Direct injection hot-bulb motor

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The hot bulb engine with direct injection , also referred to as a medium-pressure motor , Mitteldruckglühkopfmotor and semi-diesel engine is a combustion engine with internal mixture formation and an average compression ratio . The fuel is injected directly into this engine and ignites by itself. The hot-head engine with direct injection is a two-stroke engine with crankcase scavenging and membrane inlet. It is an evolution of Glühkopfmotors , with whom he is the eponymous design feature of the uncooled cylinder head it shares. The engine was invented by Anton Lentz and a patent applied for in 1952 (patent granted in 1956). The engine was used in Lanz brand tractors .

features

The engine is a heat engine in reciprocating piston design and is based on the conventional hot-head engine designed as a single-cylinder engine. It can be air or water-cooled, but the motors built by Lanz are all equipped with thermosiphon cooling (water cooling). The most important design feature of the engine is the cylinder head, which is shaped in such a way that it forms a conical combustion chamber with the piston at top dead center. The fuel is injected at the tip of this conical combustion chamber directly towards the piston crown. Since the cylinder head is not cooled and the engine compression ratio is in the range of about 11: 1, the fuel will self-ignite. The injector in the cylinder head is cooled to prevent premature vaporization and the resulting misfire. The engine is a two-stroke engine, the gas exchange is controlled via inlet and outlet ports. With nominal speeds of around 600 to 800 min −1 , it is a medium- speed runner . Diesel fuel is used as fuel . In order to achieve the required engine operating temperature, a mixture of diesel fuel and petrol is injected into Lanz engines for starting and warming up and ignited with a spark plug. When the engine has reached the required temperature, it is switched to diesel operation and the spark plug is switched off.

Differentiation from the diesel engine

The diesel engine generally has a higher compression, which heats the combustion air to such an extent that the fuel is ignited by the temperature of the air (compression ignition), while the hot-head engine uses the temperature of the cylinder head to ignite the fuel-air mixture.

Advantages over a conventional hot-head motor

By eliminating an antechamber, the cylinder head can be manufactured more easily and inexpensively, for example as a forging. The piston crown no longer needs a heat store, which is why the piston can be made of light metal. The lower thermal load on various components of the motor generally increases operational safety and reliability. The starting process is simplified and the cylinder head does not need to be preheated. The fuel consumption is reduced by around 30% to approx. 237 g / kWh and is roughly on par with a contemporary swirl chamber diesel engine of the same power.

Technical data of an example motor

Parameters Motor of the Lanz Bulldog D 6007
cooling Thermosiphon cooling
Injection pump Bosch PFR 1-8 100/33
Injector Bosch DL 60-S 879
Injection pressure 117.7 bar
Medium work pressure 4.51 bar at 800 min −1
Medium piston speed 6.93 m / s
Compression ratio 12: 1
Bore × stroke 190 mm × 260 mm
Displacement 7370 cm 3
rated capacity 44 kW (60 HP) at 800 min -1
maximum torque 578 N · m (58.9  kpm ) at 700 min -1
Lowest fuel consumption 232.5 g / kWh (171 g / PSh)

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