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Technical Paper

Development of High Performance Radiators by Fin Optimization

Requirements for fuel economy improvement and reduction in the vehicles engine compartment have increased significantly in the pass years. Performances in radiators have driven changes in terms of compactness and weight reductions. By focusing on the air flow we have optimized the radiator fin and developed a high performance radiator. A similar performance was achieved using an 11mm core depth which has 30% weight reduction compared to a 16mm core depth. The purpose of this paper is to present a technical outline about fin optimization.
Technical Paper

Reduction of the BPF Noise Radiated from an Engine Cooling Fan

This study investigates the reduction of the Blade Passing Frequency (BPF) noise radiated from an automotive engine cooling fans, especially in case of the fan with an eccentric shroud. In recent years, with the increase of HV and EV, noise reduction demand been increased. Therefore it is necessary to reduce engine cooling fan noise. In addition, as a vehicle trend, engine rooms have diminished due to expansion of passenger rooms. As a result, since the space for engine cooling fans need to be small. In this situation, shroud shapes have become complicated and non-axial symmetric (eccentric). Generally, the noise of fan with an eccentric shroud becomes worse especially for BPF noise. So it is necessary to reduce the fan BPF noise. The purposes of this paper is to find sound sources of the BPF noise by measuring sound intensity and to analyze the flow structure around the blade by Computational Fluid Dynamics (CFD).
Technical Paper

Study of Cooling Drag Reduction Method by Controlling Cooling Flow

As the demand for improved fuel economy increases and new CO2 regulations have been issued, aerodynamic drag reduction has become more critical. One of the important factors to consider is cooling drag. One way to reduce cooling drag is to decrease the air flow volume through the front grille, but this has an undesirable impact on cooling performance as well as component heat load in the under-hood area. For this reason, cooling drag reduction methods while keeping reliability, cooling performance and component heat management were investigated in this study. At first, air flow volume reduction at high speed was studied, where aerodynamic drag has the greatest influence. For vehicles sold in the USA, cooling specification tends to be determined based on low speed, while towing or driving up mountain roads, and therefore, there may be extra cooling capacity under high speed conditions.
Technical Paper

The Humidity Control System Applied to Reduce Ventilation Heat Loss of HVAC Systems

Vehicles have been more required to save energy against the background of the tendency of ecology. As the result of improving efficiency of internal combustion engines and adoption of electric power train, heat loss from engine coolant, which is used to heat the cabin, decreases and consequently additional energy may be consumed to maintain thermal comfort in the passenger compartment in winter. This paper is concerned with the humidity control system that realizes reduction of ventilation heat loss by controlling recirculation rate of the HVAC system by using highly accurate humidity sensor to evaluate risk of fogging on the windshield. As the results of the control, fuel consumption of hybrid vehicles decreases and maximum range of electric vehicles increases.
Technical Paper

Analysis of the Fuel Liquid Film Thickness of a Port Fuel Injection Engine

In this paper, the authors have developed a new measuring method of the liquid fuel film thickness on walls, such as intake ports, the combustion chamber and cylinder liner of a Port Fuel Injection (PFI) engine, and clarified the fuel film behavior under various running conditions when Fiber-based Laser-Induced Fluorescence (Fiber-based LIF) was applied to the newly developed method. The thickness of the fuel film is measured by detecting the intensity of fluorescence from the film that is irradiated by a He-Cd laser. A single optical fiber is used to simultaneously transmit the laser beam and the fluorescence from the film. In addition, the S/N ratio of the fluorescence is improved by using a He-Cd laser of which the wavelength (λ=442nm) is able to efficiently irradiate test fuel doped 2-3-butandione. Using this method, the fuel film thickness on the wall of the PFI engine was analyzed in two case studies.
Technical Paper

Effects of Fuel Properties on SIDI Fuel Injector Deposit

The tendency of spark ignition direct injection (SIDI) engines to form injector deposits was investigated using engine dynamometer tests on a SIDI engine equipped with fan spray type injectors. Fifteen test fuels with varying 90% distillation temperature (T90), aromatics, olefins, oxygenates and sulfur levels were prepared to identify the effects of fuel properties on injector deposits. The results suggested that not only the T90 but also the number of alkyl substituent of aromatics had effects on injector deposit formation. Effects of detergents on the injector deposit cleanliness were also evaluated in this study.
Technical Paper

Numerical Study of Mixture Formation and Combustion Processes in a Direct Injection Gasoline Engine with Fan-Shaped Spray

Numerical 3-D simulations are performed for the improvement of the new direct injection gasoline engine. A solution based local grid refinement method has been developed in order to reduce the CPU time. This method has been incorporated into the CFD program (STAR-CD) with in-house spray and combustion models. Calculation results were compared with the experimental data taken by the LIF technique, and good agreement was obtained for the mixture formation and combustion processes. Some calculations were carried out for the fuel-air mixture formation process during late injection stratified combustion and the following results were obtained. The unburnt fuel has a tendency to remain in the side of the piston cavity at the latter part of the combustion period. To reduce the amount of unburnt fuel, it was shown that the combination of a thin thickness fan spray and compact cavity forms a spherical mixture, suitable for combustion.
Technical Paper

Development of the Electronically Controlled Hydraulic Cooling Fan System

A new engine cooling fan system has been developed, in which the fan is driven by a hydraulic pump and motor and controlled electronically by a computer. By utilizing the hydrostatic power under precise control, the fan generates not only high airflow volume but also optimum flow rate for the various engine conditions. Also in this system, a relatively high efficiency is gained because the clearance between the tip of the fan blade and a shroud designed to be short, thanks to the installation of the fan on the radiator. As the result of these functions, the following features have been obtained which are superior to conventional fan systems like a engine-driven fan with fluid coupling or an electric-motor fan. (1) Reduced fan noise (2) Improved fuel economy (3) Small size and light weight
Technical Paper

Waste Heat Recovery of Passenger Car Using a Combination of Rankine Bottoming Cycle and Evaporative Engine Cooling System

Rankine bottoming system, which operates on waste heat of engine cooling, has been developped to improve the fuel economy of a passenger car. Evaporative engine cooling system is utilized to obtain high thermal efficiency and simplicity of the Rankine bottoming system. The bottoming system uses HCFC123 as a working fluid, and scroll expander as a power conversion unit. The results indicate that energy recovery, which depends on the ambient temperature, is almost 3 percent of engine output power at ambient temperature of 25°C.
Technical Paper

Development of Vehicle Air Conditioners for the Refrigerant HFC-134a

Concerns on environmental protection are being intensified throughout the world in recent years. Of those concerns, depletion of the ozone layer in the atomosphere caused by CFC emission into the atomosphere is the target of serious concern as shown in Fig. 1. At present, the use of CFC production is restricted by regulations at the global level, and CFC will be phased out by the end of 1995. In this regard, the authors have developed a new vehicle air conditioner to adapt to a new refrigerant HFC-134a, which is gentle to the ozone layer, and to replace CFC-12. The new refrigerant system was introduced to the market in October, 1991, and the replacement will be almost completed by the end of 1993 for the Lexus and Toyota production vehicles. This paper describes the development of the new compressor lubricant, seal rubber, hose and desiccant by taking into consideration the materials concerned and the number of technological issues involved in the new refrigerant, HFC-134a.
Technical Paper

Experimental Analysis for the Improvement of Radiator Cooling Air Intake and Discharge

EXPERIMENTAL ANALYSIS for the increase of the radiator cooling air has been performed with special attention to the utilization of air pressure in high-speed running conditions. Measurements of pressure distributions at the radiator cooling air intake showed that the prevention of the occurrence of separations around the bumper is the efficient method to increase the cooling air. Furthermore, the optimum configuration for the radiator cooling air discharge has also been experimentally studied using a simplified model which simulates the under part of the engine compartment. These improvements made the vehicle radiator cooling air volume increase 14% under high-speed running conditions.
Technical Paper

Study of Anti-Corrosive Property of Engine Coolant for Aluminum Cylinder Heads

Recently, use of aluminum engine parts has increased for fuel economy and power improvements. Aluminum cylinder heads, for example, are currently used in most engines. But, only low performance engine coolants are available for prevention of heat-transfer corrosion of aluminum cylinder heads. The authors have studied a laboratory test method that is able to accurately evaluate the performance of engine coolants for prevention of aluminum cylinder head corrosion. And we have developed the new test method by changing the test specimen temperature higher and the engine coolant temperature lower than the ASTM D4340 test. The new test has been confirmed engine bench test. We evaluated further the performance of many engine coolants of the world for prevention of aluminum cylinder head corrosion using the new test. We have known that there were a lot of poor performance engine coolants in the world.
Technical Paper

Prediction of the Airflow Through Automotive Radiators Using 3-Dimensional Analysis

Air flow around a car front end configuration and through the radiator and condenser was computed simultaneously. Although the engine compartment was simplified to reduce computational cost, comparison of experimental data with the analysis showed excellent prediction of the air flow through the radiator and condenser.
Technical Paper

The New Toyota Inline 4-Cylinder 2.5L Gasoline Engine

In order to adapt to energy security and the changes of global-scale environment, further improvement of fuel economy and adaptation to each country’s severer exhaust gas emission regulation are required in an automotive engine. To achieve higher power performance with lower fuel consumption, the engine’s basic internal design such as an engine block and cylinder head were changed and the combustion speed was dramatically increased. Consequently, stroke-bore ratio and valve layout were optimized. Also, both flow coefficient and intake tumble ratio port were improved by adopting a laser cladded valve seat. In addition, several new technologies were adopted. The Atkinson cycle using a new Electrical VVT (Variable Valve Timing) and new combustion technology adopting new multi-hole type Direct fuel Injector (DI) improved engine power and fuel economy and reduced exhaust emissions.
Journal Article

Proper Orthogonal Decomposition Analysis of Flow Structures Generated around Engine Cooling Fan

A cooling fan is one of the primary components affecting the cooling performance of an engine cooling system. In recent years, with the increase in electric vehicles (EVs) and hybrid vehicles (HVs), the cooling performance and noise level of the cooling fan have become very important. Thus, the development of a low-noise fan with the same cooling performance is urgently required. To address this issue, it is critical to find the relation between the performance of the fan and the flow structures generated around it, which is discussed in the present paper. Specifically, a computational method is employed that uses unsteady Reynolds-averaged Navier-Stokes (URANS) coupling with a sliding mesh (SLM). Measurements of the P-Q (Pressure gain-Flow rate) characteristics are performed to validate the predictive accuracy of the simulation.