Cross-Flow Turbines are optimal for use in power generation at low fall heights (2 to 70m slope). Our Cross-Flow Turbine was developed in cooperation with Univ. Prof. Krešimir Franjić, who lectured at the University of Fluid Machinery in Zagreb, and the associated calculation software was written by his daughter DI Katarine Franjić. The entire project was given a Greek name, as is common for neromylos: OBELIXX
Neromylos OBELIXX turbines are, contrary to the usual through-flow turbines (Bánki system with 2/3 to 1/3 flap control in the flow channel), equipped with a control flap which moves off-center over the turbine rotor. The advantage is that the flow is uniform over the entire blade width and the turbine water does not have to move laterally before the rotational energy is generated at the rotor. Since there are no interfering flap parts (such as bánki) in the inlet channel, inlet flow losses are also minimized. The flap is moved digitally in the hundredths of a millimeter range by a stepper motor and the water volume is thus optimally converted into rotary motion at the turbine blades. This results in a fine controllability of the turbine and an increased efficiency of approx. 84.5% (approx. 79% with conventional Bánki) over the entire available water supply. Only with a water supply of less than 18% of the expansion quantity are the efficiencies worse.
The sealing of the rotating parts is done by highly wear-resistant oil seals, as they are also used in the automotive industry. The bearings are from well-known manufacturers such as FAG and SKF and can be equipped with central lubrication at extra cost. The rotor is manufactured from high-strength stainless steel on water-jet cutting machines in the thousandth of a millimeter range and then the inlet and outlet angles are attached to the blades. Then the drive shaft, bearing shaft, sides and support disks are welded all around using a special welding process. The rotor unit with the bearings can be removed from the housing as a complete unit in one piece, thus reducing any repair times and simplifying maintenance work.
The housing is made of thick-walled, coated steel and the cutting edge between housing and slider is made of CNC milled and screwable segments. This results in the advantage that the cutting edge components, which are considered wear parts, can be replaced quickly and efficiently. As a rule, after approx. 5 years of continuous operation.
neromylos places special emphasis on the fact that each individual case is calculated and designed independantly. Subsequent manufacturing on our most modern CNC machines guarantees the accuracy of the parts in the thousandth of a millimeter. This special processing enables us to produce parts in a recurring quality. This also results in only minor corrections during the subsequent balancing of the impeller. Here we do not use balancing weights, which could fall off over time, but determine the position and size of the holes on the computer-controlled balancing machine, which removes material where it is required and thus leads to the optimum balancing and concentricity result. Each impeller is provided with a balancing certificate and documented. Per impeller 21 to 32 blades are used. Another advantage of the OBELIXX turbine is that relatively high speeds can be achieved without the need for an intermediate gearbox. Speeds 500 to 1000 rpm (revolutions per minute). Due to its simplicity and robustness, the neromylos Cross-Flow Turbine can also be used for slightly impure water.