The Z engine What is the Z engine

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 K bar

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 1. 7 -1. 9: 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 + De. NOx-catalyst + oxicat + particulate filter = 2800 € 2 working cylinders less Compressor needed Low injection pressure, low cost nozzles • No De. NOx catalyst • No particulate filter • • • = - 600 € = +200 € = - 400 € = - 500 € = - 100 € Together = - 1400 € lower production costs per engine!