Available online at ScienceDirect. Procedia Engineering 113 (2015 )

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1 Available olie at ScieceDirect rocedia Egieerig 3 (205 ) Iteratioal Coferece o Oil ad Gas Egieerig, OGE-205 The twi spool efficiecy cotrol Michuri A.I. a *, Avtoomova I.V. a a Bauma Moscow State Techical Uiversity, 5 Baumaskaya Str. 2-ya, Moscow, 05005, Russia Federatio Abstract The developmet ad implemetatio of the eergy-savig techologies is oe of the challeges facig the domestic idustrial eterprises; whe it comes to the compressor equipmet, a large-scale implemetatio of the variable capacity screw compressors ito the maufacturig processes has become the first proper step cocerig the solutio of eergy-savig questios. Nowadays the spool efficiecy cotrolled oil-flooded screw compressors are widely used for the fuel gas supply ito the gas turbie uit (GTU). This paper presets the existig types of the spool cofiguratios whereby the screw compressors cotrol is realized as well as the ew spool desig costructio that allows to implemet the gas bypass from the higher pressure paired chamber to the low pressure oe is offered. Gas is ot bypassed ito the suctio chamber, that i tur saves the supplied power. 205 The Authors. ublished by by Elsevier Elsevier Ltd. Ltd. This is a ope access article uder the CC BY-NC-ND licese ( eer-review uder resposibility of the Omsk State Techical Uiversity. eer-review uder resposibility of the Omsk State Techical Uiversity Keywords: oil-flooded screw compressor; spool; power; bypass; cotrol. Itroductio Nowadays a umber of screw compressor efficiecy comtrol methods are kow: the compressor start ad stop; the shift to the idle stroke; the compressed gas bypass from the discharge lie ito the suctio chamber or compressed gas relief to flare; the gas throttlig i the suctio brach; the compressor drive shaft rotatioal speed variatio; gas bypass from the workig chambers ito the suctio chamber through the valves; the chambers space chage by meas of the spools [,2]. I the atural gas idustry, where screw compressors are used for the fuel gas supply ito the gas turbie uits, the twi spools efficiecy cotrol is ecoomically feasible regulatio method. Accordig to the above metioed method uder the full compressor load, the spools appressed, that is the primary spool is i the left ed positio, while the secodary spool is i the right ed oe (Fig., positio A), ad full * Correspodig author. Tel.: address: sotka-sotka@mail.ru The Authors. ublished by Elsevier Ltd. This is a ope access article uder the CC BY-NC-ND licese ( eer-review uder resposibility of the Omsk State Techical Uiversity doi:0.06/j.proeg

2 302 A.I. Michuri ad I.V. Avtoomova / rocedia Egieerig 3 ( 205 ) operatig screw legth is equal to +2, here ad 2 correspodigly are the primary ad secodary spools legth. ositio A ositio B ositio C Fig.. The twi spool oil-flooded screw compressor: - compressor casig, 2 - screw, 3 - primary spool, 4 - secodary spool. At the pressure ad/or temperature chagig i the suctio brach, the compressor efficiecy varies that at the gas supply ito the GTU is uacceptable, ad cosequetly it results i the efficiecy cotrol ecessity. I the upper rage of the efficiecy cotrol (the efficiecy varies from the maximum value V e max to 0,6 V e max ) the spools keeps the iitial positios (Fig., positio A), while the efficiecy cotrol is carried out via the surplus gas bypass from discharge to suctio. At the further efficiecy loss, the secodary spool is displaced to the left ed positio (Fig., positio B). I these circumstaces the maximum compressor efficiecy V e max is determied by the primary spool legth l, while the efficiecy is regulated by the primary spool smooth displacemet to the right side (Fig., positio C). Whe the primary spool is displaced, both efficiecy ad geometric compressor ratio ca be varied. The efficiecy cotrol by gas bypass from discharge to suctio which is carried out i the upper rage of the efficiecy cotrol is the most uecoomic way of cotrol. Therefore the efficiecy cotrol is proposed to be carried out by gas bypass from the high pressure paired chamber to the precedig low pressure oe. Moreover the low pressure paired chamber should ot be coected with the compressor suctio chamber. I this regard a ew desig cocept of the secodary spool was developed. 2. The proposed secodary spool structure The secodary spool (Fig.2), hollow cylider with bypass holes 2 carries out gas bypass from the higher pressure compressor paired chambers to the low pressure oes. Compressor casig 4 (Fig.2) has bypass holes 3 (Fig.2) which diameter is equal to the bypass holes diameter i the secodary spool. Fig. 2. The ew spool desig costructio.

3 A.I. Michuri ad I.V. Avtoomova / rocedia Egieerig 3 ( 205 ) The gas cosumptio cotrol betwee the compressor paired chamber ad the iside secodary spool chamber is carried out by the secodary spool turig. It should be oted that gas is bypassed from the higher pressure paired chamber to the spool chamber ad the to the low pressure paired chamber. Gas is ot bypassed to the suctio chamber. Whe calculatig the amout of bypassed gas at the first stage, the gas parameters i the paired chambers which are ot coected to each other are idetified by the equatio: T T * e suc ( suc ) l( suc ) suc suc k () where T ad T suc are the temperatures i the actual paired chamber ad i the suctio chamber accordigly, k is the compressio polytrope coefficiet, suc is the actual compressio cell pressure. Gas parameters i the paired chambers coected to each other were determied by the equatio. I this case it is cosidered that there is o overflow: trough the gap alog the cotact lie, radial gaps ad triagular gap. The mixture temperature is calculated accordig to the formula: T mix T* T2( W* suc W2* suc2) T * * W T * * W 2 suc suc2 2 (2) where W, W 2 are the volumes of the first ad the secod paired chambers accordigly, T, T 2 are the temperatures of the first ad the secod paired chambers accordigly, The mixture pressure is estimated by solvig the equatio usig umerical procedure: d k dv RTG p p TGy dt V dt (3) where p is the pressure. The volumetric gas cosumptio ca be calculated by the suctio coditios usig the formula: 2 k 2k k k 2 2 Vo f k RT (4) The chambers described volume is determied by the formula: V h V * T * T * h suc suc suc (5) where T is the temperature i the -th compressio cell, suc is the suctio pressure i the -th cell. Idicated power cosumed for compressio i chambers ca be calculated as follows: NI Vh * suc* * (6)

4 304 A.I. Michuri ad I.V. Avtoomova / rocedia Egieerig 3 ( 205 ) NII III ( mix suc2)* Vh 2 ( mix suc2)*( Vh 3VG 3) (7) 4 NIV ( Vh 4 VG 4)* mix * * (8) 4 V h5 G4 mix 4 h5 G5 н mix 4 N K*(( V V )*( * * * ) ( V V )*( * ) (9) Where is the iteral compressio rate of the -th cell, V G is the overflowig gas volumetric cosumptio through the holes related by the -th cell coditios. The total cosumed idicated power is calculated accordig to the formula: N N N N N I II III IV V (0) To fid out the power cosumed by the compressor, the aical efficiecy is accepted, ad the power cosumed for the aical losses ca be determied by the followig formula: N N * () While the total power cosumed by the compressor is determied usig the formula: N N N (2) The varied hole diameter values calculatio was carried out ad the fidigs are preseted i Table. Table. The calculatio fidigs. The diameter value The compressor efficiecy, m3/s The total power, cosumed by the compressor, W No bypass (the spool is closed) The hole diameter 5mm The hole diameter 3mm The hole diameter 2mm 0, , , , The calculatio showed that at 3 mm hole opeig, the efficiecy is decreased for 37%, while savig of eergy correspods to 20%; at 2 mm hole opeig, the efficiecy is decreased for 2%, while savig of eergy correspods to 5%.

5 A.I. Michuri ad I.V. Avtoomova / rocedia Egieerig 3 ( 205 ) Refereces [] A.A. Nuzhdi, Vasilyev V.I. Regulirovaiye proizvoditelosti vitovyh holodilyh kompressorov. M: CINTIHIMNEFTEMASH, s.(I Russia) [2] G.A. Bodareko, Zharkov.E. Vitovyie kompressory v sistemah obespecheiya szhatym vozduhom. - Sumy: izd-vo Sum GU, s. (I Russia)