Aircraft Piston Engine Research Articles

Assessment of the effectiveness of mounting the aircraft piston combustion engine on a test stand

The subject of the considerations described in the paper is the problem of efficiency of mounting an aircraft engine on a dyno test bench. The paper presents the empirical research results of vibroacoustic signal application to the evaluation of correctness of positioning of the Rotax 912 piston aircraft engine. The variability of selected parameters and vibroacoustic characteristics for real engine operating conditions was assessed, and functional relations and their discrete representations were developed, reflecting the efficiency of mounting the object on the frame. Thanks to this process, quantitative measures of the diagnostic assessment of the object were obtained, which can be used in periodic or continuous operational control of the object, taking into account the impact of tribological processes taking place in the test object.

Coupling analysis of cylinder block for two-stroke aviation piston engine

The aluminum alloy block is a component of aircraft piston engine, and it is prone to fatigue cracks when working in a thermal mechanical coupling state for a long time. Establish a GT-POWER simulation model for a certain type of engine, verify the accuracy of the model, obtain boundary parameters such as temperature and pressure of the engine block under harsh operating conditions through the model, and divide the cylinder wall into gradients based on the engine operating conditions to obtain the surface heat transfer coefficient of the block, and then obtain the temperature field distribution of the engine body. The coupling analysis of the cylinder burst pressure and temperature field of the engine block under harsh working conditions showed that the maximum stress of the engine block was 292.55 MPa and the maximum deformation was 0.39 mm, with thermal load being the main factor causing deformation. Conduct a complete engine bench test, and under the 1000 h bench durability test, there are no cracks on the engine block, indicating that the design and analysis meet the requirements.

Numerical Simulation of the Lubrication System of Aircraft Piston Engines

Numerical Simulation of the Lubrication System of Aircraft Piston Engines

Influence of oil service life on selected performance parameters of an aircraft piston engine

This article presents an analysis of the influence of oil service life on the performance parameters of an aircraft piston engine lubrication system used in an ultralight aircraft. The ageing of oil between oil changes causes a change in its parameters (such as density, viscosity ...). These parameters have a strong influence on the level of protection of the lubricated components. Currently, in aircraft, oil changes are carried out according to a time schedule - oil is changed every fixed period (residual life) regardless of its actual condition. The task of this article is to test the possibility of indirect assessment of oil condition based on analysis of changes in selected parameters of engine lubrication system operation during normal operation. The oil warm-up speed during the pre-start procedure and the dependence of oil pressure on engine speed were assumed for the analysis. The study was conducted on an ultralight rotorcraft during normal operation. Selected first daily flights directly after oil change, and after 17, 32, 50, 66 hours of operation were analysed. It was shown that the warm-up rate changes in the samples analyzed, but that this change may also be due to factors other than oil operating time. In the case of the oil pressure vs. speed characteristics, different characteristics were shown for different operating time, but no specific dependencies were found.

ВИКОРИСТАННЯ ПІДШИПНИКІВ КОВЗАННЯ У АВІАЦІЙНІЙ ТА КОСМІЧНОЇ ТЕХНІЦІ

Examples and prospects of various types of sliding bearings applications in power elements of aircraft engines and in turbopump units (TPU) of liquid propellant rocket engines (LPRE) are discussed in this article.In the second half of the last century, piston aircraft engines were replaced by turboprop (TPE) and turbojet (TJE) engines. Almost all leading manufacturers of these motors use rolling bearings as rotor supports for the main power units. The use of sliding bearings is extremely rare and is the exception rather than the rule. These exceptions include the company Pratt & Whitney, which has been using sliding bearings since the 1950s (engine PT6A). The sliding bearings are also used in modern turbofan engines Pratt & Whitney PW1000G series. The use of sliding bearings as a support for planetary gearbox elements has a number of advantages over rolling bearings, since under normal operating conditions such supports have a significantly longer service life.In rocketry, sliding bearings are used as supports for a LPRE TPU. Examples of such supports are hydrodynamic sliding bearings of the first German missiles during the Second World War (one of them was the FAU-2) and Soviet missiles developed by S.P. Korolev and V.P. Glushko. As our analysis has shown, in the 50s the use of sliding bearings in LPRE was abandoned due to a number of advantages of rolling bearings over sliding bearings, especially taking into account the very short service life of these engines (hundreds of seconds). Recently, however, sliding bearings as supports for a TPU have been attracting more attention again due to the development of reusable missile systems with a sharp increase in required service life. Although the results achieved for TPU with rolling bearings still provide the required durability, studies of the sliding bearings for TPU design with increased service life are relevant.The data obtained as the result of the analysis describe existing practice of using sliding bearings in units of aircraft and rocket engines, as well as the prospects for their further use.

Aircraft piston engine load distribution in steady state operating conditions

The article presents the results of analysis of operational parameters of piston engine CA 912 ULT which is a propulsion system of ultralight gyroplane Tercel produced by Aviation Artur Trendak. Research was conducted under normal operating conditions of the autogyro and data was collected from 15 independent tests including a total of 14 flight hours conducted during training flights. Engine and flight parameters were recorded at 9 Hz during each flight using on-board Fligh Data Recorded system. Collective results were presented to show the statistical analyses of the individual parameters by determining the mean values, standard deviations and histograms of the distribution of these parameters. The analyses included engine speed, charge pressure, air temperature, oil temperature and exhaust temperature. Histograms of operating points defined by both engine speed and manifold air pressure were also determined. Analyses were carried out to determine the contribution of steady-state and transient engine operation. It was also shown that the dynamics of engine work in real operating conditions is small. Detailed analyses were conducted for steady-state conditions. The value of the engine load index was determined and its statistical analyses were carried out. It was shown that the engine operating points are concentrated mainly in the range of idle and power above 50% of nominal power. The most frequent range is 50% to 80% of nominal power.

Numerical Investigation of the Intercooler Performance of Aircraft Piston Engines Under the Influence of High Altitude and Cruise Mode

Abstract Multistage supercharging is an effective way to solve the problems of low volumetric efficiency and combustion deterioration of piston engines under high altitude conditions. As a critical component of the supercharger system, the high-altitude intercooler performance is challenged to meet the heavy heat load caused by the large boosting ratio. The purpose of this study was to add more knowledge on the high-altitude intercooler performance to the limited existing studies. The intercooler experimental tests were conducted in a high-altitude simulation system, allowing for simultaneous pressure and temperature reductions. A 3D computational fluid dynamics (CFD) model was developed and validated against experimental results to investigate the intercooler performance, including the heat exchange and pressure drop characteristics. The results indicated that the atmospheric conditions and cruising speed significantly affected the intercooler performance. For example, the weighting of the effects of the temperature difference and air density on heat exchange performance varied with altitude. The altitude of 11 km was the turning point of the heat transfer rate because it is the junction of the troposphere and stratosphere. Based on this finding, this study further investigated whether a higher cruise speed could compensate for heat transfer deterioration with increasing altitude, more consistent with actual flight conditions. The simulation results showed that the variation of cruise speed directly affected the effectiveness of the heat exchanger, resulting in a different trend with altitude. Furthermore, the heat exchange of the intercooler fluctuated less with altitude under variable speed conditions. Overall, these findings support more fundamental research on high-altitude intercoolers, which may benefit the design and optimization of high-altitude engines and turbocharged systems.

Design, Development and Testing of a Starter-Generator Based on a Brushless DC Electric Machine for an APD-500 Aircraft Piston Engine Demonstrator

Design, Development and Testing of a Starter-Generator Based on a Brushless DC Electric Machine for an APD-500 Aircraft Piston Engine Demonstrator

Effect of ignition advance angle offset in a dual ignition system of a large aircraft piston engine

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out with different ignition advance angle offset between both spark plugs. In the test, the ignition advance angle for one spark plug was changed while leaving the ignition advance angle for the other spark plug. The tests performed for two engine operating points were to change the angle of the front spark plug and the rear spark plug. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the ignition advance angle offset significantly affects the combustion process. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When ignition is carried out with a steady rear spark plug advance angle, the combustion process practically does not change when the ignition advance angle of the front spark plug changes. However, changing the rear spark plug advance angle at a constant front spark plug ignition advance angle significantly changes the combustion process.

Application of Torsional Dampers for the Vibrations Reduction in Crankshafts of Piston Aircraft Engines

It is a well-known fact that piston engines shake, among which some of them more than others. Therefore, such type of vibrations, created by piston engines, should be controlled somehow. For the reduction of torsional crankshaft vibrations, torsional dampers are often used. The crankshaft vibrations are intrinsic in any internal combustion engine because of the powerful though unequal forces, which act directly on its crankshaft. Although the dampers will not add engine horsepower, lack of using them causes that crankshaft vibrations will hamper the horsepower potential of engines. The study attempts to explore how torsional-vibration damping methods can be improved for traditional aircraft horizontally-opposed engines.

Numerical investigation on combustion processes of an aircraft piston engine fueled with aviation kerosene and gasoline

Replacing gasoline with aviation kerosene for spark-ignition (SI) piston engines applied for aircrafts can get better security and easier logistics, however, this action cannot proceed smoothly by serious knocking combustion. In this study, the in-cylinder combustion for gasoline and aviation kerosene are investigated through computed-fluid-dynamics (CFD) to analyze combustion characteristics, and try to use pre-chamber technology to improve combustion issues.All CFD results demonstrate in-cylinder combustion differences effectively: All injected aviation kerosene cannot be completely evaporated, leading to non-uniformed unburned mixture and slow flame propagation. Some odd test phenomena are caused by unevaporated kerosene. The slower turbulence flame speed, worse equivalence ratio, higher local temperature and lower spontaneous combustion temperature lead to mixture auto-ignition and knocking combustion eventually. After adding a passive pre-chamber, the mixture distribution near spark plugs is more reasonable, higher turbulence kinetic energy (TKE) inside pre-chamber accelerates burning process, the ignition delay period is reduced by about 21.6%. The pre-chamber increases main-chamber's TKE, the whole combustion process is shortened by about 9%, the pre-flame reaction of unburned mixture near cylinder is shortened, contributing to suppress knocking combustion effectively. The passive pre-chamber technology is of great significance to the popularization and application for SI aircraft piston engine fueled with aviation kerosene.

Analysis of operating parameters of the aircraft piston engine in real operating conditions

The article presents the results of analysis of operational parameters of piston engine CA 912 ULT which is a propulsion system of ultralight gyroplane Tercel produced by Aviation Artur Trendak. Research was conducted under normal operating conditions of the autogyro and data was collected from 20 independent tests including a total of 28 flight hours, divided into training flights and competition flights.Engine speed, manifold air pressure and temperature, fuel pressure, injection time, and head temperature were recorded at 9 Hz during each flight. Collective results were presented to show the statistical analyses of the individual parameters by determining the mean values, standard deviations and histograms of the distribution of these parameters. Histograms of operating points defined by both engine speed and manifold air pressure were also determined. Analyses of the engine dynamics as a distribution of the rate of change of the engine rotational speed were also carried out. It was shown that the engine operating points are concentrated mainly in the range of idle and power above 50% of nominal power. The most frequent range is 70-80% of nominal power. It was also shown that the dynamics of engine work in real operating conditions is small. It was also shown that the way of use significantly influences the distribution of operating points. During training flights, an increase in the number of take-offs and landings causes an increase in the amount of engine work at take-off and nominal power and at idle.

Bench Tests for Exhaust Gas Temperature Distribution in an Aircraft Piston Engine with and without a Turbocharger

Bench Tests for Exhaust Gas Temperature Distribution in an Aircraft Piston Engine with and without a Turbocharger

Dimensional structural mass optimization of forged steel connecting rod for aircraft piston engine

The connecting rod is an important component of the engine. It conveys the kinetic energy from the piston to the crankshaft. All cars and aircraft engines contain at least one connecting rod, which differs from one motor to another in terms of length, size and shape. Hence, it is subjected to massive alternating load. This research aims to improve the connecting rod design by reducing its mass without sacrificing durability and safety especially for aircraft applications. Therefore, a static stress analysis is carried out on forged steel connecting rod using ANSYS APDL. Geometric modelling of the connecting rod was created using ANSYS APDL. Additionally, von-Mises stress and strain, principal stresses and strains, shear stress and the deflation results of the connecting rod are investigated. The results showed a great opportunity for mass weight reduction. Thus, a dimensional structural mass optimization was performed. The optimization results were promising, which reduced the mass by 55.13% (in the tensile case) and 56.7% (in the compression case) from the initial design. Therefore, the efficiency of aircraft engine can be maximized.

Altitude Performance and Fuel Consumption Modelling of Aircraft Piston Engine Rotax 912 S/ULS

Rotax 912 spark-ignition (SI) naturally aspirated aircraft piston engine is one of the most popular prime movers for the ultra-light weight aircrafts used for short and moderate range flights. SI engines operate at stoichiometric combustion and at high altitude conditions atmospheric pressure is lower than sea level reducing mass of air intake to the engine. At these conditions engine power degrades significantly from sea level, affecting flight parameters such as range and endurance. In order to optimize these parameters, engine power modelling is of vital importance. Within the scope of this study, a thermodynamic SI engine model with performance parameters (break torque and power) and fuel consumption estimation developed in MATLAB/Simulink software. Model tuning is realised using data extracted from Rotax engine operating manual at sea level and high altitude conditions. Model inputs are set as altitude, throttle lever and engine speed. Pressure drop at the intake port is modelled as a function of mass air flow using engine operating manual pressure data at various engine speed points. Mass air flow is determined via employing a volumetric efficiency map based on intake port pressure and engine speed inputs, calibrated using engine operating manual fuel data considering stoichiometric combustion. Compression and expansion strokes area modelled as isentropic events and combustion is modelled as constant volume heat input at top dead centre (TDC). However a combustion efficiency map based on engine speed and fuel flow is employed for the heat input in order to tune the work output of the engine and heat loss to the coolant and exhaust. Pumping loss is calculated based on friction mean effective pressure data. Introduced approach provides high accuracy performance and fuel consumption modelling based on engine operating manual data and can be used for flight parameters optimization studies.

Influence of the Flame Speed on the Power, Fuel Consumption, and Efficiency of the Aircraft Piston Engine

Influence of the Flame Speed on the Power, Fuel Consumption, and Efficiency of the Aircraft Piston Engine

Numerical Investigation on Combustion Processes of an Aircraft Piston Engine Fueled with Aviation Kerosene and Gasoline

Replacing gasoline with aviation kerosene for spark-ignition(SI) piston engines applied for aircrafts has become an essential trend. In this study, the fuel evaporation, mixture distribution, and flame propagation process of gasoline and aviation kerosene in a four-stroke SI engine are investigated through computed-fluid-dynamics(CFD) simulation to analyze in-cylinder combustion process and lay a theoretical foundation for some strange experimental phenomenon. The tested engine was operated under two different combustion mechanisms (with or without pre-chamber) and two throttle openings (26% and 30%) at a fixed engine speed of 5000 rpm.

Acoustic Characteristics of Aircraft Piston Engines

A brief overview of the noise generation mechanisms of piston engines is given. The spectral, energy, and spatial characteristics of the sound field are considered for engines used in aviation as a part of the power plants of light aircraft and unmanned aerial vehicles.

Comparison of dual and single spark ignition in operation of a large piston aircraft engine

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual or single spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out by both spark plugs, the rear plug only, and the front plug only. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the type of ignition significantly affects the combustion process and its non-repeatability. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When the ignition is carried out with the rear spark plug, the induction period is identical to that for dual ignition, but the combustion process is much less intensive. Ignition carried out with the front spark plug only has a longer induction period but a similar intensity of combustion as with dual ignition. Deactivating one of the plugs also improves the non-repeatability of the combustion process.

Problems of aviation leaded gasoline application on aircraft

A steady trend of expanding the small aircraft fleet equipped with piston engines is observed today. Special fuel (aviation gasoline with specified operational properties) for aircraft piston engines (PE) ensuring their stable operation in all modes and under all operating conditions is used. The indicators of aviation fuels operational properties including gasoline are achieved by means of adding special additives. One of these additives is an anti-knock additive – tetraethyl lead (TEL) that is added into the fuel in a certain amount in an ethyl liquid form. Despite the excellent TEL properties as an anti-knock additive, it also has a number of significant disadvantages. From the point of view of aircraft engine operation, it is noted that the TEL combustion products (decomposition) that are not effectively removed from the combustion chamber, enter the oil system in a significant amount, causing fine oil filters clogging. The article notes that even a small content of TEL decomposition products in aviation oils deteriorates dramatically their pumping capacity and leads to complete fine oil filters clogging for few minutes of engine operation, even on fresh oil. Moreover, the multi-stage oil cleaning stipulated by the design of some PE does not have a significant impact on this negative factor posing a threat to flight safety. These days the lead-containing gasoline use for aviation PE has no alternative, so solutions to reduce the negative consequences while applying are required.