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THE rotary engine, first introduced in automobiles, may be the engine of choice for business and commuter aircraft in the early 1990s.

AVCO Lycoming Williamsport Division and John Deere Technologies International (JDTI) today announced an agreement to jointly develop a stratified charge, turbocharged rotary engine for general aviation which will burn jet fuel or other alternative fuels.

SMALL surface cracks in some cast pistons are often present from the date of manufacture, and are due to the casting stresses in the uneven sections. Provided the piston is not subject to considerable distortion in service, these cooling cracks do not increase or lead to failure by fatigue. Actual experience of the design is necessary, however, before a decision can be given as to the safety of a cracked piston, and it must be remembered that the holder of a “C” licence may not have the facilities for so careful an examination of the piston during top overhaul.

This paper aims to present experimental results of gasoline-fuelled engine operation of a crankcase-scavenged two-stroke cycle engine used for unmanned air vehicle (UAV)/unmanned air system application and to cross correlate with computational fluid dynamic modelling results.

Computational modelling of the engine system was conducted using the WAVE software supported by the experimental research and development via dynamometer testing of a spark ignition UAV engine to construct a validated computational model exploring a range of fuel delivery options.

Experimental test data and computational simulation have allowed an assessment of the potential advantages of applying direct in-cylinder fuel injection.

The ability to increase system efficiency offers significant advantages in terms of maximising limited resources and extending mission duration capabilities. The computational simulation and validation via experimental test experience provides a means of assessment of possibilities that are costly to explore experimentally and offers added confidence to be able to investigate possibilities for the development of similar future engine designs.

The software code used has not been applied to such crankcase-scavenged two-stroke cycle engines and provides a valuable facility for further simulation of the twin cylinder horizontally opposed design to offer further system optimisation and exploration of future possibilities.

To the Editor. DEAR SIR, In the June issue of AIRCRAFT ENGINEERING, Mr V. D. Naylor rightly asserts that, according to one‐dimensional theory, the velocity at the throat of a Laval nozzle is the local sonic velocity, whether friction is present or not. However his proof rests on an expansion law pvn=constant, when n≠y, and the throat velocity which he obtains differs according to the value of n. Both the assumption and the conclusion are false. The confusion which has existed on this point is, therefore, deepened.

The importance of effective laboratory work in mechanical engineering courses cannot be over‐emphasised. Firstly, laboratory work normally occupies about one third of the time in undergraduate and Higher National Certificate courses. Secondly, the laboratory building, experimental equipment and the time spent by academic staff and technicians in laboratory classes results in a substantial financial commitment. The need to spend this time and money wisely suggests a continuing demand for critical appraisal of the aims and practice of laboratory work. Further, there is a need to examine the design and layout of the laboratories themselves, and some literature has appeared in this field.

IN the earliest stages of the development of the aeroplane the speed range obtainable was small, flight occurred only at fairly high lift coefficients, and induced drag was the predominant component of total resistance, hence successful flight depended on the achievement rather of minimum weight, minimum wing loading and maximum engine power than on the achievement of minimum possible parasite resistance.

THE history of aviation engines shows that most of the important pioneering in design has been done, with a few notable exceptions, by the United States. Research on all related problems and even empirical methods have been tried again and again, until each detail was worked out towards the betterment of a particular engine. Despite long and sometimes vociferous patent disagreements, progress has been on the whole satisfactory. We can see how the accomplishments of our various aviation engines, sturdy and non‐spectacular during the war, quite spectacular and reliable in the boom period since 1927, are directly the result of painstaking and quiet research on the part of metallurgists, fuel experts, cooling investigators, ignition experimenters, designers, dabblers in oil and now and then a mechanic. In a word, the whole history of engines is to be found in the elimination or addition of details—details of design.

IN all sciences and industries progress has soundly and steadily been maintained as knowledge and experience has been accumulated.

This paper aims to investigate the effect of frictional heat on the wear of high-speed rotary lip seals in engines.

In this research paper, the authors focus on the high-speed rotating lip seal of aircraft engines. Using the hybrid lubrication theory, a thermal-fluid-solid coupled numerical simulation model is established to investigate the influence of parameters such as contact pressure distribution, temperature rise and leakage rate on the sealing performance under different operating conditions. By incorporating the Rhee wear theory and combining simulation results with experimental data, a method for predicting the wear of the rotating seal lip profile is proposed. Experimental validation is conducted using a high-speed rotating test rig.

The results indicate that as the speed increases, the rise in frictional heat leads to a decrease in the sealing performance of the lip seal contact region. The experimental results show a similar trend to the numerical simulation results, and considering the effect of frictional heat, the predicted wear of the lip seal profile aligns more closely with the actual wear curve. This highlights the importance of considering the influence of frictional heat in the analysis of rotating seal mechanisms.

This study provides a reference for the prediction of wear profiles of engine high-speed rotary lip seals.