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JLA Cross-Flow Turbines

  1. The cross-flow principle
  2. The cross-flow range
  3. Work field
  4. Applications

The cross-flow principle

1903 :
Australian engineer A.G.M. Mitchell invents the cross-flow turbine principle.
1917 :
Hungarian-born Professor Donat Banki publishes various papers on the subject.
1920 :
German company Ossberger is awarded patents for its technical improvements and markets these turbines on a huge scale.
1949 :
Mockmore and Merryfield, from Oregan State University, publish a comprehensive work on cross-flow turbine theory and results obtained using their prototype.
1982 :
U. Meier, for the SKAT, begins to draft construction plans for a cross-flow turbine designed for technology transfer to countries in the southern hemisphere (Series T1 - T12).

In addition to its low runaway speed, one of the major advantages of this turbine is the relative simplicity of its design, as it only includes two or three moving parts :

  • the rotor (without axial thrust) ;
  • 1 or 2 valves for the flow control

What makes it special is that the water crosses the rotor twice, while the peripheral blades are driven successively by a centripetal radial and radial centrifugal flow.

The rotor is completely insensitive to foliage, twigs, algae, plastic packaging, etc., which are ejected after a half-rotation due to the combined effect of the water flow and centrifugal force.

In terms of maximum efficiency, the Francis turbine is superior to the cross-flow for a flow rate equivalent to 80% of the nominal flow rate. But the cross-flow produces a better efficiency when used for a small fraction of the nominal flow rate (up to +/- 1/6 of the nominal flow rate for a subdivision of 1/3 - 2/3). Maximum efficiency is not always the best factor when selecting a turbine, as it all depends on the frequency of occurrence of turbinated flows.
 

The cross-flow range

Conventional equipment for small hydroelectric installations is still relatively expensive. In order to resolve this problem, we have developed highly robust standard hydraulic cross-flow turbine models. Based on a useful height of three metres, these turbines will be a superior replacement for the water wheels used by our ancestors.

Design

We make no compromises when it comes to the quality of our machines. Our JLA turbines are built to last and can be used continuously for many decades with minimum maintenance.

When designing our machines, we aim to create:

  • Compact equipment ;
  • Optimum mechanical reliability ;
  • Maximum performance with variable flow rates ;
  • Guaranteed operation with the full range of turbine flows

Turbine casing and bearings

The turbine casing is made of cast iron, which has the following advantages:

  • Excellent castability and easy machining, which reduces costs
  • Excellent corrosion resistance
  • Dimensional stability

The bearings housings, which are also cast iron, are:

  • Specially made for our turbines
  • Equipped with a double-ring sealing system and central lubrication, which ensures that the turbine casing remains watertight
  • Protected against any inflow of water
  • Fitted with amply dimensioned high quality roller bearings

All the turbine components are easily accessible, which greatly facilitates the removal of any part (runner, roller bearings, etc). Maintenance is limited to occasional lubrication of the bearings and seal rings. The rotor can easily be checked by removing the turbine cap.

As the turbine casing is watertight, it is possible to use the full drop height by controlling the depression under the turbine runner.

Water inlet

Depending on the configuration of the site, the water inlet can be either vertical or horizontal.

The flow rate is controlled by means of a low operating torque using one or two specially profiled valves, fitted with a stainless steel axle and watertight. These valves split the water flow in two, before shaping it so that its penetrates the rotor without shocks.

The flow rate control devices are easy to regulate - either by using electric/hydraulic actuators or manually.
 

Rotor

The rotor consists of laminated steel blades, which are hydraulically designed and specially profiled in order to optimise turbine efficiency. These blades are mounted between two flanges and carefully welded, using a special procedure developed at the JLA & Co workshops. When the drop height increases, intermediate reinforcement disks are added in order to make the whole system rigid. The rotor is then hot-dip galvanized and coated with special epoxy, which makes it highly corrosion and abrasion resistant.

All our rotors are dynamically balanced. They are symmetrical, so that the PTO can be located on the left, right or even on both sides, depending on the layout.

Efficiency

Our JLA turbines are specially designed to meet the needs of variable flow installations. Our dual cell turbines make it possible to work with a very wide range of flow rates (from nominal flow rates to one sixth of the latter) with a efficiency of between 75 (guaranteed minimum) and 80 % (maximum average efficiency).

Installation

A JLA Cross-Flow is straightforward to install, costs very little and respects the environment. It is easy to control, maintain and exceptionally long-lasting.

JLA Cross-Flow turbines are designed to be mounted on a metal chassis above the outlet channel and as low as possible but out of reach of the floods.

In the event of a weak head with a variable downstream level, the turbine is fitted with a draft tube so that the full available head can be used efficiently, regardless of the downstream level.
 

Work field

JLA29

Head : from 2.5 to 80 m

Design flow : from 30 to 600 lit./sec.

Mechanical power : from 2 to 120 kW

Speed : from 200 to 1.100 RPM

JLA52

Head : from 2.5 to 12 m

Design flow : from 500 to 1200 lit./sec.

Mechanical power : from 10 to 100 kW

Speed : from 110 to 250 RPM

If the characteristics of your site are within the following work field, we can provide you with the ideal equipment. If this is not the case, this is no problem, as you can take advantage of our experience of developing tailor-made solutions. Please contact us if you would like to discuss possible options.
 

Applications

A JLA Cross-Flow turbine can be used for a wide variety of applications:

  • Electricity generation, either connected to the national grid or for independent generation at an isolated site
  • Hydro-mechanical applications, connected to a mechanical receptor: pump, mill, heat pump, sawmill, multiplication stage, etc.