G. P. Blair

REDUCTION OF FUEL CONSUMPTION OF A SPARK-IGNITION TWO-STROKE CYCLE ENGINE

The paper describes and lists the performance characteristics of a 400 cubic cm single-cylinder two-stroke cycle engine with natural-aspiration, spark-ignition and carburetter control of gasoline fuel. The engine features an uncomplicated and unique system of stratified-charging which helps reduce the short-circuited loss of fuel during scavenging. With an untuned exhaust system the engine produces a peak power of 13 kW at 5500 rev/min and a brake specific fuel consumption which has a minimum of 0.265 kg/kWh but, more importantly, virtually the entire speed and load range is below 0.34kg/kWh (0.55 lb/hp. hr). All performance characteristics at several throttle openings are presented at various engine speeds as a function of air/fuel ratio.

An Experimental Comparison of Loop and Cross Scavenging of the Two-Stroke Cycle Engine

In a previous paper the authors pointed out that the single-cycle gas simulation rig which they had developed would prove to be an invaluable experimental tool for the development of two-stroke cycle engine cylinders to attain better scavenging and trapping efficiency of the fresh charge. This paper reports on the use of that now proven experimental technique to examine one of the longest running, and hitherto unresolved, discussions in the field of small two-stroke cycle engines: is loop-scavenging really superior to cross-scavenging. All of the cross-scavenging tests in the paper are compared to tests conducted on loop-scavenged cylinders of the same basic geometry and which were reported previously to SAE. The main conclusion from the experimental investigation is that cross-scavenging is superior to loop-scavenging at low or modest scavenge ratios but is inferior at high scavenge ratios.

Further tests on reducing fuel consumption with a carburetted two-stroke cycle engine

This paper describes a unique and uncomplicated method of stratified-charging a two-stroke cycle engine which assists in reducing the short-circuited loss of fuel during scavenging. Performance characteristics as presented were acquired from tests conducted on a 400 cu cm naturally aspirated, single cylinder, spark ignition two-stroke engine with carburettor control of gasoline fuel, the design and construction of the engine also being done at The Queens University of Belfast. Using a tuned exhaust pipe, the engine produces a peak power of 16 kW at 5000 rev/min and has a minimum brake specific fuel consumption of 0.275 kg/kWh. Moreover, for the tests presented at full and quarter throttle openings, virtually all of the brake specific fuel consumption values are below 0.36 kg/kWh. Most of the performance characteristics shown at various engine speeds are as a function of air/fuel ratio. This paper is a continuation of that presented as SAE 830093.

Acceleration Test Method for a High Performance Two-Stroke Racing Engine

This paper describes an inertial dynamometer system which has been applied to the testing of small two-stroke kart racing engines. The dynamometer incorporates a flywheel of appropriate moment of inertia to simulate the mass of a kart and driver. The test procedure involves measurement of the flywheel speed during an acceleration phase resulting from opening the throttle. Calculation of the instantaneous flywheel acceleration corresponding to each engine speed directly gives a measure of the torque and power characteristics. Performance results, including exhaust pressure traces, are presented from a series of tests conducted on a 100 cm3 kart engine. The results are compared with corresponding steady state measurements recorded on an eddy current dynamometer. In addition, the measured results are compared with predictions from a computer simulation.

Predicting the Performance Characteristics of Twin-Cylinder Two- Stroke Cycle Engines for Outboard Motor Applications

This paper outlines the results of an investigation of twin cylinder engines of the outboard motor type where compact and complex exhaust systems are used to optimise the performance characteristics within a specified package size. Measured and predicted pressure-time histories for the exhaust and open cycle cylinder are presented for a 350 cm 3 , twin cylinder test engine, which has been extensively modified to emulate the porting configuration and performance characteristics of two production outboard motor engines

Initial Development of a Two-Stroke Cycle Diesel Engine for Automotive Applications

A three cylinder two-stroke cycle diesel engine is proposed for automotive use. The engine is of the simple loop or cross-scavenging type with a crosshead seal and under piston scavenging pump. This paper records the initial investigations of this concept using a purpose built single cylinder engine. Results from different combustion systems are presented together with tests with the same engine when using an external air supply. Measurements from a parallel investigation using a laser doppler anemometer to measure air swirl motion within one of the chambers are also presented.

Observations on the Design and Operation of Pulsejet Engines as Derived from an Experimental and Theoretical Investigation

This paper describes some of the experimental and theoretical work carried out at the Queens University, Belfast in connection with a pulsejet project. It starts from the earliest stages of trying to achieve a working reed valved engine and continues to the present where valveless pulsejets have been designed with the aid of a simulation program. Suggestions are made regarding the manner in which various parameters such as duct and intake geometry, orientation and flight speed can affect performance. It suggest four main criteria which must be fulfilled for any valveless pulsejet to operate successfully and discusses methods by which these can be achieved.