Simulation and Control of Combustion in Military Diesel Engines

Effort began in 2013 (ARC Phase III) and concluded in 2018 (ARC Phase IV) across two consecutive projects.

The goal of this project was to develop combustion mechanisms needed for the 3-D simulation codes which are used to design, develop, and control advanced diesel engines. Since military, as well as domestic fuels, are distillates composed of a large number of different hydrocarbons, and it is impossible to develop combustion mechanisms for them all, surrogate fuels composed of a small number of hydrocarbons, of known combustion mechanisms, are needed to collectively emulate the physical and chemical processes of the distillates. The number of components should be small to reduce the time and cost of computation.

In this project, a combustion mechanism based on a surrogate fuel of two components (60% n-dodecane and 40% Trimethylbenzene) was developed for JP8, and another mechanism based on surrogate of three components (46% Isocetane, 10% n-Nonane and 44% decalin) was developed for Sasol-IPK. The JP8 and Sasol-IPK surrogates were first validated in IQT (Ignition Quality Tester) in which combustion occurs in a constant volume environment and the charge pressure and temperature are kept constant. Analysis of the ignition delay, peak gas pressure, RHR peak, and their locations, showed a closer match in the IQT than in the diesel engine in case of the Sasol-IPK surrogate. While a very good match was observed in both the IQT and the diesel engine at all conditions in case of the two-component surrogate.

This was followed by validation of the two surrogates in two single-cylinder diesel engines. Results of tests on PNGV (Partnership for New Generation of Vehicles) diesel engine showed clearly that the 2-component surrogate produced a good match with the results of tests using JP8 considering different parameters of autoignition, combustion, performance, and engine-out emissions. For Sasol-IPK, tests were conducted on a modified HATZ single-cylinder diesel engine and the match was not as good as that of JP8.

Finally, the reduced mechanism for JP8 surrogate was developed and applied in a 3-D CFD cycle simulation code of combustion in two diesel engines. The first was the PNGV single-cylinder diesel engine at different injection timings, and intake air temperatures, and the simulated results showed a good match with the experimental results for the cycle-resolved cylinder gas pressure, ignition delay, engine-out emissions of un-burnt hydrocarbons, carbon monoxide, and nitrogen oxides. The second engine was the CAT C7 six-cylinder military diesel engine at different loads. Simulation results for the cycle-resolved cylinder gas pressure agreed with the experimental data.

In the subsequent effort, (1) Sasol-IPK 3-component surrogate was refined to get a better match with the target fuel, (2) extended investigation to blends of JP8 and Sasol IPK that are expected to be used in military engines, and (3) validated JP8 mechanism in the simulation of diesel engine operation during the cold start at low ambient temperatures in the cold room at Wayne State University.

Publications:

• Alkhayat, Samy, et al. “Experimental Validation of a Three-Component Surrogate for Sasol-Isoparaffinic Kerosene in Single Cylinder Diesel Engine and Ignition Quality Tester.” Journal of Engineering for Gas Turbines and Power 140.8 (2018).
• Udayachalam, Krishnaraj, et al. Development of a Surrogate for SASOL IPK and Its Validation in Ignition Quality Tester. No. 2017-01-0263. SAE Technical Paper, 2017.
• Joshi, Umashankar Mohan Chandra, et al.,” Simulation and Comparison of Auto-ignition of Homogeneous Fuel/Air Mixtures and Sprays in Diesel Engines.” SAE Technical paper 2016-01-0311, 2016.
• Zheng, Ziliang, et al. “Effect of cetane improver on combustion and emission characteristics of coal-derived Sasol isomerized paraffinic kerosene in a single cylinder diesel engine.” Journal of Engineering for Gas Turbines and Power 137.7 (2015): 071506.
• Joshi, Umashankar, et al. “An Investigation on Sensitivity of Ignition Delay and Activation Energy in Diesel Combustion.” Journal of Engineering for Gas Turbines and Power 137.9 (2015): 091506.
• Shrestha, Amit, et al. “Development of JP-8 surrogates and their validation using ignition quality tester.” SAE International Journal of Fuels and Lubricants 7.2014-01-9077 (2014): 337-351.
• Shrestha, Amit, et al. “Experimental Validation and Combustion Modeling of a JP-8 Surrogate in a Single Cylinder Diesel Engine.” SAE International Journal of Fuels and Lubricants 7.2014-01-1376 (2014): 94-105.