Aircraft Diesel Engine Research Articles

ВИБІР ТА ОБҐРУНТУВАННЯ СХЕМИ НАДДУВУ ДИЗЕЛЯ АВІАЦІЙНОГО ПРИЗНАЧЕННЯ

The article provides the substantiation of the rational scheme of the boost system of the aircraft diesel engine KhADI-100A to ensure its altitude from the point of view of the lowest losses of the effective engine power. A method is proposed for assessing the power loss of an aircraft diesel engine depending on the flight altitude. Three variants of the supercharging system are considered: with one free turbocharger; parallel drive compressor and free turbocharger; sequential drive compressor and free turbocharger. As a result of the computational study, it was shown that in the case of using one free turbocharger at an altitude of h > 1500 m, the normal operating process of a diesel engine cannot be realized, since in this case, the excess air ratio falls below the critical value for a diesel engine α <1.4. Even if a constant excess air ratio is maintained, the effective engine power, with one free turbocharger, decreases by about 6 ... 11 kW per 1000 m with an increase in flight altitude. In schemes with a driving compressor, the quality of the fuel-air mixture will not change with altitude, and the power losses for their drive are insignificant in comparison - within 1 ... 2 kW per 1000 m of lifting height and can be compensated by increasing the cycle fuel supply without losing the quality of the working process. As a result of the computational study, it was concluded that the most rational from the point of view of the least power consumption is the scheme with a sequential drive compressor and a free turbocharger, the power consumption for the compressor drive at an altitude of 5000 m is 1.4 kW less than in the scheme with a parallel drive compressor and is the maximum value of 8.5 kW. The use of an electrically driven compressor is proposed since in this case the unit gains control flexibility to select the optimal operating mode and the possibility of using alternative energy sources for the drive electric generator (solar batteries, accumulators, thermoelectric generators, etc.).

Modelling of Dynamic Interactions in the Fuel Rail for the Aircraft Diesel Engine

Modelling of Dynamic Interactions in the Fuel Rail for the Aircraft Diesel Engine

Effect of scavenge port angles on flow distribution and performance of swirl-loop scavenging in 2-stroke aircraft diesel engine

Swirl-Loop Scavenging (SLS) improves the performance of 2-stroke aircraft diesel engine because the involved swirl may not only benefit the scavenging process, but also facilitate the fuel atomization and combustion. The arrangement of scavenge port angles greatly influences in-cylinder flow distribution and swirl intensity, as well as the performance of the SLS engine. However, the mechanism of the effect and visualization experiment are rarely mentioned in the literature. To further investigate the SLS, Particle Image Velocimetry (PIV) experiment and Computational Fluid Dynamics (CFD) simulation are adopted to obtain its swirl distribution characteristics, and the effect of port angles on scavenging performance is discussed based on engine fired cycle simulation. The results illustrate that Reynolds Stress Turbulence model is accurate enough for in-cylinder flow simulation. Tangential and axial velocity distribution of the flow, as well as the scavenging performance, are mainly determined by geometric scavenge port angles αgeom and βgeom. For reinforcement of scavenging on cross-sections and meridian planes, αgeom value of 27° and βgeom value of 60° are preferred, under which the scavenging efficiency reaches as high as 73.7%. Excessive swirl intensity has a negative effect on SLS performance, which should be controlled to a proper extent.

High-altitude performance and improvement methods of poppet valves 2-stroke aircraft diesel engine

Poppet valves 2-stroke (PV2S) diesel engine is promising to overcome the problems of low combustion performance and deteriorated emissions of conventional 2-stroke aircraft engines due to the lubricant leakage into cylinders. However, the high-altitude gas exchange and power performance of PV2S diesel engine with complex supercharging systems have been rarely studied, and the corresponding experimental methods are expected to be improved. To address these issues, a reformative experimental platform and one-dimensional simulation model are proposed to accurately predict the high-altitude performance and explore the improvement methods of a PV2S aircraft diesel engine with a combined supercharging system. Tracer gas method and pressure-based mass flow acquisition method are innovatively conducted in the platform to measure the gas exchange characteristics, which are validated with satisfactory accuracy and feasibility. The results indicate the performance deterioration of the PV2S engine is more severe than conventional 2-stroke engines due to the additional decrease of trapping efficiency. As the altitude increases from sea level to 8000 m, delivery ratio, trapping efficiency, charging efficiency and available brake power decrease by 22%, 27%, 43% and 61% respectively. Adjustments of valve overlap duration, as well as exhaust manifold length and chamber volume, can effectively improve the charging efficiency and brake power, which increase by 36.73% and 30.38% at 8000 m altitude, whereas at sea level they decrease 5.68% and 8.39% respectively. The study reveals the feasible application of PV2S diesel engine in aircraft propulsion and facilitates its use at high altitudes.

The zero-dimensional model of the scavenging process in the opposed-piston two-stroke aircraft diesel engine

The analysis of the scavenging process in two-stroke engines is important in terms of achieved performance and emission of toxic substances. The amount of mass of air used for the scavenging process and the amount mass of gas retained in the cylinder affect engine efficiency. When designing two-stroke engines, the most efficient charge exchange process defined by the scavenging efficiency parameter is desirable. The process of charge exchange in a two-stroke opposed-piston aircraft diesel engine based on the assumed scavenging model was analyzed in this work. The charge exchange process was performed by a mechanical centrifugal compressor. A zero-dimensional engine model created in the AVL BOOST program was used for the research. The simulation tests were performed for the selected operating conditions, i.e. maximum continuous power. The analysis of the charge exchange process was accompanied by obtaining the basic engine operating parameters from the simulation calculations.

Experimental research of oil pump for a compression-ignition aircraft engine

The paper presents an analysis of the constructions of oil pumps for an aircraft compression ignition engine. It is a two-stroke liquid-cooled engine with a power of 100 kW. The system has 3 cylinders and 6 opposed pistons. The paper estimates the required oil pump capacity to make the engine components well-lubricated. Next, automotive oil pumps for diesel engines are analyzed to select a correct pump for aircraft diesel engine applications. Three pump constructions of different constructions and dimensions of a rotor were selected. A measurement bench was designed and built to test these oil pumps in the range of pump shaft speeds from 0 to 4500 rpm and volumetric flow rate up to 150 l/min. The bench also enables stabilization of oil temperature at the required level within the range from 30 to 120oC. In addition, flow resistance through engine slide bearings was simulated by changing the position of a throttling valve at the pump output to regulate pressure in the range of 0–700 kPa. The obtained capacity characteristics of individual pumps versus on oil pressure and temperature allowed us to find an appropriate oil pump to make individual engine nodes well-lubricated.

Experimental research of two stroke aircraft diesel engine

This paper presents the results of experimental studies of the opposed-piston diesel engine. This engine was designed during one of the stages of the research on a new-type drive unit for gyrocopter applications. In order to conduct research, a special test stand as well as control and measurement systems were developed. As part of the work on the engine, the fuel injection system, engine temperature control system and measurement systems were designed. In addition, a computer program has been developed for the fuel injection system control (injectors, valves fuel pressure regulators). The paper presents the results of the preliminary tests for a single value of engine speed (1500 rpm) and three values of load defined by torque. The measured value of the indicated pressure made it possible to calculate the maximum pressure. The results obtained from the bench tests were analyzed.

Finite element analysis of a composite piston for a diesel aircraft engine

The article presents calculations of thermal and mechanical loads of the piston, consisting of two parts: steel and aluminum. The calculations were made using FEM in the Abaqus software. The piston is characterized by a split construction and was equipped with a cooling oil channel. The piston will be used in an aircraft diesel engine characterized by opposite piston movement. The presented geometry of the piston is the next of the ones being developed earlier and contains preliminary assumptions as to the size and main geometrical dimensions. The thermal boundary conditions of the simulation tests assumed defined areas of heat reception surface and heating of the piston by defining a temperature map on its crown. The results of these studies were presented in the form of temperature distribution and heat flux on the surface of the tested element. The strength boundary conditions assumed a mechanical load in the form of pressure resulting from the pressure in the combustion chamber applied to the piston crown surface and the opposite pressure defined on the support at the surface of contact between the piston and the piston pin. The results of these tests were presented in the form of stress distribution on the surface of the tested element. As a result of the analyses carried out, the results constituting the basis for further modernization of the piston geometry were obtained.

Selecting a material for an aircraft diesel engine block

Selecting appropriate materials is presently a complex task as material databases cover tens of thousands of different types of mate-rials. Product designing proceeds in numerous stages and in most of them there are open questions with not only one correct solution but better and worse ones. This paper overviews the Diesel engine body construction materials mentioned in the literature and discusses a certain practical method to select materials for a cylinder head and a Diesel engine block as a prototype. The engine body, depending on its purpose, is most frequently iron or aluminum. If it is important to optimize parts to achieve low weight, aluminum alloys are usual-ly applied, especially in the automotive and aviation industries. In the latter case, weight is even more important so new types of magne-sium alloys which are even lighter than aluminum ones are developed and used. However, magnesium alloys are, for example, more flammable and not enough strong so, for safety reasons, this type of material is not used solely in engine bodies.

An investigation of the fuel injector dedicated to the aircraft opposed-piston two-stroke diesel engine

The paper presents the research results of the injector construction with the modified injection nozzle. The injector is designed for a prototype opposed-piston aircraft diesel engine. The measurements were based on the Mie scattering technique. The conditions of the experiment corresponded to maximum loads similar to those occurring at the start. The measuring point was selected in line with the analysis of engine operating conditions: combustion chamber pressure at the moment of fuel delivery (6 MPa) and fuel pressure in the injection rail (140 MPa). The analysis focused on the average spray range and distribution, taking into account the differences between holes in the nozzle. As a result of the conducted research, the fuel spray range was defined with the determined parameters of injection. The fuel spray ranges inside the constant volume chamber at specific injection pressures and in the chamber were examined, and the obtained results were used to verify and optimize the combustion process in the designed opposed-piston two-stroke engine.

Energetic Analysis of the Aircraft Diesel Engine

The analysis of the distribution of thermal energy generated during the combustion process in internal combustion engines and the estimation of individual losses are important regarding performance and efficiency. The article analyses the energy balance of the designed two-stroke opposed piston diesel engines with offset, i.e. the angle by which the crankshaft at the side of exhaust ports is ahead of the crankshaft at the side of intake ports. Based on the developed zero-dimensional engine model, a series of simulations were performed in steady-state conditions using the AVL BOOST software. The values of individual energy losses, including cooling losses, exhaust gas losses, friction losses were obtained. The influence of decreasing and increasing the offset on the performance of the tested engine was analysed.

Numerical Analysis of a Fuel Pump for an Aircraft Diesel Engine

The paper reports on the process of modelling a high-pressure common rail pump designed to supply a two-stroke compression-ignition engine, which includes the presentation of methodology for model construction and results of simulation tests. A one-dimensional model of the pump was developed in the AVL Hydsim environment. A single-section positive displacement pump driven by a double cam was used for modelling. The developed model enables simulation of pump operation in various conditions defined by shaft speed, pumping pressure, settings of pump executive elements as well as fuel properties. The obtained results were compared with the results of bench tests and theoretical calculations. The analysis included the flow rate fuel overflow and changes in pumping pressure depending on the fuel dispenser settings. The model will also be used to build a complete fuel supply system model consisting of an injector model, a rail model and a control system model. The research is carried out with a view to optimising individual components and the operation of the entire supply system, taking into account the regulation of pumping pressure and synchronisation of the pumping process with fuel injection cycles.

Charging process analysis of an opposed-piston two-stroke aircraft Diesel engine

This paper presents the research results on a 1D model of an opposed-piston two-stroke aircraft Diesel engine. The research aimed at creating a model of the engine in question to investigate how engine performance is affected by the compressor gear ratio. The power was constant at all the operating points. The research results are presented as graphs of power consumed by the compressor, compressor efficiency and brake specific fuel consumption. The optimal range of compressor gear ratio in terms of engine efficiency was defined from the research results.

AN INNOVATIVE METHOD FOR DETERMINING MAXIMUM POWER OBTAINABLE FROM A COMMON RAIL TURBOCHARGED DIESEL ENGINE STARTING FROM EXPERIMENTAL DATA

ABSTRACTThis paper presents an experimental method for determining the maximum powerobtainable from an aircraft diesel engine derived from the automotive field. Severaltests were performed to estimate the real values of pressure and thermal loads on thepiston and head. The simple and original method described in this paper made itpossible to define two constants for the description of the engine-performanceenvelope.Maximum allowable pressure on the piston and the head was evaluated withcomputer simulation. Two different indicator cycles of the same engine (in theautomotive and aircraft version) were analyzed to extrapolate three constants thatdefine the engine family:• The contributing factor of compression (the exponent of the polytrophic curve n)• The contributing factors of combustion (a constant and an exponent)These contributing factors were examined and quantified separately.The paper is composed of two parts: the first part highlights the ultimate loads oncritical engine parts while the second details the method for the extrapolation of theultimate power output value. Successive experimental tests performed on the engineconfirmed the simple method described herein.

航空ヂーゼル発動機の超過送入に就て(第2報)

航空ヂーゼル発動機の超過送入に就て(第2報)