INFLUENCE OF THE INCORRECT SETTINGS OF AXIAL COMPRESSOR INLET VARIABLE STATOR VANES ON GAS TURBINE ENGINE WORK PARAMETERS

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1 Jornal of KONES Powertrain and Transport, Vol. 19, No INFLUENCE OF THE INCORRECT SETTINGS OF AXIAL COMPRESSOR INLET VARIABLE STATOR VANES ON GAS TURBINE ENGINE WORK PARAMETERS Pawe Wirkowski Polish Naval Academy Department of Mechanical and Electrical Engineering Smidowicza Street 69, Gdynia, Poland tel.: , fax: p.wirkowski@amw.gdynia.pl Abstract The paper deals with the problem of inflence of changes variable stator vanes axial compressor settings of gas trbine engine on work parameters of compressor and engine. Incorrect operation of change setting system of variable vanes cold make nstable work of compressor and engine. This paper presents theoretical analysis of sitation described above and reslts of own research done on real engine. When in the compressor constrction there is assembled system of setting change of variable stator vanes its task is to make optimal cooperation engine nits dring the permanent improvement of compressor characteristic. Pertrbations in the operation of this system cold case changes in work of compressor and engine similarly as in the case of changes cased by changes of rotational speed or pollted interblades dcts of compressor. The prpose of investigations, which was carried ot on real engine was determination inflence of incorrect operation of axial compressor inlet gide variable stator vanes control system of gas trbine engine on compressor and engine work parameters. The object of research is type DR 77 marine gas trbine engine, which is a part of power transmission system of war ship. In compressor constrction configration of this engine there are sed inlet gide stator vanes which make possibilities to change the setting angle incidance (change of compressor flow dct geometry) in depend on engine load. On the base of reslts of experiment there were determined the mathematical eqations modelling the changes of particlar engine work parameters in the fnction of variable inlet gide stator vanes setting angle. Keywords: gas trbine, axial compressor, variable stator vanes 1. Introdction When in the compressor constrction is assembled system of setting change of variable stator vanes its task is to make optimal cooperation engine nits dring the permanent improvement of compressor characteristic. Pertrbations in the operation of this system cold case changes in work of compressor and engine similarly as in the case of changes cased by changes of rotational speed or pollted interblades dcts of compressor. Compressor stage nitary work on radis is defined on the base of eqation of anglar momentm and it has form c c c w lst r 1, (1) where: anglar velocity, tangential velocity, r rotor radis, c 1, c circmferential components of air stream absolte velocity on the inlet and otlet rotor blades on radis r, c, w air stream whirl in the rotor.

2 P. Wirkowski That work is constant on whole depth of rotor blade. The sm of works is the nitary work of stage. Involved change of variable stator vanes angle setting at a constant level rotational velocity (constant ) cased change of air stream inlet angle in rotor vane 1 (Fig. 1). It cased change of axial component of air stream absolte velocity on inlet c 1a what is eqivalent with the change of air mass flow m and change of air stream whirl w in rotor. It inflences on efficiency and work of stage. The prpose of investigations, which was carried ot on real engine was determination of inflence of incorrect operation of axial compressor inlet gide variable stator vanes control system of gas trbine engine on compressor and engine work parameters. Compressor characteristic is a relationship between compression ratio C, compressor efficiency C and air flow mass m and compressor rotational velocity n. It makes possible to determine the best condition of compressor and another engine nits mating. The characteristic is sed to select optimal conditions of air flow reglation and assessment of operational factors on compressor parameters. Therefore compressor shold be so controlled in operational range of rotational velocity that the compressor and engine mating line has a stock of stable work. The main rle of compressor control dring the change of their rotational velocity or flow intensity is to keep p the stream inlet angles i vale 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. This soltion makes it possible to change of air stream inlet angle on rotor blades of compressor stages by change of stator vanes setting angles dring the change of compressor rotational velocity. Fig. 1 illstrates the rle of reglation of variable stator vanes. For average vales of operational range of compressor rotor speed is sitation in Fig. 1b speed vales and directions with sbscript nmber 1. In this sitation is intermediate angle setting of stator vanes. Air 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 velocity c 1a, it is necessary to redce the stream otlet angle of variable stator vanes 1 (Fig. 1a). The angle redction range shold allow keeping the same vale of stream inlet angle on rotor blades. Analogical sitation takes place dring the 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. 1c. Application in gas trbine engine constrction of control system of flow dcts geometry has a bearing on a rn of nstable processes.. Object of research The object of research is type DR 77 marine gas trbine engine (Fig. ), which is a part of power transmission system of a warship. It is three-shaft engine with can-ring-type combstor chamber and reversible power trbine. In compressor constrction configration of this engine there are sed inlet gide stator vanes which make possibilities to change the setting angle incidance (change of compressor flow dct geometry) in dependance 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. 3 is presented block diagram of flow control signal of variable stator vanes system. Compressed air from the last stage of high pressre compressor is spplied to working space of control actator by cleaning and cooling block. Compressed 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 1 (Fig. 1). In cleaning and cooling block are made holes. Dring research air stream was bleeded by the holes and less air was spplied to the actator. It cased change of setting angle VIGV of variable stator vanes. In conseqence of that change flow dct geometry was changed. 484

3 Inflence of the Incorrect Settings of Axial Compressor Inlet Variable Stator Vanes on Gas Trbine Engine Work Parameters a) b) c) d)... k w 1 1 i=0 a 1 1 a 1 w 1 k w 1 c 1a w 1 c 1a c 1a w 1 w w 1 w 1 c 1a w Fig. 1. Essence of control of compressor s axial stage by changing the setting angle of stator vanes ring at changeable air flow velocity; a) decreased axial velocity, b) analytical axial velocity, c) increased axial velocity, d) schema of flow rond of axial compressor rotor blades dring constant rotor speed and constant air stream inlet angles; k variable stator vanes ring, w rotor vanes ring Fig.. Type DR 77 marine gas trbine engine CO HPC CLEANING AND COOLING BLOCK BLEED CONTROL ACTUATOR VIGV MOVING RING p 0, T 0, 0 LPC 1 z Fig. 3. Block diagram of stator vanes change setting mechanism 485

4 P. Wirkowski The experiment was carried ot on an engine load 0,5P nom with taking into consideration atmospheric conditions. For this load setting angle of variable vanes has vale VIGV = - 4 o. Dring change engine load in the whole range from idle to fll load setting angle VIGV of variable vanes changes in range from -18 o to +18 o. Dring experiment a few parameters of engine work was measred and registered. It was made for three different setting angle VIGV of variable vanes: A- VIGV = -4 o, B- VIGV = -11 o, C- VIGV = -18 o. Tab. 1 presents measred and registered parameters. Tab. 1. Parameters of engine DR77 work measred dring research Parameter Measrement range Unit Parameter name n LPC [rpm] low pressre rotor speed n HPC [rpm] high pressre rotor speed n PT [rpm] power trbine rotor speed p [MPa] sbatmospheric pressre on compressor inlet p [MPa] air pressre on low pressre compressor otlet p [MPa] air pressre on high pressre compressor otlet p p [MPa] fel pressre before injectors T [K] air temperatre on compressor inlet T [K] exhast gases temperatre on inlet power trbine 3. Reslts of research Change angle vanes setting from position A to position C cased the increase of air flow resistance by stator vanes. In conseqence of that sbatmospheric pressre on the compressor inlet p 1 decreases. It cases pressre decrease in next parts of compressor and engine flow dct. 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 noticeable is increase of low pressre compressor rotor speed cased by directly inflence on this compressor incorrectly setting variable stator vanes. Gasodynamical connection between the low pressre compressor and the 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 experiment it is below 1% and it is in measring error of sensor range. Change of sbatmospheric pressre is above 5% ndistrbed vale of this parameter. Changes of low and high pressre compressor otlet presre are adeqately above 1.3% and above.4% ndistrbed vale of angle setting VIGV = - 4 o. Changes of pressre and air mass flow intensity vales accompanied distrbed work of compressor, dring constant fel mass flow intensity in combstor, cased enrichment of fel mixtre. As a reslt of that, temperatre combstor otlet gases increases. In experiment was confirmed the tendency changes of gases tempertare vales even thogh the range of those changes is in measring error of sensor range. On the base of reslts of experiment there were determined the mathematical eqations modelling the changes of particlar engine work parameters in the fnction of variable inlet gide stator vanes setting angle VIGV : n , () n LPC VIGV VIGV HPC VIGV 1.14 VIGV 6 6 p1 10 VIGV 10 VIGV 16 p.1 10 VIGV VIGV 16 p 10 VIGV VIGV T VIGV VIGV 1598, (3) , (4).9814, (5) , (6) (7) 486

5 Inflence of the Incorrect Settings of Axial Compressor Inlet Variable Stator Vanes on Gas Trbine Engine Work Parameters Figre 4 presents reslts of mathematical modelling of engine work parameters. Modelling was cary ot an state engine load what was eqivalent nchangable fel mass flow. In this case range of change of variable inlet gide stator vanes angle setting VIGV was widen from -18 o to +18 o. Research in range VIGV from -4 o to +18 o were not possilble to realize on real engine. It is cased by technical restrictions on the engine. Fig. 4. Change of vales of engine work parameters in fnction of variable inlet gide stator vanes setting angle gotten dring mathematical simlation 487

6 P. Wirkowski Figre 5 presents reslts of mathematical modelling of engine work parameters in relative vales. Parameters obtained dring the tests have been referenced to the vales in the ndistorted work of engine. This work is characterized by 50 % nominal engine load and variable inlet gide vanes angle setting VIGV = - 4 o. 4. Conclsions Fig. 5. Reslts of mathematical modeling of engine work parameters in relative vales Change of vales of variable inlet gide stator vanes setting angle VIGV from -4 o to +18 o cased the increase of stream otlet angle of variable stator gide vanes 1 (Fig. 1). It decreases air flow drag on low pressre compressor inlet that cased decrease of sbatmospheric pressre. Dring keeping the constant engine load (constant fel mass flow) absolte axial component velocity c 1a increases. It exerts an inflence on air mass flow m increase. Simltaneosly the absolte axial component velocity c 1a increase cased decrease of air stream whirl in rotor w. In conseqence of that low pressre compressor rotor speed increases (Fig. 4a). In connection with decrease of sbatmospheric pressre the increase of air pressre on low pressre otlet compressor is cased (Fig. 4d). In spite of the slight decrease of high pressre compressor rotor speed the increase of air pressre on low pressre otlet compressor involves the increases of air pressre on high pressre otlet compressor (Fig. 4e). This slight decrease of high pressre compressor rotor speed cased increase of gases flow drag in the next gas trbine engine nits for the combstor. The effect of above is a slight increase of exhast gas temperatre on power trbine inlet. 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 achievements. Preliminary research confirms the necessity of inspection the 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 the diagnostic inspections. 488

7 Inflence of the Incorrect Settings of Axial Compressor Inlet Variable Stator Vanes on Gas Trbine Engine Work Parameters References [1] Charchalis, A., Diagnostics of marine gas trbine engines (in Polish), Pblished by Polish Naval Academy, Gdynia [] D ygad o, Z. et al., Rotor nits of gas trbine engines (in Polish), Transport and Telecommnication Pblishing Hose (WKi ), Warszawa 198. [3] Korczewski, Z., Wirkowski, P., Modelling gasodynamic processes within trbine engines compressors eqipped with variable geometry of flow dct, IV International Scientifically- Technical Conference Explo-Diesel & Gas Trbine, Wydawnictwo Politechniki Gda skiej, pp. 7-36, Gda sk 005. [4] Marschal, D. J., Mir, D. E., Saravanamttoo, H. I. H., Health Monitoring of Variable Geometry Gas Trbines for the Canadian Navy, The American Society of Mechanical Engineers 345 E, 47 St., New York, N.Y [5] Wirkowski, P., Modelling the characteristics of axial compressor of variable flow passage geometry, working in the gas trbine engine system, Polish Maritime Research, No 3/007, Pblished by Gda sk University of Technology, pp. 7-3, Gda sk 007. [6] Wirkowski, P., Simlation of changes of gas trbine engine work parameters eqipped with variable inlet stator vanes axial compressor, 1 TH International Conference Compter systems aided science, indstry and transport, TRANSCOMP, Pblished by Radom University of Technology, , Radom 008. [7] Wirkowski, P., Inflence of axial compressor flow passage geometry changes on gas trbine engine work parameters, VI International Scientifically-Technical Conference POLISH CIMAC Explo-Diesel & Gas Trbine 09, Pblished by Gda sk University of Technology, Vol., Gda sk 009. Parameters, abbreviations and sbscripts 1 air stream otlet angle with stator vanes, VIGV setting angle of variable inlet gide vanes, 1, air stream inlet and otlet angles in rotor vanes, c 1a axial component of air stream absolte speed on rotor blades inlet, c 1, c circmferential components of air stream absolte velocity on the inlet and otlet rotor blades, CO combstor, HPC high pressre compressor, HPT high pressre trbine, C compressor efficiency, I air stream inlet angle on rotor blades, LPC low pressre compressor, LPT low pressre trbine, variable stator vane, m air mass flow, N compressor rotor speed, anglar velocity, p fel fel pressre, P nom nominal engine power, PT power trbine, C compression ratio, U circmferential speed, W 1, w air stream relative speed on inlet and otlet rotor blades, VIGV variable inlet gide vanes, c, w air stream whirl in the rotor, Z nmber of inlet gide stator vanes. 489