Nozomu Hashimoto

Bio: Nozomu Hashimoto is an academic researcher from Hokkaido University. The author has contributed to research in topics: Combustion & Pulverized coal-fired boiler. The author has an hindex of 18, co-authored 58 publications receiving 989 citations. Previous affiliations of Nozomu Hashimoto include Central Research Institute of Electric Power Industry.

Fundamental combustion characteristics of palm methyl ester (PME) as alternative fuel for gas turbines

Abstract: To investigate the combustion characteristics of palm methyl ester (PME) as an alternative fuel for gas turbines, combustion experiments at atmospheric pressure using high-temperature air (673 K) were performed. Chemical equilibrium calculations and investigations of fuel atomizing characteristics using a laser diffraction spray analyzer (LDSA) were also conducted. The results show that combustion characteristics of PME are similar to those of diesel fuel. Furthermore, it is indicated that NO x emissions can be reduced by using PME instead of diesel fuel for gas turbines.

A numerical simulation of pulverized coal combustion employing a tabulated-devolatilization-process model (TDP model)

Abstract: A new coal devolatilization model employing a tabulated-devolatilization-process model (TDP model) is developed, and its validity is investigated by performing a numerical simulation of a pulverized coal combustion field formed by an industrial low-NOx burner in a 100 kg-coal/h test furnace. The predicted characteristics of the pulverized coal combustion field obtained from the simulation employing the TDP model are compared with those employing the conventional devolatilization model, those employing the two competing reaction rate model, and the experiments. The results show that drastic differences in the gas flow patterns and coal particle behavior appear between simulations. In particular, the recirculation flow behavior is strongly affected by the difference in the coal devolatilization model because of the difference in the volatile matter evolution rate. The TDP model captures the observed behavior of the coal particles in the experiment better than the other models. Although it is considered that by adjusting the devolatilization parameters the prediction similar to the TDP model is also possible by the other models, appropriate devolatilization parameters are automatically set to particles depending on the particle heating rate without trial–error method by employing the TDP model.

Numerical simulation of pulverized coal jet flame employing the TDP model

Abstract: The effect of the devolatilization model on the coal particle behavior is investigated in detail by performing numerical simulations of a simple pulverized coal jet flame formed by a small jet burner (0.5 kg-coal/h) [S. Hwang et al., Energy & Fuels 2005;19:382–92]. As the devolatilization model, widely-used conventional devolatilization model, two competing reaction rate model and newly-proposed tabulated-devolatilization-process model (TDP model) [N. Hashimoto et al., Combust Flame 2012;159:353–366] are used. The results show that the coal particle velocities predicted by the TDP model are in better agreement with the experiments than those by the other models, with a slight increase in computation time. The difference in the mean axial particle velocity between the simulations is caused by the difference in the axial gas velocity, which is ultimately caused by the difference in the volatile matter evolution rate. It is also found that the devolatilization model has great influence on particle velocity prediction compared to the turbulence model, the gas-phase combustion model and the radiation model.

Evaporation characteristics of a palm methyl ester droplet at high ambient temperatures

Abstract: To investigate the evaporation characteristics of a palm methyl ester (PME) droplet at high ambient temperatures, droplet evaporation experiments were conducted. Thermogravimetric and differential thermal analyses (TG–DTA) were also conducted to investigate the presence of exothermic reactions during fuel evaporation. The results for PME were compared with those for diesel fuel and n-hexadecane. The results show that the initial heating period decreases and the average evaporation coefficient increases with increasing ambient temperature for all fuels. As a results, the droplet lifetime decreases with increasing ambient temperature for all fuels. It was found that the droplet lifetime of PME is longer than that of diesel fuel and n-hexadecane. The average evaporation coefficients of PME and diesel fuel are almost equal. The longer initial heating period of PME due to the higher boiling points of the components leads to the longer droplet lifetime. It was also found that exothermic reactions occur during PME droplet evaporation. The exothermic reactions are considered to be polymerization reactions of the unsaturated fatty acid methyl esters. The volume of the residue formed by the polymerization reactions decreases with increasing ambient temperature due to the shorter reaction time before complete evaporation.

Soot formation characteristics in a lab-scale turbulent pulverized coal flame with simultaneous planar measurements of laser induced incandescence of soot and Mie scattering of pulverized coal

Abstract: Soot formation characteristics of a lab-scale pulverized coal flame were investigated by performing carefully controlled laser diagnostics. The spatial distributions of soot volume fraction and the pulverized coal particles were measured simultaneously by laser induced incandescence (LII) and Mie scattering imaging, respectively. In addition, the radial distributions of the soot volume fraction were compared with the OH radical fluorescence, gas temperature and oxygen concentration obtained in our previous studies [1] , [2] . The results indicated that the laser pulse fluence used for LII measurement should be carefully controlled to measure the soot volume fraction in pulverized coal flames. To precisely measure the soot volume fraction in pulverized coal flames using LII, it is necessary to adjust the laser pulse fluence so that it is sufficiently high to heat up all the soot particles to the sublimation temperature but also sufficiently low to avoid including a too large of a change in the morphology of the soot particles and the superposition of the LII signal from the pulverized coal particles on that from the soot particles. It was also found that the radial position of the peak LII signal intensity was located between the positions of the peak Mie scattering signal intensity and peak OH radical signal intensity. The region, in which LII signal, OH radical fluorescence and Mie scattering coexisted, expanded with increasing height above the burner port. It was also found that the soot formation in pulverized coal flames was enhanced at locations where the conditions of high temperature, low oxygen concentration and the existence of pulverized coal particles were satisfied simultaneously.

The Self-medication Hypothesis of Substance Use Disorders: A Reconsideration and Recent Applications

Abstract: The self-medication hypothesis of addictive disorders derives primarily from clinical observations of patients with substance use disorders. Individuals discover that the specific actions or effects of each class of drugs relieve or change a range of painful affect states. Self-medication factors occur in a context of self-regulation vulnerabilities--primarily difficulties in regulating affects, self-esteem, relationships, and self-care. Persons with substance use disorders suffer in the extreme with their feelings, either being overwhelmed with painful affects or seeming not to feel their emotions at all. Substances of abuse help such individuals to relieve painful affects or to experience or control emotions when they are absent or confusing. Diagnostic studies provide evidence that variously supports and fails to support a self-medication hypothesis of addictive disorders. The cause-consequence controversy involving psychopathology and substance use/abuse is reviewed and critiqued. In contrast, clinical observations and empirical studies that focus on painful affects and subjective states of distress more consistently suggest that such states of suffering are important psychological determinants in using, becoming dependent upon, and relapsing to addictive substances. Subjective states of distress and suffering involved in motives to self-medicate with substances of abuse are considered with respect to nicotine dependence and to schizophrenia and posttraumatic stress disorder comorbid with a substance use disorder.

Biodiesel production, properties, and feedstocks

Abstract: Biodiesel, defined as the mono-alkyl esters of vegetable oils or animal fats, is an environmentally attractive alternative to conventional petroleum diesel fuel (petrodiesel). Produced by transesterification with a monohydric alcohol, usually methanol, biodiesel has many important technical advantages over petrodiesel, such as inherent lubricity, low toxicity, derivation from a renewable and domestic feedstock, superior flash point and biodegradability, negligible sulfur content, and lower exhaust emissions. Important disadvantages of biodiesel include high feedstock cost, inferior storage and oxidative stability, lower volumetric energy content, inferior low-temperature operability, and in some cases, higher NO x exhaust emissions. This review covers the process by which biodiesel is prepared, the types of catalysts that may be used for the production of biodiesel, the influence of free fatty acids on biodiesel production, the use of different monohydric alcohols in the preparation of biodiesel, the influence of biodiesel composition on fuel properties, the influence of blending biodiesel with other fuels on fuel properties, alternative uses for biodiesel, and value-added uses of glycerol, a co-product of biodiesel production. A particular emphasis is placed on alternative feedstocks for biodiesel production. Lastly, future challenges and outlook for biodiesel are discussed.

A review of battery fires in electric vehicles

Abstract: Over the last decade, the electric vehicle (EV) has significantly changed the car industry globally, driven by the fast development of Li-ion battery technology. However, the fire risk and hazard associated with this type of high-energy battery has become a major safety concern for EVs. This review focuses on the latest fire-safety issues of EVs related to thermal runaway and fire in Li-ion batteries. Thermal runaway or fire can occur as a result of extreme abuse conditions that may be the result of the faulty operation or traffic accidents. Failure of the battery may then be accompanied by the release of toxic gas, fire, jet flames, and explosion. This paper is devoted to reviewing the battery fire in battery EVs, hybrid EVs, and electric buses to provide a qualitative understanding of the fire risk and hazards associated with battery powered EVs. In addition, important battery fire characteristics involved in various EV fire scenarios, obtained through testing, are analysed. The tested peak heat release rate (PHHR in MW) varies with the energy capacity of LIBs ($$E_{B}$$ in Wh) crossing different scales as $$PHRR = 2E_{B}^{0.6}$$. For the full-scale EV fire test, limited data have revealed that the heat release and hazard of an EV fire are comparable to that of a fossil-fuelled vehicle fire. Once the onboard battery involved in fire, there is a greater difficulty in suppressing EV fires, because the burning battery pack inside is inaccessible to externally applied suppressant and can re-ignite without sufficient cooling. As a result, an excessive amount of suppression agent is needed to cool the battery, extinguish the fire, and prevent reignition. By addressing these concerns, this review aims to aid researchers and industries working with batteries, EVs and fire safety engineering, to encourage active research collaborations, and attract future research and development on improving the overall safety of future EVs. Only then will society achieve the same comfort level for EVs as they have for conventional vehicles.

Laser-induced incandescence: Particulate diagnostics for combustion, atmospheric, and industrial applications

Abstract: The understanding of soot formation in combustion processes and the optimization of practical combustion systems require in situ measurement techniques that can provide important characteristics, such as particle concentrations and sizes, under a variety of conditions. Of equal importance are techniques suitable for characterizing soot particles produced from incomplete combustion and emitted into the environment. Additionally, the production of engineered nanoparticles, such as carbon blacks, may benefit from techniques that allow for online monitoring of these processes. In this paper, we review the fundamentals and applications of laser-induced incandescence (LII) for particulate diagnostics in a variety of fields. The review takes into account two variants of LII, one that is based on pulsed-laser excitation and has been mainly used in combustion diagnostics and emissions measurements, and an alternate approach that relies on continuous-wave lasers and has become increasingly popular for measuring black carbon in environmental applications. We also review the state of the art in the determination of physical parameters central to the processes that contribute to the non-equilibrium nanoscale heat and mass balances of laser-heated particles; these parameters are important for LII-signal analysis and simulation. Awareness of the significance of particle aggregation and coatings has increased recently, and the effects of these characteristics on the LII technique are discussed. Because of the range of experimental constraints in the variety of applications for which laser-induced incandescence is suited, many implementation approaches have been developed. This review discusses considerations for selection of laser and detection characteristics to address application-specific needs. The benefits of using LII for measurements of a range of nanoparticles in the fields mentioned above are demonstrated with some typical examples, covering simple flames, internal-combustion engines, exhaust emissions, the ambient atmosphere, and nanoparticle production. We also remark on less well-known studies employing LII for particles suspended in liquids. An important aspect of the paper is to critically assess the improvement in the understanding of the fundamental physical mechanisms at the nanoscale and the determination of underlying parameters; we also identify further research needs in these contexts. Building on this enhanced capability in describing the underlying complex processes, LII has become a workhorse of particulate measurement in a variety of fields, and its utility continues to be expanding. When coupled with complementary methods, such as light scattering, probe-sampling, molecular-beam techniques, and other nanoparticle instrumentation, new directions for research and applications with LII continue to materialize.

Modelling of fuel droplet heating and evaporation: Recent results and unsolved problems

Abstract: The most recent developments in the modelling of heating and evaporation of fuel droplets, the results of which were published in 2014–2017, are reviewed, and the most important unsolved problems are identified. Basic principles of power law and polynomial approximations and the heat balance method for modelling the heating of non-evaporating droplets are discussed. Several approaches to modelling the heating of evaporating droplets, predicting different heating and evaporation characteristics, are compared. New results in modelling heating and evaporation of spheroidal droplets are identified. Basic principles of the Discrete Component Model and its application to biodiesel fuel droplets are summarised. Main ideas of the Multi-dimensional Quasi-discrete Model and its applications to Diesel and gasoline fuel droplets are discussed. New developments in gas phase evaporation models for multi-component fuel droplets are presented. A self-consistent kinetic model for droplet heating and evaporation is described. New approaches to the estimation of the evaporation coefficient, including those taking into account quantum-chemical effects, are summarised. Among unsolved problems, the effects of non-spherical droplets, limitations of the ETC/ED model, effects of the interaction between droplets, effects of the moving interface due to evaporation, modelling of complex multi-component droplets, modelling of droplet heating and evaporation in near- and super-critical conditions, development of advanced kinetic and molecular dynamics models and effective approximation of the kinetic effects are discussed.