Water Turbine Glossary

A few  pictures and terms that may help clarify the dizzying variety of water turbines used in the 19th and early 20th century (some types of which are still used today).  The glossary is naturally Tyler-centric - the turbine notes and images on these pages reflect the fact that the Ledyard Up-Down sawmill is powered by a John Tyler turbine.  The specific choices of turbines types in part 2 below are not meant to be complete, but only a partial introduction to classification and historically important turbines in the late 19th century. These notes are by a rank amateur - turbine engineers and technology historians no doubt will read and shudder like an unbalanced runner.
turbine parts

Left, Tyler turbine. Photo used with permission of the American Precision Museum, Windsor, Vermont.   Center, from J. Tyler US patent 20456 (1858).  Right, The runner from the Tyler turbine at Ledyard Up-down sawmill when we removed it for inspection in 2013.  Note the corrosion and rough edges on the vanes.

Water Turbine Glossary - Part 1. Terms and Components

 apron Platform upon which the turbine case is set and fastened.

 Increased levels of water below the mill can back up into the tailrace and impede operation of the water wheel.  Many types of water wheels are susceptible to backwater during spring freshets or other times of flood; that is, they don't operate as well as with lower levels of water in the tailrace.  A common claim for many turbines is that operation is not affected by backwater. 
 The multiple separate chambers in a turbine runner through which water flows. The runner vanes define the buckets. 19th century turbine manufacturers continually modified and patented “improved” forms and shapes of the runner buckets, and used these new features as a focal point in their marketing literature.   

 The static enclosure around a turbine runner is called the curb (or case). Provides for mounting the turbine assembly and controls the flow of water through the turbine via one or more gates. The cover for the case is referred to as a dome in some of the Tyler literature. 
 A sliding or pivoting panel that controls the entry of water into a turbine. Some turbine types have multiple gates, or a cylindrical gate that regulates flow into multiple compartments of the turbine case. Turbine and waterwheel power systems typically also have at least one other gate: the head gate controlling water from the headrace or sluiceway into the turbine penstock 

 Many turbine types have guides – fixed partitions in the turbine case that direct the flow of water into the runner. The compartments in the case that are defined by the guides are called chutes. Tyler turbine cases, and most scroll-type turbines, do not have guides per se; rather, the case consists of a single compartment. 
 head The height difference between the water source upstream (typically a pond) of the mill and the water in the outflow, or tailrace.  The Ledyard Up-Down samill has a head of 9 - 9.5 feet when the pond is full. 

 The pipe or tank that supplies water directly to a turbine. The turbine inlet can be attached to a separate penstock, or set completely within the penstock. In the latter installations, a sealed draft tube at the water exit of a turbine allows placement of the turbine above the level of water in the tailrace for easier access.  Sometimes spelled pentstock.   

 step bearing

 Also called a foot-step bearing or simply a step. The thrust bearing that supports a vertical shaft. In water turbines there are examples of foot-step bearings of conical and half-spherical shape – the bottom of the runner shaft is turned to match. A common material for turbine foot-step bearings is lignum vitae.
Some turbine designs are manually adjustable to raise the foot-step bearing in order to compensate for wear. Upper figure is a drawing from a brief description of Tyler turbines (Scientific American, 1864) showing a cross-section of the foot-step bearing (grey), the cup bearing turned into the bottom of the runner shaft (cross hatch), and the step adjuster mechanism. Bottom figure shows the wood step bearing of the Ledyard sawmill Tyler turbine during the 1970s restoration of the mill.
 turbine step adjuster
wood turbine step bearing

The main revolving part of a water turbine. 

 turbine pit
 Or tail-pit. The excavation in the base of a mill in which the turbine discharges. The difference in height of the water in the tail-pit and the water reservoir supplying the turbine is the maximum available head of water. 

 The partition in a turbine runner that separate and form the individual buckets. See the figure in runner that show the large convex vanes in a Tyler turbine; that is, curved away from the flow of water into the runner. This is relatively unusual – in many turbine types the vanes are concave. Also called a float. 

Water Turbine Glossary - Part 2. Classification and Types of Turbines


 Refers to a type of mixed-flow turbine built by American manufacturers from about the 1870s into the 20th century. Companies and turbines of this type include Francis, Leffel, Hercules, Risdon, Swain and others.
American-type turbines receive water which flows inward from the periphery, downwards, and then flows outwards or radially.
The figure (from Tyler, W.W., 1898.) shows why the later American turbines are “mixed-flow”: The direction of water changes as it moves through the runner.
 direction of flow
 Turbines can be classified by the general direction(s) of water flow through the runner buckets.
  • axial flow turbine. Or parallel flow turbine. A turbine in which the direction of water flow through the buckets is generally along the direction of the runner shaft axis. A key early type of axial flow turbine was developed by French engineer Feu Jonval in the 1840s. Jonval turbine adaptations were developed and sold by U.S. manufacturers throughout the second half of the 19th century. 
  • mixed flow turbine. Water flow through the runner buckets changes direction. 
  • radial flow turbine. Flow of water in the runner buckets is perpendicular to the axis of the runner shaft 
  • inward flow turbine. The flow of water in the runner buckets is outside inwards. The early Francis turbines were inward flow, but later were developed into mixed-flow turbines as the shapes of the runner vanes became more complex. outward flow turbine. The flow of water in the runner buckets is from the inside outwards. Fourneyman-type turbines are the classic example.
 Francis turbine  

 An important type of American mixed-flow turbine invented and developed by British-born James Francis who emigrated as a young man to America (and worked briefly on the new railroad to Stonington Connecticut in 1833). Francis moved to Lowell Massachusetts and shortly thereafter became the Manager of Locks and Canals. He used a careful experimental approach to increase the efficiency of Uriah Boyden’s improved Fourneyman turbine. Francis-type turbine designs were hugely influential, widely used in the last half of the 19th century, and are still made and used today. Figure from Safford and Hamilton, 1922, p. 1253.
 Francis turbine
 Fourneyman turbine
An outward flow turbine developed by French engineer Benoit Fourneyman beginning in the in the 1820s. An important turbine technology development since it was the first small turbine that could develop sufficient power for industrial use. The Founrneyman turbine greatly influenced the further development of modern turbines. The Fourneyman turbine technology was brought to the U.S. in the early 1840s and used throughout the nineteenth century. Figure from Safford and Hamilton, 1922, p. 1249.
Fourneyman turbine

 Leffel turbine

 James Leffel of Springfield, Ohio invented, developed, and manufactured turbines which were widely used through the last half of the 19th century. Characterized by a series of 12 gates around the periphery of the case. The company was founded by Leffel in 1862 is still in business in Springfield, Ohio and producing turbines. Leffel turbines were also manufactured in New Haven Connecticut.  Figure from 1885 Leffel catalog
Leffel turbine
 Pelton Waterwheel Pelton wheels are the most widely distributed and most commonly encountered type of impulse turbine. Their cast iron buckets have a characteristic tandem cup form that is credited with achieving their high efficiency. They were developed by Lester Pelton in the Mother Lode region of California in the 1870s to provide mechanical power for hard rock mining; Pelton's design achieved significant improvements in efficiency compared to other impulse wheels. In later decades Pelton wheels proved adaptable for hydroelectric power, particularly at locations with high head and low flow volume, for which purpose they have been scaled up massively to units of 100,000 HP and more. In the second half of the 20th century, improved forms of Francis turbines have displaced Pelton wheels except for installations with very high (>2,000 ft.) head.  The wooden or cast iron shroud typically found on Pelton wheels helped direct water discharge (rather than direct the inflowing water jet as on reaction wheels). Thank you to Mike Dalbey, volunteer at Wilder Ranch State Park in Santa Cruz, CA for Pelton wheel information.
 Image from The Pelton Water Wheel Co. catalog, 1898, page 8
Pelton waterwheel

 Reaction  waterwheel
 Many turbine types are classified as reaction: power generation depends upon changes in water pressure acting on the turbine vanes within an enclosed case.
Reaction turbines can be contrasted with impulse turbines in which a jet of water is directed onto the runner vanes. Impulse turbines do not require an enclosed case.
Rose Wheel

 Likely named for the inventor Timothy Rose, but believed by some to be named for the appearance of the water spraying out of the wheels when operating.

“…the cast iron scroll wheel (or rather one of them, for there were two, both set on a large wooden shaft, on the inner end of which was the saw crank-wheel.  These wheels were sometimes called "Rose wheels" as the water would fly out at each side like the blossom of a rose, when running under a "full head" of water.  The tail race of the mill runs just in front of the mill, and is the whole brook.”

From archival material at the Henry Ford Museum in Dearborn MI describing the Georgetown Massachusetts Spofford –Morse sawmill which was subsequently moved to and rebuilt at the Ford museum.  Quote is from Peterson, Charles E..  Sawdust Trail, Annals of Sawmilling and the Lumber Trade from Virginia to Hawaii via Maine, Barbados, Sault Ste. Marie, Manchac and Seattle to the Year 1860.  Bulletin of the Association for Preservation Technology. Vol. 5, No. 2, 1973. 84-153. 

(note: much of the same material as the Sawdust Trail article is also in Peterson, C.E., Early Lumbering:  A pictorial essay, in America’s Wooden Age: Aspects of its Early Technology, Brooke Hindle (ed.), Tarrytown, NY: Sleepy Hollow Restorations. 1975. 63-83.)

Photo right top, A pair of rose wheels at a sawmill site Rhode Island.  Machinery moved to RI from Massachusetts and assembled in the 1930s.  Right bottom, from Timothy Rose, Water-Wheel, US Patent 7674, September 5, 1850.  Rose previously patented an improved form of reaction turbine described in US Patent 1376, Timothy Rose Water-Wheel.

Rose Wheel

Rose Wheel patent pic

 scroll wheel

 Or scroll-type turbine. The figure shows a top-view cross-section of a Tyler turbine from J. Tyler US patent 20456 (1858) showing in grey the scroll shape of the turbine case. There is typically a single gate controlling the entry of water into a scroll turbine. Blue arrows show direction of water flow in the case when the turbine control gate is open
scroll turbine water flow
 waterwheel In the 19th century the term “water wheel” was often applied both to what we think of today as waterwheels, but also enclosed turbines. 

Bibliography (see also reference list on Tyler turbine water wheel page of this website)