Constant Compression Ratio Research Articles

Pressurizing the Fuel Cell in a Direct Hybrid System for Airborne Applications

The push towards achieving emission-free aviation is intensifying. The number of demonstrator aircraft like the HY4 form H2FLY or the ATR72 from Universal Hydrogen taking flight and gaining experience in electric aviation is increasing. One existing approach for the realization of an all-electric aircraft is a direct hybrid system comprising a fuel cell and a battery. During high-power phases of a mission, such as takeoff and climb, both the battery and the fuel cell contribute power. However, during cruise, power is solely supplied by the fuel cell to leverage the high energy density of hydrogen. In a direct hybrid system, the power share of the fuel cell and the battery is determined by the size and the operating conditions of both.The low ambient pressures at high altitude negatively affect the performance of fuel cells. This is not only important in fuel cell only propulsion systems but also when operating a direct hybrid system. The impact of low pressures on the behavior of a direct hybrid system, linking a fuel cell and a battery without a DC/DC converter, is demonstrated. The effects of a non-pressurized PEM-fuel cell in a direct hybrid with a lithium-ion battery in a low-pressure environment was analyzed previously (see attached figure).However, since weight and volume are crucial factors in an aircraft, the fuel cell reactants can be pressurized to increase the power density of the system. Pressurization improves the fuel cells performance and therefore reduces weight and volume of the system, but the pressurization of the ambient air to the desired inlet pressure of the fuel cell cathode requires energy. The pressurization of a fuel cell also changes its voltage power behavior, which in turn affects the operation of the direct hybrid system.In order to examine and analyze the influence of pressurization on the overall system performance, an open-source two-phase model of a fuel cell is used and compared to experimental measurement data to gain fuel cell data at different pressure levels.The behavior of the direct hybrid system at different operating conditions will be presented, where the net power of the pressurized PEM-fuel cell system is combined with a battery to form a direct hybrid system. At lower state of charge (SOC) levels, the share of the fuel cell increases due to the lower voltage level of the battery over all power levels. In a pressure-driven fuel cell system, we take advantage of the fact that the pressure of the reactants can be controlled. By adjusting the pressure, the power share of the fuel cell and battery can be actively controlled. Lower operating pressure results in a higher battery share, due to the lower fuel cell voltage. By increasing the pressure, the voltage level provided by the fuel cell increases and therefore the power share of the fuel cell also increases.In addition, a realistic flight mission is analyzed with a constant compression ratio for the fuel cell air supply resulting in variable operating pressures of the fuel cell during flight, due to the different environmental pressures. The performance of the pressurized fuel cell direct hybrid under those varying ambient conditions will be presented. Figure 1

Modeling and Energy Flow Calculation of Integrated Energy System Based on Partial Differential Equation Model

This paper discusses the modeling and energy flow calculation method of integrated energy system based on partial differential equation model. By constructing a model that integrates power, heat, and natural gas networks, we analyze in detail the process of energy transmission, conversion, and storage in the system. In the process of modeling, the influence of compressor in constant compression ratio, constant outlet pressure and constant natural gas flow is specially considered, and the accuracy of the model is verified by specific data. In terms of energy flow calculation methods, we compare the performance of the unified solution method and the decomposition solution method. Data analysis shows that the non-gradient descent iterative method, gradient descent iterative method and decomposition solution method show consistency in calculation accuracy, that is, the calculation results of the three methods are the same. However, in terms of computational efficiency, the gradient descent iterative method shows significant advantages. Specifically, under identical computing conditions, our analysis reveals that the gradient descent iterative method exhibits a convergence rate approximately 30% faster than the decomposition solution method, resulting in a notable reduction of around 25% in computational time. This pivotal observation serves as a solid foundation for selecting a more computationally efficient approach in practical applications. To further enhance the computational efficiency, we have delved into deriving the Jacobian matrix of the model and subsequently proposed an advanced gradient descent iterative calculation technique. Through the actual test, this method not only improves the calculation speed, but also ensures the stability and accuracy of the calculation. The research in this paper not only provides a strong theoretical support for the optimal operation of the integrated energy system, but also provides a valuable reference for future research in related fields. Through specific data analysis, we prove the effectiveness and practicability of the proposed method, laying a solid foundation for the sustainable development of integrated energy systems.

Experimental assessment of catalytic biofuel effect on performance and exhaust emission of diesel engine

The present experiment is to analyze the effect of blended biodiesel of chicken fat CF10 (10% chicken fat and 90% diesel), waste cooking oil WC10 (10% waste cooking oil and 90% diesel), and combined chicken fat with waste cooking oil CF&WC10 (5% chicken fat + 5% waste cooking oil and 90% diesel) on the performance of diesel engine. The experiment is conducted at a constant compression ratio of 17, mixing 50 ppm alumina alfa (Al2O3-α) catalyst nanoparticles in each blend. The performance of biodiesel is analyzed at 25%, 50%, 75%, and 100% load conditions and is compared with pure diesel. The results show that the brake torque (BT) and brake power of CF&WC10 were found to be 22.48 Nm and 3.58 kW at full load conditions. However, the indicated thermal efficiency and BTE of CF&WC10 are at full loading conditions of 52.45% and 26.78% respectively. Because the supply of A/F ratio is 18.81, at full load condition and also lowering the brake specific fuel consumption up to 0.32 kg/kWh. Therefore, optimization of both performance and exhaust emission of an engine depends on BTE and NOx as well as HC emissions. Hence, from the emissions reduction point of view, CF&WC10 has lower emissions while achieving brake thermal efficiency similar to diesel fuel. The novelty of research shows CF&WC10 leads to enhanced performance of diesel engine compared to pure diesel fuel.

Study on seismic performance of the CFST-framed aeolian sand concrete composite shear wall

This study examined the seismic performance of composite shear walls framed with concrete-filled steel tubes (CFST) utilizing aeolian sand concrete. Six specimens were designed and tested under low cyclic load with a constant axial compression ratio. The research aimed to analyze how the CFST frame affects the seismic behavior of shear walls made from aeolian sand concrete and understand the underlying influence mechanism. The results showed significant differences in failure modes between CFST-framed and conventional aeolian sand concrete shear walls, with the former exhibiting a lower degree of failure and instances of plastic hinge failure. The hysteretic curve of CFST-framed walls displayed noticeable pinching, indicating enhanced seismic energy dissipation capacity and ductility. The damage analysis model based on the energy damage principle was found to be suitable for conducting seismic damage analysis of these walls. A shear capacity model was also established to accurately depict the variation in bearing capacity under low cyclic loading, providing valuable insights for engineering applications.

Comparative analysis of the seismic performance of ECC jacket reinforced columns with different cross-sectional forms subject to different load modes

Based on the high tensile strength and tensile strain of (engineered cementitious composites) ECC, it is applied to the weak link central columns of subway stations to enhance their seismic resilience. In this study, the effects of the column's cross-sectional shape, ECC jacket form, and the vertical gravity load and vertical dynamic load during seismic action on the hysteretic performance of the column were thoroughly analyzed. A constrained constitutive model for cementitious materials, a reinforced hysteresis constitute model, and a calculated damage factor for concrete were adopted to establish a three-dimensional refined column model with an experimentally verified error of less than 10 %. After that, the damage distribution and damage degree of the columns, as well as the changes in hysteretic performance such as hysteretic curve, skeleton curve, energy dissipation, and stiffness degradation were analyzed by the static model analysis. The results showed that the columns had higher damage levels under high frequency and high amplitude of dynamic axial compression ratio in the vertical direction compared to the constant high axial compression ratio, and the ECC jacket could effectively reduce the damage levels of the columns, but the use of the in-built ECC (IB-ECC) jacket was better than the out-sourced ECC (OS-ECC) jacket. In addition, the IB-ECC jacket did not significantly improve the peak bearing capacity of the columns, but significantly improved the ultimate bearing capacity and displacement ductility of the columns, while the OS-ECC jacket significantly improved the peak bearing capacity of the columns. The ECC jacket was also effective in slowing down the stiffness degradation of the columns. This study significantly contributes to the design strategies for enhancing the resilience of columns in subway stations.

Experimental Analysis of Gasoline-Ethanol-Methanol Blend at Various Conditions in Engine

Renewable resources are minimal throughout the world and considerable research work has been carried out to develop fossil-based options. Aim of the research work is to evaluate performance and engine exhaust emissions of varying blends at different conditions in engine. The experiments are conducted to analyze the performance of three distinct gasoline-alcohol fuel mixtures EM25 (10 percent ethanol-15 percent methanol-75 percent gasoline) in a computerized 1-cylinder, 4-stroke, VCR SI engine. The additional tests are conducted using regular gasoline fuel to compare performance and engine exhaust emissions. The engine performance using mixed fuel of ethanol-methanol-gasoline (GEM) has been evaluated under the various operating conditions in the range of 1200 to 1800 rpm, Spark Timings (ST’s) 100, Air Fuel Ratio 0.9 at constant Compression Ratio (CR) 10:1. When the vehicles operated with ethanol-methanol- gasoline mixtures then it has found that there is the reduction in HC, CO2, CO exhaust gases contents while 14% increments in NOx emission as compared with regular gasoline fuel. It is also observed that the brake power/brake torque is decreased when operated on ethanol-methanol-gasoline fuels as compared to pure gasoline. However, it has been revealed that BSFC is enhanced in comparison to regular gasoline.

Bambusa tulda: A potential feedstock for bioethanol and its blending effects on the performance of spark ignition engine

Alternatives to conventional fuel sources must be investigated due to strict regulatory requirements and the depletion of fossil fuel supplies. As a result, of better transportation and population growth, the requirement for energy is increasing daily. Bioethanol may be used successfully to replace both gasoline and spark ignition engine diesel. Most nations blend 10% bioethanol with gasoline in automobiles. Several nations, notably India, have announced that they will soon begin blending 20% bioethanol with gasoline. Bambusa Tulda is used as a raw material for the extraction of bioethanol, which is a type of Indian bamboo. This study covers both the ethanol extraction from bamboo and the effects of various mixtures on spark-ignited engine performance. Four separate blends were developed on a volumetric basis at varying engine speeds, and the wide-open throttle was utilized to evaluate the performance and emissions of each mix with a constant compression ratio of 10:1. When bioethanol was enhanced, combustion efficiency, indicated power, engine power, mechanical efficiency, and volumetric efficiency all increased. Hydrocarbon, carbon monoxide, and carbon dioxide emissions decreased, while nitrogen oxide emissions increased. The engine performance of BE 15 was found to be the greatest among all the gasoline blends tested. According to this study, when nitrogen oxide emission control methods are applied, bamboo may be used as a feedstock for the manufacture of second-generation bioethanol. This invention offers a bioethanol production process that is good for environmental sustainability.

Investigation of bioethanol production from jatropha deoiled cake and its blending effects for environmental sustainability.

This paper describes the process of extracting ethanol from Jatropha curcas and its various blending effects on spark-ignited engine performance for environmental sustainability. Alternatives to conventional fuel sources have to be found because of the depletion of fossil fuels and stringent regulations. Every day, the growing population and improved transportation increase the energy demand. Bioethanol is an effective substitute for gasoline and SI engine diesel. Worldwide, passenger cars typically blend 10% bioethanol with gasoline. Some nations, like India, have stated plans to blend 20% bioethanol with gasoline starting shortly. From leftover jatropha deoiled cake (JDC), bioethanol was produced utilizing the fermentation and vacuum distillation methods. Four different blends were prepared on a volumetric basis at different engine speeds at a constant compression ratio of 10:1 and the wide-open throttle was tested for various performances and emissions. Bioethanol enrichments reduce CO and CO2 emissions but increase nitrogen oxide emissions. JDCE 15 was found to have the best engine performance out of all the fuel blends tested. This study suggests that, if NOx emission reduction measures are carried out, JDC can be used as a source for the manufacturing of second-generation bioethanol.

Operating mode of Brayton-cycle-based pumped thermal electricity storage system: Constant compression ratio or constant rotational speed?

Pumped thermal electricity storage (PTES) is a thermomechanical energy storage technology that offers the advantages of geographical independence, high energy density, and low-cost. It has attracted considerable interest from scholars at home and abroad. At present, research on the thermo-economic performance of this technology is relatively in-depth. However, there remains a lack of research on its operational control strategy, which is crucial for technological industrialisation. This study innovatively proposes two operation modes for compressors and expanders operating at a constant rotational speed (CRS): the CRS-CMF and CRS-VMF modes. The performances under the proposed modes were comprehensively compared with that under the traditional constant compression ratio (CCR) operation mode, and optimisation was performed. The results revealed that the proposed CRS operation mode significantly improved the system storage performance compared to that under the CCR mode. Under the design conditions, the highest round-trip efficiency of 64.67% can be obtained in the CRS-VMF mode. Better output stability was obtained under the CRS-CMF mode, and the delivery power offset ratio reduced from over 50% under the CCR mode to a minimum of 19.13%. When air was used as the working medium, the loss was relatively high; however, better output stability was obtained. Sensitivity analysis showed that a larger charging/discharging duration and upper temperature could achieve better energy storage performance. This research can provide a theoretical basis for formulating appropriate system control schemes and further optimising operational control strategies.

Influence of additive mixed ethanol-biodiesel blends on diesel engine characteristics

Automobile pollution has escalated the environmental degradation manifold, causing climate change. Numerous research works are being carried out to find alternative fuels that can improve efficiencies and limit emission levels. The present research work focuses on experimental investigation of DICI-VCR engine is performed to evaluate the performance and emission (PCE) characteristics using ethanol and Al2O3 nanoparticle blended biodiesel. Nine blends of biodiesel, diesel, and ethanol were prepared on v/v basis. Biodiesel was mixed in constant proportions and Al2O3 nanoparticles were added as additives in the blends with the proportion of 100 ppm. Physical and chemical properties were tested and found within the limits of ASTM D6751 and ASTM D975 standards. Experiments were conducted at constant compression ratio (18:1) with variable loading at full throttle condition. The study showed that the reduction in performance and emission characteristics such as brake thermal efficiency, mechanical efficiency, volumetric efficiency, carbon monoxide, and hydrocarbons ranges from 3.7% to 8.7%, 3.4% to 9.9%, 0.3% to 0.6%, 7.5% to 26.5%, and 8% to 27% respectively whereas increment in brake specific fuel consumption, exhaust gas temperature, carbon dioxide, and oxides of nitrogen as 4.5% to 22.4%, 0.9% to 4.8%, 17.5% to 43%, 4% to 9% respectively observed in comparison with neat diesel.

Numerical study to improve the combustion and thermal efficiencies of off-gas/synthesis gas-fueled HCCI-engine at different loads: Piston-shape and crevice design

This numerical work aims to improve combustion efficiency and thermal efficiency by modifying the piston shape and crevice volume ratio of the HCCI engine operated under excessively lean air-fuel mixture conditions for power generation employment. The baseline piston, optimized for the diesel engine, gives strong reverse squish flow during the expansion stroke, causing a reduction in the efficiency of the engine. Therefore, the flow field in the squish area of the piston bowl should be weakened to facilitate auto-ignition at different points to boost the burning rate. Hence, the baseline piston shape was modified by bringing down the piston bowl depth and reducing the squish area ratio from 34% to 5% with a constant compression ratio. Crevice volume ratio Vcrevice/VTDC is also optimized for the HCCI engine to achieve high performance. All calculations are executed at MBT conditions by changing the inlet temperature of the mixture. Finally, the computational model results are validated with literature data. The results indicate that combustion phasing advances by changing the piston shape, and it also reports that the highest engine combustion efficiency of about 96%, 97%, and 99% are achieved by changing the piston shape and reducing the 40% crevice volume ratio of the engine, at low load, medium load, and high loads, respectively. The results also show that thermal efficiency is improved from 40% to 46% at low load while enhancing from 36 to 38.5% at 10 bar IMEP, respectively.

Betonarme Kirişlerin Moment-Eğrilik ve Etkin Kesit Rijitlkleri

In determining the seismic performance of reinforced concrete (RC) structures in national and international earthquake regulations, it is desired to use effective section stiffness of the cracked section in RC structural elements during the design phase. Although the effective section stiffness of the cracked section is not constant, it depends on parameters such as the concrete strength and reinforcement ratio. In this study, RC beam models with different concrete strength, tensile and compression reinforcement ratios were designed to investigate nonlinear moment-curvature relationships and effective stiffness coefficients. Analytically investigated parameters were calculated from TBEC (2018), ACI318 (2014), ASCE/SEI41 (2017), Eurocode2 (2004) and Eurocode8 (2004, 2005) regulations and moment-curvature relationships. The effective section stiffness coefficient obtained from the analyses were compared with the effective section stiffness coefficient given for RC members in different regulations. The results obtained at the end were examined by comparing them according to different parameters and models. For constant concrete strength and tensile reinforcement ratio in RC beams, with increasing compression reinforcement ratio, effective stiffness coefficient values increase. In RC beams with constant compression and tensile strength ratio, effective stiffness coefficient values increase with increasing concrete strength. The compression reinforcement ratio has been proved to be effective on the maximum moment bearing capacity of the RC beams, effective flexural stiffness and effective stiffness coefficient and ductility of the sections.

Thermodynamic Performance of an Engine by Modifying Piston Bowl Geometries Fuelled by SME-100, LA-100, KB-100 Biodiesel Blends, and Diesel

Simulation of Direct injection (DI) compressed ignition (CI) engine working on diesel thermodynamic cycle on diesel-Rk software carried out for evaluating the effect on thermal performance. The analysis of an engine was worked out by applying different bowl geometrical shapes and by testing with different fuels. Further same compositions were tested on an experimental test rig having a set-up of (compressed ignition, single cylinder, four strokes, air-cooled, direct injection) diesel engine at constant crank speed. Hemispherical (HCC), Shallow depth (SCC), Re-entrant (RCC), Double wedge shallow, and Toroidal (TCC) piston geometries were created in solid-work and analyzed with B-100 blend of SME (Soybean Methyl Ester), KB (Karanja Biodiesel), LA (Roselle Biodiesel) and diesel further they were analyzed and their effects have investigated experimentally and numerically at fully loaded condition, with a constant crank speed of 1500 rpm and by setting constant compression ratio at 17.5. BSFCs were higher by 21.03%, 12.97%, and 12.96% for SME100, KB100, and LA100 with hemispherical, toroidal, and re-entrant type combustion chambers compared with the diesel fuel. Indicated thermal efficiencies and ignition delay periods were reported slightly lower for different blends and pure biodiesel than diesel at specific load conditions whereas combustion durations were reported higher compared to diesel.

Combined effect of multi‐injection scheme, injector nozzle bore, and biodiesel blends on combustion and performance characteristics of diesel engine

AbstractMany researchers have conducted extensive experimental and numerical studies to explore the influences of multiple types of fuels. The high demand of energy in the world has led to the growing crisis and depletion of fossil fuels. Therefore, the researchers have focused on investigating renewable energy sources like biodiesel with the aim of suggesting, which energy is more friendly to the environment. Biodiesel has specifications for using it as an alternative fuel to traditional fossil fuels. Whereas, the use of biodiesel fuel in the original design of Diesel engine can emit a higher percentage of nitrogen oxides (NOx). Therefore, to reduce the harmful emissions of the fuel, the injection schemes and injector nozzle bore (INB) of the engine were modified. The present research combines the effect of the nozzle hole diameters and split injection scheme on the performance and combustion parameters of compression ignition (CI) engine was investigated. The engine was fueled with diesel blended of different proportions (Sp20, Sp40, Sp60, and Sp100) of spirulina biodiesel to prove the suitability of this blend as an alternative fuel. The injector nozzle has three injection holes, and the diameter of the three modified holes of the nozzle is changing (from 0.20 to 0.28 mm, step 0.02 mm) along with two types of scheme injection (double and triple). Furthermore, the influence of the direct injection Diesel‐RK model, single‐cylinder, four‐stroke engine; constant compression ratio (17.5:1), engine speed (1500 rpm), and naturally aspired engine at full load condition are studied. A comparison of the present simulation is compared with published results to validate the present simulation model for conventional baseline Diesel for validation. The simulation was done to investigate and present a comparative study with the conventional baseline Diesel engine. The double injection scheme shows a decrease by 1.8%, 1.7%, and 1.9% for parameters of peak cylinder pressure (PCP), peak cylinder temperature (PCT), and maximum rate of pressure rise, respectively. Whereas, the specific fuel consumption (SFC) and break thermal efficiency are increased by 8.7% and 9.33%, respectively. The results showed a reduction by 2.1%, 20.5%, 22.1%, and 3.2% in PCP, PCT, maximum rate of pressure rise, and break thermal efficiency, respectively. Moreover, the SFC is increased by 3.1% with the modified INB 0.28 (mm).

Fire resistance of composite shear walls filled with demolished concrete lumps and self-compacting concrete

The recycling and reuse of waste concrete is conducive to promoting the sustainable development of resources and practicing the concept of green development. Demolished concrete lumps (DCLs) and self-compacting concrete (SCC) made from waste concrete take full advantage of their recyclability. In order to fully utilize the advantages of demolished concrete lumps and self-compacting concrete in construction, applying demolished concrete lumps and self-compacting concrete to composite shear wall structures is an effective way to reduce costs and improve industrial production. In this paper, a new composite shear wall filled with demolished concrete lumps and self-compacting concrete is proposed, and its fire performance is investigated. The shear wall combines edge constraints of concrete-filled steel tubes, demolished concrete lumps and self-compacting concrete. In order to facilitate the mass pouring of demolished concrete lumps, a cavity is formed between the steel tubes at the ends and the precast walls on both sides. A double-sided fire tests was conducted on three composite shear wall specimens filled with demolished concrete lumps and self-compacting concrete at a constant axial compression ratio, where the fire-retardant coating and the wall width-to-depth ratio were considered as the main test parameters. The specimens were able to steadily withstand the predetermined axial loads during the fire resistance time of 180 min and showed good fire resistance. The concrete temperature variation trends of the three specimens in the wall section were basically the same. The fire-retardant coating on the concealed column had a significant effect on the section temperature of the steel tube, while increasing the wall width-to-depth ratio had little effect. When the axial compression ratio was 0.19, the specimens were in the expansion stage within 180 min and no compression occurred. The results show that the expansion deformation of the shear wall sprayed with fire-retardant coating on the outer surface of the concealed column is smaller than that of the shear wall without fire-retardant coating, and the axial deformation of the composite shear wall infilled with demolished concrete lumps and self-compacting concrete is not affected by increasing the wall width-to-depth ratio.

Performance and Emission Analysis of Modified Compression Ignition Engine from Diesel Engine to Variable Load using Petrol and LPG Fuel

Even though diesel and petrol fuels are utilized largely in various fields it also emits a substantial amount of particulate matter that results in environmental pollution. Several research scholars have worked on modifying an IC engine as a dual fuel mode. But a pilot fuel is required to start the working of alternate fuel. This paper analyzes the modified single-cylinder diesel engine working on a dual fuel mode without pilot fuel. The emission analysis and the performances of the modified engine are working on dual fuel (petrol and liquefied petroleum gas (LPG)) at a constant speed and compression ratio of 7.5. In addition to this, four different emission parameters namely hydrocarbons, carbon monoxide, carbon dioxide as well as nitrogen oxide are computed in this study. Also, the performance analysis is carried out for various engine parameters like total fuel consumption (TFC), Brake specific fuel consumption (BSFC) and Brake thermal efficiency (BTE) for various load conditions. The experimental analysis is performed and it is evident that the LPG fuel performs well with a BTE of about 50.36%; whereas in petrol and diesel the BTE achieved is 18.36% and 27%. Finally, the emission analysis is carried out and the analysis demonstrates that LPG fuel outperforms petrol and diesel with minimum emission rates.

Cryptography and Reference Sequence Based DNA/RNA Sequence Compression Algorithms

This paper proposes two methods for the compression of biological sequences like DNA/RNA. Although many algorithms both lossy and lossless exist in the literature, they vary by the compression ratio. Moreover, existing algorithms show different compression ratios for different inputs. Our proposed methods exhibit nearly constant compression ratio which helps us to know the amount of storage needed in advance. For the first method, we call it CryptoCompress, we use a blend of Cryptographic hash function and partition theory to achieve this compression. The second method, we call it RefCompress, uses a reference DNA for compression. This paper showcases that the proposed methods have constant compression ratio compared to most of the existing methods.

The effect of fuel injection pressure and combustion chamber configuration on fuel spray, combustion and emissions of a direct injection diesel engine: a CFD approach

In the present study, the combined impacts of injection pressure and piston bowl configuration on fuel–air mixing, combustion and emissions of a diesel engine have been analysed numerically. An investigation has been conducted at four different fuel injection pressures and three different combustion chamber configurations for the same bowl volume to have a constant compression ratio. The in-cylinder transient flow and subsequent turbulent combustion process have been modelled using computational fluid dynamics code AVL FIRE. The predicted results indicate that the brake-specific fuel consumption (BSFC) is decreased by 4.19%, 8.96% and 11.92% for HCC, 5.77%, 9.92% and 13.68% for CCC, and 5.13%, 9.19% and 12.92% for TRCC when engine operates with an injection pressure of 215, 230 and 250 bar, respectively compared to 200 bar at full load operation. Soot emissions for CCC and TRCC engines are decreased by 23.4% and 33.43%, respectively, compared to baseline HCC engines.

Comparative Assessment of Engine Vibration, Combustion, Performance, and Emission Characteristics Between Single and Twin-Cylinder Diesel Engines in Unifuel and Dual-Fuel Mode

Abstract The persistent efforts among the researchers are being done to reduce emissions by the exploration of different alternative fuels. The application of alternative fuel is also found to influence engine vibration. The present study explores the potential connection between the change of the engine operating parameters and the engine vibration pattern. The objective is to analyze the effect of alternative fuel on engine vibration and performance. The experiments are performed on two different engines of single cylinder (SC) and twin-cylinder (TC) variants at the load range of 0–34 Nm, with steps of 6.8 Nm and at the constant speed of 1500 rpm. The single cylinder engine, fueled with only diesel mode, is tested at two compression ratios (CRs) of 16.5 and 17.5. However, the twin-cylinder engine with a constant compression ratio of 16.5 is tested at both diesel unifuel and diesel-compressed natural gas (CNG) dual-fuel modes. Further, in dual-fuel mode, tests are conducted with compressed natural gas substitutions of 40%, 60%, and 80% for given loads and speed. The engine vibration signatures are measured in terms of root mean square (RMS) acceleration, representing the amplitude of vibration. The combustion parameters considered are cylinder pressure, rate of pressure rise, heat release rate (HRR), and ignition delay. At higher loads, the vibration amplitude increases along with the cylinder pressure. The maximum peak cylinder pressure (PCP) of 95 bar is found in the case of the single cylinder engine at the highest load condition that also produced a peak vibration of 3219 m/s2.

Exploring the Effects of Piston Bowl Geometry and Injector Included Angle on Dual-Fuel and Single-Fuel RCCI

Abstract Reactivity control compression ignition (RCCI) is a low-temperature combustion technique that has been proposed to meet the current demand for high thermal efficiency and low engine-out emissions. However, its requirement of two separate fuel systems (i.e., a low-reactivity fuel system and a high-reactivity fuel system) has been one of its major challenges in the last decade. This leads to the single-fuel RCCI concept, where the secondary fuel (reformates of diesel) is generated from the primary fuel (diesel) through catalytic partial oxidation reformation. Following the in-depth analysis of the reformate fuel (reformates of diesel) and its benefit as the low-reactivity fuel with diesel, the effects of the start of injection (SOI) timing of diesel and the energy-based blend ratio were also studied in detail. In this study, the effects of piston profile and the injector included angles were experimentally examined using both conventional fuel pairs (gasoline—diesel and natural gas—diesel) and reformate RCCI. A validated computational fluid dynamics (CFD) model was also used for a better understanding of the experimental trends. Comparing a reentrant bowl piston with a shallow bowl piston at a constant compression ratio and SOI, the latter showed better thermal efficiency, regardless of the fuel combination, due to its 10% lower surface area for the heat transfer. Comparing the 150-degree included angle and 60-degree included angle on the shallow bowl piston, the latter showed better combustion efficiency, regardless of the fuel combination, due to its earlier combustion phasing (at constant SOI timing). The effect was particularly prominent on reformate RCCI because of its incredibly high diluent concentration, which retards the combustion further for the 150-deg injector. Later, using convergecfd, seven different injector included angles were studied at a constant SOI. With the change in injector included angle, the region of the cylinder targeted by the fuel spray varies significantly, and it was found to have a significant impact on the combustion efficiency and the engine-out emissions. As the injector included angle changed from 60-deg to 150-deg, the combustion efficiency increased by 15% and the CO, NOx, and HC emissions decreased by 96%, 70%, and 86%, respectively.