DOCSLIB.ORG

Pumps, Fans and Turbines

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pumps, Fans and Turbines Turbomachinery { pumps, fans and turbines Fluid machinery Eciency Characteristic curves Turbomachinery { pumps, fans and turbines Pump/pipe systems SOE2156: Fluids Lecture 4 Pump/pipe systems Pump/pipe systems Turbomachinery { pumps, fans and turbines Fluid machinery Fluid machinery Fluid machine { a device exchanging energy (work) between a Eciency uid and a mechanical system. Characteristic curves In particular : a turbomachine is a device using a rotating Pump/pipe mechanical system. systems Pump/pipe The ow of energy can be in either direction : systems 1 Turbine ! the ow does work on the mechanical system Pump/pipe systems (i.e. energy is transmitted from the uid to the mechanical system) 2 Pumps, fans, compressors, blowers ! the mechanical system does work on the ow (i.e. energy is transmitted from the rotor to the uid) Contact between the mechanical and uid parts is via an impeller Turbomachinery { pumps, fans and turbines Types of turbine Fluid machinery Impulse turbine { e.g. Pelton wheel. Free jet of water impinges Eciency on revolving impeller (runner) and is de ected. Characteristic Change of momentum of water change of curves momentum (torque) for impeller. Pump/pipe systems Total available head converted into kinetic energy Pump/pipe systems head ! work done on impeller. Pump/pipe Reaction turbine { e.g. centrifugal, Kaplan turbine. Turbine systems completely enclosed in water, which can be pressurised. Shape of blades forces change in momentum of water { torque on blades { power. Reaction turbine uses available pressure head directly, without conversion to k.e. Turbomachinery { pumps, fans and turbines Fluid machinery Eciency Contact between the mechanical and uid parts is via an Characteristic curves impeller Pump/pipe 1 Axial ow : uid approaches and leaves impeller along the systems axis of rotation Pump/pipe systems 2 Centrifugal ow : uid approaches axially, leaves radially Pump/pipe systems (in plane of impeller) 3 Mixed ow : part axial, part radial Turbomachinery { pumps, fans and turbines Centrifugal pumps/turbines Fluid machinery Eciency Characteristic curves Pump/pipe systems Pump/pipe systems Pump/pipe systems Turbomachinery { pumps, fans and turbines Kaplan turbine (axial ow) Fluid machinery Eciency Characteristic curves Pump/pipe systems Pump/pipe systems Pump/pipe systems Turbomachinery { pumps, fans and turbines Eciency Fluid machinery Eciency De ne the eciency of a turbine Characteristic curves Actual power generated by turbine Pump/pipe = systems Head available to turbine Pump/pipe systems Power generated by turbine will be reduced by a number of Pump/pipe systems losses : Mechanical losses { bearing friction etc. Hydraulic losses, including : Impeller power loss { ineciencies in the impeller design Leakage power loss { some ow evades the impeller Casing power loss { friction with casing Turbomachinery { pumps, fans and turbines For a turbine, supplied with water ow rate Q at head H, the Fluid machinery power generated will be Eciency Characteristic P = gQH curves Pump/pipe systems Reaction turbines will also operate as pumps { mechanical work Pump/pipe used to increase energy of uid. systems Pump/pipe For a pump, pumping ow rate Q against head H, the power systems necessary will be gQH P = Eciencies, power, head etc. will depend on design of system and operating conditions. Turbomachinery { pumps, fans and turbines Characteristic curves Fluid machinery Eciency For a pump, we are interested in how the developed head H, Characteristic curves power P and eciency vary as ow rate Q changes. Plot Pump/pipe these against Q : systems Pump/pipe systems Pump/pipe systems Head H Power P Efficiency Flow rate Q Turbomachinery { pumps, fans and turbines Fluid machinery Eciency For a turbine, plot power P, ow rate Q, eciency against Characteristic turbine speed N. curves Pump/pipe systems Pumps, turbines designed to work at a particular point on the Pump/pipe characteristic curve { hopefully at the most ecient point. systems Usually quote the performance at this design point. Pump/pipe systems What determines the conditions that the pump operates under? How do we couple the pump to the surrounding pipes? 3 Pump characteristic inverted 4 System will function where head and ow both match Turbomachinery { pumps, fans and turbines Pump/pipe systems Fluid machinery Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve Q 4 System will function where head and ow both match Turbomachinery { pumps, fans and turbines Pump/pipe systems Fluid machinery Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Pump Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve 3 Pump characteristic inverted Q Turbomachinery { pumps, fans and turbines Pump/pipe systems Fluid machinery Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Pump Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve 3 Pump characteristic inverted Q 4 System will function where head and ow both match.
Load more

Recommended publications
  • Combustion Turbines
    Section 3. Technology Characterization – Combustion Turbines U.S. Environmental Protection Agency Combined Heat and Power Partnership March 2015 Disclaimer The information contained in this document is for information purposes only and is gathered from published industry sources. Information about costs, maintenance, operations, or any other performance criteria is by no means representative of EPA, ORNL, or ICF policies, definitions, or determinations for regulatory or compliance purposes. The September 2017 revision incorporated a new section on packaged CHP systems (Section 7). This Guide was prepared by Ken Darrow, Rick Tidball, James Wang and Anne Hampson at ICF International, with funding from the U.S. Environmental Protection Agency and the U.S. Department of Energy. Catalog of CHP Technologies ii Disclaimer Section 3. Technology Characterization – Combustion Turbines 3.1 Introduction Gas turbines have been in use for stationary electric power generation since the late 1930s. Turbines went on to revolutionize airplane propulsion in the 1940s, and since the 1990s through today, they have been a popular choice for new power generation plants in the United States. Gas turbines are available in sizes ranging from 500 kilowatts (kW) to more than 300 megawatts (MW) for both power-only generation and combined heat and power (CHP) systems. The most efficient commercial technology for utility-scale power plants is the gas turbine-steam turbine combined-cycle plant that has efficiencies of more than 60 percent (measured at lower heating value [LHV]35). Simple- cycle gas turbines used in power plants are available with efficiencies of over 40 percent (LHV). Gas turbines have long been used by utilities for peaking capacity.
    [Show full text]
  • Engineering the Future – Since 1758
    MAN Energy Solutions MAN Energy Solutions Product range und product centres 3 Steinbrinkstr. 1 2 46145 Oberhausen, Germany Turbomachinery P + 49 208 692-01 F + 49 208 692-021 [email protected] www.man-es.com Factories Engineering turbomachinery Turbo- the future – Bangalore, India MAN Turbomachinery India Private Limited since 175 8 Plot No. 113 | Jigani link Road KIADB Industrial Area | Jigani | 560105 Bangalore, India Phone +91 80 6655 2200 | Fax +91 80 6655 2222 machinery We are MAN Energy Solutions SE, the force of Berlin, Germany innovation behind the world’s leading large-bore MAN Energy Solutions SE engines and turbomachinery for marine and Egellsstr. 21 13507 Berlin, Germany stationary applications. Our home is in Augsburg, Phone +49 30 440402-0 | Fax +49 30 440402-2000 Germany. But we are also close to you, in over 100 countries, with more than 15,000 employees Changzhou, China who dedicate each workday to our customer’s MAN Diesel & Turbo China Production Co. Ltd. Fengming Road 9, Wujin High-Tech Industrial Zone satisfaction. 213164 Changzhou, P. R. China Phone +86 519 8622-7001 | Fax +86 519 8622-7002 Our products are an integral part of Between 1893 and 1897, Rudolf custom, fully integrated train solutions most energy and transportation solu- Diesel and a group of M.A.N. engineers that are unsurpassed in performance, Deggendorf, Germany tions that surround you every day. We developed the first diesel engine in efficiency and reliability. MAN Energy Solutions SE produce world-class marine propulsion Augsburg, and in 1904 we produced Werftstr. 17 systems, turbomachinery for the our first steam turbine in Oberhausen.
    [Show full text]
  • Wind Energy Glossary: Technical Terms and Concepts Erik Edward Nordman Grand Valley State University, [email protected]
    Grand Valley State University ScholarWorks@GVSU Technical Reports Biology Department 6-1-2010 Wind Energy Glossary: Technical Terms and Concepts Erik Edward Nordman Grand Valley State University, [email protected] Follow this and additional works at: http://scholarworks.gvsu.edu/bioreports Part of the Environmental Indicators and Impact Assessment Commons, and the Oil, Gas, and Energy Commons Recommended Citation Nordman, Erik Edward, "Wind Energy Glossary: Technical Terms and Concepts" (2010). Technical Reports. Paper 5. http://scholarworks.gvsu.edu/bioreports/5 This Article is brought to you for free and open access by the Biology Department at ScholarWorks@GVSU. It has been accepted for inclusion in Technical Reports by an authorized administrator of ScholarWorks@GVSU. For more information, please contact [email protected]. The terms in this glossary are organized into three sections: (1) Electricity Transmission Network; (2) Wind Turbine Components; and (3) Wind Energy Challenges, Issues and Solutions. Electricity Transmission Network Alternating Current An electrical current that reverses direction at regular intervals or cycles. In the United States, the (AC) standard is 120 reversals or 60 cycles per second. Electrical grids in most of the world use AC power because the voltage can be controlled with relative ease, allowing electricity to be transmitted long distances at high voltage and then reduced for use in homes. Direct Current A type of electrical current that flows only in one direction through a circuit, usually at relatively (DC) low voltage and high current. To be used for typical 120 or 220 volt household appliances, DC must be converted to AC, its opposite. Most batteries, solar cells and turbines initially produce direct current which is transformed to AC for transmission and use in homes and businesses.
    [Show full text]
  • Hydroelectric Power -- What Is It? It=S a Form of Energy … a Renewable Resource
    INTRODUCTION Hydroelectric Power -- what is it? It=s a form of energy … a renewable resource. Hydropower provides about 96 percent of the renewable energy in the United States. Other renewable resources include geothermal, wave power, tidal power, wind power, and solar power. Hydroelectric powerplants do not use up resources to create electricity nor do they pollute the air, land, or water, as other powerplants may. Hydroelectric power has played an important part in the development of this Nation's electric power industry. Both small and large hydroelectric power developments were instrumental in the early expansion of the electric power industry. Hydroelectric power comes from flowing water … winter and spring runoff from mountain streams and clear lakes. Water, when it is falling by the force of gravity, can be used to turn turbines and generators that produce electricity. Hydroelectric power is important to our Nation. Growing populations and modern technologies require vast amounts of electricity for creating, building, and expanding. In the 1920's, hydroelectric plants supplied as much as 40 percent of the electric energy produced. Although the amount of energy produced by this means has steadily increased, the amount produced by other types of powerplants has increased at a faster rate and hydroelectric power presently supplies about 10 percent of the electrical generating capacity of the United States. Hydropower is an essential contributor in the national power grid because of its ability to respond quickly to rapidly varying loads or system disturbances, which base load plants with steam systems powered by combustion or nuclear processes cannot accommodate. Reclamation=s 58 powerplants throughout the Western United States produce an average of 42 billion kWh (kilowatt-hours) per year, enough to meet the residential needs of more than 14 million people.
    [Show full text]
  • Hydropower Technologies Program — Harnessing America’S Abundant Natural Resources for Clean Power Generation
    U.S. Department of Energy — Energy Efficiency and Renewable Energy Wind & Hydropower Technologies Program — Harnessing America’s abundant natural resources for clean power generation. Contents Hydropower Today ......................................... 1 Enhancing Generation and Environmental Performance ......... 6 Large Turbine Field-Testing ............................... 9 Providing Safe Passage for Fish ........................... 9 Improving Mitigation Practices .......................... 11 From the Laboratories to the Hydropower Communities ..... 12 Hydropower Tomorrow .................................... 14 Developing the Next Generation of Hydropower ............ 15 Integrating Wind and Hydropower Technologies ............ 16 Optimizing Project Operations ........................... 17 The Federal Wind and Hydropower Technologies Program ..... 19 Mission and Goals ...................................... 20 2003 Hydropower Research Highlights Alden Research Center completes prototype turbine tests at their facility in Holden, MA . 9 Laboratories form partnerships to develop and test new sensor arrays and computer models . 10 DOE hosts Workshop on Turbulence at Hydroelectric Power Plants in Atlanta . 11 New retrofit aeration system designed to increase the dissolved oxygen content of water discharged from the turbines of the Osage Project in Missouri . 11 Low head/low power resource assessments completed for conventional turbines, unconventional systems, and micro hydropower . 15 Wind and hydropower integration activities in 2003 aim to identify potential sites and partners . 17 Cover photo: To harness undeveloped hydropower resources without using a dam as part of the system that produces electricity, researchers are developing technologies that extract energy from free flowing water sources like this stream in West Virginia. ii HYDROPOWER TODAY Water power — it can cut deep canyons, chisel majestic mountains, quench parched lands, and transport tons — and it can generate enough electricity to light up millions of homes and businesses around the world.
    [Show full text]
  • AP-42, Vol. I, 3.1: Stationary Gas Turbines
    3.1 Stationary Gas Turbines 3.1.1 General1 Gas turbines, also called “combustion turbines”, are used in a broad scope of applications including electric power generation, cogeneration, natural gas transmission, and various process applications. Gas turbines are available with power outputs ranging in size from 300 horsepower (hp) to over 268,000 hp, with an average size of 40,200 hp.2 The primary fuels used in gas turbines are natural gas and distillate (No. 2) fuel oil.3 3.1.2 Process Description1,2 A gas turbine is an internal combustion engine that operates with rotary rather than reciprocating motion. Gas turbines are essentially composed of three major components: compressor, combustor, and power turbine. In the compressor section, ambient air is drawn in and compressed up to 30 times ambient pressure and directed to the combustor section where fuel is introduced, ignited, and burned. Combustors can either be annular, can-annular, or silo. An annular combustor is a doughnut-shaped, single, continuous chamber that encircles the turbine in a plane perpendicular to the air flow. Can-annular combustors are similar to the annular; however, they incorporate several can-shaped combustion chambers rather than a single continuous chamber. Annular and can-annular combustors are based on aircraft turbine technology and are typically used for smaller scale applications. A silo (frame-type) combustor has one or more combustion chambers mounted external to the gas turbine body. Silo combustors are typically larger than annular or can-annular combustors and are used for larger scale applications. The combustion process in a gas turbine can be classified as diffusion flame combustion, or lean- premix staged combustion.
    [Show full text]
  • Modelling of a Turbojet Gas Turbine Engine
    The University of Manchester Research Modelling of a turbojet gas turbine engine Document Version Accepted author manuscript Link to publication record in Manchester Research Explorer Citation for published version (APA): Klein, D., & Abeykoon, C. (2015). Modelling of a turbojet gas turbine engine. In host publication (pp. 198-204) Published in: host publication Citing this paper Please note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscript or Proof version this may differ from the final Published version. If citing, it is advised that you check and use the publisher's definitive version. General rights Copyright and moral rights for the publications made accessible in the Research Explorer are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Takedown policy If you believe that this document breaches copyright please refer to the University of Manchester’s Takedown Procedures [http://man.ac.uk/04Y6Bo] or contact [email protected] providing relevant details, so we can investigate your claim. Download date:02. Oct. 2021 Modelling of a Turbojet Gas Turbine Engine Dominik Klein Chamil Abeykoon Division of Applied Science, Computing and Engineering, Division of Applied Science, Computing and Engineering, Glyndwr University, Mold Road, LL11 2AW, Wrexham, Glyndwr University, Mold Road, LL11 2AW, Wrexham, United Kingdom United Kingdom E-mail: [email protected] E-mail: [email protected]; [email protected] Abstract—Gas turbines are one of the most important A.
    [Show full text]
  • Horizontal Axis Water Turbine: Generation and Optimization of Green Energy
    International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 5 (2018) pp. 9-14 © Research India Publications. http://www.ripublication.com Horizontal Axis Water Turbine: Generation and Optimization of Green Energy Disha R. Verma1 and Prof. Santosh D. Katkade2 1Undergraduate Student, 2Assistant Professor, Department of Mechanical Engineering, Sandip Institute of Technology & Research Centre, Nashik, Maharashtra, (India) 1Corresponding author energy requirements. Governments across the world have been Abstract creating awareness about harnessing green energy. The The paper describes the fabrication of a Transverse Horizontal HAWT is a wiser way to harness green energy from the water. Axis Water Turbine (THAWT). THAWT is a variant of The coastal areas like Maldives have also been successfully Darrieus Turbine. Horizontal Axis Water Turbine is a turbine started using more of the energy using such turbines. The HAWT has been proved a boon for such a country which which harnesses electrical energy at the expense of water overwhelmingly depends upon fossil fuels for their kinetic energy. As the name suggests it has a horizontal axis of electrification. This technology has efficiently helped them to rotation. Due to this they can be installed directly inside the curb with various social and economic crisis [2]. The water body, beneath the flow. These turbines do not require complicated remote households and communities of Brazil any head and are also known as zero head or very low head have been electrified with these small hydro-kinetic projects, water turbines. This Project aims at the fabrication of such a where one unit can provide up to 2kW of electric power [11].
    [Show full text]
  • The Effect of the Process on Turbomachinery Reliability)
    “DO AS I SAY” (THE EFFECT OF THE PROCESS ON TURBOMACHINERY RELIABILITY) by William E. Forsthoffer President Forsthoffer Associates Inc., Washington Crossing, Pennsylvania William E. (Bill) Forsthoffer spent six years at the Delaval Turbine Company, as Manager of Compressor Project Engi- neering, where he designed and tested centrifugal pumps and compressors, gears, steam turbines, and rotary (screw) pumps. Mr. Forsthoffer then joined the Mobil Research and Development Corporation. For five years, he directed the application, selection, design, testing, site precommis- sioning, and startup of the Yanbu Petrochemical complex in Yanbu, Saudi Arabia. Following that, he returned to MRDC and established a technical service program for Mobil affiliates to provide application, troubleshooting, and Figure 1. Diagram of Centrifugal Pump. training services for rotating equipment. He left Mobil in 1990 to found his own company, Forsthoffer Associates, Inc., to provide training, critical equipment selection, and troubleshooting services to the refining, petrochemical, utility, and gas transmission industries. Mr. Forsthoffer is a graduate of Bellarmine College with a B.A. degree (Mathematics) and from the University of Detroit with a B.S. degree (Mechanical Engineering). ABSTRACT This tutorial examines the primary cause of lower than expected reliability in turbomachines, the effect of the process on machinery component life. Over 95 percent of the rotating equipment installed in any refinery, petrochemical, or gas plant is the dynamic or “turbo” type. Their characteristics are limited energy output and variable flow rate determined by process energy requirements. INTRODUCTION Figure 2. Centrifugal Pump Component Damage and Causes. The objective of this tutorial is to emphasize the importance of understanding the effect of the process on turbomachinery reliability.
    [Show full text]
  • Turbomachinery Technology for High-Speed Civil Flight
    4 NASA Technical Memorandum 102092 . Turbomachinery Technology for High-speed Civil Flight , Neal T. Saunders and Arthur J. Gllassman Lewis Research Center Cleveland, Ohio Prepared for the 34th International Gas Turbine Aepengine Congress and Exposition sponsored by the American Society of Mechanical Engineers Toronto, Canada, June 4-8, 1989 ~ .. (NASA-TH-102092) TURBOHACHINERY TECHPCLOGY N89-24320 FOR HIGH-SPEED CIVIL FLIGHT (NBSEL, LEV& Research Center) 26 p CSCL 21E Unclas G3/07 0217641 TURBOMACHINERY TECHNOLOGY FOR HIGH-SPEED CIVIL FLIGHT Neal T. Saunders and Arthur J. Glassman ABSTRACT This presentation highlights some of the recent contributions and future directions of NASA Lewis Research Center's research and technology efforts applicable to turbomachinery for high-speed flight. For a high-speed civil transport application, the potential benefits and cycle requirements for advanced variable cycle engines and the supersonic throughflow fan engine are presented. The supersonic throughf low fan technology program is discussed. Technology efforts in the basic discipline areas addressing the severe operat- ing conditions associated with high-speed flight turbomachinery are reviewed. Included are examples of work in internal fluid mechanics, high-temperature materials, structural analysis, instrumentation and controls. c INTRODUCTION Future Emphasis Shifting to High-speed Flight Two years ago, the aeronautics community commemorated the 50th anniversary of the first successful operation of a turbojet engine. This remarkable feat by Sir Frank Whittle represents the birth of the turbine engine industry, which has greatly refined and improved Whittle's invention into the splendid engines that are flying today. NASA, as did its predecessor NACA, has assisted indus- try in the creation and development of advanced technologies for each new gen- eration of engines.
    [Show full text]
  • Application Note Acoustic Excitation of Turbomachinery Blisks
    www.mpihome.com Application Note Acoustic Excitation of Turbomachinery Blisks ■ Generating an engine order excitation ■ m+p’s acoustic blisk excitation software ■ Analyzing the dynamic responses of ■ m+p Analyzer for data capture and post-processing turbomachinery blisks ■ m+p VibRunner acquisition hardware ■ Four sine excitation modes During operation wind, gas and steam turbine blades are subject to high dynamic forces introduced by the working fluid. In order to assess the structural health of the blades, dynamic analyses are carried out in laboratory tests. Highly specialized test rigs are designed for analyses of blades in rotating and stationary operating conditions. Especially for stationary tests, it is crucial to artificially replicate the typical excitations acting on the rotor blades during operation, known as engine order excitation. m+p international designed a software package which enables engineers to generate an engine order excitation and analyze the dynamic responses of the turbomachinery blisks in the safety of the laboratory. Application Note Acoustic Excitation of Turbomachinery Blisks 1 Background: During operation the working fluid acts on the rotating turbine blades, creating a pulsating pressure field. Circumferentially expanding this pressure field yields a harmonic series whose coefficients are called engine orders. Basically, an engine order describes the number of sine waves traveling along the circumference of the rotor (figure 1). The corresponding excitation frequency is the product of the rotational speed and the specific engine order, EO. Only a few engine orders will be encountered during operation. Thus, it is often possible to reduce the whole pressure field to a single engine order. m+p international’s acoustic blisk excitation software replicates this engine order excitation by controlling the given actuators accordingly.
    [Show full text]
  • Selection of Turbomachinery-Centrifugal Compressors
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Texas A&M Repository SELECTION OF TURBOMACHINERY-CENTRIFUGAL COMPRESSORS by Gary A. Ehlers Senior Supervising Engineer Ralph M. Parsons Company Pasadena, California INTRODUCTION Gary A. Ehlers, is Senior Supervising Selection of a centrifugal compressor starts with performance Engineer in the Rotating Equipment Engi­ calculations. After basic machine performance is determined, neering group ofthe Engineering Department the mechanical construction is addressed. The primary areas of at Ralph M. Parsons Company, Pasadena, concern are metallurgy, shaft sealing and rotordynamics. California. He supervises the activities re­ Rotordynamics analysis (RDA) of turbomachinery designs lated to the rotating equipment engineering should be made during selection. A lateral critical speed study on projects. Thetypes of machineryrespon­ includes undamped critical speed analysis, plot of the undamped sibilities include centrifugaland reciprocat­ critical speeds as a functionof stiffness, synchronous unbalance ing compressors, axial flow compressors, response analysis, and stability analysis. The stability analysis is steam and gas turbines, centrifugal and concerned with all calculated subharmonic, self-excited vibra­ reciprocating pumps, and gas expanders. tions of the rotor. Oil whirl is one such common example of He has been employed at Parsons for the last 20years and previously subharmonic instability of concern in design of the rotor bearing at Worthington Compressor and Engine International as an Appli­ support of turbomachinery. Other instabilities result from dis­ cation Engineer in power and process marketing. turbing/destabilizing forces from aerodynamic sources or shaft Hehas worked on primarily refinerytype projects domestically,in seal design. the Middle East, and Asia and on cogeneration and oil production Rotordynamics of a centrifugal compressor with oil film seals type projects.
    [Show full text]