3D CFD Simulations of Hydrogen Engine Combustion
(2023) MVKM05 20231Department of Energy Sciences
- Abstract
- With the trend of decarbonization, the transport sector is exploring possibilities of fossil fuel free solutions. Hydrogen can be a potential fuel for future engine applications. In this work, the concept of H2 HPDI is investigated, where a pilot diesel injection ignites the hydrogen jet. This solution may enable low carbon emission and high energy efficiency. 3D CFD simulation is performed using CONVERGE. Fuel temperature, wall temperature, fuel injection timings, swirl ratio and kinetic mechanisms are studied to calibrate the model. The models is validated against experiment results at mid-load conditions. Then, varied mass of pilot diesel is studied and results show that as low as 0.5% energy share in the pilot diesel are sufficient to... (More)
- With the trend of decarbonization, the transport sector is exploring possibilities of fossil fuel free solutions. Hydrogen can be a potential fuel for future engine applications. In this work, the concept of H2 HPDI is investigated, where a pilot diesel injection ignites the hydrogen jet. This solution may enable low carbon emission and high energy efficiency. 3D CFD simulation is performed using CONVERGE. Fuel temperature, wall temperature, fuel injection timings, swirl ratio and kinetic mechanisms are studied to calibrate the model. The models is validated against experiment results at mid-load conditions. Then, varied mass of pilot diesel is studied and results show that as low as 0.5% energy share in the pilot diesel are sufficient to trigger H2 ignition. To further eliminate the carbon emission, the possibility of using H2 as the only fuel at mid-load conditions is studied. Due to the high autoignition temperature of H2, solutions like inlet preheating and H2 pilot injection are applied to provide the high temperature to achieve H2 combustion near TDC. Simulation results show that significant inlet preheating is needed and 60 K increase at IVC is needed for H2 combustion. With this solution, lower closed-cycle efficiency is observed due to high heat losses. As for pilot H2 combustion, with 5% energy share in the pilot H2, mixing-controlled combustion of H2 can be observed with only 15 K increase in the IVC temperature. Comparable efficiency to engines with pilot diesel injections can be observed while NOx emission increases due to higher flame temperature of H2 combustion. Finally, the work connected to H2 direct injection is investigated. Due to the large number of moles of gas injected near TDC, additional work as high as 2.7% of the fuel energy can be achieved. (Less)
- Popular Abstract
- Can we run an internal combustion engine with carbon-neutral fuels? Well, Formula 1 aims to achieve carbon neutral by 2030, but what about the everyday transportation? More than 2000 Mt of CO2 emission in 2021 was caused by buses and trucks. To decrease carbon emissions, changes in the fuel need to be made. Hydrogen, whose combustion product is only water, can be a good alternative.
In the transport industry, every percent of the engine efficiency counts. To achieve high engine efficiency, diesel-type engines are preferred. In these engines, typically diesel fuel is injected into the cylinder and autoignition takes place. The chemical energy in the diesel fuel is transformed into heat and then work.
However, things are not quite the... (More) - Can we run an internal combustion engine with carbon-neutral fuels? Well, Formula 1 aims to achieve carbon neutral by 2030, but what about the everyday transportation? More than 2000 Mt of CO2 emission in 2021 was caused by buses and trucks. To decrease carbon emissions, changes in the fuel need to be made. Hydrogen, whose combustion product is only water, can be a good alternative.
In the transport industry, every percent of the engine efficiency counts. To achieve high engine efficiency, diesel-type engines are preferred. In these engines, typically diesel fuel is injected into the cylinder and autoignition takes place. The chemical energy in the diesel fuel is transformed into heat and then work.
However, things are not quite the same for hydrogen in such engines. Hydrogen has higher autoignition temperature than diesel, so conventional diesel combustion method is not applicable to hydrogen. What can we do?
In this work, a solution called pilot diesel injection is applied. We inject a small amount of diesel to create a hot atmosphere so that the hydrogen can ignite. 3D CFD simulation is performed to study the process. Smooth diesel-like hydrogen combustion can be achieved with this method and high engine efficiency and low CO2 emission can be observed.
Such engines still need diesel pilot to trigger H2 combustion. Is there a solution to eliminate the diesel fuel? The answer is yes under some operating conditions. Normally, the engine uses intercooler to cool the intake air. If some of the hot air
bypasses the intercooler, hotter atmosphere can be provided and hydrogen autoignition can be achieved. Such solution is called as inlet preheating. However, with only one hydrogen injection, much inlet preheating is needed, resulting in lower engine
efficiency. To increase the efficiency, we introduce a pilot H2 injection. This H2 injection helps the autoignition and less inlet preheating is needed. In this way, higher engine efficiency can be observed and zero CO2 emission can be achieved (Less)
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@misc{9125419,
abstract = {{With the trend of decarbonization, the transport sector is exploring possibilities of fossil fuel free solutions. Hydrogen can be a potential fuel for future engine applications. In this work, the concept of H2 HPDI is investigated, where a pilot diesel injection ignites the hydrogen jet. This solution may enable low carbon emission and high energy efficiency. 3D CFD simulation is performed using CONVERGE. Fuel temperature, wall temperature, fuel injection timings, swirl ratio and kinetic mechanisms are studied to calibrate the model. The models is validated against experiment results at mid-load conditions. Then, varied mass of pilot diesel is studied and results show that as low as 0.5% energy share in the pilot diesel are sufficient to trigger H2 ignition. To further eliminate the carbon emission, the possibility of using H2 as the only fuel at mid-load conditions is studied. Due to the high autoignition temperature of H2, solutions like inlet preheating and H2 pilot injection are applied to provide the high temperature to achieve H2 combustion near TDC. Simulation results show that significant inlet preheating is needed and 60 K increase at IVC is needed for H2 combustion. With this solution, lower closed-cycle efficiency is observed due to high heat losses. As for pilot H2 combustion, with 5% energy share in the pilot H2, mixing-controlled combustion of H2 can be observed with only 15 K increase in the IVC temperature. Comparable efficiency to engines with pilot diesel injections can be observed while NOx emission increases due to higher flame temperature of H2 combustion. Finally, the work connected to H2 direct injection is investigated. Due to the large number of moles of gas injected near TDC, additional work as high as 2.7% of the fuel energy can be achieved.}},
author = {{Liu, Hao}},
issn = {{0282-1990}},
language = {{eng}},
note = {{Student Paper}},
title = {{3D CFD Simulations of Hydrogen Engine Combustion}},
year = {{2023}},
}