Function Of Crank Angle Research Articles

Analysis of the effect of the number of injector nozzles on the pressure and heat transfer coefficient in a hydrogen-diesel mixture diesel engine

In reciprocating internal combustion engines, the calculation of the heat transfer coefficient (HTC) is essential to estimate the heat transfer during combustion in the combustion chamber. The HTC calculation takes into account fluid flow and combustion processes and varies as a function of crank angle and location within the chamber. The mean HTC value is commonly used to calculate the thermo-mechanical analysis of various combustion chamber components. In this study, dynamic grids for the intake port, exhaust port and chamber are created in the chamber modelling section of the AVL-Fire software. The intake and combustion processes are then simulated and the calculated pressure data are compared with experimental data at 2800 rpm with 1, 3 and 6 hole injectors. Finally, the distribution of HTC over the chamber walls was evaluated using a time step method. The research also included verification of the HTC results with theoretical data obtained by Woschni and Hohenberg. In addition, with the decreasing availability of fossil fuels and the need for lower exhaust emissions from diesel engines, the use of blends of diesel and hydrogen fuel has become widespread. In this engine, a mixture of 10 % hydrogen and 90 % diesel fuel is used. The final results show that the heat transfer coefficient increases by approximately 1.72 % when hydrogen is added to diesel fuel due to the number of collisions between hydrogen and other fuel components.

Test bench development and implementation for experimental determination of mechanical losses in single cylinder internal combustion engines

As mechanical efficiency has great relevance in the alternative engine performance, the authors research in the development of testing facilities to characterize the sources of engine mechanical losses. The present paper deals with the realization of a hardware platform to conduct experimental studies in small combustion engines to experimentally characterize the mechanical losses of a single-cylinder internal combustion engine by means of the indicated diagram and motoring methods. The system was completed by means of an electrical motor-generator coupled to a single-cylinder air-cooled spark ignition engine, a self-developed electronic hardware control, and a PC-based instrumentation and data acquisition system. Specifications of load-motoring-starting system, including the description of the proprietary electronic load regulation system, are detailed. Also, the instrumentation system of in-cylinder and intake pressures; Temperatures of intake air, exhaust gases, lubricant oil, and engine block; effective torque and crankshaft position are described, including the signal acquisition system. The methodologies for indicated diagram and motoring method are described, mentioning the required measurements to apply each method and the engine load-temperature considerations when an engine is tested in fired or motored conditions. The platform was used to study the mechanical losses of the engine under motored and fired conditions under a wide range of rotational speeds and throttle openings, allowing to draw conclusions about the operating features of the developed test bench in itself, and also about the mechanical losses of the engine tested. Initially, samples of cylinder pressure, torque, intake pressure as function of crank angle and indicate diagram were obtained, showing similar waveforms present in related literature. Then, variations of the aforementioned temperatures against rotation speed and throttle opening and results for the mechanical losses determined by indicated diagram and motoring methods are shown. Finally, two empirical correlations are proposed to estimate the mechanical losses. In the future the hardware platform will be utilized to investigate in-cylinder engine parameters, detailed thermal and mechanical engine performance

Development of knock prediction technique in dual fuel engines and its mitigation with direct water injection

In the face of increasing emission restrictions and the parsimony of conventional fuels, dual fuel engine is presented as a promising solution that is satisfactory for environmental and economic aspects. However, this type of engine is limited by certain problems such as knocking, which negatively influences overall operation. For this reason and for optimal engine operation, prediction of this undesirable auto-ignition is essential. The approach developed in this work for this purpose, is based on dividing the combustion chamber into two zones to follow the thermodynamic properties of the unburnt gases where knock may occur. This thermodynamic modeling is coupled with a model based on Arrhenius equation for the auto-ignition delay as a function of crank angle. In addition, in order to make the model more predictive with the minimum of parameters to be calibrated experimentally, an analysis of variables is used for different engine conditions. The selected parameters undergo a correction before being modeled according to response surfaces methodology. After validation of the model using experimental results, it is coupled with a CFD calculation model to develop a global approach aimed at preventing knocking during dual fuel mode. The model makes it possible to predict knock onset with good precision. Consequently, preventing this phenomenon is possible. Water injection technique is therefore used for this objective. Accurate prediction was useful for knock avoidance via water injection strategy. Our results confirmed the effectiveness of this technique, justified mainly by water injection characteristics. The precision of the instant of knocking predicted by the developed model implied an optimal instant for water injection. Overall, this global model can be considered as a valuable means for knock prediction and prevention in dual fuel mode.

Performance Prediction, Optimisation and Validation of a CNG Engine Intake Manifold of a Commercial Vehicle Using Transient CFD Analysis

Developing countries like India have large consumer markets driven by huge demands. Commercial vehicles play a critical role in full filing these demands. Commercial vehicles increasingly face stringent emission norms criteria and hence designing an ICE-powertrain with optimum operating efficiency becomes paramount. Intake manifold is the critical part of an internal combustion engine that supplies fuel/ air mixture to all the cylinders combustion chambers. It ensures a uniform mixture at cylinder inlet for better mixing inside the cylinders for better volumetric efficiency. Uneven distribution of fuel/air mixture causes unstable torque and unburnt fuel which fails to meet the emission norms. It also results in uneven temperatures in each cylinder because of cylinder misfiring. In current paper, 3D Computational Fluid Dynamics (CFD) simulations are carried out to investigate the variance and uniformity of CNG/air mixture at the outlet of intake manifold. Commercial CFD tool Ansys Fluent is used to study the flow distribution of mixture inside the manifold and runners. Initial estimation of flow pattern is done by performing a steady state simulation to predict the uniformity index of CNG at cylinder inlet. For detailed investigation, transient simulation is performed by taking fresh air and CNG mass flow rate as a function of crank angle. In this paper, mesh dependence study was done initially to achieve an optimum cell count with good accuracy. A detailed transient analysis using multi-species modelling for air & CNG was done using automated scripts with time steps as small as 1 degree crank angle rotation coupled with injection pressure and injection timing study. This helped to identify critical areas and optimise the design to improve the mass flow rate variance from 15-20% for baseline case to 6-7% for final design, and also improve the uniformity index. It also helped reduce the CNG engine mis-firing issue. The results have been well validated with Laboratory Test Results.
 

Functional Stochastic Modeling of Empirical Knock Sensor Signals

Knock behaves a cyclically random process but also excites deterministic knock resonant behavior within any given cycle. While individual instances of the resonant response are readily acquired, the stochastic / cyclic variations of such signals (which also reflect the underlying knock process) are harder to quantify. In this work, a more complete model of this process is developed, capturing both the cyclic variability in the knock response as well as its functional resonant behavior. A recently developed alignment process is first used to evaluate the characteristic ensemble mean knock ‘signature’ of the data. A functional linearization about this ensemble mean is then used to decompose and model cyclic variations in terms of small variations in amplitude, frequency and phasing of the signal. The model is fitted to the data, encapsulating the stochastic variation of the knock signal within the stochastic variation of the estimated parameters. A residual analysis used to assess the goodness of fit as a function of crank angle, and the distribution and covariance of the estimated parameters is discussed.

A Quasi-Dimensional Fuel Distribution Model for a Radially Stratified Engine

Abstract Several combustion strategies leverage radial fuel stratification to adapt cylinder composition between the center of the chamber and the outer regions independently. Spark-assisted compression ignition (SACI) relies on careful tuning of this radial stratification to maximize the combined performance of flame propagation and auto-ignition. Established techniques for determining in-cylinder fuel stratification are computationally intensive, limiting their feasibility for control strategy development and real-time control. A fast running model for radial fuel stratification is developed for control-oriented objectives. The model consists of three submodels: spray penetration, fuel distribution along the spray axis, and postinjection mixing. The spray penetration model is adapted from fuel spray models presented in the literature. The fuel distribution and mixing submodels are validated against injection spray results from an large eddy simulation (LES) three-dimensional (3D) computational fluid dynamics (CFD) reference model for three test points as a function of crank angle. The quasi-dimensional model matches the CFD results with a root-mean-square error (RMSE) for equivalence ratio of 0.08–0.11. This is a 50% reduction from the 0.16–0.20 RMSE for a model that assumes a uniform fuel distribution immediately after injection. The computation time is 230 ms on an Intel (Santa Clara, CA) Xeon E5-1620 v3 to solve each case without optimizing the code for execution speed.

A sequential CFD-chemistry investigation of the chemical and dilution effects of hydrogen addition on the combustion of PRF-85 in an HCCI engine

The effects of hydrogen addition on the combustion characteristics of a primary reference fuel PRF-85 in a Homogeneous Charge Compression Ignition engine have been investigated analytically. The numerical modeling was focused on both chemical and dilution effects of hydrogen enrichment. The analysis used a sequential procedure combining a fluid mechanics code (IC Engine coupled with ANSYS FLUENT) to determine temperature and mass distributions as a function of crank angle, assuming motored conditions, and a mutli-zone model (ANSYS Chemkin multi-zone HCCI model) to calculate combustion and engine efficiency using a detailed chemical kinetic mechanism containing 1550 species evolved in 6000 reactions. Analysis was performed using an HCCI engine with a constant speed (1200 rpm) and an intake manifold pressure of 1 bar. The obtained results indicate that hydrogen dilution effect retarded combustion phasing, decreased both combustion duration and specific fuel consumption, and boosted the engine thermal efficiency. Opposite trends were observed for the chemical effect. In all cases, it was found that, whatever the hydrogen percentage in the fuel mixture, the dilution effect was very important as compared to the chemical one, suggesting that combustion characteristics and engine power output variations with hydrogen enrichment were essentially due to the dilution effect.

The statistical properties of raw knock signal time histories

Traditional processing of knock signals reduces each recorded time history to a single scalar knock intensity metric for each engine firing, thereby losing all information relating to the phasing and evolution of knock over the combustion period. In this work, a statistical analysis of raw knock cylinder pressure and accelerometer signal time histories has been performed showing how the nonstationary stochastic characteristics of these signals evolve as a function of crank angle, and as a function of spark timing. The data are shown to closely approximate a cyclically independent process whose 2-dimensional covariance function captures both the non-stationary deterministic processes taking place within a cycle as well as the stationary random variations from one cycle to the next. A (time-varying) dual-Gaussian model for the distribution of these cyclic variations was fitted to the data, thereby enabling them to be characterized as the sum of knocking and non-knocking populations. The parameters of the model, which describe these populations separately, provide further empirical insight into the knock process.

Thermodynamic work in inline piston gasoline engines as a function of crank angle

The purpose of this research work is to identify the laws of thermodynamic operation in the theoretical cycles of four-stroke inline piston gasoline internal combustion engines (ICE). The main results: dependence of the thermodynamic operation of the working body of ICE in theoretical cycles of four-stroke inline piston gasoline engines as a function of the angle of rotation of the crankshaft; regularities of uneven generation of positive thermodynamic operation in the theoretical cycle of four-stroke inline one-, two-, three -, five-cylinder piston gasoline ICE; regularities of the alternating character of thermodynamic operation in the theoretical cycles of inline four-stroke one -, two -, three -, four - and five-cylinder gasoline piston ICE; regularities of positive thermodynamic operation during the entire theoretical cycle of four-stroke inline six-and eight-cylinder piston gasoline ICE; conditions for uniform pulsation of thermodynamic operation during the entire theoretical cycle of four-stroke inline piston gasoline ICE - the product of the crankshaft angle by the number of cylinders must be 720o (four-cylinder inline with a crankshaft angle of 180o, six-cylinder inline with a crankshaft angle of 120o, eight-cylinder inline with a crankshaft angle of 90o).

Use of the Chief Engineers Experience to Prioritize Operational Tasks in the Ship Engine Room

Abstract The frequent causes of ships’ detentions by port authorities are abnormalities of marine power plant functioning. Each extended ship lay time in port results in a waste of ship operating time thus costs rise to ship owners. This is connected with improper marine power plant management. In order to avoid this, a ship engineer should have at his disposal computer aided system supporting him in the managing of the marine power plant. One element of the decision making process in managing the marine engine room is to determine how important is each of the tasks which the operators have to do. This estimation is the base to choose the most important tasks and make optimal schedule with them using AHP method. Based on practice, a hierarchic structure of factors influencing a tasks validity in the engine room operating process was made. Next a preliminary questionnaire was conducted, which put questions to the experts as chief engineers next. This enabled to define numerical values of suitable coefficients influencing on the validity of operating tasks, show results of calculations in form of mileage parameters of engine as a function of crank angle.

The Use of a Mathematical Model of Marine Diesel Engine in a Computer Program

Abstract The paper describes the application of the author’s mathematical model of gas-dynamic processes for a marine piston engine based on a computer program. The developed mathematical and numerical model is designed to conduct simulation diagnostics. Therefore, it is possible to carry out calculations for motors in different technical conditions and observing influence of changes in technical condition on selected parameters of its work. Simulation of changes in technical condition is carried out by modifying parameters of structure’s model object. The article contains a detailed description of each options of the computer program. From the main program window, user can select type of engine model (supercharging method, cylinder number, work order, stroke and piston diameter and a number of other parameters). Through a window of simulation of known and recognizable damages such as: change in fuel dose for each cylinder, change in intake and outlet valves, leakage of piston-ring-cylinder system, change of injector hole cross section. Final windows show results of calculations in form of mileage parameters of engine as a function of crank angle.

Influence of the use of ethanol fuel on selected parameters of the gasoline engine

Main subject of this thesis is to contrast gasoline and ethanol fuel combustions by measuring effective parameters. Introduction to the research part comprises theoretical description of alternative fuels available for gasoline engines. Next, it was describe preparation to research, also research itself and the results analysis. Results contain graphs of parameters: the pressure in the engine cylinder, the rate of pressure changes in the cylinder (as a function of crank angle). Results also contain graphs of parameters torque, engine efficiency, concentration of toxic exhaust components (as a function of the air–fuel equivalence ratio (λ) and as a function of the spark advance angle). There parameters are shown for constant the crankshaft rotational speed, for constant throttle position. Research confirmed that the use of ethanol fuel does not cause significant losses or gains in terms of effective parameters.

The convection heat transfer rate evaluation of a 6-cylinder in-line turbocharged direct-injection diesel engine

The in-cylinder convective heat transfer from the combustion gas to the cylinder wall of the combustion chamber has a strong effect on the diesel engine performances. This study contribute to the knowing in this area for the event of the convective heat transfer from fluid to the cylinder wall of a turbocharged diesel engine with six-cylinder direct injection operating under steady-state conditions. An optimized choice of correlation was applied for the evaluation of heat transfer coefficient, which is the Hohenberg's correlation. We developed a computer program for simulating the operation of a six-cylinder direct injection turbocharged diesel engine, and using a commercial GT-Power software to validate the simulation results. The influence of certain engine parameters (thermodynamic and geometric) on the convective heat flux and its maximum value are studied in the present paper. The results show that the convective heat transfer characteristics as a function of crank angle of the six cylinder turbocharged diesel engine strongly depend on the engine injection timing, the cylinder wall temperature and load for the both softwares; FORTRAN and GT-Power. DOI: http://dx.doi.org/10.5755/j01.mech.23.4.14898

Friction losses modeling of piston rings for various combustion pressures in diesel engine

This paper describes a numerical simulation of the lubrication between the first compression piston ring and the cylinder liner in a typical diesel engine, using the one-dimensional Reynolds equation. The geometric profiles of piston rings are axisymmetric. The inlet boundary is assumed to be fully flooded, but Reynolds cavitation boundary conditions are assumed for the outlet boundary. Cavitation boundaries, frictional forces, friction coefficients, lubrication regimes and power losses are determined for various combustion pressures, which were induced by varying the injection strategy at fixed injection quantity and constant engine speed. Results of the simulation show a dependence of the frictional force on the combustion pressure. Power losses due to the frictional force are obtained as a function of crank angle.

Creating mechanisms of toxic substances emission of combustion engines

Abstract The paper analyses the mechanisms of creation of toxic exhaust gases, which mainly derived from inexact fuel metering and improper air-fuel mixture preparation. The paper describes the process of creating toxic components in the exhaust gases of piston engines during engine operation, and impact on the emission of these components determining the composition of the fuel mixture determined equivalence factor Φ. The principal mechanisms of formation of toxic exhaust gases, in particular nitrogen oxides, carbon monoxide and hydrocarbons, and also essential according to create each of toxic exhaust gases are the subject of the paper. Moreover, empirical relationships, by means of which it is possible to determine the time of creation of the individual components of toxic exhaust gases, are presented. For example, one of the mechanisms for prompt formation of nitrogen oxides and hydrocarbons graphic illustration of formation as a function of crank angle is described. At the conclusion, the summary and significance of information on creation mechanisms of toxic components in the exhaust gases of piston engines are presented.

Modeling In-Cylinder Water Injection in a 2-Stroke Internal Combustion Engine

In this study, we apply Computational Fluid Dynamics (CFD) models in investigating the effect of injecting water into the combustion chamber of a 2-stroke Internal Combustion Engine (ICE). Using the commercial code, Star-CD, 3-D models for a port scavenging, in-cylinder fuel-injection; 2-Stroke engine is developed.The adapted engine's effective compression ratio (CR), crank Revolution per Minute (RPM) and fuel type are 8.5, 2000rpm and Heptane (C7H16) respectively. Two types of water mixing techniques are investigated: homogenous pre-mixing with the reactants, and direct injection around the walls of the combustion chamber. The engine's pressure, temperature, and pollutant mass fraction are estimated as a function of crank angle and injected water to fuel mass ratio, for both mixing techniques. The calculated indicated work (area under P-V diagrams) is used to estimate other engine performance indicated parameters. Results showed that although the homogenous mixing of water has an effect of reducing the combustion temperature and resulting NOx emissions, the pressure exerted on the piston is greatly diminished by this technique. However, when water vapor is injected around the chamber walls, the resulting reduction in temperature and NOx emissions has a minimum effect on the engine's P-V diagram.This is as a result of a water vapor blanket formed around the combustion zone, by the injected water vapor, which cools down the cylinder's wall with a minimum influence on the combustion process. Further analysisshowed that the water injection technique could increase the power/torque per engine size and hence, increase energy efficiency. Ultimately, the study presents the advantages of using water injection for enhancing fuel efficiency and reducing pollutant emissions

Determining the performance, emission and combustion properties of camelina biodiesel blends

In the present study, the effects of two different camelina biodiesel fuels obtained through transesterification on engine power and torque performance and emissions and fuel combustion characteristics of these fuels compared to diesel fuel were determined particularly focusing on new blend ratios of B7 and B100, which the European Union has been specifically studying on.Heat release rate calculations, which are an important parameter for the engine characterizing the combustion process that occurs depending on cylinder pressure and crank angle, and mass fraction burned (MFB) in each individual engine cycle, which describes the process of chemical energy release as a function of crank angle, were determined in the study. Maximum HRR (Heat Release Rate) at 2500rpm and 4000rpm was found as 35J/Crank Angle Degree.MFB values at 2500rpm and in blends were found as 100% after 30° (ATDC), at 4000rpm as 100% after 34° (ATDC). Temperature variation depending on crank angle and blends was found to be a maximum of 1900K after 18° (ATDC).

A statistical model for combustion resonance from a DI diesel engine with applications

Introduced in this paper is a Bayesian model for isolating the resonant frequency from combustion chamber resonance. The model shown in this paper focused on characterising the initial rise in the resonant frequency to investigate the rise of in-cylinder bulk temperature associated with combustion. By resolving the model parameters, it is possible to determine: the start of pre-mixed combustion, the start of diffusion combustion, the initial resonant frequency, the resonant frequency as a function of crank angle, the in-cylinder bulk temperature as a function of crank angle and the trapped mass as a function of crank angle. The Bayesian method allows for individual cycles to be examined without cycle-averaging—allowing inter-cycle variability studies. Results are shown for a turbo-charged, common-rail compression ignition engine run at 2000rpm and full load.

Analysis of Incylinder Pressure and Temperature Variation in a Four-Stroke S. I. Engine Using Wiebe’s Combustion Model

This paper presents the modeling of in-cylinder pressure variation of a four-stroke single cylinder spark ignition engine. It uses instantaneous properties of working fluid, viz., gasoline to calculate heat release rates, needed to quantify combustion development. Cylinder pressure variation with respect to either volume or crank angle gives valuable information about the combustion process. The analysis of the pressure – volume or pressure-theta data of a engine cycle is a classical tool for engine studies. This paper aims at demonstrating the modeling of pressure variation as a function of crank angle as well as volume with the help of MATLAB program developed for this purpose. Towards this end, Woschni heat release model is used for the combustion process. The important parameter, viz., peak pressure for different compression ratios are used in the analysis. Predicted results are compared with experimental values obtained for a typical compression ratio of 8.3.

From bicycle chain ring shape to gear ratio: Algorithm and examples

A simple model of the bicycle drive system with a non-circular front chain ring is proposed and an algorithm is devised for calculation of the corresponding Gear Ratio As a Function Of Crank Angle (GRAFOCA). It is shown that the true effective radius of the chain ring is always the perpendicular distance between the crank axis and the line through the chain segment between the chain ring and the cog. It is illustrated that the true effective radius of the chain ring at any crank angle may differ substantially from the maximum vertical distance between the crank axis and the chain ring circumference that is used as a proxy for the effective chain ring radius in several studies; in particular, the crank angle at which the effective chain ring radius is maximal as predicted from the latter approach may deviate by as much as 0.30rad from the true value. The algorithm proposed may help in designing chain rings that achieve the desired GRAFOCA.