Norimasa Iida

Analysis of the effect of charge inhomogeneity on HCCI combustion by chemiluminescence measurement

In the HCCI Engine, inhomogeneity in fuel distribution and temperature in the pre-mixture exists microscopically, and has the possibility of affecting the ignition and combustion process. In this study, the effect of charge inhomogeneity in fuel distribution on the HCCI combustion process was investigated. Two-dimensional images of the chemiluminescence were captured by using a framing camera with an optically accessible engine in order to understand the spatial distribution of the combustion. DME was used as a test fuel. By changing a device for mixing air and fuel in the intake manifold, inhomogeneity in fuel distribution in the pre-mixture was varied. The result shows that luminescence is observed in a very short time in a large part of the combustion chamber under the homogeneous condition, while luminescence appears locally with considerable time differences under the inhomogeneous condition. It is also shown that the local luminescence durations are almost the same in both conditions.

Study of diesel spray combustion and ignition using high-pressure fuel injection and a micro-hole nozzle with a rapid compression machine: Improvement of combustion using low cetane number fuel

Abstract This study aimed to reduce NO x and soot by creating a more homogeneous lean fuel distribution in a diesel spray using high-pressure fuel injection and a micro-hole nozzle. This injection system shortened the ignition delay, but a homogeneous lean fuel distribution in the diesel spray was not achieved. Using a lower cetane number fuel, the resulting longer ignition delay made a uniform, lean fuel distribution in the diesel spray possible with this injection system. Ignition and combustion were analyzed by the combustion chamber pressure history, and flame temperatures and KL values were analyzed by the two-color method.

Premixed flame propagating into a narrow channel at a high speed, part 1: Flame behaviors in the channel

Abstract This paper deals with the transient behavior of a flame flowing into a narrow channel from a chamber filled with a propaneair mixture. The flame was observed through direct or schlieren high speed photography, and at the same time the arrival at the entrance and exit of the channel were detected by ion gaps. From the experimental results it was found that in some cases the flame extinguished or hesitated in the channel before passing through. These behaviors were dependent on the equivalence ratio of the mixture, the channel width, and the flame inflow velocity. Flame standstill in the channel is assumed to be caused by continuous quenching of hot reacting gas due to turbulent mixing with cold unburned gas at the contraction region established near the entrance of the channel. For any specific mixture, when the channel entrance is rounded or the inflow velocity is low, the minimum width of the channel for which a flame will run through without any retardation becomes smaller compared with the case of a sharp-edged entrance or a high inflow velocity. On the contrary, the minimum width of the channel for which a flame cannot pass through does not depend on the corner roundness of the channel entrance or the inflow gas velocity.

A Study of High Combustion Efficiency and Low CO Emission in a Natural Gas HCCI Engine

The operating range is restricted by knocking and misfiring in a homogeneous charge compression ignition (HCCI) engine. In an HCCI engine, the autoignition does not always mean the high combustion efficiency because the operating range to achieve high combustion efficiency is very narrowly restricted by knocking and high THC, CO emissions. In this study, we have investigated the operating conditions to achieve high combustion efficiency and low CO emission in a four-stroke HCCI engine using experimental analysis and elementary reactions calculation. It is shown that the combustion efficiency reaches higher than 90%, and the CO emission can be reduced considerably when the in-cylinder maximum gas temperature is over 1600K.

Experimental study on HCCI combustion characteristics of n-heptane and iso-octane fuel/air mixture by the use of a rapid compression machine

The HCCI engines have been known with high efficiency and low pollution and can be actualized as the new internal combustion engines. However, As for(??) the ignition and combustion depend strongly on the oxidation reaction of the fuel, so it is difficult to control auto-ignition timing and combustion duration. Purpose of this paper is creating the database for development of multi-dimensional simulation and investigating the influence of different molecular structure. In this research, the effect of n-heptane mole ratio in fuel (XnH) on the ignition delay from homogeneous charge compression ignition(HCCI) has been investigated experimentally. By varying the XnH, it was possible to ascertain whether or not XnH is the main resource of ignition delay. Additionally, the information on equivalence ratio for varying XnH was obtained. The tests were performed on a RCM (Rapid Compression Machine) fueled with n-heptane and iso-octane. The results showed that decreasing XnH (100, 30, 20, 10,0), the ignition delays of low temperature reaction (tL) and high temperature reaction (tH) is longer. And the temperature of reaction increases by about 30K. n-heptane partial equivalence ratio (fnH) affect on tL.and TL. When nH was increased as a certain value, tL was decreased and TL was increased.

Self-ignition and combustion stability in a methanol fueled low heat rejection ceramic ATAC engine—analysis of cyclic variation at high wall temperatures and lean burn operation

Abstract ATAC (Active Thermo-Atmosphere Combustion) is stable at its lean limit because it is bulk-like and non-propagating in nature and is initiated by self-ignition. A low heat rejection methanol-fueled engine was used to investigate the influence of making the fuel-air ratio leaner and increasing the combustion chamber wall temperature on cyclic variation of ATAC ignition and combustion. The cyclic variation of self-ignition timing, combustion duration, total heat release, and instantaneous wall heat flux was analyzed, from which correlations between self-ignition timing and combustion duration, self-ignition timing and total heat release, and combustion duration and total heat release were obtained.

Diesel combustion model for on-board application

Diesel engines exhibit highly efficient, environmentally sound performance under good operational control; however, because of the demand of controlling multiple actuators under various environmental conditions, the conventional experimental method for controlling diesel engines has become increasingly difficult. Therefore, diesel combustion models with less calculation loads were ultimately developed with the aim of implementing such model-based controllers for engine control unit in the future. To achieve the on-board application of the diesel combustion model, the in-cylinder state of a single cycle was discretized into several representative phases such as a valve-opening and valve-closing phase, ignition phase, and maximum pressure phase. Temperature and oxygen quantities in residual gas were considered as the state variables of the system because they have a critical effect on combustion and induce cyclic coupling. The model could take account of the effect of actuators in diesel engines, and the states in each phase were calculated by fundamental thermodynamic equations and some empirical equations. The model was validated against experimental results and had a good agreement with in-cylinder pressures and temperatures at each phase. In addition, the calculation times of the model were confirmed to be capable of on-board application. Furthermore, as a demonstrative example and to show the added value of the model, it was used to synthesize controllers to enable multi-input/multi-output control of a diesel engine in simulation.

A study for generating power on operating parameters of powerpack utilizing linear engine

2 Korea institute of Energy Research, 152 Gajeong street, Yuseong-gu, daejun, 305-343, Korea Abstract >> The research shows the experiment results according to the combustion characteristics and configuration of the linear generator of powerpack for the generating power applying the 2-stroke compact linear engine. The powerpack used in this paper consists of 2-stroke linear engine, linear generator and air compressor parts. For identifying the combustion characteristics and generating power of linear engine, some parameters were varied sucha as electric load, fuel input calorie, spark timing delay and equivalence ratio. Also generating power was confirmed at each operation conditions, when the air gap length of linear generator part was changed as each 1.0 mm and 2.0 mm. During the all operations, intake air was inputted under the wide open throttle. Mass flow rate of air and fuel was changed using mass flow controller, after these were premixed by premixture device, and then premixed gas was supplied directly into each cylinder. As a result, piston frequency and combustion characteristics were different at each conditions according to parameters affecting the combustion such as fuel input calorie, resistive load, spark timing delay and equivalence ratio. Consequently, these had an effect on generating power.

Study on auto-ignition and combustion mechanism of HCCI engine

In the HCCI (Homogeneous Charge Compression Ignition) engine, a mixture of fuel and air is supplied to the cylinder and auto-ignition occurs resulting from compression. This method can expand the lean flammability limit, realizing smokeless combustion and also having the potential for realizing low NOx and high efficiency. The optimal ignition timing is necessary in order to keep high thermal efficiency. The Ignition in the HCCI engine largely depends on the chemical reaction between the fuel and the oxidizer. Physical methods in conventional engines cannot control it, so a chemical method is demanded. Combustion duration is maintained properly to avoid knocking. In addition, the amount of HC and CO emissions must be reduced. The objective of this study is to clarify the following through calculations with detailed chemical reactions and through experiment with the 2-stroke HCCI engine: the chemical reaction mechanism, and HC and CO emission mechanisms. Ignition and combustion mechanisms and the effect of pre-mixture heterogeneity on ignition and combustion are also clarified. This is done by using an optically accessible engine and measuring the luminescence at auto-ignition and during the combustion process.

Influence of the fuel compositions on the homogeneous charge compression ignition combustion

Abstract Homogeneous charge compression ignition (HCCI) engines are drawing attention as the next-generation internal combustion engine, but have not been put to practical use because of several issues. One of the issues is that increasing the fuel charge causes rapid combustion in the combustion chamber, which results in knocking that limits its operation region. In this study, the focus was put on a method to increase the operation region of HCCI engines by mixing two fuels with different reactivities. First, dimethyl ether (DME), n-butane, or hydrogen was mixed with methane to investigate how the changes in mixing ratios affected the oxidation reaction of the pre-mixture based on numerical calculations with elementary reactions. From the calculation results, applicable types of double componential fuels for HCCI engines were considered. Based on the results of the consideration, DME or n-butane was mixed with methane to conduct combustion experiments and to clarify mixing conditions of the double componential fuels that realize high output and high thermal efficiency simultaneously.