Takemi Chikahisa

Description and Analysis of Diesel Engine Rate of Combustion and Performance Using Wiebe's Functions

Two laboratory engines, one direct injection and one indirect injection, were operated for a range of speeds, loads, injection timings, fuels, and steady and transient conditions. Rate of combustion data were derived and analyzed using a double Wiebes function approximation. It is shown that three of the six function parameters are constant for a wide range of conditions and that the other three can be expressed as linear functions of the amount of fuel injected during ignition lag. Engine noise, smoke, and thermal efficiency correlate with the parameters describing the amount of premixed combustion and diffusive combustion duration. These characteristics may be optimized by reducing the quantity of premixed combustion while maintaining the duration of diffusive combustion to less than 60 /sup 0/CA.

Low carbon flower buildup, low smoke, and efficient diesel operation with vegetable oils by conversion to mono-esters and blending with diesel oil or alcohols

The purpose of this investigation is to evaluate the feasibility of rapeseed oil and palm oil for diesel fuel substitution in a naturally aspirated DI Diesel engine is evaluated. Means to reduce the carbon deposit buildup in vegetable oil combustion is found. In the experiments, the engine performance, exhaust gas emissions, and carbon deposits are measured for a number of fuels: rapeseed oil, palm oil, methylester of rapeseed oil, and these fuels blended with ethanol or diesel fuel with different fuel temperatures. Both of the vegetable oil fuels generate an acceptable engine performance and exhaust gas emission levels for short term operation, but they cause carbon deposit buildups and sticking of piston rings after extended operation. Practical solutions to overcome the problems are: increasing the fuel temperature to over 200/sup 0/C, blending 25 vol % diesel fuel in the vegetable oil, blending 20 vol % ethanol in the fuel, or converting the vegetable oils into methylesters.

Performance and durability of Pt-MFI zeolite catalyst for selective reduction of nitrogen monoxide in actual diesel engine exhaust

Abstract Selective catalytic reduction of nitrogen monoxide (NO) by hydrocarbon in an oxidizing atmosphere has been studied over platinum-MFI zeolite (Pt-MFI) in synthesized or actual diesel engine exhaust gases. The activity of Pt-MFI in the synthesized gas, containing 10% water, changed in the early stage of the use, leveled off after 150–200 h, and remained constant for more than 800 h. The Pt-MFI catalyst also showed stable activity at 423–773 K and 10 000–150 000 h − (gas hourly space velocity) in actual engine exhaust with light oil as a fuel. The degree of nitrogen monoxide reduction increased linearly upon addition of ethylene into the exhaust gas.

Effects of Cathode Catalyst Layer Structure and Properties Dominating Polymer Electrolyte Fuel Cell Performance

Title Effects of Cathode Catalyst Layer Structure and Properties Dominating Polymer Electrolyte Fuel Cell Performance Author(s) Tabe, Yutaka; Nishino, Masayoshi; Takamatsu, Hiroyuki; Chikahisa, Takemi Citation Journal of the Electrochemical Society, 158(10), B1246-B1254 https://doi.org/10.1149/1.3624606 Issue Date 2011-08-12 Doc URL http://hdl.handle.net/2115/47104 Rights

Performance of a methanol reforming system for a fuel cell powered vehicle and system evaluation of a PEFC system

Abstract The fuel cell is an environmentally-friendly power source due to high efficiency and cleanness. Considering safety, tractability and infrastructure, a methanol reformer is a candidate for the supply of hydrogen to fuel cell vehicles. However as CO generated by methanol reformers poisons the platinum catalysts of anodes, the operating conditions were studied in order to minimize the CO emissions from the reforming system. This study tested a methanol reforming system including a steam reformer and preferential oxidizer, established the chemical reaction rates of reforming and CO oxidation and calculated the dynamic changes in CO concentration from the reformer using a newly developed simulator.

NOx reduction characteristics of Pt-ZSM-5 catalyst with diesel engine exhaust

The platinum ion-exchanged ZSM-5 zeolite catalyst (Pt-5), which reduces nitrogen oxides (NOx) in the presence of oxygen and hydrocarbons, was applied to actual diesel engine exhaust. Compared to the Cooper ion-exchanged ZSM-5 zeolite catalyst, the Pt-Z had higher NOx reduction efficiency, ηNOx = 33%, and lower activation temperature, 250°C, in normal engine operation. It was found that water in the exhaust gas did not apparently affect the NOx reduction, while the reduction efficiency was significantly affected by the aspect ratio of the catalyst reactor and by the shape of the catalyst, i.e. pellet or honeycomb.

Measurement of Water Production Behavior, Temperature, and Current Density Distributions in a Polymer Electrolyte Fuel Cell

This paper observes phenomena related to water production behavior inside a fuel cell and analyzes the effect on the current and temperature distribution across the reaction area. A fuel cell permitting direct observation of the phenomena in the cell, 2-D temperature measurements in the cathode channels, and local current density measurements on the anode side was manufactured. The experimental results showed the production and flow of liquid water in the cell, and there were good correlations among the distributions of current density, temperature, and water amounts in the channels. The behavior of current, voltage, water distribution, and pressure differences in the cathode channels were used to hypothesize about the possibility of gas paths deep in the gas diffusion layer in the flooded condition and a positive feedback mechanism in the drying-out condition.© 2006 ASME

Improvement of performance and emissions of a compression ignition methanol engine with dimethyl ether

Dimethyl ether (DME) has very good compression ignition characteristics and can be converted from methanol using a {gamma}-alumina catalyst. In this study a torch ignition chamber (TIC) head with TIC close to the center of the main combustion chamber was designed for the TIC method. The possibility of improvements in reducing the quantities of DME and emission were investigated by optimizing the TIC position, methanol injection timing, DME injection timing, and intake and exhaust throttling. It was found that the necessary amount of DME was greatly reduced when optimizing methanol and DME injection timings. 2 refs., 16 figs., 1 tab.

Achievement of stable and clean combustion over a wide operating range in a spark-assisted IDI diesel engine with neat ethanol

Spark-assisted diesel engines operated with alcohol fuels usually display misfiring or knocking problems. This paper presents an analysis of the factors influencing the ignition characteristics of ethanol in a swirl chamber diesel engine with a multi-spark ignitor. In the experiments, cycle-to-cycle combustion variations and the degree of knocking were investigated by changing engine parameters over a wide operating range. The results of the investigations showed that stable ignition and smooth combustion is achieved when a flammable mixture is formed in the vicinity of the spark plug when only a small amount of the injected fuel has evaporated. By optimizing the design factors, operation with high efficiency and low exhaust emissions was achieved.

Microscopic Observation of Freezing Phenomena in PEM Fuel Cell at Cold Start

In Polymer electrolyte membrane fuel cells (PEMFCs) below zero, the freezing of product water induces the extreme deterioration of cell performance. This phenomenon is serious problem in cold regions and is needed to be solved to achieve the practical use of PEMFC. In this study, we investigate ice distribution in the catalyst layer (CL) and gas diffusion layer (GDL) using an optical microscope and a CRYO-SEM to clarify the freezing mechanism. The effects of the start-up condition such as the current density on the ice distribution and cell performance in a fuel cell are discussed.