A Study on the Powering Performance of Multi-Axes Propulsion Ships with Wing Pods

Transcription

1 Second Inernaional Symposium on Marine Propulsors smp amburg Germany une A Sudy on he Powering Performance of Muli-Axes Propulsion Ships wih Wing Pods eungwon Seo Seokcheon Go Sangbong Lee and ungil Kwon Mariime Research Insiue yundai eavy Indusries Co. Ld Ulsan Korea (hwseo@hhi.co.kr) Iniial esign eparmen yundai eavy Indusries Co. Ld Ulsan Korea ABSTRACT The procedures of model ess and powering performance predicion for muli-axes propulsion ships wih wing Pods are sudied. In his sudy he subjec vessel has one convenional propeller in cener skeg posiion and wo pods in he wing side of he vessel. These wo independen propulsion sysems have he specific power disribuion raio and he corresponding revoluion raio of each propulsion sysem should be deermined from he model es. Wih his feaure as independen propulsion sysem of muli-axes ships a new model es procedure and exrapolaion mehod should be examined horoughly wih some modified ones of convenional single screw or win screw vessels. In he exrapolaion mehod for he full scale powering performance of muli-axes propulsion ships wih wing pods drag correcion quaniy of pods in model and full scale has a direc influence on he powering performance. For his open waer ess of wo differen geomery of pod were carried ou and evaluaed wih ITTC s recommended procedures. Keywords Ship powering Muli-axes Propulsion Ship Pods Propulsion es Exrapolaion mehod INTRUCTIN Convenional ships have one propeller-shaf sysem direcly conneced o main engine and win propellershaf sysem can also be adoped for redundan safey and oher reasons. For his ype of vessel model es procedure and exrapolaion mehods have a long hisory and are well esablished such as ITTC recommendaion (ITTC 98). Some special ypes of vessels reques muli-independen propulsion sysem arrangemen. For example general design of drillship has 6 hruser unis for ransi and P mode. And also cruiser liners have one fixed P and wo azimuhing pods for safey redundancy. For propulsion efficiency some RoPax ferry adop conraroaing pod (one convenional propeller forward and conra-roaing pod af configuraion). To find ou hese muli-independen propulsion vessels powering performance open waer es of each propulsion sysem resisance es and self-propulsion es would be carried ou as usual. Bu wih he feaure of muliindependen propulsion sysem several concerns could be issued. A normal operaion poin of propulsion power each propulsion sysem has opimal power disribuion. To evaluae powering performance by he model es as a whole proper revoluion raio of each sysem should be deermined corresponding o he power disribuion raio and his feaure makes self-propulsion es marix (for conra-roaing pods open waer es marix wih differen revoluion raio can be added). Generally powering performance can be deduced from effecive power (from resisance es) and propulsion efficiency (from self-propulsion es and open waer es) and loading of propulsion sysem direcly affecs propulsion efficiency. For win screw vessel we can easily assume each propulsion sysem has same propeller loading (ha is each sysem can bear one half of effecive power) so win sysem can be reaed as one. Bu for muli-independen propulsion ships how much propulsion load would be divided ino each sysem is quesioned and accordingly propulsion efficiency of each sysem can be affeced. In he presen sudy RoPax ferry wih one main propeller a cener fixed posiion and wo pods in wing side is he subjec vessel. For issues menioned above model es procedure and exrapolaion mehod are described and discussed. Addiionally pod drag correcion beween model scale and full scale has a direc influence on he powering performance and horoughly considered wih ITTC s recommendaion. SUBECT VESSEL AN MEL TEST SETUP. Subjec Vessel

2 As a subjec vessel passengers/6 lane meers RoPax ferry is seleced and i has one cener propeller and wo wing-side pods see Figure. Figure : Propulsion sysem of subjec vessel fore-end of dummy boa o simulae open waer condiion and propeller hrus/orque/revoluion and owing speed are measured. pen waer es of pod uni has more sophisicaed configuraion due o pod shell/sru arrangemen and addiional uni hrus measuremen. Currenly ITTC has a enaive guideline (lef side of Figure ) for he es seup and we made he es configuraion following ha guideline see Figure. Ship main pariculars and dils of propulsion sysem are described as Table. Normal operaion poin of propulsion sysem has power disribuion raio main cener propeller abou 6% and wo wing-side pods hruser abou % (each %) of oal propulsion power. Table : Main pariculars of ship and propulsion sysem Ship Main Pariculars Iem Ship Model Scale 8. LBP(m). 8.6 B(m).8.8 Td(m)..6 (design). ks.8 m/s Propulsion Sysem Iem Maincener Wing-side Pods iameer(m).. P/(mean).6. EAR..6 Power(kW) 6 Figure : Tes configuraion of pod uni open waer es In above es configuraion propeller hrus and orque are measured by he waer-igh dynamomeer a righ af of propeller and uni hrus (sum of propeller hrus and pod shell/sru resisance in acceleraed flow region by propeller roaing) is measured on he op side balance conneced o pod via inernal verical shaf. For he self-propulsion es a normal propeller dynamomeer is insalled for he main propeller hrus/orque measuremen and wo dynamomeer unis for wing-side pods are posiioned on he model ship deck wih fixed pich angle for pod propeller hrus/orque and uni hrus measuremen as shown in Figure. The yaw angle of pod uni is adjused via lower pod uni par roaion. Two wing-side pods are posiioned a x=-.8m (from AP) y=8.m (from cener 6.% of B/) and insalled wih verical angle (pich angle hereafer forward downward +) deg along wih flow angle from CF calculaion and wih horizonal angle (yaw angle hereafer forward ouside +) deg variaion o find opimum powering performance. For he geomerical design of main propeller and pod propeller he wake field informaion is used from CF calculaion of ship hull form.. Model Tes Seup and Scope Model es program is organized as resisance es open waer es of cener propeller/pod uni and self-propulsion es as usual. Resisance es is carried ou as a saus of bare hull wihou bilge keel and rudder as our insiue s sandard. In open waer es of cener propeller i is insalled a Figure : Tes configuraion of self-propulsion es

3 As our insiue s normal procedure each dynamomeer is calibraed wih our cerified sandard weighs before model es and he lineariy error of dynamomeer for propeller hrus/orque and uni hrus is wihin.% F.S. TEST RESULT AN EXTRAPLATIN MET. Tes Resul Propeller open waer ess for main propeller and pod uni are carried ou separaely. pen waer characerisics of main propeller are shown in Figure and heir full scale exrapolaion o full scale are according o ITTC s sandard procedure considering blade fricion correcion. he raio.9 (wing-side pods/cener) a design speed as seen in Figure. The power raio is calculaed in model scale using self-propulsion poin daa such as orque and revoluion of each propeller. I is assumed ha he power raio in model scale would be he same in full scale and be checked again afer exrapolaion....9 ModelK_T ModelK_Q ModelEa_ FullScaleK_T FullScaleK_Q FullScaleEa_.8. K T K Q Figure : pen waer characerisics of cener propeller For he open waer characerisics of pod uni uni hrus is used o define hrus coefficien and drag correcion of pod housing is applied along wih ITTC s enaive procedure as well as pods propeller blade fricion correcion. ils on he drag correcion of pod housing are presened in he nex secion and he resuls are shown in Figure ; he open waer characerisics are used o analyze self-propulsion es daa. Figure 6: pimal es of revoluion raio and roaion direcion of wing-side pods propeller Wih he direcion of he wing-side pod propeller roaion and he revoluion raio deermined as above he opimal yaw angle is also invesigaed in he view of oal power quaniy and he opimal value is deermined as degrees as shown Figure. This yaw angle has a good agreemen wih flow field by CF carried ou for he propeller design. Also during he yaw angle opimizaion es i is again confirmed ha he power raio is nearly consan along wih pre-deermined revoluion raio.... ModelK_T ModelK_Q ModelEa_ FullScaleK_T FullScaleK_Q FullScaleEa_...9 K T K Q Figure : pen waer characerisics of pod propeller In he preliminary self-propulsion es he revoluion raio of he propellers corresponding o he given power raio for he opimal operaion of he propulsion sysems is deermined wih inward and ouward direcion cases of wing-side pods. The opimal oal power and he revoluion raio is seled as ouward direcion of pods and Figure : pimal yaw angle es of wing-side Pods. Exrapolaion Mehod Full scale exrapolaion from self-propulsion model es daa is based on he ITTC 98 mehod. In his ITTC sandard procedure for he single vessel he propeller has a unique loading and also for he win screw vessel we can easily assume he wo propellers have same loading and would have same propulsion efficiency. owever he amoun of propeller loading of each propulsion sysem is no clear in he subjec vessel

4 because wo kinds of propulsion sysems in he subjec vessel are locaed a differen posiions and have differen sizes of propeller diameer; herefore how much loading o be burdened in each propulsion sysem can affec he propulsion efficiency direcly. By his feaure a convenional approach o rea wo differen sysems as a whole one would no proper so powering performance of each sysem will be analyzed separaely in presen sudy. Two kinds of loading disribuion mehod are applied o predic propulsion facors in he exrapolaion procedure. ne is based on he propeller hrus raio and anoher on he power raio because hese wo raios are differen. In he exrapolaion analysis he hrus deducion fracion and he coefficien of propeller hrus-loading in each propulsion sysem are assumed as below equaion () and (): ( R F ) * facor T () m d where Rm is oal model resisance Fd is skin fricion correcion force Tm is propeller hrus in model scale and facor is propeller hrus raio or power raio. Thrus raio and power raio are calculaed from he model hrus orque and revoluion of each propeller a self-propulsion poin. K T S ( CTS * facor ) ( )( wts ) () where K T is hrus coefficien is advance coefficien is propeller diameer C TS is oal resisance coefficien and w TS is full scale wake fracion. Tables and show he exrapolaion resuls according o he wo kinds of mehod above menioned which give a big difference in he propulsion facors especially in he hrus deducion fracion. In he case of power raio base exrapolaion he hrus deducion fracion of he wingside pods shows a much lower figure and his value of minus sign can be inerpreed such ha wing-side pods ac as booser no affecing flow field a he viciniy of hull. And also i leads o higher hull efficiency (η ) of wing propeller han ha of cener propeller ws.9 9 ws. Cener propeller. R.99 Table : Propulsion facors based on he hrus raio n he oher hand in he case of hrus raio base he hrus deducion fracion of cener and wing-side pods are idenical because of he usage of model resisance proporional o he propeller hrus raio. Wing propeller.88 R. m P[kW 9 P[kW 9 Table : Propulsion facors based on he power raio Even hough overall propulsion facors including final propulsion efficiency of each are differen beween wo mehods delivered power disribuion raio is prediced similarly; main cener propeller abou 6% and wo wingside pods abou % (each %) of oal propulsion power; and oal sum of each propulsion sysem is nearly same. P RAG CRRECTIN In he exrapolaion procedure of model es daa o full scale analysis of subjec vessel pod drag correcion quaniy o ge PW characerisics in full scale is more imporan issue and currenly ITTC suggess a enaive exrapolaion mehod (ITTC 8). Generally a relaive fricional drag componen of model scale is higher han full scale one so he uni hrus of model scale is relaively lower han full scale (because uni hrus is a sum of propeller hrus and resisance of Pod housing); herefore pod drag correcion quaniy should be added o model scale uni hrus. In our sudy drag correcion quaniy for wo differen shapes of Pod housing (body and sru) are invesigaed and calculaed wih ITTC recommended mehod and he corresponding raio of housing drag coefficiens (K) of model and full scale defined below is checked: () ws. ws. Cener propeller.9 R full mod el K hou sin g / Khousin g In ITTC s recommended procedure pod drag componen can be calculaed by semi-empirical formula wih geomerical principals presened in Table and in he equaions below. ere non-dimensional coefficien of uni hrus is: K TS K k BY k K TU Pod BY TM S.( / L) K Pod BY T _ Pr op / n S Body V / 6.99 Wing propeller PS. ( k R. ( / L) V K PS TU BY ( k )( C FM )( C.6.6 C FM FS P[kW 96 P[kW 6 ) C FS ) ()

5 A more diled formula is referenced wih ITTC s recommended procedure (ITTC 8). K TU Figure 8: Tes cases of wo differen pod housing shapes ur es cases have geomerical difference mainly L/ raio he second has more blun shape and principal dimension is described as Table. Table : Principal dimension of pod housing and form facor.... (model scale) ousing # ousing # L(mm). 8.8 (mm) L/.8.8 δ(hickness raio).8. S BY (m )/S (m ).6/../. k BY /k./..6/. Wih hese values pod drag correcion quaniies are calculaed considering acceleraed flow by propeller roaing along advance raio and ploed as shown in Figure 9. Geomery# byittc Recommendaion Geomery# byittc Recommendaion Geomery# bydirec raio(alpha=.9) Geomery# bydirec raio(alpha=.8) Advance Raio() Figure 9: Pod drag correcion quaniy of wo es cases In he pod uni open waer es he propeller hrus is measured as well as uni hrus so he drag of pod housing can be reaed as difference beween propeller/uni hrus. Then pod drag correcion quaniy can be calculaed wih pod drag from model es and he assumed raio of formula () and bes fi value o minimize he difference beween ITTC s recommendaion and direc raio (α) is.9 for pod housing # and.8 for housing # see Figure 9. From hese values a major componen of pod drag can be hough of as form drag relaed on pressure disribuion and an approximae value of.8 can be used as a simple correcion facor for pod drag in open waer characerisics exrapolaion. CNCLUSIN For he powering performance predicion for muli-axes propulsion ship wih wing pods owing ank model ess are carried ou and exrapolaion mehod based on he ITTC 98 is sudied. And he effec of pod shapes on he pod drag correcion is invesigaed based on he h ITTC recommendaion. From he model es wih cener propeller and wing-side pods propeller propeller revoluion raio corresponding o he power raio wing-side propeller roaion direcion and yaw angle are invesigaed and hese resuls will be helpful o prepare for he anoher model ess of similar ships. In full scale exrapolaion procedure wo kinds of propeller loading reamen are used for he separae powering performance analysis of he cener propeller and he wing-side propeller. From he exrapolaed resuls hrus deducion fracion is mainly affeced by propeller loading reamen among he propulsion facors. The delivered power disribuions of cener propeller and wing-side propeller are prediced similarly a boh cases. REFERENCES ABB. (8). Azipod Reference Lis. ABB y Marine Finland. ITTC. (). ʻPropeller pen Waer Tes. ITTC- Recommended Procedures and Guidelines. ITTC. (8). Propulsion Performance Podded Propulsion Tes and Exrapolaion. ITTC- Recommended Procedures and Guidelines. ITTC (8). Propulsion Tes. ITTC-Recommended Procedures and Guidelines. oerner S.F. (96). Fluid-ynamic rag. nd ed. oerner Fluid ynamics. oserhuis G. (6). Model-scale Podded Propellers for Mariime Research. Ph Thesis Eindhoven Universiy of Technology NL. Van Rijsbergen M. & olrop. (). Invesigaions on a pod open waer es se-up. MARIN Inernal Repor 6--T. Rolls-Royce. (). Technical Specificaion. Rolls- Royce.