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| Influences of Cylinder Head Structures on Flame Development in High Power Density Diesel Engines |
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| Key Words:high power density diesel engine cylinder head structure chamber shape nozzle angle nozzle deflection angle |
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| Abstract:The influence of the cylinder head structure on the combustion state of small bore diesel engines was investigated， as well as the response of chamber shape and injector arrangement to this effect. Firstly， utilizing an open-type combustion chamber， a simulation model of a 135 mm-bore diesel engine was established using closed-valve method and compensated-volume method. And the impact on flame development was compared. The response of stepped and straight combustion chamber shapes was analyzed. Injector settings with different nozzle angles and relative valve declination angles were examined. The results show that the recessed volume of the cylinder head of the small-bore diesel engine accounts for 13.1% at top dead center. With the utilization of the compensated-volume method the peak pressure decreases by 0.473 MPa， and the proportion of post-combustion is exacerbated. The response of different chamber shapes primarily affects the interference between the flame and the cylinder head， resulting in a maximum difference in thermal efficiency of 2.34%. Furthermore， as the nozzle angle increases from 140° to 150°， the difference in post-combustion decreases. Additionally， the asymmetrical arrangement of the nozzle with valves promotes the development of the flame surface， leading to a reduction in fuel consumption by 1.90 g/（kW·h）. |
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