A pressure-wave supercharger is a charger for the engine which compresses the combustion air. Supercharging increases the power output with the same engine dimensions and engine speeds whilst reducing fuel consumption as the engine is able to work in more favourable ranges. In the past, the pressure-wave supercharger was developed to its present state in particular by the Swiss company COMPREX. In the case of the WENKO drive a pressure-wave supercharger charges the engine up to 2.6 bar in absolute terms.
The principle of supercharging (simplified):
With pressure-wave supercharging pulsating hot exhaust gases and fresh air are combined in the supercharger. The exhaust gas pressure waves compress the fresh air and force it into the combustion chambers. These processes are controlled by the central component of the pressure-wave supercharger, the cylindrical cell rotor. The speed of the latter is synchronised with the engine speed via a V-belt.
The cells in the cell rotor alternately
open and close the exhaust gas and fresh air apertures, each located
on one side of the housing. When the aperture on the exhaust gas
side is reached as a result of the rotary movement, pressurised
exhaust gas flows into the cell and compresses the fresh air there.
Meanwhile the cell rotor continues turning and the cell described
reaches the aperture on the fresh-air inlet side (to the engine).
The fresh air, now highly compressed, flows into the engine's
inlet tract. Before the exhaust gas can now flow in as well, the
aperture is closed again as a result of the cell rotor turning
and the exhaust gas column is reflected ("runs up against
a wall"). It flows back to the exhaust gas side of the housing
and leaves the cell through the aperture (to the outside), which
has now become free again as a result of the rotary motion. The
exhaust gas column leaves the cell on the exhaust gas side at
very high speed, thereby creating negative pressure "behind
it". This means that fresh air can be sucked into the cell
via an aperture now becoming free on the fresh air side. From
this point onwards the process is repeated cyclically.
The exchange of energy in the pressure-wave supercharger occurs at sound velocity, which results in a practically instant response even at low engine speeds.
Although there are various different processes for compressing intake air (turbocharger, mechanical "G supercharger", pressure-wave supercharger, i.a.), the pressure-wave supercharger is the preferred system because it combines the advantages of mechanical and exhaust gas turbocharging. In contrast to the turbocharger, the pressure-wave supercharger effectively increases the engine torque even in the engine's lower speed range. It does not have the infamous "turbo hole". In any case, the turbo is currently mainly installed on large-capacity engines. Although it increases their power output into even more ridiculous speed ranges, it does not improve efficiency in the "lower", range needed in practice - on the contrary, in order to avoid knocking in the turbocharged range the compression ratio is reduced, which worsens the efficiency over the entire operating range.
