Shinsuke Ono

Initiation of Combustion in Lean Mixtures by Flame Jets

Flame jets produced by Pulsed Combustion Jet (PCJ) systems are particularly suited for initiating combustion in lean fuel-air mixtures. Presented here is a detailed investigation of performance characteristics of a PCJ system. The progress of combustion in the cavity of a generator was observed by schlieren photography of the events occurring in the interior of a rectangular cavity simulator fitted with transparent windows. Electric properties of the jet plume were measured by an electrostatic probe. Schlieren photographs revealed that products of combustion are discharged through the orifice before the combustion process can spread throughout the volume of the cavity. Signals of the electrostatic probe showed that ejection of incomplete combustion products from the cavity is principally governed by the duration of spark discharge. In the jet, the exothermic process decays at first and then becomes reestablished inside large scale vortex structures in the jet plume.

Performance of pulsed combustion jet at high pressures and temperatures

Abstract Ignition and combustion by Pulsed Combustion Jet (PCJ) at high pressures and temperatures were investigated using a compact rapid compression machine. The compression and stop motion of a compression piston in the rapid compression machine is controlled by the cam shape, and the cam is operated by a driving piston and compressed air. The combustion process was monitored by pressure measurements and high-speed schlieren photography. Lean limit of methane-air mixture was extended by PCJ, and the superiority of PCJ over standard spark ignition was demonstrated in enhancing the process of combustion in turbulent lean mixtures.

Plasma jet ignition in turbulent lean mixtures

In order to confirm quantitatively the performance and characteristics of the plasma jet ignition in turbulent lean mixtures, combustion tests were carried out in a disk-shaped combustion chamber with lean turbulent methane-air mixtures. In the tests, the governing parameters of the plasma jet ignition such as the plasma cavity size, the orifice diameter, and the discharge energy were varied. In this paper characteristic lifetime and a characteristic length of the plasma jet and an entrainment volume of the mixture into the plasma jet is defined theoretically and expressed by the parameters of the plasma jet ignition.

PREDICTION OF IN-CYLINDER GAS MOTION IN ENGINES BY AN ENERGY METHOD.

A simple new method to predict in-cylinder gas motion during the compression stroke is presented for both flat piston and bowl-in-piston type combustion chambers. The method is principally based on the decay law of kinetic energy of the gas flow in an engine cylinder. Comparison of predicted and measured values shows fairly good agreement for different engine variables. Calculations for a flat piston type combustion chamber show that the velocity at TDC (top dead center) varies proportionally to the 1.15th power of the engine speed and to the -0.50th power of the compression ratio (CR). For the bowl-in-piston type combustion chamber, the ratio of the velocity in the bowl at TDC to that at the intake valve closure increases with a decrease in the CR, initial velocity, height of the bump clearance, and combustion bowl diameter, and with an increase in the engine speed.

Flame Extinction Behaviors in the Centrifugal Force Environment

By making use of the rotary cylinder combustion device which rotates with the combustible mixture in it, the real effects of the centrifugal force environment in the solid vortex on the flame behaviors are examined. The observed results show the enhanc-ed combustion by the swirl is not always expected, because of the rapid motion of a flame kernel to the swirl center, and the laminarization of turbulent flame. The propaga-tion speed of the flame initiated near the swirl center is considerably reduced, and in some cases, depending on the flame structure, vanishes to extinguish the flame.

An Experimental Study on the Fuel Spray Distribution and Combustion Characteristics in a Diesel Engine with Side-Injection System

The fuel spray distribution and combustion characteristics in side-injection system have been investigated by making use of the special test engine equipped with a variable angle swirler. As the results of experiments, following items have been clarified. In side-injection system, higher swirl intensity is necessary at combustion stage than central-injection system. Therefore the swirl acceleration by piston bowl during compression stroke is effective to improve the combustion characteristics. For the optimization of combustion system, it is important to find out the optimum combination of shape of combustion chamber and initial swirl intensity. When the residual fuel is used, optimization of sharp of combustion chamber becomes more important. For example, spherical bowl type combustion chamber can achieve better specific fuel consumption with smaller initial swirl intensity than flat-bottom bowl type.

On the Load Carrying Capacity of Crosshead-pin Bearing with Eccentric Journal

This paper refers to a new investigation to improve the load carrying capacity of the crossheadpin bearing in a 2-stroke cycle diesel engine. By using a specially equipped journal with a pair of eccentric sections the oscillating bearing can be forced to move up and down just like a piston-pin bearing in a 4-stroke cycle engine. Such a squeeze motion of the oil-film between a journal and a bearing has an ability to increase the oil-film thickness. Then, from the theoretical analyses on effects of various bearing shapes the following features and optimums for design became evident.(1) According to the change of an oscillating direction each sliding face is alternatively unloaded and the oil-pumping ability is generated.(2) In order to keep the oil-film pressure lower than the elastic flow pressure of a bearing metal and make the oil-film thickness as large as possible the next designing points are needed.(i) The ratio of a radial clearance to the radius is about 5 × 10-4 .(ii) The eccentricity between journals is as large as the radial clearance.(iii) The width ratio of a main journal to the whole bearing is about 0.7.