Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017RG000559

Methane Feedbacks to the Global Climate System in a Warmer World

Effects of multiple-injection strategies on overall spray behavior, combustion, and emissions reduction characteristics of biodiesel fuel

Emissions from DME combustion in diesel engines and their implications on meeting future emission norms: A review

Effects of dimethyl-ether (DME) spray behavior in the cylinder on the combustion and exhaust emissions characteristics of a high speed diesel engine

Effect of n-Butane and propane on performance and emission characteristics of an SI engine operated with DME-blended LPG fuel

The Homogeneous Charge Compression Ignition (HCCI) engine has attracted much interest because it can simultaneously achieve high efficiency and low emissions. However, the ignition timing is difficult to control because this engine has no physical ignition mechanism. In addition, combustion proceeds very rapidly because the premixed mixture ignites simultaneously at multiple locations in the cylinder, making it difficult to increase the operating load. In this study, an HCCI engine was operated using blended test fuels comprised of dimethyl ether (DME) and methane, each of which have different ignition characteristics. The effects of mixing ratios and absolute quantities of the two types of fuel on the ignition timing and rapidity of combustion were investigated. Cool flame reaction behavior, which significantly influences the ignition, was also analyzed in detail on the basis of in-cylinder spectroscopic measurements. The experimental results revealed that within the range of the experimental conditions used in this study, the quantity of DME supplied substantially influenced the ignition timing, whereas there was little observed effect from the quantity of methane supplied. Spectroscopic measurements of the behavior of a substance corresponding to HCHO also indicated that the quantity of DME supplied significantly influenced the cool flame behavior. However, the rapidity of combustion could not be controlled even by varying the mixing ratios of DME and methane. It was made clear that changes in the ignition timing substantially influence the rapidity of combustion.

HCCI combustion characteristics during operation on DME and methane fuels

This paper presents an equivalent circuit model of a LIPB (Li-Ion Polymer battery) for Hybrid Electric Vehicles (HEVs) The proposed equivalent circuit can be used to predict the charging/discharging characteristics in time domain as well as the impedance characteristic analysis in frequency domain Based on these features, a one-cell model is established as a function of Depth of Discharge (DoD), and a 48-cell model for a battery pack was also established It was confirmed by experiment that the proposed model predict the discharging and impedance (AC) characteristics quite accurately at different constant current levels To check the usefulness of the proposed circuit, the model was used to simulate a motor driving circuit with an Insulated Gate Bipolar Transistor (IGBT) inverter and Brushless DC (BLDC) motor, and it is confirmed that the model can calculate the battery voltage fluctuation in time domain at different DoDs

http://www.koreascience.or.kr:80/article/JAKO201231434112058.pdf

Electric Model of Li-Ion Polymer Battery for Motor Driving Circuit in Hybrid Electric Vehicle

This paper proposes a novel electrical characterization approach for a high-performance package system using an improved Partial Element Equivalent Circuit (PEEC). As the effect of interconnects becomes a pivotal factor for the performance of high-speed electronic systems, there is a great demand for an accurate equivalent model for interconnects. In particular, an equivalent model of interconnects is established in this paper for the Fine-Pitch Ball Grid Array (FBGA) package using the improved PEEC method. Based on the equivalent model, electrical characteristics are analyzed; furthermore, these are verified through the measurement results of a Vector Network Analyzer (VNA).

Electrical Parameter Extraction of High Performance Package Using PEEC Method

In this paper, a modeling method for predicting the conducted emission with a current probe method is presented for a motor-drive braking system. The proposed model considers the motor driving circuit components and the measurement environment. The models of motor driving circuit component include PWM inverter circuits, 3-phase motor, PCB, heatsink, bus bars, and motor casing. The models of measurement environment involve the current probe, test table including ground plane, harness cable, and LISN. To reflect the accurate path of common and differential mode current of the motor drive system, co-simulation is proposed with the equivalent circuit and SPICE model. Co-simulation is eventually conducted by using EMC Studio of EMCoS Ltd. for the calculation of electromagnetic coupling around the circuit, and the high-frequency parameters of the motor driving circuit are calculated through ANSYS Inc.'s Q3D. For the model validation, the measurement and simulation results are compared, and the results of the conducted emission of those agree well in the range of 100 kHz up to 108 MHz.

Modeling of conducted EMI with current probe method for a motor-drive braking system

In this paper, a model for a prediction of conducted emission from vehicular PMSM-drive braking system is presented. The proposed model is based on the high-frequency circuit model combined with EM simulation. The parameter for high-frequency circuit modeling is derived from the measurement as well as 3D EM simulation based on FEM. To establish meaningful high-frequency parameters, the lumped parameters concerning the three-phase motor coil, motor busbar, heatsink, LISN, harness wire, meshed strap wire, and the passive-EMI filters including parasitics are either electromagnetically simulated or directly measured through an impedance analyzer. The distributed parameters of the PCB’s, connector, and motor housing are calculated via the 3D EM simulation. Eventually, the presented high-frequency parameters were integrated with PWM inverter circuit for the system-level analysis, and the model was verified through the correlation between the measurement and simulation with the EMI filters installed in the system. Moreover, the EMI characteristics with/without particular noise propagation path were analyzed in the model. The calculated conducted emission of the proposed model showed a very good agreement with the experimental data, which proves the validness of the proposed model.

June-Sang Lee

Papers

HCCI combustion characteristics during operation on DME and methane fuels

Electric Model of Li-Ion Polymer Battery for Motor Driving Circuit in Hybrid Electric Vehicle

Electrical Parameter Extraction of High Performance Package Using PEEC Method

Modeling of conducted EMI with current probe method for a motor-drive braking system

Prediction of Conducted Emission in a PMSM-Drive Braking System Using a Circuit Model Combined with EM Simulation