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Spark ignition (SI) engines are used in a wide area in the transportation industry, from road vehicles to piston-prop aircraft. On the other hand, the decrease in reserves of fossil fuels used in SI engines and the increase in greenhouse gas emissions makes the use of alternative fuels inevitable. In this paper, optimization of in-cylinder combustion and engine performance parameters by intake-charge conditions [i.e. intake-air temperature, injection timing and exhaust gas recirculation (EGR)] in a hydrogen (H₂)-fueled small SI engine is performed.

Experimental studies were performed at a 1,600 rpm engine speed of a single-cylinder, air-cooled engine having a stroke volume of 476.5 cm³, maximum output power of 13 HP and torque of 25 Nm. The hydrogen-fueled SI engine was operated by a lean air-fuel mixture (ϕ = 0.6) under wide-open throttle (WOT) conditions.

The findings of the paper show that improvements can be achieved in in-cylinder combustion, indicated engine performance, exhaust NO_x emissions with optimum intake-air temperature, the start of H₂ injection and the ERG rate.

It has been determined that a 32°C intake-air temperature, 395°C (bTDC) start of H₂ injection, and 5%–10% EGR rates are the most suitable values for the examined hydrogen fueled SI engine.

Hydrogen is a usable alternative fuel for SI engines used in a wide area from road vehicles to piston-prop aircraft engines. However, a number of problems remain that limit hydrogen fueled SI engines to some extent, such as backfire, a decrease of engine power, and high NO_x emissions. Therefore, it is appropriate to examine the effects of intake-charge conditions on in-cylinder combustion, engine performance, and NO_x emissions parameters in a hydrogen fuelled SI engine.

SAND is very harmful to engines. During recent tests conducted by me in the North African Deserts, as much as half a pound of sand has been collected in ten minutes in each air intake of a Mosquito aircraft taxying, alone, downwind on a desert airfield. Had the Mosquito been following another aircraft, or had its air intake been situated lower, the quantity of sand would have been much larger. Under such conditions the importance of having efficient air cleaning intakes fitted to every aircraft engine is obvious. Sandy conditions are not confined to desert airfields, some airfields in this country and on the Continent are as bad.

The purpose of this paper is to present the results of the preliminary design and optimization of the air-intake system and the engine nacelle. The work was conducted as part of an integration process of a turboprop engine in a small aircraft in a tractor configuration.

The preliminary design process was performed using a parametric, interactive design approach. The parametric model of the aircraft was developed using the PARADES™ in-house software. The model assumed a high level of freedom concerning shaping all the components of aircraft important from the point of view of the engine integration. Additionally, the software was used to control the fulfillment of design constraints and to analyze selected geometrical properties. Based on the developed parametric model, the preliminary design was conducted using the interactive design and optimization methodology. Several concepts of the engine integration were investigated in the process. All components of the aircraft propulsion system were designed simultaneously to ensure their compliance with each other.

The concepts of the engine integration were modified according to changes in the design and technological constraints in the preliminary design process. For the most promising configurations, computational fluid dynamics (CFD) computations were conducted using commercial Reynolds-averaged Navier–Stokes solver FLUENT™ (ANSYS). The simulations tested the flow around the nacelle and inside the air-delivery system which consists of the air-intake duct, the foreign-particles separator and the auxiliary ducts delivering air to the cooling and air-conditioning systems. The effect of the working propeller was modeled using the Virtual Blade Model implemented in the FLUENT code. The flow inside the air-intake system was analyzed from the point of view of minimization of pressure losses in the air-intake duct, the quality of air stream delivered to the engine compressor and the effectiveness of the foreign particles separator.

Based on results of the CFD analyses, the final concept of the turboprop engine integration has been chosen.

The presented results of preliminary design process are valuable to achieve the final goal in the ongoing project.

THE greater part of the development of the components of a complicated mechanism, such as an aircraft engine, can with advantage be done apart from the mechanism as a whole. The study of any part can be more complete and improvements in operation effected more readily when it is not necessary to keep the whole working. A carburettor is in many respects a complete unit whose action may be studied with advantage apart from the engine with which it will be used. While the ultimate criterion of the performance of a carburettor is its behaviour on an engine, a great deal can be learned from suitable bench tests in which the engine is replaced by a suction plant; more use could be made of such testing methods than is done at present.

The purpose of this paper is to describe studies of accidental ignition of fuel‐air mixture. Studies were carried out in a laboratory that contains the naturally aspirated aircraft engine LYCOMNIG 320B1A IO type used in the EM‐11C Orka aircraft and the intake system to determine its resilience to the effects of accidental ignition and the occurrence of a backfire.

Tests were performed on a model under extreme conditions (with the intake system closed) and under conditions similar to normal operation using fuels of different combustion rates.

It was found that the positive pressure caused by such accidental ignition under normal operating conditions did not exceed 0.08 bar and did not pose any hazard of damaging the intake system of the IO‐320B1‐type LYCOMNIG naturally aspirated aircraft engine, as designed by the aircraft manufacturer.

The positive results of the tests of the EM11C Orka aircraft intake system's resistance to flashback and other positive test results for this aircraft have contributed to obtaining the EASA.A.115 Certificate and the EASA.21J.117 Certificate for the Design Unit, and the plane was presented at the AERO – Friedrichshafen 2011 Exhibition.

The paper described how, in the laboratory, simulated extreme operating conditions of the naturally aspirated aircraft engine intake system powered aircraft fuels with different burning speeds (aviation gasoline, hydrogen).

Aerodynamic characteristics of engine side air intakes for a lightweight helicopter are investigated aiming to achieve an efficient engine airframe integration.

On a novel full-scale model of a helicopter fuselage section, a comprehensive experimental data set is obtained by wind tunnel testing. Different plenum chamber types along with static side intake and semi-dynamic side intake configurations are considered. Engine mass flow rates corresponding to the power requirements of realistic helicopter operating conditions are reproduced. For a variety of freestream velocities and mass flow rates, five-hole pressure probe data in the aerodynamic interface plane and local surface pressure distributions are compared for the geometries.

In low-speed conditions, unshielded, sideways facing air intakes yield lowest distortion levels and total pressure losses. In fast forward flight condition, a forward-facing intake shape is most beneficial. Additionally, the influence of an intake grid and plenum chamber splitter is evaluated.

The intake testing approach and the trends found can be applied to other novel helicopter intakes in early development stages to improve engine airframe integration and decrease development times.

SUPERCHARGED aero engines are more or less a post‐war invasion into the practical side of aero‐engine design. The problem of power boosting for internal combustion engines, especially aero engines, has for several years engaged the attention of engine designers, with the result that to‐day quite a number of engines are produced with superchargers as an integral part of the standard equipment. Various types of superchargers have been tried, such as the reciprocating pump, Roots Blower, exhaust‐driven turbo compressor, and the gear‐driven centrifugal form of blower. The last‐named is the type most commonly used in this country at the present time.

The purpose of this study is to improve the performance of hollow fiber membrane and improve the separation efficiency.

By establishing a mathematical model of hollow fiber membrane gas separation, the influences of parameters such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament on the polarization coefficient were analyzed, so as to explore the degree of influence of operating parameters on the concentration polarization, and put forward a technical scheme to reduce the concentration polarization.

Factors such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament have a certain effect on the polarization coefficient. Among them, the polarization coefficient is positively correlated with pressure difference inside and outside the filament, initial oxygen concentration of intake air and back pressure outside the filament, and is negatively correlated with intake air flow.

Negative pressure suction on the permeation side can be used to increase the membrane permeation flow rate and reduce the concentration polarization.

The influence of concentration polarization on membrane performance is reduced by controlling various factors.

IN many types of engine the supercharger is built on to the accessory‐drive end, that is the rear of the engine, so that the supercharger shaft lies co‐axially or parallel with the crankshaft. This has the great advantage of permitting the use of simple spur gearing, but suffers from the disadvantage that in passing through both intake and delivery section, the working fluid is subjected to several right‐angled changes in direction. In the case of the Rolls‐Royce Merlin for example, with air intakes on either side, there are 2 × 2 right‐angled bends before the inlet to the impellor is reached and two more at the delivery side. Such bends naturally involve losses in supercharging which should definitely be avoided. Hence in Germany in the two liquid‐cooled inline types the Jumo 211 (Fig. 1) and Mercedes‐Benz DB600 (Fig. 2) the supercharger shaft is built square to the engine crankshaft and the supercharger located at the side of the transmission casing, so that a single right‐angled bend suffices to change the direction of flow of intake air from that of flight and lead it axially to the impellor. If, at the same time, care is taken in nacelle design to ensure an undisturbed flow of air to the intake duct, then the total static head of flight may be utilized in supercharging the engine, resulting in an increased altitude rating. The proportion of this increase due to full utilization of the flight static head is shown in Fig. 3. For example, at a speed of 600 km.p.h. (373 m.p.h.) its value is about 1,400 m. (4,600 ft.)

ICE formation in the carburettor or induction system of an aircraft engine may cause a serious loss of power, and if the ice continues to build up it will eventually cause complete failure of the engine. In consequence of this possibility the Air Ministry undertook, at the Royal Aircraft Establishment, a comprehensive investigation to determine the conditions under which ice is formed and to find means to prevent or remove it. The research has been attended by marked success, and the present article deals with the more important features of the work with particular reference to the practical considerations arising from it. The full results of the research are given in a paper by W. C. Clothier on “Ice Formation in Carburettors,” published in the Journal of the Royal Aeronautical Society, No. 297, Vol. XXXIX.