The basic element in a turbine is a wheel or rotor with addles, propellers, blades, or buckets arranged on its circumference in. Pdf power plant lecture notes chapter4 steam turbine. 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. What are the various types of nozzles and their functions. 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.
Supersaturated flow or metastable flow of in nozzles. 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. Mcqs steam boilers, engines, nozzles and turbines questions. Rotor means which part rotate and stator means which part is fixed. The modeled assembly of nozzle for pelton turbine consists of nozzle pipe of converging crosssectional area, spear and a free surface flow domain. The highpressure steam from the boiler is expanded in nozzles to create a highvelocity jet of steam. One the threshold is exceeded, automatic trip of turbine takes place. 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. Steam boilers, engines, nozzles and turbines questions and answers pdf free download for freshers and experienced mechanical engineering students. May 05, 2015 the nozzle also sets the total mass flow rate through the engine as described on a separate slide. 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. For example if the turbine consists of 10 nozzles for full power100 %. 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. Harris hydroelectric turbine generator adjustable p.
The nozzle serves to emit a pressurized water flow. The influence of nozzle clearance on the flow field for a variable nozzle turbine, and moreover on the turbine stage performance was numerically investigated. The axial split casing allows easy access for onsite inspection and repair. Curtis to solve the problems of a singlestage impulse turbine for use with high pressure and temperature steam. Nozzle performance parameters, discharge coefficient, and. Thermal modeling and analysis of high pressure steam turbine. As is well known, prolonging the service time of the eroded nozzle will. In noncondensing turbines or backpressure turbines, steam exhausts at a pressure greater than atmospheric. Supersonic flow in cdnozzles presents a rich behaviour, with shock waves and expansion. Harris hydroelectric turbine generator 1500w max, 14 nozzles. The condensing type, which is typical of larger turbines, is subject to attracting force due to vacuum pressure on the exhaust side.
This divides the velocity drop across the stage into several smaller drops. The failure analysis of the 70 mw gas turbine first stage nozzle made of cobaltbase alloy fsx414 is presented. The whirl of the turbine exit flow is reduced by the turbine rear support struts, which turn the flow straight. What are the effects of friction on the flow through a steam nozzle. A highvelocity steam is coming from the nozzles and it strikes the rotating blades which are fitted on a disc mounted on a shaft. Steam turbine uprates ge power systems ger4199 5 valves inlet bridge c. Oxidizer and fuel pumps are powered by combustion turbines that use fuel and engine oxidant as fuel or have other fuel 16, s.
Effect of nozzle angle and silt parameters on erosion and. Flow of gases and steam through nozzles example, the required pressure in the combustion chamber of the space shuttle ssme engine was 20. Unit iii steam nozzles and turbines flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,supersaturated flow. However, the mathematics which describe the operation of the nozzle takes some careful thought.
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. 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. The main use of steam nozzle in steam turbines is to produce a jet of steam with a high velocity. This hydroelectric battery charger uses a harris cast bronze pelton wheel and an alternator in a powder coated aluminum housing. What are the advantages of convergent divergent nozzle. 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. The curtis stage turbine, as it came to be called, is composed of one stage of nozzles as the singlestage.
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. The steam enters the nozzle at high pressure with negligible velocity and leaves at high velocity with low pressure. The control of turbine with a governor is essential. The modeled assembly consists of inlet, nozzle, spear and outlet. Steam then leaves the turbine and is utilized in other parts. When the crosssection of a nozzle decreases continuously from entrance to exit, it is called a convergent nozzle. 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.
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. Schematic diagram of a converging nozzle assuming steady flow and conservation of masses. Ed nelson is a tu rbo machinery consultant based in dickinson, texas. Nelson turbomachinery consultant dickinson, texas and perryc. 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. As shown above, nozzles come in a variety of shapes and sizes depending on the mission of the aircraft. 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.
Fuel to the primary diffusion fuel nozzles and single tertiary premixing fuel nozzle. Why is a nozzle used only impulse turbines, and not in. Turbine, pump, nozzle, throttling, the mathematical expression of the 1st law for a closed system, examples of. This governing is made by getting down the pressure of the steam. Steam turbine and steam nozzle interview question and.
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. Convergentdivergent nozzles are used in back pressure turbine. 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. A steam turbine consists of a rotor resting on bearings and enclosed in a cylindrical casing. 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 pressure of the steam when it moves over the blades remains constant but the velocity decreases. 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. These parameters describe how efficiently a turbine, compressor or nozzle approximates a corresponding isentropic device.
Schematic diagram of model turbine the resource of required water is. 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. 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. The present report describes tests on a twodimensional nozzle cascade having a design based on the nozzle of the first turbine 3 in the n. 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. Impulse turbine and reaction turbineprinciple, working. A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. Numerical simulation for pressure distribution in pelton. This mode is used from 81% corrected speed to a preselected combustion reference temperature. They are 20%, 40%, 60%, 80% and 100% nozzle opening position. A convergingdiverging nozzle condi nozzle, or cd nozzle, is the only one to get supersonic flows with m 1 when chocked. The utilization factor for a fixed nozzle angle will increase as the reaction approaches 100%. Thus a steam turbine could be viewed as a complex series of windmilllike arrangements, all assembled on the same shaft.
This gives the advantage on throttle governing where the. 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. Gas exits the stationary turbine nozzle guide vanes at absolute velocity va1. The modeled assembly of free surface flow domain consists of extended outlet. Turbine is a rotary engine that converts the energy of a moving stream of water, steam, or gas into mechanical energy. In this type, the total pressure drop expansion of the steam take place only in the first nozzle ring. Applications of steam turbines power generation transport 4. Gas turbine compressor cleaning nozzles gas turbine nozzle systems for all gas turbine engines in the range of 0. 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. These procedures are in keeping with the iso 9000 standards embraced by ge and its repair organ izations. Archived from the original pdf on 28 september 2011. What is the purpose of divergent portion after the throat section of nozzle. The impulse blades are short and have constant cross sections. Supersonic flow in cd nozzles presents a rich behaviour, with shock waves and expansion.
In a practical situation the load frequently varies from the designed or economic. Understanding and preventing steam turbine overspeeds by william e. 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. Reaction turbine 2 iii steam turbine operating range 2.
The nozzle experience cracks in different vane airfoil sections assisted by base alloy degradation due to an operation at high. The following section consists of steam nozzles and turbines questions on physics. 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. Above 600 rpm rotor relative vibrations should be monitored. Pdf cooling performance analysis of steam cooled gas. These criteria and formulae are based on work undertaken by siervo. Nozzle is a duct of varying crosssectional area in which the velocity increases with the corresponding drop in pressure. The real values of critical speeds should be measured at. Turbine casing steam chest governor valve body steam ring nozzles stationary reversing blades stationary reversing chambers diaphragm stage, turbine. Steam turbines provide electric power generation in. The steam turbine is a device for obtaining mechanical work from the energy stored in steam. Thermal engineering pdf of rk rajput for mechanical.
Impulse turbines singlerotor or multirotor are simple stages of the turbines. Reaction turbine 2 iii steam turbine operating range 2 3. 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. Steam enters the turbine with a high energy content and leaves after giving up most of it. 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. 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.
Steam turbine 1 content chapter description page i purpose 2 ii steam turbine types 2 2. Because the nozzle does no thermodynamic work, the total temperature tt through the nozzle is. This increase in velocity increases the power generation of the turbine. The timetested reliability of the rlha turbine makes it an ideal. Due to the high velocities, the time up to which the steam resides in the nozzle is small, and there may not be sufficient. Steam turbine two types of steam turbines were considered with an fem analysis, those being back pressure type and condensing type. When the steam turbine used for long time, the steam path is deteriorated, and both output and efficiency of the turbine. Effects of mach number and flow incidence on aerodynamic. The cross flow turbine consists of two main parts namely the nozzle and the turbine runner. 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. He retired fro m amoco oil company, after more than 36 years in.
The rotor is turned by steam impinging against attached vanes or blades on which it exerts a force in the tangential direction. This turbine is a velocity compounded curtis stage having a pressure ratio of 221 and a design mach number from the nozzles of 2. 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. This model is available with 1, 2 or 4 nozzles installed at the factory. Isentropic process is a special case of adiabatic processes. Impulse and reaction principles, compounding, velocity diagrams for simple and multistage turbines, speed regulationsgovernors and nozzle governors. The loss of energy due to this higher exit velocity is commonly known as carry over loss or leaving loss. The nozzles two primary functions are to generate thrust and to act as a control valve for the engine. Development of titanium 3600rpm50inch and 3000rpm60inch. Working principle of steam turbine depends on the dynamic action of steam.
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. Boyce, in gas turbine engineering handbook fourth edition, 2012. When the steam passes through the stationary nozzles and is directed at high velocity against the rotor buckets. Experimental and numerical computational fluid dynamics. 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. Turbine losses 5 116 hiope the nozzle and bucket profiles have been manufactured with a specified surface finish and with strict tolerance. The velocitycompounded impulse turbine was first proposed by c. The ratio between nozzle inlet temperature and critical temperature is given by. In turbines there are basically 2 part one is called rotor and another is known as stator.
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. The impulse turbine is a reaction turbine with a reaction of zero r 0. There is a reason why nozzles are not required for reaction turbines. Mar 07, 2015 as v1 may 01, 2015 gas turbine nozzle saran thammasirikul. Steam turbine working principle and types of steam turbine.
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. Steam turbine governing and its mechanism ece tutorials. Nozzle is the stator part of turbine means it is fixed part. There are two classical types of turbine stage designs. 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. Rochem designs and manufactures nozzle and manifold systems for cleaning the compressor on industrial and aero derivative gas turbines. The smallest section of the nozzle is called throat. The variation in load during the operation of a steam turbine can have a significant impact on its performance.
Modification of nozzles for the improvement of efficiency of. This chapter describes the exhaust nozzle and its application to aircraft gas turbine engines. Multiple choice questions on steam nozzles and turbines. 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. Abstract this chapter describes the exhaust nozzle and its application to aircraft gas turbine engines. This parameter reduces the overall efficiency and work output. May 05, 2015 the nozzle sits downstream of the power turbine. Moving blades work due to differential pressure of steam between front and at behind of. This highvelocity steam produces dynamic pressure on the blades in which blades and shaft both start to rotate in the same. It was discovered that the turbine governor could be. 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. Nozzle angle, erosive wear, efficiency loss, turgo turbine, jet velocity. The turbine runner is constructed of two discs or parallel diks connected together with several curved spindles arranged in series. Understanding and preventing steam turbine overspeeds by.