Design Of Internal Combustion Engines Research Articles

Energy aspects of automobile transport development

Problem. Improving automobile transport means increasing fuel economy and environmental indicators. Fuel, in a broad sense, means energy used to activate the car's power plant. Potential energy is dispersed in the earth’s interior, on its surface, in the atmospheric air, and even in space. Moreover, some of them exist in different substances. On the one hand, the efficiency of an energy product use is assessed by its energy intensity; on the other hand, it is evaluated by the costs of its production (transportation) and the quality of its transformation into a consumer type of energy. Special attention is paid to renewable and unlimited kinds of energy sources. Goal. The purpose of the study is a qualitative analysis of the road transport development direction from the standpoint of the alternative energy sources use, taking into account the factors that comprehensively determine the economic and environmental indicators at the stages of production and processing of fossil raw materials, production of power plants and conversion, transformation, and transportation of energy in the field of transport technologies. Methodology. The first direction consists of the adaptation (conversion) of the design of thermal internal combustion engines for alternative liquid or gaseous fuel types. The advantage of this approach is minimal costs for engine conversion and fuel production. The second approach involves using hybrid power plants, consisting of a main and auxiliary engine, an energy source or accumulator, an energy converter, and a braking recuperation system. The third direction is the use of non-traditional energy sources. Results. The directions of the development of power plants for motor vehicles related to the increase in the energy density of hydrocarbon fuels, the use of hybrid power plants, and the use of alternative energy sources have been determined. A qualitative assessment of the considered approaches is given. Originality. A comprehensive approach to evaluating the effectiveness of using alternative types of energy in road transport is considered in terms of energy, economic, and environmental indicators. Practical value. The obtained results can be regarded as recommendations when drawing up plans for the evolution of industries of fossil extraction and transformation of other energy resources, the development of motor vehicles, and transport infrastructure technologies, taking into account the natural and industrial potential of the country

A high-efficiency internal combustion engine using oxygen and hydrogen

The work proposes the design of a novel internal combustion engine developed to benefit from the availability on board of cryogenic pressurized hydrogen and oxygen to serve a mechanical propulsion system. The rationale behind the design, as well as the results of simulations, are presented. The two-stroke engine uses direct injection of hydrogen, oxygen, and water, and downstream power turbines, to deliver power densities above 220 kW/L, zero-emission of nitrous oxides and carbon dioxide, and efficiency above 0.70. The novel engine could be an alternative to fuel cell electric propulsion systems, delivering in addition to better hydrogen fuel efficiency, also reduced weight and space of the complete propulsion system.

Analysis of structures and application of different types of engines in cars

Problem. The publication analyzes the structures and application of various types of engines in a car, which allows to determine the structural aspects, features of placement and operation of engines, their future application prospects. Purpose. The purpose of the work is to analyze the design and operation of engines used in modern cars, to determine their advantages and disadvantages, and the prospects for the development and application of various types of engines. Methodology. The approaches adopted in the work to achieve the set goal consist in the analysis of designs of various types of engines of modern cars, their layout and features of their use. Results. The paper includes a comparative analysis of various types of engines used in modern cars. The peculiarity of the design and structure of internal combustion engines, electric cars and hybrid cars is considered. The scheme of the general configuration of electric vehicles, possible configurations of electric vehicles, layout schemes of hybrid cars are given. The advantages and disadvantages of each type of engine, the main prospects for their development and application are shown. Originality. The conducted analysis of the design features of various types of engines that are installed in modern cars allows us to formulate a general idea about the peculiarities of the operation of cars with the considered types of engines. Practical meaning. The obtained results of the analysis and the given advantages and disadvantages in the use of different types of engines allow us to formulate the main directions in the development of structures and the prospects of their application in different types of cars.

Simulation of Dual Combustion Cycle in Internal Combustion Engines using MATLAB

The aim of this study is to develop a comprehensive mathematical model to accurately represent the dual combustion cycle in internal combustion engines, with a focus on improving combustion efficiency and reducing emissions. The novelty of this research lies in the integration of advanced combustion models within the mathematical framework to capture the unique characteristics of dual combustion cycles. The model will consider factors such as combustion characteristics, fuel-air mixing, heat transfer, and emissions. By accurately simulating the dual combustion cycle, valuable insights can be gained into the complex interactions occurring within the engine, leading to the development of optimized engine design and control strategies. The proposed model will be implemented using MATLAB, which offers flexibility and computational efficiency. The results obtained from the simulation can be validated against experimental data to ensure the accuracy and reliability of the model. This study is expected to contribute to the advancement of dual combustion cycle technology and provide valuable guidance for the design and optimization of future internal combustion engines.

A One-Dimensional Numerical Model for High-Performance Two-Stroke Engines

Computer software that simulates the thermodynamic and gas dynamic properties of internal combustion engines can play a significant role in the design and optimization of internal combustion engines. In the present work, a quasi-dimensional numerical model for two-stroke engines is presented. Particular attention was paid to reporting in-cylinder models, combustion (turbulent with flame development and flame–wall interaction), and turbulence (K-k-ϵ model), with the addition of tumble- and squish-generated turbulence that is quite common in such engines. The aim was to reduce the role of the calibration constants, which are fundamental for correlating the models with the experiments, and relations for calculating the tumble ratio and turbulent scales were reported. A one-dimensional model for manifolds is also presented (solving the Euler equations), using the second-order Roe Riemann solver with some improvements, paying particular attention to the source terms, such as area variation. Additionally, a new approach to the end-pipe boundaries, which would reduce the mass conservation error, is reported. The engines tested were two kart two-stroke engines, used for racing purposes: the IAME X30 engine and the IAME Screamer III KZ engine. A comparison between the model results and the experimental data was made, and good accordance was observed, with a root mean square error of about 0.5 kW and providing good accuracy in evaluating changes, such as the combustion chamber squish area and the exhaust pipe length.

Combustion characteristics of a turbocharged direct-injection hydrogen engine

The direct injection hydrogen internal combustion engines avoid backfires and have a higher power density, especially when coupled with a turbocharger. However, while previous researches have focused on specific aspects of direct injection hydrogen internal combustion engines, their whole combustion characteristics remain largely unclear. Therefore, this study aims to comprehensively investigate the combustion characteristics of turbocharged direct injection hydrogen internal combustion engines across the entire operating map in order to optimize their performance. The combustion characteristics are hypothesized to be significantly influenced by operating parameters, including the equivalence ratio, spark timing, start of injection, and other relevant factors. To achieve this, the experiments were conducted on a 2.0 L turbocharged direct injection hydrogen internal combustion engine, covering a wide range of operating conditions. Specifically, the engine speeds varied from 1000 to 4000 rpm, loads ranged from 3.7 to 10.6 bar, equivalence ratios spanned from 0.33 to 0.71, spark timing was adjusted within a range of 21 degrees of crank angle, and start of injection varied within a range of 80 degrees of crank angle. The experimental results reveal notable findings regarding the turbocharged direct injection hydrogen internal combustion engine. For instance, the maximum pressure rise rate of the turbocharged direct injection hydrogen internal combustion engine (3.85 bar/°CA at 1500 rpm) at various engine speeds at wide open throttle are greater than those of a turbocharged port fuel injection hydrogen internal combustion engine and a gasoline engine. Furthermore, variations in equivalence ratio and spark timing cause significant increases in pressure rise rate by 328.4% and 233.3%, respectively. The peak pressure rise rate characteristics provide valuable insights for optimizing the noise, vibration and harshness of turbocharged direct injection hydrogen internal combustion engines. Additionally, the burning duration demonstrates an initial increase and subsequent decrease with changes in the start of injection, aiding in the determination of the optimal start of injection for achieving high brake thermal efficiency. Overall, this research provides valuable insights into the macroscopic combustion characteristics of a turbocharged direct injection hydrogen internal combustion engine across different operating conditions. These findings not only can be directly applied to hydrogen internal combustion engines of the same displacement and type, but also can be applied to the design and development of hydrogen internal combustion engines with different displacements and types.

Study of the intake system of automotive tractor internal combustion engines with variable parameters

Increasing the effective performance of automotive tractor engines is primarily associated with the intensification of the working process parameters. One of the options for solving this problem is to improve the cylinder filling parameters, which will allow to increase the engine power and torque. In addition to mechanical and gas turbine supercharging, the little-studied resonant supercharging of the engine is of interest. In this case, by selecting the parameters of the inlet path of the engine, it is possible to achieve a significant increase in pressure in the zone of the inlet valve opening without expenditure of useful energy, using only the kinetic energy of the gases of the inlet path. The paper proposes a method to calculate the geometric parameters of the intake tract using a one-dimensional model of gas flow. The results obtained from the numerical investigations give good convergence. The article can be useful for masters, graduate students, and engineering and technical workers involved in the design of internal combustion engines.

Experimental investigation on the vibrational and fluid dynamics behaviour of a turbocharger compressor in the transition to surge operation

High-speed dynamic centrifugal compressors are widely used both in the modern internal combustion engine design and in advanced pressurized cycles and innovative plant layouts as fuel cell systems. Surge strongly limits the stable operating region of centrifugal compressors in low mass flow rate conditions especially during fast transients. Therefore, it is of great importance to investigate transient system dynamic response of compressor surge evolution and early detection of incipient compressor surge. A specific experimental investigation on compressor surge was carried out at the University of Genoa turbocharger test facility and results are presented and analysed in this paper. The activity consists of steady state and transient measurements used to characterize and identify compressor behaviour in correspondence of surge inception conditions. The frequency and time frequency data analysis have been applied on inflow pressure, anemometric and vibrational signals to identify their contents and so to be able to classify compressor operation as stable or unstable. Synchronous averages performed in the time domain have been identified as a suitable algorithmic tool to detect incipient surge conditions. Anemometric signal analysis allowed to identify intermitting phenomena in deep surge conditions may be related to the rise of a rotation stall condition. The obtained results provide original diagnostic and predictive methods to be integrated in a monitoring system capable of preventing surge and extending compressor operating range, performance and reliability to allow the integration with the other plant components.

Methods for constrained optimization of expensive mixed-integer multi-objective problems, with application to an internal combustion engine design problem

Engineering design optimization problems increasingly require computationally expensive high-fidelity simulation models to evaluate candidate designs. The evaluation budget may be small, limiting the effectiveness of conventional multi-objective evolutionary algorithms. Bayesian optimization algorithms (BOAs) are an alternative approach for expensive problems but are underdeveloped in terms of support for constraints and non-continuous design variables—both of which are prevalent features of real-world design problems. This study investigates two constraint handling strategies for BOAs and introduces the first BOA for mixed-integer problems, intended for use on a real-world engine design problem. The new BOAs are empirically compared to their closest competitor for this problem—the multi-objective evolutionary algorithm NSGA-II, itself equipped with constraint handling and mixed-integer components. Performance is also analysed on two benchmark problems which have similar features to the engine design problem, but are computationally cheaper to evaluate. The BOAs offer statistically significant convergence improvements of between 5.9% and 31.9% over NSGA-II across the problems on a budget of 500 design evaluations. Of the two constraint handling methods, constrained expected improvement offers better convergence than the penalty function approach. For the engine problem, the BOAs identify improved feasible designs offering 36.4% reductions in nitrogen oxide emissions and 2.0% reductions in fuel consumption when compared to a notional baseline design. The use of constrained mixed-integer BOAs is recommended for expensive engineering design optimization problems.

Past and Future Practical Solutions for Torsional Vibration Damping in Vehicle Industry

In addition to material and production costs, consumption and emission limits, the requirements for performance, efficiency and space utilization must be met when it comes to the design of today's internal combustion engines for the automotive industry. As a result, three new design trends have been emerged (based on J. Pfleghaar and B. Lohmann's paper in 2013): 1. downsizing: reduction of engine size (number of pistons and stroke) for fuel and space-saving and CO2 emission reduction purposes, 2. downspeeding: reduction of engine speed to save fuel, which necessarily entails significantly higher torques being generated and transmitted in the engine, 3. turbo supercharging: increasing the pressure and compression ratio in the engine piston cylinder to cover the increased torque demand, which is accompanied by NOx gas emissions. Due to these new design trends, significant transverse, axial, and torsional oscillations can occur on the engine's crankshaft. To avoid power loss and fatigue due to the torsional oscillations, a torsional vibration damper is advised to be installed on the free end of the crankshaft or integrated into the flywheel. This review paper focuses on the possible reasons for torsional vibrations, the applied methods used to dampen them, and expected future trends.

MATHEMATICAL MODEL OF THE ACCELERATION PROCESS OF A WHEELED TRACTOR WITH CONSIDERING THE FUEL SUPPLY AND THE OPERATION OF THE HYDRO-CLAMPING CLUTCH

Analysis of Ukrainian production of wheeled tractors shows its rapid decline, due to many reasons, the main of which is the obsolete use of tractor technology, which affects the technical and operational performance, ergonomic and others. Today, most foreign wheeled tractors use the latest technology in the design of internal combustion engines, transmissions and wheeled engines. In particular, there is a greater bias towards the use of continuously variable transmissions. In order to create real competition for domestic producers, it is necessary to implement modern solutions, which is not possible without quality cooperation with scientists. Therefore, the material of this article aims to form guidelines for mathematical modeling of the dynamics of the wheeled tractor, taking into account the operation of the main clutch, hydraulic clutch and fuel control in the internal combustion engine. In solving this goal, a technique was used that provided mathematical modeling of the crankshaft of an internal combustion engine with the available harmonic components, as well as the ability to control the fuel supply. The simulation of the transmission operation was based on classical approaches in the study of the dynamic load of the power plant, taking into account the operation of the main clutch and hydraulic clutches. As a result, the dependences of the change of technical and operational parameters of the wheeled tractor at the stage of start-up and acceleration are obtained. The practical significance of the work lies in the possibility of its use in assessing the performance of a wheeled tractor, which is equipped with preselective and continuously variable transmissions, as well as a transmission that uses dual-clutch technology.

Influence of vehicle acceleration intensity on dual-mass flywheel elements and transmission load

Modern high-torque low-speed internal combustion engines (ICEs) generate torsional vibrations close in disturbance frequency to gearboxes natural oscillation frequencies. Effective absorption of such oscillations requires a new torsional vibration damper between the internal combustion engine and gearbox design, which is implemented in the form of a dual-mass flywheel (DMF). One of the main reasons for DMF failure is its spring components destruction. The article develops mathematical and simulation (in MATLAB Simulink environment) model of a car with DMF in the period of starting, which takes into account the dependence of torque and power of the internal combustion engine on the number of the crankshaft revolutions and uneven rotation, car inertial and stiffness parameters, road resistance. It is established that when the car starts in first gear, the maximum load on spring components of DMF and transmission occurs at the initial moment of clutch engagement and exceeds the maximum effective torque of the internal combustion engine 1.6 times, has a pronounced oscillatory character and stabilizes as the car accelerates. With smooth acceleration of a car, when torque of internal combustion engine reaches, but does not exceed its maximum value of 250 N‧m, elastic moment in transmission components is stabilized at 230 N‧m. During intensive acceleration and transition through the extremum on torque curve of internal combustion engine on number of crankshaft revolution, the maximum DMF spring components and transmission load initially doesn’t change significantly, but reduces the duration of oscillatory processes and elastic moment of 160 N·m after attenuation of oscillations. A similar nature of stress changes is observed in the elastic links of DMF, which eventually leads to their fatigue failure and DMF failure. To increase a DMF service life, it is advisable to accelerate a car when moving intensively, bringing a number of revolutions to a value that is located at the extreme of torque of internal combustion engine on its performance characteristic, followed by switching to the next gear.

A New Pathway for Prediction of Gasoline Sprays using Machine-Learning Algorithms

<div class="section abstract"><div class="htmlview paragraph">The fuel spray process is of utmost importance to internal combustion engine design as it dominates engine performance and emissions characteristics. While designers rely on computational fluid dynamics (CFD) modeling for understanding of the air-fuel mixing process, there are recognized shortcomings in current CFD spray predictions, particularly under super-critical or flash-boiling conditions. In contrast, time-resolved optical spray experiments have now produced datasets for the three-dimensional liquid distribution for a wide range of operating conditions and fuels. By utilizing such a large amount of detailed experimental data, the machine learning (ML) techniques have opened new pathways for the prediction of fuel sprays under various engine-like conditions. The ML approach for spray prediction is promising because (1) it does not require phenomenological spray models, (2) it can provide time-resolved spray data without time-stepping simulation, and (3) its evaluation has only a tiny fraction of the computational cost of a CFD simulation. In this study, an Artificial Neural Network (ANN) was applied for gasoline spray prediction under realistic engine conditions. Experimental data obtained under seven different fuels and three ambient conditions, totaling 21 different cases, were fed into a training procedure to investigate fuel effects on spray morphology. The quantitative validation results showed that the ANN is capable of predicting spray performance with nine input features, including fuel properties and ambient conditions. The ANN model fully trained on the experimental dataset showed greater accuracy in capturing the details of plume dynamics especially under flash-boiling conditions than the current state-of-the-art CFD model. While the ANN model cannot yet function or replace CFD in a full engine simulation, the ANN can be used now as a convenient design tool incorporating vast physical conditions.</div></div>

Validation and Enhancement of a Supermesh Strategy for the CFD Simulation of Four-Stroke Internal Combustion Engines

The present paper describes and validates an efficient CFD implementation to replicate the working fluid-dynamics of a real four-stroke internal combustion engine. To do this, experimental data obtained on a single-cylinder engine are used to validate the proposed computational approach. The engine domain is divided into regions according to each moving zone, and these are coupled using a pseudo-supermesh interface presented in a previous work by the authors. In this work, the original pseudo-supermesh strategy is enhanced by introducing the dual-boundary concept to model the valve opening/closing events to increase the accuracy and simplicity of the simulation procedure. The results produced by the proposed software tool show a good correlation to the experimental measurements of the complete engine cycle. Macroscopic quantities of the in-cylinder flow are accurately replicated as well as the instantaneous evolution of the in-cylinder and intake manifold pressure. Furthermore, the present work shows that the computational efficiency and scalability of the enhanced pseudo-supermesh approach are preserved even when applied to more complex real problems. In this sense, this work contributes to a new engineering tool promoting the enhanced pseudo-supermeshes as an effective tool for the design, development, and optimization of internal combustion engines.

A Computational Fluid Dynamics Investigation Comparing the Performance of an Alternative Valvetrain Design Against a Traditional Poppet Valvetrain

Abstract The poppet valve is by far the most widely used in cylinder head design of internal combustion (IC) engines; however, poppet valves themselves create significant flow restrictions during both the intake and exhaust strokes, thus causing a reduction in volumetric efficiency that affects overall engine performance. By removing the restrictive poppet valve from the flow path of air into and out of the cylinder head and allowing air to flow unobstructed, any given IC engine can achieve greater volumetric efficiency and higher specific output. The Vaztec ECOREV rotary valve system utilizes straight-cut flow passages that reduce such restrictions. This rotary valve system is designed to be directly driven by the crankshaft, thereby replacing the camshaft and poppet valve system altogether. This paper will primarily explore the differences in flow characteristics between this rotary valve and a conventional poppet valve cylinder head using both computational fluid dynamics (CFD) and flow bench data. Both configurations will be evaluated on the same single-cylinder four-stroke internal combustion engine. CFD simulations were run at multiple valve opening positions on each cylinder head configuration for both intake and exhaust cycles to validate the CFD process against flow bench test data for both cylinder head designs. The CFD was performed in 3D using hexahedral meshing and steady-state Reynolds-averaged Navier–Stokes (RANS) turbulence models. Comparison between the two engine configurations will include both intake and exhaust airflow rates as well as discharge coefficients and overall flow field evaluation using numerous scalar and vector properties.

Multi‐objective optimization of main bearing assembly structure based on improved NSGA‐II

AbstractMulti‐objective optimization of the main bearing assembly structure entails a high computational cost; moreover, the experimental measurement of the main‐bearing‐hole out‐of‐roundness has the problem of poor accuracy and inadequate repeatability. To address these issues, an improved NSGA‐II algorithm based on the fixed‐sized candidate set adaptive random testing (FSCS‐ART) algorithm and an adaptive strategy is proposed, and a more accurate method for measuring out‐of‐roundness based on the compensation method is developed. Accordingly, a mathematical model and a parametric model are established for optimization. Finally, the optimal design scheme is obtained by solving with the improved NSGA‐II algorithm. The results show that the proposed out‐of‐roundness measurement method has a high accuracy, with <5% error. The improved NSGA‐II algorithm exhibits a better solution convergence compared with the original algorithm does. The optimized solution of the improved NSGA‐II algorithm has a higher fitness when the two algorithms evolve to the same generation in the late stage, and the distribution of the Pareto optimal of the improved algorithm solution is closer to the Pareto frontier. After optimization, the stresses at the danger areas of the engine block and bearing cap are reduced by 13.67% and 6.71%, respectively. The out‐of‐roundness of the main bearing hole is reduced by 14.13%, and the maximum contact pressure on the dangerous contact surface is reduced by 14.08%. This study makes a significant contribution to the design of internal combustion engines because it facilitates the development of high‐power diesel engines by optimizing the reliability of the main bearing assembly structure.

Dual Mass Flywheel Parameter Identification

Abstract Reducing emissions brings changes in the design of internal combustion engines and thus new challenges for dual-mass flywheels (DMF) in terms of Noise Vibration and Harshness (NVH). The first part of the article describes a simple model of a centrifugal pendulum. Consequently, a more complicated DMF dynamic model involves friction between the spring components. The second part of the article deal with the multibody model of DMF using a CAD model. The dynamic model consists of a torsion spring and two bodies. The model is compared with the experimental method, which is also described in the paper.

On the use of particle image velocimetry (PIV) data for the validation of Reynolds averaged Navier-Stokes (RANS) simulations during the intake process of a spark ignition direct injection (SIDI) engine

Computational fluid dynamics (CFD) simulations of the in-cylinder flow field are widely used in the design of internal combustion engines (ICEs) and must be validated against experimental measurements to enable a robust predictive capability. Such validation is complicated by the presence of both large-scale cycle-to-cycle variations and small-scale turbulent fluctuations in experimental measurements of in-cylinder flow fields. Reynolds averaged Navier-Stokes (RANS) simulations provide overall flow structures with acceptable accuracy and affordable computational cost for widespread industrial applications. Due to the nature of averaging physical parameters in RANS, its validation against experimental results obtained by particle image velocimetry (PIV) requires consideration of how best to average or filter the measured turbulent flows. In this paper, PIV measurements on the cross-tumble plane were recorded every five crank angle degrees for [Formula: see text] cycles during the intake process of a motored, optically accessible spark ignition direct injection (SIDI) engine. Several methods including ensemble averaging, speed-based averaging and low-order proper orthogonal decomposition (POD) reconstruction were applied to remove the fluctuations from experimental PIV vector fields and thus enable comparison to RANS simulations. Quantitative comparison metrics were used to evaluate the performances of each method in representing the intake jet. Recommendations are made on how to provide a fair validation between measured data and simulation results in highly fluctuating flow fields such as the engine intake jet.

Incipient Surge Analysis in Time and Frequency Domain for Centrifugal Compressors

Abstract The use of centrifugal compressors has been increasing tremendously in the last decade as they are a key component in the present energy scenario both in the modern internal combustion engine design and in advanced cycles and innovative plant layouts as fuel cell systems. Instability phenomena limit the operating range of the whole compressor system, especially during fast transients. The target is therefore to extend the minimum flow limit in order to improve the operability of each unit while avoiding compressor surge operation and guaranteeing safe operation. For this reason, it is necessary to develop a monitoring system capable of preventing surge and extending the operating range of these machines, their performance, and reliability to allow the integration with the other plant components. The experimental investigation carried out at the University of Genoa turbocharger test facility and presented in this work, consists of steady-state and transient measurements used to characterize and identify compressor behavior in correspondence of surge inception conditions to determine different techniques which could represent surge precursors. The data analysis concentrates on pressure and vibro-acoustic signals by applying different signal processing techniques in the time and frequency domain to classify compressor operation as stable or unstable. The cross correlation function and wavelet analysis have been identified as techniques to define a precursor able to detect incipient surge conditions. Through cross correlation function analysis, it has been possible to identify the presence of propagation phenomena in the system and to evaluate how these events become more significant near an unstable low-mass flow rate condition. At low mass flow rate condition, spikes of significant amplitude are well detectable in the cross correlation function indicating the rise of significant random content in the system responses associated with the rise of incipient surge condition. Additionally, the continuous wavelet transform has been applied to operational signals to show how their time-dependent spectral structure responses can highlight the rise of unstable phenomena, not easily identifiable with traditional signal processing techniques. Exploiting its features in terms of good frequency and time resolution allowed us to identify different contents in system responses regarding phenomena that take place close to surge line and were able to detect their nature in conditions very close to deep surge ones (e.g., rotating stall with its intermitting characteristic nature). Moreover, system response was studied in high frequency range and through a demodulation technique, it was found how blade passes frequency energy content change interacting with rotating stall inception, moving close to surge line. The obtained results provide an interesting diagnostic and predictive solution to detect compressor instabilities at low mass flow rate operating conditions and to prevent compressor fails.

Performance of bioethanol and diesel fuel by thermodynamic simulation of the miller cycle in the diesel engine

The rapid growth in automotive industry and increased fuel consumption and environmental pollution, along with decrease in oil and fossil fuel resources, necessitate the adoption of new technologies to improve engine thermal efficiency and the use of alternative fuels. So, the present study proposes the thermodynamic cycle model of engine based on the Miller cycle and the use of bioethanol and diesel fuels. To analyze the cycle performance after examining the thermodynamic processes of the Miller cycle in the pressure diagram in terms of volume and calculating the amount of the operating fluid (fuel) and its thermodynamic properties based on bioethanol and diesel fuels and a homogeneous mixture of air, temperature was determined at the key points of engine operation through thermodynamic relationships. Then, the changes of engine performance parameters including output power and thermal efficiency were compared in terms of compression ratio based on Miller cycle using bioethanol and diesel fuels and they were also compared to the Otto cycle. The results showed that by increasing density ratio, the output power and thermal efficiency first increase and then decrease. Assuming to have the same volumetric efficiency and use bioethanol fuel, the engine output power and thermal efficiency would increase. Under optimum conditions of engine performance, power at the maximum point of efficiency and efficiency at the maximum point of power in the Miller cycle were greater than those of the Otto cycle. The results can be generalized to Atkinson cycle and other alternative fuels and used in a more practical way in the design and performance evaluation of internal combustion engines.