Multi-mode 2-stroke/4-stroke internal combustion engine

Abstract

In a multi-mode, 2-stroke / 4-stroke internal combustion engine operation, by switching the engine stroke from 4-stroke operation to 2-stroke operation so that the combustion frequency is doubled, doubling of the engine power is achieved even at the same work output per cycle. In order to meet the demand of extremely high power, the engine operates in 4-stroke boosted SI operation transitioned from 2-stroke HCCI operation at pre-set level of power and crank speed requirements. By combining the multi-stroke (2-stroke HCCI and 4-stroke HCCI) and multi-mode operation (2-stroke HCCI and 4-stroke boosted SI operation), full load range and overall high efficiency with minimal NOx emission are achieved.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a multi-mode, 2-stroke / 4-stroke internal combustion engine operation which maximizes efficiency and power, while minimizing emission.[0003]2. Description of Related Art[0004]Spark Ignition (SI) engines, which are widely used in United States in passenger vehicles, suffer from low efficiency in comparison to Compression Ignition (CI), or Diesel engines, especially in a partial load due to throttling. CI engines, however, exhibit high particulate and NOx emissions characteristics due to their combustion nature. Recently, Homogeneous Charge Compression Ignition (HCCI) engines have been introduced, which have higher efficiency comparable to CI engines as well as minimum particulate and NOx emissions characteristics, with the versatility of using gasoline as well as diesel fuel.[0005]In HCCI engines, a spark plug or a high-pressure injector is not used for initiation of the ignition of the fu...

AI Technical Summary

Benefits of technology

The present invention provides an internal combustion engine that can achieve a wide load range of HCCI operation without sacrificing efficiency and emissions advantages. The engine can switch between 2-stroke and 4-stroke operation to double the power output and achieve high efficiency in both load ranges. The stroke switching is simpler and smoother than mode switching and requires less modifications to the engine. The engine operates on 4S boosted SI transitioned from 2S HCCI at pre-set level of power and crank speed requirements, allowing for full controllability on smooth transition from 2S HCCI to 4S boosted SI. The combination of multi-stroke and multi-mode operation allows for full load range and overall high efficiency with minimal NOx emission compared to conventional strategies.

Problems solved by technology

Spark Ignition (SI) engines, which are widely used in United States in passenger vehicles, suffer from low efficiency in comparison to Compression Ignition (CI), or Diesel engines, especially in a partial load due to throttling.

CI engines, however, exhibit high particulate and NOx emissions characteristics due to their combustion nature.

However, the limited work output is one of the major challenges in HCCI operation, which limitation is caused by the high dilution of mixture in the cylinder.

The dilution with hot exhaust gas is not only required to increase the mixture temperature to achieve auto-ignition, but also required to limit the high rate of pressure rise, which otherwise would be destructive to the engine components.

However, in this case, the emission and efficiency benefits of HCCI operation are lost in the medium to high load range, and the transient combustion control of HCCI in mode switching is not a subtle issue in current research and industries.

Secondly, boosted HCCI may give higher power, but it is also limited since the combustion becomes too noisy and destructive due to the high rate of pressure rise from rapid burn rate.

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