HCCI engine researchers please provide the answer. Throttle losses are the major disadvantages to realize the HCCI engine concept using external mixture formation. Can we avoid this problem?
Its not possible, because HCCI requires a homogenous charge in cylinder. In HCCI, the composition of air - fuel mixture in cylinder has to fulfill two requirements: (1) the distribution must be homogeneous, that means that it is the same in every region of the combustion chamber. (2) It has to be in a certain ratio, which enables combustion. In this way, HCCI concepts need throttle for controlling engine operation at part load.
As a difference, there is a non-homogenous air - fuel mixture in diesel engines, because fuel is injected into compressed (hot) air. Due to this fact, diesel engines are controlled by the amount of injected fuel and do not require throttle control.
Kind regards,
Mario
Thank you sir,
But I am asking about the external mixture formation technique in HCCI mode of combustion where a fuel vaporizer is used to vaporize the fuel and a mixer is used to form a homogeneous mixture of air and fuel. For this purpose a long inlet manifold is used, but this is causing the throttle losses. My question is .. is there any method that can reduce these throttle losses ?
External mixture formation for HCCI needs more effort than those for standard SI engines, because the higher requirements on the mixture quality (it should be homogenous). Therefore, some technologies use long intake manifolds, which cause a certain loss due to flow resistances. One approach to reduce the lenght of these long pipes is to use two injection valves, one at the intake end of the pipe (e.g. in the airfilter box) and a second one closer to the cylinder. Depending on the engine operation mode, one injection valve or both come to use. Anyway, for part load operation, a throttle valve is obligatory, which restricts the charge-flow into the engine.
Kind regards,
Mario
Thank you Dr. Mario Hirz . Are tou working in the area of HCCI?
Not personally, but colleagues from the Institute of Internal Combustion Engines and Thermodynamics at Graz University of Technology do:
http://fvt.tugraz.at/index.php?option=com_content&view=article&id=71:mission-statement&catid=22:about-us&lang=en&Itemid=242
Kind regards,
Mario
- Badges
- Science topic
- Similar topics
- Physics