The engine knock analysis – An overview

Combustion advancements in gasoline engines

A gasoline-fueled homogeneous charge compression ignition (HCCI) engine with both direct fuel injection and negative valve overlap for exhaust gas retention was examined. The fuel was injected directly into the residual in-cylinder gas during the negative valve overlap interval for the purpose of reforming it by using the high temperature resulting from exhaust gas recompression. With this injection strategy, the HCCI combustion region was expanded dramatically without any increase in NOx emissions which were seen in the case of compression stroke injection. Injection timing during the negative valve overlap was found to be an important parameter that affects the HCCI region width. The injection timing also had the most suitable value in each engine'load for the best fuel consumption. From this result, A new injection strategy in which only a portion of the fuel was injected during the negative valve overlap interval, while the rest of fuel was injected in intake stroke, was proposed. With this split injection, by selecting the suitable amounts of fuel, further fuel consumption improvement was realized. The higher the engine load becomes, the less amount of fuel injected during negative valve overlap was required for the suitable HCCI combustion. Finally, the advantage of utilizing the combination of the negative valve overlap and the direct fuel injection in expanding HCCI operating region was summarized in a figure as contours of required negative valve overlap interval on engine speed and compression ratio plane. The effect of mixture stratification and the effect of fuel reformation can be utilized to reduce the required negative valve overlap interval for suitable HCCI combustion under each set of engine speed and compression ratio conditions.

Expansion of HCCI Operating Region by the Combination of Direct Fuel Injection, Negative Valve Overlap and Internal Fuel Reformation

At present achieving fuel economy and reducing emissions are the two main targets set by the automotive industries. Homogeneous charge compression ignition (HCCI) technology is believed to be a promising one to be applied in both spark ignition (SI) and compression ignition (CI) engines in the near future. However, some challenges such as compromise combustion phase control, controlled auto-ignition, operating range, homogeneous charge preparation, cold start and emissions of unburned hydro carbon (UHC), and carbon monoxide (CO) need to be overcome for successful operation of HCCI engine. Extensive research on HCCI combustion with a homogeneous fuel–air mixture preparation is going on throughout the world. This paper reviews the strategies of different external and in-cylinder mixture preparation methods which were adopted and proposed in the recent years. The different strategies of controlled auto-ignition by HCCI combustion are also discussed in this paper.

Homogeneous charge compression ignition (HCCI) combustion: Mixture preparation and control strategies in diesel engines

In a spark ignition type internal combustion engine that includes a variable compression ratio mechanism A capable of changing the mechanical compression ratio, and a variable valve mechanism B capable of changing valve characteristics of an intake valve or an exhaust valve, the variable valve mechanism is mechanically coupled to the variable compression ratio mechanism, and the variable valve mechanism is controlled in accordance with the compression ratio-changing operation amount of the variable compression ratio mechanism. The variable valve mechanism is coupled to the variable compression ratio mechanism without intervention of an electronic control unit. Therefore, the possibility of the interference between a piston and an intake valve resulting from an abnormality in a control system that includes an electronic control unit as an intervening unit can be eliminated.

Spark ignition type internal combustion engine

A Study on Gasoline Fueled Compression Ignition Engine ∼ A Trial of Operation Region Expansion ∼

Stroke cycles of a self-igniting gasoline engine (10) comprising an intake stroke, compression stroke, power stroke and exhaust stroke are performed sequentially by a piston (12), and self ignition of the fuel mixture is performed by compression of the fuel mixture in the compression stroke. The strokes of the piston (12) are detected by a sensor (23), and an electronic control unit (1) controls a valve timing adjustment mechanism (15, 18) so that a sealed period occurs when both an exhaust valve (17) and intake valve (14) are closed in the vicinity of top dead center of the exhaust stroke. The electronic control unit (1) also controls the fuel injection timing of a fuel injector (19) so that fuel is injected into the combustion chamber (11) during the sealed period. The fuel injected into the hot gas in the sealed combustion chamber (11) causes pre-combustion reactions, and thereby modifies the gasoline composition to a more reactive composition containing aldehydes so that compression self-ignition occurs easily.

Compression self-igniting gasoline engine

In a compression self-ignition gasoline internal combustion engine, a fuel injector through which a gasoline fuel is injected uninterruptedly within a combustion chamber of an engine cylinder is provided, a mixture of air and gasoline fuel within the combustion chamber is self-ignited through a compression action of a piston, an intake valve an open timing of the intake valve is set to a mid-way point through a suction stroke of the piston, a closure timing of an exhaust valve is set to a mid-way point through an exhaust stroke thereof, and gasoline fuel injection timing and quantity per combustion cycle injected through the fuel injector is controlled in such a manner that a first gasoline fuel injection is set during a minus valve overlap time interval during which both of exhaust and intake valves are closed and a second gasoline fuel injection is set during at least one of the suction stroke and the subsequent compression stroke.

Compression self-ignition gasoline internal combustion engine

Development of Transient Knock Prediction Technique by Using a Zero-Dimensional Knocking Simulation with Chemical Kinetics

A method and system for controlling an auto-ignition in an internal combustion engine, comprises setting the closing timing of an outlet control device of a cylinder increasingly before or ahead a top dead center (TDC) during the exhaust stroke with the decreasing engine loads at the rate of a change in the closing timing per a unit change in the decreasing engine loads. This change in the closing timing increases with the decreasing engine loads. The opening timing of an inlet control device of the cylinder is set after the TDC.

Kazuya Hasegawa

Papers

A Study on Gasoline Fueled Compression Ignition Engine ∼ A Trial of Operation Region Expansion ∼

Compression self-igniting gasoline engine

Compression self-ignition gasoline internal combustion engine

Development of Transient Knock Prediction Technique by Using a Zero-Dimensional Knocking Simulation with Chemical Kinetics

Method and system for controlling auto-ignition in an internal combustion engine