ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2021, Vol. 42 ›› Issue (3): 624037-624037.doi: 10.7527/S1000-6893.2020.24037
• Special Topic of Electric Aircraft • Previous Articles Next Articles
HUANG Jun1,2
Received:
2020-03-30
Revised:
2020-04-10
Published:
2020-04-30
CLC Number:
HUANG Jun. Survey on design technology of distributed electric propulsion aircraft[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(3): 624037-624037.
[1] KUMAR T, MOHSIN R, GHAFIR M F A, et al. Concerns over Use of Leaded Aviation Gasoline (AVGAS) Fuel[J]. Chemical Engineering Transactions, 2018, 63:181-186. [2] WOLFE P J, GIANG A, ASHOK A, et al. Costs of IQ loss from leaded aviation gasoline emissions[J]. Environmental Science & Technology, 2016, 50(17):9026-9033. [3] FAROKHI S. Future propulsion systems and energy sources in sustainable aviation[M]. New Jersey:John Wiley & Son, Inc., 2020:384-385. [4] MOORE M D. The third wave of aeronautics:On-demand mobility[J]. Journal of Aerospace, 2006, 115(1):713-722. [5] MOORE M D, GOODRICH K, VIKEN J, et al. High-speed mobility through on-demand aviation:AIAA-2013-4373[R]. Reston:AIAA, 2013. [6] BORER N K, MOORE M D, TURNBULL A R. Trade-space exploration of distributed propulsors for advanced on-demand mobility concepts:AIAA-2014-2850[R]. Reston:AIAA, 2014. [7] PATTERSON M D, GERMAN B J, MOORE M D. Performance analysis and design of on-demand electric aircraft concepts:AIAA-2012-5474[R]. Reston:AIAA, 2012. [8] MOORE M D, FREDERICKS B. Misconceptions of electric propulsion aircraft and their emergent aviation markets:AIAA-2014-0535[R]. Reston:AIAA, 2014. [9] 黄俊,杨凤田. 新能源电动飞机发展与挑战[J]. 航空学报, 2016, 37(1):57-68. HUANG J, YANG F T. Development and challenges of electric aircraft with new energies[J]. Acta Aeronautica et Astronautica Sinica, 2016, 37(1):57-68(in Chinese). [10] KIM H D, PERRY A T, ANSELL P J. A review of distributed electric propulsion concepts for air vehicle technology:AIAA-2018-4998[R]. Reston:AIAA, 2018. [11] KIM H D, BERTON J J, JONES S M. Low noise cruise efficient short take-off and landing transport vehicle study:AIAA-2006-7738[R]. Reston:AIAA, 2006. [12] BYRON R, WINBORN J. ADAM Ⅲ V/STOL concept[J]. Journal of Aircraft, 1970, 7(2):175-181. [13] GOHARDANI A S. Distributed propulsion technology[M]. New York:Nova Science Publishers, Inc., 2014:173-184. [14] KRATZ J L, THOMAS G L. Dynamic analysis of the starc-abl propulsion system:AIAA-2019-4182[R]. Reston:AIAA, 2019. [15] YOON A, SRASTU F, LOHAN F. Direct-drive electric motor for STARC-ABL tail-cone propulsor:AIAA-2019-4516[R]. Reston:AIAA, 2019. [16] SCHILTGEN B T, FREEMAN J L, HALL D W. Aero-propulsive interaction and thermal system integration within the ECO-150:A turboelectric distributed propulsion airliner with conventional electric machines:AIAA-2016-4064[R]. Reston:AIAA, 2016. [17] FREEMAN J L, SCHILTGEN B T. ECO-150-300 design and performance:A tube-and-wing distributed electric propulsion airliner:AIAA-2019-1808[R]. Reston:AIAA, 2019. [18] FELDER J L, TONG M T, CHU J. Sensitivity of mission energy consumption to turboelectric distributed propulsion design assumptions on the N3-X hybrid wing body aircraft:AIAA-2012-3701[R]. Reston:AIAA, 2012. [19] ARMSTROMG M J, ROSS C A H, BLACKWELDER M J, et al. Trade studies for NASA N3-X turboelectric distributed propulsion system electrical power system architecture[J]. SAE International Journal of Aerospace, 2012, 5(2):325-336. [20] GOHARDANI A S, DOULGERI S. Challenges of future aircraft propulsion:A review of distributed propulsion technology and its potential application for the all-electric commercial aircraft[J]. Progress in Aerospace Sciences, 2011, 47(5):369-391. [21] GOHARDANI A S. A synergistic glance at the prospects of distributed propulsion technology and the electric aircraft concept for future unmanned air vehicles and commercial/military aviation[J]. Progress in Aerospace Sciences, 2013, 57(1):25-70. [22] RODAS E A E, LEWE J H, MAVRIS D. Feasibility focused design of electric on-demand aircraft concepts:AIAA-2014-2856[R]. Reston:AIAA, 2014. [23] BARIS E, LANDMAN D. An investigation into the potential benefits of distributed electric propulsion on small uavs at low reynolds numbers:AIAA-2017-3924[R]. Reston:AIAA, 2017. [24] FLYNN M C, JONES C E, RAKHRA P, et al. Impact of key design constraints on fault management strategies for distributed electrical propulsion aircraft:AIAA-2017-5034[R]. Reston:AIAA, 2017. [25] HERMETZ J, RIDEL M, DOLL C. Distributed electric propulsion for small business aircraft a concept-plane for key-technologies investigations[EB/OL]. (2019-03-26)[2020-03-28]. https://hal.archives-ouvertes.fr/hal-01408988 [26] LASKARIDIS P, VAL E, KIRNER R, et al. Assessment of distributed propulsion systems used with different aircraft configurations:AIAA-2015-4029[R]. Reston:AIAA, 2015. [27] HOELZEN J, LIU Y L, BENSMANN B, et al. Conceptual design of operation strategies for hybrid electric aircraft[J]. Energies, 2018, 217(11):1-26. [28] ORDAS I, NIELSEN E J, RALLABHANDI S K, et al. Adjoint-based design of a distributed propulsion concept with a power objective:AIAA-2019-3681[R]. Reston:AIAA, 2019. [29] OREFICEL F, VECCHIA P D, CILLIBERTI D, et al. Aircraft conceptual design including powertrain system architecture and distributed propulsion:AIAA-2019-4465[R]. Reston:AIAA, 2019. [30] HOOGREEF M F M, VOS R, VRIES R, et al. Conceptual assessment of hybrid electric aircraft with distributed propulsion and boosted turbofans:AIAA-2019-1807[R]. Reston:AIAA, 2019. [31] VRIES R, BROWN M, VOS R. Preliminary sizing method for hybrid-electric distributed-propulsion aircraft[J]. Journal of Aircraft, 2019, 56(1):2172-2187. [32] VRIES R, BROWN M, VOS R. Preliminary sizing of a hybrid-electric passenger aircraft featuring over-the-wing distributed-propulsion:AIAA-2019-1811[R]. Reston:AIAA, 2019. [33] MA Y Y, ZHANG W, ZHANG Y Z, et al. Sizing method and sensitivity analysis for distributed electric propulsion aircraft[EB/OL]. (2020-03-19)[2020-03-28]. https://doi-org-443.e2.buaa.edu.cn/10.2514/1.C035581. [34] PATTERSON M D, DASKILEWICZ M J, GERMAN B J. Conceptual design of electric aircraft with distributed propellers:multidisciplinary analysis needs and aerodynamic modeling development:AIAA-2014-0534[R]. Reston:AIAA, 2014. [35] SCHILTGEN B, GREEN M W, GIBSON A R. Analysis of terminal area operations and short field performance of hybrid electric distributed propulsion:AIAA-2013-4265[R]. Reston:AIAA, 2013. [36] MOORE K R, NING A. Takeoff and performance trade-offs of retrofit distributed electric propulsion for urban transport[J]. Journal of Aircraft, 2019, 56(5):1880-1891. [37] PERRY A T, BRETL T, ANSELL P J. System Identification and dynamics modeling of a distributed electric propulsion aircraft:AIAA-2019-3086[R]. Reston:AIAA, 2019. [38] BORER N K, PATTERSON M D, VIKEN J K, et al. Design and performance of the NASA SCEPTOR distributed electric propulsion flight demonstrator:AIAA-2016-3920[R]. Reston:AIAA, 2016. [39] SCHMOLLGRUBER P, DOLL C, HERMETZ J, et al. Multidisciplinary exploration of DRAGON:An ONERA hybrid electric distributed propulsion concept:AIAA 2019-1585[R]. Reston:AIAA, 2019. [40] SCHMOLLGRUBER P, DONJAT D, RIDEL M, et al. Multidisciplinary design and performance of the ONERA hybrid electric distributed propulsion concept (DRAGON):AIAA-2020-0501[R]. Reston:AIAA, 2020. [41] MOORE K R, NING A. Distributed electric propulsion effects on traditional aircraft through multidisciplinary optimization:AIAA-2018-1652[R]. Reston:AIAA, 2018. [42] ANIBAL J L, MADER C A, MARTINS C R R A. Aerothermal optimization of X-57 high-lift motor nacelle:AIAA-2020-2115[R]. Reston:AIAA, 2020. [43] WICK A T, HOOKER J R, HARDIN C J. Integrated aerodynamic benefits of distributed propulsion:AIAA-2015-1500[R]. Reston:AIAA, 2015. [44] SCHILTGEN B T, FREEMAN J F, HALL D W. Aero-propulsive interaction and thermal system integration within the ECO-150:A turboelectric distributed propulsion airliner with conventional electric machines:AIAA-2016-4064[R]. Reston:AIAA, 2016. [45] NGUYEN N T, REYNOLDS K, TING E, et al. Wing shaping distributed propulsion aircraft concept for improved aerodynamic efficiency:AIAA-2016-3413[R]. Reston:AIAA, 2016. [46] PERRY A T, ANSELL P J, KERHO M F. Aero-propulsive and propulsor cross-coupling effects on a distributed propulsion system[J]. Journal of Aircraft, 2018, 55(6):2414-2426. [47] PATTERSON M D, GERMAN B. Wing aerodynamic analysis incorporating one-way interaction with distributed propellers:AIAA-2014-2852[R]. Reston:AIAA, 2014. [48] STOLL A M, BEVIRT J, MOORE M D, et al. Drag reduction through distributed electric propulsion:AIAA-2014-2851[R]. Reston:AIAA, 2014. [49] STOLL A M. Comparison of CFD and experimental results of the LEAPTech distributed electric propulsion blown wing:AIAA-2015-3188[R]. Reston:AIAA, 2015. [50] DEERE K A, VIKEN J K, VIKEN S A, et al. Computational analysis of a wing designed for the X-57 distributed electric propulsion aircraft:AIAA-2017-3923[R]. Reston:AIAA, 2017. [51] DEERE K A, VIKEN S A, CARTER M B, et al. Computational analysis of powered lift augmentation for the LEAPTech distributed electric propulsion wing:AIAA-2017-3921[R]. Reston:AIAA, 2017. [52] VIKEN J K, VIKEN S A, DEERE K A, et al. Design of the cruise and flap airfoil for the X-57 Maxwell distributed electric propulsion aircraft:AIAA-2017-3922[R]. Reston:AIAA, 2017. [53] DEERE K A, VIKEN J K, VIKEN S A, et al. Computational component build-up for the X-57 distributed electric propulsion aircraft:AIAA-2018-1275[R]. Reston:AIAA, 2018. [54] MURPHY P C, LANDMAN D. Experiment design for complex VTOL aircraft with distributed propulsion and tilt wing:AIAA-2015-0017[R]. Reston:AIAA, 2015. [55] VECCHIA P D, MALGIERI D, NICOLOSI F, et al. Numerical analysis of propeller effects on wing aerodynamic:tip mounted and distributed propulsion[J]. Transportation Research Procedia, 2018, 29:106-115. [56] HUFF D L, HENDERSON B S, ENVIA E. Motor noise for electric powered aircraft:AIAA-2016-2882[R]. Reston:AIAA, 2016. [57] SYNODINOS A P, SELF R H,TORIJA A J. Preliminary noise assessment of aircraft with distributed electric propulsion:AIAA-2018-2817[R]. Reston:AIAA, 2018. [58] RIZZI S A, PALUMBO D L, RATHSAM J, et al. Annoyance to noise produced by a distributed electric propulsion high-lift system:AIAA-2017-4050[R]. Reston:AIAA, 2017. [59] NARK D M, BUNING P G, JONES A T, et al. High-lift propeller noise prediction for a distributed electric propulsion flight demonstrator:AIAA-2017-3713[R]. Reston:AIAA, 2017. [60] HALLEZ R, COLANGELI C, CUENCA J, et al. Impact of electric propulsion on aircraft noise-all-electric light aircrafts case study:AIAA-2018-4982[R]. Reston:AIAA, 2018. [61] DEERE K A, VIKEN S A, CARTER M B, et al. Comparison of high-fidelity computational tools for wing design of a distributed electric propulsion aircraft:AIAA-2017-3925[R]. Reston:AIAA, 2017. [62] BOHARI B, BORLON Q, SANTOS P B M, et al. Conceptual design of distributed propellers aircraft:non-linear aerodynamic model verification of propeller-wing interaction in high-lift configuration:AIAA-2018-1742[R]. Reston:AIAA, 2018. [63] SHARPE P, AGARWAL R K. Numerical analysis of propeller-wing interaction in aircraft with distributed electric propulsion:AIAA-2019-3691[R]. Reston:AIAA, 2019. [64] GIBSON A R, HALL D, WATER M. Superconducting electric distributed propulsion structural integration and design in a split-wing regional airliner:AIAA-2011-0223[R]. Reston:AIAA, 2011. [65] REYNOLDS K, NGUYEN N, TING E, et al. Wing shaping concepts using distributed propulsion[J]. Aircraft Engineering and Aerospace Technology, 2014, 86(6):478-482. [66] MUKHOPADHYAY V, OZOROSKI T A, MCMILLIN M L. Structural configuration analysis of advanced flight vehicle concepts with distributed hybrid-electric propulsion:AIAA-2018-1747[R]. Reston:AIAA, 2018. [67] NGUYEN E, ALAZZRD D, DOLL C, et al. Co-design of aircraft vertical tail and control laws using distributed electric propulsion[J]. IFAC-PapersOnLine, 2019, 52(12):514-519. [68] NGUHAN N T, REYNOLDS K, TING E. Distributed propulsion aircraft with aeroelastic wing shaping control for improved aerodynamic efficiency[J]. Journal of Aircraft, 2018, 55(3):1122-1140. [69] MASSEY S J, STANFORD B K, WIESEMAN C D. Aeroelastic analysis of a distributed electric propulsion wing:AIAA-2017-0413[R]. Reston:AIAA, 2017. [70] HOOVER C B, SHEN J W, KRESHOCK A R. Whirl flutter stability and its infiuence on the design of the distributed electric propeller aircraft X-57:AIAA-2017-3785[R]. Reston:AIAA, 2017. [71] CRAVANA A, MANFREDA G, CESTINO E, et al. Aeroelastic behavior of flexible wings carrying distributed electric propulsion systems[EB/OL]. (2017-01-26)[2020-03-28]. https://doi.org/10.4271/2017-01-2061. [72] LIU C Y, SI X Y, TENG J F, et al. Method to explore the design space of a turbo-electric distributed propulsion system[J]. Journal of Aerospace Engineering, 2016, 29(5):1-9. [73] GLADIN J, TRAWICK D, PERULLO C, et al. Modeling and design of a partially electric distributed aircraft propulsion system with GT-HEAT:AIAA-2017-1924[R]. Reston:AIAA, 2017. [74] VELDHUIS L, KHAJEHZADEH A. Analysis and design of a wing trailing edge mounted over-the-wing distributed propeller propulsion system:AIAA-2017-3692[R]. Reston:AIAA, 2017. [75] KIM J H, KWON K S, ROY S. Megawatt-class turboelectric distributed propulsion, power, and thermal systems for aircraft:AIAA-2018-2024[R]. Reston:AIAA, 2018. [76] WANG S Q, ECONOMOU J T, TSOURDOS A. Design of a distributed hybrid electric propulsion system for a light aircraft based on genetic algorithm:AIAA-2017-4305[R]. Reston:AIAA, 2017. [77] LAWHORN D, RALLABANDI V, IONEL D M. Power electronics powertrain architectures for hybrid and solar electric airplanes with distributed propulsion:AIAA-2018-4995[R]. Reston:AIAA, 2018. [78] STRATHOFF P, STUMPF E, NUNO M, et al. A study on "through-the-road"-parallel hybrid powertrains for small aircraft with distributed electric propulsion:AIAA-2019-3677[R]. Reston:AIAA, 2019. [79] 孔祥浩, 张卓然, 陆嘉伟, 等. 分布式电推进飞机电力系统研究综述[J]. 航空学报, 2018, 39(1):021651. KONG X H, ZHANG Z R, LU J W, et al. Review of electric power system of distributed electric propulsion aircraft[J]. Acta Aeronautica et Astronautica Sinica, 2018, 39(1):021651(in Chinese). [80] SCHILTGEN B, GREEN M, GIBSON A R, et al. Split-wing propulsor design and analysis for electric distributed propulsion:AIAA-2011-0224[R]. Reston:AIAA, 2011. [81] BORER N K, MOORE M D. Integrated propeller-wing design exploration for distributed propulsion concepts:AIAA-2015-1672[R]. Reston:AIAA, 2015. [82] STOKKERMANS T C A, ARNHEM N, SINNIGE T, et al. Validation and comparison of RANS propeller modeling methods for tip-mounted applications[J]. AIAA Journal, 2019, 57(2):566-580. [83] MIKHALYOV S, DUNAEVSKY A, TEPERIN L, et al. Effects of propeller slipstream of distributed electric propulsion on the wing-flap system[EB/OL]. (2019-12-17)[2020-03-28].https://doi.org/10.1051/matecconf/201930402018. [84] SUZUKI Y, DUNHAM W, KOLMAMOVSKY I, et al. Failure detection and control of distributed electric propulsion aircraft engines:AIAA-2019-0109[R]. Reston:AIAA, 2019. [85] GARRETT M, AVANESIAN D, GRANGER M, et al. Development of an 11 kW lightweight, high efficiency motor controller for NASA X-57 distributed electric propulsion using SiC MOSFET switches:AIAA-2019-4400[R]. Reston:AIAA, 2019. [86] VALEMCIA E, HIDALGO V, LASKARIDIS P, et al. Design point analysis of a hybrid fuel cell gas turbine cycle for advanced distributed propulsion systems:AIAA-2015-3802[R]. Reston:AIAA, 2015. [87] OKAI K, HIMENO T, WATANABE T, et al. Potential of aircraft electric propulsion with SOFC/GT hybrid core:AIAA-2016-4713[R]. Reston:AIAA, 2016. [88] OKAI K, NOMURA H, TAGASHIR T, et al. Effects of fuel type on aircraft electric propulsion performance with SOFC/GT hybrid core:AIAA-2017-4957[R]. Reston:AIAA, 2017. [89] CHOI B B, MORRISON C, DEVER T, et al. Propulsion Electric Grid Simulator (PEGS) for future turboelectric distributed propulsion aircraft:AIAA-2014-3644[R]. Reston:AIAA, 2014. [90] ROTHHAA P M, MURPHY P C, BACON B J, et al. NASA langley distributed propulsion VTOL tilt-wing aircraft testing, modeling, simulation, control, and flight test development:AIAA-2014-2999[R]. Reston:AIAA, 2014. [91] FREEMAN J L, KLUNK G T. Dynamic flight simulation of spanwise distributed electric propulsion for directional control authority:AIAA-2018-4997[R]. Reston:AIAA, 2018. [92] PAPATHAKIS K V, KLOESEL K J, LIN Y, et al. Design and development of a 200-kW turbo-electric distributed propulsion testbed:AIAA-2016-4611[R]. Reston:AIAA, 2016. [93] PAPATHAKIS K V, SESSIONS A M, BURKHARDT P A, et al. A NASA approach to safety considerations for electric propulsion aircraft testbeds:AIAA-2017-5032[R]. Reston:AIAA, 2017. |
[1] | Yanhua ZHANG, Dengcheng ZHANG, Zhangwen ZHOU, Yuchang LEI, Lin LI. Concept and design of virtual rudder surface aircraft based on circulation control: Review [J]. Acta Aeronautica et Astronautica Sinica, 2024, 45(6): 629608-629608. |
[2] | Chuihuan KONG, Dawei WU, Zhaoguang TAN, Lijun PAN, Rubing MA, Jiangtao SI. Design of fully electric scheme for three⁃surface verification aircraft [J]. Acta Aeronautica et Astronautica Sinica, 2024, 45(6): 629618-629618. |
[3] | Jinghui DENG. Technical status and development of electric vertical take⁃off and landing aircraft [J]. Acta Aeronautica et Astronautica Sinica, 2024, 45(5): 529937-529937. |
[4] | Zhixing JI, Zhanxue WANG, Liwen CHENG, Jiang QIN, He LIU. Performance and matching analysis of gas turbine hybrid engine integrated with fuel cells in aviation [J]. Acta Aeronautica et Astronautica Sinica, 2024, 45(10): 129326-129326. |
[5] | ZHANG Xingyu, GAO Zhenghong, LEI Tao, MIN Zhihao, LI Weiling, ZHANG Xiaobin. Ground test on aerodynamic-propulsion coupling characteristics of distributed electric propulsion aircraft [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2022, 43(8): 125389-125389. |
[6] | SU Ning, HUANG Wenxin. Parallel power generation system based on dual-stator winding induction generator for electric propulsion aircraft [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2022, 43(8): 325409-325409. |
[7] | ZHANG Bendong, JIANG Jun, LI Zhi, LI Shimin, ZHANG Chaohai. Partial discharge characteristics of future more electric aircraft under low air pressure [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2022, 43(7): 325374-325374. |
[8] | ZONG Jian'an, ZHU Bingjie, HOU Zhongxi, YANG Xixiang. Design of hybrid-electric fixed-wing VTOL aircraft propulsion system [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2022, 43(5): 225395-225395. |
[9] | RAO Chong, ZHANG Tiejun, WEI Chuang, LIU Ying. Influence mechanism of propeller slipstream on wing of a distributed electric aircraft scheme [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(S1): 726387-726387. |
[10] | ZHANG Yang, ZHOU Zhou, GUO Jiahao. Effects of distributed electric propulsion jet on aerodynamic performance of rear wing [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(9): 224977-224977. |
[11] | LIU Haigang, LIU Liang, WANG Peng, ZHOU Wei. Model based simulation and analysis of energy optimization characteristics of more-electric aircraft [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(8): 525801-525801. |
[12] | ZHANG Zhuoran, XU Yanwu, YU Li, LI Jincai, XIA Yiwen. Parallel HVDC electric power system for more-electric-aircraft: State of the art and key technologies [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(6): 624069-624069. |
[13] | LEI Tao, KONG Delin, WANG Runlong, LI Weilin, ZHANG Xiaobin. Evaluation and optimization method for power systems of distributed electric propulsion aircraft [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(6): 624047-624047. |
[14] | LI Ni, BU Shuhui, SHANG Bolin, LI Yongbo, TANG Zhili, ZHANG Weiwei. Aircraft intelligent design: Visions and key technologies [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(4): 524752-524752. |
[15] | ZHANG Maoquan, CHEN Haixin. Estimated model of range and endurance of small electric UAVs [J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2021, 42(3): 625085-625085. |
Viewed | ||||||
Full text |
|
|||||
Abstract |
|
|||||
Address: No.238, Baiyan Buiding, Beisihuan Zhonglu Road, Haidian District, Beijing, China
Postal code : 100083
E-mail:hkxb@buaa.edu.cn
Total visits: 6658907 Today visits: 1341All copyright © editorial office of Chinese Journal of Aeronautics
All copyright © editorial office of Chinese Journal of Aeronautics
Total visits: 6658907 Today visits: 1341