Effect of equivalence ratio on diesel direct injection spark ignition combustion

Aviation heavy-fuel spark ignition(SI)piston engines have been paid more and more attention in the area of small aviation.Aviation heavy-fuel refers to aviation kerosene or light diesel fuel,which is safer to use and store compared to gasoline fuel.And diesel fuel is more suitable for small aviation application on land.In this study,numerical simulation was performed to evaluate the possibility of switching from gasoline direct injection spark ignition(DISI)to diesel DISI combustion.Diesel was injected into the cylinder by original DI system and ignited by spark.In the simulation,computational models were calibrated by test data from a DI engine.Based on the calibrated models,furthermore,the behavior of diesel DISI combustion was investigated.The results indicate that diesel DISI combustion is slower compared to gasoline,and the knock tendency of diesel in SI combustion is higher.For a diesel/air mixture with an equivalence ratio of 0.6 to 1.4,higher combustion pressure and faster burning rate occur when the equivalence ratios are 1.2 and 1.0,but the latter has a higher possibility of knock.In summary,the SI combustion of diesel fuel with a rich mixture can achieve better combustion performance in the engine.

Study of the Combustion Process inside an Ethanol-Diesel Dual Direct Injection Engine Based on a Non-Uniform Injection Approach

The use of ethanol is a promising method to reduce the emissions of diesel engines.The present study has been based on the installation of a gasoline electronic injection system in a single-cylinder diesel engine to control the amount of ethanol entering the cylinder during the compression(while diesel has been injected into the cylinder by the original pump injection system).The injection time has been controlled by crank angle signal collected by an AVL angle indicator.In the tests ethanol and diesel each accounted for half of the fuel volume,and the total heat energy supply of the fuel was equivalent to that of the diesel under the operating conditions of the original engine.A three-dimensional combustion model of the diesel engine has been implemented by using the CFD software FIRE.Simulations have been carried out assuming uniform and non-uniform injections rate for the different holes and the different results have been compared.According to these results,a non-uniform injection rate can produce early ignition and cause an increase in the maximum in-cylinder pressure and the maximum average incylinder temperature.Moreover,in such conditions NO emissions are larger while soot emission is slightly lower.

Mixture Preparation and Combustion of CNG Low-Pressure Compound Direct Injection Spark-Ignited Engines

A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.

Application of Waste Biomass Pyrolysis Oil in a Direct Injection Diesel Engine： For a Small Scale Non-Grid Electrification

The population which could not access to electricity was around 1.2 billion in 2010 and is distributed in many low developing countries. With the increase in the population and the economic growth in those countries, waste generation is growing rapid especially for the organic and the plastic, and the uncontrolled waste disposal is becoming more serious issues to manage it. The interest on waste to energy is growing by the above drivers. This research was carried out for aiming to the real world adaption at the minimum cost of the pyrolysis oil from waste biomass in a diesel engine, mainly for electricity generation. The proposal of the appropriate adaptable blend ratio was the major scope rather than the optimization of the engine parameters. For the sake of it, the pyrolysis oil of the waste biomass was produced from a gasification pilot plant in Japan and blended with biodiesel at minimum effort. A small single cylinder diesel engine （direct injection） was used for the experiment with regard to full load power-output, exhaust emissions and fuel consumption.

Research on the application technique of the natural gas engine with direct injection

Based on the analysis of the advantages of the Natural Gas Engine with Direct Injection （NGEDI） and the state of the art of the research in this area, the authors point out that, the NGEDI with high pressure is one potential selection and will have a good application prospects. Through investigation experiment and simulation results, the key techniques are put foreword for deployment of the NGEDI and some solutions are given.

Study on Strategies for Methane Injection in a DISI （Direct Injection Spark Ignition） Engine

This paper deals with the application of two different injection strategies in a natural gas direct injection spark ignition single-cylinder engine model. The analysis includes the air flow characterization during compression stroke and also the charge stratification. Two different swirl ratios are applied and piston bowl effects are analyzed during the gas jet deflection towards the spark plug. Achieving wall-guided effect, consequently, the charge stratification in spark plug region is obtained. The goal is to study the mixture formation differences for a single and a bi pulsed CNG （compressed natural gas） injection profiles and check the evolution of the methane concentration at the spark plug at the start of combustion.

Direct in vivo injection of ^(131)I-GMS and its distribution and excretion in rabbit

AIM: To explore the distribution and metabolism of 131 I-gelatin microspheres ( 131 I-GMSs) in rabbits after direct injection into rabbits’ livers.METHODS: Twenty-eight healthy New Zealand rabbits were divided into seven groups,with four rabbits per group.Each rabbit’s hepatic lobes were directly injected with 41.336 ± 5.106 MBq 131 I-GMSs.Each day after 131 I-GMSs administration,4 rabbits were randomly selected,and 250 μL of serum was collected for γ count.Hepatic and thyroid functions were tested on days 1,4,8,16,24,32,48 and 64 after 131 I-GMSs administration.Single-photon emission computed tomography (SPECT) was taken for each group on days 0,1,4,8,16,24,32,48,64 after 131 I-GMSs administration.A group of rabbits were sacrificed respectively on days 1,4,16,24,32,48,64 after 131 I-GMSs administration.Their livers were taken out for histological examination.RESULTS: After 131 I-GMSs administration,the nuclide was collected in the hepatic area with microspheres.The radiation could be detected on day 48 after 131 IGMSs administration,and radiography could be seen in thyroid areas in SPECT on days 4,8,16 and 24.One day after 131 I-GMSs administration,the liver function was damaged but recovered 4 d later.Eight days after 131 I-GMSs administration,the levels of free triiodothyronine and free thyroxin were reduced,which restored to normal levels on day 16.Histological examination showed that the microspheres were degraded to different degrees at 24,32 and 48 d after 131 I-GMSs administration.The surrounding parts of injection points were in fibrous sheathing.No microspheres were detected in histological examination on day 64 after 131 I-GMSs administration.CONCLUSION: Direct in vivo injection of 131 I-GMSs is safe in rabbits.It may be a promising method for treatment of malignant tumors.

Improved direct power injection model of 16-bit microcontroller for electromagnetic immunity prediction

To promote the modeling standardization process of the integrated circuits, an improved electrical simulation model for a direct power injection （DPI） setup which was used to measure the conducted immunity of a 16-bit microcontroller to radio frequency aggression was investigated. Based on the existing model of the same microcontroller, the PDN module was modified by adding the core, PLL and MD network models, which could reflect the actual electric distribution situation within the microcontroller more accurately. By comparing the simulation results with the measurement results, the effectiveness of the modified model can be improved to 500 MHz, and its uncertainty is within ＋1.8 dB （＋2 dB is acceptable）. Then, to improve the simulation accuracy of the complete model in the high frequency range, the I/O model which contained the dynamic and nonlinear characteristics reflecting the variation of the internal impedance of the microcontroller with increasing the frequency of the external noise was introduced. By comparing the simulation results with the measurement results, the effectiveness of the second modified model can be improved up to 1.4 GHz with the uncertainty of ~1.8 dB. Thus, a conclusion can be reached that the proposed model can be applied to a much wider frequency range with a smaller uncertainty than the latest model of the similar type. Furthermore, associated with the electromagnetic emission testing platform model, the PDN module can also be used to predict the electromagnetic conducted and radiated emission characteristics. This modeling method can also be applied to other integrated circuits, which is very helpful to the standardization of the IC electromagnetic compatibility （EMC） modeling process.

Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

This study focused on the effects of vessel and water temperatures on direct injection in internal combustion Rankine cycle engines through experimental and numerical methods.First,a study was carried out with schlieren photography using a high-speed camera for simultaneous liquid–gas diagnoses.Water was directly injected into a constant-volume vessel that provided stable boundaries.We wrote a MATLAB program to calculate spray tip penetration and cone angle from the images.For the further extension of boundary conditions,a numerical model was established and calibrated in AVL-FIRE for the thorough analysis of injection characteristics.Both experimental and numerical results indicated that injection and vessel temperatures have different effects on spray tip penetration.An increase in injected water temperature leads to shorter spray tip penetration,while the spray tip penetration increases with increasing vessel temperature.However,increased injection and vessel temperatures can both decrease the spray cone angle.Moreover,the simulation results also suggested that heat conduction is a main factor in boosting evaporation under top dead center conditions.When the internal energy of water parcels surges,these parcels evaporate immediately.These results are helpful and crucial for internal combustion engines equipped with direct water injection technology.

Investigations on High-Speed Flash Boiling Atomization of Fuel Based on Numerical Simulations

Flash boiling atomization(FBA)is a promising approach for enhancing spray atomization,which can generate a fine and more evenly distributed spray by increasing the fuel injection temperature or reducing the ambient pressure.However,when the outlet speed of the nozzle exceeds 400 m/s,investigating high-speed flash boiling atomization(HFBA)becomes quite challenging.This difficulty arises fromthe involvement ofmany complex physical processes and the requirement for a very fine mesh in numerical simulations.In this study,an HFBA model for gasoline direct injection(GDI)is established.This model incorporates primary and secondary atomization,as well as vaporization and boilingmodels,to describe the development process of the flash boiling spray.Compared to lowspeed FBA,these physical processes significantly impact HFBA.In this model,the Eulerian description is utilized for modeling the gas,and the Lagrangian description is applied to model the droplets,which effectively captures the movement of the droplets and avoids excessive mesh in the Eulerian coordinates.Under various conditions,numerical solutions of the Sauter mean diameter(SMD)for GDI show good agreement with experimental data,validating the proposed model’s performance.Simulations based on this HFBA model investigate the influences of fuel injection temperature and ambient pressure on the atomization process.Numerical analyses of the velocity field,temperature field,vapor mass fraction distribution,particle size distribution,and spray penetration length under different superheat degrees reveal that high injection temperature or low ambient pressure significantly affects the formation of small and dispersed droplet distribution.This effect is conducive to the refinement of spray particles and enhances atomization.

Fuel Spray Dynamic Characteristics of GDI High Pressure Injection System

In order to improve the fuel consumption and exhaust emission for gasoline engines,gasoline direct injection（GDI） system is spotlighted to solve these requirements.Thus,many researchers focus on the investigation of spray characteristics and the fuel formation of GDI injector.This paper presents a complete numerical and experimental characterization of transient gasoline spray from a high pressure injection system equipped with a modern single-hole electric controlled injector in a pressurized constant volume vessel.The numerical analysis is carried out in a one-dimensional model of fuel injection system which is developed in the AVL HYDSIM environment.The experimental analyses are implemented through a self-developed injection rate measurement device and spray evolution visualization system.The experimental results of injection rate and spray dynamics are taken to tune and validate the built model.The visualization system synchronize a high speed CMOS camera to obtain the spray structure,moreover,the captured images are taken to validate the injector needle lift process which is simulated in the model.The reliability of the built model is demonstrated by comparing the numerical results with the experimental data.The formed vortex structure at 0.8 ms is effectively disintegrated at 6.2 ms and the spray dynamics become rather chaotic.The fuel flow characteristics within injector nozzle extremely influence the subsequent spray evolution,and therefore this point should be reconsidered when building hybrid breakup GDI spray model.The spray tip speed reach the maximum at 1.18 ms regardless of the operation conditions and this is only determined by the injector itself.Furthermore,an empirical equation for the spray tip penetration is obtained and good agreement with the measured results is reached at a certain extent.This paper provides a methodology for the investigation of spray behavior and fuel distribution of GDI engine design.

Combustion and emission characteristics of a dual injection system applied to a DISI engine

Concerns about environmental pollution and energy shortages have increased worldwide. One approach to reduce CO2 emissions from gasoline engines is to achieve stratified charge combustion with various injection ratios using port fuel injection （PFI） and direct injection. The combustion and emission characteristics of a 4-valve direct injection spark ignition （DISI） engine equipped with a dual injection system were investigated while the injection ratio was varied. When the direct injection ratio increased, the lean limit A/F was extended. This suggests that the dual injection gasoline engine with both PFI and direct injection can meet severe vehicle emission and fuel economy requirements. The dual injection system had higher combustion pressure than that of either a conventional or direct injection systems. Therefore, the engine power of a dual injection DISI engine would be higher than that of a single injection DISI engine. However, NOx emissions increased compared with the emission levels in both PFI and DISI systems.

Effects of different combustion modes on the thermal efficiency and emissions of a diesel pilot-ignited natural gas engine under low-medium loads

Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.

Optimal concentration of mesenchymal stem cells for fracture healing in a rat model with long bone fracture

BACKGROUND There is still no consensus on which concentration of mesenchymal stem cells(MSCs)to use for promoting fracture healing in a rat model of long bone fracture.AIM To assess the optimal concentration of MSCs for promoting fracture healing in a rat model.METHODS Wistar rats were divided into four groups according to MSC concentrations:Normal saline(C),2.5×10^(6)(L),5.0×10^(6)(M),and 10.0×10^(6)(H)groups.The MSCs were injected directly into the fracture site.The rats were sacrificed at 2 and 6 wk post-fracture.New bone formation[bone volume(BV)and percentage BV(PBV)]was evaluated using micro-computed tomography(CT).Histological analysis was performed to evaluate fracture healing score.The protein expression of factors related to MSC migration[stromal cell-derived factor 1(SDF-1),transforming growth factor-beta 1(TGF-β1)]and angiogenesis[vascular endothelial growth factor(VEGF)]was evaluated using western blot analysis.The expression of cytokines associated with osteogenesis[bone morphogenetic protein-2(BMP-2),TGF-β1 and VEGF]was evaluated using real-time polymerase chain reaction.RESULTS Micro-CT showed that BV and PBV was significantly increased in groups M and H compared to that in group C at 6 wk post-fracture(P=0.040,P=0.009;P=0.004,P=0.001,respectively).Significantly more cartilaginous tissue and immature bone were formed in groups M and H than in group C at 2 and 6 wk post-fracture(P=0.018,P=0.010;P=0.032,P=0.050,respectively).At 2 wk post fracture,SDF-1,TGF-β1 and VEGF expression were significantly higher in groups M and H than in group L(P=0.031,P=0.014;P<0.001,P<0.001;P=0.025,P<0.001,respectively).BMP-2 and VEGF expression were significantly higher in groups M and H than in group C at 6 wk postfracture(P=0.037,P=0.038;P=0.021,P=0.010).Compared to group L,TGF-β1 expression was significantly higher in groups H(P=0.016).There were no significant differences in expression levels of chemokines related to MSC migration,angiogenesis and cytokines associated with osteogenesis between M and H groups at 2 and 6 wk post-fracture.CONCLUSION The administration of at least 5.0×10^(6)MSCs was optimal to promote fracture healing in a rat model of long bone fractures.

Test and Analysis for Spraying Ammonia in Diesel Engine

A certain amount of ammonia reducer were directly injected into the 4102BZLQ Diesel engine's combustion chamber when the combustion temperature decreases to 1573-1073K, NOx generated could be reduced to 1.11g/(kW·h). Based on PRF combustion mechanism, NO was tested by using the heavy-duty diesel engine test cycle of ESC thirteen conditions[1], the ammonia spray angle and amount were tested and optimized in different conditions. The test results show that the thermal efficiency of Diesel engine does not decrease while NO exhaust decreases.

Recent Progress in Heavy Fuel Aviation Piston Engine

Heavy fuel aviation piston engines(HF-APEs)refer to the engine using fuels with high flash point,such as kerosene or light diesel.Here technique specifications of some classical foreign HF-APEs(Hirth3503,Zanzottera 498)are introduced.Recent progress and trend of fuel injection,fuel ignition,working cycle,intake charging,thermal management and electronic control of HF-APE are compared and summarized.Emphases are put on the technological difficulties,solutions and development tendency in the design,retrofitting and manufacturing of HF-APE aiming to provide references for the research of related area and the development of prototype HF-APE in China.

Simulation and Experimental Research on Fuel Spray Characteristics of a Self-pressurized Injector

As a miniaturized direct injection(DI)solution,a self-pressurized injector is of great significance for small aviation piston engines,such as spark-ignited two-stroke heavy-fuel engines.The spray characteristics of DI injectors are an important application prerequisite.In this paper,the computational fluid dynamics(CFD)software AVL Fire is employed to study the spray characteristics.Two types of spray models are established based on the Han Sheet model and the KH-RT model,and simulation works are carried out according to two types of spray tests in the literature.The comparison results show that in the constant volume bomb test,the spray patterns obtained by simulation under the two sets of environmental pressures are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray contraction of the near nozzle field and the vortex of the far nozzle field better.In the tube test,the spray patterns obtained by simulation under the five sets of flow velocity are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray expansion and the vortex of the far nozzle field better.The RP-3 kerosene spray characteristics of the self-pressurized injector are also experimentally studied,and the results demonstrate that due to the higher viscosity of kerosene,the spray shrinks more easily,resulting in a smaller spray cone angle and larger penetration.Therefore,changes in environmental pressure have greater impact on the kerosene spray pattern.

Application of direct steam injection system to minimize browning of white radish(Raphanus sativus)broth during sterilization

Direct steam injection(DSI)was applied to minimize the quality changes of white radish(Raphanus sativus)broth during sterilization.This study compared the degree of browning of white radish broth from a retort sterilization system and a DSI system.The quality changes after thermal treatments,such as retorting and DSI,were evaluated by Lab color values,the browning index(BI)and sensory evaluation.As the volume of the retort pouch increased,the thermal processing time increased.Significant increases of a and b values,color difference and BI were observed.Unlike the retort sterilization,the DSI treatment showed no significant differences in color properties of the radish broth with a wide range of sterilization temperature.The highest sensory score among the DSI treated samples was observed at the lowest sterilization temperature(125℃).The results demonstrated that the DSI treatment showed a higher stability in the quality associated with the browning reaction,such as the color indices and BI because the DSI process rapidly increased the temperature of the radish broth by transferring the latent heat of steam to the fluid.

Applying a new method for direct collection, volume quantification and determination of N_2 emission from water

The emission of N2 is important to remove excess N from lakes, ponds, and wetlands. To investigate the gas emission from water, Gao et al.（2013） developed a new method using a bubble trap device to collect gas samples from waters. However, the determination accuracy of sampling volume and gas component concentration was still debatable. In this study, the method was optimized for in situ sampling, accurate volume measurement and direct injection to a gas chromatograph for the analysis of N2 and other gases. By the optimized new method, the recovery rate for N2 was 100.28% on average; the mean coefficient of determination（R2） was 0.9997; the limit of detection was 0.02%. We further assessed the effects of the new method, bottle full of water, vs. vacuum bag and vacuum vial methods, on variations of N2 concentration as influenced by sample storage times of 1,2, 3, 5, and 7 days at constant temperature of 15°C, using indices of averaged relative peak area（%） in comparison with the averaged relative peak area of each method at 0 day.The indices of the bottle full of water method were the lowest（99.5%–108.5%） compared to the indices of vacuum bag and vacuum vial methods（119%–217%）. Meanwhile, the gas chromatograph determination of other gas components（O2, CH4, and N2O） was also accurate. The new method was an alternative way to investigate N2 released from various kinds of aquatic ecosystems.

Frontier science and challenges on offshore carbon storage

Carbon capture and storage(CCS)technology is an imperative,strategic,and constitutive method to considerably reduce anthropogenic CO_(2)emissions and alleviate climate change issues.The ocean is the largest active carbon bank and an essential energy source on the Earth's surface.Compared to oceanic nature-based carbon dioxide removal(CDR),carbon capture from point sources with ocean storage is more appropriate for solving short-term climate change problems.This review focuses on the recent state-of-the-art developments in offshore carbon storage.It first discusses the current status and development prospects of CCS,associated with the chailenges and uncertainties of oceanic nature-based CDR.The second section outlines the mechanisms,sites,advantages,and ecologic hazards of direct offshore CO_(2)injection.The third section emphasizes the mechanisms,schemes,influencing factors,and recovery efficiency of ocean-based CO-CH_(4)replacement and CO_(2)-enhanced oil recovery are reviewed.In addition,this review discusses the economic aspects of offshore CCS and the preponderance of offshore CCs hubs.Finally,the upsides,limitations,and prospects for further investigation of offshore CO_(2)storage are presented.