F2008-06-042
The Z-Engine, a New Type of Car Diesel Engine Having Low Emissions, High Part Load Efficiency and Power Density and Low Manufacturing Costs
The Z-engine is a new type of 2-stroke car diesel engine. A 2-cylinder Z-engine is equal to a 4-cylinder 4-stroke engine in its power output and balancing, having about 30% smaller weight, volume and production costs.
The Z-engine has been tested three years in the test bench and the measurement results are very good. The part load efficiency is over 35% and the NOx emissions are 0,8 g/kWh, better than EU 5.
Modern simulation tools, for example Star CD, GT Power and Diesel RK has been used in the development of the engine.
Since now three master theses, two SAE papers and one FISITA paper have been completed on the subject.
The Z-combustion is a unique combustion system having similarities with swirl chamber combustion and M-combustion. The combustion chamber is heath isolated as in the swirl chamber engine, but it is located in the middle of the piston crown.
The very high intake flow speed to the cylinder causes a very high swirl in the combustion chamber, about 30 - 50, as in the swirl chamber engines. This type of circumstances are impossible to reach in the combustion chamber of a now a days diesel engine. Because of this it has been possible to develop a new type of combustion system, the Z-combustion.
The Z-combustion has a special deNOx phenomenon, based on NOx reduction mechanism caused by thermal cracking hydrocarbons in stratified rich zone during combustion. This phenomenon was found for the first time at the end of 1990 by same Japanese research groups and the results have been published in some COMODIA conferences. They tested it with a test engine having the combustion chamber in the middle of the piston crown and having a very high swirl in the combustion chamber. They calculated also the situation with Chemkin III and the calculated results were equal to the measured. The NOx level was very low.
The newest development of the Z-combustion is to combine the Muldic combustion with the Z-combustion. By having a PCCI combustion before the Z-combustion, it is possible to reduce the NOx and HC-emissions. This has been simulated with Diesel RK program and the test shall be done in the near future with the test engine. It is expected to reach NOx-emisson lower than 0,2 g/kWh.
When combining the Muldic and Z-combustions, the weight point of the combustion moves closer to TDC and this will improve about 2-3% the part load efficiency also because of the lower HC-emissions, and thus lower the losses of the fuel energy to the exhaust gases. There are no problems at full load with HCCI combustion, as in the Z-engine it is possible to control the time-temperatute history of the gas and thus adjust the ignition point.At full load with 20% internal EGR and with cr 15 and BMEP 20, the end temperature of the compression is possible to keep under 800K, if needed.This is not possible in normal diesel engines.
Poster presentation: Future powertrain solutions