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THE problem of silencing the exhaust of a piston engine requires that attention be given to the two main sources of gas noise; firstly, relatively low frequency vibrations in the exhaust column itself, excited by a pressure pulse produced by the rapid rush of gas from the cylinder into the exhaust pipe, and, secondly, high frequency vibrations resulting from eddies in the gas stream.

Development or upgradation of airplanes requires many different analyses, e.g. thermal, aerodynamic, structural and safety. Similar studies were performed during configuration change design of commuter category aircraft equipped with pusher turboprop engines. In this paper, thermo-fluid analyses of interactions of the new propulsion system in tractor configuration with selected elements of airplane skin are carried out. This study aims to check the airplane skin material, and its geometry, including the Plexiglas passenger window material degradation, due to hot exhaust gas plume impingement. The impact of change in exhaust stub angle and asymmetric inboard-outboard stubs on the jet thrust at various flight operating conditions like minimum off-route altitude and cruise performance is assessed.

Commercial software-based numerical models were developed. In the first stage, heat and fluid flow analysis was performed over a twin-engine airplane’s nacelle, wing and center fuselage with its powerplant mounted in the high wing configuration. Subsequently, numerical simulations of thermal interactions between the hot exhaust gases, which leave the exhaust system close to the nacelle, flaps and the center fuselage, were estimated for various combinations of exhaust stub angles with asymmetry between inboard-outboard stubs at different airplane configurations and operating conditions.

The results of the simulations are used to recommend modifications to the design of the considered airplane in terms of material selection and/or special coatings. The importance and impact of exhaust jet thrust on the overall aircraft performance are investigated.

The advanced numerical model for the exhaust jet-airplane skin thermal interaction was developed to estimate the temperature effects on the propeller blades and aircraft fuselage surfaces during different flight operating conditions with multiple combinations of stub orientations.

This study seeks the effect on static thrust, thrust specific energy consumption (TSEC) and exhaust emissions of euro diesel-hydrogen dual-fuel combustion in a small turbojet engine.

Experimental studies are performed in a JetCat P80-SE type small turbojet engine. Euro diesel and hydrogen is fed through two different inlets in a common rail distributing fuel to the nozzles. Euro diesel fuel is fed by a liquid fuel pump to the engine, while hydrogen is fed by a fuel-line with a pressure of 5 bars from a gas cylinder with a pressure of approximately 200 bars.

At different engine speeds, it is found that there is a decrease at the TSEC between a range of 1% and 4.8% by different hydrogen energy fractions (HEF).

The amount of hydrogen is adjusted corresponding to a range of 0–20% of the total heat energy of the euro diesel and hydrogen fuels. The small turbojet engine is operated between a range of 35,000 and 95,000 rpm engine speeds.

On the other hand, remarkable improvements in exhaust emissions (i.e. CO, CO₂, HC and NO_x) are observed with HEFs.

This is through providing improvements in performance and exhaust emissions using hydrogen as an alternative to conventional jet fuel in gas turbine engines.

EXHAUST smoke emission from high pressure ratio aero gas turbine engines currently in service has been reduced largely by attention to fuel air mixing in the combustion chamber. It is demonstrated that aerated fuel sprays provide the additional control required as pressure ratios increase still further on new engines. The proportion of produced carbon which can be burned in high temperature regions of the chamber will increase as both combustion maximum and turbine entry temperatures increase. To provide a quantitative assessment of the degree of visual nuisance of smoke trails, prediction methods are being developed with the aid of data from research programmes.

ROCKET and ramjet engines have not the universal application that gas turbines command and possibly on this account they have not had, until recent years, the development effort which gave such amazing results in turbine powered aircraft. Nevertheless, they have demonstrated quite dramatically in various parts of the world that they are power plants to be reckoned with. In Great Britain, their value for aircraft was appreciated somewhat belatedly and events have since decreed that the promise they showed should be smothered before it could become a vital fact. On the other hand their importance for missiles was realized at the conclusion of the 1939–45 war, but again they were not encouraged on anything like the scale that present events show would have been justified. Because of this lack of encouragement, British rockets and ramjets, instead of leading the world, as do gas turbines, are struggling hard to provide a modest rate of progress.

ACCORDING to historical records the earliest known drawings for an aerial machine that can be classified under the heading of helicopter were made in the fifteenth century by the world renowned Italian scientist and artist Leonardo da Vinci (1452–1519). Probably the Chinese had been making their helicopter toy for some considerable time before da Vinci commenced his experiments. This toy consisted of two feathers, joined together by means of a cork or soft wood boss, to form a crude type of propeller which was pushed up a threaded stick so that upon leaving the stick the propeller rotated at high speed and continued to screw itself up in the air. When the speed of rotation decreased the propeller slowly windmilled down to the ground. A similar toy is still being sold today.

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.

Waste Heat Recovery Boilers (WHRB's) enhance the thermal efficiency of gas turbine power generating plants by capturing the heat from the exhaust gas and utilising it to raise steam for increased electricity production or district heating. Under normal conditions the exhaust gas from the turbine is cooled from around 550°C to 80°C. Care is taken that condensation will not occur in the cooler parts of the boiler. Nevertheless, during normal operation, dry ammonium nitrate deposits can be formed in the WHRB. These deposits will become wet when the unit is started or shut down, when the temperature falls below the dew point. The deposits may also “sweat” (i.e. absorb atmospheric moisture and become liquid) during extended plant outage periods. In consequence, Intergranular Corrosion Attack (IGA) and Stress Assisted Intergranular Corrosion Attack (SA‐IGA) (in general called stress corrosion cracking) can occur in carbon steel construction materials. The sensitivity to IGA of a total of 86 steels, of known compositions, was tested. The steels were subjected to aerated ammonium nitrate solutions of 90°C with concentrations ranging between 2 and 35 per cent. After an exposure of 65 hours, cross sections of the steels were studied. If IGA occurred, the steel was considered sensitive to ammonium nitrate at that (critical) percentage. During the investigation it was observed that alloying elements in several types of steel influenced its resistance to IGA in ammonium nitrate. Elements such as molybdenum, manganese and chromium had a positive effect on the resistance to nitrate induced IGA, SA‐IGA and stress corrosion cracking, whereas carbon and copper were detrimental. The microstructure of the steel also appeared to be important. In many specimens taken from in‐service failures, strings of carbide precipitates were found to be present at grain boundaries. The precipitates were identified to be ternary carbides. It seems, therefore, that the presence of carbides at grain boundaries increases the susceptibility of a steel to intergranular corrosion.

The purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the influences of ash fouling characteristics during the transient/steady-state simulation and optimization of a 3D complex heat exchanger equipped with inner plain fins and side plate fins are studied.

For the particle dispersion modeling, the discrete phase model is applied and the flow field has been solved using SIMPLE algorithm.

According to obtained results, for the recuperator equipped with combine inner plain and side plate fins, determination of ash fouling characteristics is really important, effective and determinative. It is clear that by underestimating the ash fouling characteristics, the achieved results are wrong and different with reality.

Finally, the configuration with inner plain fins with characteristics of: d_i =5 mm, d_o = 6 mm, d_g = 2 mm, d_k = 3 mm and NIPFT = 9 and side plate fins with characteristics of: T_F = 3 mm, P_F = 19 mm, NSPF = 17·2 = 34, W_F = 10 mm, H_F = 25 mm, L_F = 24 mm and ß = 0° is introduced as the optimum model with the best performance among all studied configurations.