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In this study, a new method to calculate the spray collapse in multiple-hole gasoline injectors was developed. The theoretical calculation method was proposed by applying the extended spray momentum theory. In this theoretical calculation method, the deflection of the spray direction toward the injector axis was calculated serially based on the imbalance of the momentum of backward gas-flow surrounding sprays. The calculation and spray observation for validation against the calculation result were performed under conditions with and without flash boiling.

In case of electric vehicle (EV), as there are various thermal system configurations in each automotive manufacturer, suppliers should take a huge amount of time to select the best components for each OEM system. To solve this problem, a model-based development (MBD) method switching components easily and estimating their benefits efficiently is needed. In this study, the vehicle energy flow model was developed to select appropriate system configuration and components to balance cabin comfort and battery lifetime. To realize required accuracy and computing time, a 1D model, which has a motor, an air-cooling battery, a coolant circuit and heating ventilation and air-conditioning (HVAC) in a cabin, based on C-segment vehicle, was developed.

Diesel engines have smoke trade-offs with both NOx and combustion noise. Both the increment of air entrainment into the spray and deceleration of heat release rate slope which become quickly thanks to the increase of air entrainment are effective for overcoming the trade-off between smoke emission and combustion noise. In this study, effect of quick rising injection rate and pre-injection was focused as an enabler for the both. The mechanism of improvement in the trade-off caused by the quick rising injection rate and pre-injection was clarified by analyzing characteristics of spray and combustion, interaction of pre-injected spray to main-injected spray and behavior of smoke emission. Some visualization techniques were adapted to analysis of sprays and combustions. Spray momentum measurement was used for the air entrainment and mixture formation process analyzation.

The backward flow of the hot burned gas surrounding a diesel flame was found to be one of the factors dominating the set-off length (also called the lift-off length), that is, the distance from a nozzle exit into which a diffusion flame cannot intrude. In the combustion chamber of an actual diesel engine, the entrainment of the surrounding gas into a spray jet from a multi-hole nozzle is restricted by the walls and adjacent spray jets, which induces the backward flow of the surrounding gas. A new momentum theory to calculate the backward flow velocity was established by extending Wakuri's momentum theory. Shadowgraph imaging in an optical engine successfully visualized the backward flow of the hot burned gas.

In order to clarify the state of spray and mixture formation in a diesel engine cylinder, the formation technique of high temperature and high pressure conditions in a constant-volume chamber was developed. This technique reproduces actual cylinder conditions (for example, 5MPa and 873K at TDC in NA engines with a compression ratio of 16) by filling ambience formation mixture into the chamber and pre-igniting the mixture. LIEF (Laser Induced Exciplex Fluorescence) technique was applied to the analysis of vapor-liquid separation as the measurement of spray. However, the light emission from various aromatic compounds by laser irradiation makes it difficult to apply the technique to the evaluation of the actual fuel. Therefore the preparation technique of the fuel for this LIEF technique was developed to have a mixture formation state on fuel properties.

In order to clarify the diesel fuel spray characteristics inside the cylinder, we developed two novel techniques, which are preparation of same level of temperature and pressure ambient as inside cylinder and quantitative measurement of vapor concentration. The first one utilizes combustion-type constant-volume chamber (inner volume 110cc), which allows 5 MPa and 873K by igniting the pre-mixture (n-pentane and air) with two spark plugs. In the second technique, TMPD vapor concentration is measured by using Laser Induced Exciplex Fluorescence method (LIEF). The concentration is compensated by investigation of the influence of ambient pressure (from 3 to 5 MPa) and temperature (from 550 to 900 K) on TMPD fluorescence intensity. By using two techniques, we investigated the influence of nozzle hole diameter, injection pressure and ambient condition on spray characteristics.