Browsing by Author "Cheng, Qiang"
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Item Cycle-to-cycle variations of dual-fuel combustion in an optically accessible engine(ELSEVIER SCI LTD, 2019-08-02) Cheng, Qiang; Ahmad, Zeeshan; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionCyclic variations constitute an inherent consequence of the flow, thermal and concentration field variations between cycles. They are understood to lead to lower efficiency and higher emissions. The current investigation aims to evaluate the cycle-to-cycle variations (CCVs) based on 2D visualization and cylinder pressure in an optically accessible heavy-duty engine fueled with methane (main fuel) and diesel (pilot fuel). A high-speed color camera is employed to measure the combustion behavior based on natural luminosity (NL). Proper orthogonal decomposition (POD) is applied to reconstruct and analyze the images. The POD-based coefficient of variation (COV) is implemented to evaluate the cyclic variability, along with the pressure-based and global intensity-based COV. This coefficient is then adopted to discriminate the coherent and incoherent parts from the fluctuations in the luminosity field. The POD-based and global intensity-based COV presents the variations in the luminosity field, which can provide information on chemical kinetics, while pressure-based COV provides a general description of the cyclic fluctuation of thermodynamics. To extract more information from the NL images, the color-intensity COV analysis based on the intensity separated from RGB channels is adopted to estimate the CCVs from the aspect of spectral emissions (excited and ionized radicals in the flame). Finally, the effects of methane lambda, pilot fuel rate and charge air temperature on the CCVs were analyzed systematically. The results revealed that richer methane conditions has an inhibitive effect on the CCVs. The appearance of the CCVs were determined by the ignition characteristics of the pilot fuel. A critical point was found in charge air temperature, when the charge air temperature lower than the critical point, the increase of the charge air temperature has a promotive effect on the CCVs; after that, it has an inhibitive effect on the CCVs.Item DEEP RECURRENT NEURAL NETWORK ALGORITHM FOR ACTIVE SOUND QUALITY CONTROL OF WIPER-WINDSHIELD FRICTION NOISE(2024) Guo, Hui; Fan, Huizhi; Wang, Yansong; Ma, Minghui; Huang, Shuang; Liu, Ningning; Cheng, Qiang; Department of Mechanical Engineering; van Keulen, Wim; Kok, Jim; Energy Conversion and Systems; Shanghai University of Engineering ScienceThe effectiveness of traditional Adaptive Noise Equalizer (ANE) algorithm and its extension algorithms for Active Sound Quality Control (ASQC) systems is unsatisfied in engineering application, especially for the nonlinear problems. In this paper, a nonlinear active sound quality control algorithm based on Deep Recurrent Neural Network (DRNN) is proposed for the wiper-windshield friction noise. A DRNN model based on Long Short-Term Memory (LSTM) neutral network is constructed to perform nonlinear mapping on the input signal through setting an objective function. The trained output secondary signal is counteracted with the expected signal to obtain the minimum error signal. Thus, the linear filter in traditional algorithms is replaced by the proposed DRNN model. Setting the wiper-windshield friction noise of an actual vehicles as the input signal for the DRNN algorithm, simulation analysis was conducted. The results were compared with the input original signal in terms of control effectiveness in both time-domain and frequency-domain. Meanwhile, the psychoacoustic attribute metrics such as loudness, roughness, and sharpness are calculated for the simulating output signals. The results demonstrate that the proposed DRNN active sound quality control algorithm has a good control effect on the wiper-windshield friction noise, especially for the frequency range of 0-500Hz, which is 67.39%, 62.58%, and 56.38% lower than the original noise in terms of loudness, roughness, and sharpness, respectively. The amplitude of the noise is simultaneously reduced. Therefore, the proposed algorithm has significant advantages in improving the vehicle interior sound quality by controlling the wiper-windshield friction noise.Item Dynamics of the Ammonia Spray Using High-Speed Schlieren Imaging(SAE International, 2022-03-08) Cheng, Qiang; Ojanen, Katriina; Diao, Yantao; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion; Energy Authority; Shandong Heze Huaxing Fuel Injection Equipment Co. Ltd.Ammonia (NH3), as a carbon-free fuel, has a higher optimization potential to power internal combustion engines (ICEs) compared to hydrogen due to its relatively high energy density (7.1MJ/L), with an established transportation network and high flexibility. However, the NH3 is still far underdeveloped as fuel for ICE application because of its completely different chemical and physical properties compared with hydrocarbon fuels. Among all uncertainties, the dynamics of the NH3 spray at engine conditions is one of the most important factors that should be clarified for optimizing the fuel-air mixing. To characterize the evolution and evaporation process of NH3 spray, a high-speed Z-type schlieren imaging technique is employed to estimate the spray characteristics under different injection pressure and air densities in a constant volume chamber. Three renewable fuels, including NH3, methanol and ethanol, are investigated to compare the differences in their spray behavior at engine-like conditions. The basic parameters of the spray geometry such as spray penetration, spray cone angle and cross-section area are quantified based on the schlieren images postprocessing. The results show that the spray geometry of NH3 differs from that of the other fuels, which exhibits a longer penetration, larger spray cone angle and cross-section area. Moreover, the NH3 also shows a faster evaporation rate than methanol and ethanol. To extract more information from the spray images, an optical flow algorithm is derived to visualize the velocity field based on the schlieren images. The results indicate that NH3 spray is driven to the spray axis under the effect of the vortices. The vortices are induced by the entrainment of the surrounding gas and act as the driving forces that push the spray plumes towards the axis at the same time. The two vortices of NH3 grow much bigger and stronger and move closer to the spray axis compared to the ethanol and methanol.Item Effect of Hydrogen Enhancement on Natural Flame Luminosity of Tri-Fuel Combustion in an Optical Engine(MDPI AG, 2022-12) Cheng, Qiang; Ahmad, Zeeshan; Kaario, Ossi; Vuorinen, Ville; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionA novel combustion mode, namely tri-fuel (TF) combustion using a diesel pilot to ignite the premixed methane–hydrogen–air (CH4–H2–air) mixtures, was experimentally investigated under various H2 fractions (0%, 10%, 20%, 40%, 60%) and ultra-lean conditions (equivalence ratio of (Formula presented.) 0.5). The overarching objective is to evaluate the effect of H2 fraction on flame characteristics and engine performance. To visualize the effect of H2 fraction on the combustion process and flame characteristics, a high-speed color camera (Photron SA-Z) was employed for natural flame luminosity (NFL) imaging to visualize the instantaneous TF combustion process. The engine performance, flame characteristics, and flame stability are characterized based on cylinder pressure and color natural flame images. Both pressure-based and optical imaging-based analyses indicate that adding H2 into the CH4–air mixture can dramatically improve engine performance, such as combustion efficiency, flame speed, and flame stability. The visualization results of NFL show that the addition of H2 promotes the high-temperature reaction, which exhibits a brighter bluish flame during the start of combustion and main combustion, however, a brighter orangish flame during the end of combustion. Since the combustion is ultra-lean, increasing the H2 concentration in the CH4–air mixture dramatically improves the flame propagation, which might reduce the CH4 slip. However, higher H2 concentration in the CH4–air mixture might lead to a high-temperature reaction that sequentially promotes soot emissions, which emit a bright yellowish flame.Item Effect of pilot fuel properties on engine performance and combustion stability in a tri-fuel engine powered by premixed methane-hydrogen and diesel pilot(PERGAMON-ELSEVIER SCIENCE LTD, 2021-10-29) Cheng, Qiang; Kaario, Ossi; Ahmad, Zeeshan; Vuorinen, Ville; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionThe present work investigates the effect of pilot fuel properties on TF combustion using premixed methane-hydrogen-air (CH4-H2-air) mixtures ignited by a small amount of diesel pilot. Especially, we are investigating the effect of the cetane number (CN) and aromatic content (AC) on TF combustion in a single-cylinder compression ignition (CI) engine at varying charge air temperatures (Tair = 25 °C, 40 °C, 55 °C) and H2 volume fractions (MH2 = 10%, 20%, 40% and 60%) at lean premixed charge mixture conditions (equivalence ratio φ = 0.5). The novelty and main findings of the work consist of the following features: 1) besides the effect of H2 concentration and charge-air temperature, pilot fuel properties also play a crucial role in TF combustion, even a small amount of diesel pilot could dramatically affect the engine performance and combustion stability, 2) the CN and AC are the key factors affect the ignition delay time (IDT) and indicated thermal efficiency (ITE), 3) the in-cylinder pressure oscillation analysis based on a novel Superlets (SL) approach indicates that pilot fuel properties are important to the combustion states and combustion stability.Item Experimental and Numerical Investigation of Hydrogen Jet-Wall Impingement(SAE International, 2022-08-30) Yeganeh, Maria; Rabensteiner, Samuel; Cheng, Qiang; Ranta, Olli; Karimkashi Arani, Shervin; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion; Energy Conversion; Department of Mechanical EngineeringDecarbonization of the automotive industry is one of the major challenges in the transportation sector, according to the recently proposed climate neutrality policies, e.g., the EU 'Fit for 55' package. Hydrogen as a carbon-free energy career is a promising alternative fuel to reduce greenhouse gas emissions. The main objective of the present study is to investigate non-reactive hydrogen jet impingement on a piston bowl profile at different injection angles and under the effect of various pressure ratios (PR), where PR is the relative ratio of injection pressure (IP) to chamber pressure (CP). This study helps to gain further insight into the mixture formation in a heavy-duty hydrogen engine, which is critical in predicting combustion efficiency. In the experimental campaign, a typical high-speed z-type Schlieren method is applied for visualizing the jet from the lateral windows of a constant volume chamber, and two custom codes are developed for post-processing the results. In particular, the jet's major characteristics i.e., penetration, width, and cross-sectional area are calculated at different PRs (25, 10, 5, and 2.5). The results show that higher pressure ratios lead to faster penetration and larger cross-sectional areas of the hydrogen jet. In addition, the jet-piston interaction at different angles as well as the flow around the piston towards the liner and back to the main cylinder volume are studied considering the optimization of mixture formation in the cylinder. By changing the injection angle (10°, 15°, and 20°), jet-piston impingement occurs near the edges, which results in greater hydrogen concentration around those areas, adversely affecting mixture formation. The measurements are further used to validate a numerical model for hydrogen injection and mixing in a similar jet-piston geometry, applying an unsteady Reynolds-averaged Navier-Stokes simulation approach in the commercial software Star-CCM+.Item Experimental and Numerical Study of a Low-Pressure Hydrogen Jet under the Effect of Nozzle Geometry and Pressure Ratio(SAE International, 2023-04-11) Yeganeh, Maryam; Rabensteiner, Samuel; Karimkashi, Shervin; Cheng, Qiang; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion and Systems; Energy Conversion and SystemsHydrogen (H2), a potential carbon-neutral fuel, has attracted considerable attention in the automotive industry for transition toward zero-emission. Since the H2 jet dynamics play a significant role in the fuel/air mixing process of direct injection spark ignition (DISI) engines, the current study focuses on experimental and numerical investigation of a low-pressure H2 jet to assess its mixing behavior. In the experimental campaign, high-speed z-type schlieren imaging is applied in a constant volume chamber and H2 jet characteristics (penetration and cross-sectional area) are calculated by MATLAB and Python-based image post-processing. In addition, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach is used in the commercial software Star-CCM+ for numerical simulations. The H2 jet dynamics is investigated under the effect of nozzle geometry (single-hole, double-hole, and multiple-hole (5-hole)), which constitutes the novelty of the present research, and pressure ratio (PR = injection pressure (Pi) / chamber pressure (Pch)). The results show that the H2 jet from the single-hole nozzle possesses the fastest penetration and smallest cross-sectional area. On the contrary, the H2 jet from the double-hole nozzle possesses the slowest penetration and largest cross-sectional area. The H2 jet from the multiple-hole nozzle shows characteristics between those of the single-hole and double-hole. Overall, since higher pressure ratio and larger jet cross-sectional area lead to higher uniformity of the fuel/air mixture, high-pressure injection with the double-hole nozzle seems more advantageous to attain efficient mixing.Item Experimental dataset of U-folded falling chain under various openings with high-speed imaging(Elsevier, 2023-02) Markou, Athanasios A.; Baroudi, Djebar; Cheng, Qiang; Bordbar, Hadi; Department of Civil Engineering; Department of Mechanical Engineering; Structures – Structural Engineering, Mechanics and Computation; Energy Conversion and Systems; Performance in Building Design and ConstructionA folded chain hanged by its two ends in U-shape at the same level with an opening, distance, between its two tips is known as U-folded chain, as studied in Markou et al. (2023). When one of the tips is fixed and the other one is released, the free tip of the U-folded falling chain accelerates faster than gravity, due to momentum conservation. This counterintuitive fact has long excited mechanicians around the globe. In the current paper we present a group of datasets (tip's coordinate timeseries), comprising three different subsets of this variable-mass dynamical system. A series of experiments of a U-folded falling chain of length 1.51m with total mass 31 gm, have been recorded with a high-speed imaging (2000 fps) (Markou et al., 2023). The distance between the tips of the chain (opening) varies throughout the experimental session series: (i) 0.045m, (ii) 0.087m and (iii) 0.128m. Three timeseries of the tip's coordinates (x,y) have been extracted using an edge detector based method, from the recorded high-speed videos.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )Item An experimental investigation of a hydrogen jet behavior(2020-10-19) Laitinen, Tapio; Cheng, Qiang; Insinööritieteiden korkeakoulu; Larmi, MarttiPrevention of climate change is one of the biggest challenges of modern society, and there are requirements for new and sustainable options for fossil fuels, especially at the transport sector. Hydrogen internal combustion engine (H-ICE) is a technology, which gets rid of the tailpipe emissions of carbon dioxide (CO2) and reduces life cycle emissions of it. H-ICE and direct injection (DI) were selected to be analyzed because they are mature technologies and have existing infrastructures. Utilizing DI, the combustion of hydrogen can be enhanced, power density increased, and emissions of nitrogen oxides (NOx) reduced. In the experimental part of this thesis, helium was used instead of hydrogen due to safety reasons. Helium was injected into quiescent nitrogen with variable injection and chamber pressures and pressure ratios. The high-speed Schlieren imaging technique was applied to record the jet development process. It is an optical and nonintrusive method where transparent gases can be imaged utilizing their density difference, which is caused by pressure, temperature, or composition gradients, for instance. It was selected because it does not interrupt the jet development process. A high-pressure piezoelectric injector generally used in gasoline engine was selected for the helium injections. It was found out that it is capable of injecting gas up to 100 bar and up to 98 pressure ratio without discernible leakages. Increasing the pressure ratio increased the jet penetration, width, and area, but with constant pressure ratio lowering the injection pressure had a similar effect. When the pressure ratio was over 80, the jet progress retarded. It was assumed to occur due to a drop in the injection pressure during the injection. Furthermore, a horizontally positioned injector produced upwards tilted jets, and thus in the future works, the injector should be vertically installed.Item An experimental investigation of a hydrogen, methane and helium gas jet behavior using single hole and hollow cone piezoelectric injector(2021-06-14) Dharamsi, Aishwarya; Cheng, Qiang; Insinööritieteiden korkeakoulu; Larmi, MarttiThere is now an increasing need for using alternative fuels especially in the transportation sector, which are more environmentally friendly fuels due to a decrease in fossil fuels and also more importantly a rapid increase in global warming. Use of Hydrogen in Hydrogen internal combustion engine either as a dual fuel option along with diesel or even better, as a sole fuel, is much better for the environment considering the emissions and their impact on the environment. But to shift from present infrastructure to a completely clean and green hydrogen economy might take many years, resources, and finance. The use of Hydrogen as a dual fuel option would provide a bridge towards the hydrogen economy. Also, the use of methane is seen as one of the potential options to get closer to the full hydrogen economy. Direct injection (DI) is a well-established technology and the combustion of hydrogen has a possibility of further being studied in a similar way as that of diesel. Further research on optimizing DI engines using Hydrogen has the potential of achieving higher efficiency and reduced nitrogen oxides (NOx) emissions. Jets of Helium, Hydrogen, and Methane are studied in the experimental part of this thesis. These gas jets were injected into quiescent nitrogen with variable injection and chamber pressures and pressure ratios. Helium and Hydrogen have similar jet characteristics but their variations are confirmed through experimental analysis if any. Data between methane and hydrogen jets are compared in this thesis. To study these invisible, high-speed gas jets, a high-speed schlieren imaging technique was used to analyze the geometrical properties of the jets. The images obtained were post-processed to acquire geometrical attributes of jets such as penetration, width and area. Also, two different types of injectors i.e., single hole injector and hollow cone injector were used for all these jets and their results were compared and analyzed. A hollow cone injector like the one used in this thesis is already being used for gasoline engines. These injectors are capable of injecting gases up to 100 bar. The jet characteristics were also studied for different voltages for the hollow cone injector. The results showed that the jet penetration was more for the single hole injector as compared to the hollow cone injector for the same conditions. Also, it was found that with increasing pressure ratio, penetration was more for both the injectors but the area for single hole injector got reduced over time faster compared to the hollow cone injector due to quicker dispersion of gas for single hole injector. Also, it was found that increased needle lift has a higher penetration length due to higher injection pressure.Item Experimental investigation of methane/hydrogen dual-fuel combustion in a spark-ignition optical engine(2024-08-19) Kapp, Joakim; Cheng, Qiang; Insinööritieteiden korkeakoulu; Kaario, OssiLow-carbon alternative fuels are considered a viable option for reducing the emissions caused by transport sector, while also answering the ever-growing need for energy in the sector. Hydrogen is widely regarded as the most interesting alternative fuel due to its carbon free combustion. However, not all fundamental phenomena related to the combustion process of alternative fuels in an ICE are known. Optical engines play a key role in alternative fuel research, as they can be used to visualize the combustion. In this work, the optical research engine in Aalto University’s ICE lab was upgraded to provide a wider view into the combustion chamber through a quartz piston. The updated optical assembly was designed in a previous thesis. The update enables the engine to use hydrogen direct injection and makes the overall engine design more modular. In addition, methane and hydrogen blends and pure hydrogen combustion was analysed by utilizing highspeed optical imaging methods. Despite some difficulties, the mechanical update was successful, and the engine design was proven to be working by continuing tests with different blends of hydrogen and methane. In the future the updated optical engine will be used for further alternative fuel studies. The optical research conducted in this work laid ground for future studies.Item Experimental investigations of hydrogen pre-ignition phenomenon induced by two different lubricating oils in a rapid compression expansion machine(Elsevier Ltd, 2024-01) Yeganeh, Maryam; Rönn, Kristian; Karimkashi, Shervin; Cheng, Qiang; Hlaing, Ponnya; Hyvönen, Jari; Vuorinen, Ville; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion and Systems; Department of Mechanical Engineering; Wärtsilä CorporationThe growing interest in utilizing hydrogen (H2) as a zero-carbon fuel has ignited extensive research on its potential application within internal combustion engines (ICEs). However, a major challenge regarding H2 ICEs is the pre-ignition phenomenon. Various factors, including hot spots, oil droplets/deposits, and the ignition system, contribute to pre-ignition. This study focuses on pre-ignition caused by engine lubricating oil droplets/deposits. A Rapid Compression Expansion Machine (RCEM), equipped with optical access is employed to conduct a comparative analysis of the pre-ignition characteristics of two distinct engine lubricating oils called oil A and oil B. Oil A is an API (American Petroleum Institute) Group II lubricating oil with Ca (calcium) detergents, while oil B is of API Group V with a combination of Mg (magnesium) and Ca (calcium) components. The study identifies pre-ignition limits for both oils across various air-to-fuel ratios (λ = 2, 2.5, 3) and compression ratios (ɛ = 11-14.5). Comparative assessments are also performed through a chemical analysis (homogenous constant volume ignition delay time (IDT) simulations) as well as investigating the cylinder pressure and heat release rate (HRR) curves for the tested lubricating oils. This study represents the first exploration of the H2 pre-ignition phenomenon in response to different engine lubricating oils within the context of an RCEM. The findings reveal that oil A is more susceptible to pre-ignition. In contrast, oil B exhibits pre-ignition at higher ɛ while maintaining constant λ. Simultaneously, oil B displays an accelerated flame propagation and more robust combustion due to the incidence of pre-ignition at higher ɛ. Hence, in the context of H2 ICEs, the Group V oil sample (oil B) presents itself as a more advantageous choice compared to the Group II oil sample (oil A) for alleviating undesirable pre-ignition.Item Experimental study of hydrogen jet dynamics : Investigating free momentum and impingement phenomena(Elsevier Ltd, 2024-05-28) Yeganeh, Maryam; Akram, Muhammad Saad; Cheng, Qiang; Karimkashi, Shervin; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion and Systems; Department of Mechanical EngineeringThere is a growing interest in the utilization of hydrogen (H2), as a zero-carbon fuel, in internal combustion engines (ICEs). Accordingly, the primary focus of this study is to investigate low-pressure H2 jet dynamics, which play a vital role in air-fuel mixing especially in direct injection (DI) engines. High-speed z-type schlieren imaging is employed in a constant volume chamber to study the effect of nozzle geometry (single-hole, double-hole, and multi-hole), pressure ratios (PR = injection pressure (Pi)/chamber pressure (Pch)), injection angle (10°, 15°, and 20°), and injection duration (ID) on the H2 jet characteristics. Image post-processing is executed in MATLAB and Python to extract the H2 jet characteristics, including penetration and cross-sectional area. The novelty stems from the comprehensive investigation of H2 jet dynamics and impingement phenomenon under various engine-like conditions. The results indicate that apart from the fact that higher pressure ratios (PRs) improve the air-fuel mixing, the single-hole nozzle induces the fastest H2 jet penetration and the smallest cross-sectional area. Conversely, the double-hole nozzle leads to the slowest penetration and the most expansive cross-sectional area. The performance of the multi-hole nozzle falls between that of the single-hole and double-hole nozzles. Additionally, changing the injection angle results in jet-piston impingement at the periphery, leading to higher H2 concentration in those areas. This negatively affects the formation of an optimal air-fuel mixture. It is also found that changing the injection duration (ID) has no noticeable impact on the H2 jet's behavior.Item Experimental study on tri-fuel combustion using premixed methane-hydrogen mixtures ignited by a diesel pilot(PERGAMON-ELSEVIER SCIENCE LTD, 2021-06-11) Cheng, Qiang; Ahmad, Zeeshan; Kaario, Ossi; Vuorinen, Ville; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionA comprehensive investigation on diesel pilot spray ignited methane-hydrogen (CH4–H2) combustion, tri-fuel combustion (TF), is performed in a single-cylinder compression ignition (CI) engine. The experiments provide a detailed analysis of the effect of H2 concentration (based on mole fraction, MH2) and charge-air temperature (Tair) on the ignition behavior, combustion stability, cycle-to-cycle (CCV) and engine performance. The results indicate that adding H2 from 0 to 60% shortens the ignition delay time (IDT) and combustion duration (based on CA90) up to 33% and 45%, respectively. Thereby, H2 helps to increase the indicated thermal efficiency (ITE) by as much as 10%. Furthermore, to gain an insight into the combustion stability and CCV, the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) methodologies are applied to estimate the combustion stability and CCV of the TF combustion process. The results reveal that the pressure oscillation can be reduced up to 4 dB/Hz and the CCV by 50% when MH2 < 60% and Tair < 55 °C. However, when MH2 > 60% and Tair > 40 °C, abnormal combustion and knocking are observed.Item Flame propagation of hydrogen combustion(2022-08-22) Schurr, Jennifer; Kaario, Ossi; Cheng, Qiang; Insinööritieteiden korkeakoulu; Larmi, MarttiIn recent years the urge to make future fuels market ready and understand their potentials and risks has become considerably higher. Hydrogen as one of a limited number of zero emission fuels is getting more interesting in terms of supporting the energy transition. This Master Thesis helps to understand hydrogen’s combustion behaviour and flame propagation and if hydrogen has a future in the transportation industry. The thesis is conducted beginning with a literature study of previous laminar flame speed measurements, continues with 1D flame simulations in Cantera and finishes with optical flame speed measurements (Z-Schlieren) in a constant volume chamber. The flame propagation, the flame speed and its influencing factors, temperature, pressure and dilution, have been examined. The results obtained by the simulations and experimental work have been validated, analysed and compared to literature. It could be displayed that the simulations and experiments vary since turbulences and uncertainties are affecting the accuracy of the system. In conclusion it shows that hydrogen has a high potential as future fuel but it is also to mention that future studies are required to give a fully educated statement.Item HVO, RME and diesel fuel combustion in an optically accessible compression ignition engine(American Chemical Society, 2019-03-21) Cheng, Qiang; Hulkkonen, Tuomo; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionThe current paper investigates the spray and combustion characteristics of hydrotreated vegetable oil (HVO), petrol diesel (EN590), blends of HVO with petrol diesel (70% EN590 and 30% HVO), and rapeseed oil methyl esters (RME) in an optically accessible compression ignition engine. Mie scattering and natural luminosity imaging are employed to measure the liquid spray and combustion behaviors. The spray and combustion processes are divided into four stages based on optical imaging. The morphology and quantitative analysis based on imaging provides a method for visualizing the in-cylinder spray and combustion behavior with four test fuels. The ignition delay and combustion characteristics detected from optical measurements are compared to those determined from cylinder pressure. The results show that the ignition delay of HVO and RME occurs earlier and the flame propagation at the premixed combustion stage proceeds faster compared to EN590 and HVO30. The spray and combustion characteristics of HVO30 are similar to EN590. However, ignition occurs earlier for HVO30 due to the higher CN. Comparison of the HVO and RME shows that there is a marginal difference in the ignition delay for these two fuels. However, the combustion duration of RME is shorter than that of HVO.Item Hyperspectral image reconstruction from colored natural flame luminosity imaging in a tri-fuel optical engine(Nature Publishing Group, 2023-12) Cheng, Qiang; Karimkashi, Shervin; Ahmad, Zeeshan; Kaario, Ossi; Vuorinen, Ville; Larmi, Martti; Department of Mechanical Engineering; Energy Conversion and SystemsThe detection of chemiluminescence from various radicals and molecules in a hydrocarbon flame can provide valuable information on the rate of local heat release, combustion stability, and combustion completeness. In this study, chemiluminescence from the combustion process is detected using a high-speed color camera within the broadband spectrum of visible light. Whereon, a novel hyperspectral reconstruction approach based on the physically plausible spectral reconstruction (PPSR) is employed to reconstruct the spectral chemiluminescence signals from 400 to 700 nm with a resolution of 10 nm to provide 31 different spectral channels. The reconstructed key chemiluminescence signals (e.g., CH*, CH2O*, C2*, and CO2*) from the color images are further analyzed to characterize the chemical kinetics and combustion processes under engine conditions. The spectral chemiluminescence evolution with engine crank angle is identified to comprehend the effect of H2 fraction on flame characteristics and combustion kinetics. Additionally, in this study, a detailed kinetic mechanism is adopted to deepen the theoretical understanding and describe the spectral chemiluminescence from H2/CH4 and H2/CH4/n-dodecane flames at relevant conditions for various species including OH*, CH*, C2*, and CO2*. The results indicate that the PPSR is an adequately reliable approach to reconstructing spectral wavelengths based on chemiluminescence signals from the color images, which can potentially provide qualitative information about the evolution of various species during combustion. Here, the reconstructed chemiluminescence images show less than 1% errors compared to the raw images in red, green, and blue channels. Furthermore, the reconstructed chemiluminescence trends of CH*, CH2O*, C2*, and CO2* show a good agreement with the detailed kinetics 0D simulation.Item Optical engine design and optical imaging techniques in combustion engine research(2023-05-15) Nissinen, Joel; Cheng, Qiang; Insinööritieteiden korkeakoulu; Kaario, OssiNew alternative carbon neutral fuels can be a key part of the solution to reduce greenhouse gas emissions in transportation and power plants to meet set goals of carbon neutrality by 2035 in Finland and “fit for 55” aspirations in EU for reduced GHG emissions by 2030. As such hydrogen is of major interest as a fuel for internal combustion engines, and also so at the combustion engine laboratory at Department of Mechanical Engineering Energy Conversion and Systems group at Aalto university at the moment. However, hydrogen combustion still requires much more research to understand better the phenomenon involved and to visualize, analyse and measure these phenomena in combustion engine. Optical engines provide excellent platform for this with many different optical imaging techniques. However, the current optical engine construction at Aalto limits the imaging techniques applicable and injection strategies are limited to port-fuel injection (PFI) for hydrogen studies. Therefore, in this thesis work the author has designed a new optical engine set-up to start studies on direct injection hydrogen combustion and also improved the optical access of the optical engine in a way that more imaging techniques are applicable for future at Aalto. The design is also partly manufactured and will be assembled in the near future. In the first chapter of the thesis a literature review of some of the most important imaging techniques available for optical engine combustion research and differences of the optical engine to full metal engines are highlighted. The second chapter acts as an introduction to the current optical engine and some of the previous studies done and problems with the current construction are highlighted and discussed. The third chapter introduces the main thesis workload of designing and manufacturing of the new improved optical engine set-up for future use at Aalto. Then at the end summary of the thesis and short discussion of the design validation is included.Item Roadmap on electromagnetic metamaterials and metasurfaces(Institute of Physics Publishing, 2024-07) Cui, Tie Jun; Zhang, Shuang; Alù, Andrea; Wegener, Martin; Pendry, Sir John; Luo, Jie; Lai, Yun; Wang, Zuojia; Lin, Xiao; Chen, Hongsheng; Chen, Ping; Wu, Rui Xin; Yin, Yuhang; Zhao, Pengfei; Chen, Huanyang; Li, Yue; Zhou, Ziheng; Engheta, Nader; Asadchy, Viktar; Simovski, Constantin; Tretyakov, Sergei; Yang, Biao; Campbell, Sawyer D.; Hao, Yang; Werner, Douglas H.; Sun, Shulin; Zhou, Lei; Xu, Su; Sun, Hong Bo; Zhou, Zhou; Li, Zile; Zheng, Guoxing; Chen, Xianzhong; Li, Tao; Zhu, Shining; Zhou, Junxiao; Zhao, Junxiang; Liu, Zhaowei; Zhang, Yuchao; Zhang, Qiming; Gu, Min; Xiao, Shumin; Liu, Yongmin; Zhang, Xianzhe; Tang, Yutao; Li, Guixin; Zentgraf, Thomas; Koshelev, Kirill; Kivshar, Yuri; Li, Xin; Badloe, Trevon; Huang, Lingling; Rho, Junsuk; Wang, Shuming; Tsai, Din Ping; Bykov, A. Yu; Krasavin, A. V.; Zayats, A. V.; McDonnell, Cormac; Ellenbogen, Tal; Luo, Xiangang; Pu, Mingbo; Garcia-Vidal, Francisco J.; Liu, Liangliang; Li, Zhuo; Tang, Wenxuan; Ma, Hui Feng; Zhang, Jingjing; Luo, Yu; Zhang, Xuanru; Zhang, Hao Chi; He, Pei Hang; Zhang, Le Peng; Wan, Xiang; Wu, Haotian; Liu, Shuo; Jiang, Wei Xiang; Zhang, Xin Ge; Qiu, Cheng Wei; Ma, Qian; Liu, Che; Li, Long; Han, Jiaqi; Li, Lianlin; Cotrufo, Michele; Caloz, C.; Deck-Léger, Z. L.; Bahrami, A.; Céspedes, O.; Galiffi, E.; Huidobro, P. A.; Cheng, Qiang; Dai, Jun Yan; Ke, Jun Cheng; Zhang, Lei; Galdi, Vincenzo; di Renzo, Marco; Department of Electronics and Nanoengineering; Kostantin Simovski Group; Sergei Tretiakov Group; Southeast University, Nanjing; University of Hong Kong; City University of New York; Karlsruhe Institute of Technology; Imperial College London; Soochow University; Nanjing University; Zhejiang University; Xiamen University; Tsinghua University; University of Pennsylvania; National University of Defense Technology; Pennsylvania State University; Queen Mary University of London; Fudan University; Jilin University; Wuhan University; Heriot-Watt University; University of California; University of Shanghai for Science and Technology; Harbin Institute of Technology; Northeastern University; Southern University of Science and Technology; Paderborn University; Australian National University; Beijing Institute of Technology; Pohang University of Science and Technology; City University of Hong Kong; King's College London; Tel Aviv University; Chinese Academy of Sciences; Ramón y Cajal University Hospital; Nanjing University of Aeronautics and Astronautics; Nanyang Technological University; National University of Singapore; Xidian University; Peking University; KU Leuven; Universidade de Lisboa; University of Sannio; Université Paris-Saclay; Stanford UniversityItem Simultaneous Visualization of Natural Luminosity and Chemiluminescence of Dual Fuel Combustion in an Optically Accessible Engine(SAE International, 2020-04-14) Cheng, Qiang; Ahmad, Zeeshan; Kaario, Ossi; Larmi, Martti; Department of Mechanical Engineering; Energy ConversionThe engine fueled with methane/diesel is a promising and highly attractive operation mode due to its high performance-to-cost ratio and clean-burning qualities. However, the combustion process and chemical reactions in dual fuel combustion are highly complex, involving short transient pilot-fuel injection into the premixed gaseous fuel charge, autoignition, and combustion mode transition into premixed flame propagation. The motivation of the current investigation is to gain an insight into the combustion dynamics in dual fuel combustion engine based on chemical radicals and thermal radiation. The chemiluminescence (CL) and natural luminosity (NL) are expected to provide specific characteristics in combustion control and monitoring. To visualize the highly unsteady combustion process in terms of OH∗, CH2O∗ radicals and natural luminous emissions, the band pass filters with 308 nm, 330 nm combined with an image doubler are employed to visualize the OH∗ and CH2O∗ CL simultaneously. High speed natural luminosity imaging is adopted to illustrate the effects methane lambda and pilot ratio on the ignition delay, luminous intensity and engine performance. Spectroscopy analysis based on OH∗, CH2O∗ and NL was performed to study the chemical reactions in dual fuel mode.
