Search Results

One of the most critical challenges currently facing the diesel engine industry is how to improve fuel economy under emission regulations. Improvement in fuel economy can be achieved by precisely controlling Air/Fuel ratio and by monitoring fuel consumption in real time. Accurate and repeatable measurements of fuel rate play a critical role in successfully controlling air/fuel ratio and in monitoring fuel consumption. Volumetric and gravimetric measurements are well-known methods for measuring fuel consumption of internal combustion engines. However, these methods are not suitable for obtaining fuel flow rate data used in real-time control/measurement. In this paper, neural networks are used to solve the problem concerning discontinuous data of fuel flow rate measured by using an AVL 733 s fuel meter. The continuous parts of discontinuous fuel flow rate are used to train and validate a neural network, which can then be used to predict the discontinuous parts of the fuel flow rate.

Multiple-injection strategy for Premixed Charge Compression Ignition (PCCI) combustion was investigated in a four-valve, direct-injection diesel engine by CFD simulation using KIVA-3V code [ 1 ] coupled with detailed chemistry. The effects of fuel splitting proportion, injection timing, included spray angles, injecting velocity, and the combined effects of injection parameters and EGR rate and boost pressure were examined. The mixing process and formations of soot emission and NO x were investigated as the main concern of the research. The results show that the fuel splitting proportion and the injection timing significantly impacted the combustion and emissions due to the considerable changes of the mixing process and fuel distribution in cylinder. The soot emission and unburned HC (UHC) were affected by included spray angles since the massive influences of the fuel distribution resulted from the change in spray targeting point on piston bowl.

Variable compression ratio in conjunction with a control system is an effective way to improve performance and reduce emissions in a diesel engine. There are various methods that may be employed that include geometry changes and varying valve timing to change the effective compression ratio. In this paper, a simulation study is presented that is based on a modern, multi-cylinder, fixed compression ratio diesel engine equipped with exhaust gas recirculation (EGR) and a variable geometry turbocharger (VGT). The engine is represented using the GT-Power code, and includes a predictive combustion model. The aim of the investigation is to identify the impact of variable compression ratio on fuel economy and emission reduction and whether realistic optimal conditions exist. This paper describes how a formal design of experiments procedure is used to define the simulation conditions. Cost functions are defined with different weights for fuel consumption, NOx and soot emissions.

Variable valve actuation in heavy duty diesel engines is not well documented, because of diesel engine feature, such as, unthrottled air handling, which gives little room to improve pumping loss; a very high compression ratio, which makes the clearance between the piston and valve small at the top dead center. In order to avoid strike the piston while maximizing the valve movement scope, different strategies are adopted in this paper: (1) While exhaust valve closing is fixed, exhaust valve opening is changed; (2) While exhaust valve closing is fixed, late exhaust valve opening: (3) While inlet valve opening is fixed, inlet valve closing is changed; (4) Delayed Inlet valve and exhaust valve openings and closings; (5) Changing exhaust valve timing; (6) changing inlet valve timing; (7) Changing both inlet and exhaust timing, will be used.

The injection timing of a Diesel internal combustion engine typically follows a prescribed sequence depending on the operating condition using open loop control. Due to advances in sensors and digital electronics it is now possible to implement closed loop control based on in cylinder pressure values. Typically this control action is slow, and it may take several cycles or at least one cycle (cycle-to-cycle control). Using high speed sensors, it becomes technically possible to measure pressure deviations and correct them within the same cycle (intra-cycle control). For example the in cylinder pressure after the pilot inject can be measured, and the timing of the main injection can be adjusted in timing and duration to compensate any deviations in pressure from the expected reference value. This level of control can significantly reduce the deviations between cycles and cylinders, and it can also improve the transient behavior of the engine.

A three-pulse fuel injection mode has been studied by implementing two-input-two-output (2I2O) control of both peak combustion pressure (Pmax) and indicated mean effective pressure (IMEP). The engine test results show that at low engine speed, the first main injection duration and the second main injection duration are able to be used to control Pmax and IMEP respectively. This control is exercised within a limited but promising area of the engine map. However, at high engine speed, Pmax and IMEP are strongly coupled together and then can not be separately controlled by the two control variables: the first and the second main injection duration. A simple zero-dimensional (0D) combustion model together with correlation analysis method was used to find out why the coupling strength of Pmax and IMEP increases with engine speed increased.

Multi-dimensional models coupled with a reduced chemical mechanism were used to investigate the effect of fuel on exergy destruction fraction and sources in a reactivity controlled compression ignition (RCCI) engine. The exergy destruction due to chemical reaction (Deschem) makes the largest contribution to the total exergy destruction. Different from the obvious low temperature heat release (LTHR) behavior in gasoline/diesel RCCI, methanol has a negative effect on the LTHR of diesel, so the exergy destruction accumulation from LTHR to high temperature heat release (HTHR) can be avoided in methanol/diesel RCCI, contributing to the reduction of Deschem. Moreover, the combustion temperature in methanol/diesel RCCI is higher compared to gasoline/diesel RCCI, which is also beneficial to the lower exergy destruction fraction. Therefore, the exergy destruction of methanol/diesel RCCI is lower than that of gasoline/diesel RCCI at the same combustion phasing.

Syngas is considered to be a promising alternative fuel for the dual-fuel reactivity controlled compression ignition (RCCI) engine to reduce the fuel consumption and emissions. However, the optimal syngas compositions and fuel supply strategies in RCCI combustion are significantly affected by engine configurations, which have not been investigated yet. In this study, by integrating the KIVA-3V code and the non-dominated sort genetic algorithm II (NSGA-II), the optimizations for a 0.477 L single-cylinder engine with shallow/wide piston bowl (Engine A) and a 1.325 L single-cylinder engine with conventional omega-type piston (Engine B) under the syngas/diesel RCCI combustion were performed. The optimized operating parameters include the fuel-supply strategies, syngas compositions, and intake conditions. The results indicate that the fuel-supply strategy is flexible in Engine A due to the shallow/wide piston bowl and the relatively small cylinder bore.

Engine electrification is a critical technology in the promotion of engine fuel efficiency, among which the electrified turbocharger is regarded as the promising solution in engine downsizing. By installing electrical devices on the turbocharger, the excess energy can be captured, stored, and re-used. The electrified turbocharger consists of a variable geometry turbocharger (VGT) and an electric motor (EM) within the turbocharger bearing housing, where the EM is capable in bi-directional power transfer. The VGT, EM, and exhaust gas recirculation (EGR) valve all impact the dynamics of air path. In this paper, the dynamics in an electrified turbocharged diesel engine (ETDE), especially the couplings between different loops in the air path is analyzed. Furthermore, an explicit principle in selecting control variables is proposed. Based on the analysis, a model-based multi-input multi-output (MIMO) decoupling controller is designed to regulate the air path dynamics.

A control strategy has been designed for a city bus equipped with a pneumatic hybrid propulsion system. The control system design is based on the precise management of energy flows during both energy storage and regeneration. Energy recovered from the braking process is stored in the form of compressed air that is redeployed for engine start and to supplement the engine air supply during vehicle acceleration. Operation modes are changed dynamically and the energy distribution is controlled to realize three principal functions: Stop-Start, Boost and Regenerative Braking. A forward facing simulation model facilitates an analysis of the vehicle dynamic performance, engine transient response, fuel economy and energy usage.

Dimethyl ether (DME) attracts increasing attentions in recent years, because it can reduce the carbon monoxide (CO), unburned hydrocarbon (HC), and soot emissions for engines as the transportation fuel or the fuel additive. In this paper, a reduced DME oxidation mechanism is developed using the decoupling methodology. The rate constants of the fuel-related reactions are optimized using the non-dominated sorting genetic algorithm II (NSGA-II) to reproduce the ignition delay times in shock tubes and major species concentrations in jet-stirred reactors (JSR) over low-to-high temperatures. In NSGA-II, the range of the rate constants was considered to ensure the reliability of the optimized mechanism. Moreover, an improved objective function was proposed to maintain the faithfulness of the optimized mechanism to the original reaction mechanism, and a new method was presented to determine the optimal solution from the Pareto front.

When a diesel engine is running at steady state, the diesel combustion process still has some level of variation from cycle to cycle, even if engine load and all control inputs are fixed. This variation is a disturbance for the speed governor, and it could lead to less than optimal engine performance in terms of fuel economy, exhaust gas emission and noise emission. The most effective way to reduce this steady state combustion variation is by applying fuel path feedback control. The control action can be performed at a fixed frequency, or at a defined cycle event time. Intra-cycle control has the highest capacity to suppress the combustion deviation, as it measures the current cycle combustion performance and compensates for it within the same cycle using a very fast control response. Correct knowledge and a model of the disturbance sources and combustion variation patterns are essential in the design process of this intra-cycle control strategy.

In this paper an initial dynamic analysis of the Libralato rotary engine prototype is conducted based on a joint engine model. Through the investigation of the Libralato thermodynamic cycle and the geometry characteristics of the engine structure, a multi-chamber core engine model is developed via GT-Power, a commercial software. The whole engine working volume is divided into 5 parts, including an intake chamber, a compression chamber, a combustion chamber, an expansion chamber and a virtual chamber which is used to correct the actual volume variation of the expansion chamber at the end of expansion stroke. The performance of the developed model is validated by experimental results. Then an initial analysis on the engine thermodynamic cycle, the engine operation characteristics and the gas exchange process is conducted. Furthermore, a multi-body mechanism model is designed to analyze the mechanical properties of the engine.

Energy recovery from IC engines has proved to be of considerable interest across the range of vehicle applications. The motivation is substantial fuel economy gain that can be achieved with a minimal affect on the “host” technology of the vehicle. This paper reviews the initial results of a research project whose objective has been to identify system concepts and control methods for thermal recovery techniques. A vapour power cycle is the means of energy transfer. The architecture of the system is considered along with support of the fuel economy claims with the results of some hybrid vehicle modelling. An overview of the latest experimental equipment and design of the heat exchanger is presented. The choice of control architecture and strategy, whose goal is overall efficiency of the engine system, is presented and discussed. Some initial control results are presented.

The objective of the work reported in this paper was to identify how turbocharger response time (“turbo-lag”) is best managed using pneumatic hybrid technology. Initially methods to improve response time have been analysed and compared. Then the evaluation of the performance improvement is conducted using two techniques: engine brake torque response and vehicle acceleration, using the engine simulation code, GT-SUITE [1]. Three pneumatic hybrid boost systems have been considered: Intake Boost System (I), Intake Port Boost System (IP) and Exhaust Boost System (E). The three systems respectively integrated in a six-cylinder 7.25 l heavy-duty diesel engine for a city bus application have been modelled. When the engine load is increased from no load to full load at 1600 rpm, the development of brake torque has been compared and analysed. The findings show that all three systems significantly reduce the engine response time, with System I giving the fastest engine response.

Diesel homogeneous charge compression ignition (HCCI) engines with early injection can result in significant spray/wall impingement which seriously affects the fuel efficiency and emissions. In this paper, the spray/wall interaction models which are available in the literatures are reviewed, and the characteristics of modeling including spray impingement regime, splash threshold, mass fraction, size and velocity of the second droplets are summarized. Then three well developed spray/wall interaction models, O'Rourke and Amsden (OA) model, Bai and Gosman (BG) model and Han, Xu and Trigui (HXT) model, are implemented into KIVA-3V code, and validated by the experimental data from recent literatures under the conditions related to diesel HCCI engines. By comparing the spray pattern, droplet mass, size and velocity after the impingement, the thickness of the wall film and vapor distribution with the experimental data, the performance of these three models are evaluated.

For diesel engines, fuel path control plays a key role in achieving optimal emissions and fuel economy performance. There are several fuel path parameters that strongly affect the engine performance by changing the combustion process, by modifying for example, start of injection and fuel rail pressure. This is a multi-input multi-output problem. Linear Model Predictive Control (MPC) is a good approach for such a system with optimal solution. However, fuel path has fast dynamics. On-line optimisation MPC is not the good choice to cope with such fast dynamics. Explicit MPC uses off-line optimisation, therefore, it can be used to control the system with fast dynamics.

While it is generally agreed that the PEM fuel cell technology is best for road vehicles, the need for a source of relatively pure hydrogen poses significant challenges. There are two distinct options that are currently being considered: On-board processing of gasoline or methanol Fueling with hydrogen gas made in an off-board facility Each option has different implications for the fueling infrastructure and for the technologies required both on- and off-board the vehicle. In addition, various fueling strategies shift the balance of risk between fuel providers and vehicle manufacturers. Generally speaking, alternative fueling options can be seen to trade off technical risk (e.g., will it work?) for commercial risk (e.g., will anyone buy it?). In seeking a satisfactory business solution, a key issue is the balance between these two risks on the part of the vehicle manufacturer and the fuel provider.

The pursuit of fuel economy is forcing technology change across the range of control and engine management technologies. Improved thermal management has been addressed in order to promote fast warm-up, improved exhaust gas after-treatment performance, and lower variance in combustion through a consistent and high cylinder head temperature. Temperature management of exhaust gas is of increasing interest because of the need to maintain efficiency in after-treatment devices. More effective temperature management places requirements on heat exchange systems, and offers the potential for bottoming and heat recovery cycles that use energy transferred from the exhaust stream. Turbo-compounding is already established in heavy duty engines, where a reduction in exhaust gas temperature is the consequence of an additional stage of expansion through an exhaust turbine. A new project in electric turbo-compounding offers flexibility in the control of energy extracted from the exhaust stream[1].

More and more stringent emission regulations require advanced control technologies for combustion engines. This goes along with increased monitoring requirements of engine behaviour. In case of emissions behaviour and fuel consumption the actual combustion efficiency is of highest interest. A key parameter of combustion conditions is the in-cylinder pressure during engine cycle. The measurement and detection is difficult and cost intensive. Hence, modelling of in-cylinder conditions is a promising approach for finding optimum control behaviour. However, on-line controller design requires real-time scenarios which are difficult to model and current modelling approaches are either time consuming or inaccurate. This paper presents a new approach of in-cylinder condition prediction. Rather than reconstructing in-cylinder pressure signals from vibration transferred signals through cylinder heads or rods this approach predicts the conditions.