At the SAE High-Efficiency Engine Forum before WCX2019 (World Congress Experience) in Detroit this year, the chief researcher of Delphi Technologies revealed in his speech that based on the current Delphi-led GDCI high-efficiency engine research and development results, the future is expected Launched a gasoline engine with a thermal efficiency of 50%.
Although the development of new energy vehicles has been in full swing in recent years, it has brought quite severe challenges to the development of traditional internal combustion engine technology, but within a short time, or by 2025 , The engine is still the mainstream power of the car. In the process of developing towards electrification, hybrid power, as an important solution during the transition period, still needs the strong support of the engine.
is based on this trend judgment, Delphi is still continuing to invest in the development of a new generation of engine technology. As a long-term project developed by Delphi, GDCI engine has been carried out to the third generation.
GDCI draws on the concept of HCCI homogeneous compression ignition technology, but the difference from GDCI and HCCI is that the HCCI engine injects fuel into the combustion chamber during the intake stroke. Fuel and air are fully mixed during the compression stroke of the piston. When the piston reaches the top dead center of the cylinder, the mixture is compressed and self-ignites. The GDCI engine only injects fuel after the piston reaches the top dead center. After the fuel is injected into the cylinder, it mixes with high-temperature air and ignites instantly. Thanks to the characteristics of low-temperature combustion and high-speed combustion of this technology, the engine achieves maximum thermal efficiency.
Delphi's GDCI engine is different from ordinary gasoline engines in that it can achieve direct compression ignition without the participation of spark plugs. It can be said to be a perfect combination of gasoline and diesel engines. The low cost of gasoline engine and the high efficiency of diesel engine are even better than Sky Active-X of Mazda. Although Delphi’s GDCI and Mazda’s skyactive-x both use the concept of HCCI homogeneous compression ignition, Mazda’s SkyActive-X still needs spark plug assistance. Compared with GDCI, the structure is more complicated, the cost is higher and the combustion control More complicated.
Delphi’s GDCI (left) and Mazda’s Sky Active-X (right)
In the third-generation (gen3) GDCI engine announced in the previous period, it uses 350bar With the fuel injection system, the compression ratio has been increased from 14.5:1 to 16:1. Long stroke S/B=1.28 is adopted. According to the test results, the minimum fuel consumption rate is 200g/kW.h, which can achieve a thermal efficiency of 42%.
Comparison of Gen3GDCI engine thermal efficiency with competing products
As can be seen from the above figure, the thermal efficiency of Gen3 GDCI engine is 22% higher than that of 2.0TGDI (EA888) engine. The 2.0L diesel engine increased by 11%, and the intersecting 1.8L Atkinson engine (third-generation Prius) increased by 11%.
In addition, Delphi's GDCI also received a four-year project funding of $9.8 million from the US Department of Energy to continue to improve the performance and efficiency of the GDCI engine while reducing costs.
Delphi's three main GDCI projects
At the 2019 SAE High Efficiency Internal Combustion Engine Forum, Delphi announced the latest Gen3X GDCI engine research and development results, the Gen3X engine is a 2.2L engine Four cylinder double overhead camshaftCompared with the gen3 generation GDCI engine, the compression ratio of the gasoline engine is increased from 16:1 to 17:1 of the gen3, and the performance of the fuel injection system, valve mechanism and supercharging system is also improved. The most important thing is that the new generation engine adopts new High-load combustion strategy. In the Gen3X engine, the engine working interval is divided into "low load/cold start operation interval" and "medium-high load operation interval", and different combustion control strategies are adopted respectively. The test results of the Gen3X GDCI engine show that its fuel consumption rate is as low as 194g/kW.h, which is equivalent to a thermal efficiency of 43.5%.
The chief expert of Delphi Technology said at the meeting that the fourth-generation GDCI (GEN4X) may use thermal insulation coatings for cylinders to further reduce heat loss, and continue to optimize control strategies, as well as other technologies. Comprehensive application, and finally achieve 50% thermal efficiency. According to Delphi's plan, the GDCI engine may be mass-produced in 2022.
Delphi, as a well-known component supplier, the significance of the successful development of high-efficiency GDCI engine is much greater than that of Mazda’s Sky Active-X. After all, Mazda’s Sky Active-X is very To a large extent, it is only for Mazda brand models, while Delphi can supply technology to other OEM manufacturers.
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