Study Of Warship High-Power Diesel Engine's Low-Load Performance

As a prime mover of the naval ship's power plan, the low load performance of a diesel engine is a focus by us. Thus, this dissertation focuses on the operation mechanism of the high-power diesel engine's low load performance, which is improved by the double controllable intake swirl system. A sequence of theories have been analyzed and tests studied, such as the numerical value simulation of the intake system's three-dimension airstreams field; the air trimming test of steady flow of diesel engine's double intake ports; the factual examination of the diesel engine in the low load working condition and the computation of the factual combustion-heat release law. A lot of problems have been discussed, such as the flow characteristic of controllable swirl intake system, transformation rules, affect factors, and the formation and combustion-heat release law of high-power diesel engine's mixed gas effected by controllable intake swirl. This dissertation, first put forward the operation mechanism of the high-power diesel engine's low load performance improved by the double controllable intake swirl system through the theory analysis and test study. The follow are the content and creative points of the dissertation.It reviews the present study of the high-power diesel engine's low load performance, and has an overall analysis of the realistic technique and related problems in improving the high-power diesel engine's low load performance. It also brings forward a new and different technique measure of improving low load performance. That is, adopting favorite double controllable intake swirl system, which can both control high and low load performance, improves the low load performance of high-power diesel engine. The main characteristic is that in the whole load period, the controllable swirl intake system can meet the demand of engine's large flow with high load and large swirl with low load. Under low load working condition, air can be taken in from the single helical port by closing directed port. When the amount of the intake flow is much less than the double intake port, the swirl rate can remain the high level. Therefore, the process of the mixture of fuel and air can be increased, and the amount of pre-mix and combustion can be enlarged. The instable flaming can be prevented resulting from the scanty mixture gas in low load working condition in case to improve low load performance of high-power diesel engine.By adopting advanced liquid analysis software, the double-swirl-intake system, which is make up of direct and helical port, is studied in the numerical value simulation and parameter analysis of three-dimension airstreams field. The simulated calculation takes the cylinder head port of TBD620V12 diesel engine as the subject. The three-dimension substantiality is constructed on the Pro/E software platform. By employing reseau-generated tools and great non-structure tetrahedron-and-hexahedron eseau-generated tools for Ansys, the pre-process of reseau can be done,and the physics and mathematics model of diesel engine's double-controllable-intake-swirl system can be formed. According to the real condition, fix on the initial value condition for the calculation. Employing large-scale Fluent software bag, simulate the three-dimension numerical value for the intake flow of TBD620 diesel engine's double-intake port. The calculation result tends to be the same as that of steady flow test. That means the model and calculation method are effective.The steady-flow test platform is established to estimate high-power diesel engine. The steady-flow blowing test of the double-intake controllable swirl system is taken the first in China. This steady-flow test of intake system shows in double-intake port, one-direct port, or one-helical port, after the gas valve is open to a certain degree, the flux coefficient of direct port is highest, next is double-intake port, and the lowest is helical port. But the swirl rate is quite opposite. The change tendency has nothing to do with engine's load or the port's te...