HOMOGENEOUS CHARGE CATALYTIC IGNITION OF ETHANOL-WATER/AIR MIXTURES IN A RECIPROCATING ENGINE

Transcription

1 HOMOGENEOUS CHARGE CATALYTIC IGNITION OF ETHANOL-WATER/AIR MIXTURES IN A RECIPROCATING ENGINE Final Report KLK752A Compression Ratio and Catalyst Aging Effects on Aqueous Ethanol N09-04 National Institute for Advanced Transportation Technology University of Idaho Dan Cordon, Dr. Steven Beyerlein April 2009

2 DISCLAIMER The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. This document is disseminated under the sponsorship of the Department of Transportation, University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof.

3 1. Report No. 2. Government Accession No. 4. Title and Subtitle Compression Ratio and Catalyst Aging Effects on Aqueous Ethanol: Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air Mixtures in a Reciprocating Engine 3. Recipient s Catalog No. 5. Report Date April Performing Organization Code KLK752A 7. Author(s) Cordon, Dan; Beyerlein, Dr. Steven 8. Performing Organization Report No. N Performing Organization Name and Address 10. Work Unit No. (TRAIS) National Institute for Advanced Transportation Technology University of Idaho PO Box ; 115 Engineering Physics Building Moscow, ID Sponsoring Agency Name and Address US Department of Transportation Research and Special Programs Administration 400 7th Street SW Washington, DC Supplementary Notes: 11. Contract or Grant No. DTRT07-G Type of Report and Period Covered Final Report: August 2007 December Sponsoring Agency Code USDOT/RSPA/DIR Abstract Lean ethanol-water/air mixtures have potential for reducing NO x and CO emissions in internal combustion engines, with little well-to-wheels CO 2 emissions. Conventional ignition systems have been unsuccessful at igniting such mixtures. An alternative catalytic ignition source is being developed to aid in the combustion of aqueous ethanol. The operating principle is homogeneous charge compression ignition inside a catalytic prechamber, which causes torch ignition and flame propagation in the combustion chamber. Ignition timing can be adjusted by changing the length of the catalytic core element, the length of the pre-chamber, the diameter of the pre-chamber, and the electrical power supplied to the catalytic core element. To study engine operation, a 1.0L 3- cylinder Yanmar diesel engine was converted for ethanol-water use, and compared with an unmodified engine. Comparing the converted Yanmar to the stock engine shows an increase in torque and power, with improvements in CO and NO x emissions. Hydrocarbon emissions from the converted engine increased significantly, but are largely due to piston geometry not well suited for homogeneous charge combustion. No exhaust after treatment was performed on either engine configuration. Applying this technology in an engine with a combustion chamber and piston design suited for homogeneous mixtures has the potential to lower emissions to current standards, with a simple reduction catalytic converter. 17. Key Words Pollutant control, fuel systems, engine testing, renewable fuels 18. Distribution Statement Unrestricted; Document is available to the public through the National Technical Information Service; Springfield, VT. 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages Price Form DOT F (8-72) Reproduction of completed page authorized

4 Table of Contents Introduction... 1 Catalytic Igniters... 2 Engine Conversions... 4 Experimental Apparatus... 5 Engine Performance... 7 Modal Comparison Conclusion References Appendix Figures Figure 1 Exploded view of catalytic igniter Figure 2 Flame pattern exiting pre-chamber nozzle Figure 3 Experimental apparatus for engine testing Figure 4 Full load BMEP for diesel and aquanol Figure 5 Full load power for diesel and aquanol Figure 6 Equivalence ratio for full load curves Figure 7 Performance map for diesel engine Figure 8 Performance map for aquanol engine Figure 9 Mode points for comparing engines Figure 10 Efficiency in KJ/kWh Figure 11 Equivalence ratio at each mode point Figure 12 Brake specific carbon monoxide Figure 13 Brake specific hydrocarbons Figure 14 Brake specific carbon dioxide Figure 15 Brake specific oxides of nitrogen Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air i

5 Tables Table 1 Original Yanmar Engine Specifications [12] Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air ii

6 INTRODUCTION Lean burn piston engines are an avenue for reducing fuel consumption and environmental impact. The difficulty in burning lean air/fuel mixtures spawned the development of the catalytic igniter (1). Most homogeneous charge lean burn engines suffer from reduced power output per displacement and incompatibility with oxidation/reduction catalysts (2). The catalytic igniter was developed to help overcome these issues. Previous engine conversions have shown an increase in net thermal efficiency and power output and have been able to operate under lean conditions with reduced emissions. The University of Idaho has been working with Automotive Resources Inc. for the past ten years to study catalytic igniters in engines fueled by ethanol-water blends. Initially, lean ethanol mixtures were studied, but resulted in high nitrogen oxide (NO x ) emissions. Adding water to the fuel lowered combustion temperatures and resulted in a large reduction of NO x emissions. Mixtures of up to 50 percent ethanol and 50 percent water (by volume) have been used in test engines. Because no noticeable benefits were noticed beyond 30 percent water, a 70/30 blend of ethanol/water (by volume) was used in this study. This mixture is sometimes called aquanol. Because ethanol readily adsorbs water, no special emulsions or processes are required to mix this fuel. Combusting aqueous fuel in a piston engine requires a larger ignition source than necessary for gasoline. High-energy spark ignition systems are capable of initiating combustion, but the high water content in the cylinder tends to quench the flame front. Past attempts at compression ignition of aqueous fuel has been unsuccessful due to difficulties in controlling ignition timing. Modern homogeneous charge compression ignition (HCCI) control systems may open this opportunity in the future. Using a catalyst provides a consistent and controllable ignition source with sufficient energy to sustain combustion of the in-cylinder mixture. The use of water in combustion either mixed with the fuel or injected separately is not new, and has been published in many papers. Cold-starting with greater than 20 percent water has not been found in the literature. Once at operating temperatures, many engines using more than 20 percent water require significant energy for an air pre-heater in order to sustain combustion (5, 6, Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 1

7 7, and 8). Catalytic ignition has been successful with cold starting engines with as much as 50 percent water in the fuel, and the electrical energy used to heat the catalyst is 0-20W per cylinder. CATALYTIC IGNITERS The catalytic igniter is a self-contained ignition system that can be retrofitted to Spark Ignition (SI) and most Compression Ignition (CI) engines. For SI engines, the catalytic igniter is located in the spark plug hole. Conversions for CI engines must be on direct injection engines, and the catalytic igniter is located in place of the injector. An illustration of a typical catalytic igniter is shown in Figure 1. The igniter core is a hollow ceramic rod with a heating element embedded in the bottom end. A coating of noble metal catalyst paste is painted over the heater element. The top end of the tube is sealed with an electrical feed through for the heating element. This assembly is screwed in to a brass pre-chamber. The lower end of this pre-chamber is mounted to the cylinder head where the tip is exposed to the combustion chamber. Holes in the end of the pre-chamber allow fresh mixture to enter and a torch-like ignition source to exit. Figure 1 Exploded view of catalytic igniter. Ignition begins during the compression stroke, as soon as fresh mixture comes in contact with the hot catalytic surface. Reduced activation energy associated with heterogeneous catalysts means that this occurs far below the normal gas-phase ignition temperature (9). Combustion products and intermediate species accumulate in the top of the pre-chamber above the heated catalyst. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 2

8 After sufficient pressure and temperature from energy release and compression occur, multi-point homogeneous ignition inside the pre-chamber results (9, 10). The combusting mixture is released out the bottom of the pre-chamber through nozzles that direct the flame around the main combustion chamber. This flame becomes the source of ignition for the main combustion chamber, which burns in a typical flame propagation method. It is believed that the high energy and large volume of this main chamber ignition source are largely responsible for stable operation on lean ethanol-water mixtures. In-cylinder imaging has not been captured. To approximate the flame pattern exiting the catalytic igniter, a propane-air mixture was pumped through the top of the pre-chamber and past the hot catalyst surface. The resulting flame pattern is shown in Figure 2. It is believed that this is similar to what occurs in operation, but this has not yet been confirmed. Figure 2 Flame pattern exiting pre-chamber nozzle. Controlling ignition timing is a critical problem with any homogeneous charge compression ignition engine. Both Yanmar conversion engines operate without a throttle plate, so only the amount of fuel injected determines the engine power output. Because of this, the air/fuel ratio varies greatly over the operating range of the engine. The original diesel engine is direct injection, and fuel burns in a diffusion method. The aquanol conversion is a premixed air/fuel mixture fuel is injected in the intake manifold and operates via flame propagation. A mathematical model was created to explore parameters that effect ignition timing with the catalytic igniter (11). In the case of an unthrottled engine, adjustment of ignition timing Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 3

9 characteristics was best accomplished by changing the length of the ceramic core, and therefore the position of the catalyst in the pre-chamber. Shortening the rod would move the heated catalyst section higher in the pre-chamber, causing there to be a greater delay in the fresh mixture coming in contact with the catalyst. This resulted in a retardation of the ignition timing. Conversely, longer rods resulted in advancing ignition timing. The relationship between igniter core length and ignition is not completely linear. However, in the ranges used, a core length change of 1.0mm resulted in a ~5 change in ignition timing. Dynamic change of the catalyst location was not possible. The final decision of igniter core length was done by observing in-cylinder pressure traces and changing out the cores for different lengths. Testing started with a short length so the ignition timing would be retarded and relatively safe. The engine was run through a full load RPM sweep, and if there were no regions where ignition was too advanced, a longer core would be installed and the engine tested again. This was repeated until detonation was observed. The longest (most advanced timing) that did not experience detonation was selected for this study. Ignition timing was not optimal for all operating points, and use of a programmable heating circuit has potential to improve engine performance and emissions. ENGINE CONVERSIONS Two Yanmar diesel engines were used in this work. Specifications are given in Table 1. Both were recently rebuilt and brake-in was performed as per manufacturer recommendations. One engine was left in original configuration to be used as a baseline comparison for this work. All previous aquanol conversions were done on SI engines. In these conversions, the original throttle was maintained, and engines were tuned to maintain a near-constant air/fuel ratio over the entire operating range. In an attempt to study high compression ratios and lean combustion, the Yanmar conversion was not fitted with a throttle. Engine output is controlled only by the amount of fuel injected in to the intake manifold. Because the in-cylinder volume remains relatively constant, changes in fuel injection quantity result in a wide range of homogeneous air/fuel equivalence ratios. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 4

10 Table 1 Original Yanmar Engine Specifications [12] Model 3TN75E Cylinders 3 Bore 75 mm Stroke 75 mm Displacement L Compression 17.61:1 1-hr Rated Power 16.0 kw 1-hr Rated Speed 3000 Conversion of the Yanmar engine was relatively simple. A multi-port fuel injection system was fitted to the original intake manifold, with automotive-style fuel injectors. The diesel pump and injectors were removed, and catalytic igniters were placed in the direct fuel injector ports. Both engines were equipped with alternators, and any electrical load used by the engine (air pre-heaters and catalytic igniters) were powered by these alternators. Prior to each engine test session, the engines were allowed to run for several minutes until they reached operating temperatures and recharged the starting battery. The aquanol conversion also had the cylinder head machined for a combustion pressure sensor to be fitted flush with the cylinder head. This was not required for the conversion, but was used for adjusting ignition timing and measuring combustion trends in the engine. In previous conversions, the pre-chamber volume was between 5-7 percent of the original combustion chamber volume. For the aquanol conversion, each pre-chamber volume was 1.4 cm percent of the original TDC volume. This resulted in lowering the compression ratio to ~16.5:1 (13). EXPERIMENTAL APPARATUS Figure 3 shows the experimental apparatus used for data collection. Because the combustion pressure sensors were flush mounted to the combustion chamber, full Envar bodies were required. These were obtained from PCB, model number 112M275. The capacitive signal from the pressure sensors was sent to a charge converter (PCB model 422M96), then to either a 100 MHz oscilloscope or a Redline DSP combustion analyzer depending on the test. A 1000 pulse/revolution encoder was fitted to the front of the crankshaft, and a second channel with a 1 pulse/revolution signal was used to reference TDC of cylinder 1. A Land-and-Sea water brake dynamometer (9 size) with an electronic controlled water valve was used to provide a steady- Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 5

11 state load for engine testing. Calibration of the dynamometer was performed before each run, and confirmed after each run to detect signs of torque drift. Fuel flow was recorded by a Max Machinery model 710 fuel conditioning cart with temperature corrected calibrations for both diesel and 70/30 aquanol fuel. Figure 3 Experimental apparatus for engine testing. Not shown on Figure 3 are the bungs for measuring exhaust gas temperature (EGT) and emissions. The EGT bung was located in the exhaust manifold collector, mm downstream of the exhaust valve depending on the cylinder. Because of this, EGT readings are much lower than observed with closer temperature probes. In this study, the EGTs are only used to compare the engines to one another. The emissions collection bung was located 24 upstream of the exhaust exit to minimize any effects from ambient air getting in to the exhaust system between exhaust pulses. Emissions were detected by an Emissions System Inc. 5-gas analyzer, model This model uses a Peltier cooler to remove water from the incoming exhaust sample line. A NDIR sensor is used to measure CO, CO 2, and HC (hexane equivalent) concentrations. Electrochemical sensors are used to measure NO x and O 2 concentrations. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 6

12 BMEP [kpa] ENGINE PERFORMANCE BMEP and SAE corrected shaft power are shown for both the stock diesel and aquanol conversion in Figures 4 and 5. The Yanmar spec for peak engine speed is 3000 RPM. In original configuration, the slow burn rate of fuel keeps the engine from running beyond this speed. However, the homogeneous mixture of the converted engine burns quite rapidly in comparison. The converted engine was capable of much higher engine speeds, but because this was outside the max speed rating, the aquanol engine was tuned to cut fuel for any speed over 3100 RPM. If the rotating assembly was safe to run beyond this speed, power output from the aquanol engine may have been higher still Aquanol Diesel Engine Speed [RPM] Figure 4 Full load Brake Mean Effective Pressure (BMEP) for diesel and aquanol. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 7

13 Power [kw] Aquanol Diesel Engine Speed [RPM] Figure 5 Full load power for diesel and aquanol. The aquanol engine had higher full load Brake Mean Effective Pressure (BMEP) and power curves than the diesel engine. The equivalence ratio for the full load data is shown in Figure 6. It was calculated using an equation recommended by the manufacturer of the 5-gas analyzer. Several runs were made with the aquanol engine operating under higher equivalence ratios than displayed in these figures. Under richer conditions the engine produced even higher torque and power levels, but the emissions of CO increased by as much as 200 percent. Thus the engine was de-tuned to produce reasonable emissions at the cost of peak performance. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 8

14 Equivalence Ratio Aquanol Diesel Engine Speed [RPM] Figure 6 Equivalence ratio for full load curves. The lower heating value for a 70/30 aquanol blend is calculated at 17.4 MJ/kg 42 percent lower than diesel fuel at 41.4 MJ/kg. Because of this, comparing Brake Specific Fuel Consumption (BSFC) numbers directly would not tell the full story. Instead, net thermal efficiency was used to compare the two engines. Based on evenly captured data over the full range of operating conditions, performance maps with lines of constant net thermal efficiency were created. Figure 7 shows the performance map for the diesel engine, and Figure 8 shows the aquanol engine. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 9

15 Torque N*m Torque N*m Diesel Thermal Efficiency Speed RPM Figure 7 Performance map for diesel engine. Aquanol Thermal Efficiency Speed RPM Figure 8 Performance map for aquanol engine. The diesel engine has a wide range of operation where there is high efficiency. From RPM and percent load, the engine is over 30 percent efficient. This covers nearly ¾ of the operating range of the engine. The aquanol conversion is quite efficient at high loads (above 80 Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 10

16 BMEP [kpa] percent of peak load) but efficiency continually falls with reduced load. At lower loads there is a very lean homogeneous mixture in the cylinder. Based on emissions collected at these points, combustion efficiency is extremely poor. When operating below 20 N*m and under 2500 RPM, the aquanol engine is at an equivalence ratio slightly below 0.3. However, at high load across a wide RPM range the aquanol conversion has a comparable thermal efficiency to the diesel engine. MODAL COMPARISON Contour plots of Brake Specific Emissions were cluttered, and some of the emissions are on different orders of magnitude between the two engines. Instead, nine mode points based on BMEP and engine speed were selected for comparison as shown in Figure 9. The mode points are labeled 1-9. Mode points 1-6 correlate to the diesel engine at peak load. Aquanol data was selected that most closely matched to the diesel engine mode points. Load point 7 represents low load and medium speed. Load point 8 represents low load and high speed. Load point 9 is at a medium load and speed. Brake specific emissions were calculated using the EPA 40 CFR Part 91 Section 419c. See Appendix A for a sample calculation Diesel Mode Points Aquanol Mode Points Engine Speed [RPM] Figure 9 Mode points for comparing engines. Efficiency maps for the whole operating range were shown in Figures 7 and 8. Figure 10 shows efficiency at each mode point given in units of kj/kwh. This shows the rate of fuel energy used (mass flow * heating value) divided by the power output of the engine. Lower numbers represent Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 11

17 Efficiency [kj/kw*hr] higher efficiency than larger numbers. Shown in Figure 11 is the equivalence ratio for each mode point. The diesel engine operates leaner than the aquanol engine at every mode point. Of interest is how the two engines compare when operating under the same speed and equivalence ratio. Mode point three of the diesel data and point seven of the aquanol data provide this comparison. The equivalence ratio of the aquanol engine at point seven is similar to the equivalence ratio of diesel at point three, and they are both at the same engine speed (2250 RPM). Under these conditions the aquanol engine makes less power than the diesel engine and is also much less efficient. The combustion efficiency of the diesel engine is quite good at this point, but the lean homogeneous mixture does not burn very completely. This is also evident in the hydrocarbon emissions Diesel Aquanol Mode Points Figure 10 Efficiency in KJ/kWh. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 12

18 BSCO [gm/kw-hr] Phi Diesel Aquanol Mode Points Figure 11 Equivalence ratio at each mode point. Carbon monoxide emissions are given in Figure 12. At the higher load points and equivalence ratios (points 1-6) the aquanol engine produced fewer CO emissions compared to the diesel engine. However, at the highly lean conditions of low load (points 7 and 8), the aquanol engine produced greater amounts of CO Diesel Aquanol Mode Point Figure 12 Brake specific carbon monoxide. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 13

19 BSHC [gm/kw-hr] Brake specific hydrocarbon emissions are shown in Figure 13. At all operating conditions, the aquanol conversion was off the charts compared to the diesel engine. The data points for the diesel do not even register on the figure, but peaked out at 1.04 gm/kw-hr at mode point 7. Mode points 1-6 were all under 0.6 gm/kw-hr. A diffusion flame in a lean environment should have low HC emissions. The aquanol conversion had its lowest BSHC emissions at full load where the mixture was near stoichiometric. As the mixture got leaner, less and less of the mixture was completely burned. The two lowest load modes (points 7 and 8) had very poor BSHC emissions. A simple reduction catalytic converter may help clean this up, but because of the significant amount of chemical energy to be released a thermal reactor may be a better choice for this application Diesel Aquanol Mode Point Figure 13 Brake specific hydrocarbons. Brake specific CO 2 was also calculated for both engines and shown in Figure 14. A well-towheels analysis would give the bio mass fuel a clear advantage as the net CO 2 release is minimal. At moderate loads, the tailpipe BSCO 2 emissions are similar between the two engines. At low loads, the aquanol engine releases nearly 300 percent more CO 2 out the tailpipe than the diesel. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 14

20 BSNOx [gm/kw-hr] BSCO2 [gm/kw-hr] Diesel Aquanol Mode Point Figure 14 Brake specific carbon dioxide. Brake specific NO x emissions are shown in Figure 15. As expected, NO x from the diesel engine is much greater than the aquanol engine. The water in the ethanol fuel was used as a means of reducing EGTs and therefore NO x emissions. It was expected that the EGTs of the aquanol engine would be lower than the diesel. This was not the case as the diesel EGTs ranged between C, while the aquanol EGTs ranged between C. The flame temperature of aqueous ethanol is much lower than gasoline or diesel, and homogeneous charge combustion typically have reduction in NO x emissions Diesel Aquanol Mode Point Figure 15 Brake specific oxides of nitrogen. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 15

21 CONCLUSION The use of catalytic igniters allowed engine operation of homogeneous mixtures under very lean conditions. The larger ignition source also made it possible to ignite an aqueous ethanol mixture that was not possible with the original spark ignition system. The initial goal of aqueous ethanol research was lean combustion without high NO x emissions. This has been realized in this work. Slight increases in peak thermal efficiency were observed with the converted engine, and a significant increase in engine torque and power output was also achieved. Low load operation of the aquanol engine was possible at the lean limits at equivalence ratios of 0.3, but efficiency and emissions suffered greatly at low loads. Hydrocarbon cleanup is a logical next step for this application so that emissions could be dropped down to gasoline engine equivalents. Future work should be conducted with high compression ratios, and with a combustion chamber geometry better suited for homogeneous charge applications. This may help reduce some of the hydrocarbon emissions prior to exhaust after-treatment. A high-speed engine should also be used to find the resonance time requirements for aqueous ethanol. Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 16

22 REFERENCES 1. Cherry, M., Catalytic-Compression Timed Ignition, US Patent , December 18, Cherry, M., Morrisset, R., and Beck, N., Extending Lean Limit with Mass-Timed Compression Ignition Using a Plasma Torch, Society of Automotive Engineers Paper #921556, Gottschalk, Mark A., Catalytic Ignition Replaces Spark Plugs, Design News, May 22, Dale, J. and Oppenheim, A., A Rationale for Advances in Technology of IC Engines, Society of Automotive Engineers Paper #820047, Browning, L.H., and Pefley, R.K., Kinetic Wall Quenching of Methanol Flames with Applications to Spark Ignition Engines, Society of Automotive Engineers Paper , Pischinger, F., and Kramer, K., The Influence of Engine Parameters on the Aldehyde Emissions of a Methanol Operated Four-Stroke Otto Cycle Engine, Third International Symposium on Alcohol Fuel Technology, Asilomar, CA, May 28-31, Lee, W., and Geffers, W., Engine Performance and Exhaust Emissions Characteristics of Spark Ignition Engines Burning Methanol and Methanol Mixtures, A.I.Ch.E. Symposium Series #165, Vol. 73, Christensen, M., and Johnasson, B., Homogeneous Charge Compression Ignition with Water Injection, Society of Automotive Engineers Paper # , Cho, P. and Law, C., Catalytic Ignition of Fuel/Oxygen/Nitrogen Mixtures over Platinum, Combustion and Flame, Vol. 66, pp , Pfefferle, L., Catalysis in Combustion, Catalysis Reviews, Science and Engineering Vol. 29, pp , Cordon, D., Clarke, E., Catalytic Igniter to Support Combustion of Ethanol- Water/Air Mixtures in Internal Combustion Engines, Society of Automotive Engineers Paper # , Yanmar Diesel Engine Co, Service Manual for 3TN75E Engine, Clarke, E., Characterization of Aqueous Ethanol Homogeneous Charge Catalytic Compression Ignition, Master s Thesis, University of Idaho, Homogeneous Charge Catalytic Ignition of Ethanol-Water/Air 17

23 APPENDIX EXAMPLE CALCULATION USING FUEL FLOW TO FIND MASS EMISSIONS (Inputs for fuel composition are in blue. Inputs for each mode point are in yellow) Units and Constants rev 2 rad ppm Methane 1 ppm NOx 1 ppm C1 1 Molecular Weights M CO gm mol M CO gm mol M NO gm mol Humidity Correction for NOx H specific gm kg K H H specific K H 0.74 Fuel Composition gm HC ratio 1.75 MW fuel HC ratio mol Measured Engine Data MW fuel gm mol RPM measured 1750 rev min Torque measured ft lbf G fuel lb hr Measured Emissions Data CO2 dry 3.375% CO dry.705% O2 dry % NOx dry 371.5ppm NOx HC dry ppm Methane <--- corrected for Hexane readout Calculated Data Power measured Torque measured RPM measured Power measured kW Percent H2 present in exhaust (calculated) 0.5 HC ratio CO dry CO dry CO2 dry H2 dry CO dry 3 CO2 dry H2 dry 0.232% Correction factor to correct measurements on a dry basis to a wet basis K factor CO dry CO2 dry HC ratio 0.01 H2 dry 100 K factor 0.968

24 HC wet HC dry K factor HC wet ppm C1 CO wet CO dry K factor CO wet 0.682% CO2 wet CO2 dry K factor CO2 wet 3.266% NOx wet NOx dry K factor NOx wet ppm NOx O2 wet O2 dry K factor O2 wet % TC CO wet CO2 wet HC wet TC % Carbon Calculated Mass Emissions G fuel HC wet gm HC TC 10 6 HC hr 100 CO M CO MW fuel G fuel TC CO wet CO gm hr 100 CO2 M CO2 MW fuel G fuel TC CO2 wet CO gm hr 100 M NO2 G fuel NOx wet gm NOx K MW fuel TC H 10 6 NOx hr 100 Comparing carbon flow in and carbon flow out m dot_carbon_hc HC ( ) gm mol gm mol m dot_carbon_hc gm hr m dot_carbon_co CO gm M CO mol m dot_carbon_co gm hr m dot_carbon_co2 CO gm M CO2 mol m dot_carbon_co gm hr m dot_carbon_exh m dot_carbon_hc m dot_carbon_co m dot_carbon_co2 m dot_carbon_exh gm hr m dot_carbon_fuel G fuel MW fuel gm mol m dot_carbon_fuel gm hr