To produce a good mixing or homogeneous air and fuel in combustion-chamber of spark Ignition Engines are needed a strong turbulence intensity. And to obtain a strong turbulence intensity, the flow of a swirling jet in the combustion-chamber is needed.
The flow of swirling jet was presented by a nondimensional swirl number, which can be derived from NAVTER STOKES equations and presented as a theoritical solution in this dissertation. Analysis showed that the stronger the swirl the higher the swirl-number is.
Before experiment starting with a moving transparent glass cylinder model of SI-Engine, the basic experiments have been done and presented in Chapter-III. The results obtained in this basic experiment have expressed many important fact, especially the boundary conditions and characteristics of free jet, confined jet, swirling jet and confined swirling jet.
The meaning of confined jet and confined swirling jet are the flow of a jet or a swirling jet which are limited by cylindrical wall.
Analysis of this basic experiment showed that the radial distributions of velocity components for free jet and swirling jet should vary asymptotically as (x-x0) and (x- x0), respectively. Whereas the influence of round obstacle which is placed near the orifice showed that the farther the distance from orifice the lower the influence of round obstacle and disappeared after a certain distance from the orifice. Its also showed that it is not necessary to work with two velocities, one is sufficient. For nondimensional radial distribution of velocity ratio, to be found by dividing the value of velocity components with the mean original velocity, then expressed the similarity of velocity distribution graphs, although the original velocities from the orifice were not the same. Velocity distributions along jet axis in a confined jet are higher than a free jet. The turbulence conditions in this experiment showed that a confined jet in cylindrical tube tend to increase as compared to a free jet. Likewise for a confined swirling jet in cylinder, the turbulence intensity is higher than a swirling jet. The basic experiment also showed that the increase in temperature can help to increase the turbulence intensity for a free jet and swirling jet, with and without cylinder.
Many informations from this basic experiment can be used as references to analyse the result data in the next experiment, which will be presented in Chapter-IV, i.e. experiment of confined jet and confined swirling jet in cylinder of SI—Engine.
To obtain a swirling jet, then the air goes into the inlet port of combustion-chamber through the valve with several blades on it. These blades can be put also in the orifice (manifold) near the exit hole.
Experimental investigation was done with several configuration, viz., blades inclination, blades number, blades location, valve lift position and valve position from the axis, to obtain the best turbulence intensity. The experiment results showed that:
1. Velocity distribution and turbulence intensity distribution in a confined swirling jet in cylinder was influenced by the wire probe position', but for confined jet without swirl, the velocity distributions are not influenced by wire probe position.
2. Shifting the valve axis from the jet axis, also shift the radial distribution of velocity, then all the turbulence intensity will be changed. The shifting of this valve increased the turbulence intensity.
3. The change of blades numbers influenced the velocity distribution. Experiment result showed that the number of blades on the valve of more or less than 6(six), can be decreasing the turbulence intensity.
4. In this experiment, two kind of blades inclination were used, 30 and 60. The results showed that the best turbulence intensity was given by the valve with 60° of blades inclination.
5. The valve lift position can influence the velocity distributions and turbulence distributions, then the higher of valve lift position, the lower of turbulence intensity.
6. Increasing the temperature can increase the turbulence intensity, similar to what will be shown in chapter-III.
Measurements for valve without blades, without swirl and with swirl which is generated by helical port were also done in this experiment. Then the results were compared with "swirl blades valve" results. This experiment showed that the best turbulence intensity result was given by "swirl blades valve". |