HCCI-Combustion in the Z Engine - Part II Aumet Oy

Format:

Conference/Event

Author/Creator:

Janhunen, Janhunen, author.

Conference Name:

SAE 2012 International Powertrains, Fuels & Lubricants Meeting (2012-09-18 : Malmo, Sweden)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

The most common car engine is a 4-cylinder 4-stroke engine. Thecar manufacturers have a great pressure to lower the cost of thecars and this deal also with the engines. The challenges are thecoming new emission norms (for example EURO-6) and also thecustomer acceptance, because of the fact that the car drives areused to the 4-cylinder engine and they want to have the samedriving fun also from the new engines. A 2-cylinder 2-stroke enginehas the same power output and torque as a 4-cylinder 4-strokeengine and thus it offers the same driving fun. Equal balancing iseasy to make without some big additional costs, if the gas exchangeof the engine is made by using poppet valves and camshafts. Asthere are only about 70% of the moving parts in the engine, itsacceleration is even better than by a 4-cylinder engine.One of the latest developments in 2-stroke engines is theZ-engine, having the compression partially transferred outside ofthe working cylinders. This offers new thermo dynamicalpossibilities to adjust the working cycle and the combustion. Asthere are methods to control the temperature at TDC, a HCCIcombustion is possible in the Z-engine at all loads. This lowerssignificantly the cost of the engine, as no urea injection, or NOxcatalyst is needed to pass the coming EU-6 emission norm. The costof the Z-engine is lower also because of the fact that it has only2 working cylinders instead of 4.In 1999, Aumet Oy began to research this 2-stroke car dieselengine, called the Z-engine, in co-operation with the InternalCombustion Engine Laboratory at the Helsinki University ofTechnology (HUT) and the Energy Technology Department at theLappeenranta University of Technology (LUT). So far, fourmaster's theses, two SAE Papers and four Fisita Papers havebeen completed on the subject. Modern simulation tools, such asStar CD, GT-Power, Diesel RK and Chemkin have been used. Theprototype engine made its first start in December 2004 and testingof the engine has been made two years in a testbench.In the HCCI combustion simulation of the Z-engine, a4-dimensional ignition delay map, calculated with Chemkin andintegrated in Diesel RK, has been used. The simulations and testswith the test engine show that the Z-engine has a very goodefficiency, especially at part load. A HCCI combustion at all loadsis possible in the Z-engine, with lambda about 1,8-2,3 and EGR-rate10-40%, depending of the load. The TDC temperature at part load isabout 800 K and at full load (BMEP 27 bar) about 700 K. The HCCIignition, triggered with a pre chamber spark plug or small amountof fuel injection, occurs between 0°-20° ATDC and this limits thepressure and maximal temperature. No knock is present, as theignition occurs always at the right side of the NTC (negativetemperature coefficient) regime. NOx values are very low as themaximal temperature at full load is about 1900 K, because of thelow starting temperature of the combustion, intern EGR and theexpansion during the combustion. Intern EGR and active radicalsstabilize the combustion and lower the activation energy needed forthe ignition

Notes:

Vendor supplied data

Publisher Number:

2012-01-1573

Access Restriction:

Restricted for use by site license