HCCI Seminar Report | Download

ABSTRACT
HCCI stands for Homogeneous Charge Compression Ignition. Homogeneous charge compression ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction releases energy that can be transformed in an engine into work and heat. HCCI combustion can substantially reduce NOx and soot emissions of diesel engines. 
HCCI Engine Seminar report pdf
However it is hard for diesel HCCI to obtain the same level of fuel economy as traditional diesel engines. HCCI lacks an easily identified combustion trigger and, when achieved via variable valve actuation (VVA), includes cycle-to-cycle coupling through the exhaust gas. This makes controlling the process decidedly non-trivial. To address these issues, the development of a closed-loop controller for HCCI combustion phasing and peak pressure was outlined. Results from both simulation and experiment show that cycle-to-cycle control of VVA-induced HCCI can be achieved using this physics-based approach. Correct combustion timing is crucial for proper engine performance in a Homogeneous Charge Compression Ignition (HCCI) engine. To stabilize unstable operating points, reject system disturbances and enable set point changes, it is necessary to use a combustion timing controller. In this, variable valve timing was used to control combustion timing, optimising fuel systems By means of the variable valve timing, residual gases were captured in cylinder to facilitate combustion timing control.The Internal Combustion (IC) Engine is perhaps the most wide-spread apparatus for transforming liquid and gaseous fuel to useful mechanical work. The reason why it’s so well accepted can be explained by its overall appearance regarding properties like performance, economy, durability, controllability but also the lack of other competitive alternatives. The demand for reduced fuel consumption and increased efficiency becomes more important when the fuel prices are rising. Lately the greenhouse effect has set new challenges to further increase the efficiency of the internal combustion engine. Increased environmental concern has focused more and more on the released exhaust pollutants from engines. The dream of every engine designer is to find a combination of the diesel engine and the spark ignited engine that only inherit the good properties of the diesel and SI engine i.e. efficiency like a diesel engine and exhaust emissions that are as clean as from the SI engine, or at least possible to after-treat to the same level. This can be reached with Homogeneous Charge Compression Ignition (HCCI). HCCI combustion was first applied to two-stroke engines, with improvement in fuel efficiency and combustion stability. When HCCI as applied to the four-stroke engine, the fuel efficiency could be improved up to 50 % compared to the SI engine.

Advantages of HCCI

  • Since HCCI engines are fuel-lean, they can operate at diesel-like compression ratios (>15), thus achieving 30% higher efficiencies than conventional SI gasoline engines.
  • Homogeneous mixing of fuel and air leads to cleaner combustion and lower emissions. Because peak temperatures are significantly lower than in typical SI engines, NOx levels are almost negligible. Additionally, the technique does not produce soot.
  • HCCI engines can operate on gasoline, diesel fuel, and most alternative fuels.
  • HCCI avoids throttle losses, which further improves efficiency

Disdvantages of HCCI

  • Achieving cold start capability.
  • High heat release and pressure rise rates contribute to engine wear.
  • Autoignition is difficult to control, unlike the ignition event in SI and diesel engines, which are controlled by spark plugs and in-cylinder fuel injectors, respectively.
  • HCCI engines have a small power range, constrained at low loads by lean flammability limits and high loads by in-cylinder pressure restrictions.
  • Carbon monoxide (CO) and hydrocarbon (HC) pre-catalyst emissions are higher than a typical spark ignition engine, caused by incomplete oxidation (due to the rapid combustion event and low in-cylinder temperatures) and trapped crevice gases, respectively.

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