Franz Lang's goal was to improve the diesel engine as a vehicle engine. To achieve a particularly soft running engine and a small load on the mechanicals. For this he experimented with undivided combustion chambers, thus the direct injection. The energy consumed was favorable, but the necessary injection pressure was too high and the combustion very harsh. He returned to his air cell or Lanova system. It connected the external cell or chamber in the cylinder head with a special shape of the combustion chamber. The butterfly shaped combustion chamber led to a particularly favorable turbulence when blowing out the air cell. Thus the engine worked also with less excess air - which corresponds to a high load - still soot-free.
Franz Lang and Albert Wielichand founded the Lanova company in Germany in 1930.
In some high-speed diesel engines, turbulence is created by an auxiliary chamber referred to as an energy or air cell. Energy cells differ in design and location. In most engines, the cells are located in the cylinder heads. One type of energy cell that is located in the cylinder head is a divided chamber and turbulence chamber. The Lanova cell is the divided chamber type.
The Lanova system uses these air or energy cells to pull a small amount of compressed air into them. As the injector fires, a small amount of fuel is directed into the cell and fires in this chamber just as it fires in the combustion chamber. With the orifice in the cell, the ejected energy is metered out and continues to push on the piston as it travels down. The out flow also swirls the air/fuel mix giving a cleaner more complete burn in the cylinder. This system is very efficient and provides lots of medium rpm torque.
The Lanova design, employs a combustion chamber consisting of two rounded spaces cast in the cylinder head. The inlet and exhaust valves open into the main combustion chamber. The fuel-injection nozzle lies horizontally, pointing across the narrow section where the lobes join. Opposite the nozzle is the two-part energy cell, which contains less than 20 percent of the main-chamber volume.
The action is as follows: During the compression stroke, the piston forces air into the energy cell. Near the end of the stroke, the nozzle sprays fuel across the main chamber in the direction of the mouth of the energy cell. While the fuel charge is traveling across the center of the main chamber, between a third and a half of the fuel mixes with the hot air and burns at once. The remainder of the fuel enters the energy cell and starts to burn there, being ignited from the fuel already burning in the main chamber. At this point, the cell pressure rises sharply, causing the products of combustion to flow at high velocity back into the main combustion space. This sets up a rapid swirling movement of fuel and air in each lobe of the main chamber, promoting the final fuel-air mixing and ensuring complete combustion. The two restricted openings of the energy cell control the time and rate of expulsion of the turbulence-creating blast from the energy cell into the main combustion space. Therefore, the rate of pressure rise on the piston is gradual, resulting in smooth engine operation.
The divided combustion chamber is similar, in some respects, to other types of chambers. It is similar to an open combustion chamber in that the main volume of air remains in the main combustion chamber and principal combustion takes place there. Both the divided chamber and the turbulence chamber depend on a high degree of turbulence to ensure thorough mixing and distribution of the fuel and air. However, turbulence in a divided combustion chamber is dependent on thermal expansion caused by combustion in the energy cell and not on engine speed as in other types of auxiliary combustion chambers.
High-speed motion picture taken through a glass window in a full-scale engine, has led to the following information as to the combustion process in a Lanova Diesel engine. The fuel supply into the cell, which depends principally on the fuel injection and the design of the air-cell, has a large influence on the engine performance. The fuel spray, if injected through the injector with a small spray angle toward the mouth of the cell, does not produce much mixture in the main combustion chamber before ignition, which burns slowly until the outflow of hot gases from the cell has improved the mixture formation to such a degree that quicker combustion becomes possible. These processes contribute toward a slow pressure rise in the early stage of combustion and high thermal efficiency. Furthermore, it was ascertained by the high-speed photography that ignition in the main chamber starts generally before that in the cell, and at the latest simultaneously with the ignition in the cell.