Exhaust Manifold Pressure Research Articles

Finite-frequency fuzzy fault-tolerant static output feedback H∞ control for Diesel engine air-path system

This paper focuses on the design of H∞ finite-frequency (FF) fault-tolerant static output feedback (FTSOFC) problem of Diesel engine air-path system with consideration of external disturbances and actuator faults. Initially, a Diesel engine air-path nonlinear model is described by Takagi-Sugeno (T-S) fuzzy model based descriptor approach. The aim is to regulate intake and exhaust manifold pressures to the desired reference pressures by controlling the Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) valves. Then, the robust integrator-based control strategy is developed to track the desired reference signals despite the presence of disturbances and actuator faults. By using the extended Generalized Kalman Yakubovich Popov (GKYP) lemma, Lyapunov functions and independent slack matrices, sufficient conditions are established to ensure both the good tracking of reference pressures and the prescribed H∞ performance with FF domain of the fuel flow variation and actuator faults. Finally, simulation results are given to demonstrate the effectiveness of the proposed approach.

Exhaust valve profile modulation for improved diesel engine curb idle aftertreatment thermal management

Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulation as a technique to increase engine-outlet temperature for ATS thermal management, without requiring modulation of exhaust manifold pressure. Experimental steady state results at 800 RPM/1.3 bar BMEP (curb idle) demonstrate that early exhaust valve opening with negative valve overlap (EEVO+NVO) can achieve engine-outlet temperature in excess of 255°C with 5.7% lower fuel consumption, 12% lower engine out NOx and 20% lower engine-out soot than the conventional thermal management strategy. Late exhaust valve opening with internal EGR via reinduction (LEVO+Reinduction) resulted in engine-outlet temperature in excess of 280°C, while meeting emission constraints at no fuel consumption penalty. This work also demonstrates that LEVO in conjunction with modulation of exhaust manifold pressure results in engine-outlet temperature in excess of 340°C while satisfying desired emission constraints. Aggressive use of LEVO can result in engine-outlet temperatures of 460°C, capable of active regeneration of DPF at curb idle, without the significant increase in engine-out soot emissions seen in previously studied strategies.

Automated synthesis of a local model network based nonlinear model predictive controller applied to the engine air path

The efficient and emission reducing control of the air path of an internal combustion engine is a challenging task due to its nonlinear and multivariate nature. By applying the well-known local model network approach to describe the nonlinear process in terms of linear operating point approximations, a fast and efficient model generation through data-driven system identification can be achieved. In this paper it is demonstrated how a nonlinear multivariate model predictive controller can be synthesised from the identified model directly by exploiting its representation in flatness coordinates. For the proposed controller, a compactly formulated quadratic programme results. Because of the uniform representation of all local models in controllability canonical form, a state observer is rendered unnecessary. Additionally, input and output constraints can be taken into account in the optimisation directly. The effectiveness of the control scheme is demonstrated successfully in jointly controlling the exhaust manifold pressure and the engine out NOx concentration for a heavy-duty engine on the testbed.

Influence of Pre-Turbine Small-Sized Oxidation Catalyst on Engine Performance and Emissions under Driving Conditions

The earlier activation of the catalytic converters in internal combustion engines is becoming highly challenging due to the reduction in exhaust gas temperature caused by the application of CO2 reduction technologies. In this context, the use of pre-turbine catalysts arises as a potential way to increase the conversion efficiency of the exhaust aftertreatment system. In this work, a small-sized oxidation catalyst consisting of a honeycomb thin-wall metallic substrate was placed upstream of the turbine to benefit from the higher temperature and pressure prior to the turbine expansion. The change in engine performance and emissions in comparison to the baseline configuration are analyzed under driving conditions. As an individual element, the pre-turbine catalyst contributed positively with a relevant increase in the overall CO and HC conversion efficiency. However, its placement produced secondary effects on the engine and baseline aftertreatment response. Although small-sized monoliths are advantageous to minimize the thermal inertia impact on the turbocharger lag, the catalyst cross-section is in trade-off with the additional pressure drop that the monolith causes. As a result, the higher exhaust manifold pressure in pre-turbine pre-catalyst configuration caused a fuel consumption increase higher than 3% while the engine-out CO and HC emissions did around 50%. These increments were not completely offset despite the high pre-turbine pre-catalyst conversion efficiency (>40%) because the partial abatement of the emissions in this device conditioned the performance of the close-coupled oxidation catalyst.

Study on Altitude Adaptability of a Turbocharged Off-Road Diesel Engine

Abstract This paper investigates the operating characteristics of an off-road diesel engine to enhance its power performance in plateau. First, the impacts of altitude on the power, fuel economy, and emissions characteristics were analyzed by a bench test. Second, the combustion and overall performance working at different altitudes were studied by three-dimensional numerical simulation, including the relationship between fuel injection parameters and engine performance. The results showed that altitude significantly affects the performance of the off-road diesel engine. As the altitude increased from 0 m to 2000 m, the engine power decreased as much as 4.3%, and the brake-specific fuel consumption (BSFC) increased as much as 6%. At the peak torque condition, the intake manifold boost pressure and the exhaust manifold pressure both reduced with a rise of altitude, while the intake and exhaust manifold temperatures both increased with a rise of altitude. Finally, after comparing the in-cylinder flow conditions and combustion characteristics given by six combustion chamber designs that have different shrinkage ratios, the engine performance at 4000 m altitude with five different fuel spray angles were further optimized. The engine rated power increased by 8.2% when the shrinkage ratio was 7.28% and the fuel spray angle was 150 deg at the 4000 m altitude.

Controller structure for high response engine exhaust throttles

Exhaust throttles are widely used as cost-effective endurance brakes on commercial vehicle diesel engines. To fulfil the requirements as endurance brakes exhaust flaps have only two states: fully opened and fully closed. However, there are several possible new applications, suggested by the authors, in which exhaust throttles could be utilised. To provide these functionalities a backpressure controller that can adjust the exhaust manifold pressure arbitrarily is needed. In this paper, the design and performance evaluation of an exhaust pressure controller is described. A first engineering principle-based, mean-value, nonlinear model of the engine and the actuator is described and validated with test bench measurements. Based on the nonlinear model a feedforward term was obtained. As feedback, an LQ servo controller was designed. The controller performance and the compliance of requirements was evaluated in three different test cycles on a medium-duty diesel engine, simulating brake blending, thermomanagement, and EGR support operations.

Nonlinear observer-based exhaust manifold pressure estimation and fault detection for gasoline engines with exhaust gas recirculation

This article presents a nonlinear observer-based method to estimate the exhaust manifold pressure for the gasoline engines equipped with an exhaust gas recirculation system. A dynamic model is designed to estimate the exhaust manifold pressure, which includes both the intake manifold and exhaust manifold dynamics focusing on gas mass flows. Based on the developed model, a nonlinear exhaust manifold pressure observer is proposed to replace the exhaust manifold pressure sensor, and the global convergence is analyzed by a constructed Lyapunov function and the physical meaning of the time-varying parameters. The experimental validations show that the observer-based exhaust manifold pressure estimator is able to converge to the real value at arbitrary initial value and estimates the exhaust manifold pressure accurately during both the steady-state and transient conditions. Finally, the proposed exhaust manifold pressure observer is applied into the fault detection problem for the exhaust gas recirculation system. The experimental validations show that the observer is able to be used to estimate the exhaust gas recirculation ratio and as an extra signal to assist to detect the faults of the exhaust gas recirculation system accurately.

Strategies for using valvetrain flexibility instead of exhaust manifold pressure modulation for diesel engine gas exchange and thermal management control

At low-to-moderate loads, modern diesel engines manipulate exhaust manifold pressure to drive exhaust gas recirculation and thermally manage the aftertreatment. In these engines, exhaust manifold pressure control is typically achieved via either a valve after the turbine, a variable geometry turbine, or wastegating. The study described here demonstrates how valvetrain flexibility enables engine operation without requiring exhaust manifold pressure control. Specifically, intake valve closure modulation and cylinder deactivation at elevated engine speeds, along with exhaust valve opening modulation at low engine speeds, can match, or improve, efficiency and thermal management compared to a stock thermal calibration that requires exhaust manifold pressure control. During low-speed, low-load operation, the stock engine uses elevated exhaust manifold pressures to increase the required fueling (for thermal management) and to drive exhaust gas recirculation. Exhaust valve opening modulation can instead be implemented to enable similar aftertreatment warm-up, while cylinder deactivation allows aftertreatment temperature maintenance with a 40% reduction in fuel consumption. During high-speed, low-to-moderate loads, the stock engine implements thermal management operation by decreasing exhaust manifold pressure. Intake valve closure modulation together with cylinder deactivation can instead be implemented to enable fuel-efficient thermal management improvements via charge flow control.

Impact of Cylinder Deactivation and Cylinder Cutout via Flexible Valve Actuation on Fuel Efficient Aftertreatment Thermal Management at Curb Idle

Cylinder deactivation (CDA) and cylinder cutout are different operating strategies for diesel engines. CDA includes the deactivation of both the valve motions and the fuel injection of select cylinders, while cylinder cutout incorporates only fuel injection deactivation in select cylinders. This study compares diesel engine aftertreatment thermal management improvements possible via CDA and cylinder cutout at curb idle operation (800 RPM and 1.3 bar BMEP). Experiments and analysis demonstrated that both CDA and cylinder cutout enable improved fuel efficient “stay warm” thermal management compared to a stock thermal calibration on a Clean Idle Certified engine. At curb idle, this stock calibration depends on elevated exhaust manifold pressure to increase the required fueling (for thermal management) and to drive EGR. The study described here demonstrates that CDA does not require an elevated exhaust manifold pressure for thermal management or EGR delivery control, whereas cylinder cutout does. In addition to achieving engine-out NOx levels no higher than the stock thermal calibration, both cylinder cutout and CDA enable up to 55% and 80% reductions in particulate matter (PM), respectively. Cylinder cutout demonstrates 17% fuel savings, while CDA demonstrates 40% fuel savings, over the stock six-cylinder thermal calibration. These fuel efficiency improvements primarily result from reductions in pumping work via reduced air flow through the engine. Cylinder cutout reduces the air flow rate via elevated amounts of recirculated gases which are also required to regulate engine-out NOx, resulting in a larger delta pressure across the engine and consequently more pumping work than CDA. CDA reduces the air flow rate by deactivating cylinders, which reduces the charge flow rate and enables a small delta pressure between the intake and exhaust manifolds, resulting in less pumping work by the cylinders. As a result, CDA is more efficient than cylinder cutout. Furthermore, the thermal merits of cylinder cutout require high exhaust manifold pressures, and are subject to the configuration of the exhaust manifold and the exhaust gas recirculation (EGR) path.

Robust Adaptive Controller for the Diesel Engine Air Path with Input Saturation

In this paper, we design an adaptive controller for the diesel engine air path with a priori consideration of actuator saturation effects to regulate the exhaust manifold pressure and the compressor flow rate. The originality of the proposed approach is the integration of an auxiliary system to compensate the saturation effects. Simulation results of the diesel engine air path are given to show the efficiency of the proposed approach.

Nonlinear observer-based control design and experimental validation for gasoline engines with EGR

This paper presents a nonlinear observer-based control design approach for gasoline engines equipped with exhaust gas recirculation (EGR) system. A mean value engine model is designed for control which includes both the intake manifold and exhaust manifold dynamic focused on gas mass flows. Then, the nonlinear feedback controller based on the developed model is designed for the state tracking control, and the stability of the close loop system is guaranteed by a constructed Lyapunov function. Since the exhaust manifold pressure is usually unmeasurable in the production engines, a nonlinear observer-based feedback controller is proposed by using standard sensors equipped on the engine, and the asymptotic stability of the both observer dynamic system and control dynamic system are guaranteed with Lyapunov design assisted by the detail analysis of the model. The experimental validations show that the observer-based nonlinear feedback controller is able to regulate the intake pressure and exhaust pressure state to the desired values during both the steady-state and transient conditions quickly by only using the standard sensors.

Lyapunov-Based Nonlinear Feedback Control Design for Exhaust Gas Recirculation Loop of Gasoline Engines

For gasoline engine with an exhaust gas recirculation loop, a challenging issue is how to achieve maximum brake efficiency while providing the desired torque. This paper presents a solution to this challenging issue via dynamical control approach which consists of two phases: optimal equilibrium point generation and feedback regulation of the optimized operating mode. First, a mean-value model is developed to represent the dynamical behavior of the intake manifold and exhaust manifold focused on gas mass flows. Then, the control scheme is constructed based on the control-oriented model. Mainly, the optimal set-points are designed by solving the optimal programming problem of maximizing the brake efficiency under demand torque constraint which is the first control design stage, and the dynamical model to the feedback stabilization regulation control for improving transient performance is at the second stage. Lyapunov-based design is used for the derivation of the state feedback law. Furthermore, the proposed exhaust manifold pressure estimator is also coupled into the controller to replace the cost prohibitive exhaust pressure sensor. Finally, experimental validations on the test bench are provided to evaluate the proposed controller.

High efficiency ethanol-diesel dual-fuel combustion: A comparison against conventional diesel combustion from low to full engine load

Comparisons between dual-fuel combustion and conventional diesel combustion (CDC) are often performed using different engine hardware setups, exhaust gas recirculation rates, as well as intake and exhaust manifold pressures. These modifications are usually made in order to curb in-cylinder pressure rise rates and meet exhaust emissions targets during the dual-fuel operation. To ensure a fair comparison, an experimental investigation into dual-fuel combustion has been carried out from low to full engine load with the same engine hardware and identical operating conditions to those of the CDC baseline. The experiments were executed on a single cylinder heavy-duty diesel engine at a constant speed of 1200 rpm and various steady-state loads between 0.3 and 2.4 MPa net indicated mean effective pressure (IMEP). Ethanol was port fuel injected while diesel was direct injected using a high pressure common rail injection system. The start of diesel injection was optimised for the maximum net indicated efficiency in both combustion modes. Varied ethanol energy fractions and different diesel injection strategies were required to control the in-cylinder pressure rise rate and achieve highly efficient and clean dual-fuel operation. In terms of performance, dual-fuel combustion attained higher net indicated efficiency than the CDC mode from 0.6 to 2.4 MPa IMEP, with a maximum value of 47.2% at 1.2 MPa IMEP. The comparison also shows the use of ethanol resulted in 26% to 90% lower nitrogen oxides (NOx) emissions than the CDC operation. At the lowest engine load of 0.3 MPa IMEP, the dual-fuel operation led to simultaneous low NOx and soot emissions at the expense of a relatively low net indicated efficiency of 38.9%. In particular, the reduction in NOx emissions introduced by the utilisation of ethanol has the potential to decrease the engine running costs via lower consumption of aqueous urea solution in the selective catalyst reduction system. Moreover, the dual-fuel combustion with a low carbon fuel such as ethanol is an effective means of decreasing the use of fossil fuel and associated greenhouse gas emissions.

Exhaust Pressure Estimation for Diesel Engines Equipped With Dual-Loop EGR and VGT

This paper describes an observer design method that estimates the exhaust manifold pressure in a diesel engine with limited sensor information. In the modern model-based control of air flows, information on the exhaust pressure is often necessary for control stability. However, it is not easy to measure the exhaust pressure with sensors due to the unfavorable environment for measurement and the high cost of sensors. Therefore, a robust observer, which is applicable to engines equipped with a dual-loop exhaust gas recirculation (EGR) system and a variable geometry turbine, is designed to estimate the exhaust pressure. The observer takes the form of a Luenberger-sliding mode observer in order to guarantee its asymptotic stability upon consideration of the model uncertainties. For research on state estimation and control of dual-loop EGR engines, information on the pressure states in the low pressure EGR loop must be provided. Hence, this paper also proposes an intuitive regression modeling method for the pressure states of the compressor inlet and turbine outlet with physical insights into the engine operation. Applying the regression models to the observer algorithm, the estimation performance of the exhaust pressure observer is verified experimentally in both steady state and transient conditions with a 6-L heavy-duty diesel engine.

Crank angle-resolved exergy analysis of exhaust flows in a diesel engine from the perspective of exhaust waste energy recovery

Exhaust waste energy recovery (WER) is a critical component in the portfolio of efficiency improvement strategies being considered for internal combustion engines. This paper addresses an important existing knowledge gap by introducing a methodology for performing crank angle-resolved exergy analysis of exhaust flows from the perspective of exhaust WER in diesel engines. To this end, a single-cylinder research engine (SCRE) operating in conventional diesel combustion mode was tested at a load of 5 bar brake mean effective pressure (BMEP), speeds of 1200 and 1500 rpm, and boost pressures of 1.2, 1.5, 2, and 2.4 bar. The crank angle-resolved specific exergy and its thermal and mechanical components were calculated by combining experimental crank angle-resolved exhaust manifold pressure measurements with 1D system-level (GT-POWER) simulations. In addition, exhaust flow specific exergies in the “blowdown” and “displacement” phases of the exhaust process, the total exergy flow rates, and cumulative (time-integrated) exergy were quantified. The results obtained show that low boost pressures led to the highest crank angle-resolved specific exergy, the lowest specific mechanical exergy, and the highest specific thermal exergy. In general, the specific thermal exergy was dominant during the initial phase of the exhaust process while the specific mechanical exergy became important after peak mass flow rate was attained. Regardless of engine speed, with increasing boost pressure, the mechanical component of the cumulative exergy in the exhaust flow increased while the thermal component decreased. Consequently, the results indicate that highly boosted conditions may be more appropriate for direct WER with positive displacement expanders that leverage the mechanical component of exhaust exergy while low boost operating conditions may be better suited for other WER strategies that utilize the thermal component of exhaust exergy.

Exhaust pressure LPV observer for turbocharged diesel engine on-board diagnosis

This paper deals with the estimation of the exhaust manifold pressure for a truck diesel engine equipped with a turbocharger. The knowledge of this variable is essential in order to fulfill functions such as the exhaust brake control or on-board diagnosis (OBD) of antipollution systems. However, while in most cases the pressure is directly measured, the sensor may encounter failures in some specific operating conditions. Its estimation is then of great interest for diagnosis and fault tolerant control objectives. Based on mean value models of the turbocharger and the exhaust manifold, a Linear Parameter Varying (LPV) polytopic observer is designed to provide an estimation of the pressure. The merits of this solution are illustrated with the high-fidelity professional simulator GT-POWER.

Nonlinear Model Predictive Controller Design for Air System Control of Variable Geometry Turbocharged Diesel Engine

Variable geometry turbocharger (VGT) is a key technology and has become a development trend in the diesel engine industry because it can reduce turbo lag and improve fuel economy. In this paper, nonlinear model predictive control (NMPC) method for VGT is developed to solve the air system control problem of turbocharged diesel engine. Firstly, a model of the turbocharged diesel engine was built in AMESim. Secondly, the desired torque is converted into the desired exhaust manifold pressure through the look-up table. Thirdly, The VGT controller based on NMPC is designed to achieve the desired exhaust manifold pressure tracking while considering constraints on the system input and output. Finally, the effectiveness of the VGT controller is verified.

Advanced Air Path Control in Diesel Engines Accounting for Variable Operational Conditions

In this paper, we develop an extended linear parameter-varying (LPV) model to design an LPV controller for air path system control in diesel engines. The objective is to use a widely used and accepted nonlinear diesel engine air path model, minimize simplifying assumptions on the model, and then design a model-based gain scheduling controller to work in a wide range of engine operating points. To that end, we transform the nonlinear model to linear parameter-varying form by defining state-dependent inputs and scheduling parameters. Some of the defined state-dependent scheduling parameters are synthetic in the sense that they are not obvious from the model and are created through algebraic operations. The control law we design is parameter-dependent and allows a large range of operating points to be considered. The robust performance of the controller (with respect to parametric uncertainties in the control design model) under variable operating points (depending on engine speed, fuel flow rate, and intake-exhaust manifold temperatures) is tested on simulations by tracking reference exhaust manifold pressure and compressor air mass flow signals. Finally, the performance of the designed extended LPV controller is compared to an H∞ controller and to an LPV controller from the existing literature to see its superior performance under variable operating points.

Nonlinear observer based sliding mode control and oxygen fraction estimation for diesel engine

In this paper, a nonlinear observer based sliding mode control (NOSMC) approach for air-path and a model-based observer for oxygen concentration in the diesel engine equipped with a variable geometry turbocharger and exhaust gas recirculation is introduced. We propose a less conservative observer design technique for Lipschitz nonlinear systems using Ricatti equations. The observer gains are obtained by solving the linear matrix inequality (LMI). Then a robust nonlinear control method, sliding mode control is applied for the states of intake and exhaust manifold pressure and compressor mass flow rate for the sake of the minimization of emissions. The proposed NOSMC controller is applied on a mean value model of turbocharged diesel engine. Besides this, a model-based observer is developed to estimate the oxygen concentration in the intake and exhaust manifolds owing to its significance in reducing emissions of diesel engines. The validation and efficiency of the proposed method are demonstrated by AMESim and Matlab/Simulink co-simulation results.

Exhaust pulse energy harvesting - an experimental investigation on a single cylinder research engine

This paper discusses the theoretical potential of direct exhaust pulse energy harvesting, specifically through a proposed theoretical expander device. A detailed review of pertinent literature determined that there has been little focus specifically on directly converting exhaust pulse energy into useful power. Crank position resolved exhaust pressure was measured as engine load and speed were varied in a single cylinder research (diesel) engine. Potential theoretical improvements average a 12% reduction in overall indicated specific fuel consumption with respect to baseline for the tested operating conditions. Additional parametric studies quantify the effects of intake manifold pressure, exhaust manifold pressure, engine speed and load on measured instantaneous exhaust pressures. Together, these observations are expected to provide a wide range of experimental data to anchor CFD and phenomenological models, which can be used to design viable expander geometries to optimally harness exhaust waste energy in light and heavy-duty engines.