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For heavy-duty Diesel Engines
Turbodyne Canada
ABSTRACT
This paper describes the development of an emissions upgrade kit for the Caterpillar heavy-duty 3406E engine. The upgrade kit for the CAT 3406E engine incorporates continuous water injection (CWI) system, designed and manufactured by Turbodyne Systems, Inc. in cooperation with A.M. Turbo/Engine Design of Vancouver, BC A significant emission reduction has been demonstrated for the CAT engines.
INTRODUCTION
The internal combustion engine, gasoline and diesel, is the backbone and preeminent mode of transportation and source of power in the modern industrial world. Increasingly, worldwide strict legislation covering environmental issues and energy efficiency is causing manufacturers and end-users to focus on the drawbacks of the engines. Two major issues need addressing: fuel economy and pollutant emissions. There is increasing global urgency about air pollution's escalating damage to the environmental and human health. This environmental damage, including smog, acid rain and the deterioration of the ecosystem, is causing governments and industry to search for a solution to these problems. The world is becoming aware of hazard engine emissions, which range from eye irritation, asthma and emphysema, to lung cancer and premature death. Apprehension over air pollution is coupled with growing concern for our natural resources, including the depletion of petroleum reserves. The ultimate impact on the quality of life, in addition to the tremendous economic costs, is the driving force behind new, more serious legislation and focus by both the industrialized nations and developing countries. Global environmental conferences, exemplified by the recent global warming conference in Kyoto, Japan, demonstrate the existing urgency.
The Kyoto Climate Change Convention is pointing the compass towards the future for energy companies and corporations relying on fossil fuels - greenhouse gas (GHG) emissions must be drastically reduced.
Canada agreed to reduce its combined emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) by 6% below their baseline 1990 levels. It was also agreed to bring down combined emissions of hydroflourocarbon (HFC), perfluorocarbon (PFC) and sulfur hexafluoride (SF6) by 6%, measured against 1990 or 1995 baseline levels. All this is to occur between 2008 and 2012.
Reducing fossil fuel consumption is an enormous challenge for the any energy intensive society. The economic transition may be costly and difficult.
In the U.S., more stringent criteria for reduction of emissions in urban buses and heavy-duty engines were mandated again for 1998. For example, the EPA's new locomotive standards impose new requirements for oxides of nitrogen (NOx), hydrocarbons (HC), carbon monoxide (CO) and smoke for newly manufactured and remanufactured diesel-powered locomotives, which have previously been unregulated. According to these new standards, the NOx emissions for the average locomotive build between 1973 and 1997 must be reduced by 37%.
Similar laws are being implemented around the world.
Energy efficiency and renewable energy technologies will be the primary means to achieve the Kyoto targets. At present, there are not many companies, which can offer the technical solutions for the control of pollution and greenhouse emissions. However, Turbodyne Technology Inc. is a company that has such a technology.
THE PROBLEM
The traditional diesel engine suffers from the high NOx and particulate emissions, and most strategies to reduce either NOx or particulate emission cause an increased emission of the other. Reducing NOx emissions from the diesel engines has historically been achieved by the following technologies:
1. Retarding the injection timing (RIT);
2. Exhaust after-treatment (EAT);
3. Exhaust Gas Recirculation (EGR)
All of the above technologies have numbers of disadvantages and limits. For example, injection timing can be varied to reduce NOx (by retarding) but only with a corresponding increase in the other pollutants. In addition this method leads to inevitable fuel consumption penalty.
The EAT technology, whilst successful in controlling NOx, is very expensive and affected engine power and fuel consumption.
Exhaust Gas Recirculation is used in many passenger cars in order to reduce NOx on part load conditions only. In heavy-duty application and for full load conditions the EGR significantly increases engine wear, specific fuel consumption and visible smoke.
Using water in diesel engine is as old as the diesel engine industry itself and seems to show up again on a regular cycle. About every 10 years, somebody rediscovers a way to put water into an engine to lower combustion temperatures and to enhance engine performances and the industry runs through another engineering cycle to evaluate the concept. Numerous studies are now under way on emulsified fuels and water injection directly into cylinders.
Germany's Daimler-Benz and Japanese automaker Mitsubishi found that a stratified diesel/water/diesel (DWD) injection system can cut both NOx and PM emissions to EURO IV emissions standards around 2005, with a fuel economy improvement.
The main obstacles to DWD are the very high cost of DWD injectors and DWD control system. That explains why we in Turbodyne set up a program to design a simple not expensive water injection system which can used relatively low-quality water and reduce NOx up to 40% without affecting engine performances.
DEVELOPMENT OF NEW CONTINUOUS WATER INJECTION TECHNOLOGY
In August 1998, Turbodyne arranged with the Emissions Research and Measurement Division (ERMD) of Environment Canada, to conduct a controlled test program on a 1995 Caterpillar 3406E 455 hp heavy-duty engine with the intent of demonstrating the performance of the CWI technology. A program was arranged with two test engine configurations - one as the baseline and the other with the CWI in operation. The evaluation was comprised of a series test simulation protocol emission tests which started with one baseline test followed by a number of consecutive CWI device tests. Conformance to Canadian Motor Vehicle Safety Standards (CMVSS) and the USA's EPA Code of Federal Regulations (CFR) was followed for emission testing of the heavy-duty diesel engines.
RESULTS
The emission collection apparatus made use of a constant volume sampling (CVS) system that dilutes the engine exhaust during a test with ambient air from the test cell. This allows measurement of the true mass of the gaseous and particulate emissions from the engine's operation.
During the test, a continuously proportioned dilute exhaust sample is drawn from the CVS. Temperature and pressure sensors in the region of the venturi and sampling zone allow correction of volumetric flow rate to standard conditions. The exhaust sampling is finally measured by detector response (in real time) for gaseous emission concentrations and by filter weight gain for the P.M. emission. Fuel consumption was measured with an electronic gravimetric fuel meter. The following list details the equipment used:
- Oxides of Carbon (CO and CO2) - Horiba AIA-23 detectors
- Total hydrocarbons (THC) - Pierburg FID 2000 heated flame ionization detector
- Oxides of Nitrogen (NOx) - Pierburg CLD 2000 heated chemiluminescence detector
- Particulate Matter (P.M.) - double dilution gravimetric analysis
- Fuel Consumption - AVL 733S gravimetric fuel meter.
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Table 1. Weighted Emission results from 1995 Caterpillar 3406E.
COMPARATIVE ANALYSIS
The data from the weighted-average tabulation in Table 1, is a compendium of the modal data that came from specific operating conditions (i.e. water injection pressure or injection location). For this reason, a statistical study could not be undertaken, but a direct comparison can be presented. This comparison is simply the percent relative difference on the each single test point to the corresponding value of the initial baseline for each test day as in the following equation:
| measurement value-initial baseline value | ||
| Measurement = | __________________________________ |
x 100% |
| initial baseline value |
Below, in Table 2, the CWI data relevant to the study is compared by way of the percent relative difference to the initial baseline results, except for the exhaust temperature which is simply a degree Celsius difference from the initial baseline value.
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Table 2: Relative Difference of the Weighted Initial Baseline Values * the particulate emission n is a time average not weighted-average number for comparison
The general trend given by Table 1 and Table 2 is that the operation of the CWI system impacts the NOx, CO, and P.M. emissions as well as exhaust gas temperature and fuel consumption. The tests done when the CWI system operated before the air-to-air cooler (position one, Table 1 and Table 2) show that the mass emission of NOx was reduced from 23.3 up to 33.5% (see also Fig.1). This improvement is observed when the water injection is increased and the mass is compared to the initial baseline test data of the same day tests. Particulate mass also reduced from 2% to 8.4% for these same test runs (see Fig.2). Exhaust gas temperatures are reduced by roughly 20° C to as much as 26 ° C for the same test runs (Fig.3). The fuel consumption record shows a reduction of as much as 0.5% with water/air ratio of 1.6% (Fig, 4). It means that with water/air ratio of around 1.6% the 25% of NOx reduction is achievable with simultaneous 0.5 % fuel economy and approximately 6% reduction of PM emission for the CAT. 3406E engine. The bigger NOx and PM reduction may be achieved with smaller fuel savings and bigger amount of water being injected. It is very important to notice that water injection does not affected engine power (the fluctuation of engine power is +/- 0.1%).
It should be also underlined that CAT 3406E is an electronically controlled engine. That explains why the fuel savings achieved are relatively small. For a mechanically controlled engines typical fuel savings due to CWI are estimated to be in the neighborhood of 3% - 5%.
CONCLUSION
1. Continuous water injection technology has presented itself as a powerful tool for NOx emission reduction. In the electronically controlled Caterpillar 3406E engines up to 35% of NOx reduction is achievable with simultaneous fuel consumption, particulate matters and CO emissions reductions when the water injected between the compressor and air-to-air cooler.
2. For a mechanically controlled engine equipped with CWI System up to 40% of NOx reduction is visible with simultaneous reduction in fuel consumption (up to 5%), PM and CO emissions.
ACKNOWLEDGMENTS
The author would like to express his gratitude for the assistance provided by Mr. Rhett Hedrick of Turbodyne Systems, Inc. and Mr. Angus Craig of ERMD Canada.
REFERENCES
1. CFR Title 40 Part 85 Subpart O "CONTROL OF AIR POLLUTION FROM MOTOR VEHICLES AND MOTOR VEHICLE ENGINES, Urban Bus Rebuild Requirements".
2. Newkirk Matthews S., "Application of Methods for Determining Total Organic Contribution to Diesel Particulate", ASME 92-ICE016.