HCCI-Combustion in the Z Engine

Format:

Conference/Event

Author/Creator:

Janhunen, Janhunen, author.

Conference Name:

SAE 2012 World Congress & Exhibition (2012-04-24 : Detroit, Michigan, United States)

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 the customacceptance, because of the fact, that the car drives are used tothe 4-cylinder engine and they want to have the same driving funalso from the new engines. A 2-cylinder 2-stroke engine has thesame power output and torque as a 4-cylinder 4-stroke engine andthus it offers the same driving fun. Equal balancing is easy tomake without some big additional costs, if the gas exchange of theengine is made by using poppet valves and camshafts. As there areonly about 70% of the moving parts in the engine, its accelerationis even better than by a 4-cylinder engine.One of the latest development 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, aHCCI-combustion is possible in the Z-engine at all loads. Thislowers significantly the cost of the engine, as no urea injection,or NOx catalyst is needed to pass the coming EU-6 emission norm.The cost of the Z-engine is lower also because of the fact that ithas only 2 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:

2012-01-1132

Access Restriction:

Restricted for use by site license