Method for calculating the power of a rotor-screw machines Valeriy A. Lebedev, Georgy V. Serga, Irina V. Davydova, Tatiana V. Atoyan, Irina G. Koshlyakova and Alexander V. Gordienko MATEC Web Conf., 226 (2018) 01007 Published online: 07 November 2018 DOI: 10.1051/matecconf/201822601007