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Two-stroke engines are being utilized in large numbers as small utility, lawn and garden equipment engines. The following two subjects were examined with regards to exhaust emission control. The first subject was to compare the theoretical values of a combustion model simulation with the experimentally measured values of the base line emission of two-stroke volume as follows in detail. Considering high short-circuiting and residual gas characteristics peculiar to two-stroke engines, comparison analysis between measured exhaust emissions and calculated values by a thermodynamic combustion model simulation. Comparison analysis of the trapping efficiency-corrected HC, NOx, CO mass emission rates by the fuel flow and the fuel and air flow method. Analysis of influence to engine power and mass emission rates by the cylinder thermal load change with varing air-fuel ratio of the charge mixture.

This paper deals with a research project concerning an effective utilization of exhaust gas heat. Exhaust gas from a exhaust gas-separate type two-stroke cycle engine containing a high concentration of unburned gas was temporarily stored in a floating-bell type tank as an form of heat energy conservation, while in the previous report [1]* exhaust heat was recovered with continuous operation. A Stirling engine with a hot-water supply system was then used to oxidize or burn again the exhaust gas in a catalyzer and an after-burner unit in order to recover the unspent heat energy from the exhaust gas. A three-way catalyzer was employed to remove pollutants both from the combustion gas in this process and the high-concentration burned gas from the two-stroke cycle engine. The results of the research in the present paper are intended as a follow-up of the previous report [1] to clarify a method for the more effective use of exhaust gas heat.

Improvements in the engine performance, efficiency, scavenging, and emission characteristics of a modified two-stroke-cycle engine with the poppet valves and gaseous-fuel direct-injection system are described. In previous papers, SAE 901664 [1]* and 920180 [2], in which the scavenging characteristics were mainly investigated, the modified two-stroke-cycle engine was based on a production four-stroke-cycle engine. The base engine intake valve was used as scavenging valve, with a shroud installed for preventing the short-circuiting charge loss. As Shown in the previous results, considerable improvement of the scavenging efficiency was obtained. While a gasoline fuel carburetion system was used in the earlier engine [1], [2], the present engine used a propane gas direct-injection system, with the purposes of further decreasing fuel short-circuiting loss and also improving combustion preparation characteristics in terms of fuel atomization, vaporization and mixing with air.

This paper deals with the continued investigation of The scavenging and power characteristics of a two-stroke cycle gasoline engine with scavenging and exhaust valves in the cylinder head. Since this engine is reconstructed from a four-stroke cycle engine, its intake valves are used as the scavenging valves, and the scavenging of the cylinder consists of U-type flows. In the previous paper (SAE paper No. 901664), by setting up a deflector near the valve seat for each scavenging port, the study to prevent the scavenging gas short-circuit effect was conducted. As results in those test, by setting up the deflector within each scavenging port the scavenging effect and power characteristics were improved considerably. However, as the scavenging valve lift was increased, the effectiveness of the deflector decreased. The difference with or without the deflectors was only 10∼14% in scavenging efficiency, and only improvements of 5∼10% in charging efficiency were obtained.

This paper deals with a successful attempt to employ the exhaust gases of a two-stroke cycle gasoline engine as an energy source to operate an after burner and a Stirling engine, and to clean the exhaust gases by a catalyzer. By means of a rotary valve and the exhaust pipe sections, the exhaust gases could separated into a high concentration of fresh gas and a high concentration of combustion gas. The former gas was burned by a burner, and then used to heat a Stirling engine. The latter gas was disposed of by an oxidation catalyzer. The investigation revealed the enthalpy and exergy flows of a two-stroke cycle gasoline engine, a burner, a catalyzer and a Stirling engine, and then the emission gases (HC, CO, NO) were disposed of by the burner and catalyzer. The investigative analysis shows a method of successfully transferring the energy available in the exhaust gases for the combustion of a burner and the operation of a Stirling engine, a burner and a catalyzer.

A semiconductor capacitance -type accelerometer utilizing a pulse width modulation (PWM) electrostatic servo technique has been developed. Highly accurate detection of very small and low frequency acceleration became possible with the PWM sensing method. The limited air gaps between the movable and fixed electrodes ensured compatibility between high sensitivity and durability, while transverse sensitivity and temperature coefficient were reduced due to the symmetric structure of the sensing device. This sensor has been designed for the measurement range of 0 to ±1g, ±2g and 0 to 50Hz. The accelerometer is composed of two chips: the sensing device made by silicon micromachining technology and the custom IC made by bipolar CMOS technology. In this paper, we present the fundamental sensing principle, the sensing device, the custom IC and the characteristics of the new accelerometer.

This paper deals with an investigation of the scavenging and power performances of a two-stroke cycle gasoline engine having poppet valves in the cylinder head but no cylinder ports. In a previous experiment, a model test apparatus was used to carry out the experimental analysis of scavenging performance. We found as a result of this analysis that better scavenging efficiency could be obtained by improving the flow pattern of scavenging gas in the cylinder by means of scavenging valves with shroud than by perfect diffusion scavenging. The present experimental study using a real engine was conducted according to this finding. The basic engine is a four-stroke motorcycle engine, one cylinder, 250 cm3, twin-cam, four-valve. The engine was modified into a two-stroke cycle engine by altering the camshafts so as to have twice the engine speed of the four-stroke cycle engine, and the valve timings were adjusted by a pin that connected the camshaft and sprocket.

This paper deals with the separation of short-circuit gas from exhaust gas in a two-stroke cycle gasoline engine and the measures to effectively utilize the short-circuit gas. For trial manufacture of the engine, the slide shutter is kept on an open port, and is set on the upper plane of the piston. This is done in order to get control of the exhaust port. The piston moves up and down the side of the exhaust port, which is divided into 3 section areas: upper, middle and lower. This mechanism in the lower level was able to separate the fresh and burned gas concentrations, at a high level, from the exhaust gas. We succeeded in achieving a firing-run on a separated and set four-stroke cycle gasoline engine by taking advantage of this gas. The data include, among others, the relationship between the trial manufacture of the engine and the general purpose engine in performance, specific fuel consumption and emission gases.

This paper describes a radar sensor which is being developed as an adequate sensor for an inflatable occupant restraint system. The important characteristic of this radar sensor is that an optimum highly sensitive sensing zone is formed by the combination of two transmission antennas and two reception antennas in order to improve the collision judgment accuracy, minimize the difference of precollision time for various obstacles, and suppress the received signal level due to rain and snow, etc.