Hot bulb engine

The hot bulb engine is an internal combustion engine with internal mixture formation and low compression. In it the fuel on an uncooled, glowing wall ( hot bulb ) is injected during the compression stroke, the fuel ignites. He mostly works on the two-stroke principle with crankcase supercharging.

The hot bulb engine makes little demands on ignition or knock resistance of the fuel and one of the first multi-fuel engines.

Classification

The hot bulb engine is one of the heat engines in Hubkolbenbauweise. With regard to the classification between petrol or diesel principle was sometimes spoken in the hot bulb engine of a third type, since it combines features of both motor principles in itself.

With the diesel engine, it shares the internal mixture formation, but not the compression ignition. Advantageous with respect to diesel engines is that it does not rely on a good atomization of the injector due to the evaporation of fuel on the Glühkopfwandung to achieve a high-quality fuel-air mixture. A disadvantage is the poor controllability of the ignition time ( uncontrolled ignition timing ), the low speed and thus low power output per liter and higher fuel consumption.
With the gasoline engine it shares the low working pressure, the chronologically separate mixture formation and combustion phase ( in contrast to the overlap of these two phases in the diesel principle) as well as the presence of an already largely homogeneous fuel -air mixture during ignition.

Construction

The spherical prechamber, the actual hot bulb is preheated and will not be actively cooled during use. The sprayed into the hot bulb fuel evaporated, and the tangential connecting duct to the cylinder ensures the compression stroke by incoming air for a strong turbulence and evaporation.

Due to the low evaporation speed, it takes long time to form an ignitable air-fuel mixture is available. This requires a very early stage of the fuel injection (about 130 ° crank angle before the top dead center), much earlier than in the diesel engine.

Fuel and function

Semi-diesel engines can be operated with normal diesel fuel, heavy fuel oil, fish oil, paraffin, with all vegetable oils and even creosote.

Before a cold hot bulb engine can be started, the hot bulb must be pre-heated by external heating ( blow torch ).

Alternatively, there are designs with a separate small fuel tank and a spark plug in the hot bulb, so the engine can be started on petrol. After reaching the operating temperature is changed to heavy oil.

Longer idle periods are by design not possible, the hot bulb cools down due to lack of Wärmenachlieferung so that the engine stops. This cooling can by the shape of Glühkopfes (so-called Zündsack ) and an adjustable spray angle injector be delayed or prevented.

Use and history

The hot bulb engine was invented by the Englishman Herbert Akroyd Stuart. The first patents date from 1886, but the most important patent is from 1890. Akroyd Stuart invented by the hot bulb engine was produced in 1891 by Richard Hornsby & Sons in Grantham.

Semi-diesel engines were manufactured on and mehrzylindrig and built a long time as large-scale marine engines.

The hot bulb engine was made famous by the legendary Bulldog of Heinrich Lanz Mannheim. The English company Hornsby 1896 was the first, who had built a tractor with a 20 hp licensed Akroyd hot bulb engine -. It was also Hornsby, who built the first crawler tractor with hot bulb engine. These had been fitted in 1905 glow head with wheels with caterpillars. The large scavenging losses of this engine fitted in the tractor operating a special problem: Many Lanz- Bulldog should have stuck with his unburned exhaust gases and sparks fields and barns on fire. The problem you came in with subsequently modified exhaust systems.

The Russian company Mamin had built semi-diesel engines since 1903 and began 1912 to produce agricultural tractors with semi-diesel engines. In the same year the Swedish company began JV Svenson's engine factory to produce in Augustendal motorized plows with hot bulb engine. 1913, another Swedish manufacturer, Munktells Mekaniska Värkstads AB in Eskilstuna with a large 8.3 -ton twin-cylinder hot-bulb - tractor on the market. The first Lanz Bulldog, the Lanz HL was available only from 1921.

The first locomotive with a hot bulb engine also came from Hornsby and was built there since 1896. It was equipped with a 10 hp Hornsby - Akroyd hot bulb engine -.

Since the era of semi-diesel engines had already begun at the end of the 19th century, they were already well established when the first diesel engines emerged. The big advantage over gasoline engines was the simplicity of the system and easier storage of fuels, which were also less dangerous than gasoline. In addition, the demands on the fuel and thus also the costs are significantly smaller. Marine engines about could burn spent engine oil besides heavy oil, others ran with easily purified crude oil.

Large semi-diesel engines are rarely made due to the necessarily high consumption. In the model there is for micro- combustion engines in the range up to about 30 cc, the so-called glow plugs or Glühzündermotor, which operates on a similar principle of operation.

Known manufacturers of semi-diesel engines are or were Bolinder, Schlüter, Landini Lanz, Ursus, Pampa Bulldog.

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