---
title: "New Pelton Concept – up to six nozzles horizontal"
author: "Josef Martin Erlach"
affiliation: "Erlach & Erlach GmbH, Ravensburg, Germany"
event: "17th International Seminar on Hydropower Plants (Viennahydro 2012), Laxenburg near Vienna"
presented: 2012-11-22
file_date: 2012-11-04
language: en
original_pdf: https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf
original_pages: 9
document_type: transcription
transcription_checked: 2026-09-29
---

# "NEW PELTON CONCEPT" UP TO SIX NOZZLES HORIZONTAL

**Josef Martin Erlach**, Erlach & Erlach GmbH

Full paper for the 17th International Seminar on Hydropower Plants (Viennahydro), presented on 22 November 2012 in Laxenburg near Vienna. The PDF was created on 4 November 2012.

- Original PDF (9 pages): [2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf)
- Context page: [Pelton turbine: System Erlach](/en/pelton-turbine/)

> **About this file.** This is a transcription of the original PDF, not a summary. Wording, spelling, grammar, units and numbering follow the original, including its errors; obvious errors are left as they are and marked with *[sic]* only where a reader could mistake them for a transcription error. The original has no printed page numbers. The markers **[PDF page N]** give the page index of the PDF file; each marker links to that page (`#page=N`). The diagrams in Fig. 5 to 9 show measured curves; their individual data points are not transcribed. Text in blocks marked **Editorial figure description** is added by Erlach & Erlach in 2026 and is not part of the original. The authoritative version is the PDF.

---

**[[PDF page 1]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=1)**

## Abstract

Since the basic invention of the Pelton turbine more than 140 years ago, the developing underwent significant phases. It started from the one- and two jet horizontal turbine, up to the six-jet turbine 50 to 60 years ago, with the requirement to increase the power density of the unit. This could only be managed by turning the main axis into a vertical position to drainage the complied splash water to the outlet channel. Some manufacturers where then motivated to develop three jet horizontal units - with varying success.

A sudden inspiration gave me the kick to review the complete Pelton turbine from top to bottom. The result was a New Pelton Concept, now referred to as the Erlach Turbine.

## 1. Introduction

In a Pelton turbine the entire useful pressure energy is converted into kinetic energy in the nozzle. After the water is leaving, the free jet is in an ambient atmospheric pressure of the housing and hits tangential the double buckets of the runner. The free jet is cut by a central splitter into two equal parts and is deflected in the bucket by nearly 180°. Through the deflection almost all of the jet energy is converted into mechanical energy acting as an impulse force to the rotor. The remaining residual energy of approximate 2 to 4 % is still present as kinetic energy. This outlet spray water is - after leaving the buckets - divergent, and the entrainment of air is considerable, the ratio to water is about 40 to 70%. The direction from the buckets is mainly axial to the rotations axis and radial outwards. During the phase when the bucket hits the free jet and at the last part of dewatering the bucket, fine water spray, like foam, can be mixed with the rotation air, it is with low energy, non directed and can fill out the housing.

The housing shall be designed to guide this spray water in direction of the outlet channel, without a reflection to the runner. The runner itself has great air consumption, due to the ventilation effect of the buckets. These runner losses are about 1 to 1.3 %. Due to this fact, also water foam can be suctioned into the runner. At the beginning of the Pelton era, only horizontal Pelton turbines, with one or two nozzles were built. The dewatering of the spray water and foam to the outlet channel could be managed with a good housing, without spray water and foam to be rejected back to the runner.

**[[PDF page 2]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=2)**

Later on, to increase the energy density, Pelton turbines were built with up to six nozzles. In order to control dewatering, the runner in the housing and the runner's axis became vertical. Whereas the outlet spray water in direction to the channel, normally causes no problem, the above outlet water spray needs special care to avoid interference with the runner.

## 2. Realization of the invention for a New Horizontal Pelton

### 2.1. Study of investigation of the splash water in Pelton housings

The theoretical knowledge of the interaction between runner and housing, is still not in a status to follow the out coming splash water, independent of hydraulically design of the runner buckets and various housings constellations and frictions, as well different amount of air, makes it difficult for a complex calculation (Ray tracing).

Almost two decades ago the first splash water distribution on a horizontal double-jet turbine was started as model test on the Institute of Waterpower and Pumps in Vienna [1], on the basis of visual documentation, qualified by efficiency measurements. A PIV measurement of three dimensional splash water flow distribution was started ten years later at the same Institute [1].

Measurements of the jet impact velocity in casings on a vertically six-jet prototype turbine, HPP Koralpe [2] was done by the University of Technology, Graz. The aim of this research project was getting a wider knowledge of the processes in the casing of Pelton runners in terms of velocity of the water flow and the transport of portion of air, their distribution over the base area of the casing. The amount of entrained air could be calculated by the using results. The target was to get information of aeration for the HPP Kops II, with the Pelton turbine running with back pressure in the outlet channel.

A video clip made by TIWAG of the 250 MW HPP Silz, gave me an impressive view of the splash water coming out of this vertically six-jet Pelton turbine runner buckets. The remaining energy in the splash water is still 3 to 4 % and is demonstrated in the velocity. As well the need of air of the divergent water spray can be seen in combination with the air ventilation of the runner. These impressions are really challenging.

### 2.2. Dewatering of the splash water create a new housing

Again, for Pelton turbines it is essential, to have free jet, bucket design, gap angular between the nozzles, ventilation and aeration in a good matching with the housing. Up to two-jet horizontal Pelton turbine, the spray water can be good drained down to the channel. The gap angular can be selected up to 90 degrees for good dewatering the buckets. With a three jet-turbine this gap must be strongly reduced, to avoid spray water going upwards in the housing and fall down into the runner. A reducing of the gap angular shortens the time of dewatering and decrease the performance of the turbine.

The target was to create a new housing which is able to protect the runner from down falling water to the runner and this with up to six nozzles.

**[[PDF page 3]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=3)**

**Fig. 1.** HPP Koralpe; View form *[sic]* the injectors and runner section, down to the main measuring section (velocity and flow distribution), positioned on the trash rack

Text in the figure (original):

| Koralpe: Pelton turbine | |
|---|---|
| 6 jet vertically | |
| Q<sub>N</sub> | = 8 m³/s |
| H<sub>n</sub> | = 720 m |
| P | = 50 MW |

Caption inside the reproduced figure (German, from reference [2]): "Abbildung 5.27: Vertikale Abstrahlgeschwindigkeit v<sub>J</sub> [m/s]". Colour scale 0 to 11 [m/s].

> **Editorial figure description (not part of the original):** Hexagonal plan view of the measuring section below a vertical six-jet runner. The runner with its buckets sits in the centre; six injector outlines point towards it from the sides of the hexagon. Coloured contour fields show the measured vertical velocity of the water leaving the runner, with values between about 0 and 11 m/s; the highest values (red) lie in front of the injectors. Two black arrows point into the runner from opposite sides.

**Fig. 2.** HPP Koralpe; Cross section
Velocity and flow distribution of the splash water from the runner to the trash rack, transposed from the measurements, see Fig. 1

> **Editorial figure description (not part of the original):** Vertical section through the casing of the vertical six-jet turbine. From the runner at the top, dashed lines in several colours fan out downwards and to the side towards the floor; many lines on the left run up to the casing wall and down along it. Coloured blocks on the floor mark the measured flow at the trash rack.

**[[PDF page 4]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=4)**

### 2.3. From the IDEA to the REALITY

Transposing a latent idea in combination with all my experience by studding various investigations of splash water in Pelton houses, especially [1, 2], the target came closer.

In consideration of the constellation of the six-jet vertical turbine and in knowledge of the main splash water flow distribution (see Fig.1, 2), the system was turned (main shaft) to 90 degrees in to horizontal axis (see Fig.3). The idea was to avoid now the splash water reflecting to the runner, a spray water guiding ring in a certain distance to the runner was placed. The outer guiding ring is designed in a manner following the main flow of splash water. With a second ring on inner side, the complied splash water and foam is focused in a way that the runner is protected from the spray water and vagabonded foam. Incident water particles mixed with air, hitting in a certain angle of attack at the side plates, will be reflected in more or less radial direction. There is still some kinetic energy in the drainage water, so the needed space will be moderate, the housing becomes small.

Preliminary semi homologue model tests, with different housing constellations, brought out encouraging results to continue.

**Fig. 3.** Principle sketch of the new six-jet horizontal Pelton turbine housing
Drainage of full flow with six-jet in action down to the outlet channel

Text in the figure (original):

- Left side: Undisturbed splash water, showing the natural distribution after leaving the runner buckets
- Right side: The focused splash water flow, following the new housing design, without reflecting to the runner

> **Editorial figure description (not part of the original):** Section through the horizontal shaft with the runner in the middle. On the left half, without guide rings, dashed lines spread from the buckets across the housing. On the right half, the new housing with an outer and an inner guide ring: the dashed lines are led sideways between the rings and run down along the housing wall.

### 2.4. New Axial Distributer

A water supply system in axial direction to the nozzles (optional) was in the focus as well. As it is known, that in a conventional six nozzle distributer, different flow conditions are existing. Deviation can be with individual nozzle operation +/- 0.3 to 0.6 % of over all efficiency. It is known that the last nozzle have the best inflow

**[[PDF page 5]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=5)**

condition. This nozzle feeding pipe design was taken as basic design and was only to multiply for the others up to six. The commercial aspects are the production-oriented components. The design can be seen in Fig. 10

A special application (Fig. 4) is the distributer from the cone to the individual elbows and pipes for the feeding water to the injectors. The aim was to have the same inflow condition to every branch independent of the active nozzle combination as well a low friction coefficient, low swirls and to keep the diameter of the cone small.

**Fig. 4.** Inflow cone of the axial distributer
Special application (see also patent EP 2 035 689)

Text in the figure (original): "Inflow from the penstock" (arrow on the left), "to the injectors" (arrow at the top right).

> **Editorial figure description (not part of the original):** Half section of a conical pipe that widens from left to right along a horizontal axis. At its end a curved elbow branches off upwards to the injectors; a cone-shaped body sits on the axis at the end of the pipe.

**Fig. 5.** Axial distributer, efficiency deviation with the individual nozzles operation from 1 to 6, at full load

**Fig. 6.** Conventional distributer, efficiency deviation with the individual nozzles operation from 1 to 6, at full load

Axes of Fig. 5 and Fig. 6 (original): vertical axis η/η<sub>max</sub> from 0,95 to 1,00; horizontal axis speed n<sub>1'</sub> from 34 to 46.

> **Editorial figure description (not part of the original):** Both diagrams show one curve per nozzle, each running as an arch with its highest point near n<sub>1'</sub> = 40. In Fig. 5 (axial distributer) the curves lie almost on top of each other. In Fig. 6 (conventional distributer) they are spread apart: the highest curve reaches 1,00, the lowest stays below about 0,99. The diagrams have no legend assigning the curves to individual nozzles.

**[[PDF page 6]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=6)**

### 2.5. Model Tests

In consideration of a substantial reform of the complete Pelton turbine, extended full homologue model tests had been made over the complete water way from the main closing device up to the drainage to the outflow channel, concerning inflow condition to the nozzles with different distributers, nozzle tests, jet quality, and ventilation losses of the runner, runner displacement, splash water from the buckets, as well different housing constellations and aeration. This was done with various nozzles opening and combinations over the full operating field.

As basis to compare the new Pelton concept with a conventional Turbine, a well known standard vertical six-jet turbine from the research partner VOITH Hydro was taken with the components and data from vertical measurement. The complete Model Turbine (state of art) with distributer, injectors and runner was turned in horizontal position and adapted with the new housing. Later on with the same basic constellation, the axial distributer was changed with the conventional one.

A good equipped and certificated Laboratory (HSLU – Luzern), with high accuracy flow calibration (mass and volume) could be found. The crew could demonstrate an absolute overall measurement accuracy of 0.25 %, with the repeatability of 0.1 %. This was the back ground of a seriously test campaign.

The evaluation of the hydraulically efficiency was made in accordance to IEC 60103 *[sic; probably meant: IEC 60193, model acceptance tests for hydraulic turbines. Not confirmed by the author]*. Some extracts of the result can be seen in:

<u>One jet in operation;</u> Fig. 5, 6. It demonstrates the inflow effect of the new axial system versus the conventional distributer, tested with the same conditions. The data are normalized by taking η<sub>max</sub> for both diagrams the same value.

<u>Three jets in operation;</u> Fig. 7. Shows the increasing of the performance due to the new possibilities to extend the angular separation between the nozzles over the complete circumference. For a three-jet horizontal Pelton in prior art the gap is about 60 to 70 degrees. In the case of the new Pelton Turbine, the gap becomes 120 degree and enables time enough to empty the runner buckets. Fig. 8. Shows the vertical six-jet Pelton turbine (state of art) at full load as basis, versus to the new horizontal Pelton turbine conventional distributer and as well the new axial distributer.

<u>Six jets in operation;</u> Fig. 9. Shows the vertical six-jet Pelton turbine (state of art), at full load as basis, versus to the new horizontal Pelton turbine with the conventional distributer

**Fig. 7.** Six-jet Horizontal Pelton, with axial distributer, three-jet in operation, at full load
Increasing of the efficiency with 120 degree versus 60 degree

Axes (original): vertical axis η/η<sub>max</sub> from 0,96 to 1,01; horizontal axis n<sub>1'</sub> from 34 to 45. Curve labels (original): "60 degree jet 2,3,4" and "120 degree jet 1, 3, 5".

> **Editorial figure description (not part of the original):** Two arched curves that coincide at low speed. The curve for 120 degree (jets 1, 3, 5) peaks slightly above 1,00 near n<sub>1'</sub> = 40 and falls slowly towards 45. The curve for 60 degree (jets 2, 3, 4) peaks lower, near n<sub>1'</sub> = 39 to 40, and falls steeply below 0,96 before n<sub>1'</sub> = 44.

**[[PDF page 7]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=7)**

**Fig. 8.** Six-jet Horizontal Pelton with three-jet in operation at full load
Vertical axis versus horizontal axis

Axes (original): vertical axis η/η<sub>max</sub> from 0,96 to 1,01; horizontal axis n<sub>1'</sub> from 34 to 45. Curve labels (original): "3-jet vertical as **basis**", "3-jet horizontal conventional distributer", "3-jet horizontal axial distributer".

> **Editorial figure description (not part of the original):** Three arched curves with their highest points between n<sub>1'</sub> = 39 and 41. The dashed curve "3-jet vertical as basis" is the lowest over most of the range. The two solid curves for the horizontal machine lie above it and peak slightly above 1,00.

**Fig. 9.** Six-jet Horizontal Pelton with six-jet in operation at full load
Vertical axis versus horizontal axis

Axes (original): vertical axis η/η<sub>max</sub> from 0,96 to 1,01; horizontal axis n<sub>1'</sub> from 34 to 43. Curve labels (original): "6-jet vertical axis as **basis**", "6-jet **basis** model turned to horizontal axis with new housing".

> **Editorial figure description (not part of the original):** The dashed curve "6-jet vertical axis as basis" rises to about 1,00 near n<sub>1'</sub> = 39 to 40 and ends before n<sub>1'</sub> = 41. The solid curve for the model turned to horizontal axis with new housing lies above it over the whole range, peaks slightly above 1,00 between n<sub>1'</sub> = 38 and 40 and drops steeply after n<sub>1'</sub> = 41.

## 3. Main functions & advantages of the "New Horizontal Pelton"

### 3.1. Basic concept:

- Increasing the power density of the unit by using up to six jet per unit instead two (three) jets
- Flat turbine efficiency characteristic, good operation condition down to 5% of discharge. (summer and winter operation with one unit)
- Better performance due to an extension of the gap angular between the nozzles over the complete circumference.
- Outflow conditions from the runner buckets are left and right symmetric, so the conditions become better then in a vertical Pelton.
- Specially at full load condition, a clearly increasing of the performance
- Reduction of costs, especially of the generator because of higher speed opportunity.
- No additional baffle blades to avoid splash water and foam.
- Involving all advantages of a horizontal unit, now using up to six jets

**[[PDF page 8]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=8)**

The basic concept can be used with the conventional distributer, see Fig. 11 and as well as option with the axial distributer, see Fig. 10.

### 3.2. Option: Axial distributers

- Complete inflow arrangement, from the main closing device to the injectors, standard components (off store, good value) can be used; short work shop duration time can be realized.
- Weight reduction about 20 %, reduction of welding can be reduced up to 50 % compared to a six jet conventional distributer.
- Good for standardisation and parametric design, easy to adapt to different runner diameters. Axial bearing forces are better balanced.
- The housing concept is created in such a way, that for all nozzle combination (2 to 6), the basic configuration is the same.
- All nozzle inflow condition are nearly equal, therefore they have the same efficiency condition, independent of the active nozzle combination.
- Easier to extend the gap angular between the nozzles.

## 4. New Pelton Concept, schematic sketch → Erlach Turbine

**Fig. 10.** Relates to the configuration with an axial distributer (six jet)

> **Editorial figure description (not part of the original):** Left: side view of the machine on its foundation. The inflow comes from the left through a valve and a cone; curved pipes branch off above and below the axis and lead to the injectors at the runner housing; the generator stands on the right. Right: front view of the housing with six injectors arranged around the runner.

**Fig. 11.** Relates to the configuration with an conventionally distributer (six jet)

> **Editorial figure description (not part of the original):** Left: side view of a narrow housing with the generator on the right. Right: front view; the inflow comes from the left through a valve and runs as a spiral pipe around the housing.

**[[PDF page 9]](2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=9)**

## 5. Status

Preliminary, semi homologue model tests was made at the University of Stuttgart (Prof. Dr.-Ing. E. Göde), seen as function test, brought out encouraging results.

Full homologue model tests carried out at the University of Luzern (Prof. Dr.-Ing. Th. Staubli), validated full the function of the first six nozzles horizontal Pelton turbine.

In cooperation with the research partner VOITH Hydro, this concept was brought to commercial use. As the first license partner VOITH Hydro is on the way to realize the New Pelton Concept.

Concerning the new Pelton turbine, three patents are granted worldwide for the design of housing and the water supply system.

## References, literature

[1] B.List, P.Angerer, H.-B.Mattias, Institute for Waterpower and Pumps, Vienna University of Technology, VELOCITY FIELD MEASUREMENTS ON PELTON – TURBINES WITH PIV, Hydro forum 2000, Czorsztyn October 2000, 475-482

[2] A. Arch, D. Mayr, G. Zenz, Graz University of Technology
Jet impact Velocity in Casings of Pelton Turbines, HPP Koralpe
Detailuntersuchung Gehäuseströmung: Abschlussbericht Juli 2007,
S 85, Fig. 5.27

> **Editorial note on the references:** Neither reference carries a DOI or link in the original. No stable online source for [1] or [2] has been verified; [2] is a project report. The patent named in Fig. 4, EP 2 035 689, is listed with a link to the patent document on [Pelton turbine: patents](/en/pelton-turbine/patents/#ep2035689).

## Autor

Josef Martin Erlach,
Erlach & Erlach GmbH
Gustav-Werner-Straße 7, 88213 Ravensburg, Germany
Tel: +49 (0) 751 63400, Fax: +49 (0) 751 7643 441
E-Mail: josef@erlach-erlach.com

> **Editorial note:** Contact details as printed in 2012. Current contact: hello@erlach-erlach.com.

## C.V.

I was born in Austria (AT). Start of my career was HPP Kaprun, AT. In 1963, I joined Andritz Hydro (Escher Wyss) for 40 years. I am experienced in commissioning, mechanical design, specification and site testing, for all types of hydraulic machines, plants and components for new and refurnished projects, until 2003. After retirement I started as an independent consultant, specialized in advising for pumped storage power stations (VIW, Kops II AT / GNFE, ES). In 2010, I was honored with the IEC "1906 Award".