| 1. |
- Christensen, Magnus, et al.
(författare)
-
Homogeneous Charge Compression Ignition with Water Injection
- 1999
-
Ingår i: SAE Special Publications. - 0099-5908. ; 1999:1444
-
Konferensbidrag (refereegranskat)abstract
- The use of water injection in a homogeneous charge compression ignition (HCCI) engine was experimentally investigated. The purpose of this study was to examine whether it is possible to control the ignition timing and slow down the rate of combustion with the use of water injection. The effects of different water flows, air/fuel ratios and inlet pressures were studied for three different fuels, iso-octane, ethanol and natural gas. It is possible to control the ignition timing in a narrow range with the use of water injection, but to the prize of an increase in the already high emissions of unburned hydrocarbons. The CO emission also increased. The NOx emissions, which are very low for HCCI, decreased even more when water injection was applied. The amount of water used was of the magnitude of the fuel flow.
|
|
| 2. |
- Einewall, Patrik, et al.
(författare)
-
The Potential of Using the Ion-Current Signal for Optimizing Engine Stability - Comparisons of Lean and EGR (Stoichiometric) Operation
- 2003
-
Ingår i: SAE Special Publications. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0099-5908. ; 2003:1749
-
Konferensbidrag (refereegranskat)abstract
- Ion current measurements can give information useful for controlling the combustion stability in a multi-cylinder engine. Operation near the dilution limit (air or EGR) can be achieved and it can be optimized individually for the cylinders, resulting in a system with better engine stability for highly diluted mixtures. This method will also compensate for engine wear, e.g., changes in volumetric efficiency and fuel injector characteristics. Especially in a port-injected engine, changes in fuel injector characteristics can lead to increased emissions and deteriorated engine performance when operating with a closed-loop lambda control system. One problem using the ion-current signal to control engine stability near the lean limit is the weak signal resulting in low signal-to-noise ratio. Measurements presented in this paper were made on a turbocharged 9.6-liter, six-cylinder natural gas engine with port injection. Each cylinder was individually controlled by a cylinder control module (CCM). A high turbulence combustion chamber was used to be able to operate with highly diluted mixtures. Comparisons between lean and EGR (stoichiometric) operation were made to investigate the potential of using the ion-current signal to control engine stability (cylinder-to-cylinder and cycle-to-cycle variations). A much stronger ion-current signal was found with EGR compared to lean operation, for the same load and comparable emissions.
|
|
| 3. |
- Fridell, Erik, 1963, et al.
(författare)
-
Model studies of sulfur deactivation of NOx storage catalysts
- 2004
-
Ingår i: Society of Automotive Engineers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0099-5908. - 0768013194 ; SP-1860, s. 115-119
-
Tidskriftsartikel (refereegranskat)abstract
- Model NOx storage catalysts were used to study the sulfur deactivation of these systems using reactor studies, FTIR and XPS. It is found that the deactivation rate shows a linear dependence on the SO2 concentration and that bulk sulfates are easily formed. Experiments with SO2 present either during lean or during rich conditions show a more rapid deactivation in the latter case.
|
|
| 4. |
- Olsson, Jan-Ola, et al.
(författare)
-
A Turbocharged Dual-Fuel HCCI Engine
- 2001
-
Ingår i: SAE Special Publications. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0099-5908. ; 2001:1627
-
Konferensbidrag (refereegranskat)abstract
- A 6-cylinder truck engine is modified for turbocharged dual-fuel Homogeneous Charge Compression Ignition (HCCI) engine operation. Two different fuels, ethanol and n-heptane, are used to control the ignition timing. The objective of this study is to demonstrate high load operation of a full-size HCCI engine and to discuss some of the typical constraints associated with HCCI operation. This study proves the possibility to achieve high loads, up to 16 bar Brake Mean Effective Pressure (BMEP), and ultra-low NOdx emissions, using turbo charging and dual fuel. Although the system shows great potential, it is obvious that the lack of inlet air pre heating is a drawback at low loads, where combustion efficiency suffers. At high loads, the low exhaust temperature provides little energy for turbocharging, thus causing pump losses higher than for a comparable diesel engine. Design of turbocharger therefore, is a key issue in order to achieve high loads in combination with high efficiency. In spite of these limitations, brake thermal efficiencies and power rating close to those of the original diesel engine are achieved with significant reduction in NOdx emissions. The maximum efficiency is 41.2%, which is slightly lower than for the original diesel engine.
|
|
| 5. |
- Papadakis, Klaus, et al.
(författare)
-
Stationary NOx storage and reduction experiments on a heavy-duty diesel engine rig using a bypass system
- 2003
-
Ingår i: Society of Automotive Engineers - Technical Paper Series. - 0099-5908. ; , s. 117-122
-
Tidskriftsartikel (refereegranskat)abstract
- This work concerns exhaust gas cleaning for heavy-duty diesel engines by means of NOx storage and redn. technol. A full-scale engine rig has been constructed, and stationary NOx redn. tests performed. In the NOx storage and redn. approach, NOx is stored on a BaO surface as Ba(NO3)2 under long lean conditions and desorbed and reduced under short rich conditions. The rich conditions are created by injection of diesel fuel into the exhaust stream. The stationary NOx redn. tests have been performed at nine load points on an engine rig. They have shown that a stationary NOx redn. of between 25-53% is achievable at most load points depending on the temp. The high oxygen content in the exhaust gas leads to the oxidn. of the injected hydrocarbons and thus to a high fuel penalty. To lower the fuel consumption, the mass flow through the catalyst has been reduced under the regeneration periods. This was done using a bypass system with a pneumatic valve control. The extent of the reduced catalyst flow has been examd.
|
|
| 6. |
- Tunestål, Per, et al.
(författare)
-
Hydrogen Addition For Improved Lean Burn Capability of Slow and Fast Burning Natural Gas Combustion Chambers
- 2002
-
Ingår i: SAE Special Publications. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0099-5908. ; 2002:1725, s. 21-32
-
Konferensbidrag (refereegranskat)abstract
- One way to extend the lean-burn limit of a natural gas engine is by addition of hydrogen to the primary fuel. This paper presents measurements made on a one-cylinder, 1.6- liter natural gas engine. Two combustion chambers, one slow and one fast burning, were tested with various amounts of hydrogen (0, 5, 10 and 15%-vol) added to natural gas. Three operating points were investigated for each combustion chamber and each hydrogen content level; idle, part load (5 bar IMEP) and 13 bar IMEP (simulated turbocharging). Air/fuel ratio was varied between stoichiometric and the lean limit. For each operating point, a range of ignition timings were tested to find maximum brake torque (MBT) and/or knock. Heat-release rate calculations were made in order to assess the influence of hydrogen addition on burn rate. Addition of hydrogen showed an increase in burn rate for both combustion chambers, resulting in more stable combustion close to the lean limit. This effect was most pronounced for lean operation with the slow combustion chamber.
|
|
