Axial hydraulic turbines have long been in use, especially including propeller and Kaplan turbines. Good hydrodynamic and specific design features enable the turbines to be widely used for small net heads and large discharges operating ranges in big and small hydropower plants. Successful construction of these turbines is based primarily on the knowledge of flow fields in all passages, which ultimately contributes to the good perception of the hydraulic losses in its entire flow domain. Firstly from the theoretical standpoint, hydraulic losses mechanisms in all parts of very complex geometry of Kaplan turbine are defined in this paper. Then, the geometrical and flow parameters influences on the turbine energy characteristics were analyzed and their participation in the reduction of efficiency and overall energy balance were determined. The total losses distribution was performed in the wide propeller and combinatory operating regimes by extensive model tests of the Kaplan turbines. Numerical experiments were carried out using Reynolds averaged Navier-Stokes SST as well as Reynolds stress SSG turbulence models. By quantitative and qualitative analyzing of CFD results, the possibility of their application to the whole domain of axial hydraulic turbine were performed, simultaneously determining losses distribution in every turbine passage. The experimental results were used to verify the analytical and numerical results. Losses distributions in relation to integral parameters of swirl flow for certain flow passages were obtained. The analysis of flow field non-uniformity influence on the energy losses in the turbine runner was carried out. For the first time, the constant coefficient in the Voytashevski’s semi empirical formula for determining runner secondary losses was introduced as a variable one. Based on the numerical results, relevant particular losses were distributed and summary diagram of their share in total losses for the entire operating regimes obtained. The results of this complex analysis contribute to contemporary researches of the energy transformation in the axial machines and allow their application in the practical engineering (design and optimization) of technical systems and devices, in which complex turbulent flows occur. The methodology applied in this paper is to consider possible constructive changes to the flow domain geometry in order to achieve better turbine energy characteristics. Aksijalne hidraulične turbine su odavno u upotrebi, a među njima posebno mesto zauzimaju propelerne i Kaplan turbine. Dobre hidrodinamičke i specifične konstruktivne karakteristike omogućuju ovim turbinama široku primenu u oblastima malih specifičnih radova i velikih protoka, kako u velikim tako i u malim hidroenergetskim postrojenjima. Uspešno konstruisanje ovakvih turbina zasniva se pre svega na poznavanju strukture strujanja u svakom njihovom delu, što u krajnjem slučaju doprinosi dobrom sagledavanju hidrauličnih gubitaka u celom njihovom protočnom domenu. U ovom radu su najpre sa stanovišta teorije definisani mehanizmi nastanka hidrauličkih gubitaka u pojedinim delovima veoma kompleksne geometrije strujnog prostora Kaplanove turbine. Zatim su analizirani uticaji pojedinih geometrijskih i strujnih parametara na energetske karakteristike turbina i njihovo učešće u smanjenju stepena korisnosti i ukupnom energetskom bilansu turbine. Veoma opsežnim modelskim ispitivanjima Kaplanovih turbina određene su raspodele globalnih gubitaka u širokoj oblasti propelernih i kombinatorskih režima rada. Korišćenjem i dvojednačinskog SST i naponskog SSG turbulentnog modela urađeno je numeričko istraživanje i utvrđeni su mogućnost i kvalitet njihove primene za proračun strujanja kroz aksijalne hidraulične turbine i dobijanje kvantitativnih i kvalitativnih rezultata za određivanje raspodele energetskih gubitaka. Rezultati dobijeni eksperimentalnim ispitivanjima iskorišćeni su za proveru analitičkih i numeričkih rezultata. Urađena je raspodela gubitaka u funkciji integralnih parametara vihornog strujanja za pojedine oblasti protočnog trakta. Izvršena je analiza neuniformnosti strujanja na energetske gubitke u obrtnom kolu turbina. Po prvi put je konstanta u poluempirijskoj formuli za određivanja sekundarnih gubitaka u obrtnom kolu, koju je predložio Vojtaševski, uvedena kao promenljiva veličina. Na osnovu numeričkih rezultata urađena je raspodela relevantnih pojedinačnih gubitaka i dobijen svodni dijagram njihovog učešća u ukupnim gubicima u celokupnoj radnoj oblasti. Rezultati ove kompleksne analize doprinose savremenim istraživanjima razmene energije u aksijalnim mašinama i omogućuju njihovu primenu u tehničkoj praksi pri proračunu, konstruisanju i optimizaciji tehničkih sistema i uređaja u kojima se javljaju komleksna turbulentna strujanja. Metodologijom primenjenom u radu moguće je razmatrati konstrukcione izmene geometrije strujnog prostora sa ciljem postizanja boljih energetskih parametara.