Effectiveness and Flow Field Measurements in a Realistic Effusion Cooled Lean Burn Combustor

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Becchi ◽  
Bruno Facchini ◽  
Lorenzo Mazzei ◽  
Alessio Picchi ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Injection System ◽  
Wall Region ◽  
Test Model ◽  
Nox Emissions ◽  
Lean Burn ◽  
Experimental Apparatus ◽  
Adiabatic Effectiveness ◽  
The Impact

Over the last ten years, there have been significant technological advances toward the reduction of NOx emissions from civil aircraft engines, strongly aimed at meeting stricter and stricter legislation requirements. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern combustors is represented by lean burn swirl stabilized technology. The high amount of air admitted through a lean burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown, and precessing vortex core (PVC) that may deeply interact in the near wall region of the combustor liner. This interaction makes challenging the estimation of film cooling distribution, commonly generated by slot and effusion systems. The main purpose of the present work is the characterization of the flow field and the adiabatic effectiveness due to the interaction of swirling flow, generated by real geometry injectors, and a liner cooling scheme made up of a slot injection and an effusion array. The experimental apparatus has been developed within EU project LEMCOTEC (low emissions core-engine technologies) and consists of a nonreactive three-sectors planar rig; the test model is characterized by a complete cooling system and three swirlers, replicating the geometry of a GE Avio PERM (partially evaporated and rapid mixing) injector technology. Flow field measurements have been performed by means of a standard 2D PIV (particle image velocimetry) technique, while adiabatic effectiveness maps have been obtained using PSP (pressure sensitive paint) technique. PIV results show the effect of coolant injection in the corner vortex region, while the PSP measurements highlight the impact of swirled flow on the liner film protection separating the contribution of slot and effusion flows. Furthermore, an additional analysis, exploiting experimental results in terms of heat transfer coefficient, has been performed to estimate the net heat flux reduction (NHFR) on the cooled test plate.

Adiabatic Effectiveness and Flow Field Measurements in a Realistic Effusion Cooled Lean Burn Combustor

2015 ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Becchi ◽  
Bruno Facchini ◽  
Lorenzo Mazzei ◽  
Alessio Picchi ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Injection System ◽  
Wall Region ◽  
Test Model ◽  
Nox Emissions ◽  
Lean Burn ◽  
Experimental Apparatus ◽  
Adiabatic Effectiveness ◽  
The Impact

Over the last ten years there have been significant technological advances toward the reduction of NOx emissions from civil aircraft engines, strongly aimed at meeting stricter and stricter legislation requirements. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern combustors is represented by lean burn swirl stabilized technology. The high amount of air admitted through a lean-burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown and precessing vortex core, that may deeply interact in the near wall region of the combustor liner. This interaction makes challenging the estimation of film cooling distribution, commonly generated by slot and effusion systems. The main purpose of the present work is the characterization of the flow field and the adiabatic effectiveness due to the interaction of swirling flow, generated by real geometry injectors, and a liner cooling scheme made up of a slot injection and an effusion array. The experimental apparatus has been developed within EU project LEMCOTEC and consists of a non-reactive three sectors planar rig; the test model is characterized by a complete cooling system and three swirlers, replicating the geometry of a GE Avio PERM (Partially Evaporated and Rapid Mixing) injector technology. Flow field measurements have been performed by means of a standard 2D PIV (Particle Image Velocimetry) technique, while adiabatic effectiveness maps have been obtained using PSP (Pressure Sensitive Paint) technique. PIV results show the effect of coolant injection in the corner vortex region, while the PSP measurements highlight the impact of swirled flow on the liner film protection separating the contribution of slot and effusion flows. Furthermore an additional analysis, exploiting experimental results in terms of heat transfer coefficient, has been performed to estimate the net heat flux reduction (NHFR) on the cooled test plate.

Experimental Investigation of the Flow Field and the Heat Transfer on a Scaled Cooled Combustor Liner With Realistic Swirling Flow Generated by a Lean-Burn Injection System

2014 ◽  
Author(s):  
Antonio Andreini ◽  
Gianluca Caciolli ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Film Cooling ◽  
Swirling Flow ◽  
Injection System ◽  
Lean Burn ◽  
Real Geometry ◽  
Slot Film Cooling ◽  
The Impact ◽  
Combustor Liner

Lean burn swirl stabilized combustors represent the key technology to reduce NOx emissions in modern aircraft engines. The high amount of air admitted through a lean-burn injection system is characterized by very complex flow structures such as recirculations, vortex breakdown and processing vortex core, that may deeply interact in the near wall region of the combustor liner. This interaction and its effects on the local cooling performance make the design of the cooling systems very challenging, accounting for the design and commission of new test rigs for detailed analysis. The main purpose of the present work is the characterization of the flow field and the wall heat transfer due to the interaction of a swirling flow coming out from real geometry injectors and a slot cooling system which generates film cooling in the first part of the combustor liner. The experimental setup consists of a non-reactive three sector planar rig in an open loop wind tunnel; the rig, developed within the EU project LEMCOTEC, includes three swirlers, whose scaled geometry reproduces the real geometry of an Avio Aero PERM (Partially Evaporated and Rapid Mixing) injector technology, and a simple cooling scheme made up of a slot injection, reproducing the exhaust dome cooling mass flow. Test were carried out imposing realistic combustor operating conditions, especially in terms of reduced mass flow rate and pressure drop across the swirlers. The flow field is investigated by means of PIV, while the measurement of the heat transfer coefficient is performed through Thermochromic Liquid Crystals steady state technique. PIV results show the behavior of flow field generated by the injectors, their mutual interaction and the impact of the swirled main flow on the stability of the slot film cooling. TLC measurements, reported in terms of detailed 2D heat transfer coefficient maps, highlight the impact of the swirled flow and slot film cooling on wall heat transfer.

Experimental Investigation of the Flow Field and the Heat Transfer on a Scaled Cooled Combustor Liner With Realistic Swirling Flow Generated by a Lean-Burn Injection System

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Antonio Andreini ◽  
Gianluca Caciolli ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Film Cooling ◽  
Swirling Flow ◽  
Injection System ◽  
Lean Burn ◽  
Real Geometry ◽  
Slot Film Cooling ◽  
The Impact ◽  
Combustor Liner

Lean-burn swirl stabilized combustors represent the key technology to reduce NOx emissions in modern aircraft engines. The high amount of air admitted through a lean-burn injection system is characterized by very complex flow structures, such as recirculations, vortex breakdown, and processing vortex core, which may deeply interact in the near wall region of the combustor liner. This interaction and its effects on the local cooling performance make the design of the cooling systems very challenging, accounting for the design and commission of new test rigs for detailed analysis. The main purpose of the present work is the characterization of the flow field and the wall heat transfer due to the interaction of a swirling flow coming out from real geometry injectors and a slot cooling system which generates film cooling in the first part of the combustor liner. The experimental setup consists of a nonreactive three sector planar rig in an open loop wind tunnel; the rig, developed within the EU project Low Emissions Core-Engine Technologies (LEMCOTEC), includes three swirlers, whose scaled geometry reproduces the real geometry of an Avio Aero partially evaporated and rapid mixing (PERM) injector technology, and a simple cooling scheme made up of a slot injection, reproducing the exhaust dome cooling mass flow. Test were carried out imposing realistic combustor operating conditions, especially in terms of reduced mass flow rate and pressure drop across the swirlers. The flow field is investigated by means of particle image velocimetry (PIV), while the measurement of the heat transfer coefficient is performed through thermochromic liquid crystals (TLCs) steady state technique. PIV results show the behavior of flow field generated by the injectors, their mutual interaction, and the impact of the swirled main flow on the stability of the slot film cooling. TLC measurements, reported in terms of detailed 2D heat transfer coefficient maps, highlight the impact of the swirled flow and slot film cooling on wall heat transfer.

Investigation on the Effect of a Realistic Flow Field on the Adiabatic Effectiveness of an Effusion-Cooled Combustor

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Luca Andrei ◽  
Antonio Andreini ◽  
Cosimo Bianchini ◽  
Bruno Facchini ◽  
Lorenzo Mazzei ◽  
...  
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Acoustic Properties ◽  
Injection System ◽  
Flat Plates ◽  
Cooling Performance ◽  
Hot Gas ◽  
Adiabatic Effectiveness ◽  
The Impact ◽  
Side Flow

Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned cross flow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by 22 rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code Ansys® CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular, with a strong reduction of slot effectiveness in case of 90 deg angle value.

Investigation on the Effect of a Realistic Flow Field on the Adiabatic Effectiveness of an Effusion-Cooled Combustor

2014 ◽  
Author(s):  
L. Andrei ◽  
A. Andreini ◽  
C. Bianchini ◽  
B. Facchini ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Acoustic Properties ◽  
Injection System ◽  
Flat Plates ◽  
Cooling Performance ◽  
Hot Gas ◽  
Adiabatic Effectiveness ◽  
The Impact ◽  
Side Flow

Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned crossflow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by twenty-two rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code ANSYS® CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular with a strong reduction of slot effectiveness in case of 90° angle value.

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Unsteady Interaction ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Development of Steam Chest With Valve for Steam Extraction in Cogeneration

2014 ◽  
Author(s):  
Zhenzhen Hao ◽  
Puning Jiang ◽  
Xingzhu Ye ◽  
Gang Chen ◽  
Yifeng Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Distribution ◽  
Fourier Transforms ◽  
Operating Conditions ◽  
Mode Analysis ◽  
Technical Solution ◽  
Test Model ◽  
Aerodynamic Forces ◽  
Valve Disc ◽  
The Impact

Cogeneration has been identified as a key technical solution to improve environment, by reducing the impact of global climate change and reducing local emissions, such as particulates, sulphur and nitrogen oxides. In cogeneration, a certain pressure of steam has to be extracted from steam turbine. A mechanical device shall be used to maintain the pressure of the extracted steam. In this paper a new steam chest with valve used for cogeneration which is installed in the steam flow is introduced. Different amount of steam extractions need different valve openings. In order to obtain these several valve openings in typical operating conditions, CFD-program is used to simulate the flow path in the steam chest. The pressure distribution on the surface of valve disc can be calculated through CFD method, and corresponding steady aerodynamic forces and torques can be calculated by integral. Pulsatile flow will change the forces and moments acting on the valve discs with time constantly. Frequency spectrograms of the aerodynamic forces are obtained by using the fast Fourier transforms and compared to the characteristic frequencies of the valve disc obtained by mode analysis. For the purpose of validating the accuracy of CFD model, a test with test model scale of 1:5 has been designed. In the test, the pressure distribution on the valve disc surface and the flow field in the steam chest are acquired respectively by the method PSP (Pressure-Sensitive Paint) and PIV (Particle Image Velocimetry). CFD calculations and experimental results have been compared and it is shown that CFD calculations using K-ε turbulence model has satisfactory precision to calculate the pressure distribution, flow field and the torques.

Effects of Ambient Air Humidity on Emissions and Efficiency of Large-Bore Lean-Burn Otto Gas Engines in Development and Application

2020 ◽  
Author(s):  
Tomas Bartkowski ◽  
Stefan Eicheldinger ◽  
Maximilian Prager ◽  
Georg Wachtmeister
Keyword(s):  
Air Conditioning ◽  
Test Bench ◽  
Water Injection ◽  
Measurement Data ◽  
Ambient Air ◽  
Injection System ◽  
Nox Emissions ◽  
Air Humidity ◽  
Ambient Conditions ◽  
Lean Burn

Abstract The use of large-bore Otto gas engines is currently spreading widely considering the growing share of Power-To-Gas (P2G) solutions using renewable energies. P2G with a Combined Heat and Power (CHP) plant offers a promising way of utilizing chemical energy storage to provide buffering for volatile energy sources such as wind and solar power all over the world. Therefore, ambient conditions like air temperature, humidity and pressure can differ greatly between the location and time of engine operation, influencing its performance. Especially lean-burn Otto processes are sensitive to changes in ambient conditions. Besides, targeted use of humidity variation (e.g. through water injection in the charge air or combustion chamber) can help to reduce NOx emissions at the cost of a slightly lower efficiency in gas engines, being an alternative to selective catalytic reduction (SCR) exhaust gas aftertreatment. The ambient air condition boundaries have to be considered already in the early stages of combustion development, as they can also have a significant effect on generated measurement data in combustion research. To investigate the behavior, a test bench with a natural gas (CNG) powered single-cylinder research engine (piston displacement 4.77 1) at the Institute of Internal Combustion Engines (LVK) of the Technical University of Munich (TUM) was equipped with a sophisticated charge air conditioning system. This includes an air compressor and refrigeration dryer, followed by temperature and pressure control, as well as a controlled injection system for saturated steam and homogenizing containers, enabling the test bench to precisely emulate a widespread area of charge air parameters in terms of pressure, temperature and humidity. With this setup, different engine tests were conducted, monitoring and evaluating the engine’s emission and efficiency behavior regarding charge air humidity. In a first approach, the engine was operated maintaining a steady air-fuel equivalence ratio λ, fuel energy input (Q̇fuel = const.) and center of combustion (MFB 50%) while the relative ambient humidity was varied in steps between 21% and 97% (at 22 °C and 1013.25 hPa). Results show a significant decrease in nitrogen oxides (NOx) emissions (−39.5%) and a slight decrease in indicated efficiency (−1,9%) while hydrocarbon (THC) emissions increased by around 60%. The generated data shows the high significance of considering charge air conditioning already in the development stage at the engine test bench. The comparability of measurement data depends greatly on ambient air humidity. In a second approach, the engine was operated at a constant load and constant NOx emissions, while again varying the charge air humidity. This situation rather reflects an actual engine behavior at a CHP plant, where today often NOx–driven engine control is used, maintaining constant NOx emissions. The decrease in indicated efficiency was comparable to the prior measurements, while the THC emissions showed only a mild increase (5%). From the generated data it is, for instance, possible to derive operational strategies to compensate for changes in ambient conditions while maintaining emission regulations as well as high-efficiency output. Furthermore, the results suggest possibilities, but also challenges of utilizing artificial humidification (e.g. through water injection) considering the effects on THC emissions and efficiency. A possible shift of the knocking limit to earlier centers of combustion with higher humidity is to be investigated. The main goal is the further decrease of NOx emissions, increase of efficiency, while still maintaining hydrocarbon emissions.

Interactions Between the Combustor Swirl and the High Pressure Stator of a Turbine

2012 ◽  
Author(s):  
Lucas Giller ◽  
Heinz-Peter Schiffer
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Field Measurements ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Film Cooling Holes ◽  
The Impact

The interaction between the strongly swirling combustor outflow and the high pressure turbine nozzle guide vanes were investigated at the cascade test rig at Technische Universität Darmstadt. The test section of the rig consists of six swirl generators and five cascade vanes. The three middle vanes are equipped with film cooling holes at the leading edges. The swirler nozzles are aligned with the center of the cascade passages. The operating settings are defined by the swirl number, the distance between the swirler nozzles and the vanes, the blowing ratio and the radial angle of the film cooling holes. Flow field measurements using PIV downstream of the swirlers and five hole probe measurements at the inlet and outlet plane of the cascade were accomplished. Measurements using the ammonia diazo technique to determine the adiabatic film cooling effectiveness on the surface of the center cascade vane were also carried out. It is shown that a swirling inflow leads to a strong alteration of the flow field and the losses in the passages in comparison to an axial inflow. Furthermore, the impact of the swirl on the formation of the cooling film and it’s adiabatic film cooling effectiveness is presented.

Unsteady Flow Field and Noise Generation in a Centrifugal Pump Impeller With a Vaneless Diffuser

2005 ◽  
Author(s):  
Giorgio Pavesi ◽  
Guido Ardizzon ◽  
Giovanna Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Wake Flow ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaneless Diffuser ◽  
Pump Impeller ◽  
Model Flow ◽  
Return Channel ◽  
The Impact

To improve understanding of the phenomena of stall in centrifugal pumps, extensive research was conducted to investigate the impact on flow field instabilities and the noise generated in a pump equipped with a diffuser. A pump fitted with a vaneless diffuser and a return channel was used as the test model. Flow velocity was measured at the pump and at diffuser inflow to establish a link between the flow field structure and acoustic radiation. Activity was based upon the cross spectral analysis of output signals from piezoelectric transducers placed flush with the wall at the inflow and outflow of the pump, and 3D fully-viscous unsteady computations. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Consequently, periodic fluctuations were seen at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content. With the exception of the total pressure in the far field, the pressure frequency scattering by the pump was found to be consistent when compared to the experimental and analytic results.

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