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In-Cycle Closed-Loop Combustion Controllability with Pilot-Main Injections

Jorques Moreno, Carlos LU ; Stenlåås, Ola LU and Tunestål, Per LU (2018) Thermo-and Fluid Dynamic Processes in Direct Injection Engines, THIESEL 2018
Abstract
In-cycle closed-loop combustion control has been proved to reduce cycle-to-cycle variations on emissions and indicated thermal efficiency. In this paper, the in-cycle closed-loop combustion con-trollability achieved by a pilot-main fuel injection scheme is investigated. The controllability is studied by means of the maximum reachable indicated thermal efficiency (MRE). A combustion model is used for the heat release optimisation. The pilot model parameters were modified to simulate the dis-turbances of the pilot combustion. The MRE is the result of optimizing the heat release, constrained to a constant load, with a disturbed pilot injection and adjusting the main start of injection (SOI) and its duration. The nominal indicated thermal... (More)
In-cycle closed-loop combustion control has been proved to reduce cycle-to-cycle variations on emissions and indicated thermal efficiency. In this paper, the in-cycle closed-loop combustion con-trollability achieved by a pilot-main fuel injection scheme is investigated. The controllability is studied by means of the maximum reachable indicated thermal efficiency (MRE). A combustion model is used for the heat release optimisation. The pilot model parameters were modified to simulate the dis-turbances of the pilot combustion. The MRE is the result of optimizing the heat release, constrained to a constant load, with a disturbed pilot injection and adjusting the main start of injection (SOI) and its duration. The nominal indicated thermal efficiency was optimized at the central operating condi-tions.
The results showed that the most influential variable in the indicated thermal efficiency was the dis-turbances in the pilot mass. 79% of the efficiency variability can be explained by the actual injected pilot mass. The second and third most significant variables were the variances in the combustion effi-ciency and either of both, the start of vaporisation or the start of combustion (depending on the vari-ables interaction). The disturbances in the pilot combustion resulted in a reduction down to -0.8%unit net indicated thermal efficiency compared to the nominal maximum indicated thermal efficiency.
The results confirmed that by adjusting the main SOI, the indicated thermal efficiency can be im-proved in 86% of the total cases with an average change about +0.1%unit in net indicated thermal effi-ciency. The maximum improvement was +1%unit net indicated thermal efficiency for pilot masses larg-er than the nominal point, with longer ignition delay and increased combustion efficiency. The pilot in-jection is observable 1CAD after its start of combustion, which limits the controllability of the main SOI. In 86.2% of the considered cases, the main SOI was controllable in-cycle. When the main SOI was constrained to the controllable window, the reduction in indicated thermal efficiency was negligi-ble compared to the maximum indicated thermal efficiency achievable by in-cycle closed-loop com-bustion control.
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publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
host publication
THIESEL 2018 : Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines - Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines
conference name
Thermo-and Fluid Dynamic Processes in Direct Injection Engines, THIESEL 2018
conference location
Valencia, Spain
conference dates
2018-09-11 - 2018-09-14
language
English
LU publication?
yes
id
cc0743d5-aa52-463c-9d0f-845fb00b87a4
date added to LUP
2021-04-20 08:54:05
date last changed
2021-04-20 12:05:25
@inproceedings{cc0743d5-aa52-463c-9d0f-845fb00b87a4,
  abstract     = {{In-cycle closed-loop combustion control has been proved to reduce cycle-to-cycle variations on emissions and indicated thermal efficiency. In this paper, the in-cycle closed-loop combustion con-trollability achieved by a pilot-main fuel injection scheme is investigated. The controllability is studied by means of the maximum reachable indicated thermal efficiency (MRE). A combustion model is used for the heat release optimisation. The pilot model parameters were modified to simulate the dis-turbances of the pilot combustion. The MRE is the result of optimizing the heat release, constrained to a constant load, with a disturbed pilot injection and adjusting the main start of injection (SOI) and its duration. The nominal indicated thermal efficiency was optimized at the central operating condi-tions.<br/>The results showed that the most influential variable in the indicated thermal efficiency was the dis-turbances in the pilot mass. 79% of the efficiency variability can be explained by the actual injected pilot mass. The second and third most significant variables were the variances in the combustion effi-ciency and either of both, the start of vaporisation or the start of combustion (depending on the vari-ables interaction). The disturbances in the pilot combustion resulted in a reduction down to -0.8%unit net indicated thermal efficiency compared to the nominal maximum indicated thermal efficiency.<br/>The results confirmed that by adjusting the main SOI, the indicated thermal efficiency can be im-proved in 86% of the total cases with an average change about +0.1%unit in net indicated thermal effi-ciency. The maximum improvement was +1%unit net indicated thermal efficiency for pilot masses larg-er than the nominal point, with longer ignition delay and increased combustion efficiency. The pilot in-jection is observable 1CAD after its start of combustion, which limits the controllability of the main SOI. In 86.2% of the considered cases, the main SOI was controllable in-cycle. When the main SOI was constrained to the controllable window, the reduction in indicated thermal efficiency was negligi-ble compared to the maximum indicated thermal efficiency achievable by in-cycle closed-loop com-bustion control.<br/>}},
  author       = {{Jorques Moreno, Carlos and Stenlåås, Ola and Tunestål, Per}},
  booktitle    = {{THIESEL 2018 : Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines}},
  language     = {{eng}},
  month        = {{09}},
  title        = {{In-Cycle Closed-Loop Combustion Controllability with Pilot-Main Injections}},
  year         = {{2018}},
}