The Z engine

What is the Z engine? 4/2-stroke, 2-cylinder engine Revolutionary work principle combines the best aspects of 2- and 4-stroke engines Part of the compression cycle is made outside of the working cylinder, so all of the cycles of 4-stroke engine can be done in a single crankshaft rotation Compact size Light weight Small emissions Low manufacturing costs, no after treatment needed

4-stroke cycles compressed to single crankshaft rotation (Atkinson cycle) Fully valve controlled gas exchange Diesel or Otto engine Turbo charger and supercharger (piston compressor) 2-cylinder Z engine provides equal power output to a 4-cylinder 4-stroke engine HCCI combustion with ignition injection = single fuel RCCI Internal EGR Easily balanced mass forces and mass moments Good torque characteristics High downsizing degree Excellent transient behaviour Good driveability

The work cycle of the Z engine Z-engine allows providing the same power in two working cylinders as conventional 4 stroke diesel engine in 4 cylinders, downsizing and low manufacturing cost are achieved.

Exhaust cycle Exhaust valves open 50° BBCD and close 120° ABCD  2 x 180° = 360° pulses for the turbo charger Exhaust gases hot enough for oxicat

Injection Fuel injected during 110° - 120° ABDC, when the exhaust valves are closing Long mixing time before the ignition, 60° – 70° Injection pressure 700 – 1200 bar, duration 5° – 12° Hollow cone spray Small spray penetration Small droplets Fuel injected to the hot internal exhaust gas  Partial fuel reforming High temperature and low pressure during the injection  Rapid fuel evaporation Gas temperature and pressure during the start of the injection: 700 – 800 K, 1,5 – 2,5 bar Temperature drop of the gas in the cylinder during the injection: 200 – 400 K Heat for the fuel evaporation from the internal exhaust gas

Intake cycle (scavenging) Intake valves opens 60° BTDC and closes 45° BTDC Intake pressure 4 – 20 bar  Velocity of the intake gas: 300 – 500 m/s Internal EGR 15 – 45%, acts as an intern heat exchanger Hot, active radicals in the EGR can be used to assist the ignition No overlapping of the intake and exhaust valves  No losses of the intake gas Fuel evaporation cools the mixture: more air to the cylinder Electric heater in the intake channel for the cold start Glow plug for the cold start

The temperature and pressure curves between 80° - 40° BTDC = during the fuel injection and intake

Final Compression Expansion ratio: 15:1 – 17:1 Primary compression is made in piston compressor, secondary in the work cylinder: 3-5:1 Short compression time  Low amount of heat transfer Fuel evaporation before final compression and high intercooling rate  Low compression temperature, more air in to the cylinder Compression temperatures at TDC: 800 K at part load, 700 K at full load  The compression temperature decreases when the load increases Lower gas temperature  Lower compression pressure, higher bmep

Ignition delay curve of the HCCI mixture And the ”safe operation area” marked

Combustion and work cycle Single fuel RCCI, ignition injection close to TDC Controlled By: Temperature at TDC, lambda, ignition injection amount and timings intercooling rate, valve timing Pressure and temperature at TDC controlled by adjusting intake air pressure and temperature Low temperature at TDC: no self ignition Start of combustion: 0 -15° ATDC Short combustion duration: high efficiency Lambda : low Tmax, low Nox, no aftertreatment needed Active radicals assist the ignition Active radicals lower CO and HC as well as the high enough combustion temperature, 1700 – 2000 K No knock, as ignition allways at the right side of NTC area

Diesel – RK & In-cyliner parameters

Manufacturing costs of the Z-engine compared to a 4-cylinder turbodiesel engine equipped with Common Rail + DeNOx-catalyst + oxicat + particulate filter = 2800 € 2 working cylinders less = € Compressor needed = +200 € Low injection pressure, low cost nozzles = € No DeNOx catalyst = € No particulate filter = € Together = € lower production costs per engine!