Bi-fuel SI Engine Model for Analysis and Optimization

YesThe natural gas as an alternative fuel has economical and environmental benefits. Bi-fuel engines powered by gasoline and compressed natural gas (CNG) are an intermediate and alternative step to dedicated CNG engines. The conversion to bi-fuel CNG engine could be a short-term solution to air pollution problem in many developing countries. In this paper a mathematical model of a bi-fuel four-stroke spark ignition (SI) engine is presented for comparative studies and analysis. It is based on the two-zone combustion model, and it has the ability to simulate turbulent combustion. The model is capable of predicting the cylinder temperature and pressure, heat transfer, brake work , brake thermal and volumetric efficiency, brake torque, brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). The effect of engine speed, equivalence ratio and performance parameters using gasoline and CNG fuels are analysed. The model has been validated by experimental data using the results obtained from a bi-fuel engine. The results show the capability of the model in terms of engine performance optimization and minimization of the emissions. The engine used in this study is a typical example of a modified bi-fuel engine conversion, which could benefit the researchers in the field

Simulating the Influence of Injection Timing, Premixed Ratio, and Inlet Temperature on Natural Gas / Diesel Dual-Fuel HCCI Combustion in a Diesel Engine

YesDual-fuel HCCI engines allow a relatively small quantity of diesel fuel to be used to ignite a variety of fuels such as natural gas or methane in HCCI mode. The gaseous fuel is mixed with the incoming air, and diesel fuel is sprayed into the cylinder by direct injection. Mathematical modelling is used to investigate the effects of parameters such as premixed ratio (fuel ratio) and pilot fuel injection timing on combustion of a dual-fuel HCCI engines. A CFD package is used with AVL FIRE software to simulate dual-fuel HCCI combustion in detail. The results establish a suitable range of premixed ratio and liquid fuel injection timing for low levels of NOx, CO and HC emissions along with a reliable and efficient combustion. Dual-fuel HCCI mode can increase NOx emission with lower premixed ratios in comparison to normal HCCI engines, but it is shown that the NOx emission reduces above a certain level of the premixed ratio. Due to the requirement of homogenous mixing of liquid fuel with air, the liquid fuel injection is earlier than for diesel engines. It is shown that, with careful control of parameters, dual-fuel HCCI engines have lower emissions in comparison with conventional engines

Optimization of the high-frequency torsional vibration of vehicle driveline systems using genetic algorithms

Vehicle drivelines with manual transmissions are exposed to different dynamic engine torques under driving conditions. Engine torque can dramatically vary with throttle demand from coast to drive condition and, conversely, with throttle release from drive to coast. Abrupt application or release of throttle in slow moving traffic or rapid engagement of the clutch can be followed by an audible response, referred to in industry as the clonk noise. This paper presents a complete dynamic model of a vehicle driveline for the optimization of high-frequency torsional vibration by the distributed-lumped (hybrid) modelling technique (DLMT). The model used is first validated against experimental tests. Parameter sensitivity studies have been carried out using the model to identify the important components affecting clonk. Three key parameters have been chosen from the parameter study. To optimize these key factors, genetic algorithms (GAs) have been used in this multi-parameter optimization problem. The GAs show significant reduction in the driveline noise, vibration and harshness (NVH)

Closed-loop system disturbance recovery.

NoThe regulation of linearized multivariable system models, following input set point and load disturbance changes, is considered. An inner and outer closed-loop control strategy is outlined, enabling targeted recovery rates, offset attenuation and low steady state interaction to be achieved. Proportional control and passive network compensation alone are employed. Gain ratio selection and outer loop tuning are exercised, ensuring thereby the confinement of output perturbations to low-frequency load disturbances and reference input changes. Application studies are presented for purposes of comparison

Automotive gas turbine regulation

NoA multivariable model of an automotive gas turbine, obtained from the linearized system equations is investigated. To facilitate vehicle speed changes, whilst protecting the system against thermal damage, control of the power turbine inlet gas temperature and gas generator speed is proposed by feedback regulation. Fuel flow and the power turbine nozzle area variations are the selected, manipulatable inputs. Owing to the limited control energy available for regulation purposes a multivariable, optimum, minimum control effort strategy is employed in the inner loop controller design study. Simulated, open and closed loop system responses are presented for purposes of comparison. Significant improvements in the transient response interaction reaction times and low steady state output interaction achieved using passive compensation and output feedback alone. Simplification of the closed loop configuration is proposed in the final implementation without performance penalties

Nonlinear Recursive Estimation With Estimability Analysis for Physical and Semiphysical Engine Model Parameters

A methodology for nonlinear recursive parameter estimation with parameter estimability analysis for physical and semiphysical engine models is presented. Orthogonal estimability analysis based on parameter sensitivity is employed with the purpose of evaluating a rank of estimable parameters given multiple sets of observation data that were acquired from a transient engine testing facility. The qualitative information gained from the estimability analysis is then used for estimating the estimable parameters by using two well-known nonlinear adaptive estimation algorithms known as extended Kalman filter (EKF) and unscented Kalman filter (UKF). The findings of this work contribute on understanding the real-world challenges which are involved in the effective implementation of system identification techniques suitable for online nonlinear estimation of parameters with physical interpretation

The torsional response of rotor systems.

NoThe torsional response of rotor systems comprising bearings, inertia discs, and relatively long, slim shafts is considered. Lumped, finite element and hybrid, distributed-lumped parameter procedures are employed to represent the rotor systems of concern in efforts aimed at increasing accuracy, integrity, and computational efficiency. Rotor, shaft, and bearing elements of arbitrary dimensions, constructed from materials with differing mechanical properties, can be accommodated within the system models formulated. General results for multiple rotor assemblies are derived. Simple computational techniques are employed to obtain the frequency response and time domain characteristics for the models proposed. Analytical validation of the resonance conditions identified is provided. Application studies are presented for purposes of comparison

Turbine blade vibration measurement methods for turbocharges

NoThis paper presents and compares the most important and often used methods to measure turbine blade vibrations: use of strain gauges and telemetry system which is an intrusive method or, on the other site. The Blade Tip Timing (BTT) method known as Non-Intrusive Stress Measurement (System) NSMS. Both methods have advantages and disadvantages which are described below. This paper focused on synchronous vibrations, which are more important in terms of turbine blades fatigue prediction and design optimization

Dynamic modeling of a transient engine test cell for cold engine testing applications

NoThe increasing complexity in the development and manufacturing process of internal combustion engines leads to a higher demand for more effective testing and monitoring methods. Cold engine testing becomes progressively the main End-of-Line test which is used nowadays from automotive engine manufacturers with the purpose of determining the integrity of engine assembly. The present work is focused on the development of a detailed physics-based, lumped-parameter, dynamic model of a single cylinder internal combustion engine coupled with an alternating current transient dynamometer for cold engine testing applications. The overall transient engine test cell model is described based on a two-inertia system model consisting of the engine, the dynamometer and the coupling shaft. The internal combustion engine is modelled based on First Law of Thermodynamics and Second Newton’s Law for rotational bodies. The transient dynamometer is actually an alternating current three-phase induction motor which is modelled according to direct-quadrature axis approach, and its drive unit which is responsible for controlling the speed of the motor using indirect field orientation scheme. The engine and dynamometer are connected through a coupling shaft which is modelled as a compliant member with damping. The model is validated against experimental measurements such as engine cylinder pressure, engine excitation torque and alternating currents of the induction motor. All of the experimental measurements were recorded from an identical single cylinder transient engine test cell using a highly advanced instrumentation system. The described model serves as an ideal platform for developing innovative model-based fault detection and diagnosis techniques for cold engine testing applications. In conclusion, this is presented successfully for two simulated fault cases, a process fault and a sensor fault, proving the functionality and usefulness of the model