INFLUANCE OF CHANGES OF AXIAL COMPRESSOR VARIABLE STATOR VANES SETTING ON GAS TURBINE ENGINE WORK

Transcription

1 INFLUNE OF HNGES OF XIL OMPRESSOR VRILE STTOR VNES SETTING ON GS TURINE ENGINE WOR Paweł Wirkowski The Polish Naval cademy l. Śmidowicza 69, Gdynia, Poland tel.: , fax: bstract The paper deals with problem inflence of changes settings variable stator vanes axial compressor of gas trbine engine on work parameters of compressor and engine. Incorrect operation of change setting system of variable vaness cold make nstable work of compressor and engine. This sitation is nacceptable becase of mechanical overloads which cold demage the engine. This paper presents theoretical analysis of sitation described above and presents reslts of own researches done on real engine. eywords: gas trbine engine, axial compressor, variable stator vanes Parameters, abbreviations and sbscripts: α 1 α W, c a c 1a c 1a cal S S O HP HPT η S i LP LPT LPTPTS m& n p fel P nom π S TS, w z - air stream otlet angle with stator vanes, - setting angle of variable stator vanes, - air stream inlet and otlet angles in rotor vanes, - axial component of air stream absolte speed, - axial component of air stream absolte speed on rotor blades inlet, - calclating vale axial component of air stream absolte speed on rotor blades inlet, - space between high pressre compressor and combstor, - space between low pressre compressor and high pressre compressor, - combstor, - high pessre compressor, - high pressre trbine, - compressor efficiency, - air stream inlet angle on rotor blades, - low pressre compressor, - low pressre trbine, - space between low pressre trbine and power trbine, - air mass flow, - compresssor rotor speed, - fel pressre, - nominal engine power, - compression ratio, - space between high pressre trbine and low pressre trbine, - circmferential speed, - air stream relative speed on inlet and otlet rotor blades, - air stream whirl in rotor, - nmber of inlet gide stator vanes,

2 1. Introdction compressor is a part of gas trbine engine especially sensitive on change their technical state dring operation process. Pollted atmospheric air flowing in compressor cased permanent change of interblades dcts shape, rise of blades srface roghness and change of compressor rotor mass. It exerts an important inflance on compressor stable work, change their characteristic and engine performance and efficiency. In compressor constrction is assembled system of setting change of variable stator vanes its task is made optimal cooperation engine nits dring permanent improvement of compressor characteristic. Pertrbations in operation of this system cold case changes in work of compressor and engine similar like changes of rotational speed or pollted interblades dcts of compressor. 2. Prpose of researches Prpose of investigations made on real engine was determination inflance of incorect operation of axial compressor inlet gide variable stator vanes control system of gas trbine engine on parameters of compressor and engine work. ompressor characteristic is relationship between compression ratio π S, compressor efficiency η S and air flow mass m& and compressor rotational speed n. It makes possible to determine the best condition of compressor and another engine nits mating. haracteristic is sing to select optimal conditions of air flow reglation and assessment of operational factors on compressor parametres. a) b) c) i=0 i>0 i<0 c 1a=c 1a cal w2 c 1a<c 1a cal c 1a>c 1a cal w w w Fig. 1. Schema of flow rond of axial compressor rotor blades dring constant rotor speed and variable air stream inlet angles: a) calclating inlet angle, b) positive inlet angle, c) negative inlet angle ompressor nstable work is explained on Fig. 1. This Fig. presents schema of flow rond of axial stage compressor rotor blade which is moving with constant rotational speed n. For this stage is made change of air flow intensity m&. Fig. 1a presents schema of flow rond for optimal stage efficiency. Relative speed vectors and have parallel direction to center line of blade profile. It cases laminar flow of air stream in interblades dcts. Decrease of air flow intensity (Fig. 1b) for constant circmferential speed cases decrease axial component of air stream absolte speed c a.

3 It takes effect increase of air stream inlet angle i on rotor blades. This sitations favors tearing off laminary bondary layer on convex blades srfaces and forming vortex regions. Similar effect takes place on concave blades srfaces (Fig. 1c) when air flow intensity m& increases dring constant circmferential speed. For critical vales of air stream inlet angle i by formated vortex regions of lower pressre, can occre air stream back off in inlet compressor direction. It cold case rapid rise of stream flctations transmited on engine constrction. This sitation is ndesirable and dengeros on accont of mechanical and thermal overload of engine constrction [2]. Therefore compressor shold be so controlled in operational range of rotational speed that the compressor and engine mating line has a stock of stable work. The main rle of compressor control dring change of their rotational speed or flow intensity is to keep p the stream inlet angles i vales near zero. One of the most poplar ways of axial compressor control is changing their flow dct geometry by application of inlet gide stator vanes or variable stator vanes of several first compressor stages [2]. a) b) c)... variable stator vanes a 1 α 1 a 1 c 1a c 1a c 1a rotor blades Fig. 2. xial compressor stage control by change of setting angle of stator vanes dring changing speed of flow stream: decreasing axial speed, b) calclating axial speed, c) increasing axial speed This soltion makes possibile to change of air stream inlet angle on rotor baldes of compressor stages by change of stator vanes setting angles dring change of compressor rotational speed. Fig. 2 illstrates, on example one stage of compression, rle of reglation of variable stator vanes. For average vales of operational range of compressor rotor speed is sitation on Fig. 2b speed vales and directions with sbscript 1. In this sitation is intermediate angle setting of stator vanes. ir stream inlet angle on rotor blades do not case distrbance of stream flow by interblades dcts. For lower vales of compressor rotor speed and in conseqence lower vales of absolte axial component speed c 1a, it is necessary to redce the stream otlet angle of variable stator vanes α 1 (Fig. 2a). The angle redction range shold allow keeping the same vale of stream inlet angle on rotor blades. nalogical sitation takes place dring work of compressor with higher rotational speed. For higher rotational speed absolte axial component speed c 1a increases. In this sitation for keeping stable work of compressor and in conseqence constant vale of stream inlet angle on rotor blades, it is necessary to increase the stream otlet angle of variable stator vanes Fig. 2c.

4 pplication in gas trbine engine constrction of control system of flow dcts geometry has a bearing on rn of nstable processes [3]. 3. Object and corse of researches The object of researches is type DR 77 marine gas trbine engine. It is three-shafts engine with can-ring-type combstor chamber and reversible power trbine. Fig. 3 illstrates block diagram of DR gas trbine engine with marked control sections of flow dct and measring parameters. T 0, p 0 T 1, p 1 p 21 p 2 T T 5 INLET DUT S p fel FUEL O T S LPTPTS OUTLET DUT IR L P S L P T PT EXHUST GSES HP HPT STRTER GS GENERTOR POWER TURINE PROPULTION LINE Fig. 3. lock diagram of DR gas trbine engine In compressor constrction configration of this engine there are sed inlet gide stator vanes which make possibilities to change setting angle incidance (change of compressor flow dct geometry) in depend on engine load. This process is operated by control system which working medim is compressed air received from last stage of high pressre compressor. On Fig. 4 are presented elements of control system of variable stator vanes Fig. 4. Elements of control system of variable stator vanes DR type engine 1 moving ring, 2 stator vane, 3 cleaning and cooling block, 4 strand, 5 control actator

5 lock diagram of flow control signal is presented on Fig. 5. ompressed air from last stage of high pressre compressor is spllied to working space of control actator by cleaning and cooling block. ompressed air exerts pressre on control actator elements. It cases moving of control piston which is connected with moving ring. This ring moves on circmference of compressor body. Ring is connected with stator vanes by levers. When the ring is moving stator vanes realize rotational motion changing the air stream otlet angle α 1. O HP LENING ND OOLING LO LEED ONTROL TUTOR MOVING RING LEED z Fig. 5. lock diagram of stator vanes change setting mechanism; O combstor, HP high pressre compressor, variable stator vane In cleaning and cooling block are holes. Dring researches air stream was bleeded by holes and less air was spplied to actatir. It cased change of setting angle α W of variable stator vanes and in conseqence of that change of flow dct geometry. Experiment was carry ot an engine load 0,5P nom. For this load setting angle α W of variable vanes takes vale - 4 o. Dring change engine load in whole range from idle to fll load setting angle α W of variable vanes changes in range from -18 o to + 18 o. Realizing experiment a few parameters of engine work was measred and registered for three different setting angle α W of variable vanes: α W = - 4 o, α W = - 11 o, α W = - 18 o. Tab. 1 presents measred and registered parameters of engine work. Tab. 1. Parameters of engine DR work measred dring researches Parameter Measrement range Parameter name n LP [min -1 ] low pressre rotor speed n HP [min -1 ] high pressre rotor speed n PT [min -1 ] power trbine rotor speed p 1-0,04 0 [MPa] sbatmospheric pressre on compressor inlet p ,6 [MPa] air pressre on low pressre compressor otlet p 2 0 1,6 [MPa] air pressre on high pressre compressor otlet p p 0 10,0 [MPa] fel pressre before injectors T [] air temperatre on compressor inlet T [] exhast gases temperatre on inlet power trbine 4. Reslts of researches Fig. 6 presents reslts of experiment. Prameters are depend on time of mesre and setting angle of variable stator vanes. On Fig. 6 are presented those parameters which are the most sesitive on change of vanes setting angle. hange vanes setting from position to position cased increase air flow resistance by stator vanes. In conseqence of that sbatmospheric pressre on compressor inlet p 1 decreases (Fig. 6c). It cases pressre decrease in next parts of compressor and engine flow dct (rys. 6de). In this way redced air density flowing by compressor, for stable qantity of stream fle spllied to combstor, cases increase of compressors rotor speed. The most visible

6 is increase of low pressre compressor rotor speed (rys. 6a) cased by directly inflence on this compressor incorectly setting variable stator vanes. Range of change this parameter is above 2% vale of rotational speed for ndistrbed angle setting of vanes. a) low pressre rotor speed 9500 b) high pressre rotor speed n LP [min -1 ] _ n HP [min -1 ] _ sbatmospheric pressre on compressor inlet c) d) p 1 [MPa] 0,0009 0,0008 0,0007 p 21 [MPa] ,3 0,298 0,296 0,294 0,292 air pressre on low pressre otlet compressor 0,0006 e) air pressre on high pressre otlet compressor f) 0,85 0, exhast gas temperatre on power trbine inlet 800 p 2 [MPa] 0,8 T 42 [] _ 790 0, Fig. 6. hange of engine DR work parameters in fnction of variable inlet gide stator vanes setting angle: α W = - 4 o, α W = - 11 o, α W = - 18 o

7 Gasodynamical conection between low pressre compressor and high pressre compressor absorbs distrbances work of low pressre compressor which are transferred on high pressre compressor. Therefore range of change high pressre compressor rotor speed is lower than low pressre compressor. In this experimental it is belo% and it is in measring error of sensor range. hange of sbatmospheric pressre is above 5% ndistrbed vale of this parameter. hanges of low and high pressre compressor otlet presre are adecately above 1,3% and above 2,4% ndistrbed vale of angle setting α W = - 4 o. hanges of pressre and air mass flow intensity vales accompanied distrbing work of compressor, dring constant fel mas flow intensity in combstor, cased enrichment of fel mixtre. s a reslt of that, temperatre combstor otlet gases increases. In experiment was confirmed tendency changes of gases tempertare vales even thogh range of thoses changes is in measring error of sensor range. 5. onclsions On the base realised theoretical consideration and experimental researches we can draw a conclsion that incorrect operation of control system of inlet gide variable stator vanes or first stages stators vanes gas trbine engine compressor exerts negative inflence on compressor work and engine performances. Mlti-shaft constrction of gas trbine engine redces effects of incorrectly setting of variable vanes. Therefore compressors of three-shaft gas trbine engine do not reqire variable stators vanes as many stages as compressor of two-shaft engine with the same achivements. Preliminary researches confirme necessity for making inspection of correct operation of variable stator vanes system control. It makes possibility of elimination this factor from grop of factors informing abot technical state of engine which are identified dring diagnostic inspections. References [1] alicki, Wł., Szczeciński, St., Diagnozowanie lotniczych silników trbinowych, Wydawnictwo iblioteka Nakowa Instytt Lotnictwa, Warszawa [2] DŜygadło, Z., Napędy Lotnicze. Zespoły wirnikowe silników trbinowych, Wydawnictwa omnikacji i ączności, Warszawa [3] orczewski, Z., Identyfikacja procesów gazodynamicznych w zespole spręŝarkowym okrętowego trbinowego silnika spalinowego dla potrzeb diagnostyki, MW, Rozprawa habilitacyjna, Gdynia [4] orczewski, Z., Wirkowski, P., Modelling gasodynamic processes within trbine engines compressors eqipped with variable geometry of flow dct, IV International Scientifically- Technical onference Explo-Diesel & Gas Trbine 05, Gdańsk-Międzyzdroje-openhaga, Wyd. Politechnika Gdańska, str , Gdańsk [5] Marschal, D.J., Mir, D.E., Saravanamttoo, H.I.H., Health Monitoring of Variable Geometry Gas Trbines for the anadian Navy, The merican Society of Mechanical Engineers 345 E, 47 St., New York, N.Y