A Thermal Mixing Scheme for Portable Gas Turbines

2010 ◽  
Author(s):  
S. Tanaka ◽  
Z. Spakovszky
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Small Scale ◽  
Exhaust Gas ◽  
Mixing Length ◽  
Flow Ratio ◽  
Flow Mixing ◽  
Mass Flow Ratio

To meet the increasing demand for advanced portable power units, for example for use in personal electronics and robotics, a number of studies have recently focused on small gas turbine units in the 500 W to 1 kW range. The majority of the work to date is concerned with the design of efficient high-speed rotating machinery and electric components. An important aspect, especially critical for portable operation, is the cooling of the gas turbine and the exhaust gas. This is the focus of the present paper. The compact and small-scale architecture of such gas turbine engines poses major challenges in the thermal management as the required cooling mass flow for portable operation is relatively large and the flow mixing length is short and constrained by package size considerations. Previously, a mixer/ejector based cooling scheme was proposed and vortex generator rings and multi-walled ejector configurations were experimentally investigated with the goal to enhance the mixing of the exhaust gas with cooling flow [1]. Although the augmentations achieved a satisfactory cooling mass flow ratio of 16.8:1, hot spots still existed at the exit of the relatively long mixer duct due to the high area-ratio of the ejector configuration. To overcome this mixing challenge, an alternative cooling scheme was conceived. In this scheme, the hot exhaust gas flow is forced radially outward through a perforated cylindrical liner into the cooling air flow surrounding the exhaust duct. The concept resembles that of an inverted dilution liner where the hot exhaust gas is injected into the much larger cooling mass flow. The hypothesis is that the array of streamwise vortices formed by the hot jets reduces the mixing length and significantly mitigates the temperature non-uniformity. The design space was first explored using a control volume (CV) analysis and the performance of the proposed device and the detailed flow features were investigated using three-dimensional Computational Fluid Dynamics (CFD) simulations. The computations demonstrate enhanced mixing which reduces the turbine exhaust gas temperature of 630°C to a temperature distribution below 75°C at the mixer exit, comparable to the temperature levels and non-uniformity of a commercial hand dryer. The cooling mass flow ratio and required cooling fan power were 15.4 and 1.9% of engine power output respectively. Flow mixing guidelines were established together with a concept mixer configuration, generally applicable to small scale gas turbine devices.

Experimental Study on Comparison of Cooling Effectiveness Between Steam and Air for a Gas Turbine Nozzle Guide Vane

2012 ◽  
Author(s):  
Wei Wang ◽  
Jianmin Gao ◽  
Xiaojun Shi ◽  
Liang Xu ◽  
Zhao Wang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Guide Vane ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Cooling Method ◽  
Nozzle Guide ◽  
Mass Flow Ratio

An experimental investigation of the cooling performance for a gas turbine vane with internal passages is conducted on a linear turbine cascade consisting of three nozzle guide vanes with a chord length of 126mm and a blade height of 83 mm. Measurements of temperature and static pressure distribution are implemented on the center guide vane, which is internally cooled by air or steam flowing radially through five smooth channels. The main objective of this investigation is to receive more information on the temperature of vane surface, and to compare the cooling effectiveness between air and superheated steam. The experiments are performed for a variety of exit Mach numbers, exit Reynolds number, coolant-to-mainstream mass flow ratio, and coolant-to-mainstream temperatures ratio. The experimental results show, that at coolant-to-mainstream mass flow ratio 0.08 and coolant-to-mainstream temperatures ratio 0.61, the average surface temperature of steam cooled vane decreases about 25% and the corresponding average cooling effectiveness is 52%, while for the air cooled vane, it is 18% and 42%, respectively. Therefore the coolant steam has much better cooling performance than air. Furthermore, the cooling effectiveness at the middle chord region of vane is much higher than that at the leading and trailing region, as is expected. Consequently, this leads to great temperature gradient and thermal stresses at the leading and trailing region, where the internal convective cooling method has insufficient cooling ability. Therefore, besides convective cooling method, more complicated cooling configuration may be necessitated.

Investigation of the Effect of the Top and the Bottom Temperatures on the Performance of Humidification Dehumidification Desalination Systems

2016 ◽  
Author(s):  
Naef Qasem ◽  
Binash Imteyaz ◽  
M. A. Antar
Keyword(s):  
Mass Flow ◽  
Water Cycle ◽  
Open Water ◽  
Water Desalination ◽  
Small Scale ◽  
Main Concern ◽  
Flow Ratio ◽  
Water Heater ◽  
Desalinated Water ◽  
Mass Flow Ratio

Humidification dehumidification process is an attractive small scale water desalination technique in which desalinated water is produced by mimicking the nature’s water cycle. Various modifications to the basic HDH system can be vital in improving the productivity and reducing the production cost of the fresh water. In this study, a closed-air-open-water water-heated (CAOW-WH) cycle and a closed-air-open-water air-heated (CAOW-AH) cycle are modeled and optimized. Effects of mass flow ratio, humidifier and dehumidifier effectiveness, relative humidity, top and bottom temperatures (main concern of study) on the gain output ratio (GOR), the recovery ratio (RR), entropy generation in the system have been analyzed and presented. It has been observed that an optimal mass flow ratio exists for both the cycles, which maximizes the GOR of the system. Moreover, effectiveness of the humidifier and the dehumidifier is an important parameter, which determines the productivity of the systems. Furthermore, a higher GOR can be obtained at low Tmin and high Tmax and at high Tmin and low Tmax for systems heated by a water heater, whereas the GOR of the air heated HDH system increases with increasing both the Tmin and the Tmax for values of humidifier and dehumidifier effectiveness of 0.8. This study provide extended design charts for building an optimum HDH system to produce a pre-determined rate of desalinated water.

Design and Testing of a Micromix Combustor With Recuperative Wall Cooling for a Hydrogen Fuelled μ-Scale Gas Turbine

2010 ◽  
Author(s):  
A. E. Robinson ◽  
H. H.-W. Funke ◽  
P. Hendrick ◽  
R. Wagemakers
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
High Energy ◽  
High Energy Density ◽  
Energy Output ◽  
Experimental Investigations ◽  
Small Scale ◽  
Micro Scale

For more than a decade up to now there is an ongoing interest in small gas turbines downsized to micro-scale. With their high energy density they offer a great potential as a substitute for today’s unwieldy accumulators, found in a variety of applications like laptops, small tools etc. But micro-scale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles (UAVs) or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a μ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype’s design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterisation concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore the data show a full compliance with the expected operating requirements of the designated μ-scale gas turbine.

scholarly journals Visualization of Dome Region Mixing in a Quartz Combustor

1991 ◽  
Author(s):  
R. A. Brady ◽  
G. S. Samuelsen
Keyword(s):  
Flow Visualization ◽  
Gas Turbine ◽  
Mass Flow ◽  
Atmospheric Pressure ◽  
Operating Conditions ◽  
Flow Ratio ◽  
Preliminary Step ◽  
Swirl Angle ◽  
Air Mixing ◽  
Mass Flow Ratio

To improve the performance of gas turbine combustors (i.e. stability and emissions), the process of fuel-air mixing, within the dome region, must be better understood and enhanced. This paper takes a preliminary step by evaluating the influences of nozzle air/fuel ratio, swirl angle, and dome geometry on fuel-air mixing. A model combustor, fabricated from quartz and designed to utilize flow visualization as the primary diagnostic, was operated at atmospheric pressure with JP-4 injected through a twin-fluid (air-assist) atomizer. Photographs of the dome region were acquired for a variation in (1) nozzle air/fuel mass flow ratio from 2.0 to 4.0, (2) swirl angle from 45° to 60°, and (3) the shape of the dome from a dump to a 45° conical expansion configuration. The results show trends of improved mixing for higher nozzle air/fuel ratios as manifested by the improved homogeneity and reduced intermittency of the reaction structure. The effects of dome geometry and swirl strength also affect mixing, with the degree and direction of effect depending on the atomizer operating conditions.

scholarly journals Micro Gas Turbine for Combined Heat and Power in Distributed Generation

1998 ◽  
Author(s):  
Johanna Carnö ◽  
Adrin Cavani ◽  
Leif Liinanki
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Combined Heat And Power ◽  
Small Scale ◽  
Heat Output ◽  
Micro Gas Turbine ◽  
Fuel Flexibility ◽  
Evaluation Phase ◽  
Demonstration Plant

Micro gas turbine units are becoming popular for on-site combined heat and power production (CHP). CHP units based on gas turbines have several advantages; low emissions, compactness, low maintenance costs and fuel flexibility. The successful development of a small high-speed turbogenerator gives major opportunities to meet the customers’ demands in a deregulated and competitive market. Vattenfall, together with Volvo Aero Turbines and ABB, has actively participated in development of a future concept of micro gas turbines. The first demonstration plant in Northern Europe for small scale heat and power co-generation, a 40 kWe turbogenerator was installed by Vattenfall at Pappersgruppen in Gothenburg, Sweden. A first evaluation phase of the demonstration plant has been performed. The electricity and heat output showed to be 38 kWe and 70 kW respectively at full load. The net plant efficiency was 28.2% and the overall efficiency was 80%, based on the lower heating value. The emissions from the unit were very low due to low emission combustion chamber. The evaluation period will continue during 97/98. The influence of outdoor temperature, degree of loading, as well as the required maintenance and manned operation will be investigated.

Design and Testing of a Micromix Combustor With Recuperative Wall Cooling for a Hydrogen Fueled μ-Scale Gas Turbine

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
A. E. Robinson ◽  
H. H.-W. Funke ◽  
P. Hendrick ◽  
R. Wagemakers
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
High Energy ◽  
Gas Analysis ◽  
High Energy Density ◽  
Energy Output ◽  
Experimental Investigations ◽  
Small Scale

For more than 1 decade up to now, there is an ongoing interest in small gas turbines downsized to microscale. With their high energy density, they offer a great potential as a substitute for today’s unwieldy accumulators found in a variety of applications such as laptops, small tools, etc. But microscale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so-called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a μ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype’s design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterization concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore, the data show full compliance with the expected operating requirements of the designated μ-scale gas turbine.

scholarly journals Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Patrick Nau ◽  
Zhiyao Yin ◽  
Oliver Lammel ◽  
Wolfgang Meier
Keyword(s):  
Gas Turbine ◽  
Wall Temperature ◽  
Gas Turbines ◽  
High Speed ◽  
Bluff Body ◽  
Temperature Measurements ◽  
Transient Temperature ◽  
High Time Resolution ◽  
Ceramic Surface ◽  
Precessing Vortex Core

Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution. To study the feasibility of this technique for full-scale gas turbine applications, a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations. An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.

Boundary Layer Flashback Limits of Hydrogen-Methane-Air Flames in a Generic Swirl Burner at Gas Turbine Relevant Conditions

2020 ◽  
Author(s):  
Dominik Ebi ◽  
Peter Jansohn
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Wall Temperature ◽  
Gas Turbines ◽  
High Speed ◽  
Cooling System ◽  
Atmospheric Conditions ◽  
Preheat Temperature ◽  
Swirl Burner ◽  
Wide Range

Abstract Operating stationary gas turbines on hydrogen-rich fuels offers a pathway to significantly reduce greenhouse gas emissions in the power generation sector. A key challenge in the design of lean-premixed burners, which are flexible in terms of the amount of hydrogen in the fuel across a wide range and still adhere to the required emissions levels, is to prevent flame flashback. However, systematic investigations on flashback at gas turbine relevant conditions to support combustor development are sparse. The current work addresses the need for an improved understanding with an experimental study on boundary layer flashback in a generic swirl burner up to 7.5 bar and 300° C preheat temperature. Methane-hydrogen-air flames with 50 to 85% hydrogen by volume were investigated. High-speed imaging was applied to reveal the flame propagation pathway during flashback events. Flashback limits are reported in terms of the equivalence ratio for a given pressure, preheat temperature, bulk flow velocity and hydrogen content. The wall temperature of the center body along which the flame propagated during flashback events has been controlled by an oil heating/cooling system. This way, the effect any of the control parameters, e.g. pressure, had on the flashback limit was de-coupled from the otherwise inherently associated change in heat load on the wall and thus change in wall temperature. The results show that the preheat temperature has a weaker effect on the flashback propensity than expected. Increasing the pressure from atmospheric conditions to 2.5 bar strongly increases the flashback risk, but hardly affects the flashback limit beyond 2.5 bar.

Three Spool High Efficiency Small Scale Gas Turbine Concept

2017 ◽  
Author(s):  
Matti Malkamäki ◽  
Ahti Jaatinen-Värri ◽  
Antti Uusitalo ◽  
Aki Grönman ◽  
Juha Honkatukia ◽  
...  
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Small Scale ◽  
Inlet Temperature ◽  
Substantial Impact ◽  
Electrical Efficiency ◽  
Partial Load ◽  
Reciprocating Engines

Decentralized electricity and heat production is a rising trend in small-scale industry. There is a tendency towards more distributed power generation. The decentralized power generation is also pushed forward by the policymakers. Reciprocating engines and gas turbines have an essential role in the global decentralized energy markets and improvements in their electrical efficiency have a substantial impact from the environmental and economic viewpoints. This paper introduces an intercooled and recuperated three stage, three-shaft gas turbine concept in 850 kW electric output range. The gas turbine is optimized for a realistic combination of the turbomachinery efficiencies, the turbine inlet temperature, the compressor specific speeds, the recuperation rate and the pressure ratio. The new gas turbine design is a natural development of the earlier two-spool gas turbine construction and it competes with the efficiencies achieved both with similar size reciprocating engines and large industrial gas turbines used in heat and power generation all over the world and manufactured in large production series. This paper presents a small-scale gas turbine process, which has a simulated electrical efficiency of 48% as well as thermal efficiency of 51% and can compete with reciprocating engines in terms of electrical efficiency at nominal and partial load conditions.

The Effect of Transient Fuel Staging on Self-Excited Instabilities in a Multi-Nozzle Model Gas Turbine Combustor

2017 ◽  
Author(s):  
Wyatt Culler ◽  
Janith Samarasinghe ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca ◽  
Jacqueline O’Connor
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Equivalence Ratio ◽  
Growth Time ◽  
Stable Operation ◽  
Time Constants ◽  
Decay Times ◽  
Fuel Staging ◽  
Passive Techniques

Combustion instability in gas turbines can be mitigated using active techniques or passive techniques, but passive techniques are almost exclusively used in industrial settings. While fuel staging, a common passive technique, is effective in reducing the amplitude of self-excited instabilities in gas turbine combustors at steady-state conditions, the effect of transients in fuel staging on self-excited instabilities is not well understood. This paper examines the effect of fuel staging transients on a laboratory-scale five-nozzle can combustor undergoing self-excited instabilities. The five nozzles are arranged in a four-around-one configuration and fuel staging is accomplished by increasing the center nozzle equivalence ratio. When the global equivalence ratio is φ = 0.70 and all nozzles are fueled equally, the combustor undergoes self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased to φ = 0.80 or φ = 0.85. Two transient staging schedules are used, resulting in transitions from unstable to stable operation, and vice-versa. It is found that the characteristic instability decay times are dependent on the amount of fuel staging in the center nozzle. It is also found that the decay time constants differ from the growth time constants, indicating hysteresis in stability transition points. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the instability onset process is different from the instability decay process.

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