Seita Isshiki

Theoretical and experimental study on regenerative rotary displacer Stirling engine

Recently a quite new type of hot air engine called rotary displacer engine, in which the displacer is a rotating disk enclosed in a cylinder, has been conceived and developed. The working gas, contained in a notch excavated in the disk, is heated and cooled alternately, on account of the heat transferred through the enclosing cylinder that is heated at one side and cooled at the opposite one. The gas temperature oscillations cause the pressure fluctuations that obtain mechanical power acting on a power piston. In order to attempt to increase the performances for this kind of engine, the authors propose three different regeneration methods. Experimental results with and without regeneration are reported comparatively with a detailed description of the unity. A basic explanation of the working principle of this engine and a theoretical analysis investigating the main influential parameters for the regenerative effect are done. This new rotating displacer Stirling engines, for their simplicity, are expected to attain high rotational speed especially for suitable applications.

Measurement on Nusselt number of regenerator wire meshes by cylindrical probe

The regenerator is an important element in Stirling engines. As a regenerator element, a fire-hardened layer of wire mesh became popular for Stirling engines. However, such a mesh is expensive. Recently, a packed wire mesh has been used widely in Japan, but its basic performance, such as flow resistance and heat transfer ratio, has yet to be clarified. In the present study, a new method to estimate the Nusselt number of wire meshes in oscillating flow is proposed and reported. This method employs a cylindrical probe having two thermocouples in the axis symmetry direction. The present method has a feature that temperature variation in oscillating flow conditions can be estimated without expensive instruments for unsteady measurements. It became clear that the measured Nusselt numbers of usual meshes are from 45% lower to 30% higher than the empirical equations of previous studies. The Nusselt number of the packed wire mesh became about 1/6 of the equivalent layer of a usual mesh. These results shows that a rough estimation of performance of heat transfer is possible by the present method.

Regenerative rotary displacer Stirling engine

A few rotary displacer Stirling engines whose displacers have one gas pocket space at one side, and rotate in a main enclosed cylinder, which is heated from one side and cooled from the opposite side without any regenerator have been tried and studied for a considerable time by the authors. They then tried to improve this engine by equipping them with regenerators, because without regenerators, pressure oscillation and efficiency are insufficient. Here, several types of regenerative rotary displacer piston Stirling engines are proposed. One is the contra-rotating tandem two disc-type displacer engine, using axial heat conduction through side walls or by heat pipes and the other are single disc-types with circulating fluid regenerators or heat pipes. A contra-rotating type engine has been manufactured and experimented upon in order to assess the effect of the regenerators. Here, experimental results of an original rotary displacer Stirling engine without a regenerator and a contra-rotating tandem displacer engine with a side wall regenerator using axial heat conduction are reported, accompanied by many discussions.

Stirling Air Cycle Silent Emergency Home (APU) Auxiliary Electric Power Concepts: Novel Six Cylinder Single Acting Isshiki Z-Crank and a Free Piston Option

This is part two 01 of an ongoing re evaluation study of Stirling engines funded jointly by Professor Isshiki, Japanese Industry, and The Censors Foundation USA. The specific goal of this paper is to re-visit and re-examine the simplest and least costly mechanical configurations of the Stirling cycle engine. Ordinary atmospheric or compressed air is to be the working fluid. Long term durability and efficiency issues such as material creep strength, fatigue life, and thermal efficiency are secondary considerations. The contemplated service life duty cycle in the emergency home APU application is on the order of days to weeks per year. This is in sharp contrast with the current space power duty cycle on the order of 14 years continuous unattended service life. Consequently, costly sophisticated materials features of the highly developed Space application Stirling engines can be re evaluated. In this paper, the authors studied two mechanical configuration candidates. One, a novel single acting six-cylinder barrel Isshiki Z-crank engine. Two, the opposed mirror image arrangement of two synchronous free piston Stirling engines. Public utility consumer gas and/or CNG compressed natural gas and/or LPG liquid petroleum gas are fuel supply options in addition to emergency charcoal energy in Japan. The design goal is a 1 kW electrical output. Furthermore, silent operation and/or very low noise levels are a required feature to meet new contemplated more stringent local residential noise ordinance regulations in the United States. Low cost Stirling engines may best satisfy these design goals; and a business model goal to create uncontested market space, to render competition from existing open cycle internal combustion engine home emergency APUs’ irrelevant.

Visual measurement of flow rates for falling droplets from a capillary tube

The paper deals with the flow control and measurement of liquids that form droplets. An experimental investigation on the mass of the falling droplet from capillary tubes was carried out. Examples where the present study is considered useful are in the measurement of injection flow rates of fuel in a diesel engine and for flow measurement of drops from capillary tubes in medicine. In this investigation the capillary tubes used were made of brass and Bakelite material. The inner diameter of each tubes was kept constant at 1 mm and outer diameter tubes were changed from 2 mm to 5 mm in accordance with the variation in the liquid surface tension. Experiments on falling droplet of distilled water and methyl alcohol were also carried out, as the surface tension of these liquids are so very different. The experiments were performed using a visualization technique. The present paper discusses the effect of tube diameter, droplet size and physical property of liquid on the phenomena of a falling droplet.

An experimental study on flow resistance of regenerator wire meshes in oscillatory flow [in Stirling engines]

This paper describes the experimental results on fluid motion in regenerator wire meshes of a Stirling engine in a oscillatory flow. Theoretical analysis on laminar flow in a circular pipe is described for comparison. Simultaneous measurements of velocity nearby the mesh layer in the test section, pressure drops between the entry and exit points of the mesh layer and a photo signal of the top position of the piston were carried out under oscillatory flow conditions. Experimental result shows that variation of pressure drops slightly advances toward velocity variation as is clarified in the theoretical analysis on laminar oscillatory flow in a circular pipe. Friction factors, defined by adjusting the phase angle shift between pressure drops and velocity variations, show that it appears larger in the accelerating period than in the decelerating period. This phenomenon seems to be explained because fluid motion requires more energy to make an eddy structure in the accelerating period, while fluid motion in the decelerating period requires less energy as a streamwise eddy structure is already developed.

Seikan tunnel electric train propulsion regenerative energy management

The mission was to model the electric propulsion and regenerative energy requirements for the Kaikyo passenger train and the Kamolsusen freight train system currently operating between Tappikaitei and Yoshiokakaitei through the Seikan tunnel under the Pacific ocean. The Seikan tunnel is over 54 km in length and connects Aomori on the main Japanese island of Honshu to the North island of Hokkaido. Further, over 24 km of the Seikan tunnel is 100 meters below the sea bed of the Tsugaru Strait which joins the Pacific with the Sea of Japan. While, the sea bed is 140 meters below the mean Pacific sea level, at the deepest point. Safety and energy conservation issues led to reliable regenerative energy recovery and braking systems.