A New Method for Simultaneous Determination of the TDC Offset and the Pressure Offset in Fired Cylinders of an Internal Combustion Engine

An innovative computationally efficient method for the simultaneous determination of top dead centre (TDC) offset and pressure offset is presented. It is based on characteristic deviations of the rate of heat release (ROHR) that are specific for both offsets in compression phase and expansion phase after the end of combustion. These characteristic deviations of the ROHR are derived from first principles and they were also confirmed through manual shifts of the pressure trace. The ROHR is calculated based on the first law of thermodynamics using an in-cylinder pressure trace, engine geometrical parameters and operating point specific parameters. The method can be applied in off-line analyses using an averaged pressure trace or in on-line analyses using a single pressure trace. In both application areas the method simultaneously determines the TDC position and the pressure offset within a single processing of the pressure trace, whereas a second refinement step can be performed for obtaining more accurate results as correction factors are determined more accurately using nearly converged input data. Innovative analytic basis of the method allows for significant reduction of the computational times compared to the existing methods for the simultaneous determination of TDC offset and pressure offset in fired conditions. The method was validated on a heavy-duty and a light-duty diesel engine

Napredni procesi zgorevanja z uporabo inovativnih goriv, pridobljenih iz odpadkov

Numerical and experimental methodologies were developed in the dissertation with the goal of improving internal combustion engine control and decreasing engine-out exhaust emissions leading to mitigated impact on the environment. An innovative numerical method for simultaneous determination of the pressure and the top dead centre offset, which significantly reduces computational time compared to other methods, is presented in the numerical part of the dissertation. The experimental part of the dissertation comprises: - Development of a novel approach for the utilization of a pure tire pyrolysis oil (TPO) in a turbocharged and intercooled internal combustion engine without any hardware modifications with the introduction of the pilot injection. - Establishment of a partially premixed combustion (PPC) concept with a direct injection of diesel fuel, which also represents a benchmark for a novel fuel (TPO - a representative of low reactivity fuels) being assessed in the PPC. - Development of a methodology for the utilization of hydrotreated vegetable oil (HVO)/gasoline mixture in PPC. - Development of a methodology for establishing reactivity controlled compression ignition operation leading to a reduction of particulate matter and NOx emissions below EURO 6 levels without utilization of exhaust after-treatment systems at medium-load engine operation in a non-modified combustion chamber.V sklopu disertacije so bile razvite numerične in eksperimentalne metodologije s ciljem izboljšanja nadzora nad delovanjem motorja z notranjim zgorevanjem in znižanja izpustov onesnažil, kar vodi k zmanjšanju vpliva na okolje. V prvem delu disertacije je predstavljena inovativna numerična metoda za hkratno določitev absolutnega tlaka v valju in položaja zgornje mrtve lege bata, ki bistveno skrajša računske čase v primerjavi z ostalimi objavljenimi metodami. Eksperimentalni del disertacije obsega: - Razvoj inovativnega pristopa za uporabo 100% piroliznega olja iz odpadnih pnevmatik v prisilno polnjenem motorju s hladilnikom polnilnega zraka brez modifikacij strojnih komponent samo z uvedbo pilotnega vbrizga. - Vzpostavitev inovativnega zgorevalnega načina z delno homogenizirano delovno zmesjo (ang. Partially Premixed Combustion - PPC) z neposrednim vbrizgom dizelskega goriva, kar predstavlja osnovo za analizo primernosti uporabe piroliznega olja iz odpadnih pnevmatik v PPC načinu. - Razvoj metodologije za uporabo mešanice hidrogeniziranega rastlinskega olja in bencina v PPC načinu. - Razvoj metodologije za vzpostavitev inovativnega zgorevalnega koncepta s kompresijskim vžigom in krmiljenjem poteka zgorevanja na podlagi reaktivnosti delovne zmesi (ang. Reactivity Controlled Compression Ignition - RCCI), ki omogoča doseganje izpustov trdnih delcev in dušikovih oksidov pod mejnimi vrednostmi, določenimi s trenutno veljavnim emisijskim standardom EURO 6 brez uporabe sistemov za naknadno obdelavo izpušnih plinov

A new method for simultaneous determination of the TDC offset and the pressure offset in fired cylinders of an internal combustion engine

An innovative computationally efficient method for the simultaneous determination of top dead centre (TDC) offset and pressure offset is presented. It is based on characteristic deviations of the rate of heat release (ROHR) that are specific for both offsets in compression phase and expansion phase after the end of combustion. These characteristic deviations of the ROHR are derived from first principles and they were also confirmed through manual shifts of the pressure trace. The ROHR is calculated based on the first law of thermodynamics using an in-cylinder pressure trace, engine geometrical parameters and operating point specific parameters. The method can be applied in off-line analyses using an averaged pressure trace or in on-line analyses using a single pressure trace. In both application areas the method simultaneously determines the TDC position and the pressure offset within a single processing of the pressure trace, whereas a second refinement step can be performed for obtaining more accurate results as correction factors are determined more accurately using nearly converged input data. Innovative analytic basis of the method allows for significant reduction of the computational times compared to the existing methods for the simultaneous determination of TDC offset and pressure offset in fired conditions. The method was validated on a heavy-duty and a light-duty diesel engine

Real-time capable virtual NOx sensor for diesel engines based on a two-Zone thermodynamic model

This paper presents a control-oriented thermodynamic model capable of predicting nitrogen oxides (NOx) emissions in diesel engines. It is derived from zero-dimensional combustion model using in-cylinder pressure as the input. The methodology is based on a two-zone thermodynamic model which divides the combustion chamber into a burned and unburned gas zone. The original contribution of proposed method arises from: (1) application of a detailed two-zone modeling framework, developed in a way that the thermodynamic equations could be solved in a closed form without iterative procedure, which provides the basis for achieving high level of predictiveness, on the level of real-time capable models and (2) introduction of relative air-fuel ratio during combustion as a main and physically motivated calibration parameter of the NOx model. The model was calibrated and validated using data sets recorded in two different direct injection diesel engines, i.e. a light and a heavy-duty engine. The model is suitable for real-time applications since it takes less than a cycle to complete the entire closed cycle thermodynamic calculation including NOx prediction, which opens the possibility of integration in the engine control unit for closed-loop or feed-forward control

Methodology for processing pressure traces used as inputs for combustion analyses in diesel engines

This study proposes a novel methodology for designing an optimum equiripple finite impulse response (FIR) filter for processing in-cylinder pressure traces of a diesel internal combustion engine, which serve as inputs for high-precision combustion analyses. The proposed automated workflow is based on an innovative approach of determining the transition band frequencies and optimum filter order. The methodology is based on discrete Fourier transform analysis, which is the first step to estimate the location of the pass-band and stop-band frequencies. The second step uses short-time Fourier transform analysis to refine the estimated aforementioned frequencies. These pass-band and stop-band frequencies are further used to determine the most appropriate FIR filter order. The most widely used existing methods for estimating the FIR filter order are not effective in suppressing the oscillations in the rate-of-heat-release (ROHR) trace, thus hindering the accuracy of combustion analyses. To address this problem, an innovative method for determining the order of an FIR filter is proposed in this study. This method is based on the minimization of the integral of normalized signal-to-noise differences between the stop-band frequency and the Nyquist frequency. Developed filters were validated using spectral analysis and calculation of the ROHR. The validation results showed that the filters designed using the proposed innovative method were superior compared with those using the existing methods for all analyzed cases

Combustion and emission formation phenomena of tire pyrolysis oil in a common rail Diesel engine

A pure tire pyrolysis oil produced from waste tires was utilized in a modern 4-cylinder, turbocharged and intercooled, automotive Diesel engine. Due to its low cetane number, cetane improvers, external energy addition or increased compression ratios are generally required for its use in Diesel engines. Successful utilization of pure tire pyrolysis oil is also achievable with the addition of pilot injection but limited to mid- to high-load operating range. The first objective of the present study is therefore focused on further extension of the operating range towards lower loads by novel combined application of the exhaust gas recirculation and tailored main injection strategy. As the second objective, the article provides for the first time an in-depth analysis of the particulate emissions of the tire pyrolysis oil measured with two different methods. In this area it identifies and reasons challenges related to determination of the particulate emissions for alternative fuels. The original contribution of the presented approach thus arises from the holistic assessment of interactions between the exhaust gas recirculation ratios, injection parameters and combustion as well as gaseous and particulate emissions formation phenomena

Real-time capable virtual NOx sensor for diesel engines based on a two-zone thermodynamic model

International audienceThis paper presents a control-oriented thermodynamic model capable of predicting nitrogen oxides (NOx) emissions in diesel engines. It is derived from zero-dimensional combustion model using in-cylinder pressure as the input. The methodology is based on a two-zone thermodynamic model which divides the combustion chamber into a burned and unburned gas zone. The original contribution of proposed method arises from: (1) application of a detailed two-zone modeling framework, developed in a way that the thermodynamic equations could be solved in a closed form without iterative procedure, which provides the basis for achieving high level of predictiveness, on the level of real-time capable models and (2) introduction of relative air-fuel ratio during combustion as a main and physically motivated calibration parameter of the NOx model. The model was calibrated and validated using data sets recorded in two different direct injection diesel engines, i.e. a light and a heavy-duty engine. The model is suitable for real-time applications since it takes less than a cycle to complete the entire closed cycle thermodynamic calculation including NOx prediction, which opens the possibility of integration in the engine control unit for closed-loop or feed-forward control

Simultaneous particulate matter and nitrogen oxide emission reduction through enhanced charge homogenization in diesel engines

In the presented study, low temperature combustion was established with a direct injection of diesel fuel being a representative of high reactivity fuels and tire pyrolysis oil being a representative of low reactivity fuels. Tire pyrolysis oil was tested as a potential waste derived fuel for low temperature combustion, as it features diesel-like physical properties and lower cetane number compared to diesel fuel. The goal of this study was determination of suitable injection strategies and exhaust gas recirculation rates to explore potentials of both fuels in reducing emissions in low temperature combustion modes. It was demonstrated that relatively small changes in the engine control strategy possess the potential to significantly improve nitrogen oxide/particulate matter trade-off with minor effect on engine efficiency. In addition, low temperature combustion was for the first time successfully demonstrated with tire pyrolysis oil fuel, however, it was shown that lower reactivity of the fuel is by itself not sufficient to improve nitrogen oxide/ soot trade-off compared to the diesel fuel as entire spectra of fuel properties play an important role in improving nitrogen oxide/soot trade-off. This study thus establishes relations between different engine control strategies, intake manifold pressure and exhaust gas recirculation rate on engine thermodynamic parameters and engine-out emissions while utilizing innovative waste derived fuel that have not yet been analysed in similar combustion concepts

Feasibility analysis of 100% tire pyrolysis oil in a common rail Diesel engine

Tire pyrolysis oil (TPO) represents a promising waste-derived fuel for Diesel engines with its main deficiency being lower cetane number compared to Diesel fuel. Until now, successful utilization of the TPO in Diesel engines was possible only by increasing its cetane number, increasing compression ratio of the engine or preheating intake air or operation. This study shows the foremost results of utilizing the pure TPO in a modern turbocharged and intercooled Diesel engine without any of the aforementioned aids, which significantly facilitates its use and boosts its conversion efficiency to mechanical work. This was achieved by the tailored injection strategy that includes pilot injection, which was previously not utilized in combination with the TPO. The study reveals that with additional tailoring of the pilot injection, further optimization of thermodynamic parameters can be achieved while operating the turbocharged and intercooled Diesel engine in a wide operating range under the use of pure TPO. Discovered phenomena are supported by interpretation of interactions between the injection parameters and combustion as well as emission formation phenomena of the pure TPO

Spatially selective dilution

To support the ongoing energy transition and minimize the environmental footprint of combustion related technologies, the paper presents a novel approach for combustion control in gas turbines and burners. It relies on spatially targeted injection of inert components in the spray core where existent concepts fail to deliver the desired dilution rate and are unable to fully govern the spatial distribution of heat release rates. Combustion process control is thus possible by actively adjusting the composition and mass flow of spatially selective introduction of inert species in the spray, optionally combined with classic, external exhaust gas recirculation, leading to an ultimate fuel-flexible concept which is capable of adjustments to heterogeneous fuels, their reactivity and physical properties. The proof of concept is demonstrated in a gas turbine combustion chamber first by investigating the isolated effects of spatially selective injection of inert species, its comparison to external exhaust gas recirculation and a combination of both. The results confirm the superiority of the approach as spatially selective mixture inertization is capable of 7% reduction of NO emissions with merely 3% increase of CO emissions and even 9% reduction of PM emissions. Furthermore, the concept proved transferrable together with all its benefits to combustion cycles with external exhaust gas recirculation. In this case, the 63% reduction of NO emissions with no observed CO penalty is possible. Simultaneous exploitation of spatially selective inertization, as well as external exhaust gas recirculation forms a fully controllable concept - spatially selective dilution control (SSDC), which enables extensive adjustability of dilution rates throughout the spray core and primary zone of combustion chamber. Compared to baseline case, such approach was proved to simultaneously reduce CO, NO and PM emissions normalized to fuel thermal power for 39%, 63% and 91%, respectively. The confirmation of applicability of the novel approach and its potential to influence the local conditions is opening a series of possible uses, either as an original design feature for future fuel-flexible systems or as a retrofit approach in existent combustion systems