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| Experimental Study on the Performance Optimization of A Diesel Pilot Ignited Natural Gas Engine Under Medium and High Loads |
| DOI：10.13949/j.cnki.nrjgc.2023.06.005 |
| Key Words:diesel pilot ignited natural gas multi-parameter thermal efficiency minimum diesel mass |
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| Abstract:Based on the single-cylinder engine test platform modified by Weichai WP10H， the coupling relationship between thermodynamic parameters and diesel injection parameters under medium and high load operating conditions and the control method to obtain high thermal efficiency were studied in depth. The results show that under medium load conditions that the indicated mean effective pressure（IMEP） is 1.0 MPa， the diesel injection timing is advanced to reduce the diesel mass. And with the increase of premixed natural gas equivalent ratio， the diesel injection timing is delayed and its sensitivity to the variation of diesel mass is reduced. In addition， the minimum diesel mass corresponding to the indicated thermal efficiency and combustion rate approximating the maximum value is decreased. Research shows that the increase in exhaust gas recirculation（EGR） rate will not only advance the diesel injection timing， but also make the diesel mass increase with IMEP=1.4 MPa. And the boost will cause two effects. One is to reduce the equivalent ratio to slow down the combustion rate， and the other is to increase the compression temperature， which is conducive to achieving rapid compression ignition. The combined effect depends on the thermodynamic atmosphere of the mixture itself. Under medium load conditions， the control of diesel injection parameters need to enhance the combustion rate as much as possible to reduce combustion losses， and the existence of the best equivalent ratio can regulate the combustion phase， thus achieving the energy balance between heat transfer and exhaust losses， which is the key to optimizing thermal efficiency. Besides， in the case of meeting the ring index limit， the combustion phase is optimized to avoid excessive exhaust losses， which is the key to improving thermal efficiency under medium and high load conditions. The results show that as the load increases， the optimized performance corresponding intake pressure and EGR rate boundary conditions both increases and the minimum diesel mass decreases. In particular， the indicated thermal efficiency can be increased to 52.1% at indicated mean effective pressure of 1.7 MPa， and the minimum diesel energy ratio is 4.7%. |
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