Search Results

For improving the thermal efficiency and the reduction of hazardous gas emission from IC engines, it is crucial to model the heat transfer phenomenon starting from the intake system and predict the intake air’s mass and temperature as precise as possible. Previously, an empirical equation was constructed using an experimental setup of an intake port model of an ICE, in order to be implemented into an engine control unit and numerical simulation software for heat transfer calculations. The empirical equation was based on the conventional Colburn analogy with the addition of Graetz and Strouhal numbers. Introduced dimensionless numbers were used to characterize the entrance region, and intermittent flow effects, respectively.

This paper provides the importance of helical coil sub-cooled condenser which has a compact structure, large heat transfer area, and high heat transfer capability in comparison to the straight sub-cooled condenser in the automobile vehicle. The HVAC unit has the largest parasitic load on the engine. Hence, by improving the coefficient of performance of the air-conditioning (A/C) system, the reduction in vehicule emissions is possible. Previous studies explain that there is generation of secondary flow inside the fluid in the circular cross-section of the helical coil. By using the effect of the secondary flow generation, authors tried to enhance the heat transfer rate as it leads to heterogeneous temperature distribution across the periphery of the tube and causes a higher heat transfer. For the purpose of the study, a prototype with a square cross-sectional 2.7 mm × 2.7 mm channel with flat fins towards the outer side has been constructed.

Diesel engines need to optimize the fuel injection timing and quantity of each cycle in the transient operation to increase the thermal efficiency and reduce the exhaust gas emissions through the precise combustion control. The heat transfer from the working gas in the combustion chamber to the chamber wall is a crucial factor to predict the gas temperature in the combustion chamber to optimize the timing and quantity of fuel injection. Therefore, the authors developed both the heat loss and the polytropic index prediction models with the low calculation load and high accuracy. In addition, for the calculation of the heat loss and the polytropic index, the wall heat transfer model was also developed, which was derived from the continuity equation and the energy equation. The present study used a single cylinder diesel engine under the condition of engine speed of 1200 and 1500 rpm, and measured the local wall temperature and the local heat flux of the combustion chamber.

Attribute to high heat transfer rate and less complexity, the Helical coil sub-cooled condenser (HCSCC) can provide the most innovative and unique application for the air conditioning system. In the case of automobiles, reduction in air-conditioning load may diminish the vehicular emission, and power consumption as the air-conditioning load is the most power-consuming components after the engine load. Moreover, to solve the problem, we focus on the helical type heat exchanger. It may play a vital role in reducing the weight and increase the performance of the small engine because of the compact structure and lighter weight. The compressor unit is the most vital component of the refrigeration cycle, but the condenser unit is also one of the most critical devices, and the author tried to reduce the power consumption by enhancing the performance of the condenser.

This paper oriented towards spiral coil sub-cooled condenser (SCSCC) which is used for the automotive air conditioning system. Therefore, the effect of curvature diameter has been carefully measured by CFD as it reduces/intensify the centrifugal force. This centrifugal force is responsible for Dean vortices and leads to the generation of secondary flow inside the refrigerant. By taking advantage of this secondary flow, the performance of the SCSCC can be improved. CFD analysis comprises curvature diameter from 13mm to 110mm, which varied the Dean number from 7577 to 2605. The author tried to evaluate the complicated phenomena that occurred within the SCSCC. However, the turbulent kinetic energy which is one of the critical factors of heat transfer coefficient illustrates 0.009m2/s2 and 0.006m2/s2 for large and small Dean number, respectively, toward the outer side of the channel.

Diesel engine has fuel combustion capability in various high density oil such as residual fuels or biofuels derived from fossil or living matter. But for commercial use, these fuels except bio diesel fuel (BDF) should be heated, separated and filtered by equipment and dosed or mixed with additive or distillate oil etc. before being supplied to the engine in order to improve combustibility. This study aims to illuminate fuel characteristic of blend contained woody pyrolysis oil (WPO) which is high viscosity and incombustible, and dimethyl ether (DME) whose emission of combustion has no soot particle. This paper describes thermo-physical property of neat WPO and the blend on the basis of the evaluation of fuel fluidity by measurement and calculation of viscosity. According to the result, it was confirmed that the fluidity of WPO was improved by mixing DME and the approximate viscosity expressions at any temperature of WPO and the blend were good accuracy.

This paper discusses the compact structure, innovative and unique approach of high performance spiral coil sub-cooled condenser for compact power plant/engine applications. The motivation behind this study is to reduce the engine emission by improving the coefficient of performance for air-conditioning unit. Since the air conditioning system is the most power consumption units after the power plant, so it significantly affects the fuel consumption and the hazardous gas emissions. In the air condition cycle, the condenser unit is addressed as one of the important devices, and thus, the author tried to reduce the energy consumption by improving the performance of the condenser. The most advantage points of this study is to use spiral coil sub-cooled condenser, which elaborates the effect of secondary flow generation inside the fluid and is known as the Dean’s effect.

An empirical equation was developed for modeling the heat transfer phenomena taking place in an intake manifold which included the backflow gas effect. In literature, heat transfer phenomenon at intake system is modeled based on steady flow assumptions by Colburn analogy. Previously, authors developed an equation with the introduction of Graetz and Strouhal numbers, using a port model experimental setup. In this study, to further improve the empirical equation, real engine experiments were conducted where pressure ratio between the intake manifold and engine cylinder were added along with Reynolds number to characterize the backflow gas effect on intake air temperature. Compared to the experimental data, maximum and average errors of intake air temperature estimated from the new empirical equation were found to be 2.9% and 0.9%, respectively.

In the past two decades, internal combustion engines have been required to improve their thermal efficiency in order to limit hazardous gas emissions. For further improvement of the thermal efficiency, it is required to predict the mass of intake air into cylinders in order to control the auto-ignition timing for CI engines. For an accurate prediction of intake air mass, it is necessary to model the heat transfer phenomena at the intake manifold. From this intention, an empirical equation was developed based on Colburn equation. Two new arguments were presented in the derived formula. The first argument was the addition of Graetz number, where it characterized the entrance region thermal boundary layer development and its effect on the heat transfer inside the intake manifold. As the second argument, Strouhal number was included in order to represent intake valve effect on heat transfer.

For further development of the thermal efficiency of SI engines, the robust control of the air-fuel ratio (A/F) fluctuation is one of the most important technologies, because the A/F is maintained at the theoretical constant value, which causes the increase of the catalytic conversion efficiency and the reduction of pollutant emission. We developed the robust controller of the A/F, which is the method to change the fuel injection rate by using the feed-forward (FF) controller considering the heat transfer at the intake system. The FF controller was verified under transient driving conditions for a single cylinder, and the A/F fluctuations were reduced at approximately 84%.

The experiments were done in order to obtain the fundamental information that would be needed to build a physical model which expresses the heat transfer phenomena in the intake port model and manifold. In the experiments, the heating conditions and the period of the cyclic change of the gas velocity were changed as experimental parameters. In addition to those parameters, the Strouhal number was applied to express oscillating flow. As a result, the heat transfer in the experiments became clear, and the equations were obtained to show the Nusselt number using the Reynolds number, the Graetz number and the Strouhal number.

Temperature measurement experiments with intake port model were done to achieve the fundamental information on constructing physical model that expresses the heat transfer phenomena in the intake manifold and intake port. The experiments were done with steady airflow, and the size, shape, heating condition of the port model and mass flow rate were changed as experimental parameters. As the results, it was clear that the developing condition of velocity and thermal boundary layer had greater influence than the shape factor, and the coefficient and the exponent of the equation derived from the relationship between Nusselt number and Reynolds number had great difference from those of generally used Colburn's equation in undeveloped entrance region, but they got closer as developing boundary layer.

The electronic controlled carburetor and ignition system has been developed. In accordance with various working conditions of the engine, the system adjusted corresponding control parameters; air fuel ratio and ignition timing, therefore it could keep the engine working on the optimal conditions. Through analyzing overall performance of the engine based on the experimental data, we had concluded that the specific fuel consumption was improved about 8-10%, and the exhaust emission performance was improved correspondingly after electronic control, the improved ratio was about 10% for HC emission and 97% for CO emission.

In the 17th century, Christiaan Huygens invented the first engine to save the labor, which is humanism. Nowadays, both gasoline (SI) and diesel (CI) engines hold the definite position as the prime mover of the current surface transport vehicles due to their superior power, energy density, and fuel economy. Although these engines give exceeding convenience to human life, they also have become the vanguard of environmental disruption. From this viewpoint, the author has tried to give a historical review and perspective on engine developments. Although it is said that further emission controls in CI engines are quite difficult, recent research work and prediction for both lower emissions and better fuel economy are discussed. It is concluded that CI engines will co-exist with SI engines in the future, part of which will be used in hybrid systems. Fuel cells will be widely utilized, and hydrogen internal combustion engines would be expected as well.

This investigation was concerned with the rate of heat transfer from the working gases to the combustion chamber walls of the internal combustion engines. The numerical formula for estimating the heat transfer to the combustion chamber wall was derived from the theoretical analysis and the experiment, which were used the constant volume combustion chamber and the actual gasoline engine. As a result, mean heat transfer in the internal combustion engine becomes possible to estimate with measuring the cylinder pressure. In addition, the derived numerical formula forms with quite simple variables. Therefore it is very useful for engine design.

Historically the high speed diesel engine for commercial vehicles has been developed along with its combustion system in compliance with political and economical changes. After the 1970's, stricter exhaust emission regulations and fuel economy requirements induced combustion developments and application of turbocharged and inter cooled engines. From the late 1980's, high pressure fuel injection has been investigated and recognized as an essential tool for lowering emissions especially of particulate matter. Although turbulence effects on both in-cylinder air motion and during the combustion process are quite effective, they show different phenomena in conventional and advanced high pressure fuel injection systems. In the 1990's, multiple injection with high pressure has been attempted for further reduction of NOx and particulate matter.

This book examines the development of the engine from a historical perspective. Originally published in Japanese, The Romance of Engines' English translation offers readers insight into lessons learned throughout the engine's history. This book belongs on the bookshelves of all engine designers, engine enthusiasts, and automotive historians. Topics covered include: Newcomen's Steam Engine The Watt Steam Engine Internal Combustion Engine Nicolaus August Otto and His Engine Sadi Carnot and the Adiabatic Engine Radial Engines; Piston and Cylinder Problems Engine Life Problem of Cooling Engine Compartments Knocking; Energy Conservation Bugatti; Volkswagon Rolls Royce Packard Daimler-Benz DB601 Engine and more!

A new concept for diesel combustion was investigated by means of numerical simulation, engine experiment, and combustion observation in order to realize a simultaneous reduction of NOx and particulate emission. This concept (HiMICS: Homogeneous charge intelligent Multiple Injection Combustion System) is based on pre-mixed compression ignition combustion combined with multiple injection. Combustion characteristics of HiMICS concept was investigated by comparing with both a standard single injection and a pilot injection. In HiMICS concept, the pre-mixture is formed by a preliminary injection performed during a period from the early stage of the induction stroke to the middle stage of the compression stroke. Modified KIVA-II code was used to predict engine performances and emissions of each injection method. The simulation results show a capability of considerable improvement in the trade-off relation between NOx emissions and fuel consumption of HiMICS.

In order to reduce particulate and NOx emission from the direct injection diesel engine, most researchers have been expecting the utilization of higher injection pressure and injection rate for improvement of diesel combustion. In the case of pump-line-nozzle system, the injection pipe line is very important with regard to the high injection pressure. Namely, the pipe line must be able to resist not only high pressure but also cavitation erosion. In this paper, the effect of high injection pressure, injection rate and sharp cutting at the end of fuel injection are discussed along with cavitation phenomena on the injection pipe line. And durability tests on the pipe line system under high injection pressure using a test rig are also described. Regarding durability tests, several measures have been taken for the injection pipe. As a result, the authors have found that the best solution for the injection pipe is a composite pipe made with SUS and steel.

A current unmodified and modified engines with different amounts of thermal insulation have been used to generate data from which changes in bsfc, cooling loss, emissions, exhaust loss were determined. Since legislative requirement exists for allowable emission of NOx, fuel injection timing and other controllable factors were adjusted to maintain constant NOx emission except a test of influence on NOx emission according to the rate of heat insulation (adiabaticity). The effect of higher combustion temperature on the combustion phenomena is discussed.