THE COANDĂ VTOL-UAV AEROMECHANICAL ASPECTS

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1 HENRI COANDA GERMANY GENERAL M.R. STEFANIK AIR FORCE ACADEMY ARMED FORCES ACADEMY ROMANIA SLOVAK REPUBLIC INTERNATIONAL CONFERENCE of SCIENTIFIC PAPER AFASES 211 Brsov, My 211 THE COANDĂ VTOL-UAV AEROMECHANICAL ASPECTS George BĂLAN *, Sorin-Gbriel CONSTANTINESCU *, Bogdn CIOBANU ** Dunăre de Jos University of Glti *, Gheorghe Aschi Technicl University of Işi** Abstrct. The pper proposes new concept of flight, including in the first phse of the flight, verticl tke-off, using the propulsion forces from n on-bord rocket engine. The en-route phse of the flight, when moving horizontl, s the first prt of the pproch for lnding, re conducted more similr with rotry-wing flight. Also, the UAV sustenttion comes from his ero dynmicl shpe. Especilly designed to overcome the ir resistnce, the eril vehicle hs n pproprite design of the fuselge, which comply with Condă erodynmic profile. Lnding is ssisted with the help of the sme rocket engine, used for tke-off. Up tody, in our efforts to optimize the design of this VTOL-UAV, we mde first experimentl model t reduced scle. Moreover, erodynmic reserches hve been conducted on it, in wind tunnel, to enble optiml erodynmic design of this new type UAV. Brief, the proposed eril vehicle my be chrcterized s mixture between Condă UAV nd rection engine used only for verticl tke-off nd lnding phse. Keywords: rocket engine, Condă fuselge, rdil nozzle, flight vehicle. 1. INTRODUCTION The widespred eril vehicles - plnes to rech destintion point using the lift force tht occurs on the wing's erodynmic profile to the flow round them to high speed irflow. Flying n irplne consists of five distinct phses - the ccelertion device runwy, tkeoff, horizontl flight, lowering, brking on the runwy. Addiction current speed lift force provided in the direction of inesing development of vition nd flight ger shift plnes to jet propulsion. The result does not leve much to be expected - long runwys, huge irports, ctstrophic ccidents, rescue systems, fuel consumption is high becuse the irplne propeller clock functions t ll five phses of flight. Another irft s well spred is helicopter; the lift force is eted tht ll the erodynmic profile of the bldes flying in formtion 125 of eddy currents. Helicopter flight includes only three phses - tkeoff, horizontl flight, helicopter descent. Inese flight speed is limited by resistnce propeller bldes t high speeds, motoriztion is excluded so rective nd propellers used. Fuel consumption is much higher compred with the plne, becuse the helicopter propeller works extensively in ll the phses of flight, there re more ctstrophic ccidents. There re no rescue tool systems. A new flight system used for trvel erospce re spce ships Columbi (USA) nd Burn (Russi), for multiple flights, includes four min phses: STOVL (Short Tke-Off, Verticl Lnding) with rocket luncher, bllistic flight pth, erodynmic brke, lnding on runwy by erodynmic brking (ship "Columbi") or by rection engines (ship Burn ). The dvntge of the flight system, clled "Shuttle" mens the use of rocket pow- 1/6

2 ered propellers, with the period of ctive opertion of the flight pth only, use of ir resistnce for the lnding, existing rescue systems. As disdvntge we cn consider horizontl lnding on runwy long nd the impossibility of soft verticl lnding. Nowdys there is wide rnge of unmnned irft tht rely on n irplne or on helicopter scheme. These devices cn provide trcking moving objects, environmentl monitoring, fire nd flood monitoring, trcking militry personnel nd groups of people, including visul trcking suspects nd finding missing persons. Also the use of these unmnned devices requires fvorble wether conditions similr to those required for flying irplnes or helicopters (wind speed, fog, visibility nd lightning). The drwbck of unmnned devices is impossibility to rech in the fst trcking speed nd hng in the low speed trcking. All existing devices cnnot be lunched from underwter position; it cnnot move in wter nd lnd on wter. To overcome the drwbcks outlined bove re vilble to interested reserchers for monitoring of ecosystem vehicle tht stisfies its sustenttion nd propulsion through n lterntive bsed on the Condă effect nd rection propulsion. 2. UNMANNED COANDĂ AIRCRAFT WITH REACTIVE PROPULSION Below (Fig. 1) is schemtic digrm unmnned irft min propulsion Condă rective, which contins: Condă fuselge (1), gs genertor (4) which with rdil nozzle (2) forms the centrl rocket engine nd four side rocket engines (3). Fig. 1. Min scheme unmnned irft powered Condă rective: 1 - Condă fuselge, 2 - rdil nozzle, 3 - side rocket propellnt, 4 - centrl rocket propellnt; I - Centrl rocket thruster jet; II - lterl jet thruster rocket Centrl rocket engine (4) produces gs tht by nozzle rdil (2) gets round Condă fuselge, cusing the gs strem I. Becuse the supersonic Condă jet I, etes lyer tht significntly reduces the erodynmic resistnce of the fuselge. Supersonic jets II (Fig. 1) of the side rocket thrusters provide verticl tke-off nd guiding device on ctive flight pth I (Fig.2). All these engines side deeses to zero speed lnding providing soft lnding of the lst phse of flight (IV, fig. 2). The min difference in the dynmics of the device Condă jet flight unlike devices bsed on n irplne or helicopter is tht movement in the horizontl direction occurs fter inertil trjectory similr to bllistic missiles. The min purpose of the flight itself is done, horizontl displcement engines not strted but to hng the device from the point of mximum ltitude (3, fig.2) the free fll trjectory III, which my be with different trjectory from the bllistic one. 126

3 Fig. 2. Flight phses Condă device with rective propulsion: 1 - pltform off; 2-point off the engine side; 4 - the point of mximum ltitude; 5-lnding pltform; 6-lnding on wter; 7 - underwter home; I - ctive pth; II, III - pssive pth; IV pth brking. Condă jet device (Fig.1) is verticl lunch nd ll engines strts or underwter position 7(fig. 2). Active pth of the device is held up to the point 2, then engine side 3, stops. On pssive pth, device brkes due to erodynmic shpe nd the Condă effect. Reching the point of lnding 4, side engines re strted providing soft lnding on the pltform device 5, or on wter surfce 6 (fig. 2). 3. THE EXPERIMENTAL DEVICE COANDĂ JET Experimentl reserch conducted by most reserchers [1,2 ] show tht with inesing flow rte of rdil nozzle, lift force developed by Condă fuselge inesed. The Condă device with rdil convergent nozzle is shown in Fig. 3: Fig.3. The Condă device with convergent nozzle: 1-feeder; 2- Condă fuselge; 3-convergent nozzle; 4-fixing nut; I-ir intke; II-jet ttchment; D t, H- Condă fuselge dimeter nd height; R-rdius of curvture of the Condă fuselge; D -rdil nozzles dimeter; δ- rdil slot nozzle The feeder 1 (fig. 3) is centrl piece where the Condă profile is fixed 2, with nut 4. Condă fuselge rdius R= 7 mm is equl to its height H. 3 is sewed on top of bse llowing slot nozzle size chnges δ = mm. position fix 3 is mde with two dimetriclly locted mounting sews. Compressed ir tmp down by center chnnel bse 1, nd is trgeted by the oss holes of the bse in rdil convergent nozzle 3, which ccelertes nd flows on being ttched to the exterior profile of the pltes 2, eting lift force in the xil direction. Velocity converging gs nozzle rnges ccordingly the supply pressure nd the flow ccordingly the slot nd fixed dimeter nozzle pressure. Depending on the flow of gs in the convergent nozzle outlet section, being tht subsonic (Mch number M <1) or trnsonic (Mch number M = 1). In the subsonic regime speed gs flow nozzle is determined by pplying Sint-Vennt formul [1]: k 1 2k P P k t υ = 1, m / s k 1 P (1) ρ where: p =p + p tm - bsolute pressure supply, P p- mnometer pressure supply 127

p tm - tmospheric pressure p p =, kg/m 3 - density ir supply R T R=287 J/(kg K) - ir gs constnt T=273.

4 p tm - tmospheric pressure p p =, kg/m 3 - density ir supply R T R=287 J/(kg K) - ir gs constnt T= t,K - ir temperture t o o C - ir temperture Air mss flow rte using the Sint-Vennt formul for subsonic gs flow through holes nd nozzles will be: m = ρ υ S, kg/s (2) where: S= S = π D δ, sectionl re of exit, D, m rdil nozzles dimeter; δ, m rdil nozzles slot. If the totl gs pressure p is higher thn pressure of the surroundings p t in which flow k 2 k 1 occurs = 1.72 time, in the k + 1 convergent nozzle exit section trnsonic flow regime is instlled with Mch number M = 1,with iticl thermodynmic prmeters, then ir mss flow is determined by the formul: Experimentl tests conducted in the Lbortory of Aerodynmics the Deprtment of Fluid Mechnics, Hydrulic nd Pneumtic Mchines nd Drives, Technicl University "Gheorghe Aschi" from Isi, imed t mesuring the sttic pressure on the Condă device experimentl prototype of scle chieved. Since the cpcity of the lbortory compressed ir supply is up to 1.5 m 3 /min, experimentl tests were performed for flow of 25 l/sec being tested severl configurtions of exhust ir nozzles (nozzles 7, 9, 13, 15 nd 17 mm). Airflow mesurement is mde with diphrgm flow meter connected to differentil mnometer mesuring rnge 15 mm H 2 O. The fourteen sttic pressure plugs re locted from 1 to 1 mm, from the neighborhood feeder nd ending t the bottom of the Condă fuselge of experimentl prototype, smll scle developed (Fig. 4) Pressure plugs. m = ρ S, kg/s (3) where: ρ nd re the iticl prmeters determine by the initil prmeters (P, ρ, T ) nd dibtic exponent (k) of gs. Criticl velocity is given by: P 2k υ = =, m/s (4) ρ k + 1 Criticl ir density: 1 2 k 1 ρ = ρ,m/s (5) k + 1 Construction model provided 5 different dimeters converging nozzles, with dimensions of respectively D = 7, 9, 13, 15 nd 17 mm, with D t = 28 mm dimeter Condă fuselge tht, consecutively, ensure chnges rtio D /D t =.25;.32;.46;.54 nd RESULTS AND DISCUSSION Fig. 4. Pressure plugs on the Condă fuselge The vlue of pressure drop mesured on ctive element flow meter with diphrgm ws Δp=1334 mm H 2 O which corresponds to rte Q= 25 l/s. In terms of fluid flow ttched to the min body of experimentl prototype smll-scle developed, hs been noticed tht lrge dimeter discs (D =15 mm nd D =17 mm) ensures conditions for the seprtion of fluid flow in the lower housing, while for smller dimeter discs seprtion is chieved in the mximum curvture of the cse. In Fig. 5 is presented the sttic pressure distribution compred for the six nozzle dimeters considered, while three slot nozzle size, δ =1.5; 2.5 nd 5.5 mm. 128

5 Rz, N D/Dt Fig.6. Aerodynmic lift force depending on the dimeter rtio D / D t (slot nozzle δ=2.5 mm) With inesing flow velocity of the rdil jet, lso ineses the erodynmic lift force (Fig.7). Rz, N Fig. 5. Vrition of sttic pressure on genertor of Condă fuselge There is better behvior in terms of sttic pressure distribution, to nozzles with smller dimeters to lrge dimeters D = 13, 15 nd 17 mm. Rdil flow seprtion occurs on the surfce of Condă fuselge. Below Figures 6 nd 7 re grphs tht dependent lift forces Rz re shown determined by processing dt [2], depending on nozzle dimeter rdil D report to Condă fuselge dimeter D t. As shown in Figure 6, there is n optiml vlue for D /D t where erodynmic lift force mximum nd nmely is..2 Fig.7. Aerodynmic lift force R z depending on ir velocity υ to the exit of rdil nozzle Dt processing method of lest squres llowed pproximtion equtions for the dependence of erodynmic lift force depending on the dimeter rtio D /D t nd in speed ccording to rdil jet flow: R Z 3 2 D D = Dt Dt D Dt R z = υ υ υ+.52 (6) (7) Formuls 6 nd 7 llow choosing the rdil nozzle geometricl prmeters: D - rdil nozzles dimeter; δ - rdil nozzles slit. 129

6 In Tb.1 nd Tb.2, re presented the experimentl dt collected from the dependence of erodynmic lift force of dimeter rtio D /D t nd speed υ. Tb.1 Experimentl dt for the ir velocity dimeter slot Dimeter rtio Velocity D δ D / D υ t [mm] [mm] [m/s] Tb.2 Experimentl dt for the lift force dimeter D [mm] slot δ [mm] Dimeter rtio D / D t Lift force R z [N] CONCLUSIONS It ws proposed new concept of flight, including in the first phse of the flight, verticl tke-off, using the propulsion forces from n on-bord rocket engine. An eril vehicle chrcterized s mixture between Condă UAV nd rection engine used only for verticl tke-off nd lnding phse it ws desibed. For optimizing the design of this VTOL-UAV, it ws mde first experimentl model t smll scle. The erodynmic reserches hve been conducted on it, in wind tunnel. The results of erodynmic reserches llowed determintion of erodynmic lift force depending on rdil nozzles dimeter, its slot nd flow velocity t nozzles exit. dimeter rtio ws estblished to the Condă fuselge dimeter, where is the mximum erodynmic lift force. The numericl pproximtion nlyticl reltions were obtined to clculte the erodynmic lift force depending on the rdil speed jet nd geometric prmeters of the irft. REFERENCES 1. Băln G., Aerozodinmică, Ed. Tehnic-INFO, Chişinău, Todicescu Al. Mecnic fluidelor şi mşini pneumtice, E.D.P, Bucureşti,

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