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Author: Christopher J. Chadwell
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Category :
Languages : en
Pages : 14
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Author: Christopher J. Chadwell
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Category :
Languages : en
Pages : 14
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Author: Göran Haraldsson
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Category :
Languages : en
Pages : 17
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Languages : en
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The central objective of the proposed work is to demonstrate an HCCI (homogeneous charge compression ignition) capable SI (spark ignited) engine that is capable of fast and smooth mode transition between SI and HCCI combustion modes. The model-based control technique was used to develop and validate the proposed control strategy for the fast and smooth combustion mode transition based upon the developed control-oriented engine; and an HCCI capable SI engine was designed and constructed using production ready two-step valve-train with electrical variable valve timing actuating system. Finally, smooth combustion mode transition was demonstrated on a metal engine within eight engine cycles. The Chrysler turbocharged 2.0L I4 direct injection engine was selected as the base engine for the project and the engine was modified to fit the two-step valve with electrical variable valve timing actuating system. To develop the model-based control strategy for stable HCCI combustion and smooth combustion mode transition between SI and HCCI combustion, a control-oriented real-time engine model was developed and implemented into the MSU HIL (hardware-in-the-loop) simulation environment. The developed model was used to study the engine actuating system requirement for the smooth and fast combustion mode transition and to develop the proposed mode transition control strategy. Finally, a single cylinder optical engine was designed and fabricated for studying the HCCI combustion characteristics. Optical engine combustion tests were conducted in both SI and HCCI combustion modes and the test results were used to calibrate the developed control-oriented engine model. Intensive GT-Power simulations were conducted to determine the optimal valve lift (high and low) and the cam phasing range. Delphi was selected to be the supplier for the two-step valve-train and Denso to be the electrical variable valve timing system supplier. A test bench was constructed to develop control strategies for the electrical variable valve timing (VVT) actuating system and satisfactory electrical VVT responses were obtained. Target engine control system was designed and fabricated at MSU for both single-cylinder optical and multi-cylinder metal engines. Finally, the developed control-oriented engine model was successfully implemented into the HIL simulation environment. The Chrysler 2.0L I4 DI engine was modified to fit the two-step vale with electrical variable valve timing actuating system. A used prototype engine was used as the base engine and the cylinder head was modified for the two-step valve with electrical VVT actuating system. Engine validation tests indicated that cylinder #3 has very high blow-by and it cannot be reduced with new pistons and rings. Due to the time constraint, it was decided to convert the four-cylinder engine into a single cylinder engine by blocking both intake and exhaust ports of the unused cylinders. The model-based combustion mode transition control algorithm was developed in the MSU HIL simulation environment and the Simulink based control strategy was implemented into the target engine controller. With both single-cylinder metal engine and control strategy ready, stable HCCI combustion was achived with COV of 2.1% Motoring tests were conducted to validate the actuator transient operations including valve lift, electrical variable valve timing, electronic throttle, multiple spark and injection controls. After the actuator operations were confirmed, 15-cycle smooth combustion mode transition from SI to HCCI combustion was achieved; and fast 8-cycle smooth combustion mode transition followed. With a fast electrical variable valve timing actuator, the number of engine cycles required for mode transition can be reduced down to five. It was also found that the combustion mode transition is sensitive to the charge air and engine coolant temperatures and regulating the corresponding temperatures to the target levels during the combustion mode transition is the key for a smooth combustion mode transition. As a summary, the proposed combustion mode transition strategy using the hybrid combustion mode that starts with the SI combustion and ends with the HCCI combustion was experimentally validated on a metal engine. The proposed model-based control approach made it possible to complete the SI-HCCI combustion mode transition within eight engine cycles utilizing the well controlled hybrid combustion mode. Without intensive control-oriented engine modeling and HIL simulation study of using the hybrid combustion mode during the mode transition, it would be impossible to validate the proposed combustion mode transition strategy in a very short period.
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Languages : en
Pages : 5
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Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NOX emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model h as applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the intake temperature and the fuel flow rate. Satisfactory operation has been obtained over a wide range of operating conditions. Cylinder-to-cylinder variations play an important role in limiting maximum power, and should be controlled to achieve satisfactory performance.
Author: Kushal Narayanaswamy
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ISBN:
Category :
Languages : en
Pages : 226
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Author: R. Dibble
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Category :
Languages : en
Pages : 23
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This paper describes the technical approach for converting a Caterpillar 3406 natural gas spark ignited engine into HCCI mode. The paper describes all stages of the process, starting with a preliminary analysis that determined that the engine can be operated by preheating the intake air with a heat exchanger that recovers energy from the exhaust gases. This heat exchanger plays a dual role, since it is also used for starting the engine. For start-up, the heat exchanger is preheated with a natural gas burner. The engine is therefore started in HCCI mode, avoiding the need to handle the potentially difficult transition from SI or diesel mode to HCCI. The fueling system was modified by replacing the natural gas carburetor with a liquid petroleum gas (LPG) carburetor. This modification sets an upper limit for the equivalence ratio at {phi} {approx} 0.4, which is ideal for HCCI operation and guarantees that the engine will not fail due to knock. Equivalence ratio can be reduced below 0.4 for low load operation with an electronic control valve. Intake boosting has been a challenge, as commercially available turbochargers are not a good match for the engine, due to the low HCCI exhaust temperature. Commercial introduction of HCCI engines for stationary power will therefore require the development of turbochargers designed specifically for this mode of operation. Considering that no appropriate off-the-shelf turbocharger for HCCI engines exists at this time, we are investigating mechanical supercharging options, which will deliver the required boost pressure (3 bar absolute intake) at the expense of some reduction in the output power and efficiency. An appropriate turbocharger can later be installed for improved performance when it becomes available or when a custom turbocharger is developed. The engine is now running in HCCI mode and producing power in an essentially naturally aspirated mode. Current work focuses on developing an automatic controller for obtaining consistent combustion in the 6 cylinders. The engine will then be tested for 1000 hours to demonstrate durability. This paper presents intermediate progress towards development of an HCCI engine for stationary power generation and next steps towards achieving the project goals.
Author: Dusan Polovina
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Category :
Languages : en
Pages : 16
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Author: Jason Scott Souder
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Category :
Languages : en
Pages : 410
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Author: Varun Tandra
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Category :
Languages : en
Pages : 218
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With growing environmental concern, energy consumption has become a key element in the current debate on global warming. Over the past two decades, Homogeneous Charge Compression Ignition (HCCI) engine technology has aroused a great deal of interest in the automotive sector owing to its fuel flexibility and ability to generate ultra-low exhaust emissions. One of the strategies to achieve ultra-low emissions in HCCI engines is to retain some exhaust gas/burnt products in the cylinder by dynamically actuating/varying valve opening and closing timings and lifts. This can be achieved by recent advancements in microprocessor, actuators and controller technologies. The first step in the synthesis of control algorithms involves developing simple system-level mathematical models. This thesis presents two such mathematical models of HCCI combustion. In the first part of this thesis, a control-oriented two-zone thermo-kinetic model of a single cylinder HCCI engine is presented. Earlier control laws were derived using single zone mathematical models of HCCI combustion; however, such models fail to accurately capture the combustion dynamics of an HCCI engine owing to the assumption of homogeneous composition and temperature in the cylinder. Certain multi-zone models of HCCI engines emphasizing the shortcomings of these single zone models have also been reported in literature. However, such models are far too complex and unwieldy for the development of fast and efficient controllers for HCCI engines. The present work outlines the modeling approach of a physics based two-zone model of a single-cylinder HCCI engine by incorporating the first law of thermodynamics and the temperature and concentration inhomogeneities within the cylinder in order to better predict emissions, peak pressures, and timing. A comparative analysis between the single zone and two-zone models is also discussed. The nonlinear model was linearized about an operating point to facilitate the development of an effective LQR regulator. The model inputs include variable valve timing to effectively control peak pressures, exhaust temperatures and ignition timing. In the second part of the thesis we address the shortcomings of control analysis which to date has been done by developing models that are engine specific, such models often rely on extensive parameters which are to be experimentally identified. Moreover, further investigation revealed that these models were valid only for a narrow operating range. Therefore, a detailed mathematical model of an HCCI engine, which is fuel flexible and valid for transitions in engine speed, is developed based on ideal gas laws and basic thermodynamics and conservation principles. The different engine subsystems and engine phenomena discretized into eight stages are modeled in a "control-oriented sense" to address the combustion timing, peak pressure and heat release rate control issues. The model has been implemented in MATLAB® to facilitate simulation studies and requires minimum tuning parameters to be experimentally recognized. Model validation is based on three sets of engine data, obtained from literature. The validation suggests that the model, once tuned properly, shows a fair agreement between the simulation and experimental data for a given engine and operating conditions.
Author: Parag Mehresh
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ISBN:
Category :
Languages : en
Pages : 306
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