Nordberg Radial Engines

from Wikipedia, the free encyclopedia
A Nordberg diesel two-stroke radial engine in Florida that has been preserved in a museum and was used as a pump drive on Lake Okeechobee

Nordberg radial engines was a series of US stationary engines , which in the 1940s and 1950s by the Nordberg Manufacturing Company in Milwaukee , Wisconsin , were manufactured. They were eleven or twelve-cylinder, liquid-cooled radial engines that worked on the two-stroke principle . They were mainly used to drive power generators and pumping stations .

History and use

The Nordberg company had been active in the field of large diesel and stationary engines for industrial applications since the 1910s. To expand the product range, the star two-stroke engine was developed in the 1940s, which was introduced in 1947 as a spark-ignition gas engine. Initially, the main purpose was to generate electricity from natural gas for the immense electricity needs of the aluminum smelters . Due to the vertical arrangement of the output shaft, the motor was also suitable for other applications that require a standing shaft arrangement, such as lifting and pumping stations in hydraulic engineering or in wastewater management. The motors were also used in many municipal power plants in the USA.

In the mid-1950s, 242 of these engines with a total output of 475,000 hp (354,207 kW ) were in use in the power plant of Alcoa's aluminum plant in Port Lavaca , Texas . 80 Nordberg radial engines with 150,000 hp (111,885 kW) were installed in the hut of the Kaiser Aluminum company in Chalmette , Louisiana . The motors drove direct current generators in order to generate the immense demand for direct current required for the smelting flux electrolysis ( Hall-Héroult process ) in close proximity to the melting pans. This made it unnecessary to use converters to convert three-phase current from the network into direct current.

In 1973, the Nordberg Manufacturing Company, which was taken over by Rexnord in 1970, stopped the production of diesel engines and spare parts, which led to the end of the era of these engines due to the increasing shortage of spare parts.

A Nordberg diesel installed in a public power station in Winterset , Iowa in 1956 , which was held as a reserve in 2016, is likely to be the last operational model.

description

The engines were designed as stationary engines with a vertical crankshaft in a star arrangement. Using largely the same components as the housing and cylinder units, there were versions as two-stroke gasoline engines with external ignition for operation with natural gas as well as pure diesel versions for operation with diesel fuel, as well as a variant known as dual fuel , which is similar to a pilot injection engine with a variable mixture could be powered by diesel oil and natural gas.

A typical system for generating electricity extended over two floors in the machine house, the actual motor star was easily accessible on the upper level, which also represented the machine foundation and the operating level. The generator, driven directly by the crankshaft, and the other units such as the starting air tank and compressor, scavenging fan, exhaust manifold and oil pumps as well as the lower bearing of the free shaft end of the generator, were located on the lower level.

cylinder

The cylinders were largely the same in all versions. They had control slots for reverse flushing, and a flushing fan driven externally or by the crankshaft was provided for flushing. In the case of the externally ignited gas engines, two turbochargers with intercoolers could also be installed in order to improve performance and efficiency. Depending on the version, there were two spark plugs or a central injection nozzle for the diesel oil in the cylinder covers. The gas was metered in through a gas valve located in the cylinder wall above the inflow channels. Duafuel models had both the fuel injection nozzle in the cylinder head and the gas metering valve in the cylinder.

In the externally ignited gas engines, the two spark plugs staggered 15 ° and 8 ° before top dead center in order to achieve a softer pressure build-up in the large individual combustion chambers.

In addition, there were compressed air valves for starting in each cylinder head. When the engine was started, the starting compressed air was directed to the cylinders via a distributor in such a way that the pistons in the downward stroke set the engine in motion and brought it to the minimum speed required for starting.

Crank drive

The vertically arranged, single cranked crankshaft was made of alloy cast iron and was assembled from two parts. The lower part consisted of the shaft end for the power take-off, the lower crank arm with counterweight and the crank pin , the upper part consisted of the upper crank arm and the upper shaft end that drove the injection system and control elements on the top of the housing. An additional thrust bearing was arranged under the lower crank arm to take the weight of the crank mechanism .

In contrast to most star aircraft engines, the connecting rods were not designed with a main and secondary connecting rod , but all connecting rods were hinged in the same way with their lower eye in one plane on a bearing ring running on the crank pin. Therefore, the bearing ring had to be aligned in a different way during the rotation on the motor housing and thus the cylinder star. In the eleven-cylinder engine, this was achieved by means of a gear transmission, in which a control pinion mounted in the counterweight of the upper crank web rolled on a toothing fixed to the housing and by engaging a second gear on this shaft in an external toothing of the pivot bearing ring, this was guided in its path without relative to be able to turn to the housing. In the twelve-cylinder engine, this was done using a patented lever system. The connecting rod feet of two opposite cylinders in the cylinder star each carried a slightly angled rigid lever. The two levers were connected to one another by a connecting link. This lever mechanism was arranged between the bearing ring running on the crank pin and the upper crank arm, the crank pin led through an elongated hole in the connecting link that could move without colliding with the crankshaft.

Technical specifications

  • Cylinders: 11 or 12 in a star arrangement
  • Gas change: reverse purging with slot control and purging fan
  • Cylinder bore: 355  mm (14  in )
  • Stroke: 406  mm (16  in )
  • Displacement: approx. 40.4 l per cylinder, corresponds to 444 l for the eleven-cylinder and 484.3 l for the twelve-cylinder
  • Operating speed: 250 to 400 rpm
  • Gas change: external purge air fan, depending on the version, additional turbocharger
  • Output: depending on the type of fuel and charging from 985 to 1560 kW (1340 PS to 2125 PS) at 400 rpm
  • Diameter: eleven-cylinder 3.70 m, twelve-cylinder 4.96 m

swell

Web links

Individual evidence

  1. ^ Electric Utility Information. Winterset City Hall, accessed on February 18, 2016 (English): "The Nordberg and both Cooper engines are still in use today [...]"
  2. ↑ Patent specification on the central connecting rod bearing , PDF file, accessed on August 16, 2015.