Steam turbine 1 content chapter description page i purpose 2 ii steam turbine types 2 2. Turbine casing steam chest governor valve body steam ring nozzles stationary reversing blades stationary reversing chambers diaphragm stage, turbine. Turbine losses 5 116 hiope the nozzle and bucket profiles have been manufactured with a specified surface finish and with strict tolerance. Jul 05, 2016 the steam leaves the nozzle with a very high velocity and strikes the blades of the turbine mounted on a wheel with this high velocity. A highvelocity steam is coming from the nozzles and it strikes the rotating blades which are fitted on a disc mounted on a shaft. Impulse turbines singlerotor or multirotor are simple stages of the turbines. The main use of steam nozzle in steam turbines is to produce a jet of steam with a high velocity. The control of turbine with a governor is essential. Nozzle performance parameters, discharge coefficient, and. The modeled assembly of free surface flow domain consists of extended outlet. Feb 21, 2008 then, in a cd nozzle, the pressure there can still drop because the flow is accelerating out the back in the diverging section supersonic flow acts exactly opposite to sub sonic in this regard. Forcemoment calculation nema sm 23 requires that the forces and moments acting on steam turbines due to the steam inlet, extraction, and exhaust connections should be evaluated by simple set of forcemoment calculation similar to centrifugal compressors. Steam then leaves the turbine and is utilized in other parts. Reaction turbine 2 iii steam turbine operating range 2 3.
A velocitycompounded impulse stage consist of a row of fixed nozzles followed by two or more rows of moving blades and fixed blades without expansion. Working principle of steam turbine depends on the dynamic action of steam. Mar 07, 2015 as v1 may 01, 2015 gas turbine nozzle saran thammasirikul. Above 600 rpm rotor relative vibrations should be monitored. This also can represent convergent nozzle for a fluid whose peculiarity is that while both velocity and specific volume increase, the rate of specific volume increase is less than that of the velocity, thus resulting in increasing value of v 200 elements of heat engines vol.
Micro hydro power generation use a lot of crossflow turbine, being able to operate at a low head and under a small water flow rate, because ones the water jet from the turbine nozzle entering the turbine runner it would hit the blade twice and move the turbine blades 10, 11. The nozzles two primary functions are to generate thrust and to act as a control valve for the engine. There are two classical types of turbine stage designs. Steam enters the turbine with a high energy content and leaves after giving up most of it. Oxidizer and fuel pumps are powered by combustion turbines that use fuel and engine oxidant as fuel or have other fuel 16, s. The nozzle experience cracks in different vane airfoil sections assisted by base alloy degradation due to an operation at high. Unit iii steam nozzles and turbines flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,supersaturated flow. Ed nelson is a tu rbo machinery consultant based in dickinson, texas.
As steam expands in the nozzle, the pressure and temperature in it drop, and it is likely that the steam start condensing when it strikes the saturation line. Thermal engineering pdf of rk rajput for mechanical. In variable nozzle geometry turbines vnt, opening of the nozzles is used to control turbine mass flow and expansion ratio, allowing more turbine power to be. These criteria and formulae are based on work undertaken by siervo. The curtis stage turbine, as it came to be called, is composed of one stage of nozzles as the singlestage. The rotor is turned by steam impinging against attached vanes or blades on which it exerts a force in the tangential direction. Turbine, pump, nozzle, throttling, the mathematical expression of the 1st law for a closed system, examples of. Gas exits the stationary turbine nozzle guide vanes at absolute velocity va1. The steam enters the nozzle at high pressure with negligible velocity and leaves at high velocity with low pressure. What are the various types of nozzles and their functions. Design and fabrication of cmscale tesla turbines by vedavalli gomatam krishnan a dissertation submitted in partial satisfaction of the requirements for the degree of doctor of philosophy in engineering electrical engineering and computer sciences in the graduate division of the university of california, berkeley committee in charge.
Uncontrolled acceleration of the turbine rotor cam lead to an over speed trip, which causes the nozzle valves that control the flow of steam to the turbine to close. Definition a steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft. The following section consists of steam nozzles and turbines questions on physics. Impulse and reaction principles, compounding, velocity diagrams for simple and multistage turbines, speed regulationsgovernors and nozzle governors. If the load demand has reduced to 60 % then out of 10 nozzles, 4 nozzles can be closed to provide 60% load with out delay. Understanding and preventing steam turbine overspeeds by william e. Vanita thakkar bit 17 nozzles a nozzle is a device, a duct of smoothly varying cs area, that increases the velocity of a fluid at the expense of pressure. There is a reason why nozzles are not required for reaction turbines.
Why is a nozzle used only impulse turbines, and not in. Supersonic flow in cdnozzles presents a rich behaviour, with shock waves and expansion. These procedures are in keeping with the iso 9000 standards embraced by ge and its repair organ izations. The timetested reliability of the rlha turbine makes it an ideal. Steam turbine and steam nozzle interview question and. Turbine is a rotary engine that converts the energy of a moving stream of water, steam, or gas into mechanical energy. Schofield ge company schenectady, ny introduction the need to provide stateoftheart products for a diverse and everchanging market is the chal lenge facing steam turbinegenerator manufactur ers in the 90s.
What are the advantages of convergent divergent nozzle. Effects of mach number and flow incidence on aerodynamic. They are 20%, 40%, 60%, 80% and 100% nozzle opening position. Impulse turbine and reaction turbineprinciple, working. Convergentdivergent nozzles are used in back pressure turbine. Schematic diagram of a converging nozzle assuming steady flow and conservation of masses. Moving blades work due to differential pressure of steam between front and at behind of. When the steam passes through the stationary nozzles and is directed at high velocity against the rotor buckets. A dropin nozzle block 40 formed in two 180 segments 52 that can be simply lowered into position within the nozzle chamber casing of a steam turbine 42.
The failure analysis of the 70 mw gas turbine first stage nozzle made of cobaltbase alloy fsx414 is presented. This mode is used from 81% corrected speed to a preselected combustion reference temperature. This parameter reduces the overall efficiency and work output. Steam turbine two types of steam turbines were considered with an fem analysis, those being back pressure type and condensing type. The nozzle is a circular guide mechanism, which guides the water to flow at a designed direction and also to regulate the flow of water. Flow of gases and steam through nozzles example, the required pressure in the combustion chamber of the space shuttle ssme engine was 20. Thus a steam turbine could be viewed as a complex series of windmilllike arrangements, all assembled on the same shaft. The impulse blades are short and have constant cross sections. Understanding and preventing steam turbine overspeeds by. The modeled assembly consists of inlet, nozzle, spear and outlet. The condensing type, which is typical of larger turbines, is subject to attracting force due to vacuum pressure on the exhaust side. Compounding of steam turbines is the strategy in which energy from the steam is extracted in a number of stages rather than a single stage in a turbine.
Example 3 power generation by a steam turbine the power output of an adiabatic steam turbine is 5 mw, and the inlet and the exit conditions of the steam are as indicated in figure a compare the magnitudes of. The chief use of nozzle is to produce a jet of steam or gas of high velocity to produce thrust for the propulsion of rocket motors and jet engines and to drive steam or gas turbines. Because the nozzle does no thermodynamic work, the total temperature tt through the nozzle is. The pressure of the steam when it moves over the blades remains constant but the velocity decreases. Applications of steam turbines power generation transport 4. The influence of nozzle clearance on the flow field for a variable nozzle turbine, and moreover on the turbine stage performance was numerically investigated.
Pdf power plant lecture notes chapter4 steam turbine. Steam turbine governing and its mechanism ece tutorials. Harris hydroelectric turbine generator 1500w max, 14 nozzles. As shown above, nozzles come in a variety of shapes and sizes depending on the mission of the aircraft. May 05, 2015 the nozzle sits downstream of the power turbine. Exhaust hoods to the condenser gradually increase in area like a diffuser and thus, there is a further decrease in velocity of steam and an increase in pressure as steam. It was discovered that the turbine governor could be. In turbines there are basically 2 part one is called rotor and another is known as stator. The smallest section of the nozzle is called throat. This governing is made by getting down the pressure of the steam. The curtis stage turbine, as it came to be called, is composed of one stage of nozzles as the singlestage turbine, followed by two rows of moving blades instead of one. This increase in velocity increases the power generation of the turbine.
The modeled assembly of nozzle for pelton turbine consists of nozzle pipe of converging crosssectional area, spear and a free surface flow domain. Gas turbine compressor cleaning nozzles gas turbine nozzle systems for all gas turbine engines in the range of 0. This turbine is a velocity compounded curtis stage having a pressure ratio of 221 and a design mach number from the nozzles of 2. Nov, 2015 since the velocity of steam leaving the last stage of turbine is quite large 100120 ms, there will be energy losses due to friction in the exhaust hood of the turbine. Abstract this chapter describes the exhaust nozzle and its application to aircraft gas turbine engines. Cooling performance analysis of steam cooled gas turbine nozzle guide vane article pdf available in international journal of heat and mass transfer 621 july 20 with 572 reads. He retired fro m amoco oil company, after more than 36 years in.
As is well known, prolonging the service time of the eroded nozzle will. Numerical simulation for pressure distribution in pelton. May 05, 2015 the nozzle also sets the total mass flow rate through the engine as described on a separate slide. This model is available with 1, 2 or 4 nozzles installed at the factory.
Introduction 1turgo turbine is a medium head impulse turbine 15 300 m that operates in the head range where pelton and francis turbine overlap anagnostopoulos and papantonis, 2007. Steam boilers, engines, nozzles and turbines questions and answers pdf free download for freshers and experienced mechanical engineering students. Boyce, in gas turbine engineering handbook fourth edition, 2012. Steam turbine uprates ge power systems ger4199 5 valves inlet bridge c. The velocitycompounded impulse turbine was first proposed by c.
For example if the turbine consists of 10 nozzles for full power100 %. This chapter describes the exhaust nozzle and its application to aircraft gas turbine engines. The impulse turbine is a reaction turbine with a reaction of zero r 0. Experimental and numerical computational fluid dynamics. The loss of energy due to this higher exit velocity is commonly known as carry over loss or leaving loss. One the threshold is exceeded, automatic trip of turbine takes place. The variation in load during the operation of a steam turbine can have a significant impact on its performance. The steam turbine is a device for obtaining mechanical work from the energy stored in steam. Steam turbine working principle and types of steam turbine. Nelson turbomachinery consultant dickinson, texas and perryc. Steam turbine 4 128 sst56000 siemens, 280 bar 600 c610 c, net plant efficiency above 45% lhv siemens the function of the steam turbine is to convert the thermal energy contained in the steam into mechanical energy for turning the generator. Development of titanium 3600rpm50inch and 3000rpm60inch. When the steam turbine used for long time, the steam path is deteriorated, and both output and efficiency of the turbine. The real values of critical speeds should be measured at.
In principle, the impulse steam turbine consists of a casing containing stationary steam nozzles and a rotor with moving or rotating buckets. In reaction turbine, there is no nozzle to convert steam energy to mechanical energy. Archived from the original pdf on 28 september 2011. Thermal modeling and analysis of high pressure steam turbine. Jul, 2012 continuous 4th axis machining of an lp stage steam turbine nozzle on a bfw chakra machine using solidcam at chola turbo machinery international pvt ltd. Coppus rlha steam turbines the rlha turbine is an axial split horizontal turbine with split sleeve bearings, available in 4 frame sizes offering up to 4,000 hp 2,980 kw.
A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. The ratio between nozzle inlet temperature and critical temperature is given by. A convergingdiverging nozzle condi nozzle, or cd nozzle, is the only one to get supersonic flows with m 1 when chocked. The highpressure steam from the boiler is expanded in nozzles to create a highvelocity jet of steam. Due to the high velocities, the time up to which the steam resides in the nozzle is small, and there may not be sufficient. Modification of nozzles for the improvement of efficiency of. Then, in a cd nozzle, the pressure there can still drop because the flow is accelerating out the back in the diverging section supersonic flow acts exactly opposite to sub sonic in this regard.
Reaction turbine 2 iii steam turbine operating range 2. The whirl of the turbine exit flow is reduced by the turbine rear support struts, which turn the flow straight. Mar 06, 2011 i have seen some turbine manufacturers have limitations on individual nozzle reactions main steam, cold reheat, hot reheat, steam extractions and steam condenser connections and also limitations of combined reactions transferred on the support anchor and keys of every cylinder like hp, ip and lp casings when all piping connections to the. Mcqs steam boilers, engines, nozzles and turbines questions. What are the effects of friction on the flow through a steam nozzle. The turbine runner is constructed of two discs or parallel diks connected together with several curved spindles arranged in series. In noncondensing turbines or backpressure turbines, steam exhausts at a pressure greater than atmospheric. This hydroelectric battery charger uses a harris cast bronze pelton wheel and an alternator in a powder coated aluminum housing. Nozzle is a duct of varying crosssectional area in which the velocity increases with the corresponding drop in pressure. A steam turbine consists of a rotor resting on bearings and enclosed in a cylindrical casing.
However, the mathematics which describe the operation of the nozzle takes some careful thought. The axial split casing allows easy access for onsite inspection and repair. Isentropic process is a special case of adiabatic processes. Curtis to solve the problems of a singlestage impulse turbine for use with high pressure and temperature steam. Rotor means which part rotate and stator means which part is fixed. The utilization factor for a fixed nozzle angle will increase as the reaction approaches 100%. The nozzle serves to emit a pressurized water flow. At present, repairing the eroded nozzle or replacing it with a new nozzle is the most common method to recover the nozzle efficiency to the normal level.
An entire 180 segment can be lowered into position because an inner arcuate portion 58 of the nozzle block fits over and captures mating portions of the casing rather than. The air exiting the turbine is often traveling greater than mach 1, but this creates high friction losses, so the flow is immediately slowed by diffusion. The basic element in a turbine is a wheel or rotor with addles, propellers, blades, or buckets arranged on its circumference in such a fashion that the moving fluid exerts a tangential force that turns the wheel. The cross flow turbine consists of two main parts namely the nozzle and the turbine runner. Effects of mach number and flow incidence on aerodynamic losses of steam turbine blades teik lin chu abstract an experiment was conducted to investigate the aerodynamic losses of two highpressure steam turbine nozzles 526a, 525b subjected to a large range of incident angle and exit mach number.
This divides the velocity drop across the stage into several smaller drops. The nozzle sits downstream of the power turbine and, while the nozzle does no work on the flow, there are some important design features of the nozzle. The nozzle tip was modified in form, to properly seat and match the newly designed seat ring geometry without sacrificing any of the available stroke of needle stem. The basic element in a turbine is a wheel or rotor with addles, propellers, blades, or buckets arranged on its circumference in. Supersaturated flow or metastable flow of in nozzles. What is the purpose of divergent portion after the throat section of nozzle. In a practical situation the load frequently varies from the designed or economic. These parameters describe how efficiently a turbine, compressor or nozzle approximates a corresponding isentropic device. Nozzle angle, erosive wear, efficiency loss, turgo turbine, jet velocity. Fuel to the primary diffusion fuel nozzles and single tertiary premixing fuel nozzle. Schematic diagram of model turbine the resource of required water is.
Effect of nozzle angle and silt parameters on erosion and. Nozzle is the stator part of turbine means it is fixed part. Pdf cooling performance analysis of steam cooled gas. Steam turbine governing is the procedure of controlling the flow rate of steam to a steam turbine so as to maintain its speed of rotation as constant. Harris hydroelectric turbine generator adjustable p. This highvelocity steam produces dynamic pressure on the blades in which blades and shaft both start to rotate in the same. Supersonic flow in cd nozzles presents a rich behaviour, with shock waves and expansion. This gives the advantage on throttle governing where the. Multiple choice questions on steam nozzles and turbines.
855 514 1401 1114 1220 926 1373 1064 1279 299 812 799 438 1545 477 648 1389 1289 826 1264 1070 1513 453 500 246 1498 971 602 1212 186 530 687 937 1160 430 878 1364 1446 911 1055 516 1445 317 869 1078