Toshio Kurabayashi

Effect of exhaust gas recirculation on diesel knock intensity and its mechanism

Abstract This paper presents an experimental study of the effect of exhaust gas recirculation (EGR) on diesel knock intensity, which is defined and discussed. In a previous paper, it was reported that particulate emission can be decreased by applying EGR under certain operating conditions; and the possible mechanism of the effect of EGR was presented. In the present study, the effect of EGR on diesel knock is examined under a variety of operating conditions. Diesel knock intensity is decreased considerably by EGR under the same operating conditions as when the particulate emission is decreased. A quantitative relationship between the diesel knock intensity and the maximum rate of cylinder pressure rise is obtained. The effect of EGR on diesel knock intensity is determined by both the chemical reaction rate of the initial premixed combustion (spontaneous ignition) and the fuel mass fraction prepared and burned in this stage. This is verified by measuring the ignition lag and classifying it into chemical and physical lags by a statistical technique presented by S. Kumagai.

Velocity and turbulence measurements in a combustion chamber of S.I. engine under motored and firing operations by L. D. A. with fiber-optic pick-up

In order to improve adaptability of the laser Doppler anemometer (LDA) to measurement of gas flow velocities in an internal combustion engine, an optical fiber system composed of a couple of single mode, polarization-preserving optical fibers has been developed to transmit the incident beams. The overall light transmission efficiency of the system is 24% and not so high, but the system enables real-time measurements of gas flow velocity in the combustion chamber of a small two-cycle engine during firing operation. The velocity data measured are processed with cycle by cycle analysis by stationary time-averaged method to obtain bulk velocity, turbulence intensity and integral time scale of turbulence.

Failure of Spray Droplets to Impact the Cylindrical Sampler in the Iipmersion Sampling Technique

The immersion sampling technique with a cylindrical rotary shutter is quite popular in measuring spray droplet sizes. However some problems with this technique remain unsettled. In this paper the extent to which droplets fail to impact the cylindrical rotary shutter is experimentally investigated. Experiments have been carried out using a steady water jet from a 0.2 mm hole nozzle varing the diameter of the cylindrical shutter from 22.5 mm to infinity (flat plate) and the sampling distance from 800 mm to 2, 300 mm.From the results obtained the following can be concluded:(1) Contrary to expectation, failure of droplets to impact is fairly rare.(2) Though failure to impact increases with an increase in shutter diameter, the rate of increase is very small after the shutter diameter exceeds about 30 mm.(3) Since failure to impact occurs over the whole range of droplet size, arithmetic and Sauter mean diameter and size distribution are not affected significantly by the existence of the rotary shutter.