Design of a Secondary Concentrator for a Small Particle Heat Exchange Receiver

2015 ◽  
Author(s):  
Olivier Berchtold ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Small Particle ◽  
Average Power ◽  
Combined Cycle ◽  
Secondary Case ◽  
Gas Temperature ◽  
Acceptance Angle ◽  
Spectral Reflectivity ◽  
Yearly Average ◽  
Automated Simulation

The design of a secondary concentrator for the Small Particle Heat Exchange Receiver (SPHER) using a Monte Carlo Ray Tracing (MCRT) method is discussed in this paper. Applying basic MCRT rules, a modular solver logic for secondary concentrators is established. The logic is coded into FORTRAN subroutines to be compatible with MIRVAL, a ray trace code for heliostat fields created by Sandia National Laboratories. Based on a 3D Compound Parabolic Concentrator (3D-CPC) example the power of the simulation based on the Sandia heliostat field calculations is demonstrated. The results of the simulations are used to calculate the solar flux distributions in the ideal 3D CPC inlet and outlet planes as well as the incident ray distribution hitting the secondary concentrator. Code modifications to account for surface irregularities and spectral reflectivity are implemented in the appropriate FORTRAN subroutine. Using the automated simulation routines first the optimal receiver tilt angle and secondly the secondary concentrator acceptance angle are determined. These parameters combined with the fixed secondary concentrator outlet radius — which is determined by the SPHER window diameter — fully constrain the 3D CPC geometry. The flux maps generated using MATLAB post processing on the derived concentrator results clearly indicate the strengths and weaknesses of the specific concentrator and heliostat field combination. The influence of the secondary concentrator on the window incident flux distribution and window transmission, absorption and reflection properties is evaluated. Early findings using the code suggest higher yearly average power entering the receiver when compared to a non-secondary case. The reason for this effect is found in increased heliostat efficiency towards the edges of the heliostat field. At the same time the peak power hitting the window is found to increase very slightly only. This means the maximum window design specifications do not need to be adjusted dramatically to be able to accommodate the average power increase. First indications using the MCRT output in preliminary receiver simulations suggest increased receiver efficiency and a boost in receiver outlet gas temperature. The combined effect of these improvements is expected to raise overall power generation efficiency by improving the gas- / steam turbine combined cycle efficiency.

Analysis of Off-Design Behavior of a Solar-Fossil Hybrid Combined Cycle Plant Using a Small Particle Heat Exchange Receiver (SPHER) With a Variable Guide Vane Gas Turbine

2016 ◽  
Author(s):  
Matthew Miguel Virgen ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Small Particle ◽  
Guide Vane ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Inlet Temperature

Two significant goals in solar plant operation are lower cost and higher efficiencies. This is both for general competitiveness of solar technology in the energy industry, and also to meet the US DOE Sunshot Initiative Concentrating Solar Power (CSP) cost goals [1]. We present here an investigation on the effects of adding a bottoming steam power cycle to a solar-fossil hybrid CSP plant based on a Small Particle Heat Exchange Receiver (SPHER) driving a gas turbine as the primary cycle. Due to the high operating temperature of the SPHER being considered (over 1000 Celsius), the exhaust air from the primary Brayton cycle still contains a tremendous amount of exergy. This exergy of the gas flow can be captured in a heat recovery steam generator (HRSG), to generate superheated steam and run a bottoming Rankine cycle, in a combined cycle gas turbine (CCGT) system. A wide range of cases were run to explore options for maximizing both power and efficiency from the proposed CSP CCGT plant. Due to the generalized nature of the bottoming cycle modeling, and the varying nature of solar power, special consideration had to be given to the behavior of the heat exchanger and Rankine cycle in off-design scenarios. Variable guide vanes (VGVs), which can control the mass flow rate through the gas turbine system, have been found to be an effective tool in providing operational flexibility to address the variable nature of solar input. The effect VGVs and the operating range associated with them are presented. Strategies for meeting a minimum solar share are also explored. Trends with respect to the change in variable guide vane angle are discussed, as well as the response of the HRSG and bottoming Rankine cycle in response to changes in the gas mass flow rate and temperature. System efficiencies in the range of 50% were found to result from this plant configuration. However, a combustor inlet temperature (CIT) limit lower than a turbine inlet temperature (TIT) limit leads two distinct Modes of operation, with a sharp drop in both plant efficiency and power occurring when the air flow through the receiver exceeded the (CIT) limit, and as a result would have to bypass the combustor entirely and enter the turbine at a significantly lower temperature than nominal. Until that limit is completely eliminated through material or design improvements, this drawback can be addressed through strategic use of the variable guide vanes. Optimal operational strategy is ultimately decided by economics, plant objectives, or other market incentives.

Carbon Particle Generation and Lab-Scale Small Particle Heat Exchange Receiver Experimentation and Modeling

2014 ◽  
Author(s):  
Lee Frederickson ◽  
Mario Leoni ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Computer Model ◽  
Small Particle ◽  
Carbon Nanoparticles ◽  
Carbon Particle ◽  
Rankine Cycle ◽  
Gas Temperature ◽  
Solar Simulator ◽  
Ansys Fluent ◽  
Carbon Particles

Central receivers being installed in recent commercial CSP plants are liquid-cooled and power a steam turbine in a Rankine cycle. San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory has built and is testing a lab-scale Small Particle Heat Exchange Receiver (SPHER). The SPHER is an air-cooled central receiver that is designed to power a gas turbine in a Brayton cycle. The SPHER uses carbon nanoparticles suspended in air as an absorption medium. The carbon nanoparticles should oxidize by the outlet of the SPHER, which is currently designed to operate at 5 bar absolute with an exit gas temperature above 1000°C. Carbon particles are generated from hydrocarbon pyrolysis in the carbon particle generator (CPG). The particles are mixed at the outlet of the CPG with dilution air and the mixture is sent to the SPHER. As the gas-particle mixture flows through the SPHER, radiation entering the SPHER from the solar simulator is absorbed by the carbon particles, which transfer heat to the gas suspension and eventually oxidize, resulting in a clear gas stream at the outlet. Particle mass loading is measured using a laser opacity measurement combined with a Mie calculation, while particle size distribution is determined by scanning electron microscopy and a diesel particulate scatterometer prior to entering the SPHER. In predicting the performance of the system, computer models have been set up in CHEMKIN-PRO for the CPG and in ANSYS Fluent for the SPHER, which is coupled with VeGaS ray trace code for the solar simulator. Initial experimentation has resulted in temperatures above 850°C with around a 50K temperature difference when particles are present in the air flow. The CPG computer model has been used to estimate performance trends while the SPHER computer model has been run for conditions to match those expected from future experimentation.

scholarly journals Fabrication and Mechanical Properties of Cr2AlC MAX Phase Coatings on TiBw/Ti6Al4V Composite Prepared by HiPIMS

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 826
Author(s):  
Muhammad Waqas Qureshi ◽  
Xinxin Ma ◽  
Guangze Tang ◽  
Bin Miao ◽  
Junbo Niu
Keyword(s):  
Magnetron Sputtering ◽  
Deposition Rate ◽  
Pulse Width ◽  
Average Power ◽  
Max Phase ◽  
Ex Situ ◽  
Gas Temperature ◽  
Degree Of Ionization ◽  
Force Microscopy ◽  
High Degree

The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic.

scholarly journals Experimental investigations of the processes in gas generator of hydrogen-air energy storage

2021 ◽  
Vol 2039 (1) ◽  
pp. 012007
Author(s):  
N I Chukhin ◽  
A I Schastlivtsev
Keyword(s):  
Energy Storage ◽  
Turbine Unit ◽  
Cooling System ◽  
Average Power ◽  
Experimental Investigations ◽  
Gas Temperature ◽  
Gas Generator ◽  
Gas Turbine Unit ◽  
Accumulation System ◽  
Generator Unit

Abstract This paper describes the results of experimental investigation of the sample of the hydrogen-air gas generator unit with the expected average power of 65 kW. In total 5 test runs were made. Two tests showed that the mass flow and outlet gas temperature was in an agreement with the designed parameters. Additional attention should be paid to the cooling system design for the combustion chamber. In future such a gas generator in couple with the suitable gas turbine unit could be a part of the renewable energy accumulation system e.g. of hydrogen-air energy storage.

Effect of Coolant Injection Angle on Nozzle Endwall Film Cooling: Experimental and Numerical Analysis in Linear Cascade

2018 ◽  
Author(s):  
Lamyaa El-Gabry ◽  
Hongzhou Xu ◽  
Kevin Liu ◽  
James Chang ◽  
Michael Fox
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Surface Film ◽  
Combined Cycle ◽  
Gas Temperature ◽  
Injection Angle ◽  
Linear Cascade ◽  
Cfd Models ◽  
Coolant Injection ◽  
Exhaust Heat

Gas turbine components can withstand gas temperatures exceeding the melting point of the alloys they’re made of due to increasingly effective cooling methods. Increasing the operating temperature of a gas turbine is key to improving its power density and exhaust heat for steam or combined-cycle efficiency. In the turbine, the component that experiences the highest gas temperature is the vane directly downstream of the combustor; the most complex flow field in a vane occurs near the endwall. In this study, an experimental investigation is carried out to determine the effect of coolant injection angle and mass flow ratio on film effectiveness on the endwall using the pressure sensitive paint technique for various configurations of jump cooling hole configurations. Two rows of angled holes are upstream of an uncooled vane in a three-vane linear cascade. Injection angle including compound angle is varied from 20 to 60 and coolant to mainstream massflux ratio is varied from 0.5% to 3%. Contours of endwall surface film effectiveness are presented along with span-averaged film effectiveness. CFD models of the cascade are developed using a commercial solver to predict film effectiveness for some of the test conditions and comparisons are made between the experimental and numerical results. The CFD models provide further insight into the flow field and explain trends observed in the experiment by understanding the interaction of jump coolant flow with the 3D endwall mainstream flows.

Application of Ultra-Low NOx Combustor to the MHPS Existing Gas Turbine

2021 ◽  
Author(s):  
Takashi Nishiumi ◽  
Hirofumi Ohara ◽  
Kotaro Miyauchi ◽  
Sosuke Nakamura ◽  
Toshishige Ai ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Operational Experience ◽  
Emission Rates ◽  
Gas Temperature ◽  
Design Development ◽  
And Control

Abstract In recent years, MHPS achieved a NET M501J gas turbine combined cycle (GTCC) efficiency in excess of 62% operating at 1,600°C, while maintaining NOx under 25ppm. Taking advantage of our gas turbine combustion design, development and operational experience, retrofits of earlier generation gas turbines have been successfully applied and will be described in this paper. One example of the latest J-Series technologies, a conventional pilot nozzle was changed to a premix type pilot nozzle for low emission. The technology was retrofitted to the existing F-Series gas turbines, which resulted in emission rates of lower than 9ppm NOx(15%O2) while maintaining the same Turbine Inlet Temperature (TIT: Average Gas Temperature at the exit of the transition piece). After performing retrofitting design, high pressure rig tests, the field test prior to commercial operation was conducted on January 2019. This paper describes the Ultra-Low NOx combustor design features, retrofit design, high pressure rig test and verification test results of the upgraded M501F gas turbine. In addition, it describes another upgrade of turbine to improve efficiency and of combustion control system to achieve low emissions. Furthermore it describes the trouble-free upgrade of seven (7) units, which was completed by utilizing MHPS integration capabilities, including handling all the design, construction and service work of the main equipment, plant and control systems.

Gas Turbine Combined Cycle Optimized for Postcombustion Carbon Capture

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
S. Can Gülen ◽  
Chris Hall
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Co2 Capture ◽  
Carbon Capture ◽  
Heat Recovery ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Gas Temperature ◽  
Design Challenges ◽  
Stack Gas

This paper describes a gas turbine combined cycle (GTCC) power plant system, which addresses the three key design challenges of postcombustion CO2 capture from the stack gas of a GTCC power plant using aqueous amine-based scrubbing method by offering the following: (i) low heat recovery steam generator (HRSG) stack gas temperature, (ii) increased HRSG stack gas CO2 content, and (iii) decreased HRSG stack gas O2 content. This is achieved by combining two bottoming cycle modifications in an inventive manner, i.e., (i) high supplementary (duct) firing in the HRSG and (ii) recirculation of the HRSG stack gas. It is shown that, compared to an existing natural gas-fired GTCC power plant with postcombustion capture, it is possible to reduce the CO2 capture penalty—power diverted away from generation—by almost 65% and the overall capital cost ($/kW) by about 35%.

Oxidation Rate Analysis of Carbon Nanoparticles for a Small Particle Heat Exchange Receiver

2014 ◽  
Author(s):  
Mario Leoni ◽  
Lee Frederickson ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Small Particle ◽  
Oxidation Rate ◽  
Flow Behavior ◽  
Average Diameter ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Extinction Cross Section ◽  
Carbon Particles ◽  
Rate Analysis

A new experimental set-up has been introduced at San Diego State University’s Combustion and Solar Energy Lab to study the thermal oxidation characteristics of in-situ generated carbon particles in air at high pressure. The study is part of a project developing a Small Particle Heat Exchange Receiver (SPHER) utilizing concentrated solar power to run a Brayton cycle. The oxidation data obtained will further be used in different existing and planned computer models in order to accurately predict reactor temperatures and flow behavior in the SPHER. The carbon black particles were produced by thermal decomposition of natural gas at 1250 °C and a pressure of 5.65 bar (82 psi). Particles were analyzed using a Diesel Particle Scatterometer (DPS) and scanning electron microscopy (SEM) and found to have a 310 nm average diameter. The size distribution and the complex index of refraction were measured and the data were used to calculate the specific extinction cross section γ of the spherical particles. The oxidation rate was determined using 2 extinction tubes and a tube furnace and the values were compared to literature. The activation energy of the carbon particles was determined to be 295.02 kJ/mole which is higher than in comparable studies. However, the oxidation of carbon particles bigger than 100 nm is hardly studied and almost no previous data is available at these conditions.

Carbon Particle Generation and Preliminary Small Particle Heat Exchange Receiver Lab Scale Testing

2013 ◽  
Author(s):  
Lee Frederickson ◽  
Kyle Kitzmiller ◽  
Fletcher Miller
Keyword(s):  
High Temperature ◽  
Heat Exchange ◽  
Natural Gas ◽  
Small Particle ◽  
Carbon Particle ◽  
Solar Flux ◽  
Gas Mixture ◽  
Solar Simulator ◽  
Spherical Cap ◽  
Carbon Particles

High temperature central receivers are on the forefront of concentrating solar power research. Current receivers use liquid cooling and power steam cycles, but new receivers are being designed to power gas turbine engines within a power cycle while operating at a high efficiency. To address this, a lab-scale Small Particle Heat Exchange Receiver (SPHER), a high temperature solar receiver, was built and is currently undergoing testing at the San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory. The final goal is to design, build, and test a full-scale SPHER that can absorb 5 MWth and eventually be used within a Brayton cycle. The SPHER utilizes air mixed with carbon particles generated in the Carbon Particle Generator (CPG) as an absorption medium for the concentrated solar flux. Natural gas and nitrogen are sent to the CPG where the natural gas undergoes pyrolysis to carbon particles and nitrogen is used as the carrier gas. The resulting particle-gas mixture flows out of the vessel and is met with dilution air, which flows to the SPHER. The lab-scale SPHER is an insulated steel vessel with a spherical cap quartz window. For simulating on-sun testing, a solar flux is produced by a solar simulator, which consists of a 15kWe xenon arc lamp, situated vertically, and an ellipsoidal reflector to obtain a focus at the plane of the receiver window. The solar simulator has been shown to produce an output of about 3.25 kWth within a 10 cm diameter aperture. Inside of the SPHER, the carbon particles in the inlet particle-gas mixture absorb radiation from the solar flux. The carbon particles heat the air and eventually oxidize to carbon dioxide, resulting in a clear outlet fluid stream. Since testing was initiated, there have been several changes to the system as we have learned more about the operation. A new extinction tube was designed and built to obtain more accurate mass loading data. Piping and insulation for the CPG and SPHER were improved based on observations between testing periods. The window flange and seal have been redesigned to incorporate window film cooling. These improvements have been made in order to achieve the lab scale SPHER design objective gas outlet flow of 650°C at 5 bar.

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