Identification of the optimum of parameters for operating a natural gas fueled low-cost 30 kW engine with a compression ratio of 20:1, and testing post combustion to reduce emission
This project is a continuation of previous work conducted by TK Energi, with the objective of optimising small scale gas fuelled engine generator sets, especially concerning efficiency, emissions and cost price. It has been decided to work with high compression engines, in order to increase the engine efficiency.
The aim of this project is to identify the potential of efficiency and emissions operating an automotive engine with high compression ratio on natural gas. (Compression ratio 1:20, power output 30 kW). The project consists of: 1) Building a small scale power plant, based on a high compressed engine (diesel) converted to spark ignition. 2) Test running this plant for a longer period of time (1000 h). 3) Developing strategies of operation which results in low emissions of both NOx, CO and UHC, and determine the efficiency related to the emissions. 4) Developing a post combustion chamber in order to reduce emissions of UHC, increasing the overall efficiency. An electrical efficiency of 35-38 % is expected within the emission limits (550 mg NOx 500 mg CO and 1500 mg UHC). The electrical efficiency of a VW 1,9 TDI diesel engine coupled to an ABB generator, is 40,7 according to the specifications given by the manufactures. Reducing the emissions is expected to reduce the efficiency. The efficiency is highly dependent on the assumption that knocking can be avoided. Results from an earlier project (UVE j.nr. 51161/97-0023) have shown it possible to operate a 1,3 litre Toyota engine, compression ratio 1:10, on natural gas, with an electrical efficiency of 34 % within the limits of emissions proposed to engines above 120 kW
The risk of knocking is increased when raising the compression ratio. Tests performed on a natural gas fuelled 1.3 litre spark ignition (SI) engine supercharged up to 2 bar (rel.) did nog show any knocking tendencies. Therefore it was decided to do further investigations into high compression gas engines. The objective of the project is to determine the efficiency and emission potential in natural gas fuel-led high compression ratio engines for decentralised heat and power productionpurposes. Furthermore, it was decided to use exhaust gas post-combustion as a mean of reducing methane emissions from the engine. These emissions are considered the main problem in regards to natural gas engines, due to the large impact to the greenhouse gas effect resulting from the unburned methane. A small scale engine generator-set, based on a VW 1.9 litre TDI engine with a compression ratio of 19.5:1, was designed. The engine has been tested on diesel, dual fuel and natural gas (SI). An investigation of the correspondence in between efficiency and emissions has been conducted. By converting the engine from dual fuel to SI, efficiency decresed and UHC emissions incrased. It is possible to operate the engine withour knocking, however, knocking was found to be the limiting factor in optimising the engine performance. The optimum engine set-point for efficiency was found to be at lambda 1.5. In this point, electric efficiency was found to be 35% and the emissions: UHC: 900 mg/Nm3, CO: 1100 mg/Nm3 and NOx: 1500 mg/Nm3. Emission levels correspond to 5% O2. The high levels of UHC,CO and NOx, made it impossible to meet the Danish environmental limit without the use of emission control devices. A post combustion chamber has been designed and built. The device reduces the levels of UHC and CO far below the emission regulation levels, hereby making lean burn operation a possibility and thus reducing NOx emissions. A 1000 hours field test of the entire plant has been conducted, which obtained emission levels as low as: UHC: 5 mg/Nm3, CO: 150 mg/Nm3 and NOx: 130 mg/Nm3 with an electric efficiency of 32%. Emission levels correspond to 5% O2
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| Partner | Subsidy | Auto financing |
|---|---|---|
| NESA A/S |
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